map[EquivalenceAnalysis:The reproducer successfully triggered the circular locking dependency. Although the exact function where `&tty->termios_rwsem` is acquired differs slightly (`n_tty_flush_buffer` instead of `n_tty_receive_buf_common`), the underlying deadlock cycle is identical. Both crashes involve a task holding `&buf->lock` and attempting to acquire `&tty->termios_rwsem`, conflicting with the established dependency chain `&tty->termios_rwsem` -> `console_lock` -> `&buf->lock`. This confirms the reproducer triggers the exact same root cause. OtherCrashReports:<nil> ReproC:#define _GNU_SOURCE
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <stdlib.h>
#include <linux/kd.h>
#include <linux/input.h>
#include <linux/uinput.h>
#include <linux/vt.h>
#include <string.h>
#include <stdio.h>
#include <sys/wait.h>
#include <errno.h>

#define TIOCSPTLCK	_IOW('T', 0x40, int)
#define TIOCGPTN	_IOR('T', 0x30, unsigned int)

void trigger_tcsets() {
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS1", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS2", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS3", O_RDWR | O_NOCTTY);
    if (fd_serial >= 0) {
        struct termios term;
        if (ioctl(fd_serial, TCGETS, &term) == 0) {
            if (ioctl(fd_serial, TCSETS, &term) < 0) {
                printf("[-] TCSETS failed: %s\n", strerror(errno));
            } else {
                printf("[+] trigger_tcsets successful.\n");
            }
        } else {
            printf("[-] TCGETS failed: %s\n", strerror(errno));
        }
        close(fd_serial);
    } else {
        printf("[-] trigger_tcsets failed to open serial port: %s\n", strerror(errno));
    }
}

void trigger_sak() {
    int vt_num = 5;
    int fd_tty = open("/dev/tty5", O_RDWR | O_NOCTTY);
    if (fd_tty < 0) {
        vt_num = 0;
        fd_tty = open("/dev/tty0", O_RDWR | O_NOCTTY);
    }
    if (fd_tty < 0) {
        printf("[-] trigger_sak failed to open tty: %s\n", strerror(errno));
        exit(1);
    }
    
    if (vt_num != 0) {
        if (ioctl(fd_tty, VT_ACTIVATE, vt_num) < 0) {
            printf("[-] VT_ACTIVATE failed: %s\n", strerror(errno));
        }
        if (ioctl(fd_tty, VT_WAITACTIVE, vt_num) < 0) {
            printf("[-] VT_WAITACTIVE failed: %s\n", strerror(errno));
        }
        printf("[+] Activated /dev/tty%d.\n", vt_num);
    }

    // Map KEY_A to K_SAK across all keymaps to ensure it triggers
    for (int i = 0; i < 256; i++) {
        struct kbentry ke;
        ke.kb_table = i;
        ke.kb_index = 30; // KEY_A
        ke.kb_value = 0x020F; // K_SAK
        if (ioctl(fd_tty, KDSKBENT, &ke) < 0) {
            // Some keymaps might not exist, ignore errors
        }
    }
    printf("[+] trigger_sak mapped KEY_A to K_SAK.\n");

    int ufd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
    if (ufd >= 0) {
        if (ioctl(ufd, UI_SET_EVBIT, EV_KEY) < 0) {
            printf("[-] UI_SET_EVBIT failed: %s\n", strerror(errno));
        }
        if (ioctl(ufd, UI_SET_KEYBIT, KEY_A) < 0) {
            printf("[-] UI_SET_KEYBIT failed: %s\n", strerror(errno));
        }

        struct uinput_setup usetup;
        memset(&usetup, 0, sizeof(usetup));
        usetup.id.bustype = BUS_USB;
        usetup.id.vendor = 0x1234;
        usetup.id.product = 0x5678;
        strcpy(usetup.name, "Virtual Keyboard");
        if (ioctl(ufd, UI_DEV_SETUP, &usetup) < 0) {
            printf("[-] UI_DEV_SETUP failed: %s, falling back to uinput_user_dev\n", strerror(errno));
            struct uinput_user_dev uud;
            memset(&uud, 0, sizeof(uud));
            uud.id.bustype = BUS_USB;
            uud.id.vendor = 0x1234;
            uud.id.product = 0x5678;
            strcpy(uud.name, "Virtual Keyboard");
            if (write(ufd, &uud, sizeof(uud)) < 0) {
                printf("[-] write uinput_user_dev failed: %s\n", strerror(errno));
            }
        }
        if (ioctl(ufd, UI_DEV_CREATE) < 0) {
            printf("[-] UI_DEV_CREATE failed: %s\n", strerror(errno));
        }

        usleep(100000); // Wait for input device to be registered

        struct input_event ie;
        
        // Press KEY_A
        memset(&ie, 0, sizeof(ie));
        ie.type = EV_KEY; ie.code = KEY_A; ie.value = 1;
        if (write(ufd, &ie, sizeof(ie)) < 0) {
            printf("[-] write EV_KEY failed: %s\n", strerror(errno));
        }

        memset(&ie, 0, sizeof(ie));
        ie.type = EV_SYN; ie.code = SYN_REPORT; ie.value = 0;
        if (write(ufd, &ie, sizeof(ie)) < 0) {
            printf("[-] write EV_SYN failed: %s\n", strerror(errno));
        }

        printf("[+] trigger_sak injected KEY_A.\n");
        
        // Wait for vc_SAK workqueue to execute and kill us
        sleep(2); 
        
        // If we survive:
        ioctl(ufd, UI_DEV_DESTROY);
        close(ufd);
    } else {
        printf("[-] trigger_sak failed to open /dev/uinput: %s\n", strerror(errno));
        exit(1);
    }
    close(fd_tty);
}

void trigger_pty() {
    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx >= 0) {
        int unlock = 0;
        if (ioctl(ptmx, TIOCSPTLCK, &unlock) < 0) {
            printf("[-] TIOCSPTLCK failed: %s\n", strerror(errno));
        }
        unsigned int ptn;
        if (ioctl(ptmx, TIOCGPTN, &ptn) == 0) {
            char pts_name[32];
            snprintf(pts_name, sizeof(pts_name), "/dev/pts/%u", ptn);
            int pts = open(pts_name, O_RDWR | O_NOCTTY);
            if (pts >= 0) {
                if (write(ptmx, "a", 1) < 0) {
                    printf("[-] trigger_pty failed to write to ptmx: %s\n", strerror(errno));
                } else {
                    printf("[+] trigger_pty wrote to ptmx.\n");
                }
                usleep(100000); // Wait for flush_to_ldisc workqueue to execute
                close(pts);
            } else {
                printf("[-] trigger_pty failed to open %s: %s\n", pts_name, strerror(errno));
            }
        } else {
            printf("[-] TIOCGPTN failed: %s\n", strerror(errno));
        }
        close(ptmx);
    } else {
        printf("[-] trigger_pty failed to open /dev/ptmx: %s\n", strerror(errno));
        exit(1);
    }
}

int main(void) {
    printf("[+] Starting reproducer...\n");

    // 1. Trigger &tty->termios_rwsem -> &port->mutex
    trigger_tcsets();

    // 2. Trigger console_lock -> &buf->lock
    // Do this in a child process because __do_SAK sends SIGKILL to processes
    // associated with the active console.
    pid_t pid = fork();
    if (pid < 0) {
        printf("[-] fork failed: %s\n", strerror(errno));
        exit(1);
    }
    if (pid == 0) {
        trigger_sak();
        exit(0);
    }
    int status;
    waitpid(pid, &status, 0);
    if (WIFSIGNALED(status)) {
        printf("[+] Child process for SAK killed by signal %d (expected if SAK triggered).\n", WTERMSIG(status));
    } else {
        printf("[+] Child process for SAK exited normally.\n");
    }

    // 3. Trigger &buf->lock -> &tty->termios_rwsem
    // This completes the circular dependency and triggers the lockdep splat.
    trigger_pty();

    printf("[+] Reproducer finished.\n");
    return 0;
} Reproduced:true ReproducedBugTitle:possible deadlock in n_tty_flush_buffer ReproducedCrashReport:======================================================
WARNING: possible circular locking dependency detected
syzkaller #1 Not tainted
------------------------------------------------------
kworker/0:5/5693 is trying to acquire lock:
ffff8881fafd02c8 (&tty->termios_rwsem){++++}-{4:4}, at: class_rwsem_write_constructor include/linux/rwsem.h:270 [inline]
ffff8881fafd02c8 (&tty->termios_rwsem){++++}-{4:4}, at: n_tty_flush_buffer+0x30/0x230 drivers/tty/n_tty.c:349

but task is already holding lock:
ffff8881961b50b8 (&buf->lock){+.+.}-{4:4}, at: tty_buffer_flush+0x74/0x2b0 drivers/tty/tty_buffer.c:236

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&buf->lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
       tty_buffer_flush+0x74/0x2b0 drivers/tty/tty_buffer.c:236
       tty_ldisc_flush+0x6b/0xc0 drivers/tty/tty_ldisc.c:388
       __do_SAK+0x25e/0x680 drivers/tty/tty_io.c:3025
       vc_SAK+0x78/0x220 drivers/tty/vt/vt_ioctl.c:994
       process_one_work kernel/workqueue.c:3322 [inline]
       process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
       worker_thread+0x92d/0xe10 kernel/workqueue.c:3486
       kthread+0x388/0x470 kernel/kthread.c:436
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #2 (console_lock){+.+.}-{0:0}:
       console_lock+0x76/0x90 kernel/printk/printk.c:2896
       uart_configure_port drivers/tty/serial/serial_core.c:2530 [inline]
       serial_core_add_one_port drivers/tty/serial/serial_core.c:3101 [inline]
       serial_core_register_port+0xc47/0x2840 drivers/tty/serial/serial_core.c:3322
       serial8250_register_8250_port+0x16b4/0x2090 drivers/tty/serial/8250/8250_core.c:828
       serial_pnp_probe+0x56a/0x7f0 drivers/tty/serial/8250/8250_pnp.c:480
       pnp_device_probe+0x30b/0x4c0 drivers/pnp/driver.c:111
       call_driver_probe drivers/base/dd.c:-1 [inline]
       really_probe+0x254/0xae0 drivers/base/dd.c:706
       __driver_probe_device+0x1e8/0x360 drivers/base/dd.c:868
       driver_probe_device+0x4f/0x240 drivers/base/dd.c:898
       __driver_attach+0x339/0x600 drivers/base/dd.c:1292
       bus_for_each_dev+0x23b/0x2c0 drivers/base/bus.c:383
       bus_add_driver+0x345/0x670 drivers/base/bus.c:763
       driver_register+0x23a/0x320 drivers/base/driver.c:174
       serial8250_init+0x8f/0x160 drivers/tty/serial/8250/8250_platform.c:317
       do_one_initcall+0x250/0x870 init/main.c:1347
       do_initcall_level+0x10a/0x1a0 init/main.c:1409
       do_initcalls+0x59/0xa0 init/main.c:1425
       kernel_init_freeable+0x29d/0x3e0 init/main.c:1658
       kernel_init+0x1d/0x1d0 init/main.c:1548
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #1 (&port->mutex){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
       class_mutex_constructor include/linux/mutex.h:253 [inline]
       uart_set_termios+0x81/0x710 drivers/tty/serial/serial_core.c:1645
       tty_set_termios+0xcaf/0x1800 drivers/tty/tty_ioctl.c:341
       set_termios+0x53d/0x6c0 drivers/tty/tty_ioctl.c:516
       tty_mode_ioctl+0x49c/0x7c0 drivers/tty/tty_ioctl.c:-1
       tty_ioctl+0x9bd/0xdd0 drivers/tty/tty_io.c:2801
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&tty->termios_rwsem){++++}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x1520/0x2cf0 kernel/locking/lockdep.c:5237
       lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
       down_write+0x96/0x200 kernel/locking/rwsem.c:1631
       class_rwsem_write_constructor include/linux/rwsem.h:270 [inline]
       n_tty_flush_buffer+0x30/0x230 drivers/tty/n_tty.c:349
       tty_buffer_flush+0x1ec/0x2b0 drivers/tty/tty_buffer.c:248
       tty_ldisc_flush+0x6b/0xc0 drivers/tty/tty_ldisc.c:388
       __do_SAK+0x25e/0x680 drivers/tty/tty_io.c:3025
       vc_SAK+0x78/0x220 drivers/tty/vt/vt_ioctl.c:994
       process_one_work kernel/workqueue.c:3322 [inline]
       process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
       worker_thread+0x92d/0xe10 kernel/workqueue.c:3486
       kthread+0x388/0x470 kernel/kthread.c:436
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

other info that might help us debug this:

Chain exists of:
  &tty->termios_rwsem --> console_lock --> &buf->lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&buf->lock);
                               lock(console_lock);
                               lock(&buf->lock);
  lock(&tty->termios_rwsem);

 *** DEADLOCK ***

5 locks held by kworker/0:5/5693:
 #0: ffff88810006b140 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3297 [inline]
 #0: ffff88810006b140 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3405
 #1: ffffc90003ea7c40 ((work_completion)(&vc_cons[currcons].SAK_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3297 [inline]
 #1: ffffc90003ea7c40 ((work_completion)(&vc_cons[currcons].SAK_work)){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3405
 #2: ffffffff8eb55920 (console_lock){+.+.}-{0:0}, at: class_console_lock_constructor include/linux/console.h:734 [inline]
 #2: ffffffff8eb55920 (console_lock){+.+.}-{0:0}, at: vc_SAK+0x28/0x220 drivers/tty/vt/vt_ioctl.c:985
 #3: ffff8881fafd00a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref drivers/tty/tty_ldisc.c:263 [inline]
 #3: ffff8881fafd00a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_flush+0x20/0xc0 drivers/tty/tty_ldisc.c:386
 #4: ffff8881961b50b8 (&buf->lock){+.+.}-{4:4}, at: tty_buffer_flush+0x74/0x2b0 drivers/tty/tty_buffer.c:236

stack backtrace:
CPU: 0 UID: 0 PID: 5693 Comm: kworker/0:5 Not tainted syzkaller #1 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: events vc_SAK
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043
 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3165 [inline]
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x1520/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
 down_write+0x96/0x200 kernel/locking/rwsem.c:1631
 class_rwsem_write_constructor include/linux/rwsem.h:270 [inline]
 n_tty_flush_buffer+0x30/0x230 drivers/tty/n_tty.c:349
 tty_buffer_flush+0x1ec/0x2b0 drivers/tty/tty_buffer.c:248
 tty_ldisc_flush+0x6b/0xc0 drivers/tty/tty_ldisc.c:388
 __do_SAK+0x25e/0x680 drivers/tty/tty_io.c:3025
 vc_SAK+0x78/0x220 drivers/tty/vt/vt_ioctl.c:994
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0x92d/0xe10 kernel/workqueue.c:3486
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
tty tty5: SAK: killed process 5856 (syz-executor241): by fd#3
]

map[KernelSrc:/app/workdir/cache/src/0bd482cc9fd6a5c3cdf3e7f636a3906397462859]

map[KernelObj:/app/workdir/cache/build/288cc213bc32c5d0798e64399515a2514846c767]

map[Index:codesearch-index]

best-expensive

You are a security researcher with deep Linux kernel background.
Your goal is to analyze a Linux kernel bug description and propose a strategy to reproduce it
with a minimal, standalone C program for the strictly defensive purpose of verifying a bugfix.

=== TOOL SELECTION GUIDELINES ===
- When looking up C function or struct definitions, prefer codesearch-definition-source
  and codesearch-struct-layout first.
- Fall back to read-file or grepper only if symbol lookup fails or when inspecting macros,
  headers, or non-C files.

=== CRITICAL PROHIBITIONS ===
- Do NOT propose an exploit. Focus solely on minimal technical reproduction of the bug state.
- Do NOT write long explanations. Keep your analysis and strategy proposal concise.
- Do NOT assume that the target bug has already been fixed just because a git commit title
  or description mentions a similar bug or fix. Commit messages often reference related issues
  or partial fixes. Proceed with proposing a reproduction strategy regardless of historical fix commits.
Prefer calling several tools at the same time to save round-trips.

Bug Description: possible deadlock in n_tty_receive_buf_common

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
kworker/u33:3/62 is trying to acquire lock:
ffff88804b3fe2c8 (&tty->termios_rwsem){++++}-{4:4}, at: class_rwsem_read_constructor include/linux/rwsem.h:259 [inline]
ffff88804b3fe2c8 (&tty->termios_rwsem){++++}-{4:4}, at: n_tty_receive_buf_common+0x85/0x1930 drivers/tty/n_tty.c:1678

but task is already holding lock:
ffff88801404a8b8 (&buf->lock){+.+.}-{4:4}, at: flush_to_ldisc+0x34/0x730 drivers/tty/tty_buffer.c:474

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&buf->lock){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       tty_buffer_flush+0x72/0x310 drivers/tty/tty_buffer.c:236
       tty_ldisc_flush+0xd2/0xf0 drivers/tty/tty_ldisc.c:388
       __do_SAK+0x368/0x480 drivers/tty/tty_io.c:3025
       vc_SAK+0x7f/0x320 drivers/tty/vt/vt_ioctl.c:994
       process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
       process_scheduled_works kernel/workqueue.c:3405 [inline]
       worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
       kthread+0x370/0x450 kernel/kthread.c:436
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #2 (console_lock){+.+.}-{0:0}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       console_lock+0x7a/0xa0 kernel/printk/printk.c:2896
       uart_configure_port drivers/tty/serial/serial_core.c:2530 [inline]
       serial_core_add_one_port drivers/tty/serial/serial_core.c:3101 [inline]
       serial_core_register_port+0xe65/0x16f0 drivers/tty/serial/serial_core.c:3322
       serial8250_register_8250_port+0x15af/0x2330 drivers/tty/serial/8250/8250_core.c:828
       serial_pnp_probe+0x436/0x930 drivers/tty/serial/8250/8250_pnp.c:480
       pnp_device_probe+0x2b3/0x4a0 drivers/pnp/driver.c:111
       call_driver_probe drivers/base/dd.c:628 [inline]
       really_probe+0x241/0xa60 drivers/base/dd.c:706
       __driver_probe_device+0x20e/0x450 drivers/base/dd.c:868
       driver_probe_device+0x4a/0x140 drivers/base/dd.c:898
       __driver_attach+0x21f/0x5b0 drivers/base/dd.c:1292
       bus_for_each_dev+0x13e/0x1d0 drivers/base/bus.c:383
       bus_add_driver+0x305/0x5b0 drivers/base/bus.c:763
       driver_register+0x1e2/0x360 drivers/base/driver.c:174
       serial8250_init+0xcc/0x1c0 drivers/tty/serial/8250/8250_platform.c:317
       do_one_initcall+0x11d/0x700 init/main.c:1347
       do_initcall_level init/main.c:1409 [inline]
       do_initcalls init/main.c:1425 [inline]
       do_basic_setup init/main.c:1445 [inline]
       kernel_init_freeable+0x6ea/0x7b0 init/main.c:1658
       kernel_init+0x1f/0x1e0 init/main.c:1548
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #1 (&port->mutex){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       class_mutex_constructor include/linux/mutex.h:253 [inline]
       uart_set_termios+0x8e/0x690 drivers/tty/serial/serial_core.c:1645
       tty_set_termios+0x64d/0x980 drivers/tty/tty_ioctl.c:341
       set_termios+0x5c8/0x880 drivers/tty/tty_ioctl.c:516
       tty_mode_ioctl+0x17e/0xd40 drivers/tty/tty_ioctl.c:803
       n_tty_ioctl_helper+0x47/0x2b0 drivers/tty/tty_ioctl.c:982
       n_tty_ioctl+0x53/0x340 drivers/tty/n_tty.c:2496
       tty_ioctl+0x11b4/0x1640 drivers/tty/tty_io.c:2801
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl fs/ioctl.c:583 [inline]
       __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x115/0x840 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&tty->termios_rwsem){++++}-{4:4}:
       check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       down_read+0x99/0x4c0 kernel/locking/rwsem.c:1574
       class_rwsem_read_constructor include/linux/rwsem.h:259 [inline]
       n_tty_receive_buf_common+0x85/0x1930 drivers/tty/n_tty.c:1678
       tty_ldisc_receive_buf+0xaa/0x1a0 drivers/tty/tty_buffer.c:394
       tty_port_default_receive_buf+0x70/0xb0 drivers/tty/tty_port.c:37
       receive_buf drivers/tty/tty_buffer.c:452 [inline]
       flush_to_ldisc+0x26b/0x730 drivers/tty/tty_buffer.c:502
       process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
       process_scheduled_works kernel/workqueue.c:3405 [inline]
       worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
       kthread+0x370/0x450 kernel/kthread.c:436
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

other info that might help us debug this:

Chain exists of:
  &tty->termios_rwsem --> console_lock --> &buf->lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&buf->lock);
                               lock(console_lock);
                               lock(&buf->lock);
  rlock(&tty->termios_rwsem);

 *** DEADLOCK ***

4 locks held by kworker/u33:3/62:
 #0: ffff88801bce4140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x12b1/0x1940 kernel/workqueue.c:3297
 #1: ffffc900009efd08 ((work_completion)(&buf->work)){+.+.}-{0:0}, at: process_one_work+0x988/0x1940 kernel/workqueue.c:3298
 #2: ffff88801404a8b8 (&buf->lock){+.+.}-{4:4}, at: flush_to_ldisc+0x34/0x730 drivers/tty/tty_buffer.c:474
 #3: ffff88804b3fe0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref+0x21/0x90 drivers/tty/tty_ldisc.c:263

stack backtrace:
CPU: 0 UID: 0 PID: 62 Comm: kworker/u33:3 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: events_unbound flush_to_ldisc
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_circular_bug.cold+0x178/0x1c7 kernel/locking/lockdep.c:2043
 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2175
 check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237
 lock_acquire kernel/locking/lockdep.c:5868 [inline]
 lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
 down_read+0x99/0x4c0 kernel/locking/rwsem.c:1574
 class_rwsem_read_constructor include/linux/rwsem.h:259 [inline]
 n_tty_receive_buf_common+0x85/0x1930 drivers/tty/n_tty.c:1678
 tty_ldisc_receive_buf+0xaa/0x1a0 drivers/tty/tty_buffer.c:394
 tty_port_default_receive_buf+0x70/0xb0 drivers/tty/tty_port.c:37
 receive_buf drivers/tty/tty_buffer.c:452 [inline]
 flush_to_ldisc+0x26b/0x730 drivers/tty/tty_buffer.c:502
 process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
 process_scheduled_works kernel/workqueue.c:3405 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

To reproduce this circular locking dependency warning, we need to trigger the lock dependencies that form the cycle. Lockdep tracks dependencies between lock classes globally, so we don't need to cause an actual deadlock; we just need to execute the code paths that take these locks in the required order sequentially.

### Lock Dependency Analysis

The cycle consists of 4 lock classes:
1. `&port->mutex` -> `console_lock`: This dependency is **already recorded during boot** when the kernel registers the serial console (`serial8250_init` -> `uart_configure_port`). We don't need to trigger it manually.
2. `&tty->termios_rwsem` -> `&port->mutex`: This is triggered when setting termios on a serial port. `tty_set_termios` takes `&tty->termios_rwsem` (write) and then calls `uart_set_termios` which takes `&port->mutex`.
3. `console_lock` -> `&buf->lock`: This is triggered by the Secure Attention Key (SAK) on a virtual console. `vc_SAK` takes `console_lock` and then calls `__do_SAK` -> `tty_ldisc_flush` -> `tty_buffer_flush` which takes `&buf->lock`.
4. `&buf->lock` -> `&tty->termios_rwsem`: This is triggered by the normal tty receive path. `flush_to_ldisc` takes `&buf->lock` and then calls `n_tty_receive_buf_common` which takes `&tty->termios_rwsem` (read).

### Reproduction Strategy

We can write a minimal C program that sequentially triggers the remaining 3 dependencies:
1. **Open a serial port** (e.g., `/dev/ttyS0`) and call `ioctl(fd, TCSETS, &term)` to record `&tty->termios_rwsem` -> `&port->mutex`.
2. **Write 'k' to `/proc/sysrq-trigger`** to simulate a SAK keypress. This schedules `vc_SAK` work, recording `console_lock` -> `&buf->lock`.
3. **Open a PTY pair** and write to the slave PTY. This queues data to the master PTY and schedules `flush_to_ldisc`, recording `&buf->lock` -> `&tty->termios_rwsem`.

Once the last dependency is recorded, lockdep will detect the cycle and emit the warning.

### Minimal C Reproducer

```c
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <stdlib.h>

int main(void) {
    // 1. Trigger: &tty->termios_rwsem -> &port->mutex
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial >= 0) {
        struct termios term;
        if (ioctl(fd_serial, TCGETS, &term) == 0) {
            ioctl(fd_serial, TCSETS, &term);
        }
        close(fd_serial);
    }

    // 2. Trigger: console_lock -> &buf->lock
    int fd_sysrq = open("/proc/sysrq-trigger", O_WRONLY);
    if (fd_sysrq >= 0) {
        write(fd_sysrq, "k", 1);
        close(fd_sysrq);
        // Wait a bit for the vc_SAK workqueue to execute
        usleep(100000);
    }

    // 3. Trigger: &buf->lock -> &tty->termios_rwsem
    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx >= 0) {
        grantpt(ptmx);
        unlockpt(ptmx);
        char *pts_name = ptsname(ptmx);
        if (pts_name) {
            int pts = open(pts_name, O_RDWR | O_NOCTTY);
            if (pts >= 0) {
                // Writing to the slave PTY triggers flush_to_ldisc on the master PTY
                write(pts, "a", 1);
                // Wait a bit for the flush_to_ldisc workqueue to execute
                usleep(100000);
                close(pts);
            }
        }
        close(ptmx);
    }

    return 0;
}
```

gemini-3.1-pro-preview

							input: 6065
							output: 158
							thoughts: 709
						

**Analyzing a Circular Locking Dependency in the TTY Subsystem**

I've encountered a concerning circular dependency warning involving several key locking primitives within the TTY subsystem. My goal is to meticulously trace the path of these locks to understand how the cycle is formed. The involved locks are: `&tty->termios_rwsem`, `console_lock`, `&buf->lock`, and `&port->mutex`.

Initially, I'm looking at the dependency chain and trying to connect the dots. I start by examining the relationship between `&buf->lock` and `console_lock`. My initial thought is that `&buf->lock` depends on `console_lock`, but I need to be sure. I trace a path from `&buf->lock`:

*   `&buf->lock` is acquired in `tty_buffer_flush`.
*   `tty_buffer_flush` is called by `tty_ldisc_flush`.
*   `tty_ldisc_flush` is called by `__do_SAK`.
*   `__do_SAK` is called by `vc_SAK`, which is eventually invoked via `process_one_work`.

This chain seems to imply that `tty_buffer_flush` is where `&buf->lock` is acquired. Now, I need to verify the relationship between `__do_SAK` and `console_lock`. I check the implementation of `__do_SAK` and discover that it *doesn't* directly take `console_lock`. However, I recall that `tty_buffer_flush` is the function that acquires `&buf->lock`.

Next, I move on to `console_lock`. I trace the call stack leading to its acquisition:

*   `console_lock` is acquired directly within the `console_lock` function itself.
*   `console_lock` is called by `uart_configure_port`.
*   `uart_configure_port` is called by `serial_core_add_one_port`.
*   `serial_core_add_one_port` is called by `serial_core_register_port`.
*   `serial_core_register_port` is called by `serial8250_register_8250_port`.

This particular path seems to be active during system boot or initialization. The critical point here is whether `uart_configure_port` acquires `console_lock` while *already holding* `&port->mutex`. I need to scrutinize the `uart_configure_port` function to confirm this.

Then, I investigate `&port->mutex`. The chain of acquisition appears to be:

*   `&port->mutex` is acquired in `uart_set_termios`.
*   `uart_set_termios` is called by `tty_set_termios`.
*   `tty_set_termios` is called by `set_termios`.
*   `set_termios` is called by `tty_mode_ioctl`.
*   `tty_mode_ioctl` is called by `n_tty_ioctl_helper`.
*   `n_tty_ioctl_helper` is called by `n_tty_ioctl`.
*   `n_tty_ioctl` is called by `tty_ioctl`.

Here, the crucial observation is whether `uart_set_termios` acquires `&port->mutex` while *holding* `&tty->termios_rwsem`. I will need to examine `tty_set_termios` to verify this.

Finally, I look at `&tty->termios_rwsem`. The path I'm tracing leads to:

*   `&tty->termios_rwsem` is acquired (as a read lock, `rwsem_read_down`) in `n_tty_receive_buf_common`.
*   `n_tty_receive_buf_common` is called by `tty_ldisc_receive_buf`.
*   `tty_ldisc_receive_buf` is called by `tty_port_default_receive_buf`.
*   `tty_port_default_receive_buf` is called by `receive_buf`.
*   `receive_buf` calls `flush_to_ldisc`.

The function `flush_to_ldisc` appears to hold `&buf->lock` and then proceeds to acquire `&tty->termios_rwsem` (as a read lock) via its caller, `n_tty_receive_buf_common`.

Putting it all together, the suspected cycle is as follows:

1.  The `flush_to_ldisc` function holds `&buf->lock` and subsequently attempts to acquire `&tty->termios_rwsem` in read mode.
2.  The `tty_set_termios` function, holding `&tty->termios_rwsem` in write mode, calls `uart_set_termios`, which then acquires `&port->mutex`.
3.  The `uart_configure_port` function, holding `&port->mutex`, then attempts to acquire `console_lock`.
4.  The `__do_SAK` function, which we initially linked to `console_lock`, needs further investigation regarding its locking behavior in conjunction with `vc_SAK`. This is the missing piece that potentially closes the loop back to `&buf->lock` or `&tty->termios_rwsem` in a way that creates the deadlock.

To resolve this, I need to meticulously inspect the source code of `__do_SAK` and `vc_SAK` and any functions they call that might acquire locks. Utilizing static analysis tools and debugging will be crucial to definitively map out the exact lock acquisition order that leads to this circular dependency.

map[ContextFile:drivers/tty/tty_io.c Name:__do_SAK]

map[SourceCode:2997:	/*
2998:	 * This implements the "Secure Attention Key" ---  the idea is to
2999:	 * prevent trojan horses by killing all processes associated with this
3000:	 * tty when the user hits the "Secure Attention Key".  Required for
3001:	 * super-paranoid applications --- see the Orange Book for more details.
3002:	 *
3003:	 * This code could be nicer; ideally it should send a HUP, wait a few
3004:	 * seconds, then send a INT, and then a KILL signal.  But you then
3005:	 * have to coordinate with the init process, since all processes associated
3006:	 * with the current tty must be dead before the new getty is allowed
3007:	 * to spawn.
3008:	 *
3009:	 * Now, if it would be correct ;-/ The current code has a nasty hole -
3010:	 * it doesn't catch files in flight. We may send the descriptor to ourselves
3011:	 * via AF_UNIX socket, close it and later fetch from socket. FIXME.
3012:	 *
3013:	 * Nasty bug: do_SAK is being called in interrupt context.  This can
3014:	 * deadlock.  We punt it up to process context.  AKPM - 16Mar2001
3015:	 */
3016:	void __do_SAK(struct tty_struct *tty)
3017:	{
3018:		struct task_struct *g, *p;
3019:		struct pid *session;
3020:		int i;
3021:	
3022:		scoped_guard(spinlock_irqsave, &tty->ctrl.lock)
3023:			session = get_pid(tty->ctrl.session);
3024:	
3025:		tty_ldisc_flush(tty);
3026:	
3027:		tty_driver_flush_buffer(tty);
3028:	
3029:		read_lock(&tasklist_lock);
3030:		/* Kill the entire session */
3031:		do_each_pid_task(session, PIDTYPE_SID, p) {
3032:			tty_notice(tty, "SAK: killed process %d (%s): by session\n",
3033:				   task_pid_nr(p), p->comm);
3034:			group_send_sig_info(SIGKILL, SEND_SIG_PRIV, p, PIDTYPE_SID);
3035:		} while_each_pid_task(session, PIDTYPE_SID, p);
3036:	
3037:		/* Now kill any processes that happen to have the tty open */
3038:		for_each_process_thread(g, p) {
3039:			if (p->signal->tty == tty) {
3040:				tty_notice(tty, "SAK: killed process %d (%s): by controlling tty\n",
3041:					   task_pid_nr(p), p->comm);
3042:				group_send_sig_info(SIGKILL, SEND_SIG_PRIV, p,
3043:						PIDTYPE_SID);
3044:				continue;
3045:			}
3046:			guard(task_lock)(p);
3047:			i = iterate_fd(p->files, 0, this_tty, tty);
3048:			if (i != 0) {
3049:				tty_notice(tty, "SAK: killed process %d (%s): by fd#%d\n",
3050:					   task_pid_nr(p), p->comm, i - 1);
3051:				group_send_sig_info(SIGKILL, SEND_SIG_PRIV, p,
3052:						PIDTYPE_SID);
3053:			}
3054:		}
3055:		read_unlock(&tasklist_lock);
3056:		put_pid(session);
3057:	}
 SourceFile:drivers/tty/tty_io.c]

map[ContextFile:drivers/tty/vt/vt_ioctl.c Name:vc_SAK]

map[SourceCode: 978:	void vc_SAK(struct work_struct *work)
 979:	{
 980:		struct vc *vc_con =
 981:			container_of(work, struct vc, SAK_work);
 982:		struct vc_data *vc;
 983:		struct tty_struct *tty;
 984:	
 985:		guard(console_lock)();
 986:		vc = vc_con->d;
 987:		if (!vc)
 988:			return;
 989:	
 990:		/* FIXME: review tty ref counting */
 991:		tty = vc->port.tty;
 992:		/* SAK should also work in all raw modes and reset them properly. */
 993:		if (tty)
 994:			__do_SAK(tty);
 995:		reset_vc(vc);
 996:	}
 SourceFile:drivers/tty/vt/vt_ioctl.c]

map[ContextFile:drivers/tty/serial/serial_core.c Name:uart_configure_port]

map[SourceCode:2504:	static void
2505:	uart_configure_port(struct uart_driver *drv, struct uart_state *state,
2506:			    struct uart_port *port)
2507:	{
2508:		unsigned int flags;
2509:	
2510:		/*
2511:		 * If there isn't a port here, don't do anything further.
2512:		 */
2513:		if (!port->iobase && !port->mapbase && !port->membase)
2514:			return;
2515:	
2516:		/*
2517:		 * Now do the auto configuration stuff.  Note that config_port
2518:		 * is expected to claim the resources and map the port for us.
2519:		 */
2520:		flags = 0;
2521:		if (port->flags & UPF_AUTO_IRQ)
2522:			flags |= UART_CONFIG_IRQ;
2523:		if (port->flags & UPF_BOOT_AUTOCONF) {
2524:			if (!(port->flags & UPF_FIXED_TYPE)) {
2525:				port->type = PORT_UNKNOWN;
2526:				flags |= UART_CONFIG_TYPE;
2527:			}
2528:			/* Synchronize with possible boot console. */
2529:			if (uart_console(port))
2530:				console_lock();
2531:			port->ops->config_port(port, flags);
2532:			if (uart_console(port))
2533:				console_unlock();
2534:		}
2535:	
2536:		if (port->type != PORT_UNKNOWN) {
2537:			uart_report_port(drv, port);
2538:	
2539:			/* Synchronize with possible boot console. */
2540:			if (uart_console(port))
2541:				console_lock();
2542:	
2543:			/* Power up port for set_mctrl() */
2544:			uart_change_pm(state, UART_PM_STATE_ON);
2545:	
2546:			/*
2547:			 * Ensure that the modem control lines are de-activated.
2548:			 * keep the DTR setting that is set in uart_set_options()
2549:			 * We probably don't need a spinlock around this, but
2550:			 */
2551:			scoped_guard(uart_port_lock_irqsave, port) {
2552:				unsigned int mask = TIOCM_DTR;
2553:	
2554:				/* Console hardware flow control polls CTS. */
2555:				if (uart_console_hwflow_active(port))
2556:					mask |= TIOCM_RTS;
2557:	
2558:				port->mctrl &= mask;
2559:	
2560:				if (!(port->rs485.flags & SER_RS485_ENABLED))
2561:					port->ops->set_mctrl(port, port->mctrl);
2562:			}
2563:	
2564:			uart_rs485_config(port);
2565:	
2566:			if (uart_console(port))
2567:				console_unlock();
2568:	
2569:			/*
2570:			 * If this driver supports console, and it hasn't been
2571:			 * successfully registered yet, try to re-register it.
2572:			 * It may be that the port was not available.
2573:			 */
2574:			if (port->cons && !console_is_registered(port->cons))
2575:				register_console(port->cons);
2576:	
2577:			/*
2578:			 * Power down all ports by default, except the
2579:			 * console if we have one.
2580:			 */
2581:			if (!uart_console(port))
2582:				uart_change_pm(state, UART_PM_STATE_OFF);
2583:		}
2584:	}
 SourceFile:drivers/tty/serial/serial_core.c]

map[ContextFile:drivers/tty/serial/serial_core.c Name:uart_set_termios]

map[SourceCode:1636:	static void uart_set_termios(struct tty_struct *tty,
1637:				     const struct ktermios *old_termios)
1638:	{
1639:		struct uart_state *state = tty->driver_data;
1640:		struct uart_port *uport;
1641:		unsigned int cflag = tty->termios.c_cflag;
1642:		unsigned int iflag_mask = IGNBRK|BRKINT|IGNPAR|PARMRK|INPCK;
1643:		bool sw_changed = false;
1644:	
1645:		guard(mutex)(&state->port.mutex);
1646:	
1647:		uport = uart_port_check(state);
1648:		if (!uport)
1649:			return;
1650:	
1651:		/*
1652:		 * Drivers doing software flow control also need to know
1653:		 * about changes to these input settings.
1654:		 */
1655:		if (uport->flags & UPF_SOFT_FLOW) {
1656:			iflag_mask |= IXANY|IXON|IXOFF;
1657:			sw_changed =
1658:			   tty->termios.c_cc[VSTART] != old_termios->c_cc[VSTART] ||
1659:			   tty->termios.c_cc[VSTOP] != old_termios->c_cc[VSTOP];
1660:		}
1661:	
1662:		/*
1663:		 * These are the bits that are used to setup various
1664:		 * flags in the low level driver. We can ignore the Bfoo
1665:		 * bits in c_cflag; c_[io]speed will always be set
1666:		 * appropriately by set_termios() in tty_ioctl.c
1667:		 */
1668:		if ((cflag ^ old_termios->c_cflag) == 0 &&
1669:		    tty->termios.c_ospeed == old_termios->c_ospeed &&
1670:		    tty->termios.c_ispeed == old_termios->c_ispeed &&
1671:		    ((tty->termios.c_iflag ^ old_termios->c_iflag) & iflag_mask) == 0 &&
1672:		    !sw_changed)
1673:			return;
1674:	
1675:		uart_change_line_settings(tty, state, old_termios);
1676:		/* reload cflag from termios; port driver may have overridden flags */
1677:		cflag = tty->termios.c_cflag;
1678:	
1679:		/* Handle transition to B0 status */
1680:		if (((old_termios->c_cflag & CBAUD) != B0) && ((cflag & CBAUD) == B0))
1681:			uart_clear_mctrl(uport, TIOCM_RTS | TIOCM_DTR);
1682:		/* Handle transition away from B0 status */
1683:		else if (((old_termios->c_cflag & CBAUD) == B0) && ((cflag & CBAUD) != B0)) {
1684:			unsigned int mask = TIOCM_DTR;
1685:	
1686:			if (!(cflag & CRTSCTS) || !tty_throttled(tty))
1687:				mask |= TIOCM_RTS;
1688:			uart_set_mctrl(uport, mask);
1689:		}
1690:	}
 SourceFile:drivers/tty/serial/serial_core.c]

gemini-3.1-pro-preview

							input: 10436
							output: 38
							thoughts: 1201
						

**My Thoughts on This Lock Dependency Cycle**

Okay, so I've been digging into this lock dependency report, and it's revealing a rather intricate deadlock scenario within the TTY subsystem, specifically around serial port handling. My initial analysis seems to have hit a wall, but then a closer examination of the lockdep output and the code paths clarified the picture.

Here's how I'm piecing it together, and importantly, where the dependency chain forms:

First, I laid out the normal operational cycles for several key functions:
1.  `flush_to_ldisc`: This is a routine operation that acquires `&buf->lock` and then a *read* lock on `&tty->termios_rwsem`. This happens within a normal workqueue context.
2.  `tty_set_termios`: This is triggered by user-space `ioctl` calls like `TCSETS` on a serial port. It acquires a *write* lock on `&tty->termios_rwsem` and then calls into `uart_set_termios`, which in turn takes `&port->mutex`.
3.  `uart_configure_port`: This function is involved during serial port probing, whether at boot or dynamically. It holds `&port->mutex` and then acquires the `console_lock`.
4.  `vc_SAK`: This handles the Secure Attention Key (SAK) event on virtual consoles. It grabs `console_lock`, then calls into `__do_SAK`, which eventually leads to `tty_ldisc_flush` and `tty_buffer_flush`, the latter acquiring `&buf->lock`.

So far, so good. I'm seeing distinct lock acquisitions in these operations.

Now, the lockdep report shows a specific dependency chain that *looks* like a cycle, and my task is to verify it:
*   `&buf->lock` depends on `console_lock`
*   `console_lock` depends on `&port->mutex`
*   `&port->mutex` depends on `&tty->termios_rwsem`
*   `&tty->termios_rwsem` depends on `&buf->lock`

This is where it gets interesting. I need to trace these dependencies through the code to see if they hold up.

Let's break down each link:

1.  **`&buf->lock` -> `&tty->termios_rwsem`**:
    My understanding is that `flush_to_ldisc` acquires `&buf->lock` first. Then, within its execution path, it eventually calls `tty_ldisc_receive_buf` and then `n_tty_receive_buf_common`. It turns out that `n_tty_receive_buf_common` performs a `down_read(&tty->termios_rwsem)`. So, yes, `&buf->lock` *can* lead to acquiring `&tty->termios_rwsem` (in read mode). This dependency seems valid.

2.  **`&tty->termios_rwsem` -> `&port->mutex`**:
    Here, `tty_set_termios` acquires the write lock on `&tty->termios_rwsem`. Subsequently, it calls the driver's `tty->ops->set_termios` callback, which for serial ports is `uart_set_termios`. And indeed, `uart_set_termios` performs a `mutex_lock(&state->port.mutex)`. So, the write lock on `&tty->termios_rwsem` does lead to acquiring `&port->mutex`. This link also checks out.

3.  **`&port->mutex` -> `console_lock`**:
    This dependency is linked to port registration. When a serial port is registered, specifically via `serial_core_register_port`, it takes a global `port_mutex` and then `state->port.mutex`. Crucially, `uart_configure_port` is called during this process, and `uart_configure_port` acquires the `console_lock`. Therefore, `&port->mutex` leads to `console_lock`. This dependency is confirmed.

4.  **`console_lock` -> `&buf->lock`**:
    This is the final piece of the puzzle. The `vc_SAK` routine acquires the `console_lock`. From there, it proceeds to `__do_SAK`, then `tty_ldisc_flush`, and finally `tty_buffer_flush`. And `tty_buffer_flush` performs a `mutex_lock(&buf->lock)`. So, acquiring `console_lock` can indeed lead to acquiring `&buf->lock`. This final dependency is also valid.

And there it is: a complete cycle. `&buf->lock` -> `&tty->termios_rwsem` -> `&port->mutex` -> `console_lock` -> `&buf->lock`.

The critical question then becomes, how does lockdep *observe* this cycle? It needs to see these dependencies established.

My initial thought was that I'd need to *trigger* these functions in a specific sequence or concurrently. However, I realized that the lockdep report itself gives clues. It mentions that `-> #2 (console_lock){+.+.}-{0:0}:` was recorded during boot. This is a significant insight!

It means the dependency `&port->mutex` -> `console_lock` is *already* registered by the kernel during the initialization of the serial driver, likely during `do_basic_setup` -> `serial8250_init` -> `driver_register` -> `uart_configure_port`. So, this part of the cycle is pre-established.

Now, the remaining part is how `console_lock` -> `&buf->lock` gets observed. The `vc_SAK` function is the trigger. How can `vc_SAK` be initiated? It can be triggered by user space, for example, via `echo k > /proc/sysrq-trigger` (if sysrq is enabled). I'm also looking into `ioctl` calls like `TIOCLINUX` with the `VT_SAK` subcode, to see if that's a viable user-space trigger for SAK.

So, the core of my thought process has shifted from "how to create the cycle" to "how lockdep is seeing this pre-existing dependency and how a user-space interaction with SAK could complete the observable cycle." The cycle isn't necessarily being *created* by a single user action, but rather *completed* by a combination of boot-time registration and a subsequent SAK event, which lockdep then detects as a potential deadlock.

map[ContextFile:drivers/tty/vt/vt_ioctl.c Name:tioclinux]

map[SourceCode:3561:	int tioclinux(struct tty_struct *tty, unsigned long arg)
3562:	{
3563:		char type, data;
3564:		char __user *p = (char __user *)arg;
3565:		void __user *param_aligned32 = (u32 __user *)arg + 1;
3566:		void __user *param = (void __user *)arg + 1;
3567:		int lines;
3568:		int ret;
3569:	
3570:		if (current->signal->tty != tty && !capable(CAP_SYS_ADMIN))
3571:			return -EPERM;
3572:		if (get_user(type, p))
3573:			return -EFAULT;
3574:		ret = 0;
3575:	
3576:		switch (type) {
3577:		case TIOCL_SETSEL:
3578:			return set_selection_user(param, tty);
3579:		case TIOCL_PASTESEL:
3580:			if (!capable(CAP_SYS_ADMIN))
3581:				return -EPERM;
3582:			return paste_selection(tty);
3583:		case TIOCL_UNBLANKSCREEN:
3584:			scoped_guard(console_lock)
3585:				unblank_screen();
3586:			break;
3587:		case TIOCL_SELLOADLUT:
3588:			if (!capable(CAP_SYS_ADMIN))
3589:				return -EPERM;
3590:			return sel_loadlut(param_aligned32);
3591:		case TIOCL_GETSHIFTSTATE:
3592:			/*
3593:			 * Make it possible to react to Shift+Mousebutton. Note that
3594:			 * 'shift_state' is an undocumented kernel-internal variable;
3595:			 * programs not closely related to the kernel should not use
3596:			 * this.
3597:			 */
3598:			data = vt_get_shift_state();
3599:			return put_user(data, p);
3600:		case TIOCL_GETMOUSEREPORTING:
3601:			scoped_guard(console_lock)	/* May be overkill */
3602:				data = mouse_reporting();
3603:			return put_user(data, p);
3604:		case TIOCL_SETVESABLANK:
3605:			return set_vesa_blanking(param);
3606:		case TIOCL_GETKMSGREDIRECT:
3607:			data = vt_get_kmsg_redirect();
3608:			return put_user(data, p);
3609:		case TIOCL_SETKMSGREDIRECT:
3610:			if (!capable(CAP_SYS_ADMIN))
3611:				return -EPERM;
3612:	
3613:			if (get_user(data, p+1))
3614:				return -EFAULT;
3615:	
3616:			vt_kmsg_redirect(data);
3617:	
3618:			break;
3619:		case TIOCL_GETFGCONSOLE:
3620:			/*
3621:			 * No locking needed as this is a transiently correct return
3622:			 * anyway if the caller hasn't disabled switching.
3623:			 */
3624:			return fg_console;
3625:		case TIOCL_SCROLLCONSOLE:
3626:			if (get_user(lines, (s32 __user *)param_aligned32))
3627:				return -EFAULT;
3628:	
3629:			/*
3630:			 * Needs the console lock here. Note that lots of other calls
3631:			 * need fixing before the lock is actually useful!
3632:			 */
3633:			scoped_guard(console_lock)
3634:				scrollfront(vc_cons[fg_console].d, lines);
3635:			break;
3636:		case TIOCL_BLANKSCREEN:	/* until explicitly unblanked, not only poked */
3637:			scoped_guard(console_lock) {
3638:				ignore_poke = 1;
3639:				do_blank_screen(0);
3640:			}
3641:			break;
3642:		case TIOCL_BLANKEDSCREEN:
3643:			return console_blanked;
3644:		case TIOCL_GETBRACKETEDPASTE:
3645:			return get_bracketed_paste(tty);
3646:		default:
3647:			return -EINVAL;
3648:		}
3649:	
3650:		return ret;
3651:	}
 SourceFile:drivers/tty/vt/vt.c]

gemini-3.1-pro-preview

							input: 13012
							output: 52
							thoughts: 75
						

**My Thought Process on SAK in `tioclinux`**

Alright, so I was looking into the `tioclinux` functionality, and a question popped into my head: does `tioclinux` actually *implement* the Secure Attention Key (SAK) functionality? My initial intuition was that it might not directly, and that it would likely rely on some other mechanism.

To confirm this, I decided to trace how the SAK mechanism is actually *triggered*. My investigation led me to understand that `vc_SAK` is the function responsible for handling the SAK event. I then dug deeper to see how `vc_SAK` itself is invoked. It turns out `vc_SAK` is executed as a work function. Specifically, it's scheduled by calling `schedule_work(&vc_cons[currcons].SAK_work)`.

This then leads me to my next crucial question: where and under what circumstances is this `SAK_work` actually scheduled? Understanding the origin of the `SAK_work` scheduling is key to determining if `tioclinux` is involved in its initiation, or if it's handled by a different part of the system, perhaps a more generic console or virtual console driver. My current line of inquiry is focused on pinpointing the exact code paths that lead to `vc_SAK` being placed on the work queue.

log-in to see details

map[ContextFile:drivers/tty/vt/vt_ioctl.c IncludeSnippetLines:2 Name:SAK_work SourceTreePrefix:]

map[References:<nil> TruncatedOutput:false]

gemini-3.1-pro-preview

							input: 13138
							output: 30
							thoughts: 23
						

**My Thought Process on Locating SAK_work**

My initial thought, upon encountering the term `SAK_work`, was that it must be a specific field within a data structure. My immediate instinct was to investigate the `vc` structure, as this often pertains to virtual consoles in operating system contexts. Therefore, my next logical step was to perform a targeted search for `SAK_work` within the codebase associated with the `vc` structure. I'm assuming, given your expertise, that you'll recognize the significance of this particular structure and the `SAK_work` element within it, and that this direct line of inquiry is the most efficient way to get to the heart of the matter.

map[Expression:SAK_work PathPrefix:drivers/tty/vt/]

map[Output:drivers/tty/vt/keyboard.c=634=static void fn_SAK(struct vc_data *vc)
drivers/tty/vt/keyboard.c-635-{
drivers/tty/vt/keyboard.c:636:	struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
drivers/tty/vt/keyboard.c:637:	schedule_work(SAK_work);
drivers/tty/vt/keyboard.c-638-}
--
drivers/tty/vt/vt.c=1082=int vc_allocate(unsigned int currcons)	/* return 0 on success */
--
drivers/tty/vt/vt.c-1108-	vc->port.ops = &vc_port_ops;
drivers/tty/vt/vt.c:1109:	INIT_WORK(&vc_cons[currcons].SAK_work, vc_SAK);
drivers/tty/vt/vt.c-1110-
--
drivers/tty/vt/vt.c=3844=static int __init con_init(void)
--
drivers/tty/vt/vt.c-3884-						       GFP_NOWAIT);
drivers/tty/vt/vt.c:3885:		INIT_WORK(&vc_cons[currcons].SAK_work, vc_SAK);
drivers/tty/vt/vt.c-3886-		tty_port_init(&vc->port);
--
drivers/tty/vt/vt_ioctl.c=978=void vc_SAK(struct work_struct *work)
--
drivers/tty/vt/vt_ioctl.c-980-	struct vc *vc_con =
drivers/tty/vt/vt_ioctl.c:981:		container_of(work, struct vc, SAK_work);
drivers/tty/vt/vt_ioctl.c-982-	struct vc_data *vc;
]

gemini-3.1-pro-preview

							input: 13668
							output: 51
							thoughts: 83
						

**My Thought Process Regarding SAK Triggers**

Alright, so I'm looking at this `fn_SAK` function, and it seems to originate from the keyboard handling subsystem. That's a pretty standard place for it to be called from. But my instinct as an expert is always to ask: is this the *only* entry point? Are there other mechanisms that could trigger a "Secure Attention Key" (SAK) event?

My mind immediately jumps to other potential signal-related mechanisms. I'm thinking about things like `KDSIGACCEPT`. That name sounds promising, relating to signals and acceptance. Could `KDSIGACCEPT` be another way to initiate a SAK?

Then, a more specific thought dawns on me: `ioctl(fd, KDSIGACCEPT, ...)` – that's the system call interface. Does *this specific ioctl call* set up a signal to be delivered when a particular keypress occurs? This feels like a distinct possibility, a different path to the same outcome. It's not just about the keyboard driver directly, but about configuring the TTY subsystem itself to be sensitive to certain key events.

To confirm this, my next step is clear: I need to dive into the kernel source code. Specifically, I'll be looking for the implementation of `__do_SAK` within `drivers/tty/tty_io.c`. That file is the heart of TTY operations, and finding `__do_SAK` there will tell me how the SAK signal is ultimately processed and whether the `KDSIGACCEPT` ioctl plays a role in its invocation. This will help me map out the complete set of potential triggers for SAK events.

map[ContextFile:drivers/tty/tty_io.c IncludeSnippetLines:2 Name:__do_SAK SourceTreePrefix:]

map[References:[map[ReferenceKind:calls ReferencingEntityKind:function ReferencingEntityName:do_SAK_work SourceFile:drivers/tty/tty_io.c SourceLine:3063 SourceSnippet:3061:		struct tty_struct *tty =
3062:			container_of(work, struct tty_struct, SAK_work);
3063:		__do_SAK(tty);
3064:	}
] map[ReferenceKind:calls ReferencingEntityKind:function ReferencingEntityName:vc_SAK SourceFile:drivers/tty/vt/vt_ioctl.c SourceLine:994 SourceSnippet: 992:		/* SAK should also work in all raw modes and reset them properly. */
 993:		if (tty)
 994:			__do_SAK(tty);
 995:		reset_vc(vc);
 996:	}
]] TruncatedOutput:false]

gemini-3.1-pro-preview

							input: 14005
							output: 52
							thoughts: 29
						

**My Thought Process Regarding `do_SAK_work`**

Right, so I'm diving into the kernel's TTY subsystem, specifically looking at `drivers/tty/tty_io.c`. My current focus is on this function, `do_SAK_work`. I need to understand its lifecycle and how it gets invoked. My immediate next step is to trace its scheduling – who is responsible for kicking it off? I need to find the call sites and the mechanisms that lead to its execution. This will give me a clearer picture of its role within the TTY driver's operation.

map[ContextFile:drivers/tty/tty_io.c IncludeSnippetLines:2 Name:do_SAK_work SourceTreePrefix:]

map[References:[map[ReferenceKind:takes-address-of ReferencingEntityKind:function ReferencingEntityName:alloc_tty_struct SourceFile:drivers/tty/tty_io.c SourceLine:3126 SourceSnippet:3124:		spin_lock_init(&tty->files_lock);
3125:		INIT_LIST_HEAD(&tty->tty_files);
3126:		INIT_WORK(&tty->SAK_work, do_SAK_work);
3127:	
3128:		tty->driver = driver;
]] TruncatedOutput:false]

gemini-3.1-pro-preview

							input: 14207
							output: 37
							thoughts: 32
						

**My Thought Process Regarding `SAK_work` Scheduling**

Ah, a curious observation has surfaced: it appears that `tty->SAK_work` is being scheduled by the `do_SAK(tty)` function. This immediately piques my interest because, as someone deeply invested in the intricacies of terminal handling and signal management, the precise orchestration of such asynchronous operations is paramount. I need to verify this connection and understand the mechanics behind it. My immediate next step, therefore, is to delve into the implementation of `do_SAK(tty)`. I need to meticulously examine its code path, tracing the execution flow to confirm how and when `tty->SAK_work` is indeed queued for execution. This verification is critical for a comprehensive understanding of the SAK (Secure Attention Key) mechanism's lifecycle and its interaction with the workqueue system.

map[ContextFile:drivers/tty/tty_io.c Name:do_SAK]

map[SourceCode:3066:	/*
3067:	 * The tq handling here is a little racy - tty->SAK_work may already be queued.
3068:	 * Fortunately we don't need to worry, because if ->SAK_work is already queued,
3069:	 * the values which we write to it will be identical to the values which it
3070:	 * already has. --akpm
3071:	 */
3072:	void do_SAK(struct tty_struct *tty)
3073:	{
3074:		if (!tty)
3075:			return;
3076:		schedule_work(&tty->SAK_work);
3077:	}
 SourceFile:drivers/tty/tty_io.c]

gemini-3.1-pro-preview

							input: 14475
							output: 50
							thoughts: 9
						

**My Internal Monologue: Deconstructing the `do_SAK` Invocation**

Alright, let's dive into this. My primary query, the central node of my current investigation, is: "Who, precisely, is orchestrating the execution of this `do_SAK` function?" This isn't just a casual curiosity; it's fundamental to understanding the flow of control, the underlying mechanisms at play, and potentially, the motivations behind this particular action.

I'm not just looking for a simple caller. I need to trace the lineage, the dependencies, the entire call stack that leads to this point. Is it a direct invocation from a known module, or is it buried within a more complex chain of events, perhaps triggered by an external event or a state change within the system? Understanding the context of the call – what state the system is in, what data is available, what preconditions are met – is absolutely critical. This will inform my understanding of *why* `do_SAK` is being called *now*.

Furthermore, I'm considering the implications of this call. What are the expected outcomes? What are the potential side effects? Are there any error handling mechanisms in place for this particular invocation, and if so, where are they managed? The identity of the caller can often provide strong clues about these expectations and the broader purpose of the `do_SAK` operation within the system's architecture. It's about piecing together the narrative of execution, and the identity of the actor initiating the `do_SAK` call is a pivotal piece of that puzzle.

map[ContextFile:drivers/tty/tty_io.c IncludeSnippetLines:2 Name:do_SAK SourceTreePrefix:]

map[References:[map[ReferenceKind:calls ReferencingEntityKind:function ReferencingEntityName:uart_handle_break SourceFile:include/linux/serial_core.h SourceLine:1329 SourceSnippet:1327:	#endif
1328:		if (port->flags & UPF_SAK)
1329:			do_SAK(state->port.tty);
1330:		return 0;
1331:	}
] map[ReferenceKind:takes-address-of ReferencingEntityKind:global_variable ReferencingEntityName:__UNIQUE_ID_addressable_do_SAK_1091 SourceFile:drivers/tty/tty_io.c SourceLine:3078 SourceSnippet:3078:	EXPORT_SYMBOL(do_SAK);
] map[ReferenceKind:takes-address-of ReferencingEntityKind:global_variable ReferencingEntityName:__gendwarfksyms_ptr_do_SAK SourceFile:drivers/tty/tty_io.c SourceLine:3078 SourceSnippet:3078:	EXPORT_SYMBOL(do_SAK);
] map[ReferenceKind:takes-address-of ReferencingEntityKind:global_variable ReferencingEntityName:__gendwarfksyms_ptr_do_SAK SourceFile:drivers/tty/tty_io.c SourceLine:3078 SourceSnippet:3078:	EXPORT_SYMBOL(do_SAK);
]] TruncatedOutput:false]

gemini-3.1-pro-preview

							input: 14835
							output: 32
							thoughts: 25
						

**A Moment of Revelation: System Request and SAK**

My mind just had a jolt of recognition. I was pondering the intricacies of system control when it hit me: the `sysrq` mechanism! I suddenly realized that `sysrq` could actually be the trigger for SAK (Secure Attention Key). This connection feels significant, a crucial piece of the puzzle. I need to verify this immediately. My immediate next step, naturally, is to delve into the source code. I'll be heading straight for `drivers/tty/sysrq.c` to confirm this hypothesis and understand the exact implementation details. This is where the truth lies, and I'm eager to see how these two functionalities are intertwined.

log-in to see details

map[Expression:do_SAK PathPrefix:drivers/tty/sysrq.c]

map[Output:]

gemini-3.1-pro-preview

							input: 14890
							output: 30
							thoughts: 18
						

**My Thought Process on Locating SAK Implementation**

Right, so the immediate objective is to pinpoint how the "System Attention Key" (SAK) functionality is actually implemented within the kernel. Given my expertise, I know that SAK is a critical component, often associated with emergency console operations, and its code is likely to reside in a core driver area. My first instinct, therefore, is to directly inspect the source code. Specifically, I'll be looking for files that handle terminal device drivers, as SAK is intrinsically linked to console interaction. My hypothesis is that the relevant code will be within the `drivers/tty/` directory. I'll be searching for a file named `sysrq.c` because I recall the "Magic SysRq key" functionality, which SAK is a part of, being managed in that specific file. This is a direct, targeted approach, leveraging my familiarity with kernel architecture and common driver locations.

map[Expression:SAK PathPrefix:drivers/tty/sysrq.c]

map[Output:drivers/tty/sysrq.c=109=static const struct sysrq_key_op sysrq_loglevel_op = {
--
drivers/tty/sysrq.c-116-#ifdef CONFIG_VT
drivers/tty/sysrq.c:117:static void sysrq_handle_SAK(u8 key)
drivers/tty/sysrq.c-118-{
drivers/tty/sysrq.c:119:	struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
drivers/tty/sysrq.c-120-
drivers/tty/sysrq.c:121:	schedule_work(SAK_work);
drivers/tty/sysrq.c-122-}
drivers/tty/sysrq.c:123:static const struct sysrq_key_op sysrq_SAK_op = {
drivers/tty/sysrq.c:124:	.handler	= sysrq_handle_SAK,
drivers/tty/sysrq.c-125-	.help_msg	= "sak(k)",
drivers/tty/sysrq.c:126:	.action_msg	= "SAK",
drivers/tty/sysrq.c-127-	.enable_mask	= SYSRQ_ENABLE_KEYBOARD,
--
drivers/tty/sysrq.c-129-#else
drivers/tty/sysrq.c:130:#define sysrq_SAK_op (*(const struct sysrq_key_op *)NULL)
drivers/tty/sysrq.c-131-#endif
--
drivers/tty/sysrq.c=467=static const struct sysrq_key_op *sysrq_key_table[62] = {
--
drivers/tty/sysrq.c-493-	&sysrq_thaw_op,			/* j */
drivers/tty/sysrq.c:494:	&sysrq_SAK_op,			/* k */
drivers/tty/sysrq.c-495-	&sysrq_showallcpus_op,		/* l */
]

gemini-3.1-pro-preview

							input: 15451
							output: 38
							thoughts: 1974
						

**My Thought Process Unraveling a Potential Lock Order Inversion**

Alright, let's break down this lock ordering puzzle. I'm trying to understand how these locks interact, specifically looking for a situation where a deadlock might occur, or more precisely, an inversion of the expected lock order.

My starting point is the `sysrq_handle_SAK` function. I know it ultimately schedules a work item, `vc_SAK`, which is tied to the foreground console. This means if I want to trigger `vc_SAK`, I can do so by writing 'k' to `/proc/sysrq-trigger`. My immediate observation is that `vc_SAK` begins by acquiring `console_lock`, and then it proceeds to acquire a buffer lock, `&buf->lock`.

Now, the crucial part is to map out the dependencies between these locks. I need to understand which lock is acquired *after* another lock, and in what context.

**Dependency Chain Analysis:**

1.  **`&buf->lock` -> `&tty->termios_rwsem`**: I recall that `flush_to_ldisc` is the function that establishes this relationship. This function gets called automatically whenever data is received on a tty. So, I can easily trigger this by writing some data to a pseudoterminal (pty) or a serial port. This `flush_to_ldisc` operation will run within a workqueue context. Ah, I need to be precise: `flush_to_ldisc` acquires `&buf->lock` first, and *then* it attempts to acquire `&tty->termios_rwsem` (in read mode). This is a standard operation for any tty.

2.  **`&tty->termios_rwsem` -> `&port->mutex`**: This dependency arises when a `ioctl(TCSETS)` operation is performed on a serial port. This `ioctl` call will acquire `&tty->termios_rwsem` (in write mode) and then proceed to acquire `&port->mutex`.

3.  **`&port->mutex` -> `console_lock`**: This one seems to be pre-established during the system boot process for serial drivers. The `serial8250_init` function registers serial ports, and in doing so, it takes `&port->mutex` and then `console_lock`. This is a critical observation – it means this dependency is already present in the lockdep graph, and I don't need to explicitly trigger it for the initial setup.

4.  **`console_lock` -> `&buf->lock`**: This is the one I initially identified with `vc_SAK`. When I trigger `vc_SAK` (by writing 'k' to `/proc/sysrq-trigger`), it acquires `console_lock`. From there, it proceeds to call `__do_SAK`, which eventually leads to `tty_ldisc_flush` and then `tty_buffer_flush`. This `tty_buffer_flush` is where `&buf->lock` is acquired. So, `vc_SAK` establishes `console_lock` -> `&buf->lock`.

**Revisiting the Chain and the Goal:**

Given that `&port->mutex` -> `console_lock` is already established, my objective is to create a sequence where:
*   `&buf->lock` -> `&tty->termios_rwsem` (established by `flush_to_ldisc`)
*   `&tty->termios_rwsem` -> `&port->mutex` (established by `ioctl(TCSETS)`)
*   `console_lock` -> `&buf->lock` (established by `vc_SAK`)

This looks like it could form a cycle: `&tty->termios_rwsem` -> `&port->mutex` -> `console_lock` -> `&buf->lock` -> `&tty->termios_rwsem`.

**Refining the Understanding of Lock Classes and Instances:**

I need to be careful about the distinction between lock *classes* and lock *instances*. Lockdep tracks dependencies between lock *classes*.

*   `&buf->lock` is specific to a `tty_port`.
*   `&tty->termios_rwsem` is specific to a `tty_struct`.
*   `&port->mutex` is specific to a `uart_port`.

However, lockdep observes relationships between the *classes* of these locks. So, the chain I'm looking for is:
*   `&buf->lock` class -> `&tty->termios_rwsem` class
*   `&tty->termios_rwsem` class -> `&port->mutex` class
*   `&port->mutex` class -> `console_lock` class
*   `console_lock` class -> `&buf->lock` class

**Confirming the Dependencies with Specific Operations:**

*   **`&tty->termios_rwsem` -> `&port->mutex`**: I'm confident that `ioctl(TCSETS)` on a serial port will acquire `&tty->termios_rwsem` and then `&port->mutex` of the associated `uart_port`. This confirms the class relationship.

*   **`console_lock` -> `&buf->lock`**: As discussed, `vc_SAK` via `sysrq_handle_SAK` triggers `console_lock`, and this leads to `tty_buffer_flush` acquiring `&buf->lock`. This establishes the class relationship.

*   **`&buf->lock` -> `&tty->termios_rwsem`**: This is established by `flush_to_ldisc`, which happens when data arrives at a tty. Since `flush_to_ldisc` acquires `&buf->lock` and then `&tty->termios_rwsem`, this class relationship holds.

**The Crucial Detail: `&port->mutex` -> `console_lock` During Boot**

The lockdep report indicates the following chain:
`-> #3 (&buf->lock){+.+.}-{4:4}:`
`-> #2 (console_lock){+.+.}-{0:0}:`
`-> #1 (&port->mutex){+.+.}-{4:4}:`
`-> #0 (&tty->termios_rwsem){++++}-{4:4}:`

This implies the following ordering:
1.  `&tty->termios_rwsem` is acquired.
2.  Then `&port->mutex` is acquired.
3.  Then `console_lock` is acquired.
4.  Then `&buf->lock` is acquired.

This reveals the complete cycle I was looking for: `&tty->termios_rwsem` -> `&port->mutex` -> `console_lock` -> `&buf->lock` -> `&tty->termios_rwsem`.

**Finalizing the Trigger Sequence:**

Based on this, the sequence to potentially trigger this inversion seems to be:

1.  **Establish `&tty->termios_rwsem` -> `&port->mutex`**: I can achieve this by opening a serial port (let's say `/dev/ttyS0`) and then calling `ioctl(fd, TCSETS, &termios)`. This will acquire `&tty->termios_rwsem` and then `&port->mutex` for that specific serial port.

2.  **Establish `&port->mutex` -> `console_lock`**: This is where the boot time registration becomes important. If `/dev/ttyS0` is the system's console (which is common by default), then during boot, `serial8250_init` would have already registered the `&port->mutex` -> `console_lock` dependency. When I perform the `ioctl` in step 1, I'm using the `&port->mutex` associated with the console serial port, thereby linking `&tty->termios_rwsem` to the `console_lock` class.

3.  **Establish `console_lock` -> `&buf->lock`**: I can trigger this by writing 'k' to `/proc/sysrq-trigger`. This invokes `vc_SAK`, which takes `console_lock` and then subsequently acquires `&buf->lock` via the console's tty path.

4.  **Establish `&buf->lock` -> `&tty->termios_rwsem`**: This is the final piece of the cycle. This dependency is established whenever data is received by *any* tty, triggering `flush_to_ldisc`. The lockdep mechanism observes this as a class-level dependency. So, if there's any pending data on a tty (or I can simulate it by writing to a pty or serial port), this `&buf->lock` -> `&tty->termios_rwsem` link will be considered by lockdep.

The implication is that if these operations happen in the "wrong" order – for example, if the `ioctl` happens *after* `vc_SAK` has acquired `console_lock` and is waiting for `&buf->lock`, and `flush_to_ldisc` is active holding `&buf->lock` and waiting for `&tty->termios_rwsem` which is held by the `ioctl` – then we have a potential deadlock scenario. The lockdep report is showing the *potential* for an inversion if these operations are interleaved in a particular way.

map[ContextFile:drivers/tty/tty_buffer.c Name:tty_buffer_init]

map[SourceCode: 575:	/**
 576:	 * tty_buffer_init		-	prepare a tty buffer structure
 577:	 * @port: tty port to initialise
 578:	 *
 579:	 * Set up the initial state of the buffer management for a tty device. Must be
 580:	 * called before the other tty buffer functions are used.
 581:	 */
 582:	void tty_buffer_init(struct tty_port *port)
 583:	{
 584:		struct tty_bufhead *buf = &port->buf;
 585:	
 586:		mutex_init(&buf->lock);
 587:		tty_buffer_reset(&buf->sentinel, 0);
 588:		buf->head = &buf->sentinel;
 589:		buf->tail = &buf->sentinel;
 590:		init_llist_head(&buf->free);
 591:		atomic_set(&buf->mem_used, 0);
 592:		atomic_set(&buf->priority, 0);
 593:		INIT_WORK(&buf->work, flush_to_ldisc);
 594:		buf->mem_limit = TTYB_DEFAULT_MEM_LIMIT;
 595:	}
 SourceFile:drivers/tty/tty_buffer.c]

gemini-3.1-pro-preview

							input: 17820
							output: 39
							thoughts: 36
						

**My Thought Process Regarding Resource Locking Initialization**

Ah, I've just been pondering the initialization of synchronization primitives, specifically looking at `mutex_init(&buf->lock)`. My immediate recognition is that this call, in its default form, employs the standard, generic lock class for the mutex being initialized. It's a straightforward, no-frills setup.

Now, my mind immediately jumps to a related, but distinct, scenario: `&tty->termios_rwsem`. This brings to the forefront the concept of reader-writer semaphores. I'm mentally contrasting the simple mutual exclusion offered by the `mutex` with the more nuanced locking strategy of an `rwsem`. The latter allows for concurrent read access, which is a crucial distinction in scenarios where reads are frequent and writes are less so, like managing terminal configurations. My internal dialogue is essentially a comparison and confirmation of the underlying mechanisms and their typical use cases.

map[ContextFile:drivers/tty/tty_io.c Name:tty_init_termios]

map[SourceCode:1234:	/**
1235:	 * tty_init_termios - helper for termios setup
1236:	 * @tty: the tty to set up
1237:	 *
1238:	 * Initialise the termios structure for this tty. This runs under the
1239:	 * %tty_mutex currently so we can be relaxed about ordering.
1240:	 */
1241:	void tty_init_termios(struct tty_struct *tty)
1242:	{
1243:		struct ktermios *tp;
1244:		int idx = tty->index;
1245:	
1246:		if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS)
1247:			tty->termios = tty->driver->init_termios;
1248:		else {
1249:			/* Check for lazy saved data */
1250:			tp = tty->driver->termios[idx];
1251:			if (tp != NULL) {
1252:				tty->termios = *tp;
1253:				tty->termios.c_line  = tty->driver->init_termios.c_line;
1254:			} else
1255:				tty->termios = tty->driver->init_termios;
1256:		}
1257:		/* Compatibility until drivers always set this */
1258:		tty->termios.c_ispeed = tty_termios_input_baud_rate(&tty->termios);
1259:		tty->termios.c_ospeed = tty_termios_baud_rate(&tty->termios);
1260:	}
 SourceFile:drivers/tty/tty_io.c]

gemini-3.1-pro-preview

							input: 18358
							output: 51
							thoughts: 13
						

**My Thought Process:**

I'm trying to understand the lifecycle of a critical kernel synchronization primitive, specifically `termios_rwsem`. My immediate question, the first point of inquiry that sparks this thought process, is where exactly this semaphore is initialized within the kernel's code. I need to trace its origin to fully grasp its behavior, dependencies, and potential race conditions, especially considering its role in managing access to termios structures, which are fundamental to terminal I/O operations. Without knowing its initialization point, my understanding of its usage and safety guarantees would be incomplete.

log-in to see details

map[ContextFile:drivers/tty/tty_io.c IncludeSnippetLines:2 Name:termios_rwsem SourceTreePrefix:]

map[References:<nil> TruncatedOutput:false]

gemini-3.1-pro-preview

							input: 18421
							output: 29
							thoughts: 24
						

**My Thought Process**

Alright, so I'm trying to get a handle on how terminal I/O locking is managed within the kernel, and specifically how it relates to the `termios` structure. My first instinct is to dive into the core code responsible for terminal operations. Given that `termios` is central to terminal configuration and behavior, I'm going to focus my search on files that deal with the fundamental I/O aspects of ttys.

Therefore, my immediate next step is to perform a targeted search for `termios_rwsem` within the `drivers/tty/tty_io.c` file. I'm hypothesizing that this symbol, likely an `rw_semaphore` (read-write semaphore) named in relation to `termios`, will be a key indicator of the locking mechanism employed to protect the `termios` structure itself, and perhaps related terminal state, during concurrent read and write operations. Examining this symbol's usage in `tty_io.c` should provide direct insight into how contention for terminal settings is handled and serialized.

map[Expression:termios_rwsem PathPrefix:drivers/tty/]

map[Output:drivers/tty/n_tty.c=84=struct n_tty_data {
--
drivers/tty/n_tty.c-100-
drivers/tty/n_tty.c:101:	/* must hold exclusive termios_rwsem to reset these */
drivers/tty/n_tty.c-102-	unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1;
--
drivers/tty/n_tty.c=161=static void tty_copy(const struct tty_struct *tty, void *to, size_t tail,
--
drivers/tty/n_tty.c-188- * Locking:
drivers/tty/n_tty.c:189: *  * Caller holds exclusive %termios_rwsem, or
drivers/tty/n_tty.c-190- *  * n_tty_read()/consumer path:
drivers/tty/n_tty.c:191: *	holds non-exclusive %termios_rwsem
drivers/tty/n_tty.c-192- */
--
drivers/tty/n_tty.c=255=static void n_tty_check_unthrottle(struct tty_struct *tty)
--
drivers/tty/n_tty.c-292- *  * n_tty_receive_buf()/producer path:
drivers/tty/n_tty.c:293: *	caller holds non-exclusive %termios_rwsem
drivers/tty/n_tty.c-294- */
drivers/tty/n_tty.c=295=static inline void put_tty_queue(u8 c, struct n_tty_data *ldata)
--
drivers/tty/n_tty.c-308- * Locking:
drivers/tty/n_tty.c:309: *  * caller holds exclusive %termios_rwsem, or
drivers/tty/n_tty.c-310- *  * (locking is not required)
--
drivers/tty/n_tty.c=325=static void n_tty_packet_mode_flush(struct tty_struct *tty)
--
drivers/tty/n_tty.c-341- *
drivers/tty/n_tty.c:342: * Holds %termios_rwsem to exclude producer/consumer while buffer indices are
drivers/tty/n_tty.c-343- * reset.
drivers/tty/n_tty.c-344- *
drivers/tty/n_tty.c:345: * Locking: %ctrl.lock, exclusive %termios_rwsem
drivers/tty/n_tty.c-346- */
drivers/tty/n_tty.c=347=static void n_tty_flush_buffer(struct tty_struct *tty)
drivers/tty/n_tty.c-348-{
drivers/tty/n_tty.c:349:	guard(rwsem_write)(&tty->termios_rwsem);
drivers/tty/n_tty.c-350-	reset_buffer_flags(tty->disc_data);
--
drivers/tty/n_tty.c=905=static inline void finish_erasing(struct n_tty_data *ldata)
--
drivers/tty/n_tty.c-922- * Locking: n_tty_receive_buf()/producer path:
drivers/tty/n_tty.c:923: *	caller holds non-exclusive %termios_rwsem
drivers/tty/n_tty.c-924- */
--
drivers/tty/n_tty.c=1067=static void isig(int sig, struct tty_struct *tty)
--
drivers/tty/n_tty.c-1077-	/* signal and flush */
drivers/tty/n_tty.c:1078:	up_read(&tty->termios_rwsem);
drivers/tty/n_tty.c:1079:	scoped_guard(rwsem_write, &tty->termios_rwsem) {
drivers/tty/n_tty.c-1080-		__isig(sig, tty);
--
drivers/tty/n_tty.c-1097-	}
drivers/tty/n_tty.c:1098:	down_read(&tty->termios_rwsem);
drivers/tty/n_tty.c-1099-}
--
drivers/tty/n_tty.c-1108- * Locking: n_tty_receive_buf()/producer path:
drivers/tty/n_tty.c:1109: *	caller holds non-exclusive termios_rwsem
drivers/tty/n_tty.c-1110- *
drivers/tty/n_tty.c:1111: * Note: may get exclusive %termios_rwsem if flushing input buffer
drivers/tty/n_tty.c-1112- */
--
drivers/tty/n_tty.c=1140=static void n_tty_receive_overrun(const struct tty_struct *tty)
--
drivers/tty/n_tty.c-1160- * Locking: n_tty_receive_buf()/producer path:
drivers/tty/n_tty.c:1161: * 	caller holds non-exclusive %termios_rwsem
drivers/tty/n_tty.c-1162- */
--
drivers/tty/n_tty.c=1330=static void n_tty_receive_char_special(struct tty_struct *tty, u8 c,
--
drivers/tty/n_tty.c-1395- * Locking: n_tty_receive_buf()/producer path:
drivers/tty/n_tty.c:1396: *	caller holds non-exclusive %termios_rwsem
drivers/tty/n_tty.c-1397- *	publishes canon_head if canonical mode is active
--
drivers/tty/n_tty.c=1586=static void __receive_buf(struct tty_struct *tty, const u8 *cp, const u8 *fp,
--
drivers/tty/n_tty.c-1666- * Locking: n_tty_receive_buf()/producer path:
drivers/tty/n_tty.c:1667: *	claims non-exclusive %termios_rwsem
drivers/tty/n_tty.c-1668- *	publishes commit_head or canon_head
--
drivers/tty/n_tty.c=1671=n_tty_receive_buf_common(struct tty_struct *tty, const u8 *cp, const u8 *fp,
--
drivers/tty/n_tty.c-1677-
drivers/tty/n_tty.c:1678:	guard(rwsem_read)(&tty->termios_rwsem);
drivers/tty/n_tty.c-1679-
--
drivers/tty/n_tty.c=1756=static size_t n_tty_receive_buf2(struct tty_struct *tty, const u8 *cp,
--
drivers/tty/n_tty.c-1771- *
drivers/tty/n_tty.c:1772: * Locking: Caller holds @tty->termios_rwsem
drivers/tty/n_tty.c-1773- */
--
drivers/tty/n_tty.c=1865=static void n_tty_close(struct tty_struct *tty)
--
drivers/tty/n_tty.c-1871-
drivers/tty/n_tty.c:1872:	guard(rwsem_write)(&tty->termios_rwsem);
drivers/tty/n_tty.c-1873-	vfree(ldata);
--
drivers/tty/n_tty.c=1907=static inline int input_available_p(const struct tty_struct *tty, int poll)
--
drivers/tty/n_tty.c-1932- *  * n_tty_read()/consumer path:
drivers/tty/n_tty.c:1933: *		caller holds non-exclusive %termios_rwsem;
drivers/tty/n_tty.c-1934- *		read_tail published
--
drivers/tty/n_tty.c=1936=static bool copy_from_read_buf(const struct tty_struct *tty, u8 **kbp,
--
drivers/tty/n_tty.c-1987- *  * n_tty_read()/consumer path:
drivers/tty/n_tty.c:1988: *	caller holds non-exclusive %termios_rwsem;
drivers/tty/n_tty.c-1989- *	read_tail published
--
drivers/tty/n_tty.c=2090=static int job_control(struct tty_struct *tty, struct file *file)
--
drivers/tty/n_tty.c-2103-/*
drivers/tty/n_tty.c:2104: * We still hold the atomic_read_lock and the termios_rwsem, and can just
drivers/tty/n_tty.c-2105- * continue to copy data.
--
drivers/tty/n_tty.c=2107=static ssize_t n_tty_continue_cookie(struct tty_struct *tty, u8 *kbuf,
--
drivers/tty/n_tty.c-2129-	n_tty_check_unthrottle(tty);
drivers/tty/n_tty.c:2130:	up_read(&tty->termios_rwsem);
drivers/tty/n_tty.c-2131-	mutex_unlock(&ldata->atomic_read_lock);
--
drivers/tty/n_tty.c=2137=static int n_tty_wait_for_input(struct tty_struct *tty, struct file *file,
--
drivers/tty/n_tty.c-2156-
drivers/tty/n_tty.c:2157:	up_read(&tty->termios_rwsem);
drivers/tty/n_tty.c-2158-	*timeout = wait_woken(wait, TASK_INTERRUPTIBLE, *timeout);
drivers/tty/n_tty.c:2159:	down_read(&tty->termios_rwsem);
drivers/tty/n_tty.c-2160-
--
drivers/tty/n_tty.c-2180- * Locking: n_tty_read()/consumer path:
drivers/tty/n_tty.c:2181: *	claims non-exclusive termios_rwsem;
drivers/tty/n_tty.c-2182- *	publishes read_tail
--
drivers/tty/n_tty.c=2184=static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, u8 *kbuf,
--
drivers/tty/n_tty.c-2214-
drivers/tty/n_tty.c:2215:	down_read(&tty->termios_rwsem);
drivers/tty/n_tty.c-2216-
--
drivers/tty/n_tty.c-2248-		if (!input_available_p(tty, 0)) {
drivers/tty/n_tty.c:2249:			up_read(&tty->termios_rwsem);
drivers/tty/n_tty.c-2250-			tty_buffer_flush_work(tty->port);
drivers/tty/n_tty.c:2251:			down_read(&tty->termios_rwsem);
drivers/tty/n_tty.c-2252-			if (!input_available_p(tty, 0)) {
--
drivers/tty/n_tty.c-2291-	}
drivers/tty/n_tty.c:2292:	up_read(&tty->termios_rwsem);
drivers/tty/n_tty.c-2293-
--
drivers/tty/n_tty.c=2335=static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
--
drivers/tty/n_tty.c-2348-
drivers/tty/n_tty.c:2349:	guard(rwsem_read)(&tty->termios_rwsem);
drivers/tty/n_tty.c-2350-
--
drivers/tty/n_tty.c-2404-		}
drivers/tty/n_tty.c:2405:		up_read(&tty->termios_rwsem);
drivers/tty/n_tty.c-2406-
--
drivers/tty/n_tty.c-2408-
drivers/tty/n_tty.c:2409:		down_read(&tty->termios_rwsem);
drivers/tty/n_tty.c-2410-	}
--
drivers/tty/n_tty.c=2479=static int n_tty_ioctl(struct tty_struct *tty, unsigned int cmd,
--
drivers/tty/n_tty.c-2488-	case TIOCINQ:
drivers/tty/n_tty.c:2489:		scoped_guard(rwsem_write, &tty->termios_rwsem)
drivers/tty/n_tty.c-2490-			if (L_ICANON(tty) && !L_EXTPROC(tty))
--
drivers/tty/pty.c=355=static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
--
drivers/tty/pty.c-379-	tty_set_lock_subclass(o_tty);
drivers/tty/pty.c:380:	lockdep_set_subclass(&o_tty->termios_rwsem, TTY_LOCK_SLAVE);
drivers/tty/pty.c-381-
--
drivers/tty/serial/8250/8250_port.c=2604=void serial8250_update_uartclk(struct uart_port *port, unsigned int uartclk)
--
drivers/tty/serial/8250/8250_port.c-2610-
drivers/tty/serial/8250/8250_port.c:2611:		guard(rwsem_write)(&tty->termios_rwsem);
drivers/tty/serial/8250/8250_port.c-2612-		guard(mutex)(&tport->mutex);
--
drivers/tty/serial/serial_core.c=1032=static int uart_set_info_user(struct tty_struct *tty, struct serial_struct *ss)
--
drivers/tty/serial/serial_core.c-1036-
drivers/tty/serial/serial_core.c:1037:	guard(rwsem_write)(&tty->termios_rwsem);
drivers/tty/serial/serial_core.c-1038-	/*
--
drivers/tty/serial/serial_core.c=1550=uart_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg)
--
drivers/tty/serial/serial_core.c-1559-	if (cmd == TIOCSERCONFIG) {
drivers/tty/serial/serial_core.c:1560:		guard(rwsem_write)(&tty->termios_rwsem);
drivers/tty/serial/serial_core.c-1561-		return uart_do_autoconfig(tty, state);
--
drivers/tty/serial/serial_core.c-1572-	if (cmd == TIOCSRS485)
drivers/tty/serial/serial_core.c:1573:		down_write(&tty->termios_rwsem);
drivers/tty/serial/serial_core.c-1574-
--
drivers/tty/serial/serial_core.c-1615-	if (cmd == TIOCSRS485)
drivers/tty/serial/serial_core.c:1616:		up_write(&tty->termios_rwsem);
drivers/tty/serial/serial_core.c-1617-
--
drivers/tty/tty.h-30- *		  The stable lock order is master pty first, then slave pty.
drivers/tty/tty.h:31: * termios_rwsem - The stable lock order is tty_buffer lock->termios_rwsem.
drivers/tty/tty.h-32- *		   Subclassing this lock enables the slave pty to hold its
drivers/tty/tty.h:33: *		   termios_rwsem when claiming the master tty_buffer lock.
drivers/tty/tty.h-34- * tty_buffer lock - slave ptys can claim nested buffer lock when handling
--
drivers/tty/tty_baudrate.c=198=EXPORT_SYMBOL_GPL(tty_termios_encode_baud_rate);
--
drivers/tty/tty_baudrate.c-206- *	Update the current termios data for the tty with the new speed
drivers/tty/tty_baudrate.c:207: *	settings. The caller must hold the termios_rwsem for the tty in
drivers/tty/tty_baudrate.c-208- *	question.
--
drivers/tty/tty_io.c=530=static struct file *tty_release_redirect(struct tty_struct *tty)
--
drivers/tty/tty_io.c-561- *   * tty_ldiscs_lock from called functions
drivers/tty/tty_io.c:562: *   * termios_rwsem resetting termios data
drivers/tty/tty_io.c-563- *   * tasklist_lock to walk task list for hangup event
--
drivers/tty/tty_io.c=1137=int tty_send_xchar(struct tty_struct *tty, u8 ch)
--
drivers/tty/tty_io.c-1141-	if (tty->ops->send_xchar) {
drivers/tty/tty_io.c:1142:		down_read(&tty->termios_rwsem);
drivers/tty/tty_io.c-1143-		tty->ops->send_xchar(tty, ch);
drivers/tty/tty_io.c:1144:		up_read(&tty->termios_rwsem);
drivers/tty/tty_io.c-1145-		return 0;
--
drivers/tty/tty_io.c-1150-
drivers/tty/tty_io.c:1151:	down_read(&tty->termios_rwsem);
drivers/tty/tty_io.c-1152-	if (was_stopped)
--
drivers/tty/tty_io.c-1156-		stop_tty(tty);
drivers/tty/tty_io.c:1157:	up_read(&tty->termios_rwsem);
drivers/tty/tty_io.c-1158-	tty_write_unlock(tty);
--
drivers/tty/tty_io.c=3098=struct tty_struct *alloc_tty_struct(struct tty_driver *driver, int idx)
--
drivers/tty/tty_io.c-3114-	mutex_init(&tty->throttle_mutex);
drivers/tty/tty_io.c:3115:	init_rwsem(&tty->termios_rwsem);
drivers/tty/tty_io.c-3116-	mutex_init(&tty->winsize_mutex);
--
drivers/tty/tty_ioctl.c=87=EXPORT_SYMBOL(tty_driver_flush_buffer);
--
drivers/tty/tty_ioctl.c-93- * Indicate that a @tty may continue transmitting data down the stack. Takes
drivers/tty/tty_ioctl.c:94: * the &tty_struct->termios_rwsem to protect against parallel
drivers/tty/tty_ioctl.c-95- * throttle/unthrottle and also to ensure the driver can consistently reference
--
drivers/tty/tty_ioctl.c=101=void tty_unthrottle(struct tty_struct *tty)
drivers/tty/tty_ioctl.c-102-{
drivers/tty/tty_ioctl.c:103:	down_write(&tty->termios_rwsem);
drivers/tty/tty_ioctl.c-104-	if (test_and_clear_bit(TTY_THROTTLED, &tty->flags) &&
--
drivers/tty/tty_ioctl.c-107-	tty->flow_change = TTY_FLOW_NO_CHANGE;
drivers/tty/tty_ioctl.c:108:	up_write(&tty->termios_rwsem);
drivers/tty/tty_ioctl.c-109-}
--
drivers/tty/tty_ioctl.c=307=EXPORT_SYMBOL_GPL(tty_get_frame_size);
--
drivers/tty/tty_ioctl.c-316- *
drivers/tty/tty_ioctl.c:317: * Locking: &tty_struct->termios_rwsem
drivers/tty/tty_ioctl.c-318- */
drivers/tty/tty_ioctl.c=319=int tty_set_termios(struct tty_struct *tty, struct ktermios *new_termios)
--
drivers/tty/tty_ioctl.c-332-	   for the set_termios notification eventually */
drivers/tty/tty_ioctl.c:333:	down_write(&tty->termios_rwsem);
drivers/tty/tty_ioctl.c-334-	old_termios = tty->termios;
--
drivers/tty/tty_ioctl.c-350-	}
drivers/tty/tty_ioctl.c:351:	up_write(&tty->termios_rwsem);
drivers/tty/tty_ioctl.c-352-	return 0;
--
drivers/tty/tty_ioctl.c=423=__weak int kernel_termios_to_user_termios(struct termios __user *u,
--
drivers/tty/tty_ioctl.c-439- * Locking: called functions take &tty_struct->ldisc_sem and
drivers/tty/tty_ioctl.c:440: * &tty_struct->termios_rwsem locks
drivers/tty/tty_ioctl.c-441- *
--
drivers/tty/tty_ioctl.c=444=static int set_termios(struct tty_struct *tty, void __user *arg, int opt)
--
drivers/tty/tty_ioctl.c-452-
drivers/tty/tty_ioctl.c:453:	down_read(&tty->termios_rwsem);
drivers/tty/tty_ioctl.c-454-	tmp_termios = tty->termios;
drivers/tty/tty_ioctl.c:455:	up_read(&tty->termios_rwsem);
drivers/tty/tty_ioctl.c-456-
--
drivers/tty/tty_ioctl.c=526=static void copy_termios(struct tty_struct *tty, struct ktermios *kterm)
drivers/tty/tty_ioctl.c-527-{
drivers/tty/tty_ioctl.c:528:	down_read(&tty->termios_rwsem);
drivers/tty/tty_ioctl.c-529-	*kterm = tty->termios;
drivers/tty/tty_ioctl.c:530:	up_read(&tty->termios_rwsem);
drivers/tty/tty_ioctl.c-531-}
--
drivers/tty/tty_ioctl.c=533=static void copy_termios_locked(struct tty_struct *tty, struct ktermios *kterm)
drivers/tty/tty_ioctl.c-534-{
drivers/tty/tty_ioctl.c:535:	down_read(&tty->termios_rwsem);
drivers/tty/tty_ioctl.c-536-	*kterm = tty->termios_locked;
drivers/tty/tty_ioctl.c:537:	up_read(&tty->termios_rwsem);
drivers/tty/tty_ioctl.c-538-}
--
drivers/tty/tty_ioctl.c=573=static int get_sgttyb(struct tty_struct *tty, struct sgttyb __user *sgttyb)
--
drivers/tty/tty_ioctl.c-576-
drivers/tty/tty_ioctl.c:577:	down_read(&tty->termios_rwsem);
drivers/tty/tty_ioctl.c-578-	tmp.sg_ispeed = tty->termios.c_ispeed;
--
drivers/tty/tty_ioctl.c-582-	tmp.sg_flags = get_sgflags(tty);
drivers/tty/tty_ioctl.c:583:	up_read(&tty->termios_rwsem);
drivers/tty/tty_ioctl.c-584-
--
drivers/tty/tty_ioctl.c=588=static void set_sgflags(struct ktermios *termios, int flags)
--
drivers/tty/tty_ioctl.c-620- *
drivers/tty/tty_ioctl.c:621: * Locking: &tty_struct->termios_rwsem
drivers/tty/tty_ioctl.c-622- *
--
drivers/tty/tty_ioctl.c=625=static int set_sgttyb(struct tty_struct *tty, struct sgttyb __user *sgttyb)
--
drivers/tty/tty_ioctl.c-637-
drivers/tty/tty_ioctl.c:638:	down_write(&tty->termios_rwsem);
drivers/tty/tty_ioctl.c-639-	termios = tty->termios;
--
drivers/tty/tty_ioctl.c-645-						termios.c_ospeed);
drivers/tty/tty_ioctl.c:646:	up_write(&tty->termios_rwsem);
drivers/tty/tty_ioctl.c-647-	tty_set_termios(tty, &termios);
--
drivers/tty/tty_ioctl.c=653=static int get_tchars(struct tty_struct *tty, struct tchars __user *tchars)
--
drivers/tty/tty_ioctl.c-656-
drivers/tty/tty_ioctl.c:657:	down_read(&tty->termios_rwsem);
drivers/tty/tty_ioctl.c-658-	tmp.t_intrc = tty->termios.c_cc[VINTR];
--
drivers/tty/tty_ioctl.c-663-	tmp.t_brkc = tty->termios.c_cc[VEOL2];	/* what is brkc anyway? */
drivers/tty/tty_ioctl.c:664:	up_read(&tty->termios_rwsem);
drivers/tty/tty_ioctl.c-665-	return copy_to_user(tchars, &tmp, sizeof(tmp)) ? -EFAULT : 0;
--
drivers/tty/tty_ioctl.c=668=static int set_tchars(struct tty_struct *tty, struct tchars __user *tchars)
--
drivers/tty/tty_ioctl.c-673-		return -EFAULT;
drivers/tty/tty_ioctl.c:674:	down_write(&tty->termios_rwsem);
drivers/tty/tty_ioctl.c-675-	tty->termios.c_cc[VINTR] = tmp.t_intrc;
--
drivers/tty/tty_ioctl.c-680-	tty->termios.c_cc[VEOL2] = tmp.t_brkc;	/* what is brkc anyway? */
drivers/tty/tty_ioctl.c:681:	up_write(&tty->termios_rwsem);
drivers/tty/tty_ioctl.c-682-	return 0;
--
drivers/tty/tty_ioctl.c=687=static int get_ltchars(struct tty_struct *tty, struct ltchars __user *ltchars)
--
drivers/tty/tty_ioctl.c-690-
drivers/tty/tty_ioctl.c:691:	down_read(&tty->termios_rwsem);
drivers/tty/tty_ioctl.c-692-	tmp.t_suspc = tty->termios.c_cc[VSUSP];
--
drivers/tty/tty_ioctl.c-699-	tmp.t_lnextc = tty->termios.c_cc[VLNEXT];
drivers/tty/tty_ioctl.c:700:	up_read(&tty->termios_rwsem);
drivers/tty/tty_ioctl.c-701-	return copy_to_user(ltchars, &tmp, sizeof(tmp)) ? -EFAULT : 0;
--
drivers/tty/tty_ioctl.c=704=static int set_ltchars(struct tty_struct *tty, struct ltchars __user *ltchars)
--
drivers/tty/tty_ioctl.c-710-
drivers/tty/tty_ioctl.c:711:	down_write(&tty->termios_rwsem);
drivers/tty/tty_ioctl.c-712-	tty->termios.c_cc[VSUSP] = tmp.t_suspc;
--
drivers/tty/tty_ioctl.c-719-	tty->termios.c_cc[VLNEXT] = tmp.t_lnextc;
drivers/tty/tty_ioctl.c:720:	up_write(&tty->termios_rwsem);
drivers/tty/tty_ioctl.c-721-	return 0;
--
drivers/tty/tty_ioctl.c-732- *
drivers/tty/tty_ioctl.c:733: * Locking: &tty_struct->termios_rwsem.
drivers/tty/tty_ioctl.c-734- *
--
drivers/tty/tty_ioctl.c=737=static int tty_change_softcar(struct tty_struct *tty, bool enable)
--
drivers/tty/tty_ioctl.c-742-
drivers/tty/tty_ioctl.c:743:	down_write(&tty->termios_rwsem);
drivers/tty/tty_ioctl.c-744-	old = tty->termios;
--
drivers/tty/tty_ioctl.c-750-		ret = -EINVAL;
drivers/tty/tty_ioctl.c:751:	up_write(&tty->termios_rwsem);
drivers/tty/tty_ioctl.c-752-	return ret;
--
drivers/tty/tty_ioctl.c=765=int tty_mode_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg)
--
drivers/tty/tty_ioctl.c-848-			return -EFAULT;
drivers/tty/tty_ioctl.c:849:		down_write(&real_tty->termios_rwsem);
drivers/tty/tty_ioctl.c-850-		real_tty->termios_locked = kterm;
drivers/tty/tty_ioctl.c:851:		up_write(&real_tty->termios_rwsem);
drivers/tty/tty_ioctl.c-852-		return 0;
--
drivers/tty/tty_ioctl.c-865-			return -EFAULT;
drivers/tty/tty_ioctl.c:866:		down_write(&real_tty->termios_rwsem);
drivers/tty/tty_ioctl.c-867-		real_tty->termios_locked = kterm;
drivers/tty/tty_ioctl.c:868:		up_write(&real_tty->termios_rwsem);
drivers/tty/tty_ioctl.c-869-		return ret;
--
drivers/tty/tty_ldisc.c=392=EXPORT_SYMBOL_GPL(tty_ldisc_flush);
--
drivers/tty/tty_ldisc.c-404- *
drivers/tty/tty_ldisc.c:405: * Locking: takes termios_rwsem
drivers/tty/tty_ldisc.c-406- */
drivers/tty/tty_ldisc.c=407=static void tty_set_termios_ldisc(struct tty_struct *tty, int disc)
drivers/tty/tty_ldisc.c-408-{
drivers/tty/tty_ldisc.c:409:	down_write(&tty->termios_rwsem);
drivers/tty/tty_ldisc.c-410-	tty->termios.c_line = disc;
drivers/tty/tty_ldisc.c:411:	up_write(&tty->termios_rwsem);
drivers/tty/tty_ldisc.c-412-
--
drivers/tty/tty_ldisc.c=519=int tty_set_ldisc(struct tty_struct *tty, int disc)
--
drivers/tty/tty_ldisc.c-570-	if (tty->ldisc->ops->num != old_ldisc->ops->num && tty->ops->set_ldisc) {
drivers/tty/tty_ldisc.c:571:		down_read(&tty->termios_rwsem);
drivers/tty/tty_ldisc.c-572-		tty->ops->set_ldisc(tty);
drivers/tty/tty_ldisc.c:573:		up_read(&tty->termios_rwsem);
drivers/tty/tty_ldisc.c-574-	}
--
drivers/tty/tty_ldisc.c=625=static void tty_reset_termios(struct tty_struct *tty)
drivers/tty/tty_ldisc.c-626-{
drivers/tty/tty_ldisc.c:627:	down_write(&tty->termios_rwsem);
drivers/tty/tty_ldisc.c-628-	tty->termios = tty->driver->init_termios;
--
drivers/tty/tty_ldisc.c-630-	tty->termios.c_ospeed = tty_termios_baud_rate(&tty->termios);
drivers/tty/tty_ldisc.c:631:	up_write(&tty->termios_rwsem);
drivers/tty/tty_ldisc.c-632-}
--
drivers/tty/vt/vt.c=1333=EXPORT_SYMBOL(__vc_resize);
--
drivers/tty/vt/vt.c-1343- * Locking: Takes the console sem and the called methods then take the tty
drivers/tty/vt/vt.c:1344: * termios_rwsem and the tty ctrl.lock in that order.
drivers/tty/vt/vt.c-1345- */
]

gemini-3.1-pro-preview

							input: 27253
							output: 38
							thoughts: 1582
						

**My Thought Process on Reproducing Lock Dependencies**

My primary goal here is to precisely reproduce a set of lock dependencies reported by lockdep. I've been analyzing the relationships between `tty->termios_rwsem`, `buf->lock`, `port->mutex`, and `console_lock`.

Initially, I noticed that `alloc_tty_struct` initializes `tty->termios_rwsem` with a default lock class (subclass 0). However, I then saw that `pty_common_install` explicitly sets a different subclass (`TTY_LOCK_SLAVE`, subclass 1) for slave ptys. This immediately told me I need to be careful about which type of TTY I'm working with. For serial ports, it appears to stick with the default subclass 0, as does `buf->lock`.

The lockdep report provides these crucial pieces of information:
*   `ffff88804b3fe2c8 (&tty->termios_rwsem){++++}-{4:4}`
*   `ffff88801404a8b8 (&buf->lock){+.+.}-{4:4}`
*   `ffff88804b3fe0a0 (&tty->ldisc_sem){++++}-{0:0}`

The key dependency I need to reproduce is: `&buf->lock` -> `&tty->termios_rwsem`. The report shows that for the specific scenario, both are using the default lock class (implied by the `{4:4}` and `{4:4}` in the report, which, when combined with the context of `tty->termios_rwsem` and `buf->lock`, suggests they are part of the same default hierarchy and subclass 0 for `tty->termios_rwsem` is what's being observed for the serial port).

To achieve this, my initial plan was:
1.  Open a serial port (`/dev/ttyS0`).
2.  Call `ioctl(fd, TCSETS, &termios)` to establish the `&tty->termios_rwsem` -> `&port->mutex` dependency.
3.  Write to `/proc/sysrq-trigger` (`k`) to trigger `console_lock` -> `&buf->lock`.
4.  Send data to `/dev/ttyS0` to trigger `flush_to_ldisc`, which I thought would record `&buf->lock` -> `&tty->termios_rwsem`.

However, I quickly realized a critical flaw: `flush_to_ldisc` is triggered by *receiving* data, not sending it on a serial port. This means my step 4 was incorrect.

My next thought was to use a pty. I reasoned that if a pty is involved, it might exhibit the desired behavior. I confirmed that `tty_buffer_init` is common to all TTYs, including ptys, so `&buf->lock` would still be subclass 0. The master pty's `&tty->termios_rwsem` also seems to default to subclass 0.

The key insight came when I considered the direction of data flow with ptys:
*   If I write to the *master* pty, it goes to the *slave*'s buffer. The slave's `&tty->termios_rwsem` is subclass 1 (`TTY_LOCK_SLAVE`). This wouldn't help.
*   If I write to the *slave* pty, the data goes to the *master* pty's buffer. The master pty's `&tty->termios_rwsem` is subclass 0. This is exactly what I need! Writing to the slave pty would trigger `flush_to_ldisc` on the *master* pty, which would then acquire `&buf->lock` (subclass 0) and then `down_read(&tty->termios_rwsem)` on the master pty (subclass 0). This perfectly records the `&buf->lock` -> `&tty->termios_rwsem` dependency with the correct subclass.

So, my refined plan for the `&buf->lock` -> `&tty->termios_rwsem` dependency using ptys is:
1.  Open `/dev/ptmx` to get a master pty file descriptor.
2.  Use `grantpt` and `unlockpt`, then open the slave pty to get its file descriptor.
3.  Write data to the *slave* pty's file descriptor. This queues data for the master pty and schedules `flush_to_ldisc` on the master.
4.  `flush_to_ldisc` on the master pty acquires `&buf->lock` and then `down_read(&tty->termios_rwsem)` (both subclass 0).

Now, let's address the other dependencies:

*   **`&tty->termios_rwsem` -> `&port->mutex`**: My initial plan for this is still valid. Open `/dev/ttyS0` and call `ioctl(fd, TCSETS, &termios)`. This correctly acquires `down_write(&tty->termios_rwsem)` (subclass 0) followed by `mutex_lock(&port->mutex)`.

*   **`&port->mutex` -> `console_lock`**: The lockdep report indicates this dependency is already established during boot (`{0:0}`). If `ttyS0` is the console, `uart_configure_port` (which holds `&port->mutex`) is called while `console_lock` is held. I don't think I can easily reproduce this specific acquisition order from user space unless I can trigger port re-registration, which is complex. However, since it's already recorded and shows the default lock class, it's acceptable for reproduction.

*   **`console_lock` -> `&buf->lock`**: My initial plan to write `k` to `/proc/sysrq-trigger` to trigger `vc_SAK`, which then calls `tty_ldisc_flush` and ultimately `mutex_lock(&buf->lock)`, still stands. This is a standard way to trigger this dependency, assuming `CONFIG_MAGIC_SYSRQ` is enabled, which is typical in testing environments like syzkaller. I briefly considered other paths like `tioclinux` but `vc_SAK` is the most direct and reported path for this. I've noted that if this path fails, I might need to investigate further, but for now, it seems reliable.

So, my overall strategy is to combine these steps, ensuring the pty is used for the `buf->lock` -> `termios_rwsem` acquisition and the serial port is used for the `termios_rwsem` -> `port->mutex` acquisition, while relying on the boot-time establishment of `port->mutex` -> `console_lock` and the sysrq trigger for `console_lock` -> `buf->lock`.

map[ContextFile:drivers/tty/vt/vt_ioctl.c Name:vt_ioctl]

map[SourceCode: 723:	/*
 724:	 * We handle the console-specific ioctl's here.  We allow the
 725:	 * capability to modify any console, not just the fg_console.
 726:	 */
 727:	int vt_ioctl(struct tty_struct *tty,
 728:		     unsigned int cmd, unsigned long arg)
 729:	{
 730:		struct vc_data *vc = tty->driver_data;
 731:		void __user *up = (void __user *)arg;
 732:		int i, perm;
 733:		int ret;
 734:	
 735:		/*
 736:		 * To have permissions to do most of the vt ioctls, we either have
 737:		 * to be the owner of the tty, or have CAP_SYS_TTY_CONFIG.
 738:		 */
 739:		perm = 0;
 740:		if (current->signal->tty == tty || capable(CAP_SYS_TTY_CONFIG))
 741:			perm = 1;
 742:	
 743:		ret = vt_k_ioctl(tty, cmd, arg, perm);
 744:		if (ret != -ENOIOCTLCMD)
 745:			return ret;
 746:	
 747:		ret = vt_io_ioctl(vc, cmd, up, perm);
 748:		if (ret != -ENOIOCTLCMD)
 749:			return ret;
 750:	
 751:		switch (cmd) {
 752:		case TIOCLINUX:
 753:			return tioclinux(tty, arg);
 754:		case VT_SETMODE:
 755:		{
 756:			struct vt_mode tmp;
 757:	
 758:			if (!perm)
 759:				return -EPERM;
 760:			if (copy_from_user(&tmp, up, sizeof(struct vt_mode)))
 761:				return -EFAULT;
 762:			if (tmp.mode != VT_AUTO && tmp.mode != VT_PROCESS)
 763:				return -EINVAL;
 764:	
 765:			guard(console_lock)();
 766:			vc->vt_mode = tmp;
 767:			/* the frsig is ignored, so we set it to 0 */
 768:			vc->vt_mode.frsig = 0;
 769:			put_pid(vc->vt_pid);
 770:			vc->vt_pid = get_pid(task_pid(current));
 771:			/* no switch is required -- saw@shade.msu.ru */
 772:			vc->vt_newvt = -1;
 773:			break;
 774:		}
 775:	
 776:		case VT_GETMODE:
 777:		{
 778:			struct vt_mode tmp;
 779:			int rc;
 780:	
 781:			scoped_guard(console_lock)
 782:				memcpy(&tmp, &vc->vt_mode, sizeof(struct vt_mode));
 783:	
 784:			rc = copy_to_user(up, &tmp, sizeof(struct vt_mode));
 785:			if (rc)
 786:				return -EFAULT;
 787:			break;
 788:		}
 789:	
 790:		/*
 791:		 * Returns global vt state. Note that VT 0 is always open, since
 792:		 * it's an alias for the current VT, and people can't use it here.
 793:		 * We cannot return state for more than 16 VTs, since v_state is short.
 794:		 */
 795:		case VT_GETSTATE:
 796:		{
 797:			struct vt_stat __user *vtstat = up;
 798:			unsigned short state, mask;
 799:	
 800:			if (put_user(fg_console + 1, &vtstat->v_active))
 801:				return -EFAULT;
 802:	
 803:			state = 1;	/* /dev/tty0 is always open */
 804:			scoped_guard(console_lock) /* required by vt_in_use() */
 805:				for (i = 0, mask = 2; i < MAX_NR_CONSOLES && mask; ++i, mask <<= 1)
 806:					if (vt_in_use(i))
 807:						state |= mask;
 808:			return put_user(state, &vtstat->v_state);
 809:		}
 810:	
 811:		/*
 812:		 * Returns the first available (non-opened) console.
 813:		 */
 814:		case VT_OPENQRY:
 815:			scoped_guard(console_lock) /* required by vt_in_use() */
 816:				for (i = 0; i < MAX_NR_CONSOLES; ++i)
 817:					if (!vt_in_use(i))
 818:						break;
 819:			i = i < MAX_NR_CONSOLES ? (i+1) : -1;
 820:			return put_user(i, (int __user *)arg);
 821:	
 822:		/*
 823:		 * ioctl(fd, VT_ACTIVATE, num) will cause us to switch to vt # num,
 824:		 * with num >= 1 (switches to vt 0, our console, are not allowed, just
 825:		 * to preserve sanity).
 826:		 */
 827:		case VT_ACTIVATE:
 828:			if (!perm)
 829:				return -EPERM;
 830:			if (arg == 0 || arg > MAX_NR_CONSOLES)
 831:				return -ENXIO;
 832:	
 833:			arg--;
 834:			arg = array_index_nospec(arg, MAX_NR_CONSOLES);
 835:			scoped_guard(console_lock) {
 836:				ret = vc_allocate(arg);
 837:				if (ret)
 838:					return ret;
 839:			}
 840:			set_console(arg);
 841:			break;
 842:	
 843:		case VT_SETACTIVATE:
 844:			if (!perm)
 845:				return -EPERM;
 846:	
 847:			return vt_setactivate(up);
 848:	
 849:		/*
 850:		 * wait until the specified VT has been activated
 851:		 */
 852:		case VT_WAITACTIVE:
 853:			if (!perm)
 854:				return -EPERM;
 855:			if (arg == 0 || arg > MAX_NR_CONSOLES)
 856:				return -ENXIO;
 857:			return vt_waitactive(arg);
 858:	
 859:		/*
 860:		 * If a vt is under process control, the kernel will not switch to it
 861:		 * immediately, but postpone the operation until the process calls this
 862:		 * ioctl, allowing the switch to complete.
 863:		 *
 864:		 * According to the X sources this is the behavior:
 865:		 *	0:	pending switch-from not OK
 866:		 *	1:	pending switch-from OK
 867:		 *	2:	completed switch-to OK
 868:		 */
 869:		case VT_RELDISP:
 870:		{
 871:			if (!perm)
 872:				return -EPERM;
 873:	
 874:			guard(console_lock)();
 875:			return vt_reldisp(vc, arg);
 876:		}
 877:	
 878:		 /*
 879:		  * Disallocate memory associated to VT (but leave VT1)
 880:		  */
 881:		 case VT_DISALLOCATE:
 882:			if (arg > MAX_NR_CONSOLES)
 883:				return -ENXIO;
 884:	
 885:			if (arg == 0) {
 886:				vt_disallocate_all();
 887:				break;
 888:			}
 889:	
 890:			arg = array_index_nospec(arg - 1, MAX_NR_CONSOLES);
 891:			return vt_disallocate(arg);
 892:	
 893:		case VT_RESIZE:
 894:		{
 895:			struct vt_sizes __user *vtsizes = up;
 896:			struct vc_data *vc;
 897:			ushort ll,cc;
 898:	
 899:			if (!perm)
 900:				return -EPERM;
 901:			if (get_user(ll, &vtsizes->v_rows) ||
 902:			    get_user(cc, &vtsizes->v_cols))
 903:				return -EFAULT;
 904:	
 905:			guard(console_lock)();
 906:			for (i = 0; i < MAX_NR_CONSOLES; i++) {
 907:				vc = vc_cons[i].d;
 908:	
 909:				if (vc) {
 910:					/* FIXME: review v tty lock */
 911:					ret = __vc_resize(vc_cons[i].d, cc, ll, true);
 912:					if (ret)
 913:						return ret;
 914:				}
 915:			}
 916:			break;
 917:		}
 918:	
 919:		case VT_RESIZEX:
 920:			if (!perm)
 921:				return -EPERM;
 922:	
 923:			return vt_resizex(vc, up);
 924:	
 925:		case VT_LOCKSWITCH:
 926:			if (!capable(CAP_SYS_TTY_CONFIG))
 927:				return -EPERM;
 928:			vt_dont_switch = true;
 929:			break;
 930:		case VT_UNLOCKSWITCH:
 931:			if (!capable(CAP_SYS_TTY_CONFIG))
 932:				return -EPERM;
 933:			vt_dont_switch = false;
 934:			break;
 935:		case VT_GETHIFONTMASK:
 936:			return put_user(vc->vc_hi_font_mask,
 937:						(unsigned short __user *)arg);
 938:		case VT_WAITEVENT:
 939:			return vt_event_wait_ioctl((struct vt_event __user *)arg);
 940:	
 941:		case VT_GETCONSIZECSRPOS:
 942:		{
 943:			struct vt_consizecsrpos concsr;
 944:	
 945:			console_lock();
 946:			concsr.con_cols = vc->vc_cols;
 947:			concsr.con_rows = vc->vc_rows;
 948:			concsr.csr_col = vc->state.x;
 949:			concsr.csr_row = vc->state.y;
 950:			console_unlock();
 951:			if (copy_to_user(up, &concsr, sizeof(concsr)))
 952:				return -EFAULT;
 953:			return 0;
 954:		}
 955:	
 956:		default:
 957:			return -ENOIOCTLCMD;
 958:		}
 959:	
 960:		return 0;
 961:	}
 SourceFile:drivers/tty/vt/vt_ioctl.c]

gemini-3.1-pro-preview

							input: 32234
							output: 37
							thoughts: 92
						

**My Thought Process Regarding `__vc_resize` and Console Locking**

Okay, so I'm looking at this code, specifically the `__vc_resize` function. My immediate thought is a bit of a "hold on a minute." It's noted that `__vc_resize` *does* take `console_lock`, which is already held in `VT_RESIZE`. This seems like a potential point of contention, especially given the `FIXME` comment right there about reviewing the `vt_tty lock`. It immediately triggers a question in my mind: does `__vc_resize` also require `&buf->lock`? I need to dig into the `__vc_resize` function itself to see what its locking requirements truly are and if there's a potential for deadlocks or incorrect locking protocols given the existing `console_lock` being held.

map[ContextFile:drivers/tty/vt/vt.c Name:__vc_resize]

map[SourceCode:1315:	/**
1316:	 * __vc_resize - resize a VT
1317:	 * @vc: virtual console
1318:	 * @cols: columns
1319:	 * @rows: rows
1320:	 * @from_user: invoked by a user?
1321:	 *
1322:	 * Resize a virtual console as seen from the console end of things. We use the
1323:	 * common vc_do_resize() method to update the structures.
1324:	 *
1325:	 * Locking: The caller must hold the console sem to protect console internals
1326:	 * and @vc->port.tty.
1327:	 */
1328:	int __vc_resize(struct vc_data *vc, unsigned int cols, unsigned int rows,
1329:			bool from_user)
1330:	{
1331:		return vc_do_resize(vc->port.tty, vc, cols, rows, from_user);
1332:	}
 SourceFile:drivers/tty/vt/vt.c]

gemini-3.1-pro-preview

							input: 32646
							output: 38
							thoughts: 11
						

**My Thought Process Regarding `vc_do_resize`**

Alright, so my immediate inclination is to dive into the specifics of `vc_do_resize`. I need to understand its functionality, its inputs, its outputs, and crucially, how it interacts with other components within the broader system. My expectation is that this function is likely responsible for managing the dynamic adjustment of video codec resources, perhaps related to buffer allocation, resolution scaling, or potentially even adaptive bitrate streaming logic. I'll be looking for documentation, source code annotations, or any relevant API references to get a clear picture of its intended behavior and any potential side effects or limitations. Understanding its context within the overall video processing pipeline is paramount.

map[ContextFile:drivers/tty/vt/vt.c Name:vc_do_resize]

map[SourceCode:1154:	/**
1155:	 * vc_do_resize - resizing method for the tty
1156:	 * @tty: tty being resized
1157:	 * @vc: virtual console private data
1158:	 * @cols: columns
1159:	 * @lines: lines
1160:	 * @from_user: invoked by a user?
1161:	 *
1162:	 * Resize a virtual console, clipping according to the actual constraints. If
1163:	 * the caller passes a tty structure then update the termios winsize
1164:	 * information and perform any necessary signal handling.
1165:	 *
1166:	 * Locking: Caller must hold the console semaphore. Takes the termios rwsem and
1167:	 * ctrl.lock of the tty IFF a tty is passed.
1168:	 */
1169:	static int vc_do_resize(struct tty_struct *tty, struct vc_data *vc,
1170:				unsigned int cols, unsigned int lines, bool from_user)
1171:	{
1172:		unsigned long old_origin, new_origin, new_scr_end, rlth, rrem, err = 0;
1173:		unsigned long end;
1174:		unsigned int old_rows, old_row_size, first_copied_row;
1175:		unsigned int new_cols, new_rows, new_row_size, new_screen_size;
1176:		unsigned short *oldscreen, *newscreen;
1177:		u32 **new_uniscr = NULL;
1178:	
1179:		WARN_CONSOLE_UNLOCKED();
1180:	
1181:		if (cols > VC_MAXCOL || lines > VC_MAXROW)
1182:			return -EINVAL;
1183:	
1184:		new_cols = (cols ? cols : vc->vc_cols);
1185:		new_rows = (lines ? lines : vc->vc_rows);
1186:		new_row_size = new_cols << 1;
1187:		new_screen_size = new_row_size * new_rows;
1188:	
1189:		if (new_cols == vc->vc_cols && new_rows == vc->vc_rows) {
1190:			/*
1191:			 * This function is being called here to cover the case
1192:			 * where the userspace calls the FBIOPUT_VSCREENINFO twice,
1193:			 * passing the same fb_var_screeninfo containing the fields
1194:			 * yres/xres equal to a number non-multiple of vc_font.height
1195:			 * and yres_virtual/xres_virtual equal to number lesser than the
1196:			 * vc_font.height and yres/xres.
1197:			 * In the second call, the struct fb_var_screeninfo isn't
1198:			 * being modified by the underlying driver because of the
1199:			 * if above, and this causes the fbcon_display->vrows to become
1200:			 * negative and it eventually leads to out-of-bound
1201:			 * access by the imageblit function.
1202:			 * To give the correct values to the struct and to not have
1203:			 * to deal with possible errors from the code below, we call
1204:			 * the resize_screen here as well.
1205:			 */
1206:			return resize_screen(vc, new_cols, new_rows, from_user);
1207:		}
1208:	
1209:		if (new_screen_size > KMALLOC_MAX_SIZE || !new_screen_size)
1210:			return -EINVAL;
1211:		newscreen = kzalloc(new_screen_size, GFP_USER);
1212:		if (!newscreen)
1213:			return -ENOMEM;
1214:	
1215:		if (vc->vc_uni_lines) {
1216:			new_uniscr = vc_uniscr_alloc(new_cols, new_rows);
1217:			if (!new_uniscr) {
1218:				kfree(newscreen);
1219:				return -ENOMEM;
1220:			}
1221:		}
1222:	
1223:		if (vc_is_sel(vc))
1224:			clear_selection();
1225:	
1226:		old_rows = vc->vc_rows;
1227:		old_row_size = vc->vc_size_row;
1228:	
1229:		err = resize_screen(vc, new_cols, new_rows, from_user);
1230:		if (err) {
1231:			kfree(newscreen);
1232:			vc_uniscr_free(new_uniscr);
1233:			return err;
1234:		}
1235:	
1236:		vc->vc_rows = new_rows;
1237:		vc->vc_cols = new_cols;
1238:		vc->vc_size_row = new_row_size;
1239:		vc->vc_screenbuf_size = new_screen_size;
1240:	
1241:		rlth = min(old_row_size, new_row_size);
1242:		rrem = new_row_size - rlth;
1243:		old_origin = vc->vc_origin;
1244:		new_origin = (long) newscreen;
1245:		new_scr_end = new_origin + new_screen_size;
1246:	
1247:		if (vc->state.y > new_rows) {
1248:			if (old_rows - vc->state.y < new_rows) {
1249:				/*
1250:				 * Cursor near the bottom, copy contents from the
1251:				 * bottom of buffer
1252:				 */
1253:				first_copied_row = (old_rows - new_rows);
1254:			} else {
1255:				/*
1256:				 * Cursor is in no man's land, copy 1/2 screenful
1257:				 * from the top and bottom of cursor position
1258:				 */
1259:				first_copied_row = (vc->state.y - new_rows/2);
1260:			}
1261:			old_origin += first_copied_row * old_row_size;
1262:		} else
1263:			first_copied_row = 0;
1264:		end = old_origin + old_row_size * min(old_rows, new_rows);
1265:	
1266:		vc_uniscr_copy_area(new_uniscr, new_cols, new_rows,
1267:				    vc->vc_uni_lines, rlth/2, first_copied_row,
1268:				    min(old_rows, new_rows));
1269:		vc_uniscr_set(vc, new_uniscr);
1270:	
1271:		update_attr(vc);
1272:	
1273:		while (old_origin < end) {
1274:			scr_memcpyw((unsigned short *) new_origin,
1275:				    (unsigned short *) old_origin, rlth);
1276:			if (rrem)
1277:				scr_memsetw((void *)(new_origin + rlth),
1278:					    vc->vc_video_erase_char, rrem);
1279:			old_origin += old_row_size;
1280:			new_origin += new_row_size;
1281:		}
1282:		if (new_scr_end > new_origin)
1283:			scr_memsetw((void *)new_origin, vc->vc_video_erase_char,
1284:				    new_scr_end - new_origin);
1285:		oldscreen = vc->vc_screenbuf;
1286:		vc->vc_screenbuf = newscreen;
1287:		vc->vc_screenbuf_size = new_screen_size;
1288:		set_origin(vc);
1289:		kfree(oldscreen);
1290:	
1291:		/* do part of a reset_terminal() */
1292:		vc->vc_top = 0;
1293:		vc->vc_bottom = vc->vc_rows;
1294:		gotoxy(vc, vc->state.x, vc->state.y);
1295:		save_cur(vc);
1296:	
1297:		if (tty) {
1298:			/* Rewrite the requested winsize data with the actual
1299:			   resulting sizes */
1300:			struct winsize ws;
1301:			memset(&ws, 0, sizeof(ws));
1302:			ws.ws_row = vc->vc_rows;
1303:			ws.ws_col = vc->vc_cols;
1304:			ws.ws_ypixel = vc->vc_scan_lines;
1305:			tty_do_resize(tty, &ws);
1306:		}
1307:	
1308:		if (con_is_visible(vc))
1309:			update_screen(vc);
1310:		vt_event_post(VT_EVENT_RESIZE, vc->vc_num, vc->vc_num);
1311:		notify_update(vc);
1312:		return err;
1313:	}
 SourceFile:drivers/tty/vt/vt.c]

gemini-3.1-pro-preview

							input: 35310
							output: 38
							thoughts: 33
						

**My Thought Process Regarding `vc_do_resize` and `tty_do_resize`**

Okay, so I'm looking at `vc_do_resize` and I see it immediately calls `tty_do_resize(tty, &ws)`. My first instinct, as an expert in this area, is to understand the flow of operations and how this particular function integrates into the broader TTY subsystem. Therefore, my immediate next step is to delve into the implementation of `tty_do_resize` itself. I need to understand precisely what it does with the `tty` structure and the `ws` (which I'm assuming is a `winsize` structure based on the context of resizing). This will be crucial for tracing the effects of `vc_do_resize` and ensuring the TTY's state is correctly updated after a video card-initiated resize.

map[ContextFile:drivers/tty/tty_io.c Name:tty_do_resize]

map[SourceCode:2316:	/**
2317:	 * tty_do_resize - resize event
2318:	 * @tty: tty being resized
2319:	 * @ws: new dimensions
2320:	 *
2321:	 * Update the termios variables and send the necessary signals to peform a
2322:	 * terminal resize correctly.
2323:	 */
2324:	int tty_do_resize(struct tty_struct *tty, struct winsize *ws)
2325:	{
2326:		struct pid *pgrp;
2327:	
2328:		guard(mutex)(&tty->winsize_mutex);
2329:	
2330:		if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
2331:			return 0;
2332:	
2333:		/* Signal the foreground process group */
2334:		pgrp = tty_get_pgrp(tty);
2335:		if (pgrp)
2336:			kill_pgrp(pgrp, SIGWINCH, 1);
2337:		put_pid(pgrp);
2338:	
2339:		tty->winsize = *ws;
2340:	
2341:		return 0;
2342:	}
 SourceFile:drivers/tty/tty_io.c]

gemini-3.1-pro-preview

							input: 35750
							output: 37
							thoughts: 75
						

**My Thought Process Regarding `tty_do_resize` and Related Operations**

Okay, so my initial hypothesis was that `tty_do_resize` likely uses `&buf->lock` as a parameter. However, a quick mental check (or perhaps a quick skim of the relevant code if I were actually debugging this) reveals that's not the case. This immediately tells me that `VT_RESIZE`, which I know often interacts with `tty_do_resize` or similar terminal buffer resizing mechanisms, also wouldn't be taking `&buf->lock`.

Now, I need to consider other related ioctl commands that might interact with the terminal buffer or its allocation. `VT_DISALLOCATE` comes to mind. I recall (or would verify) that `VT_DISALLOCATE` internally calls `vt_disallocate`. And tracing that further, `vt_disallocate` then calls `vc_deallocate`. This is where I need to focus my attention next. The deallocation process is a critical part of buffer management, and I want to confirm if *that* operation, specifically `vc_deallocate`, is indeed taking `&buf->lock`. My current suspicion, based on the previous negation, is that it might not be, but it's essential to confirm.

map[ContextFile:drivers/tty/vt/vt.c Name:vc_deallocate]

map[SourceCode:1354:	struct vc_data *vc_deallocate(unsigned int currcons)
1355:	{
1356:		struct vc_data *vc = NULL;
1357:	
1358:		WARN_CONSOLE_UNLOCKED();
1359:	
1360:		if (vc_cons_allocated(currcons)) {
1361:			struct vt_notifier_param param;
1362:	
1363:			param.vc = vc = vc_cons[currcons].d;
1364:			atomic_notifier_call_chain(&vt_notifier_list, VT_DEALLOCATE, &param);
1365:			vcs_remove_sysfs(currcons);
1366:			visual_deinit(vc);
1367:			con_free_unimap(vc);
1368:			put_pid(vc->vt_pid);
1369:			vc_uniscr_set(vc, NULL);
1370:			kfree(vc->vc_screenbuf);
1371:			vc_cons[currcons].d = NULL;
1372:			if (vc->vc_saved_screen != NULL) {
1373:				kfree(vc->vc_saved_screen);
1374:				vc->vc_saved_screen = NULL;
1375:			}
1376:			vc_uniscr_free(vc->vc_saved_uni_lines);
1377:			vc->vc_saved_uni_lines = NULL;
1378:		}
1379:		return vc;
1380:	}
 SourceFile:drivers/tty/vt/vt.c]

gemini-3.1-pro-preview

							input: 36292
							output: 40
							thoughts: 1971
						

**My Thought Process Unpacking the Locking Dependencies**

Okay, so I've been digging into these lock dependency reports, trying to piece together the precise sequence of lock acquisitions. My initial observation was that `vc_SAK` seemed to be the *only* path that acquired `console_lock` and then subsequently `&buf->lock`. I confirmed this action is triggered by writing 'k' to `/proc/sysrq-trigger`. This led me to want to reproduce this behavior programmatically, so I started sketching out a C program using threads to simulate concurrent lock acquisitions.

My first attempt at the C code involved three threads. `thread1` aimed to trigger the `&tty->termios_rwsem` followed by `&port->mutex` sequence by performing `TCGETS` and `TCSETS` ioctls on a serial port. `thread2` was intended to trigger the `console_lock` to `&buf->lock` path by writing to `/proc/sysrq-trigger`. And `thread3` was designed to hit the `&buf->lock` to `&tty->termios_rwsem` pathway by writing to a slave pty, hoping to cause a `flush_to_ldisc` on the master.

However, as I reviewed the lockdep output again, I realized a crucial detail: the report indicated that the `&port->mutex` to `console_lock` acquisition was recorded *during boot*. This immediately shifted my focus. I initially wondered if I'd need to actively trigger port registration (perhaps by loading a module or writing to `/sys/bus/platform/drivers/serial8250/bind`) to establish this dependency. But the lockdep output, specifically the `-> #2 (console_lock){+.+.}-{0:0}` annotation and the accompanying stack trace showing `uart_configure_port` and `serial_core_register_port` calls during `do_basic_setup`, confirmed this lock ordering was a static, established dependency from the early boot process. So, I don't need to worry about triggering that specific acquisition.

This clarification allowed me to re-focus on validating the other two lock pairings within my C program.

First, I revisited the `&buf->lock` -> `&tty->termios_rwsem` dependency. My `thread3` was designed to test this by writing to a pty. I traced the execution path: writing to the slave pty (`pty_write`) calls `tty_insert_flip_string` on the master, which then calls `tty_flip_buffer_push`. This, in turn, schedules `flush_to_ldisc` on the master. `flush_to_ldisc` indeed acquires `mutex_lock(&buf->lock)` (subclass 0). Subsequently, it calls into the line discipline (`n_tty_receive_buf_common`), which takes `down_read(&tty->termios_rwsem)` (subclass 0). This sequence perfectly matches the lock classes reported. I also double-checked that `tty_buffer_init` initializes `&buf->lock` with subclass 0, and `flush_to_ldisc` is a workqueue function that starts with no locks, ensuring this is a valid dependency.

Next, I scrutinized the `&tty->termios_rwsem` -> `&port->mutex` ordering, which my `thread1` was meant to test using `TCSETS` on `/dev/ttyS0`. I followed the path: `tty_ioctl` -> `n_tty_ioctl` -> `n_tty_ioctl_helper` -> `tty_mode_ioctl` -> `set_termios` -> `tty_set_termios`. `tty_set_termios` takes `down_write(&tty->termios_rwsem)` (subclass 0). Then, it calls `tty->ops->set_termios`, which for serial ports is `uart_set_termios`. Crucially, I confirmed by examining the `uart_set_termios` source code that it *unconditionally* acquires `mutex_lock(&state->port.mutex)` (subclass 0). This again aligns precisely with the lock classes in the report. I also verified that `uart_set_termios` always takes this mutex, regardless of other conditions.

Finally, I re-examined the `console_lock` -> `&buf->lock` relationship, which is triggered by `echo k > /proc/sysrq-trigger`. My `thread2` covers this. The path is: `sysrq_handle_SAK` schedules `vc_cons[fg_console].SAK_work`. The `vc_SAK` workqueue handler acquires `console_lock()`. It then calls `__do_SAK(tty)`, which in turn calls `tty_ldisc_flush(tty)`. `tty_ldisc_flush` calls `tty_buffer_flush(tty)`, and `tty_buffer_flush` acquires `mutex_lock(&buf->lock)`. This is a direct match for the reported dependency. The only remaining question was whether `tty_ldisc_flush` *always* calls `tty_buffer_flush`. My current understanding is that it does, and I haven't found any conditions that would prevent this.

So, after this detailed review and trace, the C program seems to be a valid approach to demonstrating these specific lock ordering scenarios.

map[ContextFile:drivers/tty/tty_ldisc.c Name:tty_ldisc_flush]

map[SourceCode: 377:	/**
 378:	 * tty_ldisc_flush		-	flush line discipline queue
 379:	 * @tty: tty to flush ldisc for
 380:	 *
 381:	 * Flush the line discipline queue (if any) and the tty flip buffers for this
 382:	 * @tty.
 383:	 */
 384:	void tty_ldisc_flush(struct tty_struct *tty)
 385:	{
 386:		struct tty_ldisc *ld = tty_ldisc_ref(tty);
 387:	
 388:		tty_buffer_flush(tty, ld);
 389:		if (ld)
 390:			tty_ldisc_deref(ld);
 391:	}
 SourceFile:drivers/tty/tty_ldisc.c]

gemini-3.1-pro-preview

							input: 38534
							output: 38
							thoughts: 28
						

**A Moment of Clarification on `tty_buffer_flush` Parameters**

Hmm, I need to reconfirm the signature of `tty_buffer_flush`. My recollection is that it expects both the `tty` structure and the `ld` (line discipline) structure as arguments. Before proceeding, I'll quickly consult the source code or documentation to verify this detail. It's crucial to have this precise understanding to ensure I'm invoking the function correctly within the broader context of tty buffer management.

map[ContextFile:drivers/tty/tty_buffer.c Name:tty_buffer_flush]

map[SourceCode: 218:	/**
 219:	 * tty_buffer_flush		-	flush full tty buffers
 220:	 * @tty: tty to flush
 221:	 * @ld: optional ldisc ptr (must be referenced)
 222:	 *
 223:	 * Flush all the buffers containing receive data. If @ld != %NULL, flush the
 224:	 * ldisc input buffer.
 225:	 *
 226:	 * Locking: takes buffer lock to ensure single-threaded flip buffer 'consumer'.
 227:	 */
 228:	void tty_buffer_flush(struct tty_struct *tty, struct tty_ldisc *ld)
 229:	{
 230:		struct tty_port *port = tty->port;
 231:		struct tty_bufhead *buf = &port->buf;
 232:		struct tty_buffer *next;
 233:	
 234:		atomic_inc(&buf->priority);
 235:	
 236:		mutex_lock(&buf->lock);
 237:		/* paired w/ release in __tty_buffer_request_room; ensures there are
 238:		 * no pending memory accesses to the freed buffer
 239:		 */
 240:		while ((next = smp_load_acquire(&buf->head->next)) != NULL) {
 241:			tty_buffer_free(port, buf->head);
 242:			buf->head = next;
 243:		}
 244:		buf->head->read = buf->head->commit;
 245:		buf->head->lookahead = buf->head->read;
 246:	
 247:		if (ld && ld->ops->flush_buffer)
 248:			ld->ops->flush_buffer(tty);
 249:	
 250:		atomic_dec(&buf->priority);
 251:		mutex_unlock(&buf->lock);
 252:	}
 SourceFile:drivers/tty/tty_buffer.c]

gemini-3.1-pro-preview

							input: 39146
							output: 36
							thoughts: 1286
						

**My Thought Process Unveiled**

Okay, so I'm trying to understand this sequence of operations and how lockdep is going to react. It all hinges on this `mutex_lock(&buf->lock)` call.

The core operations I'm considering are:
1.  Opening `/dev/ttyS0` and using `ioctl(fd, TCSETS, &term)`.
2.  Opening `/dev/ptmx`, getting a PTY (pseudo-terminal), writing to it to force a `flush_to_ldisc`, which in turn should lock something.
3.  Sending 'k' to `/proc/sysrq-trigger`.

Now, the immediate question that pops into my head is: Do these need to happen at *exactly* the same time, concurrently? My understanding of `lockdep` is that it builds a global dependency graph. So, as long as all these operations *occur* within the scope of lockdep's tracking, it should be able to build the graph and identify any cycles. The order, in terms of concurrent execution, might not be the primary issue for detection; the crucial part is that they all execute.

Let's trace how `lockdep` would build its graph, assuming a sequential execution for clarity:

*   **Bootstrapping:** At boot, it's established that `&port->mutex` leads to `console_lock`. This dependency is recorded.
*   **Step 1: `ioctl(TCSETS)` on `/dev/ttyS0`:** This operation first acquires `&tty->termios_rwsem` (which I note is subclass 0 for this specific case), and then it acquires `&port->mutex` (also subclass 0). `lockdep` registers this: `&tty->termios_rwsem` -> `&port->mutex`. Since `&port->mutex` -> `console_lock` is already known, `lockdep` now understands the path: `&tty->termios_rwsem` -> `&port->mutex` -> `console_lock`.
*   **Step 2: `echo k > /proc/sysrq-trigger`:** This action takes `console_lock` first, and then proceeds to lock `&buf->lock` (subclass 0). `lockdep` adds this to its graph: `console_lock` -> `&buf->lock`. Combining this with the previous path, `lockdep` now sees: `&tty->termios_rwsem` -> `&port->mutex` -> `console_lock` -> `&buf->lock`.
*   **Step 3: Writing to the PTY:** This is where the potential cycle emerges. The `flush_to_ldisc` function, triggered by the write to the PTY, first takes `&buf->lock` (subclass 0), and then attempts to acquire `&tty->termios_rwsem` (subclass 0). `lockdep` registers this: `&buf->lock` -> `&tty->termios_rwsem`.

And there it is! The sequence `&buf->lock` -> `&tty->termios_rwsem` perfectly closes the loop with the existing chain `&tty->termios_rwsem` -> ... -> `&buf->lock`. This is precisely why `lockdep` will flag a cycle.

A critical point I need to verify is whether the `&buf->lock` acquired in `vc_SAK` (which is triggered by `sysrq-trigger`) is indeed the *same lock class* as the `&buf->lock` used in `flush_to_ldisc` during the PTY write. My investigation confirms that `tty_buffer_init` is responsible for initializing these buffers, and crucially, it uses `mutex_init(&buf->lock)`. The `mutex_init` macro, as I understand it, uses `__FILE__` and `__LINE__` to create unique, static lock class keys. Since `mutex_init(&buf->lock)` resides within `tty_buffer_init` (specifically at `drivers/tty/tty_buffer.c:586`), all instances of `&buf->lock` initialized this way, whether they originate from a VT, a serial port, or a PTY, will belong to the *same lock class*. This is the fundamental reason lockdep is detecting this cycle.

Similarly, I'm checking the `&tty->termios_rwsem`. The `init_rwsem(&tty->termios_rwsem)` call happens in `alloc_tty_struct` (at `drivers/tty/tty_io.c:3115`). This implies all `&tty->termios_rwsem` instances initialized here should share the same lock class (subclass 0). However, I remember seeing something about PTYs being different. Ah, yes, `pty_common_install` actually *changes* the subclass for the *slave* PTY's `termios_rwsem` to `TTY_LOCK_SLAVE`. But the *master* PTY retains its subclass 0.

The key insight here is that when data is written to the slave PTY, it's ultimately processed by the master PTY's buffer, and `flush_to_ldisc` operates on the *master* PTY. This means the locks acquired will be `&buf->lock` (subclass 0) and `&tty->termios_rwsem` (subclass 0, from the master PTY). This exactly matches the lock class taken by `tty_set_termios` when operating on `/dev/ttyS0` (also subclass 0). This alignment is what completes the cycle detection.

So, I'm wondering if there's an alternative. What if I could use `/dev/ttyS0` for both Step 1 *and* Step 3? If I can send data *to* `/dev/ttyS0` in a way that triggers `flush_to_ldisc` on it, that would involve locking `&buf->lock` and `&tty->termios_rwsem` (subclass 0). The question then becomes: can I reliably send data to `/dev/ttyS0`? If it's configured for loopback, then yes. But in a typical setup, that's not the case.

However, the PTY approach for Step 3 is still robust. `lockdep` cares about *lock classes*, not the specific object instances. Since the lock classes for `&buf->lock` and `&tty->termios_rwsem` are identical for a PTY master and a serial port, using a PTY for Step 3 to trigger the locks is a perfectly valid and reliable method to demonstrate the cycle.

Finally, I'm double-checking the mechanism for Step 2, the `echo k > /proc/sysrq-trigger`. Yes, `sysrq_handle_SAK` is indeed registered for the 'k' key. I'm also considering if `sysrq` needs to be explicitly enabled. Syzkaller typically runs with `kernel.sysrq = 1`, so this should be fine. But if it weren't, I'm recalling if there's an alternative way to trigger `vc_SAK`, perhaps via `ioctl(fd, TIOCLINUX, &val)`? I need to revisit `tioclinux` to be sure; my initial check didn't show SAK functionality there.

map[ContextFile:drivers/tty/vt/vt.c Name:tioclinux]

map[SourceCode:3561:	int tioclinux(struct tty_struct *tty, unsigned long arg)
3562:	{
3563:		char type, data;
3564:		char __user *p = (char __user *)arg;
3565:		void __user *param_aligned32 = (u32 __user *)arg + 1;
3566:		void __user *param = (void __user *)arg + 1;
3567:		int lines;
3568:		int ret;
3569:	
3570:		if (current->signal->tty != tty && !capable(CAP_SYS_ADMIN))
3571:			return -EPERM;
3572:		if (get_user(type, p))
3573:			return -EFAULT;
3574:		ret = 0;
3575:	
3576:		switch (type) {
3577:		case TIOCL_SETSEL:
3578:			return set_selection_user(param, tty);
3579:		case TIOCL_PASTESEL:
3580:			if (!capable(CAP_SYS_ADMIN))
3581:				return -EPERM;
3582:			return paste_selection(tty);
3583:		case TIOCL_UNBLANKSCREEN:
3584:			scoped_guard(console_lock)
3585:				unblank_screen();
3586:			break;
3587:		case TIOCL_SELLOADLUT:
3588:			if (!capable(CAP_SYS_ADMIN))
3589:				return -EPERM;
3590:			return sel_loadlut(param_aligned32);
3591:		case TIOCL_GETSHIFTSTATE:
3592:			/*
3593:			 * Make it possible to react to Shift+Mousebutton. Note that
3594:			 * 'shift_state' is an undocumented kernel-internal variable;
3595:			 * programs not closely related to the kernel should not use
3596:			 * this.
3597:			 */
3598:			data = vt_get_shift_state();
3599:			return put_user(data, p);
3600:		case TIOCL_GETMOUSEREPORTING:
3601:			scoped_guard(console_lock)	/* May be overkill */
3602:				data = mouse_reporting();
3603:			return put_user(data, p);
3604:		case TIOCL_SETVESABLANK:
3605:			return set_vesa_blanking(param);
3606:		case TIOCL_GETKMSGREDIRECT:
3607:			data = vt_get_kmsg_redirect();
3608:			return put_user(data, p);
3609:		case TIOCL_SETKMSGREDIRECT:
3610:			if (!capable(CAP_SYS_ADMIN))
3611:				return -EPERM;
3612:	
3613:			if (get_user(data, p+1))
3614:				return -EFAULT;
3615:	
3616:			vt_kmsg_redirect(data);
3617:	
3618:			break;
3619:		case TIOCL_GETFGCONSOLE:
3620:			/*
3621:			 * No locking needed as this is a transiently correct return
3622:			 * anyway if the caller hasn't disabled switching.
3623:			 */
3624:			return fg_console;
3625:		case TIOCL_SCROLLCONSOLE:
3626:			if (get_user(lines, (s32 __user *)param_aligned32))
3627:				return -EFAULT;
3628:	
3629:			/*
3630:			 * Needs the console lock here. Note that lots of other calls
3631:			 * need fixing before the lock is actually useful!
3632:			 */
3633:			scoped_guard(console_lock)
3634:				scrollfront(vc_cons[fg_console].d, lines);
3635:			break;
3636:		case TIOCL_BLANKSCREEN:	/* until explicitly unblanked, not only poked */
3637:			scoped_guard(console_lock) {
3638:				ignore_poke = 1;
3639:				do_blank_screen(0);
3640:			}
3641:			break;
3642:		case TIOCL_BLANKEDSCREEN:
3643:			return console_blanked;
3644:		case TIOCL_GETBRACKETEDPASTE:
3645:			return get_bracketed_paste(tty);
3646:		default:
3647:			return -EINVAL;
3648:		}
3649:	
3650:		return ret;
3651:	}
 SourceFile:drivers/tty/vt/vt.c]

gemini-3.1-pro-preview

							input: 41805
							output: 38
							thoughts: 19
						

**A Deep Dive into Security and Kernel Interfaces**

So, I've been sifting through some code, trying to get a handle on the security implications and how different interfaces are being used. My initial thought was about SAK, the Secure Attention Key, and I confirmed that it's definitely not present in `tioclinux`. This is important because SAK is a critical mechanism for secure console access, and its absence in this specific interface means I need to consider alternative security measures or understand the intended use case where SAK isn't a requirement.

This then naturally led me to think about other related security signals and kernel events. My next question was, "What about `KDSIGACCEPT`?" This signal is tied to the kernel's handling of signals, specifically when a process is allowed to accept signals. I'm wondering if this signal plays a role in the security context I'm examining, or if it's more of a general process management feature that might indirectly impact security. Understanding how `KDSIGACCEPT` is implemented and used could reveal potential vulnerabilities or, conversely, provide mechanisms for more robust security configurations within the kernel's signal handling. I'm trying to piece together the overall security posture by looking at these specific, granular components.

map[ContextFile:drivers/tty/vt/vt_ioctl.c Name:vt_ioctl]

map[SourceCode: 723:	/*
 724:	 * We handle the console-specific ioctl's here.  We allow the
 725:	 * capability to modify any console, not just the fg_console.
 726:	 */
 727:	int vt_ioctl(struct tty_struct *tty,
 728:		     unsigned int cmd, unsigned long arg)
 729:	{
 730:		struct vc_data *vc = tty->driver_data;
 731:		void __user *up = (void __user *)arg;
 732:		int i, perm;
 733:		int ret;
 734:	
 735:		/*
 736:		 * To have permissions to do most of the vt ioctls, we either have
 737:		 * to be the owner of the tty, or have CAP_SYS_TTY_CONFIG.
 738:		 */
 739:		perm = 0;
 740:		if (current->signal->tty == tty || capable(CAP_SYS_TTY_CONFIG))
 741:			perm = 1;
 742:	
 743:		ret = vt_k_ioctl(tty, cmd, arg, perm);
 744:		if (ret != -ENOIOCTLCMD)
 745:			return ret;
 746:	
 747:		ret = vt_io_ioctl(vc, cmd, up, perm);
 748:		if (ret != -ENOIOCTLCMD)
 749:			return ret;
 750:	
 751:		switch (cmd) {
 752:		case TIOCLINUX:
 753:			return tioclinux(tty, arg);
 754:		case VT_SETMODE:
 755:		{
 756:			struct vt_mode tmp;
 757:	
 758:			if (!perm)
 759:				return -EPERM;
 760:			if (copy_from_user(&tmp, up, sizeof(struct vt_mode)))
 761:				return -EFAULT;
 762:			if (tmp.mode != VT_AUTO && tmp.mode != VT_PROCESS)
 763:				return -EINVAL;
 764:	
 765:			guard(console_lock)();
 766:			vc->vt_mode = tmp;
 767:			/* the frsig is ignored, so we set it to 0 */
 768:			vc->vt_mode.frsig = 0;
 769:			put_pid(vc->vt_pid);
 770:			vc->vt_pid = get_pid(task_pid(current));
 771:			/* no switch is required -- saw@shade.msu.ru */
 772:			vc->vt_newvt = -1;
 773:			break;
 774:		}
 775:	
 776:		case VT_GETMODE:
 777:		{
 778:			struct vt_mode tmp;
 779:			int rc;
 780:	
 781:			scoped_guard(console_lock)
 782:				memcpy(&tmp, &vc->vt_mode, sizeof(struct vt_mode));
 783:	
 784:			rc = copy_to_user(up, &tmp, sizeof(struct vt_mode));
 785:			if (rc)
 786:				return -EFAULT;
 787:			break;
 788:		}
 789:	
 790:		/*
 791:		 * Returns global vt state. Note that VT 0 is always open, since
 792:		 * it's an alias for the current VT, and people can't use it here.
 793:		 * We cannot return state for more than 16 VTs, since v_state is short.
 794:		 */
 795:		case VT_GETSTATE:
 796:		{
 797:			struct vt_stat __user *vtstat = up;
 798:			unsigned short state, mask;
 799:	
 800:			if (put_user(fg_console + 1, &vtstat->v_active))
 801:				return -EFAULT;
 802:	
 803:			state = 1;	/* /dev/tty0 is always open */
 804:			scoped_guard(console_lock) /* required by vt_in_use() */
 805:				for (i = 0, mask = 2; i < MAX_NR_CONSOLES && mask; ++i, mask <<= 1)
 806:					if (vt_in_use(i))
 807:						state |= mask;
 808:			return put_user(state, &vtstat->v_state);
 809:		}
 810:	
 811:		/*
 812:		 * Returns the first available (non-opened) console.
 813:		 */
 814:		case VT_OPENQRY:
 815:			scoped_guard(console_lock) /* required by vt_in_use() */
 816:				for (i = 0; i < MAX_NR_CONSOLES; ++i)
 817:					if (!vt_in_use(i))
 818:						break;
 819:			i = i < MAX_NR_CONSOLES ? (i+1) : -1;
 820:			return put_user(i, (int __user *)arg);
 821:	
 822:		/*
 823:		 * ioctl(fd, VT_ACTIVATE, num) will cause us to switch to vt # num,
 824:		 * with num >= 1 (switches to vt 0, our console, are not allowed, just
 825:		 * to preserve sanity).
 826:		 */
 827:		case VT_ACTIVATE:
 828:			if (!perm)
 829:				return -EPERM;
 830:			if (arg == 0 || arg > MAX_NR_CONSOLES)
 831:				return -ENXIO;
 832:	
 833:			arg--;
 834:			arg = array_index_nospec(arg, MAX_NR_CONSOLES);
 835:			scoped_guard(console_lock) {
 836:				ret = vc_allocate(arg);
 837:				if (ret)
 838:					return ret;
 839:			}
 840:			set_console(arg);
 841:			break;
 842:	
 843:		case VT_SETACTIVATE:
 844:			if (!perm)
 845:				return -EPERM;
 846:	
 847:			return vt_setactivate(up);
 848:	
 849:		/*
 850:		 * wait until the specified VT has been activated
 851:		 */
 852:		case VT_WAITACTIVE:
 853:			if (!perm)
 854:				return -EPERM;
 855:			if (arg == 0 || arg > MAX_NR_CONSOLES)
 856:				return -ENXIO;
 857:			return vt_waitactive(arg);
 858:	
 859:		/*
 860:		 * If a vt is under process control, the kernel will not switch to it
 861:		 * immediately, but postpone the operation until the process calls this
 862:		 * ioctl, allowing the switch to complete.
 863:		 *
 864:		 * According to the X sources this is the behavior:
 865:		 *	0:	pending switch-from not OK
 866:		 *	1:	pending switch-from OK
 867:		 *	2:	completed switch-to OK
 868:		 */
 869:		case VT_RELDISP:
 870:		{
 871:			if (!perm)
 872:				return -EPERM;
 873:	
 874:			guard(console_lock)();
 875:			return vt_reldisp(vc, arg);
 876:		}
 877:	
 878:		 /*
 879:		  * Disallocate memory associated to VT (but leave VT1)
 880:		  */
 881:		 case VT_DISALLOCATE:
 882:			if (arg > MAX_NR_CONSOLES)
 883:				return -ENXIO;
 884:	
 885:			if (arg == 0) {
 886:				vt_disallocate_all();
 887:				break;
 888:			}
 889:	
 890:			arg = array_index_nospec(arg - 1, MAX_NR_CONSOLES);
 891:			return vt_disallocate(arg);
 892:	
 893:		case VT_RESIZE:
 894:		{
 895:			struct vt_sizes __user *vtsizes = up;
 896:			struct vc_data *vc;
 897:			ushort ll,cc;
 898:	
 899:			if (!perm)
 900:				return -EPERM;
 901:			if (get_user(ll, &vtsizes->v_rows) ||
 902:			    get_user(cc, &vtsizes->v_cols))
 903:				return -EFAULT;
 904:	
 905:			guard(console_lock)();
 906:			for (i = 0; i < MAX_NR_CONSOLES; i++) {
 907:				vc = vc_cons[i].d;
 908:	
 909:				if (vc) {
 910:					/* FIXME: review v tty lock */
 911:					ret = __vc_resize(vc_cons[i].d, cc, ll, true);
 912:					if (ret)
 913:						return ret;
 914:				}
 915:			}
 916:			break;
 917:		}
 918:	
 919:		case VT_RESIZEX:
 920:			if (!perm)
 921:				return -EPERM;
 922:	
 923:			return vt_resizex(vc, up);
 924:	
 925:		case VT_LOCKSWITCH:
 926:			if (!capable(CAP_SYS_TTY_CONFIG))
 927:				return -EPERM;
 928:			vt_dont_switch = true;
 929:			break;
 930:		case VT_UNLOCKSWITCH:
 931:			if (!capable(CAP_SYS_TTY_CONFIG))
 932:				return -EPERM;
 933:			vt_dont_switch = false;
 934:			break;
 935:		case VT_GETHIFONTMASK:
 936:			return put_user(vc->vc_hi_font_mask,
 937:						(unsigned short __user *)arg);
 938:		case VT_WAITEVENT:
 939:			return vt_event_wait_ioctl((struct vt_event __user *)arg);
 940:	
 941:		case VT_GETCONSIZECSRPOS:
 942:		{
 943:			struct vt_consizecsrpos concsr;
 944:	
 945:			console_lock();
 946:			concsr.con_cols = vc->vc_cols;
 947:			concsr.con_rows = vc->vc_rows;
 948:			concsr.csr_col = vc->state.x;
 949:			concsr.csr_row = vc->state.y;
 950:			console_unlock();
 951:			if (copy_to_user(up, &concsr, sizeof(concsr)))
 952:				return -EFAULT;
 953:			return 0;
 954:		}
 955:	
 956:		default:
 957:			return -ENOIOCTLCMD;
 958:		}
 959:	
 960:		return 0;
 961:	}
 SourceFile:drivers/tty/vt/vt_ioctl.c]

gemini-3.1-pro-preview

							input: 45223
							output: 40
							thoughts: 26
						

**My Thought Process on `KDSIGACCEPT`'s Location**

My immediate thought is to pinpoint the exact location of `KDSIGACCEPT` within the system's codebase. Specifically, I'm trying to recall whether it resides within the `vt_io_ioctl` function or the `vt_k_ioctl` function. This distinction is crucial for understanding the context in which this ioctl signal handling mechanism operates. Is it part of the general virtual terminal I/O operations, or is it more specifically tied to kernel-level virtual terminal interactions? My mental model is actively searching for this detail to correctly contextualize the ioctl's purpose and its relationship with the underlying virtual terminal driver.

map[ContextFile:drivers/tty/vt/vt_ioctl.c Name:vt_k_ioctl]

map[SourceCode: 283:	static int vt_k_ioctl(struct tty_struct *tty, unsigned int cmd,
 284:			unsigned long arg, bool perm)
 285:	{
 286:		struct vc_data *vc = tty->driver_data;
 287:		void __user *up = (void __user *)arg;
 288:		unsigned int console = vc->vc_num;
 289:		int ret;
 290:	
 291:		switch (cmd) {
 292:		case KIOCSOUND:
 293:			if (!perm)
 294:				return -EPERM;
 295:			/*
 296:			 * The use of PIT_TICK_RATE is historic, it used to be
 297:			 * the platform-dependent CLOCK_TICK_RATE between 2.6.12
 298:			 * and 2.6.36, which was a minor but unfortunate ABI
 299:			 * change. kd_mksound is locked by the input layer.
 300:			 */
 301:			if (arg)
 302:				arg = PIT_TICK_RATE / arg;
 303:			kd_mksound(arg, 0);
 304:			break;
 305:	
 306:		case KDMKTONE:
 307:			if (!perm)
 308:				return -EPERM;
 309:		{
 310:			unsigned int ticks, count;
 311:	
 312:			/*
 313:			 * Generate the tone for the appropriate number of ticks.
 314:			 * If the time is zero, turn off sound ourselves.
 315:			 */
 316:			ticks = msecs_to_jiffies((arg >> 16) & 0xffff);
 317:			count = ticks ? (arg & 0xffff) : 0;
 318:			if (count)
 319:				count = PIT_TICK_RATE / count;
 320:			kd_mksound(count, ticks);
 321:			break;
 322:		}
 323:	
 324:		case KDGKBTYPE:
 325:			/*
 326:			 * this is naïve.
 327:			 */
 328:			return put_user(KB_101, (char __user *)arg);
 329:	
 330:			/*
 331:			 * These cannot be implemented on any machine that implements
 332:			 * ioperm() in user level (such as Alpha PCs) or not at all.
 333:			 *
 334:			 * XXX: you should never use these, just call ioperm directly..
 335:			 */
 336:	#ifdef CONFIG_X86
 337:		case KDADDIO:
 338:		case KDDELIO:
 339:			/*
 340:			 * KDADDIO and KDDELIO may be able to add ports beyond what
 341:			 * we reject here, but to be safe...
 342:			 *
 343:			 * These are locked internally via sys_ioperm
 344:			 */
 345:			if (arg < GPFIRST || arg > GPLAST)
 346:				return -EINVAL;
 347:	
 348:			return ksys_ioperm(arg, 1, (cmd == KDADDIO)) ? -ENXIO : 0;
 349:	
 350:		case KDENABIO:
 351:		case KDDISABIO:
 352:			return ksys_ioperm(GPFIRST, GPNUM,
 353:					  (cmd == KDENABIO)) ? -ENXIO : 0;
 354:	#endif
 355:	
 356:		/* Linux m68k/i386 interface for setting the keyboard delay/repeat rate */
 357:	
 358:		case KDKBDREP:
 359:		{
 360:			struct kbd_repeat kbrep;
 361:	
 362:			if (!capable(CAP_SYS_TTY_CONFIG))
 363:				return -EPERM;
 364:	
 365:			if (copy_from_user(&kbrep, up, sizeof(struct kbd_repeat)))
 366:				return -EFAULT;
 367:	
 368:			ret = kbd_rate(&kbrep);
 369:			if (ret)
 370:				return ret;
 371:			if (copy_to_user(up, &kbrep, sizeof(struct kbd_repeat)))
 372:				return -EFAULT;
 373:			break;
 374:		}
 375:	
 376:		case KDSETMODE: {
 377:			if (!perm)
 378:				return -EPERM;
 379:	
 380:			guard(console_lock)();
 381:			return vt_kdsetmode(vc, arg);
 382:		}
 383:		case KDGETMODE:
 384:			return put_user(vc->vc_mode, (int __user *)arg);
 385:	
 386:		case KDMAPDISP:
 387:		case KDUNMAPDISP:
 388:			/*
 389:			 * these work like a combination of mmap and KDENABIO.
 390:			 * this could be easily finished.
 391:			 */
 392:			return -EINVAL;
 393:	
 394:		case KDSKBMODE:
 395:			if (!perm)
 396:				return -EPERM;
 397:			ret = vt_do_kdskbmode(console, arg);
 398:			if (ret)
 399:				return ret;
 400:			tty_ldisc_flush(tty);
 401:			break;
 402:	
 403:		case KDGKBMODE:
 404:			return put_user(vt_do_kdgkbmode(console), (int __user *)arg);
 405:	
 406:		/* this could be folded into KDSKBMODE, but for compatibility
 407:		   reasons it is not so easy to fold KDGKBMETA into KDGKBMODE */
 408:		case KDSKBMETA:
 409:			return vt_do_kdskbmeta(console, arg);
 410:	
 411:		case KDGKBMETA:
 412:			/* FIXME: should review whether this is worth locking */
 413:			return put_user(vt_do_kdgkbmeta(console), (int __user *)arg);
 414:	
 415:		case KDGETKEYCODE:
 416:		case KDSETKEYCODE:
 417:			if(!capable(CAP_SYS_TTY_CONFIG))
 418:				perm = 0;
 419:			return vt_do_kbkeycode_ioctl(cmd, up, perm);
 420:	
 421:		case KDGKBENT:
 422:		case KDSKBENT:
 423:			return vt_do_kdsk_ioctl(cmd, up, perm, console);
 424:	
 425:		case KDGKBSENT:
 426:		case KDSKBSENT:
 427:			return vt_do_kdgkb_ioctl(cmd, up, perm);
 428:	
 429:		/* Diacritical processing. Handled in keyboard.c as it has
 430:		   to operate on the keyboard locks and structures */
 431:		case KDGKBDIACR:
 432:		case KDGKBDIACRUC:
 433:		case KDSKBDIACR:
 434:		case KDSKBDIACRUC:
 435:			return vt_do_diacrit(cmd, up, perm);
 436:	
 437:		/* the ioctls below read/set the flags usually shown in the leds */
 438:		/* don't use them - they will go away without warning */
 439:		case KDGKBLED:
 440:		case KDSKBLED:
 441:		case KDGETLED:
 442:		case KDSETLED:
 443:			return vt_do_kdskled(console, cmd, arg, perm);
 444:	
 445:		/*
 446:		 * A process can indicate its willingness to accept signals
 447:		 * generated by pressing an appropriate key combination.
 448:		 * Thus, one can have a daemon that e.g. spawns a new console
 449:		 * upon a keypress and then changes to it.
 450:		 * See also the kbrequest field of inittab(5).
 451:		 */
 452:		case KDSIGACCEPT:
 453:			if (!perm || !capable(CAP_KILL))
 454:				return -EPERM;
 455:			if (!valid_signal(arg) || arg < 1 || arg == SIGKILL)
 456:				return -EINVAL;
 457:	
 458:			spin_lock_irq(&vt_spawn_con.lock);
 459:			put_pid(vt_spawn_con.pid);
 460:			vt_spawn_con.pid = get_pid(task_pid(current));
 461:			vt_spawn_con.sig = arg;
 462:			spin_unlock_irq(&vt_spawn_con.lock);
 463:			break;
 464:	
 465:		case KDFONTOP: {
 466:			struct console_font_op op;
 467:	
 468:			if (copy_from_user(&op, up, sizeof(op)))
 469:				return -EFAULT;
 470:			if (!perm && op.op != KD_FONT_OP_GET)
 471:				return -EPERM;
 472:			ret = con_font_op(vc, &op);
 473:			if (ret)
 474:				return ret;
 475:			if (copy_to_user(up, &op, sizeof(op)))
 476:				return -EFAULT;
 477:			break;
 478:		}
 479:	
 480:		default:
 481:			return -ENOIOCTLCMD;
 482:		}
 483:	
 484:		return 0;
 485:	}
 SourceFile:drivers/tty/vt/vt_ioctl.c]

gemini-3.1-pro-preview

							input: 48212
							output: 41
							thoughts: 162
						

**A Deep Dive into Console Driver Behavior**

My initial thought process is sparked by observing the `KDSKBMODE` ioctl call within the `vt_k_ioctl` function. I immediately notice that it invokes `tty_ldisc_flush(tty)`. This is a critical observation, as `tty_ldisc_flush` is responsible for clearing out the termios line discipline buffer. My immediate question is about the locking mechanisms surrounding this operation.

Specifically, I'm concerned about whether `KDSKBMODE` itself acquires the `console_lock`. My quick perusal of `vt_k_ioctl` suggests that `KDSKBMODE` *does not* directly take the `console_lock`. This absence of explicit locking by the ioctl call itself is a red flag.

This leads me to the next logical step in my investigation: does the function called by `KDSKBMODE`, namely `vt_do_kdskbmode`, acquire the `console_lock`? If `KDSKBMODE` doesn't lock, the responsibility for protecting the shared console data structures must fall upon `vt_do_kdskbmode`. Therefore, my next action is to examine the implementation of `vt_do_kdskbmode` to ascertain its locking behavior.

map[ContextFile:drivers/tty/vt/keyboard.c Name:vt_do_kdskbmode]

map[SourceCode:1867:	/**
1868:	 *	vt_do_kdskbmode		-	set keyboard mode ioctl
1869:	 *	@console: the console to use
1870:	 *	@arg: the requested mode
1871:	 *
1872:	 *	Update the keyboard mode bits while holding the correct locks.
1873:	 *	Return 0 for success or an error code.
1874:	 */
1875:	int vt_do_kdskbmode(unsigned int console, unsigned int arg)
1876:	{
1877:		struct kbd_struct *kb = &kbd_table[console];
1878:	
1879:		guard(spinlock_irqsave)(&kbd_event_lock);
1880:		switch(arg) {
1881:		case K_RAW:
1882:			kb->kbdmode = VC_RAW;
1883:			return 0;
1884:		case K_MEDIUMRAW:
1885:			kb->kbdmode = VC_MEDIUMRAW;
1886:			return 0;
1887:		case K_XLATE:
1888:			kb->kbdmode = VC_XLATE;
1889:			do_compute_shiftstate();
1890:			return 0;
1891:		case K_UNICODE:
1892:			kb->kbdmode = VC_UNICODE;
1893:			do_compute_shiftstate();
1894:			return 0;
1895:		case K_OFF:
1896:			kb->kbdmode = VC_OFF;
1897:			return 0;
1898:		default:
1899:			return -EINVAL;
1900:		}
1901:	}
 SourceFile:drivers/tty/vt/keyboard.c]

gemini-3.1-pro-preview

							input: 48907
							output: 1059
							thoughts: 2622
						

**My Thought Process for Reproducing a Circular Locking Dependency**

Alright, let's break down how I've arrived at this reproduction strategy. My goal here is to trigger a specific circular locking dependency that I've identified in the kernel, and I need to explain my reasoning clearly, assuming you're as familiar with kernel internals as I am.

First off, I’ve been looking at the interactions involving `console_lock`, `&buf->lock`, `&port->mutex`, and `&tty->termios_rwsem`. My initial thought was to check if `KDSKBMODE` or `vc_SAK` directly acquire these locks in sequence. I quickly determined that `KDSKBMODE` doesn’t involve `console_lock` in the way I was expecting.

However, when I examined the `vc_SAK` function, I saw it clearly takes `console_lock`.

```c
	void vc_SAK(struct work_struct *work)
	{
		struct vc *vc_con =
			container_of(work, struct vc, SAK_work);
		struct vc_data *vc;
		struct tty_struct *tty;

		guard(console_lock)(); // Ah, here it is!
		vc = vc_con->d;
		if (!vc)
			return;

		/* FIXME: review tty ref counting */
		tty = vc->port.tty;
		/* SAK should also work in all raw modes and reset them properly. */
		if (tty)
			__do_SAK(tty); // This path is key
		reset_vc(vc);
	}
```

Crucially, the `__do_SAK` call within `vc_SAK` eventually leads to `tty_ldisc_flush` and then `tty_buffer_flush`. It's `tty_buffer_flush` that acquires `&buf->lock`. So, this establishes a path: `console_lock` -> `&buf->lock`.

Now, I need to figure out how to connect the other pieces of the puzzle to form a cycle. My next question was: "Are there other ways to trigger `vc_SAK`?" I know that `fn_SAK` in `drivers/tty/vt/keyboard.c` is called from the keyboard interrupt handler, meaning a physical SAK key press would also trigger it. But for a programmatic reproduction, writing to `/proc/sysrq-trigger` with `k` is the most straightforward method. This is how I’ll trigger the `console_lock` -> `&buf->lock` transition.

The remaining locks are `&tty->termios_rwsem` and `&port->mutex`. I need to see how they relate to the others. I know that operations on serial ports, specifically `uart_set_termios`, acquire `&port->mutex`. Furthermore, `tty_set_termios` (which calls `uart_set_termios`) operates while holding `&tty->termios_rwsem`. This gives me a link: `&tty->termios_rwsem` -> `&port->mutex`.

The final link I need is `&port->mutex` to `console_lock`. My understanding is that during kernel boot, serial console devices are registered, and this registration process involves acquiring `console_lock` under certain conditions related to the serial port's mutex. The lockdep report confirms this; it shows `console_lock` being acquired, and its dependency chain includes `uart_configure_port`, which operates on serial ports. Therefore, I can confidently say that `&port->mutex` -> `console_lock` is a dependency that is *already recorded* by lockdep during boot. I don’t need to actively trigger this specific transition myself; it's implicitly present.

Now, let's assemble the full cycle:
1.  I need to acquire `&tty->termios_rwsem` and then `&port->mutex`. The easiest way to do this is by opening a serial port (like `/dev/ttyS0`) and performing an `ioctl` with `TCSETS` (or `TCGETS` followed by `TCSETS`). This establishes `&tty->termios_rwsem` -> `&port->mutex`.
2.  I know the system already records `&port->mutex` -> `console_lock`.
3.  I can then trigger `console_lock` -> `&buf->lock` by writing `k` to `/proc/sysrq-trigger`.
4.  Finally, I need to acquire `&buf->lock` and then transition to `&tty->termios_rwsem`. This is achieved by writing to a pseudo-terminal (pty). When I write to the slave pty, it triggers `flush_to_ldisc` on the master pty. `flush_to_ldisc` acquires `&buf->lock` and then subsequently tries to acquire `&tty->termios_rwsem` (specifically, it interacts with the TTY's line discipline, which is tied to the termios settings). This creates the path `&buf->lock` -> `&tty->termios_rwsem`.

Putting it all together, the complete circular dependency chain I've identified is:
`&tty->termios_rwsem` -> `&port->mutex` -> `console_lock` -> `&buf->lock` -> `&tty->termios_rwsem`.

To reproduce this for lockdep, I need to ensure these transitions happen in a way that lockdep can observe them. My initial thought was to use threads to run these operations concurrently. However, lockdep's dependency tracking is global. It doesn't require an actual deadlock to occur; it just needs to see the *potential* for a deadlock by observing the lock acquisition order. Therefore, executing these steps sequentially is perfectly sufficient. In fact, sequential execution is *better* because it avoids any actual system instability while still allowing lockdep to detect the circular dependency.

Here’s the refined reproduction strategy:

1.  **Establish `&tty->termios_rwsem` -> `&port->mutex`:** Open a serial port (e.g., `/dev/ttyS0`) and call `ioctl(fd, TCSETS, &term)`. This ensures the relevant termios rwsem is held, and then the serial port mutex is acquired.
2.  **Establish `console_lock` -> `&buf->lock`:** Write `k` to `/proc/sysrq-trigger`. This schedules the `vc_SAK` work item, which will acquire `console_lock` and then, through its call to `__do_SAK`, eventually acquire `&buf->lock`. I'll add a small `usleep` here to give the work item time to be processed.
3.  **Establish `&buf->lock` -> `&tty->termios_rwsem`:** Open `/dev/ptmx`, get the slave pty, and write a byte to it. This will cause `flush_to_ldisc` on the master pty, acquiring `&buf->lock` and then `&tty->termios_rwsem`. Again, a small `usleep` is added for the work to complete.

The dependency `&port->mutex` -> `console_lock` is already recorded by lockdep during boot, so I don't need to explicitly trigger it. By executing these three sequential steps, I will trigger the necessary lock acquisitions in an order that exposes the full circular dependency to lockdep, causing it to issue the warning. I've verified this logic against the lockdep report, and it aligns perfectly with the observed lock acquisition paths.

Regarding availability of resources like `/dev/ttyS0`: syzkaller tests typically run as root, so permissions are not an issue. Even if a specific `/dev/ttyS0` isn't available, any serial port managed by `serial_core` will have its `uart_port` mutex initialized in a way that contributes to the `&port->mutex` -> `console_lock` dependency, as all these mutexes share the same lock class. So, any available serial port will suffice.

The C program I've drafted directly implements these sequential steps. It's designed to be simple, clear, and to trigger the specific lock order necessary for lockdep to detect the cycle.

map[OracleFeedback:]

map[CurrentReproStrategy:To reproduce this circular locking dependency warning, we need to trigger the lock dependencies that form the cycle. Lockdep tracks dependencies between lock classes globally, so we don't need to cause an actual deadlock; we just need to execute the code paths that take these locks in the required order sequentially.

### Lock Dependency Analysis

The cycle consists of 4 lock classes:
1. `&port->mutex` -> `console_lock`: This dependency is **already recorded during boot** when the kernel registers the serial console (`serial8250_init` -> `uart_configure_port`). We don't need to trigger it manually.
2. `&tty->termios_rwsem` -> `&port->mutex`: This is triggered when setting termios on a serial port. `tty_set_termios` takes `&tty->termios_rwsem` (write) and then calls `uart_set_termios` which takes `&port->mutex`.
3. `console_lock` -> `&buf->lock`: This is triggered by the Secure Attention Key (SAK) on a virtual console. `vc_SAK` takes `console_lock` and then calls `__do_SAK` -> `tty_ldisc_flush` -> `tty_buffer_flush` which takes `&buf->lock`.
4. `&buf->lock` -> `&tty->termios_rwsem`: This is triggered by the normal tty receive path. `flush_to_ldisc` takes `&buf->lock` and then calls `n_tty_receive_buf_common` which takes `&tty->termios_rwsem` (read).

### Reproduction Strategy

We can write a minimal C program that sequentially triggers the remaining 3 dependencies:
1. **Open a serial port** (e.g., `/dev/ttyS0`) and call `ioctl(fd, TCSETS, &term)` to record `&tty->termios_rwsem` -> `&port->mutex`.
2. **Write 'k' to `/proc/sysrq-trigger`** to simulate a SAK keypress. This schedules `vc_SAK` work, recording `console_lock` -> `&buf->lock`.
3. **Open a PTY pair** and write to the slave PTY. This queues data to the master PTY and schedules `flush_to_ldisc`, recording `&buf->lock` -> `&tty->termios_rwsem`.

Once the last dependency is recorded, lockdep will detect the cycle and emit the warning.

### Minimal C Reproducer

```c
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <stdlib.h>

int main(void) {
    // 1. Trigger: &tty->termios_rwsem -> &port->mutex
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial >= 0) {
        struct termios term;
        if (ioctl(fd_serial, TCGETS, &term) == 0) {
            ioctl(fd_serial, TCSETS, &term);
        }
        close(fd_serial);
    }

    // 2. Trigger: console_lock -> &buf->lock
    int fd_sysrq = open("/proc/sysrq-trigger", O_WRONLY);
    if (fd_sysrq >= 0) {
        write(fd_sysrq, "k", 1);
        close(fd_sysrq);
        // Wait a bit for the vc_SAK workqueue to execute
        usleep(100000);
    }

    // 3. Trigger: &buf->lock -> &tty->termios_rwsem
    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx >= 0) {
        grantpt(ptmx);
        unlockpt(ptmx);
        char *pts_name = ptsname(ptmx);
        if (pts_name) {
            int pts = open(pts_name, O_RDWR | O_NOCTTY);
            if (pts >= 0) {
                // Writing to the slave PTY triggers flush_to_ldisc on the master PTY
                write(pts, "a", 1);
                // Wait a bit for the flush_to_ldisc workqueue to execute
                usleep(100000);
                close(pts);
            }
        }
        close(ptmx);
    }

    return 0;
}
```]

best-expensive

map[IsProbe:true RawCandidateReproC:#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>

int main(void) {
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) {
        printf("[-] Failed to open /dev/ttyS0: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/ttyS0.\n");
    close(fd_serial);

    int fd_sysrq = open("/proc/sysrq-trigger", O_WRONLY);
    if (fd_sysrq < 0) {
        printf("[-] Failed to open /proc/sysrq-trigger: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /proc/sysrq-trigger.\n");
    close(fd_sysrq);

    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx < 0) {
        printf("[-] Failed to open /dev/ptmx: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/ptmx.\n");
    close(ptmx);

    printf("[+] All probes successful.\n");
    return 0;
}
]

You are a security researcher with deep Linux kernel background.
Your goal is to generate a minimal, standalone C program for the strictly defensive
purpose of verifying a bugfix in an isolated environment.

To ensure that we can diagnose why a program might fail to run on the test environment,
you MUST include detailed logging and error checking in the generated C program:
1. Use 'printf(...)' for all progress messages and error logs.
2. Every system call (e.g., socket, bind, listen, connect, ioctl, send) must check for a failure return value.
3. If a call fails, it must print a specific error message including the function name
   and the error string (use strerror(errno)), and then exit with a non-zero status.
4. The program must print a message after every successful major step.
5. Generate code that follows this pattern for all operations:
    int res = do_something();
    if (res < 0) {
        printf("[-] Failed to do_something: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] do_something successful.\n");
6. The compilation and development environment (including compilers, build
   systems, makefiles, and kernel build/header directories) is NOT available
   on the target test VM guest. Do NOT check for, build, or reference any
   compilation tools, build files, or kernel development directories.
7. Do NOT execute shell commands or run external binaries (e.g. by using
   functions like 'system()', 'popen()', or the 'exec' family such as
   'execve()'). All environment checks, capability probings, and reproduction
   steps must be performed directly using standard Linux system calls (such
   as 'open', 'socket', 'ioctl', 'stat', etc.).
8. When reproducing asynchronous kernel timeouts or warnings, always
   include a sufficient delay (using sleep or similar) after deleting
   or unregistering the device to allow the kernel's asynchronous
   timeout to trigger before program exit.


=== PHASE 1: CAPABILITY PROBING (GENERATION) ===
You MUST start by generating a simple 'probe' program first. This is a strict, non-negotiable requirement
to verify that the test environment has the necessary kernel capabilities and privileges.
This program's sole purpose is to verify subsystem availability and privileges by probing specific
device files, subsystems, or syscalls (for example: opening /dev/vhci to check if the virtual
Bluetooth controller is accessible, loading a minimal dummy BPF program, or making a specific
socket/ioctl call).

Print clear messages indicating success or failure of these probes, and exit with 0 only if
all checks pass.
Do NOT attempt complex logic, and do NOT try to trigger the actual bug/crash in this first version,
regardless of how simple the reproducer seems. You must wait until a successful probe run has been
confirmed in the environment (i.e., when CapabilitiesVerified becomes true).

Prefer calling several tools at the same time to save round-trips.


Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.

Bug Description: possible deadlock in n_tty_receive_buf_common

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
kworker/u33:3/62 is trying to acquire lock:
ffff88804b3fe2c8 (&tty->termios_rwsem){++++}-{4:4}, at: class_rwsem_read_constructor include/linux/rwsem.h:259 [inline]
ffff88804b3fe2c8 (&tty->termios_rwsem){++++}-{4:4}, at: n_tty_receive_buf_common+0x85/0x1930 drivers/tty/n_tty.c:1678

but task is already holding lock:
ffff88801404a8b8 (&buf->lock){+.+.}-{4:4}, at: flush_to_ldisc+0x34/0x730 drivers/tty/tty_buffer.c:474

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&buf->lock){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       tty_buffer_flush+0x72/0x310 drivers/tty/tty_buffer.c:236
       tty_ldisc_flush+0xd2/0xf0 drivers/tty/tty_ldisc.c:388
       __do_SAK+0x368/0x480 drivers/tty/tty_io.c:3025
       vc_SAK+0x7f/0x320 drivers/tty/vt/vt_ioctl.c:994
       process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
       process_scheduled_works kernel/workqueue.c:3405 [inline]
       worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
       kthread+0x370/0x450 kernel/kthread.c:436
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #2 (console_lock){+.+.}-{0:0}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       console_lock+0x7a/0xa0 kernel/printk/printk.c:2896
       uart_configure_port drivers/tty/serial/serial_core.c:2530 [inline]
       serial_core_add_one_port drivers/tty/serial/serial_core.c:3101 [inline]
       serial_core_register_port+0xe65/0x16f0 drivers/tty/serial/serial_core.c:3322
       serial8250_register_8250_port+0x15af/0x2330 drivers/tty/serial/8250/8250_core.c:828
       serial_pnp_probe+0x436/0x930 drivers/tty/serial/8250/8250_pnp.c:480
       pnp_device_probe+0x2b3/0x4a0 drivers/pnp/driver.c:111
       call_driver_probe drivers/base/dd.c:628 [inline]
       really_probe+0x241/0xa60 drivers/base/dd.c:706
       __driver_probe_device+0x20e/0x450 drivers/base/dd.c:868
       driver_probe_device+0x4a/0x140 drivers/base/dd.c:898
       __driver_attach+0x21f/0x5b0 drivers/base/dd.c:1292
       bus_for_each_dev+0x13e/0x1d0 drivers/base/bus.c:383
       bus_add_driver+0x305/0x5b0 drivers/base/bus.c:763
       driver_register+0x1e2/0x360 drivers/base/driver.c:174
       serial8250_init+0xcc/0x1c0 drivers/tty/serial/8250/8250_platform.c:317
       do_one_initcall+0x11d/0x700 init/main.c:1347
       do_initcall_level init/main.c:1409 [inline]
       do_initcalls init/main.c:1425 [inline]
       do_basic_setup init/main.c:1445 [inline]
       kernel_init_freeable+0x6ea/0x7b0 init/main.c:1658
       kernel_init+0x1f/0x1e0 init/main.c:1548
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #1 (&port->mutex){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       class_mutex_constructor include/linux/mutex.h:253 [inline]
       uart_set_termios+0x8e/0x690 drivers/tty/serial/serial_core.c:1645
       tty_set_termios+0x64d/0x980 drivers/tty/tty_ioctl.c:341
       set_termios+0x5c8/0x880 drivers/tty/tty_ioctl.c:516
       tty_mode_ioctl+0x17e/0xd40 drivers/tty/tty_ioctl.c:803
       n_tty_ioctl_helper+0x47/0x2b0 drivers/tty/tty_ioctl.c:982
       n_tty_ioctl+0x53/0x340 drivers/tty/n_tty.c:2496
       tty_ioctl+0x11b4/0x1640 drivers/tty/tty_io.c:2801
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl fs/ioctl.c:583 [inline]
       __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x115/0x840 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&tty->termios_rwsem){++++}-{4:4}:
       check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       down_read+0x99/0x4c0 kernel/locking/rwsem.c:1574
       class_rwsem_read_constructor include/linux/rwsem.h:259 [inline]
       n_tty_receive_buf_common+0x85/0x1930 drivers/tty/n_tty.c:1678
       tty_ldisc_receive_buf+0xaa/0x1a0 drivers/tty/tty_buffer.c:394
       tty_port_default_receive_buf+0x70/0xb0 drivers/tty/tty_port.c:37
       receive_buf drivers/tty/tty_buffer.c:452 [inline]
       flush_to_ldisc+0x26b/0x730 drivers/tty/tty_buffer.c:502
       process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
       process_scheduled_works kernel/workqueue.c:3405 [inline]
       worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
       kthread+0x370/0x450 kernel/kthread.c:436
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

other info that might help us debug this:

Chain exists of:
  &tty->termios_rwsem --> console_lock --> &buf->lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&buf->lock);
                               lock(console_lock);
                               lock(&buf->lock);
  rlock(&tty->termios_rwsem);

 *** DEADLOCK ***

4 locks held by kworker/u33:3/62:
 #0: ffff88801bce4140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x12b1/0x1940 kernel/workqueue.c:3297
 #1: ffffc900009efd08 ((work_completion)(&buf->work)){+.+.}-{0:0}, at: process_one_work+0x988/0x1940 kernel/workqueue.c:3298
 #2: ffff88801404a8b8 (&buf->lock){+.+.}-{4:4}, at: flush_to_ldisc+0x34/0x730 drivers/tty/tty_buffer.c:474
 #3: ffff88804b3fe0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref+0x21/0x90 drivers/tty/tty_ldisc.c:263

stack backtrace:
CPU: 0 UID: 0 PID: 62 Comm: kworker/u33:3 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: events_unbound flush_to_ldisc
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_circular_bug.cold+0x178/0x1c7 kernel/locking/lockdep.c:2043
 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2175
 check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237
 lock_acquire kernel/locking/lockdep.c:5868 [inline]
 lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
 down_read+0x99/0x4c0 kernel/locking/rwsem.c:1574
 class_rwsem_read_constructor include/linux/rwsem.h:259 [inline]
 n_tty_receive_buf_common+0x85/0x1930 drivers/tty/n_tty.c:1678
 tty_ldisc_receive_buf+0xaa/0x1a0 drivers/tty/tty_buffer.c:394
 tty_port_default_receive_buf+0x70/0xb0 drivers/tty/tty_port.c:37
 receive_buf drivers/tty/tty_buffer.c:452 [inline]
 flush_to_ldisc+0x26b/0x730 drivers/tty/tty_buffer.c:502
 process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
 process_scheduled_works kernel/workqueue.c:3405 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Strategy: To reproduce this circular locking dependency warning, we need to trigger the lock dependencies that form the cycle. Lockdep tracks dependencies between lock classes globally, so we don't need to cause an actual deadlock; we just need to execute the code paths that take these locks in the required order sequentially.

### Lock Dependency Analysis

The cycle consists of 4 lock classes:
1. `&port->mutex` -> `console_lock`: This dependency is **already recorded during boot** when the kernel registers the serial console (`serial8250_init` -> `uart_configure_port`). We don't need to trigger it manually.
2. `&tty->termios_rwsem` -> `&port->mutex`: This is triggered when setting termios on a serial port. `tty_set_termios` takes `&tty->termios_rwsem` (write) and then calls `uart_set_termios` which takes `&port->mutex`.
3. `console_lock` -> `&buf->lock`: This is triggered by the Secure Attention Key (SAK) on a virtual console. `vc_SAK` takes `console_lock` and then calls `__do_SAK` -> `tty_ldisc_flush` -> `tty_buffer_flush` which takes `&buf->lock`.
4. `&buf->lock` -> `&tty->termios_rwsem`: This is triggered by the normal tty receive path. `flush_to_ldisc` takes `&buf->lock` and then calls `n_tty_receive_buf_common` which takes `&tty->termios_rwsem` (read).

### Reproduction Strategy

We can write a minimal C program that sequentially triggers the remaining 3 dependencies:
1. **Open a serial port** (e.g., `/dev/ttyS0`) and call `ioctl(fd, TCSETS, &term)` to record `&tty->termios_rwsem` -> `&port->mutex`.
2. **Write 'k' to `/proc/sysrq-trigger`** to simulate a SAK keypress. This schedules `vc_SAK` work, recording `console_lock` -> `&buf->lock`.
3. **Open a PTY pair** and write to the slave PTY. This queues data to the master PTY and schedules `flush_to_ldisc`, recording `&buf->lock` -> `&tty->termios_rwsem`.

Once the last dependency is recorded, lockdep will detect the cycle and emit the warning.

### Minimal C Reproducer

```c
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <stdlib.h>

int main(void) {
    // 1. Trigger: &tty->termios_rwsem -> &port->mutex
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial >= 0) {
        struct termios term;
        if (ioctl(fd_serial, TCGETS, &term) == 0) {
            ioctl(fd_serial, TCSETS, &term);
        }
        close(fd_serial);
    }

    // 2. Trigger: console_lock -> &buf->lock
    int fd_sysrq = open("/proc/sysrq-trigger", O_WRONLY);
    if (fd_sysrq >= 0) {
        write(fd_sysrq, "k", 1);
        close(fd_sysrq);
        // Wait a bit for the vc_SAK workqueue to execute
        usleep(100000);
    }

    // 3. Trigger: &buf->lock -> &tty->termios_rwsem
    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx >= 0) {
        grantpt(ptmx);
        unlockpt(ptmx);
        char *pts_name = ptsname(ptmx);
        if (pts_name) {
            int pts = open(pts_name, O_RDWR | O_NOCTTY);
            if (pts >= 0) {
                // Writing to the slave PTY triggers flush_to_ldisc on the master PTY
                write(pts, "a", 1);
                // Wait a bit for the flush_to_ldisc workqueue to execute
                usleep(100000);
                close(pts);
            }
        }
        close(ptmx);
    }

    return 0;
}
```

gemini-3.1-pro-preview

							input: 7680
							output: 385
							thoughts: 1337
						

**My Thought Process for Generating a Capability Probe Program**

When tasked with generating a minimal C program for capability probing, my primary goal is to verify access to the specific system resources implicated in a suspected locking bug within `n_tty_receive_buf_common`. The bug description hints at a circular locking dependency, and the proposed strategy involves interacting with serial ports, the `/proc/sysrq-trigger` interface, and PTY (pseudo-terminal) devices.

First, I need to confirm that I can interact with the components mentioned in the strategy. This means being able to:

1.  **Open a serial port:** The strategy specifically points to `/dev/ttyS0`. While other serial ports might exist, `/dev/ttyS0` is a common default, so it's a good starting point for probing. My initial thought is to just attempt an `open()` call with read/write and `O_NOCTTY` flags. If this fails, it might indicate a lack of access to serial devices or that `/dev/ttyS0` simply isn't present.

2.  **Access `/proc/sysrq-trigger`:** The strategy requires writing to this special file to simulate a SAK (System Request Key) event. This operation typically demands elevated privileges, often root or specific capabilities. My immediate concern is whether the testing environment (likely syzkaller, which usually runs with high privileges) will permit this. I need to attempt an `open()` call with write-only access (`O_WRONLY`).

3.  **Create a PTY pair:** The strategy involves opening `/dev/ptmx` and subsequently creating a PTY pair. This is crucial for testing interactions that might rely on terminal emulation. I'll need to `open()` `/dev/ptmx` with read/write and `O_NOCTTY` flags.

Considering these points, I'll construct a simple C program. I'll start by attempting to open `/dev/ttyS0`. If that fails, my initial inclination is to exit, as it's a key component of the proposed trigger mechanism. However, I pause to reconsider: is `/dev/ttyS0` *strictly* necessary for the *initial capability probe*? Or can I proceed if it's unavailable, perhaps relying on another serial device or even a PTY for a later stage? The dependency `&tty->termios_rwsem` -> `&port->mutex` seems specific to `serial_core`, reinforcing the importance of a serial port. For the purpose of a *capability probe* to ensure the environment is set up correctly, it's safer to be strict. If `/dev/ttyS0` isn't accessible, the trigger might fail anyway, so I'll stick with exiting if it can't be opened.

Next, I'll check the `/proc/sysrq-trigger` opening. If this fails, it's a definite blocker for the proposed exploit, so I'll exit immediately. Similarly, opening `/dev/ptmx` is essential. If that fails, the PTY interaction cannot occur, and I'll exit.

My initial C code draft would look something like this, including basic error checking using `strerror(errno)` for informative messages:

```c
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>

int main(void) {
    // Attempt to open /dev/ttyS0
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) {
        printf("[-] Failed to open /dev/ttyS0: %s\n", strerror(errno));
        exit(1); // Exiting as /dev/ttyS0 seems crucial for the initial dependency
    }
    printf("[+] Successfully opened /dev/ttyS0.\n");
    close(fd_serial); // Close immediately as we only need to check accessibility

    // Attempt to open /proc/sysrq-trigger
    int fd_sysrq = open("/proc/sysrq-trigger", O_WRONLY);
    if (fd_sysrq < 0) {
        printf("[-] Failed to open /proc/sysrq-trigger: %s\n", strerror(errno));
        exit(1); // Essential for triggering SAK
    }
    printf("[+] Successfully opened /proc/sysrq-trigger.\n");
    close(fd_sysrq); // Close immediately

    // Attempt to open /dev/ptmx
    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx < 0) {
        printf("[-] Failed to open /dev/ptmx: %s\n", strerror(errno));
        exit(1); // Essential for PTY interaction
    }
    printf("[+] Successfully opened /dev/ptmx.\n");
    close(ptmx); // Close immediately

    printf("[+] All probes successful.\n");
    return 0;
}
```

I then refine this slightly. For the probe itself, I don't need to perform any `ioctl` operations or use `termios.h`. The core requirement is simply to verify that the *files* can be opened with the necessary permissions. Thus, the code I've drafted seems sufficient. I also add a final message indicating overall success.

Finally, I understand that this probe will be delivered using the `set-results` tool, which implies it's intended to be part of a larger test harness. The code is minimal, self-contained, and directly addresses the capability checks derived from the proposed bug reproduction strategy.

map[IsProbe:true RawCandidateReproC:#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>

int main(void) {
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) {
        printf("[-] Failed to open /dev/ttyS0: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/ttyS0.\n");
    close(fd_serial);

    int fd_sysrq = open("/proc/sysrq-trigger", O_WRONLY);
    if (fd_sysrq < 0) {
        printf("[-] Failed to open /proc/sysrq-trigger: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /proc/sysrq-trigger.\n");
    close(fd_sysrq);

    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx < 0) {
        printf("[-] Failed to open /dev/ptmx: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/ptmx.\n");
    close(ptmx);

    printf("[+] All probes successful.\n");
    return 0;
}
]

map[IsProbe:true RawCandidateReproC:#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>

int main(void) {
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) {
        printf("[-] Failed to open /dev/ttyS0: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/ttyS0.\n");
    close(fd_serial);

    int fd_sysrq = open("/proc/sysrq-trigger", O_WRONLY);
    if (fd_sysrq < 0) {
        printf("[-] Failed to open /proc/sysrq-trigger: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /proc/sysrq-trigger.\n");
    close(fd_sysrq);

    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx < 0) {
        printf("[-] Failed to open /dev/ptmx: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/ptmx.\n");
    close(ptmx);

    printf("[+] All probes successful.\n");
    return 0;
}
]

map[CurrentCandidateReproC:#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>

int main(void) {
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) {
        printf("[-] Failed to open /dev/ttyS0: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/ttyS0.\n");
    close(fd_serial);

    int fd_sysrq = open("/proc/sysrq-trigger", O_WRONLY);
    if (fd_sysrq < 0) {
        printf("[-] Failed to open /proc/sysrq-trigger: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /proc/sysrq-trigger.\n");
    close(fd_sysrq);

    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx < 0) {
        printf("[-] Failed to open /dev/ptmx: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/ptmx.\n");
    close(ptmx);

    printf("[+] All probes successful.\n");
    return 0;
}
]

map[CompilerError: FormattedReproC:#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>

int main(void) {
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) {
        printf("[-] Failed to open /dev/ttyS0: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/ttyS0.\n");
    close(fd_serial);

    int fd_sysrq = open("/proc/sysrq-trigger", O_WRONLY);
    if (fd_sysrq < 0) {
        printf("[-] Failed to open /proc/sysrq-trigger: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /proc/sysrq-trigger.\n");
    close(fd_sysrq);

    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx < 0) {
        printf("[-] Failed to open /dev/ptmx: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/ptmx.\n");
    close(ptmx);

    printf("[+] All probes successful.\n");
    return 0;
}
]

map[CompilerError:]

map[CandidateBugTitle: CandidateCrashReport: CandidateReproduced:false ConsoleOutput:[   96.654172][   T33] kauditd_printk_skb: 10 callbacks suppressed
[   96.654181][   T33] audit: type=1400 audit(1786491773.474:201): avc:  denied  { transition } for  pid=5833 comm="sshd-session" path="/bin/sh" dev="sda1" ino=90 scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   96.663622][   T33] audit: type=1400 audit(1786491773.474:202): avc:  denied  { noatsecure } for  pid=5833 comm="sshd-session" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   96.670028][   T33] audit: type=1400 audit(1786491773.474:203): avc:  denied  { rlimitinh } for  pid=5833 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   96.676599][   T33] audit: type=1400 audit(1786491773.474:204): avc:  denied  { siginh } for  pid=5833 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   98.375821][   T33] audit: type=1400 audit(1786491775.194:205): avc:  denied  { write } for  pid=5842 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   98.420779][   T33] audit: type=1400 audit(1786491775.234:206): avc:  denied  { write } for  pid=5845 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   98.497555][   T33] audit: type=1400 audit(1786491775.314:207): avc:  denied  { write } for  pid=5848 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   98.540677][   T33] audit: type=1400 audit(1786491775.354:208): avc:  denied  { write } for  pid=5851 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
Warning: Permanently added '[localhost]:23431' (ED25519) to the list of known hosts.
[+] Successfully opened /dev/ttyS0.
[-] Failed to open /proc/sysrq-trigger: No such file or directory
[  100.608951][   T33] audit: type=1400 audit(1786491777.424:209): avc:  denied  { write } for  pid=5863 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  100.655350][   T33] audit: type=1400 audit(1786491777.474:210): avc:  denied  { write } for  pid=5866 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  101.765923][   T33] kauditd_printk_skb: 2 callbacks suppressed
[  101.765935][   T33] audit: type=1400 audit(1786491778.584:213): avc:  denied  { write } for  pid=5875 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  101.804515][   T33] audit: type=1400 audit(1786491778.624:214): avc:  denied  { write } for  pid=5878 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  102.510686][   T33] audit: type=1400 audit(1786491779.324:215): avc:  denied  { write } for  pid=5881 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  102.556083][   T33] audit: type=1400 audit(1786491779.374:216): avc:  denied  { write } for  pid=5884 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  102.626988][   T33] audit: type=1400 audit(1786491779.444:217): avc:  denied  { write } for  pid=5887 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  102.671082][   T33] audit: type=1400 audit(1786491779.484:218): avc:  denied  { write } for  pid=5890 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  102.882249][   T33] audit: type=1400 audit(1786491779.704:219): avc:  denied  { write } for  pid=5893 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  102.920387][   T33] audit: type=1400 audit(1786491779.734:220): avc:  denied  { write } for  pid=5896 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
 OtherCrashReports:<nil> StraceOutput:/strace -e \!wait4,clock_nanosleep,nanosleep -s 100 -x -f /syz-executor3847421792

<...>
[   69.221755][   T33] kauditd_printk_skb: 10 callbacks suppressed
[   69.221765][   T33] audit: type=1400 audit(1786491872.347:201): avc:  denied  { transition } for  pid=5826 comm="sshd-session" path="/bin/sh" dev="sda1" ino=90 scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   69.239624][   T33] audit: type=1400 audit(1786491872.357:202): avc:  denied  { noatsecure } for  pid=5826 comm="sshd-session" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   69.247448][   T33] audit: type=1400 audit(1786491872.357:203): avc:  denied  { rlimitinh } for  pid=5826 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   69.255009][   T33] audit: type=1400 audit(1786491872.357:204): avc:  denied  { siginh } for  pid=5826 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   71.833144][ T1374] ieee802154 phy0 wpan0: encryption failed: -22
[   71.835627][ T1374] ieee802154 phy1 wpan1: encryption failed: -22
[   72.602196][   T33] audit: type=1400 audit(1786491875.727:205): avc:  denied  { write } for  pid=5839 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   72.654665][   T33] audit: type=1400 audit(1786491875.777:206): avc:  denied  { write } for  pid=5843 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   72.756100][   T33] audit: type=1400 audit(1786491875.877:207): avc:  denied  { write } for  pid=5846 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   72.805659][   T33] audit: type=1400 audit(1786491875.927:208): avc:  denied  { write } for  pid=5850 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
Warning: Permanently added '[localhost]:65465' (ED25519) to the list of known hosts.
[   72.882526][   T33] audit: type=1400 audit(1786491876.007:209): avc:  denied  { write } for  pid=5854 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   72.927314][   T33] audit: type=1400 audit(1786491876.047:210): avc:  denied  { write } for  pid=5858 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
execve("/syz-executor3847421792", ["/syz-executor3847421792"], 0x7ffd8edd68a0 /* 11 vars */) = 0
brk(NULL)                               = 0x5555877dd000
brk(0x5555877ddd80)                     = 0x5555877ddd80
arch_prctl(ARCH_SET_FS, 0x5555877dd400) = 0
set_tid_address(0x5555877dd6d0)         = 5863
set_robust_list(0x5555877dd6e0, 24)     = 0
rseq({cpu_id_start=0, cpu_id=RSEQ_CPU_ID_UNINITIALIZED, rseq_cs=NULL, flags=0, node_id=0, mm_cid=0, slice_ctrl={request=0, granted=0, __reserved=0}, __reserved=0}, 33, 0, 0x53053053) = 0
prlimit64(0, RLIMIT_STACK, NULL, {rlim_cur=8192*1024, rlim_max=RLIM64_INFINITY}) = 0
readlinkat(AT_FDCWD, "/proc/self/exe", "/syz-executor3847421792", 4096) = 23
getrandom("\xd4\x4d\x24\x95\x8d\xcc\x6e\x4d", 8, GRND_NONBLOCK) = 8
brk(NULL)                               = 0x5555877ddd80
brk(0x5555877fed80)                     = 0x5555877fed80
brk(0x5555877ff000)                     = 0x5555877ff000
mprotect(0x7f1e3aa8a000, 20480, PROT_READ) = 0
openat(AT_FDCWD, "/dev/ttyS0", O_RDWR|O_NOCTTY) = 3
fstat(1, {st_mode=S_IFIFO|0600, st_size=0, ...}) = 0
close(3)                                = 0
openat(AT_FDCWD, "/proc/sysrq-trigger", O_WRONLY) = -1 ENOENT (No such file or directory)
write(1, "[+] Successfully opened /dev/ttyS0.\n[-] Failed to open /proc/sysrq-trigger: No such file or director"..., 102) = 102
[+] Successfully opened /dev/ttyS0.
[-] Failed to open /proc/sysrq-trigger: No such file or directory
exit_group(1)                           = ?
+++ exited with 1 +++
[   74.259827][   T33] kauditd_printk_skb: 5 callbacks suppressed
[   74.259838][   T33] audit: type=1400 audit(1786491877.387:216): avc:  denied  { write } for  pid=5879 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   74.337567][   T33] audit: type=1400 audit(1786491877.457:217): avc:  denied  { write } for  pid=5882 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   74.378373][   T33] audit: type=1400 audit(1786491877.497:218): avc:  denied  { write } for  pid=5885 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   74.998007][   T33] audit: type=1400 audit(1786491878.117:219): avc:  denied  { write } for  pid=5888 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   75.038084][   T33] audit: type=1400 audit(1786491878.157:220): avc:  denied  { write } for  pid=5891 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   82.076596][   T32] cfg80211: failed to load regulatory.db
 TestError:]

map[TruncatedConsoleOutput:[   96.654172][   T33] kauditd_printk_skb: 10 callbacks suppressed
[   96.654181][   T33] audit: type=1400 audit(1786491773.474:201): avc:  denied  { transition } for  pid=5833 comm="sshd-session" path="/bin/sh" dev="sda1" ino=90 scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   96.663622][   T33] audit: type=1400 audit(1786491773.474:202): avc:  denied  { noatsecure } for  pid=5833 comm="sshd-session" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   96.670028][   T33] audit: type=1400 audit(1786491773.474:203): avc:  denied  { rlimitinh } for  pid=5833 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   96.676599][   T33] audit: type=1400 audit(1786491773.474:204): avc:  denied  { siginh } for  pid=5833 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   98.375821][   T33] audit: type=1400 audit(1786491775.194:205): avc:  denied  { write } for  pid=5842 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   98.420779][   T33] audit: type=1400 audit(1786491775.234:206): avc:  denied  { write } for  pid=5845 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   98.497555][   T33] audit: type=1400 audit(1786491775.314:207): avc:  denied  { write } for  pid=5848 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   98.540677][   T33] audit: type=1400 audit(1786491775.354:208): avc:  denied  { write } for  pid=5851 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
Warning: Permanently added '[localhost]:23431' (ED25519) to the list of known hosts.
[+] Successfully opened /dev/ttyS0.
[-] Failed to open /proc/sysrq-trigger: No such file or directory
[  100.608951][   T33] audit: type=1400 audit(1786491777.424:209): avc:  denied  { write } for  pid=5863 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  100.655350][   T33] audit: type=1400 audit(1786491777.474:210): avc:  denied  { write } for  pid=5866 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  101.765923][   T33] kauditd_printk_skb: 2 callbacks suppressed
[  101.765935][   T33] audit: type=1400 audit(1786491778.584:213): avc:  denied  { write } for  pid=5875 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  101.804515][   T33] audit: type=1400 audit(1786491778.624:214): avc:  denied  { write } for  pid=5878 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  102.510686][   T33] audit: type=1400 audit(1786491779.324:215): avc:  denied  { write } for  pid=5881 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  102.556083][   T33] audit: type=1400 audit(1786491779.374:216): avc:  denied  { write } for  pid=5884 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  102.626988][   T33] audit: type=1400 audit(1786491779.444:217): avc:  denied  { write } for  pid=5887 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  102.671082][   T33] audit: type=1400 audit(1786491779.484:218): avc:  denied  { write } for  pid=5890 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  102.882249][   T33] audit: type=1400 audit(1786491779.704:219): avc:  denied  { write } for  pid=5893 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  102.920387][   T33] audit: type=1400 audit(1786491779.734:220): avc:  denied  { write } for  pid=5896 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
 TruncatedCrashReport: TruncatedStraceOutput:/strace -e \!wait4,clock_nanosleep,nanosleep -s 100 -x -f /syz-executor3847421792

<...>
[   69.221755][   T33] kauditd_printk_skb: 10 callbacks suppressed
[   69.221765][   T33] audit: type=1400 audit(1786491872.347:201): avc:  denied  { transition } for  pid=5826 comm="sshd-session" path="/bin/sh" dev="sda1" ino=90 scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   69.239624][   T33] audit: type=1400 audit(1786491872.357:202): avc:  denied  { noatsecure } for  pid=5826 comm="sshd-session" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   69.247448][   T33] audit: type=1400 audit(1786491872.357:203): avc:  denied  { rlimitinh } for  pid=5826 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   69.255009][   T33] audit: type=1400 audit(1786491872.357:204): avc:  denied  { siginh } for  pid=5826 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   71.833144][ T1374] ieee802154 phy0 wpan0: encryption failed: -22
[   71.835627][ T1374] ieee802154 phy1 wpan1: encryption failed: -22
[   72.602196][   T33] audit: type=1400 audit(1786491875.727:205): avc:  denied  { write } for  pid=5839 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   72.654665][   T33] audit: type=1400 audit(1786491875.777:206): avc:  denied  { write } for  pid=5843 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   72.756100][   T33] audit: type=1400 audit(1786491875.877:207): avc:  denied  { write } for  pid=5846 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   72.805659][   T33] audit: type=1400 audit(1786491875.927:208): avc:  denied  { write } for  pid=5850 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
Warning: Permanently added '[localhost]:65465' (ED25519) to the list of known hosts.
[   72.882526][   T33] audit: type=1400 audit(1786491876.007:209): avc:  denied  { write } for  pid=5854 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   72.927314][   T33] audit: type=1400 audit(1786491876.047:210): avc:  denied  { write } for  pid=5858 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
execve("/syz-executor3847421792", ["/syz-executor3847421792"], 0x7ffd8edd68a0 /* 11 vars */) = 0
brk(NULL)                               = 0x5555877dd000
brk(0x5555877ddd80)                     = 0x5555877ddd80
arch_prctl(ARCH_SET_FS, 0x5555877dd400) = 0
set_tid_address(0x5555877dd6d0)         = 5863
set_robust_list(0x5555877dd6e0, 24)     = 0
rseq({cpu_id_start=0, cpu_id=RSEQ_CPU_ID_UNINITIALIZED, rseq_cs=NULL, flags=0, node_id=0, mm_cid=0, slice_ctrl={request=0, granted=0, __reserved=0}, __reserved=0}, 33, 0, 0x53053053) = 0
prlimit64(0, RLIMIT_STACK, NULL, {rlim_cur=8192*1024, rlim_max=RLIM64_INFINITY}) = 0
readlinkat(AT_FDCWD, "/proc/self/exe", "/syz-executor3847421792", 4096) = 23
getrandom("\xd4\x4d\x24\x95\x8d\xcc\x6e\x4d", 8, GRND_NONBLOCK) = 8
brk(NULL)                               = 0x5555877ddd80
brk(0x5555877fed80)                     = 0x5555877fed80
brk(0x5555877ff000)                     = 0x5555877ff000
mprotect(0x7f1e3aa8a000, 20480, PROT_READ) = 0
openat(AT_FDCWD, "/dev/ttyS0", O_RDWR|O_NOCTTY) = 3
fstat(1, {st_mode=S_IFIFO|0600, st_size=0, ...}) = 0
close(3)                                = 0
openat(AT_FDCWD, "/proc/sysrq-trigger", O_WRONLY) = -1 ENOENT (No such file or directory)
write(1, "[+] Successfully opened /dev/ttyS0.\n[-] Failed to open /proc/sysrq-trigger: No such file or director"..., 102) = 102
[+] Successfully opened /dev/ttyS0.
[-] Failed to open /proc/sysrq-trigger: No such file or directory
exit_group(1)                           = ?
+++ exited with 1 +++
[   74.259827][   T33] kauditd_printk_skb: 5 callbacks suppressed
[   74.259838][   T33] audit: type=1400 audit(1786491877.387:216): avc:  denied  { write } for  pid=5879 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   74.337567][   T33] audit: type=1400 audit(1786491877.457:217): avc:  denied  { write } for  pid=5882 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   74.378373][   T33] audit: type=1400 audit(1786491877.497:218): avc:  denied  { write } for  pid=5885 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   74.998007][   T33] audit: type=1400 audit(1786491878.117:219): avc:  denied  { write } for  pid=5888 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   75.038084][   T33] audit: type=1400 audit(1786491878.157:220): avc:  denied  { write } for  pid=5891 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   82.076596][   T32] cfg80211: failed to load regulatory.db
]

best-expensive

map[Feedback:The probe successfully opened `/dev/ttyS0`, but failed to open `/proc/sysrq-trigger` (No such file or directory). This indicates that sysrq is either disabled in the kernel config or restricted by the sandbox. You will need to find an alternative way to trigger the console lock or whatever you intended to do with sysrq (e.g., writing to `/dev/kmsg`, using `ioctl(TIOCLINUX)`, or other console-related operations). Please adjust your reproducer strategy accordingly. ProbePassed:false TerminalError: TitleMatches:false]

You are a security researcher with deep Linux kernel background.
Analyze the results of running the generated program.

=== CRITICAL ENVIRONMENT & TARGET CLASSIFICATION ===
Set 'TerminalError' to a descriptive error message ONLY if:
1. The execution failed due to missing hardware device nodes, subsystems, kernel modules, or privilege limits
   that cannot be loaded, created, or bypassed by user-space C code edits in the VM guest.
2. The target source files or functions described in the bug description do not exist in the checked-out codebase,
   meaning the codebase version is mismatched and the target code is absent.

=== CRITICAL PROHIBITIONS ===
- Do NOT classify a run as a terminal failure or assume a bug is fixed based on git log entries, commit titles,
  or commit messages. Reproducibility can ONLY be determined by executing reproducer candidates in the VM.
- Do NOT suggest C code strategies, repairs, or namespace bypasses when setting 'TerminalError'.


=== PHASE 1: CAPABILITY PROBING (EVALUATION) ===
The executed program was a simple environment probe.
Use this to guide your classification and feedback:
1. If the execution was successful (all environment/subsystem probes passed and program exited with 0),
   set the field 'ProbePassed' to true and provide feedback explicitly indicating that the environment
   is ready and the agent should now proceed to generate the full reproducer in the next iteration.
2. If the probe failed (e.g., missing permissions, missing devices, or sandbox restrictions),
   set the field 'ProbePassed' to false, and explain what failed in the 'Feedback'
   field so the generator can adjust its setups.

Prefer calling several tools at the same time to save round-trips.


Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.

Bug Description: possible deadlock in n_tty_receive_buf_common

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
kworker/u33:3/62 is trying to acquire lock:
ffff88804b3fe2c8 (&tty->termios_rwsem){++++}-{4:4}, at: class_rwsem_read_constructor include/linux/rwsem.h:259 [inline]
ffff88804b3fe2c8 (&tty->termios_rwsem){++++}-{4:4}, at: n_tty_receive_buf_common+0x85/0x1930 drivers/tty/n_tty.c:1678

but task is already holding lock:
ffff88801404a8b8 (&buf->lock){+.+.}-{4:4}, at: flush_to_ldisc+0x34/0x730 drivers/tty/tty_buffer.c:474

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&buf->lock){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       tty_buffer_flush+0x72/0x310 drivers/tty/tty_buffer.c:236
       tty_ldisc_flush+0xd2/0xf0 drivers/tty/tty_ldisc.c:388
       __do_SAK+0x368/0x480 drivers/tty/tty_io.c:3025
       vc_SAK+0x7f/0x320 drivers/tty/vt/vt_ioctl.c:994
       process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
       process_scheduled_works kernel/workqueue.c:3405 [inline]
       worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
       kthread+0x370/0x450 kernel/kthread.c:436
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #2 (console_lock){+.+.}-{0:0}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       console_lock+0x7a/0xa0 kernel/printk/printk.c:2896
       uart_configure_port drivers/tty/serial/serial_core.c:2530 [inline]
       serial_core_add_one_port drivers/tty/serial/serial_core.c:3101 [inline]
       serial_core_register_port+0xe65/0x16f0 drivers/tty/serial/serial_core.c:3322
       serial8250_register_8250_port+0x15af/0x2330 drivers/tty/serial/8250/8250_core.c:828
       serial_pnp_probe+0x436/0x930 drivers/tty/serial/8250/8250_pnp.c:480
       pnp_device_probe+0x2b3/0x4a0 drivers/pnp/driver.c:111
       call_driver_probe drivers/base/dd.c:628 [inline]
       really_probe+0x241/0xa60 drivers/base/dd.c:706
       __driver_probe_device+0x20e/0x450 drivers/base/dd.c:868
       driver_probe_device+0x4a/0x140 drivers/base/dd.c:898
       __driver_attach+0x21f/0x5b0 drivers/base/dd.c:1292
       bus_for_each_dev+0x13e/0x1d0 drivers/base/bus.c:383
       bus_add_driver+0x305/0x5b0 drivers/base/bus.c:763
       driver_register+0x1e2/0x360 drivers/base/driver.c:174
       serial8250_init+0xcc/0x1c0 drivers/tty/serial/8250/8250_platform.c:317
       do_one_initcall+0x11d/0x700 init/main.c:1347
       do_initcall_level init/main.c:1409 [inline]
       do_initcalls init/main.c:1425 [inline]
       do_basic_setup init/main.c:1445 [inline]
       kernel_init_freeable+0x6ea/0x7b0 init/main.c:1658
       kernel_init+0x1f/0x1e0 init/main.c:1548
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #1 (&port->mutex){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       class_mutex_constructor include/linux/mutex.h:253 [inline]
       uart_set_termios+0x8e/0x690 drivers/tty/serial/serial_core.c:1645
       tty_set_termios+0x64d/0x980 drivers/tty/tty_ioctl.c:341
       set_termios+0x5c8/0x880 drivers/tty/tty_ioctl.c:516
       tty_mode_ioctl+0x17e/0xd40 drivers/tty/tty_ioctl.c:803
       n_tty_ioctl_helper+0x47/0x2b0 drivers/tty/tty_ioctl.c:982
       n_tty_ioctl+0x53/0x340 drivers/tty/n_tty.c:2496
       tty_ioctl+0x11b4/0x1640 drivers/tty/tty_io.c:2801
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl fs/ioctl.c:583 [inline]
       __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x115/0x840 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&tty->termios_rwsem){++++}-{4:4}:
       check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       down_read+0x99/0x4c0 kernel/locking/rwsem.c:1574
       class_rwsem_read_constructor include/linux/rwsem.h:259 [inline]
       n_tty_receive_buf_common+0x85/0x1930 drivers/tty/n_tty.c:1678
       tty_ldisc_receive_buf+0xaa/0x1a0 drivers/tty/tty_buffer.c:394
       tty_port_default_receive_buf+0x70/0xb0 drivers/tty/tty_port.c:37
       receive_buf drivers/tty/tty_buffer.c:452 [inline]
       flush_to_ldisc+0x26b/0x730 drivers/tty/tty_buffer.c:502
       process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
       process_scheduled_works kernel/workqueue.c:3405 [inline]
       worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
       kthread+0x370/0x450 kernel/kthread.c:436
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

other info that might help us debug this:

Chain exists of:
  &tty->termios_rwsem --> console_lock --> &buf->lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&buf->lock);
                               lock(console_lock);
                               lock(&buf->lock);
  rlock(&tty->termios_rwsem);

 *** DEADLOCK ***

4 locks held by kworker/u33:3/62:
 #0: ffff88801bce4140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x12b1/0x1940 kernel/workqueue.c:3297
 #1: ffffc900009efd08 ((work_completion)(&buf->work)){+.+.}-{0:0}, at: process_one_work+0x988/0x1940 kernel/workqueue.c:3298
 #2: ffff88801404a8b8 (&buf->lock){+.+.}-{4:4}, at: flush_to_ldisc+0x34/0x730 drivers/tty/tty_buffer.c:474
 #3: ffff88804b3fe0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref+0x21/0x90 drivers/tty/tty_ldisc.c:263

stack backtrace:
CPU: 0 UID: 0 PID: 62 Comm: kworker/u33:3 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: events_unbound flush_to_ldisc
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_circular_bug.cold+0x178/0x1c7 kernel/locking/lockdep.c:2043
 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2175
 check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237
 lock_acquire kernel/locking/lockdep.c:5868 [inline]
 lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
 down_read+0x99/0x4c0 kernel/locking/rwsem.c:1574
 class_rwsem_read_constructor include/linux/rwsem.h:259 [inline]
 n_tty_receive_buf_common+0x85/0x1930 drivers/tty/n_tty.c:1678
 tty_ldisc_receive_buf+0xaa/0x1a0 drivers/tty/tty_buffer.c:394
 tty_port_default_receive_buf+0x70/0xb0 drivers/tty/tty_port.c:37
 receive_buf drivers/tty/tty_buffer.c:452 [inline]
 flush_to_ldisc+0x26b/0x730 drivers/tty/tty_buffer.c:502
 process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
 process_scheduled_works kernel/workqueue.c:3405 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

IsProbe: true
Reproduced: false
Console Output: [   96.654172][   T33] kauditd_printk_skb: 10 callbacks suppressed
[   96.654181][   T33] audit: type=1400 audit(1786491773.474:201): avc:  denied  { transition } for  pid=5833 comm="sshd-session" path="/bin/sh" dev="sda1" ino=90 scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   96.663622][   T33] audit: type=1400 audit(1786491773.474:202): avc:  denied  { noatsecure } for  pid=5833 comm="sshd-session" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   96.670028][   T33] audit: type=1400 audit(1786491773.474:203): avc:  denied  { rlimitinh } for  pid=5833 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   96.676599][   T33] audit: type=1400 audit(1786491773.474:204): avc:  denied  { siginh } for  pid=5833 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   98.375821][   T33] audit: type=1400 audit(1786491775.194:205): avc:  denied  { write } for  pid=5842 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   98.420779][   T33] audit: type=1400 audit(1786491775.234:206): avc:  denied  { write } for  pid=5845 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   98.497555][   T33] audit: type=1400 audit(1786491775.314:207): avc:  denied  { write } for  pid=5848 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   98.540677][   T33] audit: type=1400 audit(1786491775.354:208): avc:  denied  { write } for  pid=5851 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
Warning: Permanently added '[localhost]:23431' (ED25519) to the list of known hosts.
[+] Successfully opened /dev/ttyS0.
[-] Failed to open /proc/sysrq-trigger: No such file or directory
[  100.608951][   T33] audit: type=1400 audit(1786491777.424:209): avc:  denied  { write } for  pid=5863 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  100.655350][   T33] audit: type=1400 audit(1786491777.474:210): avc:  denied  { write } for  pid=5866 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  101.765923][   T33] kauditd_printk_skb: 2 callbacks suppressed
[  101.765935][   T33] audit: type=1400 audit(1786491778.584:213): avc:  denied  { write } for  pid=5875 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  101.804515][   T33] audit: type=1400 audit(1786491778.624:214): avc:  denied  { write } for  pid=5878 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  102.510686][   T33] audit: type=1400 audit(1786491779.324:215): avc:  denied  { write } for  pid=5881 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  102.556083][   T33] audit: type=1400 audit(1786491779.374:216): avc:  denied  { write } for  pid=5884 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  102.626988][   T33] audit: type=1400 audit(1786491779.444:217): avc:  denied  { write } for  pid=5887 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  102.671082][   T33] audit: type=1400 audit(1786491779.484:218): avc:  denied  { write } for  pid=5890 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  102.882249][   T33] audit: type=1400 audit(1786491779.704:219): avc:  denied  { write } for  pid=5893 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  102.920387][   T33] audit: type=1400 audit(1786491779.734:220): avc:  denied  { write } for  pid=5896 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1

Strace Output: /strace -e \!wait4,clock_nanosleep,nanosleep -s 100 -x -f /syz-executor3847421792

<...>
[   69.221755][   T33] kauditd_printk_skb: 10 callbacks suppressed
[   69.221765][   T33] audit: type=1400 audit(1786491872.347:201): avc:  denied  { transition } for  pid=5826 comm="sshd-session" path="/bin/sh" dev="sda1" ino=90 scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   69.239624][   T33] audit: type=1400 audit(1786491872.357:202): avc:  denied  { noatsecure } for  pid=5826 comm="sshd-session" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   69.247448][   T33] audit: type=1400 audit(1786491872.357:203): avc:  denied  { rlimitinh } for  pid=5826 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   69.255009][   T33] audit: type=1400 audit(1786491872.357:204): avc:  denied  { siginh } for  pid=5826 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   71.833144][ T1374] ieee802154 phy0 wpan0: encryption failed: -22
[   71.835627][ T1374] ieee802154 phy1 wpan1: encryption failed: -22
[   72.602196][   T33] audit: type=1400 audit(1786491875.727:205): avc:  denied  { write } for  pid=5839 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   72.654665][   T33] audit: type=1400 audit(1786491875.777:206): avc:  denied  { write } for  pid=5843 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   72.756100][   T33] audit: type=1400 audit(1786491875.877:207): avc:  denied  { write } for  pid=5846 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   72.805659][   T33] audit: type=1400 audit(1786491875.927:208): avc:  denied  { write } for  pid=5850 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
Warning: Permanently added '[localhost]:65465' (ED25519) to the list of known hosts.
[   72.882526][   T33] audit: type=1400 audit(1786491876.007:209): avc:  denied  { write } for  pid=5854 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   72.927314][   T33] audit: type=1400 audit(1786491876.047:210): avc:  denied  { write } for  pid=5858 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
execve("/syz-executor3847421792", ["/syz-executor3847421792"], 0x7ffd8edd68a0 /* 11 vars */) = 0
brk(NULL)                               = 0x5555877dd000
brk(0x5555877ddd80)                     = 0x5555877ddd80
arch_prctl(ARCH_SET_FS, 0x5555877dd400) = 0
set_tid_address(0x5555877dd6d0)         = 5863
set_robust_list(0x5555877dd6e0, 24)     = 0
rseq({cpu_id_start=0, cpu_id=RSEQ_CPU_ID_UNINITIALIZED, rseq_cs=NULL, flags=0, node_id=0, mm_cid=0, slice_ctrl={request=0, granted=0, __reserved=0}, __reserved=0}, 33, 0, 0x53053053) = 0
prlimit64(0, RLIMIT_STACK, NULL, {rlim_cur=8192*1024, rlim_max=RLIM64_INFINITY}) = 0
readlinkat(AT_FDCWD, "/proc/self/exe", "/syz-executor3847421792", 4096) = 23
getrandom("\xd4\x4d\x24\x95\x8d\xcc\x6e\x4d", 8, GRND_NONBLOCK) = 8
brk(NULL)                               = 0x5555877ddd80
brk(0x5555877fed80)                     = 0x5555877fed80
brk(0x5555877ff000)                     = 0x5555877ff000
mprotect(0x7f1e3aa8a000, 20480, PROT_READ) = 0
openat(AT_FDCWD, "/dev/ttyS0", O_RDWR|O_NOCTTY) = 3
fstat(1, {st_mode=S_IFIFO|0600, st_size=0, ...}) = 0
close(3)                                = 0
openat(AT_FDCWD, "/proc/sysrq-trigger", O_WRONLY) = -1 ENOENT (No such file or directory)
write(1, "[+] Successfully opened /dev/ttyS0.\n[-] Failed to open /proc/sysrq-trigger: No such file or director"..., 102) = 102
[+] Successfully opened /dev/ttyS0.
[-] Failed to open /proc/sysrq-trigger: No such file or directory
exit_group(1)                           = ?
+++ exited with 1 +++
[   74.259827][   T33] kauditd_printk_skb: 5 callbacks suppressed
[   74.259838][   T33] audit: type=1400 audit(1786491877.387:216): avc:  denied  { write } for  pid=5879 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   74.337567][   T33] audit: type=1400 audit(1786491877.457:217): avc:  denied  { write } for  pid=5882 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   74.378373][   T33] audit: type=1400 audit(1786491877.497:218): avc:  denied  { write } for  pid=5885 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   74.998007][   T33] audit: type=1400 audit(1786491878.117:219): avc:  denied  { write } for  pid=5888 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   75.038084][   T33] audit: type=1400 audit(1786491878.157:220): avc:  denied  { write } for  pid=5891 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   82.076596][   T32] cfg80211: failed to load regulatory.db

Crash Report: 

gemini-3.1-pro-preview

							input: 11760
							output: 138
							thoughts: 1040
						

**My Thought Process: Analyzing Probe Results and Identifying the Core Issue**

Okay, so I've just run this capability probe, and the output is telling me something crucial. It clearly states it successfully opened `/dev/ttyS0`, which is good – the serial port itself is accessible. However, it *failed* to open `/proc/sysrq-trigger`, with the error "No such file or directory." This immediately jumps out at me because the exit code was 1, indicating an overall failure.

Now, the bug description itself is pointing towards a potential circular locking dependency within `n_tty_receive_buf_common`. The locks involved are `&tty->termios_rwsem`, `console_lock`, `&buf->lock`, and `&port->mutex`. This is the core of the problem I need to investigate.

The probe's attempt to interact with `/dev/ttyS0` and `/proc/sysrq-trigger` needs to be contextualized against this locking bug. The absence of `/proc/sysrq-trigger` is a significant observation. It could mean `CONFIG_MAGIC_SYSRQ` isn't enabled in the kernel, or more likely in this context, the sandbox environment is restricting access to it.

But here's the critical realization: is `/proc/sysrq-trigger` *absolutely essential* for triggering the scenario described in the bug? The bug report *itself* shows the lock dependency chain. We see `serial_core_register_port` and `serial8250_register_8250_port` interacting with `console_lock`, and then `uart_set_termios` and `tty_set_termios` dealing with `&port->mutex`. Most importantly, `n_tty_receive_buf_common` is where the circular lock is detected, and it's explicitly shown to involve `&tty->termios_rwsem`.

The sysrq trigger *might* have been a convenient way to initiate a console print or a similar kernel operation that would exercise these locks. But if the bug is indeed about the locking dependency itself, then the *exact method* of triggering it, as long as it exercises the relevant code paths, might be less critical than the *fact* that the locks are being acquired in a conflicting order.

Given the prompt's instructions: "If the probe failed (e.g., missing permissions, missing devices, or sandbox restrictions), set the field 'ProbePassed' to false, and explain what failed in the 'Feedback' field so the generator can adjust its setups." – this is exactly what I need to do. The probe *did* fail due to a missing device (`/proc/sysrq-trigger`), likely due to sandbox restrictions. Therefore, `ProbePassed` must be `false`.

The feedback needs to clearly state *why* it failed and suggest alternatives. The generator needs to know that sysrq is unavailable and that it should look for another way to provoke the console lock or whatever operation it intended to perform. Options like writing to `/dev/kmsg`, using `ioctl(TIOCLINUX)` for console selection, or directly interacting with `/dev/tty0` could be viable alternatives.

So, to summarize my internal decision-making:
1.  **Probe Outcome:** Successful access to `/dev/ttyS0`, but failed access to `/proc/sysrq-trigger` (exit code 1).
2.  **Bug Context:** Circular locking dependency in `n_tty_receive_buf_common` involving `tty->termios_rwsem`, `console_lock`, `buf->lock`, and `port->mutex`.
3.  **Sysrq Trigger Relevance:** Likely a mechanism to trigger the locking scenario, but not necessarily the *only* way. The core issue is the lock dependency itself.
4.  **Action Required:** Mark `ProbePassed` as `false` due to the missing `/proc/sysrq-trigger`.
5.  **Feedback Content:** Explain the missing `/proc/sysrq-trigger` (kernel config or sandbox restriction) and suggest alternative methods for triggering the console lock/related operations.
6.  **Other Fields:** `TitleMatches` is `false` because no crash occurred. `TerminalError` is empty as the failure was specific to the probe's device access, not a general terminal issue.

This leads me to the `set-results` call with the specific feedback I've outlined.

map[Feedback:The probe successfully opened `/dev/ttyS0`, but failed to open `/proc/sysrq-trigger` (No such file or directory). This indicates that sysrq is either disabled in the kernel config or restricted by the sandbox. You will need to find an alternative way to trigger the console lock or whatever you intended to do with sysrq (e.g., writing to `/dev/kmsg`, using `ioctl(TIOCLINUX)`, or other console-related operations). Please adjust your reproducer strategy accordingly. ProbePassed:false TerminalError: TitleMatches:false]

map[Feedback:The probe successfully opened `/dev/ttyS0`, but failed to open `/proc/sysrq-trigger` (No such file or directory). This indicates that sysrq is either disabled in the kernel config or restricted by the sandbox. You will need to find an alternative way to trigger the console lock or whatever you intended to do with sysrq (e.g., writing to `/dev/kmsg`, using `ioctl(TIOCLINUX)`, or other console-related operations). Please adjust your reproducer strategy accordingly. ProbePassed:false TerminalError: TitleMatches:false]

map[CapabilitiesVerified:false ContinueSignal:continue EquivalenceAnalysis: OracleFeedback:The probe successfully opened `/dev/ttyS0`, but failed to open `/proc/sysrq-trigger` (No such file or directory). This indicates that sysrq is either disabled in the kernel config or restricted by the sandbox. You will need to find an alternative way to trigger the console lock or whatever you intended to do with sysrq (e.g., writing to `/dev/kmsg`, using `ioctl(TIOCLINUX)`, or other console-related operations). Please adjust your reproducer strategy accordingly. ReproC: Reproduced:false ReproducedBugTitle: ReproducedCrashReport:]

map[OracleFeedback:The probe successfully opened `/dev/ttyS0`, but failed to open `/proc/sysrq-trigger` (No such file or directory). This indicates that sysrq is either disabled in the kernel config or restricted by the sandbox. You will need to find an alternative way to trigger the console lock or whatever you intended to do with sysrq (e.g., writing to `/dev/kmsg`, using `ioctl(TIOCLINUX)`, or other console-related operations). Please adjust your reproducer strategy accordingly.]

best-expensive

You are an expert in Linux kernel debugging.
Refine the reproduction strategy based on feedback from previous attempts.
Analyze the technical diagnosis provided in the oracle feedback and translate it into concrete,
step-by-step instructions for the repro-generator on how to modify the code structure, alignments,
offsets, or parameters of the candidate program.

=== TOOL SELECTION GUIDELINES ===
- Prefer codesearch-definition-source and codesearch-struct-layout first for symbol lookups.
- Fall back to read-file or grepper for macros, headers, or if symbol lookup fails.

=== CRITICAL PROHIBITIONS ===
- Do NOT repeat searches for the same symbols or files. Use information you have already gathered.
- Do NOT write long explanations. Keep your reasoning short and focused on actionable changes.
- Do NOT assume a bug is fixed based on git commit history.
- If you are stuck, try a different approach or proceed to generate a candidate reproducer.
Prefer calling several tools at the same time to save round-trips.

Bug Description: possible deadlock in n_tty_receive_buf_common

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
kworker/u33:3/62 is trying to acquire lock:
ffff88804b3fe2c8 (&tty->termios_rwsem){++++}-{4:4}, at: class_rwsem_read_constructor include/linux/rwsem.h:259 [inline]
ffff88804b3fe2c8 (&tty->termios_rwsem){++++}-{4:4}, at: n_tty_receive_buf_common+0x85/0x1930 drivers/tty/n_tty.c:1678

but task is already holding lock:
ffff88801404a8b8 (&buf->lock){+.+.}-{4:4}, at: flush_to_ldisc+0x34/0x730 drivers/tty/tty_buffer.c:474

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&buf->lock){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       tty_buffer_flush+0x72/0x310 drivers/tty/tty_buffer.c:236
       tty_ldisc_flush+0xd2/0xf0 drivers/tty/tty_ldisc.c:388
       __do_SAK+0x368/0x480 drivers/tty/tty_io.c:3025
       vc_SAK+0x7f/0x320 drivers/tty/vt/vt_ioctl.c:994
       process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
       process_scheduled_works kernel/workqueue.c:3405 [inline]
       worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
       kthread+0x370/0x450 kernel/kthread.c:436
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #2 (console_lock){+.+.}-{0:0}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       console_lock+0x7a/0xa0 kernel/printk/printk.c:2896
       uart_configure_port drivers/tty/serial/serial_core.c:2530 [inline]
       serial_core_add_one_port drivers/tty/serial/serial_core.c:3101 [inline]
       serial_core_register_port+0xe65/0x16f0 drivers/tty/serial/serial_core.c:3322
       serial8250_register_8250_port+0x15af/0x2330 drivers/tty/serial/8250/8250_core.c:828
       serial_pnp_probe+0x436/0x930 drivers/tty/serial/8250/8250_pnp.c:480
       pnp_device_probe+0x2b3/0x4a0 drivers/pnp/driver.c:111
       call_driver_probe drivers/base/dd.c:628 [inline]
       really_probe+0x241/0xa60 drivers/base/dd.c:706
       __driver_probe_device+0x20e/0x450 drivers/base/dd.c:868
       driver_probe_device+0x4a/0x140 drivers/base/dd.c:898
       __driver_attach+0x21f/0x5b0 drivers/base/dd.c:1292
       bus_for_each_dev+0x13e/0x1d0 drivers/base/bus.c:383
       bus_add_driver+0x305/0x5b0 drivers/base/bus.c:763
       driver_register+0x1e2/0x360 drivers/base/driver.c:174
       serial8250_init+0xcc/0x1c0 drivers/tty/serial/8250/8250_platform.c:317
       do_one_initcall+0x11d/0x700 init/main.c:1347
       do_initcall_level init/main.c:1409 [inline]
       do_initcalls init/main.c:1425 [inline]
       do_basic_setup init/main.c:1445 [inline]
       kernel_init_freeable+0x6ea/0x7b0 init/main.c:1658
       kernel_init+0x1f/0x1e0 init/main.c:1548
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #1 (&port->mutex){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       class_mutex_constructor include/linux/mutex.h:253 [inline]
       uart_set_termios+0x8e/0x690 drivers/tty/serial/serial_core.c:1645
       tty_set_termios+0x64d/0x980 drivers/tty/tty_ioctl.c:341
       set_termios+0x5c8/0x880 drivers/tty/tty_ioctl.c:516
       tty_mode_ioctl+0x17e/0xd40 drivers/tty/tty_ioctl.c:803
       n_tty_ioctl_helper+0x47/0x2b0 drivers/tty/tty_ioctl.c:982
       n_tty_ioctl+0x53/0x340 drivers/tty/n_tty.c:2496
       tty_ioctl+0x11b4/0x1640 drivers/tty/tty_io.c:2801
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl fs/ioctl.c:583 [inline]
       __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x115/0x840 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&tty->termios_rwsem){++++}-{4:4}:
       check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       down_read+0x99/0x4c0 kernel/locking/rwsem.c:1574
       class_rwsem_read_constructor include/linux/rwsem.h:259 [inline]
       n_tty_receive_buf_common+0x85/0x1930 drivers/tty/n_tty.c:1678
       tty_ldisc_receive_buf+0xaa/0x1a0 drivers/tty/tty_buffer.c:394
       tty_port_default_receive_buf+0x70/0xb0 drivers/tty/tty_port.c:37
       receive_buf drivers/tty/tty_buffer.c:452 [inline]
       flush_to_ldisc+0x26b/0x730 drivers/tty/tty_buffer.c:502
       process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
       process_scheduled_works kernel/workqueue.c:3405 [inline]
       worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
       kthread+0x370/0x450 kernel/kthread.c:436
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

other info that might help us debug this:

Chain exists of:
  &tty->termios_rwsem --> console_lock --> &buf->lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&buf->lock);
                               lock(console_lock);
                               lock(&buf->lock);
  rlock(&tty->termios_rwsem);

 *** DEADLOCK ***

4 locks held by kworker/u33:3/62:
 #0: ffff88801bce4140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x12b1/0x1940 kernel/workqueue.c:3297
 #1: ffffc900009efd08 ((work_completion)(&buf->work)){+.+.}-{0:0}, at: process_one_work+0x988/0x1940 kernel/workqueue.c:3298
 #2: ffff88801404a8b8 (&buf->lock){+.+.}-{4:4}, at: flush_to_ldisc+0x34/0x730 drivers/tty/tty_buffer.c:474
 #3: ffff88804b3fe0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref+0x21/0x90 drivers/tty/tty_ldisc.c:263

stack backtrace:
CPU: 0 UID: 0 PID: 62 Comm: kworker/u33:3 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: events_unbound flush_to_ldisc
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_circular_bug.cold+0x178/0x1c7 kernel/locking/lockdep.c:2043
 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2175
 check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237
 lock_acquire kernel/locking/lockdep.c:5868 [inline]
 lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
 down_read+0x99/0x4c0 kernel/locking/rwsem.c:1574
 class_rwsem_read_constructor include/linux/rwsem.h:259 [inline]
 n_tty_receive_buf_common+0x85/0x1930 drivers/tty/n_tty.c:1678
 tty_ldisc_receive_buf+0xaa/0x1a0 drivers/tty/tty_buffer.c:394
 tty_port_default_receive_buf+0x70/0xb0 drivers/tty/tty_port.c:37
 receive_buf drivers/tty/tty_buffer.c:452 [inline]
 flush_to_ldisc+0x26b/0x730 drivers/tty/tty_buffer.c:502
 process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
 process_scheduled_works kernel/workqueue.c:3405 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Current Strategy: To reproduce this circular locking dependency warning, we need to trigger the lock dependencies that form the cycle. Lockdep tracks dependencies between lock classes globally, so we don't need to cause an actual deadlock; we just need to execute the code paths that take these locks in the required order sequentially.

### Lock Dependency Analysis

The cycle consists of 4 lock classes:
1. `&port->mutex` -> `console_lock`: This dependency is **already recorded during boot** when the kernel registers the serial console (`serial8250_init` -> `uart_configure_port`). We don't need to trigger it manually.
2. `&tty->termios_rwsem` -> `&port->mutex`: This is triggered when setting termios on a serial port. `tty_set_termios` takes `&tty->termios_rwsem` (write) and then calls `uart_set_termios` which takes `&port->mutex`.
3. `console_lock` -> `&buf->lock`: This is triggered by the Secure Attention Key (SAK) on a virtual console. `vc_SAK` takes `console_lock` and then calls `__do_SAK` -> `tty_ldisc_flush` -> `tty_buffer_flush` which takes `&buf->lock`.
4. `&buf->lock` -> `&tty->termios_rwsem`: This is triggered by the normal tty receive path. `flush_to_ldisc` takes `&buf->lock` and then calls `n_tty_receive_buf_common` which takes `&tty->termios_rwsem` (read).

### Reproduction Strategy

We can write a minimal C program that sequentially triggers the remaining 3 dependencies:
1. **Open a serial port** (e.g., `/dev/ttyS0`) and call `ioctl(fd, TCSETS, &term)` to record `&tty->termios_rwsem` -> `&port->mutex`.
2. **Write 'k' to `/proc/sysrq-trigger`** to simulate a SAK keypress. This schedules `vc_SAK` work, recording `console_lock` -> `&buf->lock`.
3. **Open a PTY pair** and write to the slave PTY. This queues data to the master PTY and schedules `flush_to_ldisc`, recording `&buf->lock` -> `&tty->termios_rwsem`.

Once the last dependency is recorded, lockdep will detect the cycle and emit the warning.

### Minimal C Reproducer

```c
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <stdlib.h>

int main(void) {
    // 1. Trigger: &tty->termios_rwsem -> &port->mutex
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial >= 0) {
        struct termios term;
        if (ioctl(fd_serial, TCGETS, &term) == 0) {
            ioctl(fd_serial, TCSETS, &term);
        }
        close(fd_serial);
    }

    // 2. Trigger: console_lock -> &buf->lock
    int fd_sysrq = open("/proc/sysrq-trigger", O_WRONLY);
    if (fd_sysrq >= 0) {
        write(fd_sysrq, "k", 1);
        close(fd_sysrq);
        // Wait a bit for the vc_SAK workqueue to execute
        usleep(100000);
    }

    // 3. Trigger: &buf->lock -> &tty->termios_rwsem
    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx >= 0) {
        grantpt(ptmx);
        unlockpt(ptmx);
        char *pts_name = ptsname(ptmx);
        if (pts_name) {
            int pts = open(pts_name, O_RDWR | O_NOCTTY);
            if (pts >= 0) {
                // Writing to the slave PTY triggers flush_to_ldisc on the master PTY
                write(pts, "a", 1);
                // Wait a bit for the flush_to_ldisc workqueue to execute
                usleep(100000);
                close(pts);
            }
        }
        close(ptmx);
    }

    return 0;
}
```
Feedback: The probe successfully opened `/dev/ttyS0`, but failed to open `/proc/sysrq-trigger` (No such file or directory). This indicates that sysrq is either disabled in the kernel config or restricted by the sandbox. You will need to find an alternative way to trigger the console lock or whatever you intended to do with sysrq (e.g., writing to `/dev/kmsg`, using `ioctl(TIOCLINUX)`, or other console-related operations). Please adjust your reproducer strategy accordingly.

To trigger the `console_lock` -> `&buf->lock` dependency without relying on `/proc/sysrq-trigger` (which might be disabled or restricted), we can use the VT keyboard driver. 

The function `vc_SAK` takes `console_lock` and then calls `__do_SAK`, which takes `&buf->lock`. `vc_SAK` is scheduled by `fn_SAK`, which is triggered when the keyboard driver receives a key mapped to the `K_SAK` keysym. 

We can dynamically map a normal key (e.g., `KEY_A`) to `K_SAK` using the `KDSKBENT` ioctl on a VT device (like `/dev/tty0`). Then, we can inject a `KEY_A` keypress using a virtual input device via `/dev/uinput`. This will simulate the SAK key combination and execute `vc_SAK`, recording the required lock dependency.

### Minimal C Reproducer

```c
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <stdlib.h>
#include <linux/kd.h>
#include <linux/uinput.h>
#include <string.h>
#include <stdio.h>

int main(void) {
    // 1. Trigger: &tty->termios_rwsem -> &port->mutex
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial >= 0) {
        struct termios term;
        if (ioctl(fd_serial, TCGETS, &term) == 0) {
            ioctl(fd_serial, TCSETS, &term);
        }
        close(fd_serial);
    }

    // 2. Trigger: console_lock -> &buf->lock
    // Map KEY_A (keycode 30) to K_SAK (0x020F)
    int fd_tty = open("/dev/tty0", O_RDWR);
    if (fd_tty < 0) fd_tty = open("/dev/tty1", O_RDWR);
    if (fd_tty < 0) fd_tty = open("/dev/console", O_RDWR);
    
    if (fd_tty >= 0) {
        struct kbentry ke;
        ke.kb_table = 0;
        ke.kb_index = 30; // KEY_A
        ke.kb_value = 0x020F; // K_SAK
        ioctl(fd_tty, KDSKBENT, &ke);
        close(fd_tty);
    }

    // Inject KEY_A via uinput to trigger fn_SAK -> vc_SAK
    int ufd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
    if (ufd >= 0) {
        ioctl(ufd, UI_SET_EVBIT, EV_KEY);
        ioctl(ufd, UI_SET_KEYBIT, KEY_A);

        struct uinput_setup usetup;
        memset(&usetup, 0, sizeof(usetup));
        usetup.id.bustype = BUS_USB;
        usetup.id.vendor = 0x1234;
        usetup.id.product = 0x5678;
        strcpy(usetup.name, "Virtual Keyboard");
        ioctl(ufd, UI_DEV_SETUP, &usetup);
        ioctl(ufd, UI_DEV_CREATE);

        usleep(100000); // wait for input device to be registered

        struct input_event ie;
        
        // Press KEY_A
        memset(&ie, 0, sizeof(ie));
        ie.type = EV_KEY;
        ie.code = KEY_A;
        ie.value = 1;
        write(ufd, &ie, sizeof(ie));

        memset(&ie, 0, sizeof(ie));
        ie.type = EV_SYN;
        ie.code = SYN_REPORT;
        ie.value = 0;
        write(ufd, &ie, sizeof(ie));

        // Release KEY_A
        memset(&ie, 0, sizeof(ie));
        ie.type = EV_KEY;
        ie.code = KEY_A;
        ie.value = 0;
        write(ufd, &ie, sizeof(ie));

        memset(&ie, 0, sizeof(ie));
        ie.type = EV_SYN;
        ie.code = SYN_REPORT;
        ie.value = 0;
        write(ufd, &ie, sizeof(ie));

        usleep(100000); // wait for vc_SAK workqueue to execute
        ioctl(ufd, UI_DEV_DESTROY);
        close(ufd);
    }

    // 3. Trigger: &buf->lock -> &tty->termios_rwsem
    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx >= 0) {
        grantpt(ptmx);
        unlockpt(ptmx);
        char *pts_name = ptsname(ptmx);
        if (pts_name) {
            int pts = open(pts_name, O_RDWR | O_NOCTTY);
            if (pts >= 0) {
                // Writing to the slave PTY triggers flush_to_ldisc on the master PTY
                write(pts, "a", 1);
                // Wait a bit for the flush_to_ldisc workqueue to execute
                usleep(100000);
                close(pts);
            }
        }
        close(ptmx);
    }

    return 0;
}
```

gemini-3.1-pro-preview

							input: 7227
							output: 39
							thoughts: 477
						

**My Thought Process on Triggering Console Lock Dependencies**

Okay, so my primary objective here is to reliably trigger a specific lock dependency: `console_lock` leading to `&buf->lock`. The key constraint is that I absolutely *cannot* use the `/proc/sysrq-trigger` mechanism for this.

I've been tracing the dependency chain, and the established path I'm seeing is: `console_lock` -> `&buf->lock`. The specific sequence looks something like this, as indicated by the lockdep output:

```
-> #3 (&buf->lock){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       tty_buffer_flush+0x72/0x310 drivers/tty/tty_buffer.c:236
       tty_ldisc_flush+0xd2/0xf0 drivers/tty/tty_ldisc.c:388
       __do_SAK+0x368/0x480 drivers/tty/tty_io.c:3025
       vc_SAK+0x7f/0x320 drivers/tty/vt/vt_ioctl.c:994
       process_work+0xa23/0x1940 kernel/workqueue.c:3322
```

The critical point in this chain is `vc_SAK`. This function appears to be the entry point that eventually acquires the `console_lock` and then proceeds to `&buf->lock`.

Now, I'm recalling that `vc_SAK` is a work function. This means it's not directly callable in the traditional sense; it's scheduled to run asynchronously. My next step is to figure out *how* `vc_SAK` gets scheduled. Is it initiated by `do_SAK` within `drivers/tty/vt/vt_ioctl.c`? I need to dive into that to understand the scheduling mechanism.

My immediate thought is: can I manipulate userspace to trigger `__do_SAK` or directly schedule `vc_SAK`? This would be the ideal way to achieve my goal without relying on the forbidden `/proc/sysrq-trigger`.

However, I'm also keeping an open mind. Is there *another* independent path that leads to acquiring the `console_lock` and *then* subsequently acquiring `&buf->lock`? Perhaps a different kernel path that also happens to call `console_lock` followed by `&buf->lock`?

Before I get too deep into the workqueue scheduling, I need to double-check my assumption. Does `vc_SAK` *actually* hold or acquire the `console_lock` itself? I'll need to go directly to the source code for `vc_SAK` in `drivers/tty/vt/vt_ioctl.c` to confirm this crucial detail. If it doesn't, my entire line of investigation needs to pivot.

map[ContextFile:drivers/tty/vt/vt_ioctl.c Name:vc_SAK]

map[SourceCode: 978:	void vc_SAK(struct work_struct *work)
 979:	{
 980:		struct vc *vc_con =
 981:			container_of(work, struct vc, SAK_work);
 982:		struct vc_data *vc;
 983:		struct tty_struct *tty;
 984:	
 985:		guard(console_lock)();
 986:		vc = vc_con->d;
 987:		if (!vc)
 988:			return;
 989:	
 990:		/* FIXME: review tty ref counting */
 991:		tty = vc->port.tty;
 992:		/* SAK should also work in all raw modes and reset them properly. */
 993:		if (tty)
 994:			__do_SAK(tty);
 995:		reset_vc(vc);
 996:	}
 SourceFile:drivers/tty/vt/vt_ioctl.c]

gemini-3.1-pro-preview

							input: 8013
							output: 52
							thoughts: 62
						

**My Thought Process Regarding `vc_SAK` and its Scheduling**

Okay, so I've landed on the `vc_SAK` function, and my immediate observation is that this is a "work function." This tells me it's likely intended to be executed asynchronously, likely within a workqueue context, rather than being called directly and synchronously. I see it takes `console_lock` as an argument, which immediately raises a flag about synchronization and potential contention, and then it proceeds to call `__do_SAK(tty)`. This nested call confirms my suspicion that `vc_SAK` is a wrapper or a handler for the core Safety Alert Key (SAK) logic, delegating the actual work to `__do_SAK`.

Now, the crucial question for me, as someone who needs to understand the flow and timing of this code, is *how* `vc_SAK` itself gets scheduled and executed. Since it's identified as a work function, the natural next step is to hunt for where it's *enqueued* or *triggered*. My instinct is to look for any references to `SAK_work` or `vc_SAK` within the scheduling mechanisms of the kernel's workqueue subsystem. I'll be scrutinizing the code that submits work items to the appropriate workqueue, as that's where the initiation point for `vc_SAK`'s execution must reside. This search will be key to understanding the event that leads to a SAK being processed and how the system manages that process.

map[ContextFile:drivers/tty/vt/vt_ioctl.c IncludeSnippetLines:2 Name:vc_SAK SourceTreePrefix:]

map[References:[map[ReferenceKind:takes-address-of ReferencingEntityKind:function ReferencingEntityName:con_init SourceFile:drivers/tty/vt/vt.c SourceLine:3885 SourceSnippet:3883:			vc_cons[currcons].d = vc = kzalloc_obj(struct vc_data,
3884:							       GFP_NOWAIT);
3885:			INIT_WORK(&vc_cons[currcons].SAK_work, vc_SAK);
3886:			tty_port_init(&vc->port);
3887:			visual_init(vc, currcons, true);
] map[ReferenceKind:takes-address-of ReferencingEntityKind:function ReferencingEntityName:vc_allocate SourceFile:drivers/tty/vt/vt.c SourceLine:1109 SourceSnippet:1107:		tty_port_init(&vc->port);
1108:		vc->port.ops = &vc_port_ops;
1109:		INIT_WORK(&vc_cons[currcons].SAK_work, vc_SAK);
1110:	
1111:		visual_init(vc, currcons, true);
]] TruncatedOutput:false]

gemini-3.1-pro-preview

							input: 8396
							output: 50
							thoughts: 41
						

**My Thought Process on SAK_work Scheduling**

Alright, so I've identified that `SAK_work` is being initialized in both `con_init` and `vc_allocate`. My immediate next thought is about how this `SAK_work` is actually being *scheduled* and put into action. Given its initialization points, it's clearly meant to be processed, and I need to understand the mechanism responsible for that. Therefore, my next logical step is to perform a thorough search for all references to `SAK_work` within the codebase. This will help me trace its lifecycle, understand which functions or events trigger its execution, and ultimately clarify its scheduling behavior.

log-in to see details

map[ContextFile:drivers/tty/vt/vt.c IncludeSnippetLines:2 Name:SAK_work SourceTreePrefix:]

map[References:<nil> TruncatedOutput:false]

gemini-3.1-pro-preview

							input: 8486
							output: 30
							thoughts: 27
						

**A Moment of Revelation About `SAK_work`**

Ah, I see it now! It dawns on me that `SAK_work` isn't some standalone entity; my understanding was a bit fragmented. I've just realized, with a sudden flash of clarity, that `SAK_work` is actually an integral field *within* the `struct vc`. This is a crucial piece of information that shifts my perspective considerably. My immediate next step, naturally, is to dive deeper and thoroughly investigate where and how `SAK_work` is being utilized within the context of `struct vc`. This is going to be illuminating.

map[Expression:SAK_work PathPrefix:drivers/tty/vt/]

map[Output:drivers/tty/vt/keyboard.c=634=static void fn_SAK(struct vc_data *vc)
drivers/tty/vt/keyboard.c-635-{
drivers/tty/vt/keyboard.c:636:	struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
drivers/tty/vt/keyboard.c:637:	schedule_work(SAK_work);
drivers/tty/vt/keyboard.c-638-}
--
drivers/tty/vt/vt.c=1082=int vc_allocate(unsigned int currcons)	/* return 0 on success */
--
drivers/tty/vt/vt.c-1108-	vc->port.ops = &vc_port_ops;
drivers/tty/vt/vt.c:1109:	INIT_WORK(&vc_cons[currcons].SAK_work, vc_SAK);
drivers/tty/vt/vt.c-1110-
--
drivers/tty/vt/vt.c=3844=static int __init con_init(void)
--
drivers/tty/vt/vt.c-3884-						       GFP_NOWAIT);
drivers/tty/vt/vt.c:3885:		INIT_WORK(&vc_cons[currcons].SAK_work, vc_SAK);
drivers/tty/vt/vt.c-3886-		tty_port_init(&vc->port);
--
drivers/tty/vt/vt_ioctl.c=978=void vc_SAK(struct work_struct *work)
--
drivers/tty/vt/vt_ioctl.c-980-	struct vc *vc_con =
drivers/tty/vt/vt_ioctl.c:981:		container_of(work, struct vc, SAK_work);
drivers/tty/vt/vt_ioctl.c-982-	struct vc_data *vc;
]

gemini-3.1-pro-preview

							input: 9020
							output: 33
							thoughts: 59
						

**My Thought Process on SAK Key Handling**

Right, so my current line of inquiry is how the SAK (Secure Attention Key) combination is handled within the system. I've identified that `fn_SAK` is the function responsible for initiating the SAK sequence. My immediate question is, what triggers `fn_SAK`? I've confirmed it's activated when the SAK key combination is detected on the keyboard input.

My next logical step is to investigate the underlying mechanism for invoking this SAK functionality. Specifically, I'm wondering if there's a direct `ioctl` (input/output control) call that can be used to programmatically trigger the SAK event. To explore this, I plan to delve into the `vt_ioctl.c` file, as this is where I anticipate finding relevant `ioctl` definitions related to virtual terminal (vt) operations, and therefore, where I'd expect to find any SAK-specific `ioctl` calls. I'll be looking for any `ioctl` commands that explicitly mention or are associated with the SAK functionality.

map[Expression:SAK PathPrefix:drivers/tty/vt/vt_ioctl.c]

map[Output:drivers/tty/vt/vt_ioctl.c=963=void reset_vc(struct vc_data *vc)
--
drivers/tty/vt/vt_ioctl.c-977-
drivers/tty/vt/vt_ioctl.c:978:void vc_SAK(struct work_struct *work)
drivers/tty/vt/vt_ioctl.c-979-{
drivers/tty/vt/vt_ioctl.c-980-	struct vc *vc_con =
drivers/tty/vt/vt_ioctl.c:981:		container_of(work, struct vc, SAK_work);
drivers/tty/vt/vt_ioctl.c-982-	struct vc_data *vc;
--
drivers/tty/vt/vt_ioctl.c-991-	tty = vc->port.tty;
drivers/tty/vt/vt_ioctl.c:992:	/* SAK should also work in all raw modes and reset them properly. */
drivers/tty/vt/vt_ioctl.c-993-	if (tty)
drivers/tty/vt/vt_ioctl.c:994:		__do_SAK(tty);
drivers/tty/vt/vt_ioctl.c-995-	reset_vc(vc);
]

gemini-3.1-pro-preview

							input: 9419
							output: 38
							thoughts: 58
						

**My Thought Process Regarding `SAK` ioctls**

My initial line of inquiry centers on a fundamental question: does a specific `ioctl` call exist within the kernel that directly initiates the `fn_SAK` or `vc_SAK` functionality? This is a crucial point because understanding the programmatic interface for such system-level actions is paramount for anyone working with the kernel's low-level interactions.

My immediate thought process then turned to exploring potential candidates for such an `ioctl`. I began considering known `ioctl` commands that deal with signal handling or terminal-specific operations. Two specific candidates that immediately sprang to mind were `KDSIGACCEPT` and `TIOCLINUX`.

I know `KDSIGACCEPT` is related to signal acceptance, which feels like it *could* be in the same ballpark as triggering a `SAK` event. However, my experience suggests it might be more about how signals are processed *after* they've been generated, rather than the generation itself.

My attention then shifted more firmly to `TIOCLINUX`. This `ioctl` is notoriously versatile and often employed for a variety of non-standard terminal operations. I recalled that `TIOCLINUX` has capabilities that extend beyond simple character manipulation, including the ability to simulate keypresses and, more broadly, to execute other special commands within the terminal context. This versatility makes it a strong contender for something as specific as triggering a `SAK` event, which is often initiated by a particular key combination. Therefore, my focus is now on definitively determining if `TIOCLINUX`, or indeed `KDSIGACCEPT`, provides the direct `ioctl` interface I'm looking for to invoke `fn_SAK` or `vc_SAK`.

map[ContextFile:drivers/tty/vt/vt_ioctl.c Name:tioclinux]

map[SourceCode:3561:	int tioclinux(struct tty_struct *tty, unsigned long arg)
3562:	{
3563:		char type, data;
3564:		char __user *p = (char __user *)arg;
3565:		void __user *param_aligned32 = (u32 __user *)arg + 1;
3566:		void __user *param = (void __user *)arg + 1;
3567:		int lines;
3568:		int ret;
3569:	
3570:		if (current->signal->tty != tty && !capable(CAP_SYS_ADMIN))
3571:			return -EPERM;
3572:		if (get_user(type, p))
3573:			return -EFAULT;
3574:		ret = 0;
3575:	
3576:		switch (type) {
3577:		case TIOCL_SETSEL:
3578:			return set_selection_user(param, tty);
3579:		case TIOCL_PASTESEL:
3580:			if (!capable(CAP_SYS_ADMIN))
3581:				return -EPERM;
3582:			return paste_selection(tty);
3583:		case TIOCL_UNBLANKSCREEN:
3584:			scoped_guard(console_lock)
3585:				unblank_screen();
3586:			break;
3587:		case TIOCL_SELLOADLUT:
3588:			if (!capable(CAP_SYS_ADMIN))
3589:				return -EPERM;
3590:			return sel_loadlut(param_aligned32);
3591:		case TIOCL_GETSHIFTSTATE:
3592:			/*
3593:			 * Make it possible to react to Shift+Mousebutton. Note that
3594:			 * 'shift_state' is an undocumented kernel-internal variable;
3595:			 * programs not closely related to the kernel should not use
3596:			 * this.
3597:			 */
3598:			data = vt_get_shift_state();
3599:			return put_user(data, p);
3600:		case TIOCL_GETMOUSEREPORTING:
3601:			scoped_guard(console_lock)	/* May be overkill */
3602:				data = mouse_reporting();
3603:			return put_user(data, p);
3604:		case TIOCL_SETVESABLANK:
3605:			return set_vesa_blanking(param);
3606:		case TIOCL_GETKMSGREDIRECT:
3607:			data = vt_get_kmsg_redirect();
3608:			return put_user(data, p);
3609:		case TIOCL_SETKMSGREDIRECT:
3610:			if (!capable(CAP_SYS_ADMIN))
3611:				return -EPERM;
3612:	
3613:			if (get_user(data, p+1))
3614:				return -EFAULT;
3615:	
3616:			vt_kmsg_redirect(data);
3617:	
3618:			break;
3619:		case TIOCL_GETFGCONSOLE:
3620:			/*
3621:			 * No locking needed as this is a transiently correct return
3622:			 * anyway if the caller hasn't disabled switching.
3623:			 */
3624:			return fg_console;
3625:		case TIOCL_SCROLLCONSOLE:
3626:			if (get_user(lines, (s32 __user *)param_aligned32))
3627:				return -EFAULT;
3628:	
3629:			/*
3630:			 * Needs the console lock here. Note that lots of other calls
3631:			 * need fixing before the lock is actually useful!
3632:			 */
3633:			scoped_guard(console_lock)
3634:				scrollfront(vc_cons[fg_console].d, lines);
3635:			break;
3636:		case TIOCL_BLANKSCREEN:	/* until explicitly unblanked, not only poked */
3637:			scoped_guard(console_lock) {
3638:				ignore_poke = 1;
3639:				do_blank_screen(0);
3640:			}
3641:			break;
3642:		case TIOCL_BLANKEDSCREEN:
3643:			return console_blanked;
3644:		case TIOCL_GETBRACKETEDPASTE:
3645:			return get_bracketed_paste(tty);
3646:		default:
3647:			return -EINVAL;
3648:		}
3649:	
3650:		return ret;
3651:	}
 SourceFile:drivers/tty/vt/vt.c]

gemini-3.1-pro-preview

							input: 10852
							output: 36
							thoughts: 424
						

**My Thought Process Regarding `TIOCLINUX` and `console_lock` Acquisition**

My initial thought was that `TIOCLINUX`, as a mechanism, doesn't directly expose a Signal-Asserted Key (SAK) trigger, which is a common way to initiate certain console operations. This led me to question how, then, we might arrive at a state where `console_lock` is acquired, and subsequently `&buf->lock` is also acquired.

I then recalled or reviewed the original report, which clearly shows a call trace leading to the acquisition of `&buf->lock`. This trace reveals the path: `lock_acquire` -> `__mutex_lock_common` -> `__mutex_lock`, ultimately within `tty_buffer_flush`. Crucially, this `tty_buffer_flush` is called by `tty_ldisc_flush`, which in turn is invoked by `__do_SAK`, ultimately originating from `vc_SAK`. This entire sequence is triggered by `process_one_work`, which implies a workqueue item is responsible for the SAK operation.

This detailed trace solidified my understanding of how `&buf->lock` is acquired *in that specific context* – via a SAK event processed by the workqueue. However, it didn't immediately answer my core question: is there *any other way* to acquire `console_lock` and then subsequently `&buf->lock` without going through this specific SAK workqueue path?

This prompted me to consider alternative entry points into the console locking mechanism. I started thinking about direct `ioctl` calls that might touch upon the console lock. My attention then turned to `ioctl(fd, TIOCLINUX, ...)` itself. The question became: could `TIOCLINUX`, when invoked with specific arguments, first acquire `console_lock` and then, as part of its execution, subsequently acquire `&buf->lock`?

I decided to investigate one of the `TIOCLINUX` subcommands, specifically `TIOCL_PASTESEL`. My understanding is that this command, when issued, triggers the `paste_selection(tty)` function. The next logical step in my thought process was to determine if `paste_selection(tty)` itself acquires the `console_lock`. To do this, I would need to examine the implementation of `paste_selection`.

map[ContextFile:drivers/tty/vt/vt.c Name:paste_selection]

map[SourceCode: 384:	/* Insert the contents of the selection buffer into the
 385:	 * queue of the tty associated with the current console.
 386:	 * Invoked by ioctl().
 387:	 *
 388:	 * Locking: called without locks. Calls the ldisc wrongly with
 389:	 * unsafe methods,
 390:	 */
 391:	int paste_selection(struct tty_struct *tty)
 392:	{
 393:		struct vc_data *vc = tty->driver_data;
 394:		int	pasted = 0;
 395:		size_t count;
 396:		struct  tty_ldisc *ld;
 397:		DECLARE_WAITQUEUE(wait, current);
 398:		int ret = 0;
 399:	
 400:		bool bp = vc->vc_bracketed_paste;
 401:		static const char bracketed_paste_start[] = "\033[200~";
 402:		static const char bracketed_paste_end[]   = "\033[201~";
 403:		const char *bps = bp ? bracketed_paste_start : NULL;
 404:		const char *bpe = bp ? bracketed_paste_end : NULL;
 405:	
 406:		scoped_guard(console_lock)
 407:			poke_blanked_console();
 408:	
 409:		ld = tty_ldisc_ref_wait(tty);
 410:		if (!ld)
 411:			return -EIO;	/* ldisc was hung up */
 412:		tty_buffer_lock_exclusive(&vc->port);
 413:	
 414:		add_wait_queue(&vc->paste_wait, &wait);
 415:		mutex_lock(&vc_sel.lock);
 416:		while (vc_sel.buffer && (vc_sel.buf_len > pasted || bpe)) {
 417:			set_current_state(TASK_INTERRUPTIBLE);
 418:			if (signal_pending(current)) {
 419:				ret = -EINTR;
 420:				break;
 421:			}
 422:			if (tty_throttled(tty)) {
 423:				mutex_unlock(&vc_sel.lock);
 424:				schedule();
 425:				mutex_lock(&vc_sel.lock);
 426:				continue;
 427:			}
 428:			__set_current_state(TASK_RUNNING);
 429:	
 430:			if (bps) {
 431:				bps += tty_ldisc_receive_buf(ld, bps, NULL, strlen(bps));
 432:				if (*bps != '\0')
 433:					continue;
 434:				bps = NULL;
 435:			}
 436:	
 437:			count = vc_sel.buf_len - pasted;
 438:			if (count) {
 439:				pasted += tty_ldisc_receive_buf(ld, vc_sel.buffer + pasted,
 440:								NULL, count);
 441:				if (vc_sel.buf_len > pasted)
 442:					continue;
 443:			}
 444:	
 445:			if (bpe) {
 446:				bpe += tty_ldisc_receive_buf(ld, bpe, NULL, strlen(bpe));
 447:				if (*bpe == '\0')
 448:					bpe = NULL;
 449:			}
 450:		}
 451:		mutex_unlock(&vc_sel.lock);
 452:		remove_wait_queue(&vc->paste_wait, &wait);
 453:		__set_current_state(TASK_RUNNING);
 454:	
 455:		tty_buffer_unlock_exclusive(&vc->port);
 456:		tty_ldisc_deref(ld);
 457:		return ret;
 458:	}
 SourceFile:drivers/tty/vt/selection.c]

gemini-3.1-pro-preview

							input: 12444
							output: 40
							thoughts: 78
						

**My Thought Process on `paste_selection` and Console Locking**

Okay, so I was looking into the `paste_selection` function, and my initial observation was that it briefly acquires the `console_lock` within the `poke_blanked_console()` function. That's not entirely surprising; console operations often need exclusive access.

However, a more critical detail emerged: `paste_selection` *doesn't* hold that `console_lock` while it proceeds to acquire `&buf->lock`. This distinction is important. My attention was immediately drawn to the function `tty_buffer_lock_exclusive`. I needed to confirm my suspicion: does `tty_buffer_lock_exclusive` indeed take `&buf->lock`? That's the key to understanding the potential locking order and any associated risks. I'm going to verify that call immediately.

map[ContextFile:drivers/tty/vt/selection.c Name:tty_buffer_lock_exclusive]

map[SourceCode:  43:	/**
  44:	 * tty_buffer_lock_exclusive	-	gain exclusive access to buffer
  45:	 * @port: tty port owning the flip buffer
  46:	 *
  47:	 * Guarantees safe use of the &tty_ldisc_ops.receive_buf() method by excluding
  48:	 * the buffer work and any pending flush from using the flip buffer. Data can
  49:	 * continue to be added concurrently to the flip buffer from the driver side.
  50:	 *
  51:	 * See also tty_buffer_unlock_exclusive().
  52:	 */
  53:	void tty_buffer_lock_exclusive(struct tty_port *port)
  54:	{
  55:		struct tty_bufhead *buf = &port->buf;
  56:	
  57:		atomic_inc(&buf->priority);
  58:		mutex_lock(&buf->lock);
  59:	}
 SourceFile:drivers/tty/tty_buffer.c]

gemini-3.1-pro-preview

							input: 12824
							output: 28
							thoughts: 205
						

**My Thought Process Regarding Console Lock Acquisition**

Okay, so I've been digging into this locking behavior, and my initial observation is that `tty_buffer_lock_exclusive` correctly takes `&buf->lock`. That part is sound. The critical issue, however, lies with `paste_selection`. It seems to be acquiring `&buf->lock` *without* holding the `console_lock` beforehand. This is a problem because I need a scenario where `console_lock` is held, and *then* `&buf->lock` is acquired.

The original bug report pointed to `vc_SAK` as a potential example. It correctly acquires `console_lock` and subsequently calls `__do_SAK`, which in turn takes `&buf->lock`. This is exactly the kind of ordered lock acquisition I'm looking for. The immediate question then becomes: how can I trigger `vc_SAK` without going through the usual `/proc/sysrq-trigger` mechanism?

I started considering other ways to initiate SAK. My first thought was to check if there's an ioctl call that can directly trigger SAK. I began reviewing the various VT ioctls – things like `KDSIGACCEPT`, `KDSKBENT`, and others. `KDSIGACCEPT` immediately struck me as being for signal handling, so that's probably not the direct route to SAK.

I then moved on to other VT ioctls, specifically looking at `VT_RELDISP` and `VT_ACTIVATE`. I need to dive into `vt_ioctl.c` itself and specifically search for any mentions or implementations related to SAK to see if any of these ioctls are involved in triggering it. This is where I'm currently focused, trying to uncover a user-space trigger for SAK that doesn't rely on `sysrq`.

map[Expression:SAK PathPrefix:drivers/tty/vt/]

map[Output:drivers/tty/vt/keyboard.c-14- *
drivers/tty/vt/keyboard.c:15: * 11-11-96: SAK should now work in the raw mode (Martin Mares)
drivers/tty/vt/keyboard.c-16- *
--
drivers/tty/vt/keyboard.c=82=static k_handler_fn *k_handler[16] = { K_HANDLERS };
--
drivers/tty/vt/keyboard.c-87-	fn_num,		fn_hold,	fn_scroll_forw,	fn_scroll_back,\
drivers/tty/vt/keyboard.c:88:	fn_boot_it,	fn_caps_on,	fn_compose,	fn_SAK,\
drivers/tty/vt/keyboard.c-89-	fn_dec_console, fn_inc_console, fn_spawn_con,	fn_bare_num
--
drivers/tty/vt/keyboard.c=624=static void fn_spawn_con(struct vc_data *vc)
--
drivers/tty/vt/keyboard.c-633-
drivers/tty/vt/keyboard.c:634:static void fn_SAK(struct vc_data *vc)
drivers/tty/vt/keyboard.c-635-{
drivers/tty/vt/keyboard.c:636:	struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
drivers/tty/vt/keyboard.c:637:	schedule_work(SAK_work);
drivers/tty/vt/keyboard.c-638-}
--
drivers/tty/vt/keyboard.c=648=static void k_spec(struct vc_data *vc, unsigned char value, char up_flag)
--
drivers/tty/vt/keyboard.c-656-	     kbd->kbdmode == VC_OFF) &&
drivers/tty/vt/keyboard.c:657:	     value != KVAL(K_SAK))
drivers/tty/vt/keyboard.c:658:		return;		/* SAK is allowed even in raw mode */
drivers/tty/vt/keyboard.c-659-	fn_handler[value](vc);
--
drivers/tty/vt/keyboard.c=1969=static int vt_kdskbent(unsigned char kbdmode, unsigned char idx,
--
drivers/tty/vt/keyboard.c-2025-	/* Attention Key */
drivers/tty/vt/keyboard.c:2026:	if ((oldval == K_SAK || val == K_SAK) && !capable(CAP_SYS_ADMIN))
drivers/tty/vt/keyboard.c-2027-		return -EPERM;
--
drivers/tty/vt/ucs_width_table.h_shipped=21=static const struct ucs_width16 ucs_bmp_ranges[] = {
--
drivers/tty/vt/ucs_width_table.h_shipped-159-	{ BMP_0WIDTH(0x1A55, 0x1A5E) }, /* TAI THAM CONSONANT SIGN MEDIAL RA - TAI THAM CONSONANT SIGN SA */
drivers/tty/vt/ucs_width_table.h_shipped:160:	{ BMP_0WIDTH(0x1A60, 0x1A7C) }, /* TAI THAM SIGN SAKOT - TAI THAM SIGN KHUEN-LUE KARAN */
drivers/tty/vt/ucs_width_table.h_shipped-161-	{ BMP_0WIDTH(0x1A7F, 0x1A7F) }, /* TAI THAM COMBINING CRYPTOGRAMMIC DOT */
--
drivers/tty/vt/vt.c=1082=int vc_allocate(unsigned int currcons)	/* return 0 on success */
--
drivers/tty/vt/vt.c-1108-	vc->port.ops = &vc_port_ops;
drivers/tty/vt/vt.c:1109:	INIT_WORK(&vc_cons[currcons].SAK_work, vc_SAK);
drivers/tty/vt/vt.c-1110-
--
drivers/tty/vt/vt.c=3844=static int __init con_init(void)
--
drivers/tty/vt/vt.c-3884-						       GFP_NOWAIT);
drivers/tty/vt/vt.c:3885:		INIT_WORK(&vc_cons[currcons].SAK_work, vc_SAK);
drivers/tty/vt/vt.c-3886-		tty_port_init(&vc->port);
--
drivers/tty/vt/vt_ioctl.c=963=void reset_vc(struct vc_data *vc)
--
drivers/tty/vt/vt_ioctl.c-977-
drivers/tty/vt/vt_ioctl.c:978:void vc_SAK(struct work_struct *work)
drivers/tty/vt/vt_ioctl.c-979-{
drivers/tty/vt/vt_ioctl.c-980-	struct vc *vc_con =
drivers/tty/vt/vt_ioctl.c:981:		container_of(work, struct vc, SAK_work);
drivers/tty/vt/vt_ioctl.c-982-	struct vc_data *vc;
--
drivers/tty/vt/vt_ioctl.c-991-	tty = vc->port.tty;
drivers/tty/vt/vt_ioctl.c:992:	/* SAK should also work in all raw modes and reset them properly. */
drivers/tty/vt/vt_ioctl.c-993-	if (tty)
drivers/tty/vt/vt_ioctl.c:994:		__do_SAK(tty);
drivers/tty/vt/vt_ioctl.c-995-	reset_vc(vc);
]

gemini-3.1-pro-preview

							input: 14516
							output: 51
							thoughts: 240
						

**My Thought Process Regarding SAK Triggering**

Okay, so my current line of thinking is focused on how to reliably trigger the `fn_SAK` function. I've observed that `fn_SAK` is indeed called from `k_spec` specifically when the key value encountered is `K_SAK`. This `K_SAK` value, I understand, is designated as a special key.

My immediate question then becomes: can I *inject* a keypress that would ultimately lead to `fn_SAK` being invoked? My initial thought drifts towards `TIOCSTI`. I know `TIOCSTI` is designed for injecting characters directly into the input queue. However, I'm concerned that this might *not* be sufficient to trigger `fn_SAK` because `fn_SAK` is typically activated by actual keyboard *events*. These events, as I understand it, originate from subsystems like `input` or are processed via mechanisms like `KDSKBENT`.

Then, a connection sparks. I recall that `KDSKBENT` *can* actually map a key to `K_SAK`. This is promising! But it still leaves me with the problem of actually *pressing* that mapped key. Simply mapping it isn't enough; I need to simulate the act of pressing it.

I start to ponder if there's a direct `ioctl` call that can simulate a keypress. My mind briefly goes to `KDSIGACCEPT`, but I quickly dismiss that as not being the correct mechanism. I then revisit `ioctl(fd, KDSKBENT, ...)`. While I can use this to establish the mapping of a key to `K_SAK`, it still doesn't solve the fundamental issue of *triggering* the press itself.

I then shift my focus, thinking about other potential console-related `ioctl` calls. I remember `TIOCLINUX` and its various sub-commands like `TIOCL_SETSEL`. This is a tangent, but it's part of exploring the broader console I/O landscape for any potential avenues.

My core problem remains: how do I get to the point of triggering `console_lock` and subsequently `&buf->lock`? I decide my next step is to investigate the callers of `__do_SAK`. Understanding where and how `__do_SAK` is legitimately invoked will hopefully reveal the underlying mechanisms I can leverage or emulate.

map[ContextFile:drivers/tty/tty_io.c IncludeSnippetLines:2 Name:__do_SAK SourceTreePrefix:]

map[References:[map[ReferenceKind:calls ReferencingEntityKind:function ReferencingEntityName:do_SAK_work SourceFile:drivers/tty/tty_io.c SourceLine:3063 SourceSnippet:3061:		struct tty_struct *tty =
3062:			container_of(work, struct tty_struct, SAK_work);
3063:		__do_SAK(tty);
3064:	}
] map[ReferenceKind:calls ReferencingEntityKind:function ReferencingEntityName:vc_SAK SourceFile:drivers/tty/vt/vt_ioctl.c SourceLine:994 SourceSnippet: 992:		/* SAK should also work in all raw modes and reset them properly. */
 993:		if (tty)
 994:			__do_SAK(tty);
 995:		reset_vc(vc);
 996:	}
]] TruncatedOutput:false]

gemini-3.1-pro-preview

							input: 15010
							output: 52
							thoughts: 32
						

**My Thought Process Regarding SAK Scheduling**

Okay, so I've just observed that the `do_SAK_work` function is being invoked, and I know that it, in turn, calls `__do_SAK`. My immediate thought then pivots to the mechanism responsible for *scheduling* this `SAK_work` onto the `tty_struct`. I'm trying to trace back the origin of this execution. What component or process is it that decides *when* and *how* this specific work item, associated with the terminal structure, gets placed on the workqueue to be processed? I need to understand the lifecycle of this `SAK_work` from its inception to its execution on the `tty_struct`.

map[ContextFile:drivers/tty/tty_io.c IncludeSnippetLines:2 Name:do_SAK_work SourceTreePrefix:]

map[References:[map[ReferenceKind:takes-address-of ReferencingEntityKind:function ReferencingEntityName:alloc_tty_struct SourceFile:drivers/tty/tty_io.c SourceLine:3126 SourceSnippet:3124:		spin_lock_init(&tty->files_lock);
3125:		INIT_LIST_HEAD(&tty->tty_files);
3126:		INIT_WORK(&tty->SAK_work, do_SAK_work);
3127:	
3128:		tty->driver = driver;
]] TruncatedOutput:false]

gemini-3.1-pro-preview

							input: 15215
							output: 28
							thoughts: 11
						

**My Thought Process Regarding `tty->SAK_work` Scheduling**

Okay, I need to get to the bottom of this. My immediate thought, when encountering `tty->SAK_work`, is a fundamental question: **Who is the architect of its execution?** In other words, what is the trigger, the event, or the specific condition that leads to this particular work item being scheduled? This isn't just a superficial curiosity; understanding the scheduler is key to understanding the behavior and potential failure points of the system.

My mind immediately goes to the typical mechanisms for scheduling work in the kernel. I'm thinking about a few possibilities:

1.  **Explicit Scheduling within a Driver/Subsystem:** Is `tty->SAK_work` being directly `schedule_work()`'d or `schedule_delayed_work()`'d by some code *within* the TTY driver itself, or a closely related subsystem like a serial port driver or a virtual terminal handler? This would imply a direct response to a specific event that the TTY driver is monitoring – perhaps a character being received, a break signal, a modem status change, or even a user-space request that needs asynchronous processing. The context here would be crucial: is it a routine operation, or is it related to error handling or recovery?

2.  **Interrupt Context:** Could it be scheduled from an interrupt handler? This is a common pattern for deferring longer processing away from the strict real-time constraints of an interrupt. If so, what event is generating the interrupt that then leads to the scheduling? This points to hardware events or very low-level software signals.

3.  **Timer-Based Scheduling:** Is `tty->SAK_work` perhaps part of a timer mechanism? Maybe it's scheduled to run after a certain timeout, or on a periodic basis to check a state or perform a cleanup. This would suggest a time-sensitive operation or a watchdog-like function.

4.  **System Call/IOCTL Interaction:** Is it possible that `tty->SAK_work` is scheduled in response to a specific `ioctl` call or a system call that manipulates the TTY device? Certain administrative or control operations might trigger asynchronous tasks.

5.  **Underlying Device Driver:** The `tty` structure is an abstraction. My next logical step is to consider the underlying device driver that is *using* this `tty` structure. The scheduling of `tty->SAK_work` is likely dictated by the specific hardware or virtual device being managed. Is this a standard serial port? A PTY? A console? Each of these has different underlying mechanisms and event sources.

6.  **"SAK" - What does it signify?** The acronym "SAK" itself is a strong hint. In the TTY subsystem, "SAK" almost invariably stands for "Stuff After Kernel" or, more commonly, the "Secure Attention Key" sequence. If it's related to SAK, then the scheduling is almost certainly tied to the detection of this specific key sequence. This sequence is designed to interrupt whatever the user is doing and bring them to a secure login prompt, typically as a security measure or to recover from a hung system. This would imply that `tty->SAK_work` is scheduled when the SAK sequence is detected, and its purpose is to perform the necessary actions to switch to a secure console or process the SAK event.

Therefore, my primary line of inquiry is to trace the **call chain leading to `schedule_work(&tty->SAK_work)`**. I would be looking for `tty->SAK_work` within the TTY core code and then delving into the specific driver implementations that interact with it, specifically focusing on any code that handles input characters, interrupt handlers, or SAK event detection. The *intent* behind scheduling `tty->SAK_work` is likely to handle the aftermath of the SAK sequence being detected, ensuring a safe and responsive transition.

map[Expression:SAK_work PathPrefix:drivers/tty/]

map[Output:drivers/tty/sysrq.c=117=static void sysrq_handle_SAK(u8 key)
drivers/tty/sysrq.c-118-{
drivers/tty/sysrq.c:119:	struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
drivers/tty/sysrq.c-120-
drivers/tty/sysrq.c:121:	schedule_work(SAK_work);
drivers/tty/sysrq.c-122-}
--
drivers/tty/tty_io.c=1489=static void tty_flush_works(struct tty_struct *tty)
drivers/tty/tty_io.c-1490-{
drivers/tty/tty_io.c:1491:	flush_work(&tty->SAK_work);
drivers/tty/tty_io.c-1492-	flush_work(&tty->hangup_work);
drivers/tty/tty_io.c-1493-	if (tty->link) {
drivers/tty/tty_io.c:1494:		flush_work(&tty->link->SAK_work);
drivers/tty/tty_io.c-1495-		flush_work(&tty->link->hangup_work);
--
drivers/tty/tty_io.c=3016=void __do_SAK(struct tty_struct *tty)
--
drivers/tty/tty_io.c-3058-
drivers/tty/tty_io.c:3059:static void do_SAK_work(struct work_struct *work)
drivers/tty/tty_io.c-3060-{
drivers/tty/tty_io.c-3061-	struct tty_struct *tty =
drivers/tty/tty_io.c:3062:		container_of(work, struct tty_struct, SAK_work);
drivers/tty/tty_io.c-3063-	__do_SAK(tty);
--
drivers/tty/tty_io.c-3066-/*
drivers/tty/tty_io.c:3067: * The tq handling here is a little racy - tty->SAK_work may already be queued.
drivers/tty/tty_io.c:3068: * Fortunately we don't need to worry, because if ->SAK_work is already queued,
drivers/tty/tty_io.c-3069- * the values which we write to it will be identical to the values which it
--
drivers/tty/tty_io.c=3072=void do_SAK(struct tty_struct *tty)
--
drivers/tty/tty_io.c-3075-		return;
drivers/tty/tty_io.c:3076:	schedule_work(&tty->SAK_work);
drivers/tty/tty_io.c-3077-}
--
drivers/tty/tty_io.c=3098=struct tty_struct *alloc_tty_struct(struct tty_driver *driver, int idx)
--
drivers/tty/tty_io.c-3125-	INIT_LIST_HEAD(&tty->tty_files);
drivers/tty/tty_io.c:3126:	INIT_WORK(&tty->SAK_work, do_SAK_work);
drivers/tty/tty_io.c-3127-
--
drivers/tty/vt/keyboard.c=634=static void fn_SAK(struct vc_data *vc)
drivers/tty/vt/keyboard.c-635-{
drivers/tty/vt/keyboard.c:636:	struct work_struct *SAK_work = &vc_cons[fg_console].SAK_work;
drivers/tty/vt/keyboard.c:637:	schedule_work(SAK_work);
drivers/tty/vt/keyboard.c-638-}
--
drivers/tty/vt/vt.c=1082=int vc_allocate(unsigned int currcons)	/* return 0 on success */
--
drivers/tty/vt/vt.c-1108-	vc->port.ops = &vc_port_ops;
drivers/tty/vt/vt.c:1109:	INIT_WORK(&vc_cons[currcons].SAK_work, vc_SAK);
drivers/tty/vt/vt.c-1110-
--
drivers/tty/vt/vt.c=3844=static int __init con_init(void)
--
drivers/tty/vt/vt.c-3884-						       GFP_NOWAIT);
drivers/tty/vt/vt.c:3885:		INIT_WORK(&vc_cons[currcons].SAK_work, vc_SAK);
drivers/tty/vt/vt.c-3886-		tty_port_init(&vc->port);
--
drivers/tty/vt/vt_ioctl.c=978=void vc_SAK(struct work_struct *work)
--
drivers/tty/vt/vt_ioctl.c-980-	struct vc *vc_con =
drivers/tty/vt/vt_ioctl.c:981:		container_of(work, struct vc, SAK_work);
drivers/tty/vt/vt_ioctl.c-982-	struct vc_data *vc;
]

gemini-3.1-pro-preview

							input: 16588
							output: 50
							thoughts: 25
						

**My Thought Process Regarding SAK Scheduling**

Alright, so I've just encountered a piece of code, or perhaps a system state, where `do_SAK` is being called. My immediate thought is to dissect this execution flow. I need to understand *why* `do_SAK` is being invoked in the first place. My mental model immediately flags that `do_SAK`'s primary function here is to schedule a `tty->SAK_work` item. This tells me that `do_SAK` isn't the *originating* event, but rather a mechanism to queue up some subsequent asynchronous work related to the terminal (`tty`).

Therefore, my next crucial question, and the core of my current inquiry, is: **What is triggering the call to `do_SAK`?** I'm looking for the caller, the function or event that initiates this sequence. Understanding the context of the `do_SAK` invocation is paramount to grasping the overall system behavior and the implications of this scheduled `SAK_work`. Without knowing *who* is telling `do_SAK` to run, I can't fully comprehend the purpose or the potential impact of the `SAK_work` itself.

map[ContextFile:drivers/tty/tty_io.c IncludeSnippetLines:2 Name:do_SAK SourceTreePrefix:]

map[References:[map[ReferenceKind:calls ReferencingEntityKind:function ReferencingEntityName:uart_handle_break SourceFile:include/linux/serial_core.h SourceLine:1329 SourceSnippet:1327:	#endif
1328:		if (port->flags & UPF_SAK)
1329:			do_SAK(state->port.tty);
1330:		return 0;
1331:	}
] map[ReferenceKind:takes-address-of ReferencingEntityKind:global_variable ReferencingEntityName:__UNIQUE_ID_addressable_do_SAK_1091 SourceFile:drivers/tty/tty_io.c SourceLine:3078 SourceSnippet:3078:	EXPORT_SYMBOL(do_SAK);
] map[ReferenceKind:takes-address-of ReferencingEntityKind:global_variable ReferencingEntityName:__gendwarfksyms_ptr_do_SAK SourceFile:drivers/tty/tty_io.c SourceLine:3078 SourceSnippet:3078:	EXPORT_SYMBOL(do_SAK);
] map[ReferenceKind:takes-address-of ReferencingEntityKind:global_variable ReferencingEntityName:__gendwarfksyms_ptr_do_SAK SourceFile:drivers/tty/tty_io.c SourceLine:3078 SourceSnippet:3078:	EXPORT_SYMBOL(do_SAK);
]] TruncatedOutput:false]

gemini-3.1-pro-preview

							input: 16964
							output: 31
							thoughts: 638
						

**My Thought Process Regarding the SAK Triggering Issue**

I've been digging into this SAK (System Attention Key) handling logic, and it's quite a rabbit hole. My initial understanding was that `uart_handle_break` would directly trigger `do_SAK` if `UPF_SAK` was set. However, that path leads to scheduling `tty->SAK_work`, which then calls `__do_SAK` through `do_SAK_work`. Crucially, I realized that `tty->SAK_work` doesn't acquire the `console_lock`.

The key insight came from examining the provided stack trace. It clearly shows `vc_SAK` calling `__do_SAK` while holding the `console_lock`. This is the critical difference: `vc_SAK` is the function that actually acquires the `console_lock` before proceeding. Therefore, my goal shifted to finding a way to reliably trigger `vc_SAK`.

Now, how does `vc_SAK` get invoked? I found that it's scheduled by either `fn_SAK` in `drivers/tty/vt/keyboard.c` or `sysrq_handle_SAK` in `drivers/tty/sysrq.c`. Given that `/proc/sysrq-trigger` isn't an option in this scenario, I focused on `fn_SAK`, which is triggered by keyboard input.

The next hurdle was figuring out *how* to inject keyboard input that would trigger `fn_SAK`. My first thought was `ioctl(fd, TIOCSTI, &c)`. However, I quickly dismissed this because `TIOCSTI` injects characters directly into the tty input queue, bypassing the keyboard driver entirely, and thus wouldn't trigger the desired keyboard event path.

What I *really* need is to inject a genuine keyboard event. This led me to consider `/dev/uinput`. Using `/dev/uinput`, I can create a virtual keyboard and then send the appropriate key combination. The immediate question then became: what *is* the SAK key combination?

While it's often SysRq + K, I recalled that `fn_SAK` is actually called when a key is mapped to `K_SAK` in the keymap. This opened up another avenue: could I modify the keymap? I considered using `ioctl(fd, KDSKBENT, ...)` to map a key to `K_SAK`, and *then* inject that key using `/dev/uinput`. This seemed like a viable path. I also briefly considered `ioctl(fd, KDSIGACCEPT, ...)` but quickly realized that wasn't the right tool for this job.

At this point, I'm still exploring the possibility of modifying the keymap, but I'm also thinking more broadly. Is there *any other* way to acquire the `console_lock` and then subsequently reach `&buf->lock`? I need to broaden my search and check for alternative code paths that might involve acquiring `console_lock` and then `&buf->lock`, as that might reveal a more direct or simpler triggering mechanism.

map[Expression:tty_buffer_lock_exclusive PathPrefix:drivers/tty/]

map[Output:drivers/tty/tty_buffer.c-43-/**
drivers/tty/tty_buffer.c:44: * tty_buffer_lock_exclusive	-	gain exclusive access to buffer
drivers/tty/tty_buffer.c-45- * @port: tty port owning the flip buffer
--
drivers/tty/tty_buffer.c-52- */
drivers/tty/tty_buffer.c:53:void tty_buffer_lock_exclusive(struct tty_port *port)
drivers/tty/tty_buffer.c-54-{
--
drivers/tty/tty_buffer.c-59-}
drivers/tty/tty_buffer.c:60:EXPORT_SYMBOL_GPL(tty_buffer_lock_exclusive);
drivers/tty/tty_buffer.c-61-
drivers/tty/tty_buffer.c=62=static bool tty_buffer_queue_work(struct tty_bufhead *buf)
--
drivers/tty/tty_buffer.c-74- *
drivers/tty/tty_buffer.c:75: * See also tty_buffer_lock_exclusive().
drivers/tty/tty_buffer.c-76- */
--
drivers/tty/tty_io.c=2272=static int tiocsti(struct tty_struct *tty, u8 __user *p)
--
drivers/tty/tty_io.c-2287-		return -EIO;
drivers/tty/tty_io.c:2288:	tty_buffer_lock_exclusive(tty->port);
drivers/tty/tty_io.c-2289-	if (ld->ops->receive_buf)
--
drivers/tty/vt/selection.c=391=int paste_selection(struct tty_struct *tty)
--
drivers/tty/vt/selection.c-411-		return -EIO;	/* ldisc was hung up */
drivers/tty/vt/selection.c:412:	tty_buffer_lock_exclusive(&vc->port);
drivers/tty/vt/selection.c-413-
]

gemini-3.1-pro-preview

							input: 18137
							output: 51
							thoughts: 193
						

**My Thought Process Regarding `tiocsti` and Lock Ordering**

Alright, let's trace this out. I'm looking at `tiocsti`, and I see it calls `tty_buffer_lock_exclusive(tty->port)`. I know that internally, `tty_buffer_lock_exclusive` acquires the lock associated with the `tty`'s buffer, which is `&buf->lock` (where `buf` is the `tty_buffer`). So, my immediate thought is: does `tiocsti` *also* acquire the `console_lock`? My initial check indicates no, it doesn't seem to directly take or hold `console_lock`.

Then, my mind jumps to `paste_selection`. I recall seeing that `paste_selection` *does* involve `console_lock`. Let's look closer at its code:

```c
	scoped_guard(console_lock) // Acquires console_lock here
		poke_blanked_console();

	ld = tty_ldisc_ref_wait(tty);
	if (!ld)
		return -EIO;	/* ldisc was hung up */
	tty_buffer_lock_exclusive(&vc->port); // And then acquires &buf->lock here
```

Now, I'm analyzing the lock acquisition in `paste_selection`. It first acquires `console_lock`, performs some operations (`poke_blanked_console`), and *then* releases `console_lock` when the `scoped_guard` goes out of scope. *After* that, it proceeds to acquire the exclusive buffer lock (`&buf->lock`) via `tty_buffer_lock_exclusive`. The critical observation here is that `console_lock` and `&buf->lock` are *not held concurrently* within `paste_selection`. One is released before the other is acquired. This means that `paste_selection` itself does *not* establish a lock dependency where `console_lock` must always be held before `&buf->lock` is acquired.

This leads me to my next point of inquiry: what about `tty_buffer_flush`? I need to consider if this function introduces any different lock ordering scenarios that might be relevant to my overall analysis of `tiocsti`.

map[ContextFile:drivers/tty/tty_buffer.c IncludeSnippetLines:2 Name:tty_buffer_flush SourceTreePrefix:]

map[References:[map[ReferenceKind:calls ReferencingEntityKind:function ReferencingEntityName:pty_flush_buffer SourceFile:drivers/tty/pty.c SourceLine:211 SourceSnippet: 209:			return;
 210:	
 211:		tty_buffer_flush(to, NULL);
 212:		if (to->ctrl.packet) {
 213:			guard(spinlock_irq)(&tty->ctrl.lock);
] map[ReferenceKind:calls ReferencingEntityKind:function ReferencingEntityName:tty_ioctl SourceFile:drivers/tty/tty_io.c SourceLine:2775 SourceSnippet:2773:			case TCIOFLUSH:
2774:			/* flush tty buffer and allow ldisc to process ioctl */
2775:				tty_buffer_flush(tty, NULL);
2776:				break;
2777:			}
] map[ReferenceKind:calls ReferencingEntityKind:function ReferencingEntityName:tty_ldisc_flush SourceFile:drivers/tty/tty_ldisc.c SourceLine:388 SourceSnippet: 386:		struct tty_ldisc *ld = tty_ldisc_ref(tty);
 387:	
 388:		tty_buffer_flush(tty, ld);
 389:		if (ld)
 390:			tty_ldisc_deref(ld);
]] TruncatedOutput:false]

gemini-3.1-pro-preview

							input: 18698
							output: 39
							thoughts: 369
						

**My Thought Process Regarding Potential TTY Locking Issues and SysRq Triggering**

My initial line of inquiry focused on the `tty_buffer_flush` function. I established that it's invoked by `tty_ioctl` when the `TCFLSH` (specifically `TCIOFLUSH`) ioctl is used. A critical question then arose: does `tty_ioctl` itself hold the `console_lock`? My understanding is that it does not.

This led me to broaden my search. I needed to determine if there were any *other* execution paths that could concurrently hold the `console_lock` and then subsequently call `tty_buffer_flush`, or related functions like `tty_ldisc_flush` or `tty_buffer_lock_exclusive`. I specifically looked for instances where `console_lock` and `tty_buffer_flush` were mentioned together in the codebase.

However, a thought occurred to me: perhaps there's a simpler way to achieve a similar outcome. I considered using the `ioctl(fd, TIOCLINUX, ...)` command with the `TIOCL_UNBLANKSCREEN` argument. I know that `TIOCL_UNBLANKSCREEN` *does* acquire the `console_lock`. The important distinction here is that it does *not* acquire `&buf->lock`, which was a potential point of contention in other paths.

Then, my attention shifted to the `vc_SAK` function. I recalled that the dependency chain `console_lock` -> `&buf->lock` is explicitly recorded by `vc_SAK`. This sparked a question: if the `/proc/sysrq-trigger` interface isn't available (which might be the case in a restricted environment), how could I possibly trigger `vc_SAK`?

My next idea was to simulate a keyboard input. I reasoned that injecting a keypress might be a viable alternative. The question then became: how could I programmatically inject a keypress? This led me to `/dev/uinput`. I know that `/dev/uinput` is commonly used to create virtual input devices, effectively simulating keyboard and mouse events. I also recalled that syzkaller, a tool I'm familiar with, frequently utilizes `/dev/uinput`.

So, my plan crystallized: I would write a small C program designed to use `/dev/uinput`. This program would create a virtual keyboard and then send the specific key combination for SysRq + K. I double-checked the key codes, confirming that SysRq + K translates to `KEY_SYSRQ` and `KEY_K`.

Finally, I would verify if sending `KEY_SYSRQ` + `KEY_K` via this method indeed triggers the System Request `SAK` behavior. I'd refer to the `drivers/tty/sysrq.c` file for confirmation of this mechanism. The core idea is to find a reliable, if indirect, way to exercise the critical paths and locks involving the TTY subsystem, particularly when direct SysRq triggers might be unavailable.

log-in to see details

map[ContextFile:drivers/tty/sysrq.c Name:sysrq_handle_SAK]

map[SourceCode: SourceFile:]

gemini-3.1-pro-preview

							input: 19111
							output: 31
							thoughts: 30
						

**My Thought Process:**

Okay, so I'm trying to get a handle on this `sysrq_handle_SAK` function. My first instinct, based on the context I'm working with, is that it's likely related to system requests and terminal drivers. A quick mental check—or rather, a quick scan of my internal knowledge base, which is what I'm simulating here—points me to the `drivers/tty/sysrq.c` file. That seems like the most logical place for a function named `sysrq_handle_SAK` to reside, given its name and presumed functionality within the kernel's sysrq subsystem, which fundamentally interacts with terminal devices. So, my immediate next step is to locate this specific function within that particular source file.

map[Expression:sysrq_handle_SAK PathPrefix:drivers/tty/]

map[Output:drivers/tty/sysrq.c=109=static const struct sysrq_key_op sysrq_loglevel_op = {
--
drivers/tty/sysrq.c-116-#ifdef CONFIG_VT
drivers/tty/sysrq.c:117:static void sysrq_handle_SAK(u8 key)
drivers/tty/sysrq.c-118-{
--
drivers/tty/sysrq.c=123=static const struct sysrq_key_op sysrq_SAK_op = {
drivers/tty/sysrq.c:124:	.handler	= sysrq_handle_SAK,
drivers/tty/sysrq.c-125-	.help_msg	= "sak(k)",
]

gemini-3.1-pro-preview

							input: 19348
							output: 16
							thoughts: 561
						

**My Thought Process on Triggering `vc_SAK` via SysRq**

My initial thought is that if `sysrq_handle_SAK` is indeed mapped to the 'k' key, then sending SysRq + 'k' through `/dev/uinput` should be the way to trigger it. I'm already envisioning the sequence: first send an `EV_KEY` event for `KEY_SYSRQ` with a value of 1 (press), followed by an `EV_KEY` event for `KEY_K` with a value of 1.

However, I quickly pause to re-evaluate. The bug report I'm referencing doesn't explicitly state that `sysrq_handle_SAK` was called. Instead, it points to `vc_SAK` being the function that was executed. This is a crucial distinction. I know that `vc_SAK` is the *handler* that gets scheduled, likely by `sysrq_handle_SAK` or another SysRq handler like `fn_SAK`.

Looking at the call trace provided in the bug report further solidifies this:

```
       __do_SAK+0x368/0x480 drivers/tty/tty_io.c:3025
       vc_SAK+0x7f/0x320 drivers/tty/vt/vt_ioctl.c:994
       process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
```

This clearly shows that `vc_SAK` was the function that ran. The question then becomes: how did syzkaller manage to trigger this `vc_SAK`?

I start considering syzkaller's capabilities for interacting with the kernel. It can definitely use `/dev/uinput` for injecting key events, but I also recall it has other mechanisms like `ioctl` calls on TTY devices. Specifically, I'm thinking about `ioctl(fd, KDSKBENT, ...)` and `ioctl(fd, TIOCLINUX, ...)`.

My attention is drawn to `KDSKBENT`. The structure involved, `struct kbentry`, has fields like `kb_table`, `kb_index`, and `kb_value`. This suggests that it's possible to *map* a specific key to an action. If I could map a key to `K_SAK` (the internal symbol for the "Secure Attention Key" functionality), and then somehow simulate a keypress for that mapped key, that would be a viable path.

But how do I simulate a keypress itself? `ioctl(fd, TIOCSTI, &c)` comes to mind, but I immediately dismiss it because it injects a *character*, not a raw keycode event. That's not what I need here; I need to simulate the physical act of pressing a key. `ioctl(fd, VT_RELDISP, 1)` is also a possibility, but it relates to display release, not direct key injection.

I circle back to my initial thought about `/dev/uinput`. Yes, syzkaller *does* use `/dev/uinput` for injecting keycodes. This seems to be the most direct and reliable method for simulating the precise keypresses needed. Therefore, my plan solidifies: I need to craft a `/dev/uinput` snippet that will inject `KEY_SYSRQ` and `KEY_K` to trigger the SysRq functionality that ultimately leads to `vc_SAK` being executed.

map[Name:race]

map[Toolkit:// Copyright 2026 syzkaller project authors. All rights reserved.
// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.

// IMPORTANT: Do not copy the macros or definitions below directly into your reproducer.
// Instead, add the following line to your reproducer:
// #include "race_toolkit.h"

// --- Race Condition Toolkit ---
// Macros and snippets for CPU pinning, memory barriers, and userfaultfd.

#define _GNU_SOURCE
#include <errno.h>
#include <fcntl.h>
#include <linux/futex.h>
#include <linux/userfaultfd.h>
#include <poll.h>
#include <pthread.h>
#include <sched.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <sys/syscall.h>
#include <time.h>
#include <unistd.h>

// Unbuffered I/O: Ensure logs are written immediately.
#define SETUP_UNBUFFERED_IO() setvbuf(stdout, NULL, _IONBF, 0)

// CPU Pinning: Pin the current thread to a specific CPU core.
#define PIN_TO_CPU(cpu)                                                \
	do {                                                           \
		cpu_set_t mask;                                        \
		CPU_ZERO(&mask);                                       \
		CPU_SET(cpu, &mask);                                   \
		if (sched_setaffinity(0, sizeof(mask), &mask) == -1) { \
			perror("sched_setaffinity");                   \
		}                                                      \
	} while (0)

// Memory Barrier: Ensure memory ordering.
#define MB() __atomic_thread_fence(__ATOMIC_SEQ_CST)

// Spin-wait Barrier: Wait until a memory location has a specific value.
// Best for tight race windows (low latency, no context switches).
#define WAIT_ON(addr, val)                                               \
	do {                                                             \
		while (__atomic_load_n(addr, __ATOMIC_ACQUIRE) != (val)) \
			;                                                \
	} while (0)

// Signal: Set a memory location to a specific value to release a WAIT_ON.
#define SIGNAL(addr, val) __atomic_store_n(addr, val, __ATOMIC_RELEASE)

// --- Timing Primitives ---
// Robust timing loops in VM environments (using CLOCK_MONOTONIC to avoid time(NULL) jumps).

static inline double timer_elapsed_sec(struct timespec* start)
{
	struct timespec now;
	if (clock_gettime(CLOCK_MONOTONIC, &now) == -1) {
		perror("clock_gettime(CLOCK_MONOTONIC) elapsed");
		exit(1);
	}
	return (double)(now.tv_sec - start->tv_sec) + (double)(now.tv_nsec - start->tv_nsec) / 1e9;
}

// Initialize a monotonic timer variable.
#define TIMER_START(t)                                          \
	struct timespec t;                                      \
	if (clock_gettime(CLOCK_MONOTONIC, &t) == -1) {         \
		perror("clock_gettime(CLOCK_MONOTONIC) start"); \
		exit(1);                                        \
	}

// Check if the elapsed time since 't' is less than 'sec' seconds.
#define TIMER_NOT_EXPIRED(t, sec) (timer_elapsed_sec(&(t)) < (double)(sec))

// Futex-based Event: Shared with syzkaller executor.
// Best for general synchronization or longer waits to save CPU.
typedef struct {
	int state;
} event_t;

static void event_init(event_t* ev)
{
	ev->state = 0;
}
static void event_reset(event_t* ev)
{
	ev->state = 0;
}

static void event_set(event_t* ev)
{
	if (__atomic_load_n(&ev->state, __ATOMIC_ACQUIRE)) {
		fprintf(stderr, "event already set\n");
		exit(1);
	}
	__atomic_store_n(&ev->state, 1, __ATOMIC_RELEASE);
	syscall(SYS_futex, &ev->state, FUTEX_WAKE | FUTEX_PRIVATE_FLAG, 1000000);
}

static void event_wait(event_t* ev)
{
	while (!__atomic_load_n(&ev->state, __ATOMIC_ACQUIRE))
		syscall(SYS_futex, &ev->state, FUTEX_WAIT | FUTEX_PRIVATE_FLAG, 0, 0);
}

// userfaultfd setup: Register a memory range for page fault handling.
static int setup_uffd(void* addr, size_t len)
{
	int uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
	if (uffd == -1)
		return -1;
	struct uffdio_api api = {.api = UFFD_API, .features = 0};
	if (ioctl(uffd, UFFDIO_API, &api) == -1) {
		close(uffd);
		return -1;
	}
	struct uffdio_register reg = {
	    .range = {.start = (uintptr_t)addr, .len = len},
	    .mode = UFFDIO_REGISTER_MODE_MISSING};
	if (ioctl(uffd, UFFDIO_REGISTER, &reg) == -1) {
		close(uffd);
		return -1;
	}
	return uffd;
}

// --- Guidance on Usage ---
// 1. Use WAIT_ON/SIGNAL for tight race conditions to avoid scheduling overhead.
// 2. Use event_t (futexes) for general coordination or when waiting for longer periods.
// 3. Always use PIN_TO_CPU to increase race probability on multi-core systems.
// 4. Use setup_uffd to register a memory range for page fault handling. This allows you to
//    pause a thread accessing that memory until you handle the fault, creating a reliable
//    and controllable race window.
// 5. Call SETUP_UNBUFFERED_IO() at the start of main() to ensure that logs are printed
//    immediately. This is essential for understanding the exact interleaving of events
//    when debugging race conditions.
// 6. For timing-based loops (e.g., running a race for 10 seconds), do NOT use time(NULL)
//    or loops relying on real-time clocks, as VM clocks are highly unreliable and can fail or drift.
//    Instead, use the robust monotonic timing primitives TIMER_START and TIMER_NOT_EXPIRED:
//        TIMER_START(start);
//        while (TIMER_NOT_EXPIRED(start, 10.0)) {
//            // Your race logic here
//        }
]

gemini-3.1-pro-preview

							input: 21591
							output: 52
							thoughts: 55
						

**A Moment of Clarification in my TTY Driver Debugging**

Alright, so I was deep in the weeds, wrestling with this TTY driver issue, and I had this initial thought, this instinct, that I needed the "race toolkit." You know, the standard suite of tools you might reach for when dealing with concurrency or timing-related problems in drivers. It's a go-to, a reliable first step.

But then, a little voice in my head, or perhaps just a well-honed intuition honed by years of this stuff, whispered a correction. "Hold on a second," I thought. "Do I *really* need the whole race toolkit for this specific problem?" I started to dissect the core of what I was trying to achieve. What was the *actual* action I needed to perform? It wasn't about preempting or synchronizing in a broad sense. It was about triggering a very specific piece of functionality: `vc_SAK`.

This realization shifted my focus dramatically. If my goal is simply to initiate `vc_SAK`, then the overhead and complexity of the full race toolkit might be overkill, or worse, might obscure the direct solution. My thought process then naturally led to a more targeted inquiry: "Is there a more direct way to achieve this? Is there an `ioctl` that *directly* triggers `vc_SAK`?" This felt like a much more elegant and efficient path.

To validate this hypothesis, my next logical step, the one I'm about to embark on, is to dive into the code. Specifically, I need to examine `drivers/tty/vt/vt_ioctl.c`. This is where the TTY ioctl handlers are defined, and I'm confident that if a direct ioctl for `vc_SAK` exists, it will be documented and implemented within this file. This targeted investigation should either confirm my suspicion or guide me to the correct, more direct approach, bypassing the need for the broader race toolkit.

map[ContextFile:drivers/tty/vt/vt_ioctl.c IncludeSnippetLines:2 Name:vc_SAK SourceTreePrefix:]

map[References:[map[ReferenceKind:takes-address-of ReferencingEntityKind:function ReferencingEntityName:con_init SourceFile:drivers/tty/vt/vt.c SourceLine:3885 SourceSnippet:3883:			vc_cons[currcons].d = vc = kzalloc_obj(struct vc_data,
3884:							       GFP_NOWAIT);
3885:			INIT_WORK(&vc_cons[currcons].SAK_work, vc_SAK);
3886:			tty_port_init(&vc->port);
3887:			visual_init(vc, currcons, true);
] map[ReferenceKind:takes-address-of ReferencingEntityKind:function ReferencingEntityName:vc_allocate SourceFile:drivers/tty/vt/vt.c SourceLine:1109 SourceSnippet:1107:		tty_port_init(&vc->port);
1108:		vc->port.ops = &vc_port_ops;
1109:		INIT_WORK(&vc_cons[currcons].SAK_work, vc_SAK);
1110:	
1111:		visual_init(vc, currcons, true);
]] TruncatedOutput:false]

gemini-3.1-pro-preview

							input: 21967
							output: 34
							thoughts: 257
						

**My Thought Process on Triggering SAK**

Right, so my initial thought is that the SAK (Secure Attention Key) functionality, based on these notes, seems to be initialized only during `con_init` and `vc_allocate`. It's also scheduled for execution by both `fn_SAK` and `sysrq_handle_SAK`. This makes me wonder, how exactly can I get `fn_SAK` to trigger?

Digging a bit deeper, I see that `fn_SAK` is invoked by `k_spec` when a specific condition is met: `value == KVAL(K_SAK)`. And `k_spec` itself is called by `kbd_keycode` whenever a special key is pressed. This gives me a potential path forward.

My current hypothesis is that I can leverage the `ioctl(fd, KDSKBENT, ...)` system call to achieve this. The idea is to map a particular keycode to the `K_SAK` keysym. Once that mapping is established, I can then inject that specific key event using `/dev/uinput`.

However, I need to pause and re-evaluate this. `KDSKBENT` is used to map a keycode to a keysym. Let me double-check the structure of `KDSKBENT` to ensure I'm on the right track. Ah, yes, the `struct kbentry` has `kb_table` for the shift state, `kb_index` for the actual keycode, and `kb_value` for the keysym. So, indeed, I'll be targeting the `kb_value` field with `K_SAK`. And for reference, `K_SAK` is clearly defined in `include/uapi/linux/keyboard.h`, which is good to know for the exact value. The overall strategy seems sound: configure a key to represent `K_SAK` and then simulate pressing that key.

map[Expression:K_SAK PathPrefix:include/uapi/linux/keyboard.h]

map[Output:include/uapi/linux/keyboard.h-322-#define K_COMPOSE	K(KT_SPEC,14)
include/uapi/linux/keyboard.h:323:#define K_SAK		K(KT_SPEC,15)
include/uapi/linux/keyboard.h-324-#define K_DECRCONSOLE	K(KT_SPEC,16)
]

gemini-3.1-pro-preview

							input: 22348
							output: 27
							thoughts: 1864
						

**My Thought Process on Triggering a Specific Console Lock Dependency**

My primary objective is to trigger a specific lock dependency: `console_lock` -> `&buf->lock`. I'm analyzing the kernel code to find a path that acquires `console_lock` and subsequently acquires `&buf->lock` while `console_lock` is still held.

Initially, I'm considering ways to simulate a user input that might lead to this. I recall that `K_SAK` (which is defined as `K(KT_SPEC, 15)`, with `KT_SPEC` being `2`, resulting in `0x020F`) is related to the Secure Attention Key mechanism. I know that `KEY_A` (keycode 30) can be mapped to `K_SAK` using `KDSKBENT`.

My first thought is to inject this event. I consider `ioctl(fd, TIOCSTI, ...)`, but quickly realize this only injects characters, not keycodes, so it won't work for simulating a key press.

The more appropriate mechanism for injecting keycodes is through `/dev/uinput`. I decide to write a small C program to create a virtual keyboard using `/dev/uinput` and send the `KEY_A` event mapped to `K_SAK`. This involves setting up the `uinput` device, configuring it for the `KEY_A` event, and then writing the `input_event` structure to simulate a key press and release. I've outlined the necessary steps and the structure of the C code for this approach.

However, as I delve deeper into the kernel's locking behavior, I question if there's a more direct way. I examine the `paste_selection` function, which uses `console_lock`. I note that `paste_selection` releases `console_lock` *before* acquiring `&buf->lock`. This means it *doesn't* establish the `console_lock` -> `&buf->lock` dependency I'm looking for, as lockdep only tracks dependencies when locks are held concurrently.

This leads me back to the `vc_SAK` function. I observe that `vc_SAK` *does* hold `console_lock` before calling `__do_SAK(tty)`. Crucially, `__do_SAK` then calls `tty_buffer_flush(tty, ld)`, which, in turn, acquires `&buf->lock`. This path, `vc_SAK` -> `__do_SAK` -> `tty_buffer_flush`, is the one that establishes the `console_lock` -> `&buf->lock` dependency.

Now, I need to figure out how to trigger `vc_SAK`. I look at its callers: `do_SAK_work` and `sysrq_handle_SAK`. `do_SAK_work` doesn't hold `console_lock`, so that's not the path. My focus shifts to `sysrq_handle_SAK`.

I attempt to trigger `sysrq_handle_SAK` by writing to `/proc/sysrq-trigger`. However, I encounter an error: "failed to open `/proc/sysrq-trigger` (No such file or directory)". This indicates that either `CONFIG_MAGIC_SYSRQ` is disabled, `/proc` is not mounted, or the sandbox environment is preventing access. If `CONFIG_MAGIC_SYSRQ` is disabled, `sysrq_handle_SAK` simply isn't compiled, rendering this path unusable.

Since the `sysrq` route is blocked, I re-evaluate the `vc_SAK` path. I confirm that `fn_SAK` in `drivers/tty/vt/keyboard.c` is compiled if `CONFIG_VT` is enabled, making it a viable alternative. This brings me back to my initial strategy: simulating a key press that `fn_SAK` would handle.

I then perform a broader search within the kernel code for functions that might hold `console_lock` and then acquire `&buf->lock` (or similar buffer locking mechanisms). I look for patterns involving `tty_buffer_lock_exclusive`, `tty_buffer_flush`, or `mutex_lock(&buf->lock)` called within functions that are already holding `console_lock`.

During this review, I consider other `ioctl` commands for the TTY device:
*   `ioctl(fd, TIOCLINUX, ...)`: I check its sub-commands like `TIOCL_PASTESEL`, `TIOCL_SETSEL`, but they don't seem to directly trigger the desired lock order.
*   `ioctl(fd, KDSIGACCEPT, ...)`: This is for signal handling, not keyboard events.
*   `ioctl(fd, VT_RELDISP, ...)`: This relates to display management.
*   `ioctl(fd, KDADDIO, ...)`: This is for adding I/O ports, not event injection.

The `ioctl(fd, TIOCSTI, &c)` function is again considered, but I reiterate that it injects characters directly into the TTY's input buffer, bypassing the keyboard driver and thus not triggering `fn_SAK`.

Ultimately, I conclude that the most reliable method, given the constraints and the analysis of the kernel code, is to use `/dev/uinput` to inject the `KEY_A` event, which should then be processed by the keyboard driver and ultimately lead to `fn_SAK` being called. I also verify that `KDSKBENT` likely requires `CAP_SYS_TTY_CONFIG`, which should be available in the syzkaller sandbox environment running as root. I confirm the structure of `struct kbentry` and the meaning of its fields (`kb_table`, `kb_index`, `kb_value`) to ensure the correct values are used.

map[Expression:console_lock PathPrefix:drivers/tty/]

map[Output:drivers/tty/hvc/hvc_console.c=977=void hvc_remove(struct hvc_struct *hp)
--
drivers/tty/hvc/hvc_console.c-983-
drivers/tty/hvc/hvc_console.c:984:	console_lock();
drivers/tty/hvc/hvc_console.c-985-	spin_lock_irqsave(&hp->lock, flags);
--
drivers/tty/serial/8250/8250_port.c=3288=static void serial8250_console_fifo_write(struct uart_8250_port *up,
--
drivers/tty/serial/8250/8250_port.c-3324- *
drivers/tty/serial/8250/8250_port.c:3325: *	The console_lock must be held when we get here.
drivers/tty/serial/8250/8250_port.c-3326- *
--
drivers/tty/serial/kgdboc.c=193=static int configure_kgdboc(void)
--
drivers/tty/serial/kgdboc.c-223-	/*
drivers/tty/serial/kgdboc.c:224:	 * Take console_lock to serialize device() callback with
drivers/tty/serial/kgdboc.c-225-	 * other console operations. For example, fg_console is
drivers/tty/serial/kgdboc.c:226:	 * modified under console_lock when switching vt.
drivers/tty/serial/kgdboc.c-227-	 */
drivers/tty/serial/kgdboc.c:228:	console_lock();
drivers/tty/serial/kgdboc.c-229-
--
drivers/tty/serial/ma35d1_serial.c=539=static void ma35d1serial_console_putchar(struct uart_port *port, unsigned char ch)
--
drivers/tty/serial/ma35d1_serial.c-550- *
drivers/tty/serial/ma35d1_serial.c:551: *  The console_lock must be held when we get here.
drivers/tty/serial/ma35d1_serial.c-552- */
--
drivers/tty/serial/pch_uart.c=1538=static void pch_console_putchar(struct uart_port *port, unsigned char ch)
--
drivers/tty/serial/pch_uart.c-1550- *
drivers/tty/serial/pch_uart.c:1551: *	The console_lock must be held when we get here.
drivers/tty/serial/pch_uart.c-1552- */
--
drivers/tty/serial/pxa.c=584=static void serial_pxa_console_putchar(struct uart_port *port, unsigned char ch)
--
drivers/tty/serial/pxa.c-595- *
drivers/tty/serial/pxa.c:596: *	The console_lock must be held when we get here.
drivers/tty/serial/pxa.c-597- */
--
drivers/tty/serial/sb1250-duart.c=770=static void __init sbd_probe_duarts(void)
--
drivers/tty/serial/sb1250-duart.c-820- * Serial console stuff.  Very basic, polling driver for doing serial
drivers/tty/serial/sb1250-duart.c:821: * console output.  The console_lock is held by the caller, so we
drivers/tty/serial/sb1250-duart.c-822- * shouldn't be interrupted for more console activity.
--
drivers/tty/serial/serial_core.c=2505=uart_configure_port(struct uart_driver *drv, struct uart_state *state,
--
drivers/tty/serial/serial_core.c-2529-		if (uart_console(port))
drivers/tty/serial/serial_core.c:2530:			console_lock();
drivers/tty/serial/serial_core.c-2531-		port->ops->config_port(port, flags);
--
drivers/tty/serial/serial_core.c-2540-		if (uart_console(port))
drivers/tty/serial/serial_core.c:2541:			console_lock();
drivers/tty/serial/serial_core.c-2542-
--
drivers/tty/serial/serial_txx9.c=833=static void serial_txx9_console_putchar(struct uart_port *up, unsigned char ch)
--
drivers/tty/serial/serial_txx9.c-842- *
drivers/tty/serial/serial_txx9.c:843: *	The console_lock must be held when we get here.
drivers/tty/serial/serial_txx9.c-844- */
--
drivers/tty/tty_io.c=3556=static ssize_t show_cons_active(struct device *dev,
--
drivers/tty/tty_io.c-3584-	/*
drivers/tty/tty_io.c:3585:	 * Take console_lock to serialize device() callback with
drivers/tty/tty_io.c-3586-	 * other console operations. For example, fg_console is
drivers/tty/tty_io.c:3587:	 * modified under console_lock when switching vt.
drivers/tty/tty_io.c-3588-	 */
drivers/tty/tty_io.c:3589:	console_lock();
drivers/tty/tty_io.c-3590-	while (i--) {
--
drivers/tty/vt/consolemap.c-14- * In order to prevent the following circular lock dependency:
drivers/tty/vt/consolemap.c:15: *   &mm->mmap_lock --> cpu_hotplug.lock --> console_lock --> &mm->mmap_lock
drivers/tty/vt/consolemap.c-16- *
drivers/tty/vt/consolemap.c:17: * We cannot allow page fault to happen while holding the console_lock.
drivers/tty/vt/consolemap.c-18- * Therefore, all the userspace copy operations have to be done outside
drivers/tty/vt/consolemap.c:19: * the console_lock critical sections.
drivers/tty/vt/consolemap.c-20- *
--
drivers/tty/vt/consolemap.c=352=int con_set_trans_old(unsigned char __user * arg)
--
drivers/tty/vt/consolemap.c-363-
drivers/tty/vt/consolemap.c:364:	guard(console_lock)();
drivers/tty/vt/consolemap.c-365-	memcpy(translations[USER_MAP], inbuf, sizeof(inbuf));
--
drivers/tty/vt/consolemap.c=371=int con_get_trans_old(unsigned char __user * arg)
--
drivers/tty/vt/consolemap.c-376-
drivers/tty/vt/consolemap.c:377:	scoped_guard(console_lock)
drivers/tty/vt/consolemap.c-378-		for (i = 0; i < ARRAY_SIZE(outbuf); i++) {
--
drivers/tty/vt/consolemap.c=386=int con_set_trans_new(ushort __user * arg)
--
drivers/tty/vt/consolemap.c-392-
drivers/tty/vt/consolemap.c:393:	guard(console_lock)();
drivers/tty/vt/consolemap.c-394-	memcpy(translations[USER_MAP], inbuf, sizeof(inbuf));
--
drivers/tty/vt/consolemap.c=400=int con_get_trans_new(ushort __user * arg)
--
drivers/tty/vt/consolemap.c-403-
drivers/tty/vt/consolemap.c:404:	scoped_guard(console_lock)
drivers/tty/vt/consolemap.c-405-		memcpy(outbuf, translations[USER_MAP], sizeof(outbuf));
--
drivers/tty/vt/consolemap.c=569=int con_clear_unimap(struct vc_data *vc)
drivers/tty/vt/consolemap.c-570-{
drivers/tty/vt/consolemap.c:571:	guard(console_lock)();
drivers/tty/vt/consolemap.c-572-	return con_do_clear_unimap(vc);
--
drivers/tty/vt/consolemap.c=632=int con_set_unimap(struct vc_data *vc, ushort ct, struct unipair __user *list)
--
drivers/tty/vt/consolemap.c-644-
drivers/tty/vt/consolemap.c:645:	guard(console_lock)();
drivers/tty/vt/consolemap.c-646-
--
drivers/tty/vt/consolemap.c=772=int con_get_unimap(struct vc_data *vc, ushort ct, ushort __user *uct,
--
drivers/tty/vt/consolemap.c-782-
drivers/tty/vt/consolemap.c:783:	scoped_guard(console_lock) {
drivers/tty/vt/consolemap.c-784-		ect = 0;
--
drivers/tty/vt/selection.c=123=int sel_loadlut(u32 __user *lut)
--
drivers/tty/vt/selection.c-129-
drivers/tty/vt/selection.c:130:	guard(console_lock)();
drivers/tty/vt/selection.c-131-	memcpy(inwordLut, tmplut, sizeof(inwordLut));
--
drivers/tty/vt/selection.c=143=static int store_utf8(u32 c, char *p)
--
drivers/tty/vt/selection.c-182- *
drivers/tty/vt/selection.c:183: * Locking: The entire selection process is managed under the console_lock.
drivers/tty/vt/selection.c-184- * It's a lot under the lock but its hardly a performance path.
--
drivers/tty/vt/selection.c=376=int set_selection_kernel(struct tiocl_selection *v, struct tty_struct *tty)
--
drivers/tty/vt/selection.c-378-	guard(mutex)(&vc_sel.lock);
drivers/tty/vt/selection.c:379:	guard(console_lock)();
drivers/tty/vt/selection.c-380-	return vc_selection(vc_cons[fg_console].d, v, tty);
--
drivers/tty/vt/selection.c=391=int paste_selection(struct tty_struct *tty)
--
drivers/tty/vt/selection.c-405-
drivers/tty/vt/selection.c:406:	scoped_guard(console_lock)
drivers/tty/vt/selection.c-407-		poke_blanked_console();
--
drivers/tty/vt/vc_screen.c=127=vcs_poll_data_get(struct file *file)
--
drivers/tty/vt/vc_screen.c-181- *
drivers/tty/vt/vc_screen.c:182: * Must be called with console_lock.
drivers/tty/vt/vc_screen.c-183- */
drivers/tty/vt/vc_screen.c=184=static struct vc_data *vcs_vc(struct inode *inode, bool *viewed)
--
drivers/tty/vt/vc_screen.c-207- *
drivers/tty/vt/vc_screen.c:208: * Must be called with console_lock.
drivers/tty/vt/vc_screen.c-209- */
--
drivers/tty/vt/vc_screen.c=229=static loff_t vcs_lseek(struct file *file, loff_t offset, int orig)
--
drivers/tty/vt/vc_screen.c-234-
drivers/tty/vt/vc_screen.c:235:	scoped_guard(console_lock) {
drivers/tty/vt/vc_screen.c-236-		vc = vcs_vc(inode, NULL);
--
drivers/tty/vt/vc_screen.c=364=vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
--
drivers/tty/vt/vc_screen.c-382-	 */
drivers/tty/vt/vc_screen.c:383:	guard(console_lock)();
drivers/tty/vt/vc_screen.c-384-
--
drivers/tty/vt/vc_screen.c-453-		ret = copy_to_user(buf, con_buf + skip, this_round);
drivers/tty/vt/vc_screen.c:454:		console_lock();
drivers/tty/vt/vc_screen.c-455-
--
drivers/tty/vt/vc_screen.c=585=vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
--
drivers/tty/vt/vc_screen.c-607-	 */
drivers/tty/vt/vc_screen.c:608:	guard(console_lock)();
drivers/tty/vt/vc_screen.c-609-
--
drivers/tty/vt/vc_screen.c-633-		ret = copy_from_user(con_buf, buf, this_round);
drivers/tty/vt/vc_screen.c:634:		console_lock();
drivers/tty/vt/vc_screen.c-635-
--
drivers/tty/vt/vc_screen.c=736=vcs_open(struct inode *inode, struct file *filp)
--
drivers/tty/vt/vc_screen.c-745-
drivers/tty/vt/vc_screen.c:746:	guard(console_lock)();
drivers/tty/vt/vc_screen.c-747-
--
drivers/tty/vt/vt.c-62- *
drivers/tty/vt/vt.c:63: * Removed console_lock, enabled interrupts across all console operations
drivers/tty/vt/vt.c-64- * 13 March 2001, Andrew Morton
--
drivers/tty/vt/vt.c=1346=static int vt_resize(struct tty_struct *tty, struct winsize *ws)
--
drivers/tty/vt/vt.c-1349-
drivers/tty/vt/vt.c:1350:	guard(console_lock)();
drivers/tty/vt/vt.c-1351-	return vc_do_resize(tty, vc, ws->ws_col, ws->ws_row, false);
--
drivers/tty/vt/vt.c=1715=enum {
--
drivers/tty/vt/vt.c-1748-
drivers/tty/vt/vt.c:1749:/* console_lock is held */
drivers/tty/vt/vt.c-1750-static void csi_m(struct vc_data *vc)
--
drivers/tty/vt/vt.c=1905=static int get_bracketed_paste(struct tty_struct *tty)
--
drivers/tty/vt/vt.c-1911-
drivers/tty/vt/vt.c:1912:/* console_lock is held */
drivers/tty/vt/vt.c-1913-static void enter_alt_screen(struct vc_data *vc)
--
drivers/tty/vt/vt.c-1930-
drivers/tty/vt/vt.c:1931:/* console_lock is held */
drivers/tty/vt/vt.c-1932-static void leave_alt_screen(struct vc_data *vc)
--
drivers/tty/vt/vt.c=1973=enum {
--
drivers/tty/vt/vt.c-1986-
drivers/tty/vt/vt.c:1987:/* console_lock is held */
drivers/tty/vt/vt.c-1988-static void csi_DEC_hl(struct vc_data *vc, bool on_off)
--
drivers/tty/vt/vt.c=2049=enum {
--
drivers/tty/vt/vt.c-2054-
drivers/tty/vt/vt.c:2055:/* console_lock is held */
drivers/tty/vt/vt.c-2056-static void csi_hl(struct vc_data *vc, bool on_off)
--
drivers/tty/vt/vt.c=2077=enum CSI_right_square_bracket {
--
drivers/tty/vt/vt.c-2095- *
drivers/tty/vt/vt.c:2096: * console_lock is held
drivers/tty/vt/vt.c-2097- */
drivers/tty/vt/vt.c=2098=static void csi_RSB(struct vc_data *vc)
--
drivers/tty/vt/vt.c-2161-
drivers/tty/vt/vt.c:2162:/* console_lock is held */
drivers/tty/vt/vt.c-2163-static void csi_at(struct vc_data *vc, unsigned int nr)
--
drivers/tty/vt/vt.c-2168-
drivers/tty/vt/vt.c:2169:/* console_lock is held */
drivers/tty/vt/vt.c-2170-static void csi_L(struct vc_data *vc)
--
drivers/tty/vt/vt.c-2177-
drivers/tty/vt/vt.c:2178:/* console_lock is held */
drivers/tty/vt/vt.c-2179-static void csi_P(struct vc_data *vc)
--
drivers/tty/vt/vt.c-2185-
drivers/tty/vt/vt.c:2186:/* console_lock is held */
drivers/tty/vt/vt.c-2187-static void csi_M(struct vc_data *vc)
--
drivers/tty/vt/vt.c-2194-
drivers/tty/vt/vt.c:2195:/* console_lock is held (except via vc_init->reset_terminal */
drivers/tty/vt/vt.c-2196-static void save_cur(struct vc_data *vc)
--
drivers/tty/vt/vt.c-2200-
drivers/tty/vt/vt.c:2201:/* console_lock is held */
drivers/tty/vt/vt.c-2202-static void restore_cur(struct vc_data *vc)
--
drivers/tty/vt/vt.c=2236=enum vc_ctl_state {
--
drivers/tty/vt/vt.c-2257-
drivers/tty/vt/vt.c:2258:/* console_lock is held (except via vc_init()) */
drivers/tty/vt/vt.c-2259-static void reset_terminal(struct vc_data *vc, int do_clear)
--
drivers/tty/vt/vt.c=2682=static void vc_reset_params(struct vc_data *vc)
--
drivers/tty/vt/vt.c-2687-
drivers/tty/vt/vt.c:2688:/* console_lock is held */
drivers/tty/vt/vt.c-2689-static void do_con_trol(struct tty_struct *tty, struct vc_data *vc, u8 c)
--
drivers/tty/vt/vt.c=3192=static int vc_con_write_normal(struct vc_data *vc, int tc, int c,
--
drivers/tty/vt/vt.c-3274-
drivers/tty/vt/vt.c:3275:/* acquires console_lock */
drivers/tty/vt/vt.c-3276-static int do_con_write(struct tty_struct *tty, const u8 *buf, int count)
--
drivers/tty/vt/vt.c-3289-
drivers/tty/vt/vt.c:3290:	guard(console_lock)();
drivers/tty/vt/vt.c-3291-	currcons = vc->vc_num;
--
drivers/tty/vt/vt.c-3347- * with other console code and prevention of re-entrancy is
drivers/tty/vt/vt.c:3348: * ensured with console_lock.
drivers/tty/vt/vt.c-3349- */
drivers/tty/vt/vt.c=3350=static void console_callback(struct work_struct *ignored)
drivers/tty/vt/vt.c-3351-{
drivers/tty/vt/vt.c:3352:	guard(console_lock)();
drivers/tty/vt/vt.c-3353-
--
drivers/tty/vt/vt.c=3535=static struct console vt_console_driver = {
--
drivers/tty/vt/vt.c-3550-/*
drivers/tty/vt/vt.c:3551: * Generally a bit racy with respect to console_lock();.
drivers/tty/vt/vt.c-3552- *
--
drivers/tty/vt/vt.c=3561=int tioclinux(struct tty_struct *tty, unsigned long arg)
--
drivers/tty/vt/vt.c-3583-	case TIOCL_UNBLANKSCREEN:
drivers/tty/vt/vt.c:3584:		scoped_guard(console_lock)
drivers/tty/vt/vt.c-3585-			unblank_screen();
--
drivers/tty/vt/vt.c-3600-	case TIOCL_GETMOUSEREPORTING:
drivers/tty/vt/vt.c:3601:		scoped_guard(console_lock)	/* May be overkill */
drivers/tty/vt/vt.c-3602-			data = mouse_reporting();
--
drivers/tty/vt/vt.c-3632-		 */
drivers/tty/vt/vt.c:3633:		scoped_guard(console_lock)
drivers/tty/vt/vt.c-3634-			scrollfront(vc_cons[fg_console].d, lines);
--
drivers/tty/vt/vt.c-3636-	case TIOCL_BLANKSCREEN:	/* until explicitly unblanked, not only poked */
drivers/tty/vt/vt.c:3637:		scoped_guard(console_lock) {
drivers/tty/vt/vt.c-3638-			ignore_poke = 1;
--
drivers/tty/vt/vt.c=3723=static void con_flush_chars(struct tty_struct *tty)
--
drivers/tty/vt/vt.c-3729-
drivers/tty/vt/vt.c:3730:	guard(console_lock)();
drivers/tty/vt/vt.c-3731-	set_cursor(vc);
--
drivers/tty/vt/vt.c=3737=static int con_install(struct tty_driver *driver, struct tty_struct *tty)
--
drivers/tty/vt/vt.c-3742-
drivers/tty/vt/vt.c:3743:	guard(console_lock)();
drivers/tty/vt/vt.c-3744-	ret = vc_allocate(currcons);
--
drivers/tty/vt/vt.c=3786=static void con_shutdown(struct tty_struct *tty)
--
drivers/tty/vt/vt.c-3790-
drivers/tty/vt/vt.c:3791:	guard(console_lock)();
drivers/tty/vt/vt.c-3792-	vc->port.tty = NULL;
--
drivers/tty/vt/vt.c=3844=static int __init con_init(void)
--
drivers/tty/vt/vt.c-3849-
drivers/tty/vt/vt.c:3850:	console_lock();
drivers/tty/vt/vt.c-3851-
--
drivers/tty/vt/vt.c=4273=static ssize_t store_bind(struct device *dev, struct device_attribute *attr,
--
drivers/tty/vt/vt.c-4278-
drivers/tty/vt/vt.c:4279:	guard(console_lock)();
drivers/tty/vt/vt.c-4280-
--
drivers/tty/vt/vt.c=4289=static ssize_t show_bind(struct device *dev, struct device_attribute *attr,
--
drivers/tty/vt/vt.c-4294-
drivers/tty/vt/vt.c:4295:	scoped_guard(console_lock)
drivers/tty/vt/vt.c-4296-		bind = con_is_bound(con->con);
--
drivers/tty/vt/vt.c=4543=static void con_driver_unregister_callback(struct work_struct *ignored)
--
drivers/tty/vt/vt.c-4546-
drivers/tty/vt/vt.c:4547:	guard(console_lock)();
drivers/tty/vt/vt.c-4548-
--
drivers/tty/vt/vt.c-4559-
drivers/tty/vt/vt.c:4560:		console_lock();
drivers/tty/vt/vt.c-4561-
--
drivers/tty/vt/vt.c=4605=void give_up_console(const struct consw *csw)
drivers/tty/vt/vt.c-4606-{
drivers/tty/vt/vt.c:4607:	guard(console_lock)();
drivers/tty/vt/vt.c-4608-	do_unregister_con_driver(csw);
--
drivers/tty/vt/vt.c=4649=static int set_vesa_blanking(u8 __user *mode_user)
--
drivers/tty/vt/vt.c-4655-
drivers/tty/vt/vt.c:4656:	guard(console_lock)();
drivers/tty/vt/vt.c-4657-	vesa_blank_mode = (mode <= VESA_BLANK_MAX) ? mode : VESA_NO_BLANKING;
--
drivers/tty/vt/vt.c=4835=int con_set_cmap(unsigned char __user *arg)
--
drivers/tty/vt/vt.c-4842-
drivers/tty/vt/vt.c:4843:	guard(console_lock)();
drivers/tty/vt/vt.c-4844-	for (i = k = 0; i < 16; i++) {
--
drivers/tty/vt/vt.c=4863=int con_get_cmap(unsigned char __user *arg)
--
drivers/tty/vt/vt.c-4867-
drivers/tty/vt/vt.c:4868:	scoped_guard(console_lock)
drivers/tty/vt/vt.c-4869-		for (i = k = 0; i < 16; i++) {
--
drivers/tty/vt/vt.c=4910=static int con_font_get(struct vc_data *vc, struct console_font_op *op)
--
drivers/tty/vt/vt.c-4926-
drivers/tty/vt/vt.c:4927:	scoped_guard(console_lock) {
drivers/tty/vt/vt.c-4928-		if (vc->vc_mode != KD_TEXT)
--
drivers/tty/vt/vt.c=4955=static int con_font_set(struct vc_data *vc, const struct console_font_op *op)
--
drivers/tty/vt/vt.c-4981-
drivers/tty/vt/vt.c:4982:	guard(console_lock)();
drivers/tty/vt/vt.c-4983-
--
drivers/tty/vt/vt.c=4995=static int con_font_default(struct vc_data *vc, struct console_font_op *op)
--
drivers/tty/vt/vt.c-5007-
drivers/tty/vt/vt.c:5008:	scoped_guard(console_lock) {
drivers/tty/vt/vt.c-5009-		if (vc->vc_mode != KD_TEXT)
--
drivers/tty/vt/vt_ioctl.c=44=static inline bool vt_in_use(unsigned int i)
--
drivers/tty/vt/vt_ioctl.c-48-	/*
drivers/tty/vt/vt_ioctl.c:49:	 * console_lock must be held to prevent the vc from being deallocated
drivers/tty/vt/vt_ioctl.c-50-	 * while we're checking whether it's in-use.
--
drivers/tty/vt/vt_ioctl.c=283=static int vt_k_ioctl(struct tty_struct *tty, unsigned int cmd,
--
drivers/tty/vt/vt_ioctl.c-379-
drivers/tty/vt/vt_ioctl.c:380:		guard(console_lock)();
drivers/tty/vt/vt_ioctl.c-381-		return vt_kdsetmode(vc, arg);
--
drivers/tty/vt/vt_ioctl.c=589=static int vt_setactivate(struct vt_setactivate __user *sa)
--
drivers/tty/vt/vt_ioctl.c-601-	vsa.console = array_index_nospec(vsa.console, MAX_NR_CONSOLES);
drivers/tty/vt/vt_ioctl.c:602:	scoped_guard(console_lock) {
drivers/tty/vt/vt_ioctl.c-603-		ret = vc_allocate(vsa.console);
--
drivers/tty/vt/vt_ioctl.c=626=static int vt_disallocate(unsigned int vc_num)
--
drivers/tty/vt/vt_ioctl.c-629-
drivers/tty/vt/vt_ioctl.c:630:	scoped_guard(console_lock) {
drivers/tty/vt/vt_ioctl.c-631-		if (vt_busy(vc_num))
--
drivers/tty/vt/vt_ioctl.c=644=static void vt_disallocate_all(void)
--
drivers/tty/vt/vt_ioctl.c-648-
drivers/tty/vt/vt_ioctl.c:649:	scoped_guard(console_lock)
drivers/tty/vt/vt_ioctl.c-650-		for (i = 1; i < MAX_NR_CONSOLES; i++)
--
drivers/tty/vt/vt_ioctl.c=662=static int vt_resizex(struct vc_data *vc, struct vt_consize __user *cs)
--
drivers/tty/vt/vt_ioctl.c-699-			continue;
drivers/tty/vt/vt_ioctl.c:700:		guard(console_lock)();
drivers/tty/vt/vt_ioctl.c-701-		vcp = vc_cons[i].d;
--
drivers/tty/vt/vt_ioctl.c=727=int vt_ioctl(struct tty_struct *tty,
--
drivers/tty/vt/vt_ioctl.c-764-
drivers/tty/vt/vt_ioctl.c:765:		guard(console_lock)();
drivers/tty/vt/vt_ioctl.c-766-		vc->vt_mode = tmp;
--
drivers/tty/vt/vt_ioctl.c-780-
drivers/tty/vt/vt_ioctl.c:781:		scoped_guard(console_lock)
drivers/tty/vt/vt_ioctl.c-782-			memcpy(&tmp, &vc->vt_mode, sizeof(struct vt_mode));
--
drivers/tty/vt/vt_ioctl.c-803-		state = 1;	/* /dev/tty0 is always open */
drivers/tty/vt/vt_ioctl.c:804:		scoped_guard(console_lock) /* required by vt_in_use() */
drivers/tty/vt/vt_ioctl.c-805-			for (i = 0, mask = 2; i < MAX_NR_CONSOLES && mask; ++i, mask <<= 1)
--
drivers/tty/vt/vt_ioctl.c-814-	case VT_OPENQRY:
drivers/tty/vt/vt_ioctl.c:815:		scoped_guard(console_lock) /* required by vt_in_use() */
drivers/tty/vt/vt_ioctl.c-816-			for (i = 0; i < MAX_NR_CONSOLES; ++i)
--
drivers/tty/vt/vt_ioctl.c-834-		arg = array_index_nospec(arg, MAX_NR_CONSOLES);
drivers/tty/vt/vt_ioctl.c:835:		scoped_guard(console_lock) {
drivers/tty/vt/vt_ioctl.c-836-			ret = vc_allocate(arg);
--
drivers/tty/vt/vt_ioctl.c-873-
drivers/tty/vt/vt_ioctl.c:874:		guard(console_lock)();
drivers/tty/vt/vt_ioctl.c-875-		return vt_reldisp(vc, arg);
--
drivers/tty/vt/vt_ioctl.c-904-
drivers/tty/vt/vt_ioctl.c:905:		guard(console_lock)();
drivers/tty/vt/vt_ioctl.c-906-		for (i = 0; i < MAX_NR_CONSOLES; i++) {
--
drivers/tty/vt/vt_ioctl.c-944-
drivers/tty/vt/vt_ioctl.c:945:		console_lock();
drivers/tty/vt/vt_ioctl.c-946-		concsr.con_cols = vc->vc_cols;
--
drivers/tty/vt/vt_ioctl.c=978=void vc_SAK(struct work_struct *work)
--
drivers/tty/vt/vt_ioctl.c-984-
drivers/tty/vt/vt_ioctl.c:985:	guard(console_lock)();
drivers/tty/vt/vt_ioctl.c-986-	vc = vc_con->d;
--
drivers/tty/vt/vt_ioctl.c=1269=int vt_move_to_console(unsigned int vt, int alloc)
--
drivers/tty/vt/vt_ioctl.c-1272-
drivers/tty/vt/vt_ioctl.c:1273:	scoped_guard(console_lock) {
drivers/tty/vt/vt_ioctl.c-1274-		/* Graphics mode - up to X */
--
drivers/tty/vt/vt_ioctl.c=1310=void pm_set_vt_switch(int do_switch)
drivers/tty/vt/vt_ioctl.c-1311-{
drivers/tty/vt/vt_ioctl.c:1312:	guard(console_lock)();
drivers/tty/vt/vt_ioctl.c-1313-	disable_vt_switch = !do_switch;
]

gemini-3.1-pro-preview

							input: 33372
							output: 36
							thoughts: 1357
						

**My Thought Process on Triggering a Specific Kernel Lock Sequence**

Right, so my primary objective here is to trigger a particular sequence of lock acquisitions: `&tty->termios_rwsem` -> `&port->mutex` -> `console_lock` -> `&buf->lock` -> `&tty->termios_rwsem`. I've been dissecting the kernel's console and TTY handling code to figure out the exact path.

I've identified that `vc_SAK` is the critical function that takes `console_lock` and then subsequently acquires `&buf->lock` via its internal call to `__do_SAK`. This means my strategy *must* involve triggering `vc_SAK`.

Since I don't have direct access to `/proc/sysrq-trigger` (which would be the straightforward way to invoke `sysrq_handle_SAK` and thus `vc_SAK`), I need an alternative. My current best bet is to trigger `fn_SAK`, which in turn calls `vc_SAK`. The established method for triggering `fn_SAK` is by combining `KDSKBENT` with `/dev/uinput`.

I've double-checked if there are any other routes to `vc_SAK`. Based on my analysis, `vc_SAK` is solely scheduled by `fn_SAK` and `sysrq_handle_SAK`. So, yes, the `KDSKBENT` + `/dev/uinput` approach seems to be the only viable path to get `vc_SAK` running without `/proc/sysrq-trigger`.

With that established, I've drafted a reproducer C code. Let me walk through the logic of the reproducer:

1.  **Triggering `&tty->termios_rwsem` -> `&port->mutex`:**
    I'm opening `/dev/ttyS0` and performing a `TCGETS` followed by `TCSETS`. This sequence, particularly the `TCGETS`, is known to acquire `&tty->termios_rwsem` and then `&port->mutex` within the TTY driver's implementation.

2.  **Triggering `console_lock` -> `&buf->lock` (via `vc_SAK`):**
    This is the core part.
    *   First, I use `KDSKBENT` on `/dev/tty1`. I'm mapping the keycode for 'A' (index 30) to the `K_SAK` key value (`0x020F`). This setup primes the system for the System Attention Key (SAK) event.
    *   Then, I use `/dev/uinput` to inject a `KEY_A` event. This simulated key press will be interpreted by the kernel as a SAK event, triggering `fn_SAK` and subsequently `vc_SAK`. As established, `vc_SAK` will then acquire `console_lock` and `&buf->lock`.

3.  **Triggering `&buf->lock` -> `&tty->termios_rwsem`:**
    This final step in the lock acquisition chain is a bit more indirect. I'm utilizing `/dev/ptmx` to create a pseudo-terminal pair. By writing to the slave PTY (`pts`), I force a `flush_to_ldisc` operation on the master PTY. This operation, when it attempts to flush data, will acquire `&buf->lock` and then, in its path, will attempt to acquire `&tty->termios_rwsem` on the master side.

So, the reproducer is designed to execute these three distinct steps sequentially, each aiming to acquire a specific lock in the chain, ultimately to achieve the full nested lock acquisition.

Now, I'm pondering if there are any *other* ways to reach that `console_lock` -> `&buf->lock` transition, specifically. What if other TTY ioctls, like `TIOCL_SETSEL` or something similar, also grab `console_lock` before ultimately needing `&buf->lock`? I decided to investigate `set_selection_kernel`. Looking at its implementation, it uses `guard(mutex)(&vc_sel.lock)` and then `guard(console_lock)()`. This looks promising. The question then becomes: does `vc_selection` (which `set_selection_kernel` calls) subsequently acquire `&buf->lock`? I need to dive into `vc_selection`'s code to confirm that. If it does, then `TIOCL_SETSEL` could be another avenue to trigger that part of the lock sequence. But for now, the `KDSKBENT` + `/dev/uinput` route is confirmed and is the focus of my current reproducer.

map[ContextFile:drivers/tty/vt/selection.c Name:vc_selection]

map[SourceCode: 338:	static int vc_selection(struct vc_data *vc, struct tiocl_selection *v,
 339:			struct tty_struct *tty)
 340:	{
 341:		int ps, pe;
 342:	
 343:		poke_blanked_console();
 344:	
 345:		if (v->sel_mode == TIOCL_SELCLEAR) {
 346:			/* useful for screendump without selection highlights */
 347:			clear_selection();
 348:			return 0;
 349:		}
 350:	
 351:		/* Historically 0 => max value */
 352:		v->xs = umin(v->xs - 1, vc->vc_cols - 1);
 353:		v->ys = umin(v->ys - 1, vc->vc_rows - 1);
 354:		v->xe = umin(v->xe - 1, vc->vc_cols - 1);
 355:		v->ye = umin(v->ye - 1, vc->vc_rows - 1);
 356:	
 357:		if (mouse_reporting() && (v->sel_mode & TIOCL_SELMOUSEREPORT)) {
 358:			mouse_report(tty, v->sel_mode & TIOCL_SELBUTTONMASK, v->xs,
 359:				     v->ys);
 360:			return 0;
 361:		}
 362:	
 363:		ps = v->ys * vc->vc_size_row + (v->xs << 1);
 364:		pe = v->ye * vc->vc_size_row + (v->xe << 1);
 365:		if (ps > pe)	/* make vc_sel.start <= vc_sel.end */
 366:			swap(ps, pe);
 367:	
 368:		if (vc_sel.cons != vc) {
 369:			clear_selection();
 370:			vc_sel.cons = vc;
 371:		}
 372:	
 373:		return vc_do_selection(vc, v->sel_mode, ps, pe);
 374:	}
 SourceFile:drivers/tty/vt/selection.c]

gemini-3.1-pro-preview

							input: 35388
							output: 36
							thoughts: 32
						

**My Thought Process on Function Argument Checking**

Okay, so my primary line of inquiry right now is about how these two functions, `vc_do_selection` and `mouse_report`, handle the buffer lock. Specifically, I need to confirm whether they are designed to accept `&buf->lock` as an argument.

My immediate instinct is to start by examining `mouse_report`. This seems like a logical first step because mouse input handling often involves direct manipulation or immediate feedback on the buffer state, making it a likely candidate to require explicit lock management. I'm going to dive into the implementation details of `mouse_report` to see if `&buf->lock` is present in its signature or if there's any other mechanism for lock acquisition/release related to buffer operations within that function. Once I have a clear understanding of `mouse_report`'s lock handling, I'll then move on to `vc_do_selection` to perform a similar analysis.

map[ContextFile:drivers/tty/vt/selection.c Name:mouse_report]

map[SourceCode:1888:	void mouse_report(struct tty_struct *tty, int butt, int mrx, int mry)
1889:	{
1890:		char buf[8];
1891:		int len;
1892:	
1893:		len = sprintf(buf, "\033[M%c%c%c", (char)(' ' + butt),
1894:				(char)('!' + mrx), (char)('!' + mry));
1895:		respond_string(buf, len, tty->port);
1896:	}
 SourceFile:drivers/tty/vt/vt.c]

gemini-3.1-pro-preview

							input: 35623
							output: 36
							thoughts: 14
						

**My Thought Process**

Ah, I'm examining the `respond_string` function here. My immediate question is whether it requires access to `&buf->lock`. This is a critical point for me because if it does, it implies a shared mutable state scenario. I need to understand if `respond_string` is going to be directly manipulating or reading a buffer (`buf`) that's protected by a lock, `buf->lock`. If it does, I'll need to ensure that any calls to `respond_string` are properly synchronized, likely by acquiring the lock *before* calling it and releasing it *after*. The implication is that `respond_string` might be performing operations that could lead to race conditions if not properly guarded by that lock. I need to be certain about this dependency to maintain data integrity and prevent concurrent access issues in the system.

map[ContextFile:drivers/tty/vt/vt.c Name:respond_string]

map[SourceCode:1856:	static void respond_string(const char *p, size_t len, struct tty_port *port)
1857:	{
1858:		tty_insert_flip_string(port, p, len);
1859:		tty_flip_buffer_push(port);
1860:	}
 SourceFile:drivers/tty/vt/vt.c]

gemini-3.1-pro-preview

							input: 35770
							output: 40
							thoughts: 79
						

**Aha! My initial observation about `tty_insert_flip_string` accepting `&buf->lock` seems to be correct.**

I'm really pleased to see that `tty_insert_flip_string` indeed takes `&buf->lock`. That was my first hunch, and it's good to confirm it. I then dug a little deeper, following the call stack. My expectation was that `tty_insert_flip_string` would delegate the actual buffer manipulation to another function, and sure enough, it calls `tty_insert_flip_string_fixed_flag`.

Now, the critical part of my investigation was to see if this subsequent function also respected the lock. And yes, it does! `tty_insert_flip_string_fixed_flag` in turn calls `tty_buffer_request_room`, and I've confirmed that this function also operates with `&buf->lock`. This is precisely what I was looking for – a clear indication that the buffer operations are properly synchronized. It gives me confidence that the locking mechanism is being applied consistently throughout the relevant code path for buffer insertion.

map[ContextFile:drivers/tty/vt/vt.c Name:tty_insert_flip_string]

map[SourceCode:  80:	static inline size_t tty_insert_flip_string(struct tty_port *port,
  81:						    const u8 *chars, size_t size)
  82:	{
  83:		return tty_insert_flip_string_fixed_flag(port, chars, TTY_NORMAL, size);
  84:	}
 SourceFile:include/linux/tty_flip.h]

gemini-3.1-pro-preview

							input: 35992
							output: 44
							thoughts: 17
						

**My Thought Process**

Right, so I'm digging into the kernel code here, and I need to understand how character data is being inserted into the TTY buffer. My current focus is on a specific function: `tty_insert_flip_string_fixed_flag`. I need to examine its implementation to grasp the mechanics of this insertion process, particularly how it handles flags that are fixed or pre-determined. This will likely involve looking at how it interacts with the TTY's internal buffer structures and what those "fixed flags" signify in terms of data processing or character attributes.

map[ContextFile:include/linux/tty_flip.h Name:tty_insert_flip_string_fixed_flag]

map[SourceCode:  19:	/**
  20:	 * tty_insert_flip_string_fixed_flag - add characters to the tty buffer
  21:	 * @port: tty port
  22:	 * @chars: characters
  23:	 * @flag: flag value for each character
  24:	 * @size: size
  25:	 *
  26:	 * Queue a series of bytes to the tty buffering. All the characters passed are
  27:	 * marked with the supplied flag.
  28:	 *
  29:	 * Returns: the number added.
  30:	 */
  31:	static inline size_t tty_insert_flip_string_fixed_flag(struct tty_port *port,
  32:							       const u8 *chars, u8 flag,
  33:							       size_t size)
  34:	{
  35:		return __tty_insert_flip_string_flags(port, chars, &flag, false, size);
  36:	}
 SourceFile:include/linux/tty_flip.h]

gemini-3.1-pro-preview

							input: 36323
							output: 43
							thoughts: 16
						

**My Thought Process**

Right, so the immediate impulse is to investigate `__tty_insert_flip_string_flags`. This is where my mind naturally gravitates when I'm looking to understand how string insertion and flipping operations are being handled at the low level within this particular TTY (teletypewriter) subsystem. My expertise tells me that flags like these often dictate crucial behaviors, such as whether the insertion should be immediate, if it should be buffered, how it interacts with existing content, or if there are any special processing requirements. Therefore, digging into the definition and usage of `__tty_insert_flip_string_flags` is the most direct path to comprehending the mechanics of the operation at hand. I need to see what flags are available, what they signify, and how they are being applied in the context of this insertion.

map[ContextFile:include/linux/tty_flip.h Name:__tty_insert_flip_string_flags]

map[SourceCode: 307:	size_t __tty_insert_flip_string_flags(struct tty_port *port, const u8 *chars,
 308:					      const u8 *flags, bool mutable_flags,
 309:					      size_t size)
 310:	{
 311:		bool need_flags = mutable_flags || flags[0] != TTY_NORMAL;
 312:		size_t copied = 0;
 313:	
 314:		do {
 315:			size_t goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
 316:			size_t space = __tty_buffer_request_room(port, goal, need_flags);
 317:			struct tty_buffer *tb = port->buf.tail;
 318:	
 319:			if (unlikely(space == 0))
 320:				break;
 321:	
 322:			memcpy(char_buf_ptr(tb, tb->used), chars, space);
 323:	
 324:			if (mutable_flags) {
 325:				memcpy(flag_buf_ptr(tb, tb->used), flags, space);
 326:				flags += space;
 327:			} else if (tb->flags) {
 328:				memset(flag_buf_ptr(tb, tb->used), flags[0], space);
 329:			} else {
 330:				/* tb->flags should be available once requested */
 331:				WARN_ON_ONCE(need_flags);
 332:			}
 333:	
 334:			tb->used += space;
 335:			copied += space;
 336:			chars += space;
 337:	
 338:			/* There is a small chance that we need to split the data over
 339:			 * several buffers. If this is the case we must loop.
 340:			 */
 341:		} while (unlikely(size > copied));
 342:	
 343:		return copied;
 344:	}
 SourceFile:drivers/tty/tty_buffer.c]

gemini-3.1-pro-preview

							input: 36965
							output: 41
							thoughts: 19
						

**My Internal Monologue on `__tty_buffer_request_room` and Locking**

Alright, let's dive into this. I'm trying to get a handle on the locking strategy around `__tty_buffer_request_room`. The core question on my mind is: does this function, in its execution, acquire or rely on the `&buf->lock`?

I'm picturing the call path, the data structures involved, and the critical sections. My initial thought is that if `__tty_buffer_request_room` is indeed meant to safely manipulate the buffer's contents or its metadata – things like available space, or perhaps even the pointers within the buffer structure itself – then it *absolutely* needs to be protected by a lock. And given the context, `&buf->lock` seems like the most logical candidate for ensuring serialization of access to that specific buffer.

However, I also need to consider the possibility that the design might be more nuanced. Perhaps `__tty_buffer_request_room` is a lower-level helper that *assumes* it's already being called within a context where the relevant lock is held. Or, it might be that its operations are inherently atomic enough not to require explicit locking *within* the function itself, but rather that the *caller* is responsible for providing that protection.

This leads me to ponder the specific actions `__tty_buffer_request_room` performs. Is it merely checking a count? Is it modifying pointers? Is it allocating or deallocating memory associated with the buffer? The answer to these questions will dictate whether `&buf->lock` is essential. If it's just reading a counter that's updated atomically elsewhere, then maybe not. But if it's touching any shared mutable state that could lead to race conditions with other operations on the same buffer, then yes, `&buf->lock` is crucial.

My mental model is leaning towards the idea that `__tty_buffer_request_room` *should* be operating under the protection of `&buf->lock`. If it doesn't, I'd be concerned about potential race conditions where, for instance, one part of the system is trying to add data while another is trying to free space, leading to inconsistent states or data corruption. The question then becomes: is this an oversight in the current implementation, or is there a deliberate architectural choice being made where the caller is expected to manage the lock? I need to verify this by tracing the callers of `__tty_buffer_request_room` to see how they are acquiring and releasing `&buf->lock` around their calls. This will be key to understanding the intended synchronization mechanism.

map[ContextFile:drivers/tty/tty_buffer.c Name:__tty_buffer_request_room]

map[SourceCode: 254:	/**
 255:	 * __tty_buffer_request_room	-	grow tty buffer if needed
 256:	 * @port: tty port
 257:	 * @size: size desired
 258:	 * @flags: buffer has to store flags along character data
 259:	 *
 260:	 * Make at least @size bytes of linear space available for the tty buffer.
 261:	 *
 262:	 * Will change over to a new buffer if the current buffer is encoded as
 263:	 * %TTY_NORMAL (so has no flags buffer) and the new buffer requires a flags
 264:	 * buffer.
 265:	 *
 266:	 * Returns: the size we managed to find.
 267:	 */
 268:	static int __tty_buffer_request_room(struct tty_port *port, size_t size,
 269:					     bool flags)
 270:	{
 271:		struct tty_bufhead *buf = &port->buf;
 272:		struct tty_buffer *n, *b = buf->tail;
 273:		size_t left = (b->flags ? 1 : 2) * b->size - b->used;
 274:		bool change = !b->flags && flags;
 275:	
 276:		if (!change && left >= size)
 277:			return size;
 278:	
 279:		/* This is the slow path - looking for new buffers to use */
 280:		n = tty_buffer_alloc(port, size);
 281:		if (n == NULL)
 282:			return change ? 0 : left;
 283:	
 284:		n->flags = flags;
 285:		buf->tail = n;
 286:		/*
 287:		 * Paired w/ acquire in flush_to_ldisc() and lookahead_bufs()
 288:		 * ensures they see all buffer data.
 289:		 */
 290:		smp_store_release(&b->commit, b->used);
 291:		/*
 292:		 * Paired w/ acquire in flush_to_ldisc() and lookahead_bufs()
 293:		 * ensures the latest commit value can be read before the head
 294:		 * is advanced to the next buffer.
 295:		 */
 296:		smp_store_release(&b->next, n);
 297:	
 298:		return size;
 299:	}
 SourceFile:drivers/tty/tty_buffer.c]

gemini-3.1-pro-preview

							input: 37732
							output: 1376
							thoughts: 6786
						

**My Thought Process to Uncover a Potential Kernel Race Condition**

Here's a breakdown of my investigation into a potential race condition involving kernel locks:

My primary goal was to identify a sequence of operations that would create a dependency chain of locks: `&tty->termios_rwsem` -> `&port->mutex` -> `&buf->lock` -> `&tty->termios_rwsem`.

1.  **Analyzing `tty_buffer_request_room`:** I started by examining `__tty_buffer_request_room`. My initial thought was that it *must* take `&buf->lock`. However, upon closer inspection, I realized this wasn't the case. I then cross-referenced where `&buf->lock` *is* taken: in `tty_buffer_lock_exclusive`, `tty_buffer_flush`, and `flush_to_ldisc`. Crucially, it's *not* taken in `tty_insert_flip_string`. This immediately told me that `mouse_report`, which I knew called `tty_insert_flip_string`, would *not* be directly involved in taking `&buf->lock` and therefore not a primary path for the dependency.

2.  **Investigating `paste_selection`:** Next, I looked at `paste_selection`. I saw it first takes `console_lock`, releases it, and *then* takes `&buf->lock`. This means `paste_selection` itself doesn't create a *dependency* where one lock is held while another is acquired. It's a sequential acquisition, not a nested one that could lead to a deadlock or race.

3.  **Pinpointing the `console_lock` -> `&buf->lock` Link via `vc_SAK`:** This was the critical breakthrough. I found that `vc_SAK` holds `console_lock` for its entire duration. Inside `vc_SAK`, it calls `__do_SAK(tty)`, which in turn calls `tty_ldisc_flush(tty)`, and finally `tty_buffer_flush(tty, ld)`. And there it is: `tty_buffer_flush` calls `mutex_lock(&buf->lock)`. This is the *only* path I could find that holds `console_lock` and subsequently acquires `&buf->lock`. Therefore, triggering `vc_SAK` became essential to establishing this specific dependency.

4.  **Triggering `vc_SAK`:** I knew `vc_SAK` is scheduled by `fn_SAK` or `sysrq_handle_SAK`.
    *   `/proc/sysrq-trigger` is the most straightforward way, but I couldn't assume its availability.
    *   `fn_SAK` can be triggered via `KDSKBENT` (setting a key to `K_SAK`) combined with injecting that key using `/dev/uinput`. This seemed promising because it doesn't rely on the SysRq functionality being enabled (`CONFIG_MAGIC_SYSRQ`).
    *   I briefly considered other `ioctl` calls (`TIOCLINUX`, `VT_RELDISP`, etc.), but none of them appeared to trigger `vc_SAK`.
    *   Injecting `KEY_SYSRQ` and `KEY_K` was another thought for triggering SysRq, but again, that depends on `CONFIG_MAGIC_SYSRQ`, making the `KDSKBENT` approach more robust.

5.  **Refining the `KDSKBENT` Strategy:**
    *   I confirmed that `KDSKBENT` modifies the global keymap.
    *   I checked the `kbentry` structure and confirmed `kb_table=0`, `kb_index=30` (for `KEY_A`), and `kb_value=0x020F` (for `K_SAK`) would correctly map `KEY_A` to trigger `K_SAK`.
    *   I verified that the `KEY_A` keycode from `linux/input-event-codes.h` (30) directly maps to the `kb_index` in the VT keyboard driver, ensuring the correct key is targeted.
    *   I decided to use `/dev/tty0`, `/dev/tty1`, or `/dev/console` as fallback options for the `KDSKBENT` `ioctl` call, as the specific TTY might vary.

6.  **Constructing the Reproducer:** Based on the above, I assembled the reproducer code, aiming to trigger the dependencies in sequence:
    *   **Step 1: `&tty->termios_rwsem` -> `&port->mutex`**: I used a serial port (`/dev/ttyS0`) and performed `TCGETS` followed by `TCSETS`. This is a known way to acquire `&tty->termios_rwsem` and then `&port->mutex`.
    *   **Step 2: `console_lock` -> `&buf->lock`**: This is where the `KDSKBENT` and `/dev/uinput` magic happens.
        *   I map `KEY_A` to `K_SAK` using `KDSKBENT` on a TTY device.
        *   I then use `/dev/uinput` to create a virtual keyboard, set up the `KEY_A` event, and inject it. This injection causes the system to call `fn_SAK`, which schedules `vc_SAK`.
        *   `vc_SAK` then executes, holding `console_lock` and acquiring `&buf->lock`.
        *   I added `usleep` calls to allow time for workqueues to execute and for the uinput device to be registered.
    *   **Step 3: `&buf->lock` -> `&tty->termios_rwsem`**: I used the classic `/dev/ptmx` and PTY slave mechanism. Writing to the slave PTY triggers `flush_to_ldisc` on the master PTY, which holds `&buf->lock` and then acquires `&tty->termios_rwsem`.

This methodical approach, starting from the problematic lock acquisition and working backward and forward through the code paths, allowed me to isolate the necessary steps and construct a precise reproducer. The key was realizing the unique role of `vc_SAK` in linking `console_lock` to `&buf->lock` and finding a reliable, configuration-independent way to trigger it.

map[CurrentReproStrategy:To trigger the `console_lock` -> `&buf->lock` dependency without relying on `/proc/sysrq-trigger` (which might be disabled or restricted), we can use the VT keyboard driver. 

The function `vc_SAK` takes `console_lock` and then calls `__do_SAK`, which takes `&buf->lock`. `vc_SAK` is scheduled by `fn_SAK`, which is triggered when the keyboard driver receives a key mapped to the `K_SAK` keysym. 

We can dynamically map a normal key (e.g., `KEY_A`) to `K_SAK` using the `KDSKBENT` ioctl on a VT device (like `/dev/tty0`). Then, we can inject a `KEY_A` keypress using a virtual input device via `/dev/uinput`. This will simulate the SAK key combination and execute `vc_SAK`, recording the required lock dependency.

### Minimal C Reproducer

```c
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <stdlib.h>
#include <linux/kd.h>
#include <linux/uinput.h>
#include <string.h>
#include <stdio.h>

int main(void) {
    // 1. Trigger: &tty->termios_rwsem -> &port->mutex
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial >= 0) {
        struct termios term;
        if (ioctl(fd_serial, TCGETS, &term) == 0) {
            ioctl(fd_serial, TCSETS, &term);
        }
        close(fd_serial);
    }

    // 2. Trigger: console_lock -> &buf->lock
    // Map KEY_A (keycode 30) to K_SAK (0x020F)
    int fd_tty = open("/dev/tty0", O_RDWR);
    if (fd_tty < 0) fd_tty = open("/dev/tty1", O_RDWR);
    if (fd_tty < 0) fd_tty = open("/dev/console", O_RDWR);
    
    if (fd_tty >= 0) {
        struct kbentry ke;
        ke.kb_table = 0;
        ke.kb_index = 30; // KEY_A
        ke.kb_value = 0x020F; // K_SAK
        ioctl(fd_tty, KDSKBENT, &ke);
        close(fd_tty);
    }

    // Inject KEY_A via uinput to trigger fn_SAK -> vc_SAK
    int ufd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
    if (ufd >= 0) {
        ioctl(ufd, UI_SET_EVBIT, EV_KEY);
        ioctl(ufd, UI_SET_KEYBIT, KEY_A);

        struct uinput_setup usetup;
        memset(&usetup, 0, sizeof(usetup));
        usetup.id.bustype = BUS_USB;
        usetup.id.vendor = 0x1234;
        usetup.id.product = 0x5678;
        strcpy(usetup.name, "Virtual Keyboard");
        ioctl(ufd, UI_DEV_SETUP, &usetup);
        ioctl(ufd, UI_DEV_CREATE);

        usleep(100000); // wait for input device to be registered

        struct input_event ie;
        
        // Press KEY_A
        memset(&ie, 0, sizeof(ie));
        ie.type = EV_KEY;
        ie.code = KEY_A;
        ie.value = 1;
        write(ufd, &ie, sizeof(ie));

        memset(&ie, 0, sizeof(ie));
        ie.type = EV_SYN;
        ie.code = SYN_REPORT;
        ie.value = 0;
        write(ufd, &ie, sizeof(ie));

        // Release KEY_A
        memset(&ie, 0, sizeof(ie));
        ie.type = EV_KEY;
        ie.code = KEY_A;
        ie.value = 0;
        write(ufd, &ie, sizeof(ie));

        memset(&ie, 0, sizeof(ie));
        ie.type = EV_SYN;
        ie.code = SYN_REPORT;
        ie.value = 0;
        write(ufd, &ie, sizeof(ie));

        usleep(100000); // wait for vc_SAK workqueue to execute
        ioctl(ufd, UI_DEV_DESTROY);
        close(ufd);
    }

    // 3. Trigger: &buf->lock -> &tty->termios_rwsem
    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx >= 0) {
        grantpt(ptmx);
        unlockpt(ptmx);
        char *pts_name = ptsname(ptmx);
        if (pts_name) {
            int pts = open(pts_name, O_RDWR | O_NOCTTY);
            if (pts >= 0) {
                // Writing to the slave PTY triggers flush_to_ldisc on the master PTY
                write(pts, "a", 1);
                // Wait a bit for the flush_to_ldisc workqueue to execute
                usleep(100000);
                close(pts);
            }
        }
        close(ptmx);
    }

    return 0;
}
```]

best-expensive

map[IsProbe:true RawCandidateReproC:#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>

int main(void) {
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) {
        printf("[-] Failed to open /dev/ttyS0: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/ttyS0.\n");
    close(fd_serial);

    int fd_tty = open("/dev/tty0", O_RDWR);
    if (fd_tty < 0) fd_tty = open("/dev/tty1", O_RDWR);
    if (fd_tty < 0) fd_tty = open("/dev/console", O_RDWR);
    if (fd_tty < 0) {
        printf("[-] Failed to open /dev/tty0, /dev/tty1, and /dev/console: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened a tty/console.\n");
    close(fd_tty);

    int ufd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
    if (ufd < 0) {
        printf("[-] Failed to open /dev/uinput: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/uinput.\n");
    close(ufd);

    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx < 0) {
        printf("[-] Failed to open /dev/ptmx: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/ptmx.\n");
    close(ptmx);

    printf("[+] All probes successful.\n");
    return 0;
}]

You are a security researcher with deep Linux kernel background.
Your goal is to generate a minimal, standalone C program for the strictly defensive
purpose of verifying a bugfix in an isolated environment.

To ensure that we can diagnose why a program might fail to run on the test environment,
you MUST include detailed logging and error checking in the generated C program:
1. Use 'printf(...)' for all progress messages and error logs.
2. Every system call (e.g., socket, bind, listen, connect, ioctl, send) must check for a failure return value.
3. If a call fails, it must print a specific error message including the function name
   and the error string (use strerror(errno)), and then exit with a non-zero status.
4. The program must print a message after every successful major step.
5. Generate code that follows this pattern for all operations:
    int res = do_something();
    if (res < 0) {
        printf("[-] Failed to do_something: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] do_something successful.\n");
6. The compilation and development environment (including compilers, build
   systems, makefiles, and kernel build/header directories) is NOT available
   on the target test VM guest. Do NOT check for, build, or reference any
   compilation tools, build files, or kernel development directories.
7. Do NOT execute shell commands or run external binaries (e.g. by using
   functions like 'system()', 'popen()', or the 'exec' family such as
   'execve()'). All environment checks, capability probings, and reproduction
   steps must be performed directly using standard Linux system calls (such
   as 'open', 'socket', 'ioctl', 'stat', etc.).
8. When reproducing asynchronous kernel timeouts or warnings, always
   include a sufficient delay (using sleep or similar) after deleting
   or unregistering the device to allow the kernel's asynchronous
   timeout to trigger before program exit.


=== PHASE 1: CAPABILITY PROBING (GENERATION) ===
You MUST start by generating a simple 'probe' program first. This is a strict, non-negotiable requirement
to verify that the test environment has the necessary kernel capabilities and privileges.
This program's sole purpose is to verify subsystem availability and privileges by probing specific
device files, subsystems, or syscalls (for example: opening /dev/vhci to check if the virtual
Bluetooth controller is accessible, loading a minimal dummy BPF program, or making a specific
socket/ioctl call).

Print clear messages indicating success or failure of these probes, and exit with 0 only if
all checks pass.
Do NOT attempt complex logic, and do NOT try to trigger the actual bug/crash in this first version,
regardless of how simple the reproducer seems. You must wait until a successful probe run has been
confirmed in the environment (i.e., when CapabilitiesVerified becomes true).

Prefer calling several tools at the same time to save round-trips.


Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.

Bug Description: possible deadlock in n_tty_receive_buf_common

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
kworker/u33:3/62 is trying to acquire lock:
ffff88804b3fe2c8 (&tty->termios_rwsem){++++}-{4:4}, at: class_rwsem_read_constructor include/linux/rwsem.h:259 [inline]
ffff88804b3fe2c8 (&tty->termios_rwsem){++++}-{4:4}, at: n_tty_receive_buf_common+0x85/0x1930 drivers/tty/n_tty.c:1678

but task is already holding lock:
ffff88801404a8b8 (&buf->lock){+.+.}-{4:4}, at: flush_to_ldisc+0x34/0x730 drivers/tty/tty_buffer.c:474

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&buf->lock){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       tty_buffer_flush+0x72/0x310 drivers/tty/tty_buffer.c:236
       tty_ldisc_flush+0xd2/0xf0 drivers/tty/tty_ldisc.c:388
       __do_SAK+0x368/0x480 drivers/tty/tty_io.c:3025
       vc_SAK+0x7f/0x320 drivers/tty/vt/vt_ioctl.c:994
       process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
       process_scheduled_works kernel/workqueue.c:3405 [inline]
       worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
       kthread+0x370/0x450 kernel/kthread.c:436
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #2 (console_lock){+.+.}-{0:0}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       console_lock+0x7a/0xa0 kernel/printk/printk.c:2896
       uart_configure_port drivers/tty/serial/serial_core.c:2530 [inline]
       serial_core_add_one_port drivers/tty/serial/serial_core.c:3101 [inline]
       serial_core_register_port+0xe65/0x16f0 drivers/tty/serial/serial_core.c:3322
       serial8250_register_8250_port+0x15af/0x2330 drivers/tty/serial/8250/8250_core.c:828
       serial_pnp_probe+0x436/0x930 drivers/tty/serial/8250/8250_pnp.c:480
       pnp_device_probe+0x2b3/0x4a0 drivers/pnp/driver.c:111
       call_driver_probe drivers/base/dd.c:628 [inline]
       really_probe+0x241/0xa60 drivers/base/dd.c:706
       __driver_probe_device+0x20e/0x450 drivers/base/dd.c:868
       driver_probe_device+0x4a/0x140 drivers/base/dd.c:898
       __driver_attach+0x21f/0x5b0 drivers/base/dd.c:1292
       bus_for_each_dev+0x13e/0x1d0 drivers/base/bus.c:383
       bus_add_driver+0x305/0x5b0 drivers/base/bus.c:763
       driver_register+0x1e2/0x360 drivers/base/driver.c:174
       serial8250_init+0xcc/0x1c0 drivers/tty/serial/8250/8250_platform.c:317
       do_one_initcall+0x11d/0x700 init/main.c:1347
       do_initcall_level init/main.c:1409 [inline]
       do_initcalls init/main.c:1425 [inline]
       do_basic_setup init/main.c:1445 [inline]
       kernel_init_freeable+0x6ea/0x7b0 init/main.c:1658
       kernel_init+0x1f/0x1e0 init/main.c:1548
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #1 (&port->mutex){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       class_mutex_constructor include/linux/mutex.h:253 [inline]
       uart_set_termios+0x8e/0x690 drivers/tty/serial/serial_core.c:1645
       tty_set_termios+0x64d/0x980 drivers/tty/tty_ioctl.c:341
       set_termios+0x5c8/0x880 drivers/tty/tty_ioctl.c:516
       tty_mode_ioctl+0x17e/0xd40 drivers/tty/tty_ioctl.c:803
       n_tty_ioctl_helper+0x47/0x2b0 drivers/tty/tty_ioctl.c:982
       n_tty_ioctl+0x53/0x340 drivers/tty/n_tty.c:2496
       tty_ioctl+0x11b4/0x1640 drivers/tty/tty_io.c:2801
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl fs/ioctl.c:583 [inline]
       __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x115/0x840 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&tty->termios_rwsem){++++}-{4:4}:
       check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       down_read+0x99/0x4c0 kernel/locking/rwsem.c:1574
       class_rwsem_read_constructor include/linux/rwsem.h:259 [inline]
       n_tty_receive_buf_common+0x85/0x1930 drivers/tty/n_tty.c:1678
       tty_ldisc_receive_buf+0xaa/0x1a0 drivers/tty/tty_buffer.c:394
       tty_port_default_receive_buf+0x70/0xb0 drivers/tty/tty_port.c:37
       receive_buf drivers/tty/tty_buffer.c:452 [inline]
       flush_to_ldisc+0x26b/0x730 drivers/tty/tty_buffer.c:502
       process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
       process_scheduled_works kernel/workqueue.c:3405 [inline]
       worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
       kthread+0x370/0x450 kernel/kthread.c:436
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

other info that might help us debug this:

Chain exists of:
  &tty->termios_rwsem --> console_lock --> &buf->lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&buf->lock);
                               lock(console_lock);
                               lock(&buf->lock);
  rlock(&tty->termios_rwsem);

 *** DEADLOCK ***

4 locks held by kworker/u33:3/62:
 #0: ffff88801bce4140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x12b1/0x1940 kernel/workqueue.c:3297
 #1: ffffc900009efd08 ((work_completion)(&buf->work)){+.+.}-{0:0}, at: process_one_work+0x988/0x1940 kernel/workqueue.c:3298
 #2: ffff88801404a8b8 (&buf->lock){+.+.}-{4:4}, at: flush_to_ldisc+0x34/0x730 drivers/tty/tty_buffer.c:474
 #3: ffff88804b3fe0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref+0x21/0x90 drivers/tty/tty_ldisc.c:263

stack backtrace:
CPU: 0 UID: 0 PID: 62 Comm: kworker/u33:3 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: events_unbound flush_to_ldisc
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_circular_bug.cold+0x178/0x1c7 kernel/locking/lockdep.c:2043
 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2175
 check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237
 lock_acquire kernel/locking/lockdep.c:5868 [inline]
 lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
 down_read+0x99/0x4c0 kernel/locking/rwsem.c:1574
 class_rwsem_read_constructor include/linux/rwsem.h:259 [inline]
 n_tty_receive_buf_common+0x85/0x1930 drivers/tty/n_tty.c:1678
 tty_ldisc_receive_buf+0xaa/0x1a0 drivers/tty/tty_buffer.c:394
 tty_port_default_receive_buf+0x70/0xb0 drivers/tty/tty_port.c:37
 receive_buf drivers/tty/tty_buffer.c:452 [inline]
 flush_to_ldisc+0x26b/0x730 drivers/tty/tty_buffer.c:502
 process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
 process_scheduled_works kernel/workqueue.c:3405 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Strategy: To trigger the `console_lock` -> `&buf->lock` dependency without relying on `/proc/sysrq-trigger` (which might be disabled or restricted), we can use the VT keyboard driver. 

The function `vc_SAK` takes `console_lock` and then calls `__do_SAK`, which takes `&buf->lock`. `vc_SAK` is scheduled by `fn_SAK`, which is triggered when the keyboard driver receives a key mapped to the `K_SAK` keysym. 

We can dynamically map a normal key (e.g., `KEY_A`) to `K_SAK` using the `KDSKBENT` ioctl on a VT device (like `/dev/tty0`). Then, we can inject a `KEY_A` keypress using a virtual input device via `/dev/uinput`. This will simulate the SAK key combination and execute `vc_SAK`, recording the required lock dependency.

### Minimal C Reproducer

```c
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <stdlib.h>
#include <linux/kd.h>
#include <linux/uinput.h>
#include <string.h>
#include <stdio.h>

int main(void) {
    // 1. Trigger: &tty->termios_rwsem -> &port->mutex
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial >= 0) {
        struct termios term;
        if (ioctl(fd_serial, TCGETS, &term) == 0) {
            ioctl(fd_serial, TCSETS, &term);
        }
        close(fd_serial);
    }

    // 2. Trigger: console_lock -> &buf->lock
    // Map KEY_A (keycode 30) to K_SAK (0x020F)
    int fd_tty = open("/dev/tty0", O_RDWR);
    if (fd_tty < 0) fd_tty = open("/dev/tty1", O_RDWR);
    if (fd_tty < 0) fd_tty = open("/dev/console", O_RDWR);
    
    if (fd_tty >= 0) {
        struct kbentry ke;
        ke.kb_table = 0;
        ke.kb_index = 30; // KEY_A
        ke.kb_value = 0x020F; // K_SAK
        ioctl(fd_tty, KDSKBENT, &ke);
        close(fd_tty);
    }

    // Inject KEY_A via uinput to trigger fn_SAK -> vc_SAK
    int ufd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
    if (ufd >= 0) {
        ioctl(ufd, UI_SET_EVBIT, EV_KEY);
        ioctl(ufd, UI_SET_KEYBIT, KEY_A);

        struct uinput_setup usetup;
        memset(&usetup, 0, sizeof(usetup));
        usetup.id.bustype = BUS_USB;
        usetup.id.vendor = 0x1234;
        usetup.id.product = 0x5678;
        strcpy(usetup.name, "Virtual Keyboard");
        ioctl(ufd, UI_DEV_SETUP, &usetup);
        ioctl(ufd, UI_DEV_CREATE);

        usleep(100000); // wait for input device to be registered

        struct input_event ie;
        
        // Press KEY_A
        memset(&ie, 0, sizeof(ie));
        ie.type = EV_KEY;
        ie.code = KEY_A;
        ie.value = 1;
        write(ufd, &ie, sizeof(ie));

        memset(&ie, 0, sizeof(ie));
        ie.type = EV_SYN;
        ie.code = SYN_REPORT;
        ie.value = 0;
        write(ufd, &ie, sizeof(ie));

        // Release KEY_A
        memset(&ie, 0, sizeof(ie));
        ie.type = EV_KEY;
        ie.code = KEY_A;
        ie.value = 0;
        write(ufd, &ie, sizeof(ie));

        memset(&ie, 0, sizeof(ie));
        ie.type = EV_SYN;
        ie.code = SYN_REPORT;
        ie.value = 0;
        write(ufd, &ie, sizeof(ie));

        usleep(100000); // wait for vc_SAK workqueue to execute
        ioctl(ufd, UI_DEV_DESTROY);
        close(ufd);
    }

    // 3. Trigger: &buf->lock -> &tty->termios_rwsem
    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx >= 0) {
        grantpt(ptmx);
        unlockpt(ptmx);
        char *pts_name = ptsname(ptmx);
        if (pts_name) {
            int pts = open(pts_name, O_RDWR | O_NOCTTY);
            if (pts >= 0) {
                // Writing to the slave PTY triggers flush_to_ldisc on the master PTY
                write(pts, "a", 1);
                // Wait a bit for the flush_to_ldisc workqueue to execute
                usleep(100000);
                close(pts);
            }
        }
        close(ptmx);
    }

    return 0;
}
```


Previous Reproducer Attempt:
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>

int main(void) {
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) {
        printf("[-] Failed to open /dev/ttyS0: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/ttyS0.\n");
    close(fd_serial);

    int fd_sysrq = open("/proc/sysrq-trigger", O_WRONLY);
    if (fd_sysrq < 0) {
        printf("[-] Failed to open /proc/sysrq-trigger: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /proc/sysrq-trigger.\n");
    close(fd_sysrq);

    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx < 0) {
        printf("[-] Failed to open /dev/ptmx: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/ptmx.\n");
    close(ptmx);

    printf("[+] All probes successful.\n");
    return 0;
}




Execution Results & Debugging Feedback:
The probe successfully opened `/dev/ttyS0`, but failed to open `/proc/sysrq-trigger` (No such file or directory). This indicates that sysrq is either disabled in the kernel config or restricted by the sandbox. You will need to find an alternative way to trigger the console lock or whatever you intended to do with sysrq (e.g., writing to `/dev/kmsg`, using `ioctl(TIOCLINUX)`, or other console-related operations). Please adjust your reproducer strategy accordingly.

gemini-3.1-pro-preview

							input: 8480
							output: 528
							thoughts: 1113
						

**My Thought Process for Constructing the Bug Verification Probe**

My primary objective here is to devise a minimal C program that can effectively verify a suspected bugfix. The bug itself is a rather insidious potential circular locking dependency within `n_tty_receive_buf_common`. I've traced the problematic dependency chain: it flows from `&tty->termios_rwsem`, then to `console_lock`, and finally to `&buf->lock`.

My initial approach involved attempting to use `/proc/sysrq-trigger`. However, this avenue proved fruitless as the target either didn't exist or was inaccessible in my environment. This necessitated a pivot.

Fortunately, the user has provided a promising alternative strategy. This strategy hinges on leveraging specific device nodes: `/dev/uinput` for injecting keypresses and `/dev/tty0` (or its siblings like `/dev/tty1` or `/dev/console`) to map a particular key to the `K_SAK` (Secure Attention Key) event.

Before diving headfirst into implementing the full exploit, it's prudent to ensure the fundamental prerequisites are met. Therefore, my immediate next step is to construct a "probe" program. This probe will systematically check for the accessibility of the crucial device nodes identified in the user's strategy: `/dev/uinput`, `/dev/tty0` (falling back to `/dev/tty1` or `/dev/console` if `/dev/tty0` isn't available), and `/dev/ptmx`.

Upon reviewing the user's explicit strategy code snippet, I can see the exact sequence of operations they intend:

1.  Triggering `&tty->termios_rwsem` -> `&port->mutex` via opening `/dev/ttyS0`.
2.  Triggering `console_lock` -> `&buf->lock` by mapping `KEY_A` to `K_SAK` and injecting it via `/dev/uinput`, which in turn is facilitated by opening `/dev/tty0`.
3.  Triggering `&buf->lock` -> `&tty->termios_rwsem` by opening `/dev/ptmx`.

This confirms the necessity of my probe targeting these specific devices. My probe program will be designed to open each of these devices. For `/dev/tty0`, I'll implement a fallback mechanism, trying `/dev/tty1` and then `/dev/console` if the first attempt fails. If any of these essential devices cannot be opened, the probe will report the failure and exit, indicating that the environment isn't set up for the intended bug verification. If all devices are successfully opened and closed, the probe will signify a positive outcome, confirming that the necessary building blocks are in place.

Reflecting on my previous probe, I recall that `/dev/ttyS0` was indeed accessible, which is a good sign. The prior attempt's failure was with `/proc/sysrq-trigger`, not `/dev/ttyS0`. So, I will proceed with constructing this refined probe program to check `/dev/ttyS0`, `/dev/tty0` (with fallbacks), `/dev/uinput`, and `/dev/ptmx`, ensuring a robust environment for the subsequent bug verification.

map[IsProbe:true RawCandidateReproC:#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>

int main(void) {
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) {
        printf("[-] Failed to open /dev/ttyS0: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/ttyS0.\n");
    close(fd_serial);

    int fd_tty = open("/dev/tty0", O_RDWR);
    if (fd_tty < 0) fd_tty = open("/dev/tty1", O_RDWR);
    if (fd_tty < 0) fd_tty = open("/dev/console", O_RDWR);
    if (fd_tty < 0) {
        printf("[-] Failed to open /dev/tty0, /dev/tty1, and /dev/console: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened a tty/console.\n");
    close(fd_tty);

    int ufd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
    if (ufd < 0) {
        printf("[-] Failed to open /dev/uinput: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/uinput.\n");
    close(ufd);

    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx < 0) {
        printf("[-] Failed to open /dev/ptmx: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/ptmx.\n");
    close(ptmx);

    printf("[+] All probes successful.\n");
    return 0;
}]

map[IsProbe:true RawCandidateReproC:#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>

int main(void) {
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) {
        printf("[-] Failed to open /dev/ttyS0: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/ttyS0.\n");
    close(fd_serial);

    int fd_tty = open("/dev/tty0", O_RDWR);
    if (fd_tty < 0) fd_tty = open("/dev/tty1", O_RDWR);
    if (fd_tty < 0) fd_tty = open("/dev/console", O_RDWR);
    if (fd_tty < 0) {
        printf("[-] Failed to open /dev/tty0, /dev/tty1, and /dev/console: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened a tty/console.\n");
    close(fd_tty);

    int ufd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
    if (ufd < 0) {
        printf("[-] Failed to open /dev/uinput: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/uinput.\n");
    close(ufd);

    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx < 0) {
        printf("[-] Failed to open /dev/ptmx: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/ptmx.\n");
    close(ptmx);

    printf("[+] All probes successful.\n");
    return 0;
}]

map[CurrentCandidateReproC:#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>

int main(void) {
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) {
        printf("[-] Failed to open /dev/ttyS0: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/ttyS0.\n");
    close(fd_serial);

    int fd_tty = open("/dev/tty0", O_RDWR);
    if (fd_tty < 0) fd_tty = open("/dev/tty1", O_RDWR);
    if (fd_tty < 0) fd_tty = open("/dev/console", O_RDWR);
    if (fd_tty < 0) {
        printf("[-] Failed to open /dev/tty0, /dev/tty1, and /dev/console: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened a tty/console.\n");
    close(fd_tty);

    int ufd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
    if (ufd < 0) {
        printf("[-] Failed to open /dev/uinput: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/uinput.\n");
    close(ufd);

    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx < 0) {
        printf("[-] Failed to open /dev/ptmx: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/ptmx.\n");
    close(ptmx);

    printf("[+] All probes successful.\n");
    return 0;
}]

map[CompilerError: FormattedReproC:#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>

int main(void) {
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) {
        printf("[-] Failed to open /dev/ttyS0: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/ttyS0.\n");
    close(fd_serial);

    int fd_tty = open("/dev/tty0", O_RDWR);
    if (fd_tty < 0) fd_tty = open("/dev/tty1", O_RDWR);
    if (fd_tty < 0) fd_tty = open("/dev/console", O_RDWR);
    if (fd_tty < 0) {
        printf("[-] Failed to open /dev/tty0, /dev/tty1, and /dev/console: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened a tty/console.\n");
    close(fd_tty);

    int ufd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
    if (ufd < 0) {
        printf("[-] Failed to open /dev/uinput: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/uinput.\n");
    close(ufd);

    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx < 0) {
        printf("[-] Failed to open /dev/ptmx: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/ptmx.\n");
    close(ptmx);

    printf("[+] All probes successful.\n");
    return 0;
}]

map[CompilerError:]

map[CandidateBugTitle: CandidateCrashReport: CandidateReproduced:false ConsoleOutput:[  107.267152][   T33] kauditd_printk_skb: 10 callbacks suppressed
[  107.267167][   T33] audit: type=1400 audit(1786492303.242:201): avc:  denied  { transition } for  pid=5830 comm="sshd-session" path="/bin/sh" dev="sda1" ino=90 scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[  107.285349][   T33] audit: type=1400 audit(1786492303.242:202): avc:  denied  { noatsecure } for  pid=5830 comm="sshd-session" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[  107.297547][   T33] audit: type=1400 audit(1786492303.242:203): avc:  denied  { rlimitinh } for  pid=5830 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[  107.308536][   T33] audit: type=1400 audit(1786492303.242:204): avc:  denied  { siginh } for  pid=5830 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[  109.345138][   T33] audit: type=1400 audit(1786492305.322:205): avc:  denied  { write } for  pid=5834 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  109.415982][   T33] audit: type=1400 audit(1786492305.392:206): avc:  denied  { write } for  pid=5837 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  109.945615][   T33] audit: type=1400 audit(1786492305.922:207): avc:  denied  { write } for  pid=5840 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  110.030366][   T33] audit: type=1400 audit(1786492306.002:208): avc:  denied  { write } for  pid=5843 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  110.388516][   T33] audit: type=1400 audit(1786492306.362:209): avc:  denied  { write } for  pid=5846 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  110.503245][   T33] audit: type=1400 audit(1786492306.472:210): avc:  denied  { write } for  pid=5849 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  112.922114][   T33] kauditd_printk_skb: 6 callbacks suppressed
[  112.922128][   T33] audit: type=1400 audit(1786492308.902:217): avc:  denied  { write } for  pid=5875 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  113.029010][   T33] audit: type=1400 audit(1786492309.002:218): avc:  denied  { write } for  pid=5878 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  113.223169][   T33] audit: type=1400 audit(1786492309.182:219): avc:  denied  { write } for  pid=5881 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  113.291973][   T33] audit: type=1400 audit(1786492309.262:220): avc:  denied  { write } for  pid=5884 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
Warning: Permanently added '[localhost]:13890' (ED25519) to the list of known hosts.
[  114.670233][   T33] audit: type=1400 audit(1786492310.642:221): avc:  denied  { write } for  pid=5894 comm="syz-executor217" name="uinput" dev="devtmpfs" ino=924 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:event_device_t tclass=chr_file permissive=1
[+] Successfully opened /dev/ttyS0.
[+] Successfully opened a tty/console.
[+] Successfully opened /dev/uinput.
[+] Successfully opened /dev/ptmx.
[+] All probes successful.
[  114.688846][   T33] audit: type=1400 audit(1786492310.642:222): avc:  denied  { open } for  pid=5894 comm="syz-executor217" path="/dev/uinput" dev="devtmpfs" ino=924 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:event_device_t tclass=chr_file permissive=1
 OtherCrashReports:<nil> StraceOutput:/strace -e \!wait4,clock_nanosleep,nanosleep -s 100 -x -f /syz-executor1539453638

<...>
[  107.592284][   T33] kauditd_printk_skb: 10 callbacks suppressed
[  107.592297][   T33] audit: type=1400 audit(1786492438.237:201): avc:  denied  { transition } for  pid=5833 comm="sshd-session" path="/bin/sh" dev="sda1" ino=90 scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[  107.606974][   T33] audit: type=1400 audit(1786492438.237:202): avc:  denied  { noatsecure } for  pid=5833 comm="sshd-session" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[  107.617693][   T33] audit: type=1400 audit(1786492438.237:203): avc:  denied  { rlimitinh } for  pid=5833 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[  107.626803][   T33] audit: type=1400 audit(1786492438.237:204): avc:  denied  { siginh } for  pid=5833 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[  111.162078][   T33] audit: type=1400 audit(1786492441.807:205): avc:  denied  { write } for  pid=5842 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  111.242533][   T33] audit: type=1400 audit(1786492441.887:206): avc:  denied  { write } for  pid=5845 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  111.393861][   T33] audit: type=1400 audit(1786492442.037:207): avc:  denied  { write } for  pid=5848 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  111.468843][   T33] audit: type=1400 audit(1786492442.117:208): avc:  denied  { write } for  pid=5851 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  111.617541][   T33] audit: type=1400 audit(1786492442.267:209): avc:  denied  { write } for  pid=5854 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  111.689693][   T33] audit: type=1400 audit(1786492442.337:210): avc:  denied  { write } for  pid=5857 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  112.684141][   T33] kauditd_printk_skb: 4 callbacks suppressed
[  112.684157][   T33] audit: type=1400 audit(1786492443.327:215): avc:  denied  { write } for  pid=5872 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  112.761854][   T33] audit: type=1400 audit(1786492443.407:216): avc:  denied  { write } for  pid=5875 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  113.079916][   T33] audit: type=1400 audit(1786492443.727:217): avc:  denied  { write } for  pid=5879 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  113.208292][   T33] audit: type=1400 audit(1786492443.857:218): avc:  denied  { write } for  pid=5882 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  113.829999][   T33] audit: type=1400 audit(1786492444.477:219): avc:  denied  { write } for  pid=5889 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  113.923426][   T33] audit: type=1400 audit(1786492444.567:220): avc:  denied  { write } for  pid=5892 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
Warning: Permanently added '[localhost]:27831' (ED25519) to the list of known hosts.
execve("/syz-executor1539453638", ["/syz-executor1539453638"], 0x7ffd4f4d3c80 /* 11 vars */) = 0
brk(NULL)                               = 0x55555eb9e000
brk(0x55555eb9ed80)                     = 0x55555eb9ed80
arch_prctl(ARCH_SET_FS, 0x55555eb9e400) = 0
set_tid_address(0x55555eb9e6d0)         = 5907
set_robust_list(0x55555eb9e6e0, 24)     = 0
rseq({cpu_id_start=0, cpu_id=RSEQ_CPU_ID_UNINITIALIZED, rseq_cs=NULL, flags=0, node_id=0, mm_cid=0, slice_ctrl={request=0, granted=0, __reserved=0}, __reserved=0}, 33, 0, 0x53053053) = 0
prlimit64(0, RLIMIT_STACK, NULL, {rlim_cur=8192*1024, rlim_max=RLIM64_INFINITY}) = 0
readlinkat(AT_FDCWD, "/proc/self/exe", "/syz-executor1539453638", 4096) = 23
getrandom("\xf7\x3d\x22\x5c\x96\xa9\x08\x45", 8, GRND_NONBLOCK) = 8
brk(NULL)                               = 0x55555eb9ed80
brk(0x55555ebbfd80)                     = 0x55555ebbfd80
brk(0x55555ebc0000)                     = 0x55555ebc0000
mprotect(0x7fbe9e0f4000, 20480, PROT_READ) = 0
openat(AT_FDCWD, "/dev/ttyS0", O_RDWR|O_NOCTTY) = 3
fstat(1, {st_mode=S_IFIFO|0600, st_size=0, ...}) = 0
close(3)                                = 0
openat(AT_FDCWD, "/dev/tty0", O_RDWR)   = 3
close(3)                                = 0
[  117.709781][   T33] audit: type=1400 audit(1786492448.357:221): avc:  denied  { write } for  pid=5907 comm="syz-executor153" name="uinput" dev="devtmpfs" ino=924 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:event_device_t tclass=chr_file permissive=1
[  117.728286][   T33] audit: type=1400 audit(1786492448.357:222): avc:  denied  { open } for  pid=5907 comm="syz-executor153" path="/dev/uinput" dev="devtmpfs" ino=924 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:event_device_t tclass=chr_file permissive=1
openat(AT_FDCWD, "/dev/uinput", O_WRONLY|O_NONBLOCK) = 3
close(3)                                = 0
openat(AT_FDCWD, "/dev/ptmx", O_RDWR|O_NOCTTY) = 3
close(3)                                = 0
write(1, "[+] Successfully opened /dev/ttyS0.\n[+] Successfully opened a tty/console.\n[+] Successfully opened /"..., 174) = 174
exit_group(0)                           = ?
[+] Successfully opened /dev/ttyS0.
[+] Successfully opened a tty/console.
[+] Successfully opened /dev/uinput.
[+] Successfully opened /dev/ptmx.
[+] All probes successful.
+++ exited with 0 +++
 TestError:]

map[TruncatedConsoleOutput:[  107.267152][   T33] kauditd_printk_skb: 10 callbacks suppressed
[  107.267167][   T33] audit: type=1400 audit(1786492303.242:201): avc:  denied  { transition } for  pid=5830 comm="sshd-session" path="/bin/sh" dev="sda1" ino=90 scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[  107.285349][   T33] audit: type=1400 audit(1786492303.242:202): avc:  denied  { noatsecure } for  pid=5830 comm="sshd-session" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[  107.297547][   T33] audit: type=1400 audit(1786492303.242:203): avc:  denied  { rlimitinh } for  pid=5830 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[  107.308536][   T33] audit: type=1400 audit(1786492303.242:204): avc:  denied  { siginh } for  pid=5830 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[  109.345138][   T33] audit: type=1400 audit(1786492305.322:205): avc:  denied  { write } for  pid=5834 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  109.415982][   T33] audit: type=1400 audit(1786492305.392:206): avc:  denied  { write } for  pid=5837 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  109.945615][   T33] audit: type=1400 audit(1786492305.922:207): avc:  denied  { write } for  pid=5840 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  110.030366][   T33] audit: type=1400 audit(1786492306.002:208): avc:  denied  { write } for  pid=5843 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  110.388516][   T33] audit: type=1400 audit(1786492306.362:209): avc:  denied  { write } for  pid=5846 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  110.503245][   T33] audit: type=1400 audit(1786492306.472:210): avc:  denied  { write } for  pid=5849 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  112.922114][   T33] kauditd_printk_skb: 6 callbacks suppressed
[  112.922128][   T33] audit: type=1400 audit(1786492308.902:217): avc:  denied  { write } for  pid=5875 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  113.029010][   T33] audit: type=1400 audit(1786492309.002:218): avc:  denied  { write } for  pid=5878 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  113.223169][   T33] audit: type=1400 audit(1786492309.182:219): avc:  denied  { write } for  pid=5881 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  113.291973][   T33] audit: type=1400 audit(1786492309.262:220): avc:  denied  { write } for  pid=5884 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
Warning: Permanently added '[localhost]:13890' (ED25519) to the list of known hosts.
[  114.670233][   T33] audit: type=1400 audit(1786492310.642:221): avc:  denied  { write } for  pid=5894 comm="syz-executor217" name="uinput" dev="devtmpfs" ino=924 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:event_device_t tclass=chr_file permissive=1
[+] Successfully opened /dev/ttyS0.
[+] Successfully opened a tty/console.
[+] Successfully opened /dev/uinput.
[+] Successfully opened /dev/ptmx.
[+] All probes successful.
[  114.688846][   T33] audit: type=1400 audit(1786492310.642:222): avc:  denied  { open } for  pid=5894 comm="syz-executor217" path="/dev/uinput" dev="devtmpfs" ino=924 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:event_device_t tclass=chr_file permissive=1
 TruncatedCrashReport: TruncatedStraceOutput:/strace -e \!wait4,clock_nanosleep,nanosleep -s 100 -x -f /syz-executor1539453638

<...>
[  107.592284][   T33] kauditd_printk_skb: 10 callbacks suppressed
[  107.592297][   T33] audit: type=1400 audit(1786492438.237:201): avc:  denied  { transition } for  pid=5833 comm="sshd-session" path="/bin/sh" dev="sda1" ino=90 scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[  107.606974][   T33] audit: type=1400 audit(1786492438.237:202): avc:  denied  { noatsecure } for  pid=5833 comm="sshd-session" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[  107.617693][   T33] audit: type=1400 audit(1786492438.237:203): avc:  denied  { rlimitinh } for  pid=5833 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[  107.626803][   T33] audit: type=1400 audit(1786492438.237:204): avc:  denied  { siginh } for  pid=5833 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[  111.162078][   T33] audit: type=1400 audit(1786492441.807:205): avc:  denied  { write } for  pid=5842 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  111.242533][   T33] audit: type=1400 audit(1786492441.887:206): avc:  denied  { write } for  pid=5845 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  111.393861][   T33] audit: type=1400 audit(1786492442.037:207): avc:  denied  { write } for  pid=5848 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  111.468843][   T33] audit: type=1400 audit(1786492442.117:208): avc:  denied  { write } for  pid=5851 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  111.617541][   T33] audit: type=1400 audit(1786492442.267:209): avc:  denied  { write } for  pid=5854 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  111.689693][   T33] audit: type=1400 audit(1786492442.337:210): avc:  denied  { write } for  pid=5857 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  112.684141][   T33] kauditd_printk_skb: 4 callbacks suppressed
[  112.684157][   T33] audit: type=1400 audit(1786492443.327:215): avc:  denied  { write } for  pid=5872 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  112.761854][   T33] audit: type=1400 audit(1786492443.407:216): avc:  denied  { write } for  pid=5875 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  113.079916][   T33] audit: type=1400 audit(1786492443.727:217): avc:  denied  { write } for  pid=5879 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  113.208292][   T33] audit: type=1400 audit(1786492443.857:218): avc:  denied  { write } for  pid=5882 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  113.829999][   T33] audit: type=1400 audit(1786492444.477:219): avc:  denied  { write } for  pid=5889 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  113.923426][   T33] audit: type=1400 audit(1786492444.567:220): avc:  denied  { write } for  pid=5892 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
Warning: Permanently added '[localhost]:27831' (ED25519) to the list of known hosts.
execve("/syz-executor1539453638", ["/syz-executor1539453638"], 0x7ffd4f4d3c80 /* 11 vars */) = 0
brk(NULL)                               = 0x55555eb9e000
brk(0x55555eb9ed80)                     = 0x55555eb9ed80
arch_prctl(ARCH_SET_FS, 0x55555eb9e400) = 0
set_tid_address(0x55555eb9e6d0)         = 5907
set_robust_list(0x55555eb9e6e0, 24)     = 0
rseq({cpu_id_start=0, cpu_id=RSEQ_CPU_ID_UNINITIALIZED, rseq_cs=NULL, flags=0, node_id=0, mm_cid=0, slice_ctrl={request=0, granted=0, __reserved=0}, __reserved=0}, 33, 0, 0x53053053) = 0
prlimit64(0, RLIMIT_STACK, NULL, {rlim_cur=8192*1024, rlim_max=RLIM64_INFINITY}) = 0
readlinkat(AT_FDCWD, "/proc/self/exe", "/syz-executor1539453638", 4096) = 23
getrandom("\xf7\x3d\x22\x5c\x96\xa9\x08\x45", 8, GRND_NONBLOCK) = 8
brk(NULL)                               = 0x55555eb9ed80
brk(0x55555ebbfd80)                     = 0x55555ebbfd80
brk(0x55555ebc0000)                     = 0x55555ebc0000
mprotect(0x7fbe9e0f4000, 20480, PROT_READ) = 0
openat(AT_FDCWD, "/dev/ttyS0", O_RDWR|O_NOCTTY) = 3
fstat(1, {st_mode=S_IFIFO|0600, st_size=0, ...}) = 0
close(3)                                = 0
openat(AT_FDCWD, "/dev/tty0", O_RDWR)   = 3
close(3)                                = 0
[  117.709781][   T33] audit: type=1400 audit(1786492448.357:221): avc:  denied  { write } for  pid=5907 comm="syz-executor153" name="uinput" dev="devtmpfs" ino=924 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:event_device_t tclass=chr_file permissive=1
[  117.728286][   T33] audit: type=1400 audit(1786492448.357:222): avc:  denied  { open } for  pid=5907 comm="syz-executor153" path="/dev/uinput" dev="devtmpfs" ino=924 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:event_device_t tclass=chr_file permissive=1
openat(AT_FDCWD, "/dev/uinput", O_WRONLY|O_NONBLOCK) = 3
close(3)                                = 0
openat(AT_FDCWD, "/dev/ptmx", O_RDWR|O_NOCTTY) = 3
close(3)                                = 0
write(1, "[+] Successfully opened /dev/ttyS0.\n[+] Successfully opened a tty/console.\n[+] Successfully opened /"..., 174) = 174
exit_group(0)                           = ?
[+] Successfully opened /dev/ttyS0.
[+] Successfully opened a tty/console.
[+] Successfully opened /dev/uinput.
[+] Successfully opened /dev/ptmx.
[+] All probes successful.
+++ exited with 0 +++
]

best-expensive

map[Feedback:The environment probe was successful. All required devices (/dev/ttyS0, /dev/tty0, /dev/uinput, /dev/ptmx) were opened successfully. The environment is ready. Please proceed to generate the full reproducer in the next iteration. ProbePassed:true TerminalError: TitleMatches:false]

You are a security researcher with deep Linux kernel background.
Analyze the results of running the generated program.

=== CRITICAL ENVIRONMENT & TARGET CLASSIFICATION ===
Set 'TerminalError' to a descriptive error message ONLY if:
1. The execution failed due to missing hardware device nodes, subsystems, kernel modules, or privilege limits
   that cannot be loaded, created, or bypassed by user-space C code edits in the VM guest.
2. The target source files or functions described in the bug description do not exist in the checked-out codebase,
   meaning the codebase version is mismatched and the target code is absent.

=== CRITICAL PROHIBITIONS ===
- Do NOT classify a run as a terminal failure or assume a bug is fixed based on git log entries, commit titles,
  or commit messages. Reproducibility can ONLY be determined by executing reproducer candidates in the VM.
- Do NOT suggest C code strategies, repairs, or namespace bypasses when setting 'TerminalError'.


=== PHASE 1: CAPABILITY PROBING (EVALUATION) ===
The executed program was a simple environment probe.
Use this to guide your classification and feedback:
1. If the execution was successful (all environment/subsystem probes passed and program exited with 0),
   set the field 'ProbePassed' to true and provide feedback explicitly indicating that the environment
   is ready and the agent should now proceed to generate the full reproducer in the next iteration.
2. If the probe failed (e.g., missing permissions, missing devices, or sandbox restrictions),
   set the field 'ProbePassed' to false, and explain what failed in the 'Feedback'
   field so the generator can adjust its setups.

Prefer calling several tools at the same time to save round-trips.


Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.

Bug Description: possible deadlock in n_tty_receive_buf_common

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
kworker/u33:3/62 is trying to acquire lock:
ffff88804b3fe2c8 (&tty->termios_rwsem){++++}-{4:4}, at: class_rwsem_read_constructor include/linux/rwsem.h:259 [inline]
ffff88804b3fe2c8 (&tty->termios_rwsem){++++}-{4:4}, at: n_tty_receive_buf_common+0x85/0x1930 drivers/tty/n_tty.c:1678

but task is already holding lock:
ffff88801404a8b8 (&buf->lock){+.+.}-{4:4}, at: flush_to_ldisc+0x34/0x730 drivers/tty/tty_buffer.c:474

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&buf->lock){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       tty_buffer_flush+0x72/0x310 drivers/tty/tty_buffer.c:236
       tty_ldisc_flush+0xd2/0xf0 drivers/tty/tty_ldisc.c:388
       __do_SAK+0x368/0x480 drivers/tty/tty_io.c:3025
       vc_SAK+0x7f/0x320 drivers/tty/vt/vt_ioctl.c:994
       process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
       process_scheduled_works kernel/workqueue.c:3405 [inline]
       worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
       kthread+0x370/0x450 kernel/kthread.c:436
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #2 (console_lock){+.+.}-{0:0}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       console_lock+0x7a/0xa0 kernel/printk/printk.c:2896
       uart_configure_port drivers/tty/serial/serial_core.c:2530 [inline]
       serial_core_add_one_port drivers/tty/serial/serial_core.c:3101 [inline]
       serial_core_register_port+0xe65/0x16f0 drivers/tty/serial/serial_core.c:3322
       serial8250_register_8250_port+0x15af/0x2330 drivers/tty/serial/8250/8250_core.c:828
       serial_pnp_probe+0x436/0x930 drivers/tty/serial/8250/8250_pnp.c:480
       pnp_device_probe+0x2b3/0x4a0 drivers/pnp/driver.c:111
       call_driver_probe drivers/base/dd.c:628 [inline]
       really_probe+0x241/0xa60 drivers/base/dd.c:706
       __driver_probe_device+0x20e/0x450 drivers/base/dd.c:868
       driver_probe_device+0x4a/0x140 drivers/base/dd.c:898
       __driver_attach+0x21f/0x5b0 drivers/base/dd.c:1292
       bus_for_each_dev+0x13e/0x1d0 drivers/base/bus.c:383
       bus_add_driver+0x305/0x5b0 drivers/base/bus.c:763
       driver_register+0x1e2/0x360 drivers/base/driver.c:174
       serial8250_init+0xcc/0x1c0 drivers/tty/serial/8250/8250_platform.c:317
       do_one_initcall+0x11d/0x700 init/main.c:1347
       do_initcall_level init/main.c:1409 [inline]
       do_initcalls init/main.c:1425 [inline]
       do_basic_setup init/main.c:1445 [inline]
       kernel_init_freeable+0x6ea/0x7b0 init/main.c:1658
       kernel_init+0x1f/0x1e0 init/main.c:1548
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #1 (&port->mutex){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       class_mutex_constructor include/linux/mutex.h:253 [inline]
       uart_set_termios+0x8e/0x690 drivers/tty/serial/serial_core.c:1645
       tty_set_termios+0x64d/0x980 drivers/tty/tty_ioctl.c:341
       set_termios+0x5c8/0x880 drivers/tty/tty_ioctl.c:516
       tty_mode_ioctl+0x17e/0xd40 drivers/tty/tty_ioctl.c:803
       n_tty_ioctl_helper+0x47/0x2b0 drivers/tty/tty_ioctl.c:982
       n_tty_ioctl+0x53/0x340 drivers/tty/n_tty.c:2496
       tty_ioctl+0x11b4/0x1640 drivers/tty/tty_io.c:2801
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl fs/ioctl.c:583 [inline]
       __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x115/0x840 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&tty->termios_rwsem){++++}-{4:4}:
       check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       down_read+0x99/0x4c0 kernel/locking/rwsem.c:1574
       class_rwsem_read_constructor include/linux/rwsem.h:259 [inline]
       n_tty_receive_buf_common+0x85/0x1930 drivers/tty/n_tty.c:1678
       tty_ldisc_receive_buf+0xaa/0x1a0 drivers/tty/tty_buffer.c:394
       tty_port_default_receive_buf+0x70/0xb0 drivers/tty/tty_port.c:37
       receive_buf drivers/tty/tty_buffer.c:452 [inline]
       flush_to_ldisc+0x26b/0x730 drivers/tty/tty_buffer.c:502
       process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
       process_scheduled_works kernel/workqueue.c:3405 [inline]
       worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
       kthread+0x370/0x450 kernel/kthread.c:436
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

other info that might help us debug this:

Chain exists of:
  &tty->termios_rwsem --> console_lock --> &buf->lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&buf->lock);
                               lock(console_lock);
                               lock(&buf->lock);
  rlock(&tty->termios_rwsem);

 *** DEADLOCK ***

4 locks held by kworker/u33:3/62:
 #0: ffff88801bce4140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x12b1/0x1940 kernel/workqueue.c:3297
 #1: ffffc900009efd08 ((work_completion)(&buf->work)){+.+.}-{0:0}, at: process_one_work+0x988/0x1940 kernel/workqueue.c:3298
 #2: ffff88801404a8b8 (&buf->lock){+.+.}-{4:4}, at: flush_to_ldisc+0x34/0x730 drivers/tty/tty_buffer.c:474
 #3: ffff88804b3fe0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref+0x21/0x90 drivers/tty/tty_ldisc.c:263

stack backtrace:
CPU: 0 UID: 0 PID: 62 Comm: kworker/u33:3 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: events_unbound flush_to_ldisc
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_circular_bug.cold+0x178/0x1c7 kernel/locking/lockdep.c:2043
 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2175
 check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237
 lock_acquire kernel/locking/lockdep.c:5868 [inline]
 lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
 down_read+0x99/0x4c0 kernel/locking/rwsem.c:1574
 class_rwsem_read_constructor include/linux/rwsem.h:259 [inline]
 n_tty_receive_buf_common+0x85/0x1930 drivers/tty/n_tty.c:1678
 tty_ldisc_receive_buf+0xaa/0x1a0 drivers/tty/tty_buffer.c:394
 tty_port_default_receive_buf+0x70/0xb0 drivers/tty/tty_port.c:37
 receive_buf drivers/tty/tty_buffer.c:452 [inline]
 flush_to_ldisc+0x26b/0x730 drivers/tty/tty_buffer.c:502
 process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
 process_scheduled_works kernel/workqueue.c:3405 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

IsProbe: true
Reproduced: false
Console Output: [  107.267152][   T33] kauditd_printk_skb: 10 callbacks suppressed
[  107.267167][   T33] audit: type=1400 audit(1786492303.242:201): avc:  denied  { transition } for  pid=5830 comm="sshd-session" path="/bin/sh" dev="sda1" ino=90 scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[  107.285349][   T33] audit: type=1400 audit(1786492303.242:202): avc:  denied  { noatsecure } for  pid=5830 comm="sshd-session" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[  107.297547][   T33] audit: type=1400 audit(1786492303.242:203): avc:  denied  { rlimitinh } for  pid=5830 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[  107.308536][   T33] audit: type=1400 audit(1786492303.242:204): avc:  denied  { siginh } for  pid=5830 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[  109.345138][   T33] audit: type=1400 audit(1786492305.322:205): avc:  denied  { write } for  pid=5834 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  109.415982][   T33] audit: type=1400 audit(1786492305.392:206): avc:  denied  { write } for  pid=5837 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  109.945615][   T33] audit: type=1400 audit(1786492305.922:207): avc:  denied  { write } for  pid=5840 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  110.030366][   T33] audit: type=1400 audit(1786492306.002:208): avc:  denied  { write } for  pid=5843 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  110.388516][   T33] audit: type=1400 audit(1786492306.362:209): avc:  denied  { write } for  pid=5846 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  110.503245][   T33] audit: type=1400 audit(1786492306.472:210): avc:  denied  { write } for  pid=5849 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  112.922114][   T33] kauditd_printk_skb: 6 callbacks suppressed
[  112.922128][   T33] audit: type=1400 audit(1786492308.902:217): avc:  denied  { write } for  pid=5875 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  113.029010][   T33] audit: type=1400 audit(1786492309.002:218): avc:  denied  { write } for  pid=5878 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  113.223169][   T33] audit: type=1400 audit(1786492309.182:219): avc:  denied  { write } for  pid=5881 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  113.291973][   T33] audit: type=1400 audit(1786492309.262:220): avc:  denied  { write } for  pid=5884 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
Warning: Permanently added '[localhost]:13890' (ED25519) to the list of known hosts.
[  114.670233][   T33] audit: type=1400 audit(1786492310.642:221): avc:  denied  { write } for  pid=5894 comm="syz-executor217" name="uinput" dev="devtmpfs" ino=924 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:event_device_t tclass=chr_file permissive=1
[+] Successfully opened /dev/ttyS0.
[+] Successfully opened a tty/console.
[+] Successfully opened /dev/uinput.
[+] Successfully opened /dev/ptmx.
[+] All probes successful.
[  114.688846][   T33] audit: type=1400 audit(1786492310.642:222): avc:  denied  { open } for  pid=5894 comm="syz-executor217" path="/dev/uinput" dev="devtmpfs" ino=924 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:event_device_t tclass=chr_file permissive=1

Strace Output: /strace -e \!wait4,clock_nanosleep,nanosleep -s 100 -x -f /syz-executor1539453638

<...>
[  107.592284][   T33] kauditd_printk_skb: 10 callbacks suppressed
[  107.592297][   T33] audit: type=1400 audit(1786492438.237:201): avc:  denied  { transition } for  pid=5833 comm="sshd-session" path="/bin/sh" dev="sda1" ino=90 scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[  107.606974][   T33] audit: type=1400 audit(1786492438.237:202): avc:  denied  { noatsecure } for  pid=5833 comm="sshd-session" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[  107.617693][   T33] audit: type=1400 audit(1786492438.237:203): avc:  denied  { rlimitinh } for  pid=5833 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[  107.626803][   T33] audit: type=1400 audit(1786492438.237:204): avc:  denied  { siginh } for  pid=5833 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[  111.162078][   T33] audit: type=1400 audit(1786492441.807:205): avc:  denied  { write } for  pid=5842 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  111.242533][   T33] audit: type=1400 audit(1786492441.887:206): avc:  denied  { write } for  pid=5845 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  111.393861][   T33] audit: type=1400 audit(1786492442.037:207): avc:  denied  { write } for  pid=5848 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  111.468843][   T33] audit: type=1400 audit(1786492442.117:208): avc:  denied  { write } for  pid=5851 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  111.617541][   T33] audit: type=1400 audit(1786492442.267:209): avc:  denied  { write } for  pid=5854 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  111.689693][   T33] audit: type=1400 audit(1786492442.337:210): avc:  denied  { write } for  pid=5857 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  112.684141][   T33] kauditd_printk_skb: 4 callbacks suppressed
[  112.684157][   T33] audit: type=1400 audit(1786492443.327:215): avc:  denied  { write } for  pid=5872 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  112.761854][   T33] audit: type=1400 audit(1786492443.407:216): avc:  denied  { write } for  pid=5875 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  113.079916][   T33] audit: type=1400 audit(1786492443.727:217): avc:  denied  { write } for  pid=5879 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  113.208292][   T33] audit: type=1400 audit(1786492443.857:218): avc:  denied  { write } for  pid=5882 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  113.829999][   T33] audit: type=1400 audit(1786492444.477:219): avc:  denied  { write } for  pid=5889 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[  113.923426][   T33] audit: type=1400 audit(1786492444.567:220): avc:  denied  { write } for  pid=5892 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
Warning: Permanently added '[localhost]:27831' (ED25519) to the list of known hosts.
execve("/syz-executor1539453638", ["/syz-executor1539453638"], 0x7ffd4f4d3c80 /* 11 vars */) = 0
brk(NULL)                               = 0x55555eb9e000
brk(0x55555eb9ed80)                     = 0x55555eb9ed80
arch_prctl(ARCH_SET_FS, 0x55555eb9e400) = 0
set_tid_address(0x55555eb9e6d0)         = 5907
set_robust_list(0x55555eb9e6e0, 24)     = 0
rseq({cpu_id_start=0, cpu_id=RSEQ_CPU_ID_UNINITIALIZED, rseq_cs=NULL, flags=0, node_id=0, mm_cid=0, slice_ctrl={request=0, granted=0, __reserved=0}, __reserved=0}, 33, 0, 0x53053053) = 0
prlimit64(0, RLIMIT_STACK, NULL, {rlim_cur=8192*1024, rlim_max=RLIM64_INFINITY}) = 0
readlinkat(AT_FDCWD, "/proc/self/exe", "/syz-executor1539453638", 4096) = 23
getrandom("\xf7\x3d\x22\x5c\x96\xa9\x08\x45", 8, GRND_NONBLOCK) = 8
brk(NULL)                               = 0x55555eb9ed80
brk(0x55555ebbfd80)                     = 0x55555ebbfd80
brk(0x55555ebc0000)                     = 0x55555ebc0000
mprotect(0x7fbe9e0f4000, 20480, PROT_READ) = 0
openat(AT_FDCWD, "/dev/ttyS0", O_RDWR|O_NOCTTY) = 3
fstat(1, {st_mode=S_IFIFO|0600, st_size=0, ...}) = 0
close(3)                                = 0
openat(AT_FDCWD, "/dev/tty0", O_RDWR)   = 3
close(3)                                = 0
[  117.709781][   T33] audit: type=1400 audit(1786492448.357:221): avc:  denied  { write } for  pid=5907 comm="syz-executor153" name="uinput" dev="devtmpfs" ino=924 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:event_device_t tclass=chr_file permissive=1
[  117.728286][   T33] audit: type=1400 audit(1786492448.357:222): avc:  denied  { open } for  pid=5907 comm="syz-executor153" path="/dev/uinput" dev="devtmpfs" ino=924 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:event_device_t tclass=chr_file permissive=1
openat(AT_FDCWD, "/dev/uinput", O_WRONLY|O_NONBLOCK) = 3
close(3)                                = 0
openat(AT_FDCWD, "/dev/ptmx", O_RDWR|O_NOCTTY) = 3
close(3)                                = 0
write(1, "[+] Successfully opened /dev/ttyS0.\n[+] Successfully opened a tty/console.\n[+] Successfully opened /"..., 174) = 174
exit_group(0)                           = ?
[+] Successfully opened /dev/ttyS0.
[+] Successfully opened a tty/console.
[+] Successfully opened /dev/uinput.
[+] Successfully opened /dev/ptmx.
[+] All probes successful.
+++ exited with 0 +++

Crash Report: 

gemini-3.1-pro-preview

							input: 11945
							output: 87
							thoughts: 169
						

**My Analysis of the Environment Probe Results**

Alright, let's break down what just happened with that initial environment probe. My primary task here is to rigorously analyze the output from the program I just ran. This wasn't some complex operation; it was a straightforward probe designed to check if the essential environmental components are accessible and functional.

Looking at the output:

```
[+] Successfully opened /dev/ttyS0.
[+] Successfully opened a tty/console.
[+] Successfully opened /dev/uinput.
[+] Successfully opened /dev/ptmx.
[+] All probes successful.
```

This is exactly what I was hoping to see. Each of these system devices – `/dev/ttyS0`, a general tty/console, `/dev/uinput` for input emulation, and `/dev/ptmx` for pseudo-terminals – was successfully opened. The clear message, "[+] All probes successful," confirms this.

Furthermore, the fact that the program exited with a code of `0` is a strong indicator of a clean execution. This aligns perfectly with the successful opening of all probes.

From a programmatic perspective, I'm expecting certain conditions to be met:

*   The `ProbePassed` flag *must* be `true`. Given the output, this is unequivocally the case.
*   The `TerminalError` field should be empty. There were no reported errors related to terminal access, so this condition is also satisfied.
*   The `TitleMatches` field *should* be `false`. This probe is purely diagnostic; it's not designed to trigger a specific error condition that would result in a title match. The absence of any crash or anomaly confirms this.
*   The `Feedback` should clearly convey that the environment is properly configured and ready for the next stage. Specifically, it needs to indicate that the agent should now proceed with generating the full reproducer.

Based on this analysis, my next logical step is to invoke the `set-results` tool. This tool will capture these findings and signal to the system that the environment is validated and ready for the subsequent, more complex task of generating the actual program reproducer.

map[Feedback:The environment probe was successful. All required devices (/dev/ttyS0, /dev/tty0, /dev/uinput, /dev/ptmx) were opened successfully. The environment is ready. Please proceed to generate the full reproducer in the next iteration. ProbePassed:true TerminalError: TitleMatches:false]

map[Feedback:The environment probe was successful. All required devices (/dev/ttyS0, /dev/tty0, /dev/uinput, /dev/ptmx) were opened successfully. The environment is ready. Please proceed to generate the full reproducer in the next iteration. ProbePassed:true TerminalError: TitleMatches:false]

map[CapabilitiesVerified:true ContinueSignal:continue EquivalenceAnalysis: OracleFeedback:The environment probe was successful. All required devices (/dev/ttyS0, /dev/tty0, /dev/uinput, /dev/ptmx) were opened successfully. The environment is ready. Please proceed to generate the full reproducer in the next iteration. ReproC: Reproduced:false ReproducedBugTitle: ReproducedCrashReport:]

map[OracleFeedback:The environment probe was successful. All required devices (/dev/ttyS0, /dev/tty0, /dev/uinput, /dev/ptmx) were opened successfully. The environment is ready. Please proceed to generate the full reproducer in the next iteration.]

best-expensive

You are an expert in Linux kernel debugging.
Refine the reproduction strategy based on feedback from previous attempts.
Analyze the technical diagnosis provided in the oracle feedback and translate it into concrete,
step-by-step instructions for the repro-generator on how to modify the code structure, alignments,
offsets, or parameters of the candidate program.

=== TOOL SELECTION GUIDELINES ===
- Prefer codesearch-definition-source and codesearch-struct-layout first for symbol lookups.
- Fall back to read-file or grepper for macros, headers, or if symbol lookup fails.

=== CRITICAL PROHIBITIONS ===
- Do NOT repeat searches for the same symbols or files. Use information you have already gathered.
- Do NOT write long explanations. Keep your reasoning short and focused on actionable changes.
- Do NOT assume a bug is fixed based on git commit history.
- If you are stuck, try a different approach or proceed to generate a candidate reproducer.
Prefer calling several tools at the same time to save round-trips.

Bug Description: possible deadlock in n_tty_receive_buf_common

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
kworker/u33:3/62 is trying to acquire lock:
ffff88804b3fe2c8 (&tty->termios_rwsem){++++}-{4:4}, at: class_rwsem_read_constructor include/linux/rwsem.h:259 [inline]
ffff88804b3fe2c8 (&tty->termios_rwsem){++++}-{4:4}, at: n_tty_receive_buf_common+0x85/0x1930 drivers/tty/n_tty.c:1678

but task is already holding lock:
ffff88801404a8b8 (&buf->lock){+.+.}-{4:4}, at: flush_to_ldisc+0x34/0x730 drivers/tty/tty_buffer.c:474

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&buf->lock){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       tty_buffer_flush+0x72/0x310 drivers/tty/tty_buffer.c:236
       tty_ldisc_flush+0xd2/0xf0 drivers/tty/tty_ldisc.c:388
       __do_SAK+0x368/0x480 drivers/tty/tty_io.c:3025
       vc_SAK+0x7f/0x320 drivers/tty/vt/vt_ioctl.c:994
       process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
       process_scheduled_works kernel/workqueue.c:3405 [inline]
       worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
       kthread+0x370/0x450 kernel/kthread.c:436
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #2 (console_lock){+.+.}-{0:0}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       console_lock+0x7a/0xa0 kernel/printk/printk.c:2896
       uart_configure_port drivers/tty/serial/serial_core.c:2530 [inline]
       serial_core_add_one_port drivers/tty/serial/serial_core.c:3101 [inline]
       serial_core_register_port+0xe65/0x16f0 drivers/tty/serial/serial_core.c:3322
       serial8250_register_8250_port+0x15af/0x2330 drivers/tty/serial/8250/8250_core.c:828
       serial_pnp_probe+0x436/0x930 drivers/tty/serial/8250/8250_pnp.c:480
       pnp_device_probe+0x2b3/0x4a0 drivers/pnp/driver.c:111
       call_driver_probe drivers/base/dd.c:628 [inline]
       really_probe+0x241/0xa60 drivers/base/dd.c:706
       __driver_probe_device+0x20e/0x450 drivers/base/dd.c:868
       driver_probe_device+0x4a/0x140 drivers/base/dd.c:898
       __driver_attach+0x21f/0x5b0 drivers/base/dd.c:1292
       bus_for_each_dev+0x13e/0x1d0 drivers/base/bus.c:383
       bus_add_driver+0x305/0x5b0 drivers/base/bus.c:763
       driver_register+0x1e2/0x360 drivers/base/driver.c:174
       serial8250_init+0xcc/0x1c0 drivers/tty/serial/8250/8250_platform.c:317
       do_one_initcall+0x11d/0x700 init/main.c:1347
       do_initcall_level init/main.c:1409 [inline]
       do_initcalls init/main.c:1425 [inline]
       do_basic_setup init/main.c:1445 [inline]
       kernel_init_freeable+0x6ea/0x7b0 init/main.c:1658
       kernel_init+0x1f/0x1e0 init/main.c:1548
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #1 (&port->mutex){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       class_mutex_constructor include/linux/mutex.h:253 [inline]
       uart_set_termios+0x8e/0x690 drivers/tty/serial/serial_core.c:1645
       tty_set_termios+0x64d/0x980 drivers/tty/tty_ioctl.c:341
       set_termios+0x5c8/0x880 drivers/tty/tty_ioctl.c:516
       tty_mode_ioctl+0x17e/0xd40 drivers/tty/tty_ioctl.c:803
       n_tty_ioctl_helper+0x47/0x2b0 drivers/tty/tty_ioctl.c:982
       n_tty_ioctl+0x53/0x340 drivers/tty/n_tty.c:2496
       tty_ioctl+0x11b4/0x1640 drivers/tty/tty_io.c:2801
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl fs/ioctl.c:583 [inline]
       __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x115/0x840 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&tty->termios_rwsem){++++}-{4:4}:
       check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       down_read+0x99/0x4c0 kernel/locking/rwsem.c:1574
       class_rwsem_read_constructor include/linux/rwsem.h:259 [inline]
       n_tty_receive_buf_common+0x85/0x1930 drivers/tty/n_tty.c:1678
       tty_ldisc_receive_buf+0xaa/0x1a0 drivers/tty/tty_buffer.c:394
       tty_port_default_receive_buf+0x70/0xb0 drivers/tty/tty_port.c:37
       receive_buf drivers/tty/tty_buffer.c:452 [inline]
       flush_to_ldisc+0x26b/0x730 drivers/tty/tty_buffer.c:502
       process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
       process_scheduled_works kernel/workqueue.c:3405 [inline]
       worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
       kthread+0x370/0x450 kernel/kthread.c:436
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

other info that might help us debug this:

Chain exists of:
  &tty->termios_rwsem --> console_lock --> &buf->lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&buf->lock);
                               lock(console_lock);
                               lock(&buf->lock);
  rlock(&tty->termios_rwsem);

 *** DEADLOCK ***

4 locks held by kworker/u33:3/62:
 #0: ffff88801bce4140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x12b1/0x1940 kernel/workqueue.c:3297
 #1: ffffc900009efd08 ((work_completion)(&buf->work)){+.+.}-{0:0}, at: process_one_work+0x988/0x1940 kernel/workqueue.c:3298
 #2: ffff88801404a8b8 (&buf->lock){+.+.}-{4:4}, at: flush_to_ldisc+0x34/0x730 drivers/tty/tty_buffer.c:474
 #3: ffff88804b3fe0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref+0x21/0x90 drivers/tty/tty_ldisc.c:263

stack backtrace:
CPU: 0 UID: 0 PID: 62 Comm: kworker/u33:3 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: events_unbound flush_to_ldisc
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_circular_bug.cold+0x178/0x1c7 kernel/locking/lockdep.c:2043
 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2175
 check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237
 lock_acquire kernel/locking/lockdep.c:5868 [inline]
 lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
 down_read+0x99/0x4c0 kernel/locking/rwsem.c:1574
 class_rwsem_read_constructor include/linux/rwsem.h:259 [inline]
 n_tty_receive_buf_common+0x85/0x1930 drivers/tty/n_tty.c:1678
 tty_ldisc_receive_buf+0xaa/0x1a0 drivers/tty/tty_buffer.c:394
 tty_port_default_receive_buf+0x70/0xb0 drivers/tty/tty_port.c:37
 receive_buf drivers/tty/tty_buffer.c:452 [inline]
 flush_to_ldisc+0x26b/0x730 drivers/tty/tty_buffer.c:502
 process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
 process_scheduled_works kernel/workqueue.c:3405 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Current Strategy: To trigger the `console_lock` -> `&buf->lock` dependency without relying on `/proc/sysrq-trigger` (which might be disabled or restricted), we can use the VT keyboard driver. 

The function `vc_SAK` takes `console_lock` and then calls `__do_SAK`, which takes `&buf->lock`. `vc_SAK` is scheduled by `fn_SAK`, which is triggered when the keyboard driver receives a key mapped to the `K_SAK` keysym. 

We can dynamically map a normal key (e.g., `KEY_A`) to `K_SAK` using the `KDSKBENT` ioctl on a VT device (like `/dev/tty0`). Then, we can inject a `KEY_A` keypress using a virtual input device via `/dev/uinput`. This will simulate the SAK key combination and execute `vc_SAK`, recording the required lock dependency.

### Minimal C Reproducer

```c
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <stdlib.h>
#include <linux/kd.h>
#include <linux/uinput.h>
#include <string.h>
#include <stdio.h>

int main(void) {
    // 1. Trigger: &tty->termios_rwsem -> &port->mutex
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial >= 0) {
        struct termios term;
        if (ioctl(fd_serial, TCGETS, &term) == 0) {
            ioctl(fd_serial, TCSETS, &term);
        }
        close(fd_serial);
    }

    // 2. Trigger: console_lock -> &buf->lock
    // Map KEY_A (keycode 30) to K_SAK (0x020F)
    int fd_tty = open("/dev/tty0", O_RDWR);
    if (fd_tty < 0) fd_tty = open("/dev/tty1", O_RDWR);
    if (fd_tty < 0) fd_tty = open("/dev/console", O_RDWR);
    
    if (fd_tty >= 0) {
        struct kbentry ke;
        ke.kb_table = 0;
        ke.kb_index = 30; // KEY_A
        ke.kb_value = 0x020F; // K_SAK
        ioctl(fd_tty, KDSKBENT, &ke);
        close(fd_tty);
    }

    // Inject KEY_A via uinput to trigger fn_SAK -> vc_SAK
    int ufd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
    if (ufd >= 0) {
        ioctl(ufd, UI_SET_EVBIT, EV_KEY);
        ioctl(ufd, UI_SET_KEYBIT, KEY_A);

        struct uinput_setup usetup;
        memset(&usetup, 0, sizeof(usetup));
        usetup.id.bustype = BUS_USB;
        usetup.id.vendor = 0x1234;
        usetup.id.product = 0x5678;
        strcpy(usetup.name, "Virtual Keyboard");
        ioctl(ufd, UI_DEV_SETUP, &usetup);
        ioctl(ufd, UI_DEV_CREATE);

        usleep(100000); // wait for input device to be registered

        struct input_event ie;
        
        // Press KEY_A
        memset(&ie, 0, sizeof(ie));
        ie.type = EV_KEY;
        ie.code = KEY_A;
        ie.value = 1;
        write(ufd, &ie, sizeof(ie));

        memset(&ie, 0, sizeof(ie));
        ie.type = EV_SYN;
        ie.code = SYN_REPORT;
        ie.value = 0;
        write(ufd, &ie, sizeof(ie));

        // Release KEY_A
        memset(&ie, 0, sizeof(ie));
        ie.type = EV_KEY;
        ie.code = KEY_A;
        ie.value = 0;
        write(ufd, &ie, sizeof(ie));

        memset(&ie, 0, sizeof(ie));
        ie.type = EV_SYN;
        ie.code = SYN_REPORT;
        ie.value = 0;
        write(ufd, &ie, sizeof(ie));

        usleep(100000); // wait for vc_SAK workqueue to execute
        ioctl(ufd, UI_DEV_DESTROY);
        close(ufd);
    }

    // 3. Trigger: &buf->lock -> &tty->termios_rwsem
    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx >= 0) {
        grantpt(ptmx);
        unlockpt(ptmx);
        char *pts_name = ptsname(ptmx);
        if (pts_name) {
            int pts = open(pts_name, O_RDWR | O_NOCTTY);
            if (pts >= 0) {
                // Writing to the slave PTY triggers flush_to_ldisc on the master PTY
                write(pts, "a", 1);
                // Wait a bit for the flush_to_ldisc workqueue to execute
                usleep(100000);
                close(pts);
            }
        }
        close(ptmx);
    }

    return 0;
}
```
Feedback: The environment probe was successful. All required devices (/dev/ttyS0, /dev/tty0, /dev/uinput, /dev/ptmx) were opened successfully. The environment is ready. Please proceed to generate the full reproducer in the next iteration.

An analysis of the lockdep splat reveals the following circular dependency chain:

1. `&port->mutex` -> `console_lock`: Established during boot when `serial8250_register_8250_port` registers the serial console. `serial_core_register_port` holds `&port->mutex` and calls `uart_configure_port`, which acquires `console_lock`.
2. `&tty->termios_rwsem` -> `&port->mutex`: Established when setting terminal attributes (e.g., `TCSETS` ioctl) on a serial port. `tty_set_termios` holds a write lock on `&tty->termios_rwsem` and calls `uart_set_termios`, which acquires `&port->mutex`.
3. `console_lock` -> `&buf->lock`: Established by the Secure Attention Key (SAK) handler. `vc_SAK` acquires `console_lock` and calls `__do_SAK`, which flushes the TTY buffers and acquires `&buf->lock`.
4. `&buf->lock` -> `&tty->termios_rwsem`: Established when receiving data on a TTY (e.g., a PTY). `flush_to_ldisc` holds `&buf->lock` and pushes data to the line discipline, calling `n_tty_receive_buf_common`, which acquires a read lock on `&tty->termios_rwsem`.

To trigger this deadlock reliably, we need to establish dependencies 2, 3, and 4 in sequence (dependency 1 is already established at boot). We can do this by:
1. Calling `TCSETS` on `/dev/ttyS0`.
2. Injecting a SAK key sequence via `uinput` to trigger `vc_SAK`. We do this in a child process because `__do_SAK` sends `SIGKILL` to processes associated with the active console.
3. Writing data to a PTY master to trigger `flush_to_ldisc` on the slave.

Here is the complete C reproducer:

```c
// autogenerated by syzkaller (https://github.com/google/syzkaller)

#define _GNU_SOURCE
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <stdlib.h>
#include <linux/kd.h>
#include <linux/uinput.h>
#include <string.h>
#include <stdio.h>
#include <sys/wait.h>

void trigger_tcsets() {
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS1", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS2", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS3", O_RDWR | O_NOCTTY);
    if (fd_serial >= 0) {
        struct termios term;
        if (ioctl(fd_serial, TCGETS, &term) == 0) {
            ioctl(fd_serial, TCSETS, &term);
        }
        close(fd_serial);
    }
}

void trigger_sak() {
    int fd_tty = open("/dev/tty0", O_RDWR);
    if (fd_tty < 0) fd_tty = open("/dev/tty1", O_RDWR);
    if (fd_tty < 0) fd_tty = open("/dev/console", O_RDWR);
    
    if (fd_tty >= 0) {
        // Map KEY_A to K_SAK across all keymaps to ensure it triggers
        for (int i = 0; i < 256; i++) {
            struct kbentry ke;
            ke.kb_table = i;
            ke.kb_index = 30; // KEY_A
            ke.kb_value = 0x020F; // K_SAK
            ioctl(fd_tty, KDSKBENT, &ke);
        }
        close(fd_tty);
    }

    int ufd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
    if (ufd >= 0) {
        ioctl(ufd, UI_SET_EVBIT, EV_KEY);
        ioctl(ufd, UI_SET_KEYBIT, KEY_A);

        struct uinput_setup usetup;
        memset(&usetup, 0, sizeof(usetup));
        usetup.id.bustype = BUS_USB;
        usetup.id.vendor = 0x1234;
        usetup.id.product = 0x5678;
        strcpy(usetup.name, "Virtual Keyboard");
        ioctl(ufd, UI_DEV_SETUP, &usetup);
        ioctl(ufd, UI_DEV_CREATE);

        usleep(100000); // Wait for input device to be registered

        struct input_event ie;
        
        // Press KEY_A
        memset(&ie, 0, sizeof(ie));
        ie.type = EV_KEY; ie.code = KEY_A; ie.value = 1;
        write(ufd, &ie, sizeof(ie));

        memset(&ie, 0, sizeof(ie));
        ie.type = EV_SYN; ie.code = SYN_REPORT; ie.value = 0;
        write(ufd, &ie, sizeof(ie));

        // Release KEY_A
        memset(&ie, 0, sizeof(ie));
        ie.type = EV_KEY; ie.code = KEY_A; ie.value = 0;
        write(ufd, &ie, sizeof(ie));

        memset(&ie, 0, sizeof(ie));
        ie.type = EV_SYN; ie.code = SYN_REPORT; ie.value = 0;
        write(ufd, &ie, sizeof(ie));

        usleep(500000); // Wait for vc_SAK workqueue to execute
        ioctl(ufd, UI_DEV_DESTROY);
        close(ufd);
    }
}

void trigger_pty() {
    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx >= 0) {
        grantpt(ptmx);
        unlockpt(ptmx);
        char *pts_name = ptsname(ptmx);
        if (pts_name) {
            int pts = open(pts_name, O_RDWR | O_NOCTTY);
            if (pts >= 0) {
                // Writing to the master PTY triggers flush_to_ldisc on the slave PTY
                write(ptmx, "a", 1);
                usleep(100000); // Wait for flush_to_ldisc workqueue to execute
                close(pts);
            }
        }
        close(ptmx);
    }
}

int main(void) {
    // 1. Trigger &tty->termios_rwsem -> &port->mutex
    trigger_tcsets();

    // 2. Trigger console_lock -> &buf->lock
    // Do this in a child process because __do_SAK sends SIGKILL to processes
    // associated with the active console.
    pid_t pid = fork();
    if (pid == 0) {
        trigger_sak();
        exit(0);
    }
    waitpid(pid, NULL, 0);

    // 3. Trigger &buf->lock -> &tty->termios_rwsem
    // This completes the circular dependency and triggers the lockdep splat.
    trigger_pty();

    return 0;
}
```

gemini-3.1-pro-preview

							input: 7493
							output: 29
							thoughts: 2371
						

**My Thoughts on Debugging the `n_tty_receive_buf_common` Deadlock**

Alright, I've been diving deep into this `possible deadlock in n_tty_receive_buf_common` bug, and I think I've pieced together the lock dependency chain that's causing the issue. It's a bit of a tangled web, but here's how I'm seeing it play out:

First, the core of the problem seems to stem from the interaction between acquiring `&tty->termios_rwsem` in `n_tty_receive_buf_common` when the task already holds `&buf->lock`. Lockdep is telling me that the existing dependency chain, when read in reverse order of acquisition, is:

*   **#3: `&buf->lock`**
*   **#2: `console_lock`** (which, importantly, depends on `&buf->lock`)
*   **#1: `&port->mutex`** (which, in turn, depends on `console_lock`)
*   **#0: `&tty->termios_rwsem`** (which is the lock we're trying to acquire in the buggy path and depends on `&port->mutex`)

So, to break this down into actual lock dependencies:

1.  **`&tty->termios_rwsem` -> `&port->mutex`**: I've traced this back to the `TCSETS` ioctl call on a serial port (`/dev/ttyS0`). The path appears to be `tty_ioctl` -> `n_tty_ioctl` -> `n_tty_ioctl_helper` -> `tty_mode_ioctl` -> `set_termios` -> `tty_set_termios` (which acquires `&tty->termios_rwsem` in write mode) -> `uart_set_termios` (which acquires `&port->mutex`). This establishes the initial dependency.

2.  **`&port->mutex` -> `console_lock`**: This dependency seems to be established early on during system boot. Specifically, `serial_core_register_port` acquires `&port->mutex` and then calls `uart_configure_port`, which in turn acquires `console_lock`. Lockdep has already recorded this because it happens during the core serial port registration process.

3.  **`console_lock` -> `&buf->lock`**: This is where the virtual keyboard interrupt handler, `vc_SAK`, comes into play. When the `K_SAK` key is pressed, `vc_SAK` is scheduled. This handler acquires `console_lock()` and then calls `__do_SAK()`. Within `__do_SAK`, it iterates through associated ttys and calls `tty_ldisc_flush`, which eventually leads to `tty_buffer_flush` acquiring `&buf->lock`. This establishes the final step needed for the deadlock.

Now, the critical piece is that when `n_tty_receive_buf_common` attempts to acquire `&tty->termios_rwsem` (read lock), the task already holds `&buf->lock`. Lockdep, seeing the established chain `&tty->termios_rwsem` -> `&port->mutex` -> `console_lock` -> `&buf->lock`, is essentially saying: "You're trying to acquire a lock (`&tty->termios_rwsem`) that is depended upon by a lock you already hold (`&buf->lock`), but the dependency chain is in the wrong order for this specific acquisition path." More accurately, the bug is that `n_tty_receive_buf_common` needs `&tty->termios_rwsem` (read) *after* `flush_to_ldisc` has acquired `&buf->lock`. And `flush_to_ldisc` calls `tty_buffer_flush` which takes `&buf->lock`. The lockdep report implies a circular dependency: `&buf->lock` -> `&tty->termios_rwsem`.

The previous iteration of my attempt to reproduce this successfully probed the environment, confirming that all necessary devices (`/dev/ttyS0`, `/dev/tty0`, `/dev/uinput`, `/dev/ptmx`) were available. This means my strategy for triggering these lock acquisitions in the correct sequence is sound.

My plan is to construct a C reproducer that sequentially triggers these events:

1.  Initiate the `TCSETS` ioctl on `/dev/ttyS0` to establish the `&tty->termios_rwsem` -> `&port->mutex` dependency.
2.  Inject a virtual keypress that maps to `K_SAK` (using `/dev/uinput`) to trigger `vc_SAK` and consequently acquire `console_lock` and then `&buf->lock`.
3.  Finally, perform an operation that involves `flush_to_ldisc` (perhaps by writing to a PTY) to acquire `&buf->lock` and then attempt to acquire `&tty->termios_rwsem` in `n_tty_receive_buf_common`, thereby hitting the deadlock.

Since lockdep records dependencies globally, a sequential execution of these steps should be sufficient to expose the bug. Concurrency isn't strictly necessary for lockdep to detect the problem, and sequential execution offers better reliability in ensuring each step happens in the intended order. I'm confident that generating the full C reproducer based on this understanding will reliably trigger the deadlock.

map[ContextFile: Name:__do_SAK]

map[SourceCode:2997:	/*
2998:	 * This implements the "Secure Attention Key" ---  the idea is to
2999:	 * prevent trojan horses by killing all processes associated with this
3000:	 * tty when the user hits the "Secure Attention Key".  Required for
3001:	 * super-paranoid applications --- see the Orange Book for more details.
3002:	 *
3003:	 * This code could be nicer; ideally it should send a HUP, wait a few
3004:	 * seconds, then send a INT, and then a KILL signal.  But you then
3005:	 * have to coordinate with the init process, since all processes associated
3006:	 * with the current tty must be dead before the new getty is allowed
3007:	 * to spawn.
3008:	 *
3009:	 * Now, if it would be correct ;-/ The current code has a nasty hole -
3010:	 * it doesn't catch files in flight. We may send the descriptor to ourselves
3011:	 * via AF_UNIX socket, close it and later fetch from socket. FIXME.
3012:	 *
3013:	 * Nasty bug: do_SAK is being called in interrupt context.  This can
3014:	 * deadlock.  We punt it up to process context.  AKPM - 16Mar2001
3015:	 */
3016:	void __do_SAK(struct tty_struct *tty)
3017:	{
3018:		struct task_struct *g, *p;
3019:		struct pid *session;
3020:		int i;
3021:	
3022:		scoped_guard(spinlock_irqsave, &tty->ctrl.lock)
3023:			session = get_pid(tty->ctrl.session);
3024:	
3025:		tty_ldisc_flush(tty);
3026:	
3027:		tty_driver_flush_buffer(tty);
3028:	
3029:		read_lock(&tasklist_lock);
3030:		/* Kill the entire session */
3031:		do_each_pid_task(session, PIDTYPE_SID, p) {
3032:			tty_notice(tty, "SAK: killed process %d (%s): by session\n",
3033:				   task_pid_nr(p), p->comm);
3034:			group_send_sig_info(SIGKILL, SEND_SIG_PRIV, p, PIDTYPE_SID);
3035:		} while_each_pid_task(session, PIDTYPE_SID, p);
3036:	
3037:		/* Now kill any processes that happen to have the tty open */
3038:		for_each_process_thread(g, p) {
3039:			if (p->signal->tty == tty) {
3040:				tty_notice(tty, "SAK: killed process %d (%s): by controlling tty\n",
3041:					   task_pid_nr(p), p->comm);
3042:				group_send_sig_info(SIGKILL, SEND_SIG_PRIV, p,
3043:						PIDTYPE_SID);
3044:				continue;
3045:			}
3046:			guard(task_lock)(p);
3047:			i = iterate_fd(p->files, 0, this_tty, tty);
3048:			if (i != 0) {
3049:				tty_notice(tty, "SAK: killed process %d (%s): by fd#%d\n",
3050:					   task_pid_nr(p), p->comm, i - 1);
3051:				group_send_sig_info(SIGKILL, SEND_SIG_PRIV, p,
3052:						PIDTYPE_SID);
3053:			}
3054:		}
3055:		read_unlock(&tasklist_lock);
3056:		put_pid(session);
3057:	}
 SourceFile:drivers/tty/tty_io.c]

gemini-3.1-pro-preview

							input: 10975
							output: 28
							thoughts: 34
						

**My Thought Process Regarding `__do_SAK` and `vc_SAK`**

Alright, so I'm looking at this function, `__do_SAK`. My initial observation is that it expects a `struct tty_struct *tty` as its argument. This is a crucial piece of information, as it immediately tells me this function is operating at a level that interacts directly with the terminal device itself. My immediate next step, given this understanding, is to investigate how `vc_SAK` relates to this. I need to see what `vc_SAK` does and how it uses or is used in conjunction with the `tty` structure that `__do_SAK` receives. This will likely involve tracing the call chain and examining the internal workings of `vc_SAK` to understand its purpose and its connection to the Secure Access Key (SAK) mechanism within the TTY subsystem.

map[ContextFile: Name:vc_SAK]

map[SourceCode: 978:	void vc_SAK(struct work_struct *work)
 979:	{
 980:		struct vc *vc_con =
 981:			container_of(work, struct vc, SAK_work);
 982:		struct vc_data *vc;
 983:		struct tty_struct *tty;
 984:	
 985:		guard(console_lock)();
 986:		vc = vc_con->d;
 987:		if (!vc)
 988:			return;
 989:	
 990:		/* FIXME: review tty ref counting */
 991:		tty = vc->port.tty;
 992:		/* SAK should also work in all raw modes and reset them properly. */
 993:		if (tty)
 994:			__do_SAK(tty);
 995:		reset_vc(vc);
 996:	}
 SourceFile:drivers/tty/vt/vt_ioctl.c]

gemini-3.1-pro-preview

							input: 11307
							output: 20
							thoughts: 2332
						

**My Thought Process on Reproducing a Lock Dependency Issue**

I've been analyzing a report detailing a circular lock dependency that occurs within the kernel's TTY (teletypewriter) subsystem. My goal is to reproduce this issue reliably so I can understand and potentially fix it. Here's how I'm approaching it, step by step, based on the information I have.

First, I need to ensure that the `vc_SAK` function, which handles the "Secure Attention Key" (SAK) event, can access the TTY device. This function expects to find a valid `tty` pointer, which it gets from `vc->port.tty`. For `vc->port.tty` to be populated, the Virtual Console (VT) associated with it must be opened. Therefore, before I even think about injecting the SAK key, my absolute first step must be to open a VT device, like `/dev/tty1` or `/dev/tty0`. This guarantees that the necessary TTY structure is initialized and available.

Next, I need to understand how to trigger a specific lock dependency: `&buf->lock` acquiring `&tty->termios_rwsem`. The report indicates this chain of calls: `n_tty_receive_buf_common` -> `tty_ldisc_receive_buf` -> `tty_port_default_receive_buf` -> `receive_buf` -> `flush_to_ldisc`. The crucial part here is that `flush_to_ldisc` takes ownership of `&buf->lock`. Subsequently, it calls into the TTY receive path, eventually leading to `n_tty_receive_buf_common`, which acquires a read lock on `&tty->termios_rwsem`. This entire sequence is triggered when data is received on a TTY and passed to the line discipline.

A PTY (pseudo-terminal) is an ideal mechanism to simulate this TTY data reception. I can set up a PTY by opening the master (`/dev/ptmx`), granting and unlocking the slave using `grantpt` and `unlockpt`, and then opening the slave. Once that's done, I can write data to *either* the master or the slave. My understanding is that if I write to the master, the data flows to the slave's receive buffer, and `flush_to_ldisc` is scheduled for the slave. Conversely, writing to the slave sends data to the master's receive buffer, scheduling `flush_to_ldisc` for the master. Regardless of the direction, `flush_to_ldisc` will eventually execute, acquire `&buf->lock`, and then proceed to acquire `&tty->termios_rwsem`, thus establishing the `&buf->lock` -> `&tty->termios_rwsem` dependency.

Now, I need to establish the second lock dependency: `&tty->termios_rwsem` acquiring `&port->mutex`. The call trace here is: `uart_set_termios` -> `tty_set_termios` -> `set_termios` -> `tty_mode_ioctl` -> `n_tty_ioctl_helper` -> `n_tty_ioctl` -> `tty_ioctl`. The key observation is that `tty_set_termios` first acquires a write lock on `&tty->termios_rwsem`. Following that, it invokes the TTY driver's operations, specifically `tty->ops->set_termios`, which in turn calls `uart_set_termios`. This `uart_set_termios` function then acquires `&port->mutex`. This entire sequence is triggered when I execute the `TCSETS` ioctl on a serial port, such as `/dev/ttyS0`.

With these pieces understood, I can formulate the sequence of actions to trigger the circular dependency.

1.  **Establish `&tty->termios_rwsem` -> `&port->mutex`:** I'll open `/dev/ttyS0` and perform a `TCSETS` ioctl. This will ensure the `termios_rwsem` is locked (in write mode), and then the driver's `set_termios` operation will acquire the `port->mutex`.

2.  **Establish `&buf->lock` -> `&tty->termios_rwsem`:** I'll use a PTY. I'll open `/dev/ptmx`, set up the slave, and then write some data to the PTY master. This will trigger `flush_to_ldisc`, which will acquire `&buf->lock` and then `&tty->termios_rwsem` (in read mode).

3.  **Establish `console_lock` -> `&buf->lock` and trigger the final link:** This is where it gets tricky. The SAK mechanism is involved. I need to first configure a key (e.g., `KEY_A`) to act as the SAK on a VT device. I'll open `/dev/tty1` and use the `KDSKBENT` ioctl with `KEY_A` mapped to `K_SAK`. Then, I'll inject `KEY_A` using a `uinput` device. This injection will lead to `fn_SAK`, then `vc_SAK`. `vc_SAK` acquires the `console_lock` and then calls `__do_SAK`. Crucially, `__do_SAK` calls `tty_ldisc_flush`, which acquires `&buf->lock`. This establishes the `console_lock` -> `&buf->lock` dependency.

The critical realization comes when I consider the order. If I perform the SAK injection *after* the `TCSETS` ioctl and the PTY data write, the circular dependency will be completed at the point `vc_SAK` acquires `console_lock` and then `__do_SAK` calls `tty_ldisc_flush` which acquires `&buf->lock`. At this point, the complete chain `&tty->termios_rwsem` -> `&port->mutex` (from step 1), `&buf->lock` -> `&tty->termios_rwsem` (from step 2), and `console_lock` -> `&buf->lock` (from step 3) will be established. Lockdep, being active, should then detect the circular dependency and print the splat.

However, there's a significant pitfall with the SAK injection: `__do_SAK` sends `SIGKILL` to processes associated with the TTY. If my reproducer process has `/dev/tty1` open as its controlling terminal, it will be killed. This is problematic if I want the reproducer to run to completion and observe the lockdep output.

My initial thought was to fork a child process to handle the SAK injection. The child would be killed, but the parent might survive. But `SIGKILL` cannot be caught or ignored, so even a child might not be the cleanest solution. Another thought was to ignore the signal, but that's not possible.

The most elegant solution, given that lockdep prints the splat *immediately* upon detecting the circular dependency, is to perform the SAK injection as the *very last step* in my sequence. The `vc_SAK` function runs in a workqueue thread, so that thread will be the one to detect the circular dependency and print the splat. Even though my reproducer process will be killed by `SIGKILL` shortly after, the lockdep splat will already have been printed to the kernel logs. This means I don't need a complex fork or signal handling. I can just let the process die after the SAK is injected, knowing the crucial information has been captured.

So, the refined sequence of actions is:

1.  Execute a `TCSETS` ioctl on `/dev/ttyS0` to establish `&tty->termios_rwsem` -> `&port->mutex`.
2.  Write data to a PTY master to trigger `flush_to_ldisc` and establish `&buf->lock` -> `&tty->termios_rwsem`.
3.  Map `KEY_A` to `K_SAK` on `/dev/tty1`.
4.  Inject `KEY_A` via `uinput` to trigger `vc_SAK` and establish `console_lock` -> `&buf->lock`, completing the circular dependency.
5.  Allow the reproducer process to be killed by the `SIGKILL` signal as a consequence of the SAK.

I'll need to be mindful of the necessary capabilities (like `CAP_SYS_TTY_CONFIG` for `KDSKBENT`, which syzkaller usually has by default as root) and ensure sufficient delays (`usleep`) are in place to allow the kernel's asynchronous operations (like workqueue execution) to complete between steps. I'll also verify the exact value for `K_SAK` from the relevant kernel headers.

map[Expression:#define K_SAK]

map[Output:include/uapi/linux/keyboard.h-322-#define K_COMPOSE	K(KT_SPEC,14)
include/uapi/linux/keyboard.h:323:#define K_SAK		K(KT_SPEC,15)
include/uapi/linux/keyboard.h-324-#define K_DECRCONSOLE	K(KT_SPEC,16)
]

gemini-3.1-pro-preview

							input: 13753
							output: 18
							thoughts: 16
						

**My Thought Process for Verifying `K(KT_SPEC, 15)`**

Alright, so my first inclination is to directly interrogate this value: `K(KT_SPEC, 15)`. My immediate thought is, "What exactly *is* this `K` function, and what does it represent in the context of `KT_SPEC`? And what's the significance of the number `15`?" I'm assuming `KT_SPEC` is some kind of defined set, specification, or perhaps a data structure that holds relevant parameters or entities. The `K` function, given its common use in mathematical and computational contexts, likely signifies some form of operation, transformation, or retrieval. The argument `15` could be an index, a specific parameter value, a threshold, or even a particular instance or iteration.

My next step would be to delve into the definition of `K` as it pertains to `KT_SPEC`. I'd be looking for its formal definition – is it a known algorithm, a custom function, or an inherent property? Does it operate on the *entirety* of `KT_SPEC`, or on a specific subset or element dictated by the `15`? I need to understand its input and output. What data types does it expect, and what does it produce? Is the output a scalar value, a vector, a matrix, a boolean, or something else entirely?

Then, I need to contextualize the `15`. If `KT_SPEC` is a sequence or an array-like structure, then `15` is almost certainly an index. In that case, I'd be focusing on the *fifteenth* element or aspect of `KT_SPEC` and how the function `K` interacts with it. If `KT_SPEC` is more abstract, `15` could be a key, a specific attribute, or a condition. My mind immediately jumps to thinking about the *validity* of `15` within the bounds of `KT_SPEC`. Is `15` a valid index? Does `KT_SPEC` even *have* 15 elements or define a parameter with that label?

Ultimately, my goal in checking `K(KT_SPEC, 15)` is to ascertain its *meaning and effect* within the larger system or problem I'm addressing. I'm trying to understand if this particular invocation is:

*   **Correct:** Does it represent a valid operation?
*   **Relevant:** Does it contribute to the desired outcome?
*   **Consistent:** Does it align with established principles or previous calculations?
*   **Efficient:** Is this the most direct or optimized way to achieve whatever it's supposed to do?

So, the thought process is essentially: dissect the components (`K`, `KT_SPEC`, `15`), understand their individual roles, and then synthesize that understanding to grasp the overall implication of the expression `K(KT_SPEC, 15)`. It's a diagnostic step, a sanity check, and a gateway to further analysis or action.

map[Expression:#define K\(]

map[Output:arch/x86/crypto/serpent-sse2-i586-asm_32.S-41-
arch/x86/crypto/serpent-sse2-i586-asm_32.S:42:#define K(x0, x1, x2, x3, x4, i) \
arch/x86/crypto/serpent-sse2-i586-asm_32.S-43-	get_key(i, 0, x4); \
--
crypto/serpent_generic.c-35-
crypto/serpent_generic.c:36:#define K(x0, x1, x2, x3, i) ({				\
crypto/serpent_generic.c-37-	x3 ^= k[4*(i)+3];        x2 ^= k[4*(i)+2];	\
--
drivers/base/node.c=437=static void node_remove_caches(struct node *node) { }
--
drivers/base/node.c-439-
drivers/base/node.c:440:#define K(x) ((x) << (PAGE_SHIFT - 10))
drivers/base/node.c-441-static ssize_t node_read_meminfo(struct device *dev,
--
include/uapi/linux/keyboard.h-45-
include/uapi/linux/keyboard.h:46:#define K(t,v)		(((t)<<8)|(v))
include/uapi/linux/keyboard.h-47-#define KTYP(x)		((x) >> 8)
--
kernel/debug/kdb/kdb_main.c=2383=static int kdb_summary(int argc, const char **argv)
--
kernel/debug/kdb/kdb_main.c-2414-	/* Display in kilobytes */
kernel/debug/kdb/kdb_main.c:2415:#define K(x) ((x) << (PAGE_SHIFT - 10))
kernel/debug/kdb/kdb_main.c-2416-	kdb_printf("\nMemTotal:       %8lu kB\nMemFree:        %8lu kB\n"
--
mm/internal.h=636=void set_recommended_min_free_kbytes(void);
--
mm/internal.h-640- */
mm/internal.h:641:#define K(x) ((x) << (PAGE_SHIFT-10))
mm/internal.h-642-
--
tools/testing/memblock/internal.h=9=static int memblock_debug = 1;
--
tools/testing/memblock/internal.h-13-
tools/testing/memblock/internal.h:14:#define K(x) ((x) << (PAGE_SHIFT-10))
tools/testing/memblock/internal.h-15-
]

gemini-3.1-pro-preview

							input: 14503
							output: 19
							thoughts: 7
						

**My Internal Monologue on KT_SPEC**

Ah, so the discussion has turned to `KT_SPEC`. My mind immediately goes to its purpose and implications within our field. I'm contemplating its current state, its intended function, and whether it's truly living up to its potential or if there are areas ripe for refinement. I'm also considering its relationship with other components or frameworks we're working with – does it integrate seamlessly, or are there friction points? I'm trying to anticipate potential challenges or opportunities that arise directly from `KT_SPEC`'s presence, and perhaps even considering its future trajectory. Essentially, I'm running through a mental checklist of its significance and impact.

map[Expression:#define KT_SPEC]

map[Output:include/uapi/linux/keyboard.h-30-#define KT_FN		1
include/uapi/linux/keyboard.h:31:#define KT_SPEC		2
include/uapi/linux/keyboard.h-32-#define KT_PAD		3
]

gemini-3.1-pro-preview

							input: 14592
							output: 27
							thoughts: 3921
						

**My Journey Through Kernel Lock Dependencies and the SAK Vulnerability**

I've been deep-diving into a rather intricate kernel locking issue, and I think I've finally pieced together the complete picture. It all started with understanding a specific value: `K_SAK` being calculated as `(2 << 8) | 15`, which correctly resolves to `0x020F`. This initial calculation confirmed my understanding of a key piece of data involved.

My next step was to meticulously trace the execution flow of `tty_ldisc_flush` and `__do_SAK`. I noted that both these functions operate on a `tty` structure. `tty_ldisc_flush` itself calls `tty_buffer_flush`, which, in turn, requires access to `tty->port` and, crucially, `&buf->lock`. This confirmed my initial hypothesis that `__do_SAK`, through its call to `tty_ldisc_flush`, would indeed acquire `&buf->lock`. The presence of `tty->port` for devices like `/dev/tty1` was a crucial detail here.

A critical question then arose: could the `vc_SAK` function, which is central to this problem, be prevented from executing if a `SAK_work` item was already pending? My thought was that a simple delay after injecting the key might resolve this. I also considered the importance of ensuring the input device was properly registered, recalling that a `usleep(100000)` after `UI_DEV_CREATE` usually suffices for this.

The core of the puzzle, however, lay in identifying *all* the ways `console_lock` could lead to the acquisition of `&buf->lock`, and how this might interact with other lock dependencies. The report provided a vital clue: the stack traces showed that `console_lock` was being acquired within `uart_configure_port`. This was a significant deviation from my initial expectation.

Then, I noticed how the report detailed the lock acquisition stacks *for each lock that established the dependency*. This was the key to understanding the chain:

1.  **`&buf->lock` acquisition:** This was clearly established within `__do_SAK`, which then called `tty_ldisc_flush`. This function, as I'd confirmed, eventually leads to `tty_buffer_flush` acquiring `&buf->lock`.
2.  **`console_lock` acquisition:** The report showed this happening in `uart_configure_port`. This, in turn, meant that `serial_core_register_port` must have held `&port->mutex` beforehand. This establishes the dependency `&port->mutex` -> `console_lock`.
3.  **`&port->mutex` acquisition:** This was found to be held by `uart_set_termios`, which was called by `tty_set_termios`, which in turn holds `&tty->termios_rwsem`. This creates the dependency `&tty->termios_rwsem` -> `&port->mutex`.
4.  **`&tty->termios_rwsem` acquisition:** This was happening in `n_tty_receive_buf_common`, which is called by `flush_to_ldisc`. Crucially, `flush_to_ldisc` acquires `&buf->lock` *before* calling `n_tty_receive_buf_common`. This establishes the final link in the chain: `&buf->lock` -> `&tty->termios_rwsem`.

My analysis of these four dependencies aligned perfectly with the report:

*   `&port->mutex` -> `console_lock`
*   `&tty->termios_rwsem` -> `&port->mutex`
*   `console_lock` -> `&buf->lock`
*   `&buf->lock` -> `&tty->termios_rwsem`

This forms a perfect circular dependency, a deadlock waiting to happen! The report's phrasing, "which lock already depends on the new lock," indicated the precise order lockdep was observing. The `&tty->termios_rwsem` acquisition was the "new lock" in `n_tty_receive_buf_common`, and the task already held `&buf->lock` in `flush_to_ldisc`. Therefore, the dependency being added was `&buf->lock` -> `&tty->termios_rwsem`.

I realized that the *order in which these dependencies are established* is critical for triggering the lockdep splat. While lockdep tracks all established dependencies, the *last one* to be established is the one that completes the circle and causes the crash. So, if `&buf->lock` -> `&tty->termios_rwsem` were established first, followed by `&tty->termios_rwsem` -> `&port->mutex`, and then `console_lock` -> `&buf->lock`, the circle would be completed by the third step, triggering the splat.

I also confirmed that the dependency `&port->mutex` -> `console_lock` is established at boot time, specifically during `serial8250_register_8250_port`, meaning I wouldn't need to explicitly trigger this one in my reproducer.

This understanding led me to devise a specific order for triggering these dependencies in my C reproducer:

1.  Trigger `&tty->termios_rwsem` -> `&port->mutex` by performing a `TCSETS` operation on `/dev/ttyS0`. I've made this more robust by attempting to open other `/dev/ttyS*` devices if `/dev/ttyS0` isn't available.
2.  Trigger `console_lock` -> `&buf->lock` by injecting a SAK key. To mitigate potential issues where `__do_SAK` might terminate the process holding the TTY, I decided to perform this action in a child process created via `fork()`. This also involves creating a virtual input device using `/dev/uinput` for key injection.
3.  Trigger `&buf->lock` -> `&tty->termios_rwsem` by writing to the master side of a PTY, which forces data into the slave's buffer, scheduling `flush_to_ldisc`.

I spent time scrutinizing `trigger_pty` to ensure the write operation to the master (`ptmx`) correctly led to the `flush_to_ldisc` on the slave and the subsequent acquisition of `&tty->termios_rwsem`. I also considered that lockdep handles both read and write locks, and while `tty_set_termios` uses a write lock, `n_tty_receive_buf_common` uses a read lock, a circular dependency involving these is still a valid deadlock scenario.

My reproducer is now written with these steps carefully ordered, and the logic for each function seems sound, aiming to precisely replicate the sequence of lock acquisitions that leads to the kernel panic. I'm confident this covers the entire dependency chain and provides a reliable way to demonstrate the vulnerability.

map[ContextFile: Name:tioclinux]

map[SourceCode:3561:	int tioclinux(struct tty_struct *tty, unsigned long arg)
3562:	{
3563:		char type, data;
3564:		char __user *p = (char __user *)arg;
3565:		void __user *param_aligned32 = (u32 __user *)arg + 1;
3566:		void __user *param = (void __user *)arg + 1;
3567:		int lines;
3568:		int ret;
3569:	
3570:		if (current->signal->tty != tty && !capable(CAP_SYS_ADMIN))
3571:			return -EPERM;
3572:		if (get_user(type, p))
3573:			return -EFAULT;
3574:		ret = 0;
3575:	
3576:		switch (type) {
3577:		case TIOCL_SETSEL:
3578:			return set_selection_user(param, tty);
3579:		case TIOCL_PASTESEL:
3580:			if (!capable(CAP_SYS_ADMIN))
3581:				return -EPERM;
3582:			return paste_selection(tty);
3583:		case TIOCL_UNBLANKSCREEN:
3584:			scoped_guard(console_lock)
3585:				unblank_screen();
3586:			break;
3587:		case TIOCL_SELLOADLUT:
3588:			if (!capable(CAP_SYS_ADMIN))
3589:				return -EPERM;
3590:			return sel_loadlut(param_aligned32);
3591:		case TIOCL_GETSHIFTSTATE:
3592:			/*
3593:			 * Make it possible to react to Shift+Mousebutton. Note that
3594:			 * 'shift_state' is an undocumented kernel-internal variable;
3595:			 * programs not closely related to the kernel should not use
3596:			 * this.
3597:			 */
3598:			data = vt_get_shift_state();
3599:			return put_user(data, p);
3600:		case TIOCL_GETMOUSEREPORTING:
3601:			scoped_guard(console_lock)	/* May be overkill */
3602:				data = mouse_reporting();
3603:			return put_user(data, p);
3604:		case TIOCL_SETVESABLANK:
3605:			return set_vesa_blanking(param);
3606:		case TIOCL_GETKMSGREDIRECT:
3607:			data = vt_get_kmsg_redirect();
3608:			return put_user(data, p);
3609:		case TIOCL_SETKMSGREDIRECT:
3610:			if (!capable(CAP_SYS_ADMIN))
3611:				return -EPERM;
3612:	
3613:			if (get_user(data, p+1))
3614:				return -EFAULT;
3615:	
3616:			vt_kmsg_redirect(data);
3617:	
3618:			break;
3619:		case TIOCL_GETFGCONSOLE:
3620:			/*
3621:			 * No locking needed as this is a transiently correct return
3622:			 * anyway if the caller hasn't disabled switching.
3623:			 */
3624:			return fg_console;
3625:		case TIOCL_SCROLLCONSOLE:
3626:			if (get_user(lines, (s32 __user *)param_aligned32))
3627:				return -EFAULT;
3628:	
3629:			/*
3630:			 * Needs the console lock here. Note that lots of other calls
3631:			 * need fixing before the lock is actually useful!
3632:			 */
3633:			scoped_guard(console_lock)
3634:				scrollfront(vc_cons[fg_console].d, lines);
3635:			break;
3636:		case TIOCL_BLANKSCREEN:	/* until explicitly unblanked, not only poked */
3637:			scoped_guard(console_lock) {
3638:				ignore_poke = 1;
3639:				do_blank_screen(0);
3640:			}
3641:			break;
3642:		case TIOCL_BLANKEDSCREEN:
3643:			return console_blanked;
3644:		case TIOCL_GETBRACKETEDPASTE:
3645:			return get_bracketed_paste(tty);
3646:		default:
3647:			return -EINVAL;
3648:		}
3649:	
3650:		return ret;
3651:	}
 SourceFile:drivers/tty/vt/vt.c]

gemini-3.1-pro-preview

							input: 19877
							output: 27
							thoughts: 23
						

**A Deep Dive into `paste_selection` and its Locking Mechanism**

My immediate thought upon encountering the phrase "`paste_selection` takes `&buf->lock`?" is one of cautious inquiry. As an expert in this domain, I know that such a question usually signals a need to scrutinize the intricate details of resource management and concurrency control within our codebase. My mental alarm bells are ringing, prompting me to investigate *why* this particular function might be acquiring a lock from a buffer. This isn't a trivial observation; it implies a dependency and a potential point of contention that needs thorough examination.

My next step is, naturally, to "check `paste_selection`." This isn't a casual glance. For me, this means initiating a comprehensive code review of the `paste_selection` function. I'm not just looking at its immediate signature and the lines of code directly within it. My focus will be on understanding its entire operational context.

Specifically, I'll be asking myself:

*   **What is the fundamental purpose of `paste_selection`?** Understanding its role in the system's workflow is paramount. Is it involved in copying data between different parts of the buffer, between buffers, or perhaps interacting with external systems? The "paste" operation itself suggests data manipulation, which inherently carries risks of race conditions.
*   **Why does it need a lock, and specifically *that* lock (`&buf->lock`)?** This is the core of my initial question. The presence of `&buf->lock` tells me that `paste_selection` is operating on or in relation to a specific buffer, and it needs to ensure exclusive access to that buffer's data or internal state. I'll be dissecting the code to identify *which* parts of the buffer's state are being accessed and modified. Is it the buffer's contents, its size, its metadata, or perhaps pointers to its internal structures?
*   **What are the potential concurrency issues that this lock is designed to prevent?** My expertise allows me to anticipate problems. Is this lock preventing data corruption if multiple threads try to paste into the same buffer simultaneously? Is it ensuring the atomicity of the paste operation, so it's either fully completed or not at all, from the perspective of other threads? Is it synchronizing with other operations that might be modifying the buffer concurrently, like reading, writing, or even resizing?
*   **What is the scope of the lock?** Does `paste_selection` acquire the lock at the very beginning and hold it until the very end, or are there more granular locking strategies in play? A broad lock can be a bottleneck, while overly granular locking can lead to deadlocks. I need to assess this trade-off.
*   **Are there any edge cases or specific scenarios where this lock might be problematic?** I'll be thinking about situations like:
    *   What happens if the `paste_selection` operation itself takes a long time? Will it block other essential operations on the buffer?
    *   Could this lock introduce a deadlock if another function that calls `paste_selection` also tries to acquire `&buf->lock` (or a related lock) in a different order?
    *   Are there any situations where the lock might *not* be acquired, leading to potential race conditions that the current design might have missed?
    *   How does this lock interact with other locking mechanisms in the system that might also be operating on the same buffer or related data structures?
*   **Is the locking mechanism correctly implemented?** Beyond just *having* a lock, I'll be verifying its usage. Is it acquired and released properly? Are there any potential paths where it might be missed? Are there any assertions or checks in place to validate the lock's state before operations?

In essence, "checking `paste_selection`" is my signal to embark on a thorough, critical analysis of how this function interacts with buffer resources in a concurrent environment. It's about understanding the 'why' behind the design decision to acquire this specific lock and ensuring that this mechanism is robust, efficient, and free from exploitable concurrency flaws. My goal is to confirm that the `&buf->lock` acquisition is a well-reasoned and correctly implemented safeguard.

map[ContextFile: Name:paste_selection]

map[SourceCode: 384:	/* Insert the contents of the selection buffer into the
 385:	 * queue of the tty associated with the current console.
 386:	 * Invoked by ioctl().
 387:	 *
 388:	 * Locking: called without locks. Calls the ldisc wrongly with
 389:	 * unsafe methods,
 390:	 */
 391:	int paste_selection(struct tty_struct *tty)
 392:	{
 393:		struct vc_data *vc = tty->driver_data;
 394:		int	pasted = 0;
 395:		size_t count;
 396:		struct  tty_ldisc *ld;
 397:		DECLARE_WAITQUEUE(wait, current);
 398:		int ret = 0;
 399:	
 400:		bool bp = vc->vc_bracketed_paste;
 401:		static const char bracketed_paste_start[] = "\033[200~";
 402:		static const char bracketed_paste_end[]   = "\033[201~";
 403:		const char *bps = bp ? bracketed_paste_start : NULL;
 404:		const char *bpe = bp ? bracketed_paste_end : NULL;
 405:	
 406:		scoped_guard(console_lock)
 407:			poke_blanked_console();
 408:	
 409:		ld = tty_ldisc_ref_wait(tty);
 410:		if (!ld)
 411:			return -EIO;	/* ldisc was hung up */
 412:		tty_buffer_lock_exclusive(&vc->port);
 413:	
 414:		add_wait_queue(&vc->paste_wait, &wait);
 415:		mutex_lock(&vc_sel.lock);
 416:		while (vc_sel.buffer && (vc_sel.buf_len > pasted || bpe)) {
 417:			set_current_state(TASK_INTERRUPTIBLE);
 418:			if (signal_pending(current)) {
 419:				ret = -EINTR;
 420:				break;
 421:			}
 422:			if (tty_throttled(tty)) {
 423:				mutex_unlock(&vc_sel.lock);
 424:				schedule();
 425:				mutex_lock(&vc_sel.lock);
 426:				continue;
 427:			}
 428:			__set_current_state(TASK_RUNNING);
 429:	
 430:			if (bps) {
 431:				bps += tty_ldisc_receive_buf(ld, bps, NULL, strlen(bps));
 432:				if (*bps != '\0')
 433:					continue;
 434:				bps = NULL;
 435:			}
 436:	
 437:			count = vc_sel.buf_len - pasted;
 438:			if (count) {
 439:				pasted += tty_ldisc_receive_buf(ld, vc_sel.buffer + pasted,
 440:								NULL, count);
 441:				if (vc_sel.buf_len > pasted)
 442:					continue;
 443:			}
 444:	
 445:			if (bpe) {
 446:				bpe += tty_ldisc_receive_buf(ld, bpe, NULL, strlen(bpe));
 447:				if (*bpe == '\0')
 448:					bpe = NULL;
 449:			}
 450:		}
 451:		mutex_unlock(&vc_sel.lock);
 452:		remove_wait_queue(&vc->paste_wait, &wait);
 453:		__set_current_state(TASK_RUNNING);
 454:	
 455:		tty_buffer_unlock_exclusive(&vc->port);
 456:		tty_ldisc_deref(ld);
 457:		return ret;
 458:	}
 SourceFile:drivers/tty/vt/selection.c]

gemini-3.1-pro-preview

							input: 21059
							output: 29
							thoughts: 103
						

**A Deep Dive into My Reasoning on Console Locking and Selection Handling**

Alright, let's trace this out in my head. I'm looking at `paste_selection` and trying to untangle the locking mechanisms it employs. My initial thought, a moment of almost alarm, is: "Wait a minute, `paste_selection` calls `tty_buffer_lock_exclusive(&vc->port)`. And `vc->port` *is* `&buf->lock`!" So, on the surface, it looks like `paste_selection` is acquiring `&buf->lock`.

But then I scrutinize it further, and my thought process shifts. The critical observation is that `paste_selection` *doesn't hold* `console_lock` when it acquires `&buf->lock`. It *does* grab `console_lock` for a fleeting moment, specifically to call `poke_blanked_console`. However, and this is the crucial part, it *releases* `console_lock` immediately after that call.

This means, in my understanding, the expected lock ordering of `console_lock` followed by `&buf->lock` is *not* established by `paste_selection` in its primary operation. It's a temporary acquisition and release of `console_lock`, not a persistent hold that's then combined with `&buf->lock`.

This leads me to the next logical question that immediately springs to mind: "Okay, if `paste_selection` doesn't establish this ordering, what about `set_selection_user`? Does *that* function handle the lock hierarchy differently or in conjunction with `paste_selection`?" That's where my focus is now, trying to see if `set_selection_user` is the piece of the puzzle that ensures the correct locking order is maintained when user-initiated selection operations occur.

map[ContextFile: Name:set_selection_user]

map[SourceCode: 176:	/**
 177:	 * set_selection_user - set the current selection.
 178:	 * @sel: user selection info
 179:	 * @tty: the console tty
 180:	 *
 181:	 * Invoked by the ioctl handle for the vt layer.
 182:	 *
 183:	 * Locking: The entire selection process is managed under the console_lock.
 184:	 * It's a lot under the lock but its hardly a performance path.
 185:	 */
 186:	int set_selection_user(const struct tiocl_selection __user *sel,
 187:			       struct tty_struct *tty)
 188:	{
 189:		struct tiocl_selection v;
 190:	
 191:		if (copy_from_user(&v, sel, sizeof(*sel)))
 192:			return -EFAULT;
 193:	
 194:		/*
 195:		 * TIOCL_SELCLEAR and TIOCL_SELPOINTER are OK to use without
 196:		 * CAP_SYS_ADMIN as they do not modify the selection.
 197:		 */
 198:		switch (v.sel_mode) {
 199:		case TIOCL_SELCLEAR:
 200:		case TIOCL_SELPOINTER:
 201:			break;
 202:		default:
 203:			if (!capable(CAP_SYS_ADMIN))
 204:				return -EPERM;
 205:		}
 206:	
 207:		return set_selection_kernel(&v, tty);
 208:	}
 SourceFile:drivers/tty/vt/selection.c]

gemini-3.1-pro-preview

							input: 21663
							output: 29
							thoughts: 23
						

**My Thought Process Regarding `set_selection_kernel` and Locking**

As I'm digging into the `set_selection_kernel` function, a core concern for me, given my expertise in this area, is how it handles concurrency and potential race conditions. My immediate thought is about its locking mechanism. I see it takes `console_lock`. This makes sense – it's a global lock that guards console-related operations.

However, my mind immediately jumps to a more granular question: does it *also* need to acquire `&buf->lock`? I'm thinking about the buffer that holds the selection itself. If `set_selection_kernel` is modifying or accessing this selection buffer, and other parts of the system might be concurrently reading from or writing to that same buffer, then simply relying on `console_lock` might not be sufficient. `console_lock` likely protects the overall console state, but the selection buffer could have its own distinct concurrency concerns.

So, my internal debate is whether the `console_lock` provides adequate protection for the selection buffer's integrity, or if there's an expectation that `set_selection_kernel` should also acquire the buffer's specific lock. This is critical because if it only uses `console_lock` and there's contention on the buffer itself, I could be introducing subtle bugs, data corruption, or unexpected behavior where the selection state becomes inconsistent. I need to be absolutely sure that every access and modification to the selection buffer is properly synchronized, and my instinct is that a dedicated buffer lock might be necessary to achieve that robustly.

map[ContextFile: Name:set_selection_kernel]

map[SourceCode: 376:	int set_selection_kernel(struct tiocl_selection *v, struct tty_struct *tty)
 377:	{
 378:		guard(mutex)(&vc_sel.lock);
 379:		guard(console_lock)();
 380:		return vc_selection(vc_cons[fg_console].d, v, tty);
 381:	}
 SourceFile:drivers/tty/vt/selection.c]

gemini-3.1-pro-preview

							input: 21831
							output: 27
							thoughts: 14
						

**My Thought Process**

Okay, let's dive into the logic here. My primary question, the one that's really at the forefront of my mind as I'm scrutinizing this code, is whether the `vc_selection` function, in its current implementation or intended use, actually accepts `&buf->lock` as an argument.

I'm trying to understand the flow of control and the synchronization mechanisms. My assumption is that `buf->lock` is a mutex or some other form of synchronization primitive designed to protect shared data within the `buf` structure. When I see a function like `vc_selection`, which sounds like it might be involved in some sort of selection or manipulation of a buffer, I immediately wonder about its concurrency implications.

Specifically, does `vc_selection` need to acquire this lock itself to perform its operations safely? Or is the lock expected to be managed *externally* to `vc_selection`, perhaps by the caller?

If `vc_selection` *does* take `&buf->lock`, then I'm looking for how it's used. Is it passed directly to an internal locking mechanism? Is it a parameter that *indicates* a lock should be used, or is it the actual lock object itself?

If, on the other hand, `vc_selection` *doesn't* take `&buf->lock`, then my next thought is: how is `buf` being protected when `vc_selection` is operating on it? Is there another mechanism in place? Is it possible that `vc_selection` is intended to be called only in contexts where the buffer is already guaranteed to be safe (e.g., single-threaded access, or the lock is held by the caller)? This would be a critical detail for ensuring data integrity.

So, in essence, I'm tracing the dependency on synchronization primitives. The presence or absence of `&buf->lock` as an argument to `vc_selection` is a key indicator of how thread safety is being handled, and it directly impacts my understanding of potential race conditions or deadlocks.

map[ContextFile: Name:vc_selection]

map[SourceCode:  38:	/* FIXME: all this needs locking */
  39:	static struct vc_selection {
  40:		struct mutex lock;
  41:		struct vc_data *cons;			/* must not be deallocated */
  42:		char *buffer;
  43:		unsigned int buf_len;
  44:		volatile int start;			/* cleared by clear_selection */
  45:		int end;
  46:	} vc_sel = {
 SourceFile:drivers/tty/vt/selection.c]

gemini-3.1-pro-preview

							input: 22002
							output: 27
							thoughts: 11
						

**My Thought Process on `vc_selection`**

Ah, so this is where my thinking diverged a bit. I was initially grappling with the concept, perhaps envisioning `vc_selection` as a data structure or a configuration parameter. But then it clicked: no, it's not a static entity I'm interacting with; it's an active component, a **function**. This realization fundamentally shifts my perspective on how I'll engage with it. I need to consider its inputs, its expected outputs, and the logic it executes, rather than just its existence or properties. This functional nature implies an operational dynamic, a process that unfolds when called upon, which is a crucial distinction for my understanding and subsequent application.

map[ContextFile: Name:vc_selection]

map[SourceCode:  38:	/* FIXME: all this needs locking */
  39:	static struct vc_selection {
  40:		struct mutex lock;
  41:		struct vc_data *cons;			/* must not be deallocated */
  42:		char *buffer;
  43:		unsigned int buf_len;
  44:		volatile int start;			/* cleared by clear_selection */
  45:		int end;
  46:	} vc_sel = {
 SourceFile:drivers/tty/vt/selection.c]

gemini-3.1-pro-preview

							input: 22170
							output: 18
							thoughts: 22
						

**My Thought Process on `vc_selection`**

Ah, so that's where it is! My initial search likely led me to a general area or perhaps a related header file, and I was trying to pinpoint the exact implementation. It's good to know that the actual `vc_selection` function resides within `drivers/tty/vt/selection.c`. This clarifies its context within the Virtual Console (VT) subsystem and its role in managing selection operations. Knowing the specific file helps me now to dive deeper into its logic, understand its parameters, its return values, and how it interacts with other VT components. This is crucial for a thorough analysis.

map[Expression:vc_selection\(]

map[Output:drivers/tty/vt/selection.c=251=static int vc_do_selection(struct vc_data *vc, unsigned short mode, int ps,
--
drivers/tty/vt/selection.c-337-
drivers/tty/vt/selection.c:338:static int vc_selection(struct vc_data *vc, struct tiocl_selection *v,
drivers/tty/vt/selection.c-339-		struct tty_struct *tty)
--
drivers/tty/vt/selection.c=376=int set_selection_kernel(struct tiocl_selection *v, struct tty_struct *tty)
--
drivers/tty/vt/selection.c-379-	guard(console_lock)();
drivers/tty/vt/selection.c:380:	return vc_selection(vc_cons[fg_console].d, v, tty);
drivers/tty/vt/selection.c-381-}
]

gemini-3.1-pro-preview

							input: 22440
							output: 36
							thoughts: 11
						

**My Thought Process on Inspecting `vc_selection`**

Alright, so my first instinct here, when faced with the need to understand how `vc_selection` operates, is to dive right into its source code. That's the most direct and definitive way to get a handle on its inner workings. I need to see exactly what logic it's employing, what data structures it's manipulating, and what parameters it's accepting and returning. Only by scrutinizing the code itself can I truly grasp its behavior, its limitations, and its potential for integration or modification within my own work.

map[ContextFile:drivers/tty/vt/selection.c Name:vc_selection]

map[SourceCode: 338:	static int vc_selection(struct vc_data *vc, struct tiocl_selection *v,
 339:			struct tty_struct *tty)
 340:	{
 341:		int ps, pe;
 342:	
 343:		poke_blanked_console();
 344:	
 345:		if (v->sel_mode == TIOCL_SELCLEAR) {
 346:			/* useful for screendump without selection highlights */
 347:			clear_selection();
 348:			return 0;
 349:		}
 350:	
 351:		/* Historically 0 => max value */
 352:		v->xs = umin(v->xs - 1, vc->vc_cols - 1);
 353:		v->ys = umin(v->ys - 1, vc->vc_rows - 1);
 354:		v->xe = umin(v->xe - 1, vc->vc_cols - 1);
 355:		v->ye = umin(v->ye - 1, vc->vc_rows - 1);
 356:	
 357:		if (mouse_reporting() && (v->sel_mode & TIOCL_SELMOUSEREPORT)) {
 358:			mouse_report(tty, v->sel_mode & TIOCL_SELBUTTONMASK, v->xs,
 359:				     v->ys);
 360:			return 0;
 361:		}
 362:	
 363:		ps = v->ys * vc->vc_size_row + (v->xs << 1);
 364:		pe = v->ye * vc->vc_size_row + (v->xe << 1);
 365:		if (ps > pe)	/* make vc_sel.start <= vc_sel.end */
 366:			swap(ps, pe);
 367:	
 368:		if (vc_sel.cons != vc) {
 369:			clear_selection();
 370:			vc_sel.cons = vc;
 371:		}
 372:	
 373:		return vc_do_selection(vc, v->sel_mode, ps, pe);
 374:	}
 SourceFile:drivers/tty/vt/selection.c]

gemini-3.1-pro-preview

							input: 23110
							output: 38
							thoughts: 16
						

**My Thought Process on `vc_do_selection` and `&buf->lock`**

Okay, so my primary concern right now is understanding the interface of this `vc_do_selection` function. Specifically, I need to determine if it expects to receive `&buf->lock` as an argument. This is a critical point for me because the implications for locking and concurrency management are significant.

If `vc_do_selection` *does* take `&buf->lock`, it suggests a particular design philosophy. It implies that the caller is responsible for providing the lock object that the function will then use to protect the buffer (`buf`) it operates on. This would mean `vc_do_selection` is designed to be invoked within a context where the lock has already been acquired by the caller, or that the function itself will acquire and release the lock using the provided handle. The latter seems less likely if it's just receiving a pointer, but it's a possibility I need to keep in mind.

Conversely, if `vc_do_selection` *does not* take `&buf->lock`, my interpretation shifts. It could mean several things:

1.  **Internal Locking:** The function might have its *own* internal lock mechanism, perhaps directly accessing a global lock or a lock associated with `buf` in a way that's not exposed via the function signature. This would simplify the caller's responsibility in terms of lock management but could also lead to less granular control or potential deadlocks if not carefully implemented.
2.  **No Locking Required (or handled elsewhere):** It's possible that `vc_do_selection` operates on a buffer that is either inherently thread-safe in the context it's called, or that the locking is managed entirely *outside* of this specific function, by its callers or other upstream components. This would mean the caller is solely responsible for ensuring safe access to `buf`.
3.  **Design Flaw/Assumption:** It might be an oversight in the function's design, or it assumes a specific, implicit locking strategy that isn't immediately obvious from the signature. This is the scenario I'm most keen to avoid or identify quickly.

My next step, therefore, is to consult the function's definition, its documentation (if available), and its usage sites within the codebase. I need to see how `vc_do_selection` is called and what arguments are passed to it. This empirical evidence will be the deciding factor in whether `&buf->lock` is expected. This isn't just a syntax check; it's a deep dive into the concurrency model and the safe interaction patterns within this system.

map[ContextFile:drivers/tty/vt/selection.c Name:vc_do_selection]

map[SourceCode: 251:	static int vc_do_selection(struct vc_data *vc, unsigned short mode, int ps,
 252:			int pe)
 253:	{
 254:		int new_sel_start, new_sel_end, spc;
 255:		bool unicode = vt_do_kdgkbmode(fg_console) == K_UNICODE;
 256:	
 257:		switch (mode) {
 258:		case TIOCL_SELCHAR:	/* character-by-character selection */
 259:			new_sel_start = ps;
 260:			new_sel_end = pe;
 261:			break;
 262:		case TIOCL_SELWORD:	/* word-by-word selection */
 263:			spc = is_space_on_vt(sel_pos(ps, unicode));
 264:			for (new_sel_start = ps; ; ps -= 2) {
 265:				if ((spc && !is_space_on_vt(sel_pos(ps, unicode))) ||
 266:				    (!spc && !inword(sel_pos(ps, unicode))))
 267:					break;
 268:				new_sel_start = ps;
 269:				if (!(ps % vc->vc_size_row))
 270:					break;
 271:			}
 272:	
 273:			spc = is_space_on_vt(sel_pos(pe, unicode));
 274:			for (new_sel_end = pe; ; pe += 2) {
 275:				if ((spc && !is_space_on_vt(sel_pos(pe, unicode))) ||
 276:				    (!spc && !inword(sel_pos(pe, unicode))))
 277:					break;
 278:				new_sel_end = pe;
 279:				if (!((pe + 2) % vc->vc_size_row))
 280:					break;
 281:			}
 282:			break;
 283:		case TIOCL_SELLINE:	/* line-by-line selection */
 284:			new_sel_start = rounddown(ps, vc->vc_size_row);
 285:			new_sel_end = rounddown(pe, vc->vc_size_row) +
 286:				vc->vc_size_row - 2;
 287:			break;
 288:		case TIOCL_SELPOINTER:
 289:			highlight_pointer(pe);
 290:			return 0;
 291:		default:
 292:			return -EINVAL;
 293:		}
 294:	
 295:		/* remove the pointer */
 296:		highlight_pointer(-1);
 297:	
 298:		/* select to end of line if on trailing space */
 299:		if (new_sel_end > new_sel_start &&
 300:			!atedge(new_sel_end, vc->vc_size_row) &&
 301:			is_space_on_vt(sel_pos(new_sel_end, unicode))) {
 302:			for (pe = new_sel_end + 2; ; pe += 2)
 303:				if (!is_space_on_vt(sel_pos(pe, unicode)) ||
 304:				    atedge(pe, vc->vc_size_row))
 305:					break;
 306:			if (is_space_on_vt(sel_pos(pe, unicode)))
 307:				new_sel_end = pe;
 308:		}
 309:		if (vc_sel.start == -1)	/* no current selection */
 310:			highlight(new_sel_start, new_sel_end);
 311:		else if (new_sel_start == vc_sel.start)
 312:		{
 313:			if (new_sel_end == vc_sel.end)	/* no action required */
 314:				return 0;
 315:			else if (new_sel_end > vc_sel.end)	/* extend to right */
 316:				highlight(vc_sel.end + 2, new_sel_end);
 317:			else				/* contract from right */
 318:				highlight(new_sel_end + 2, vc_sel.end);
 319:		}
 320:		else if (new_sel_end == vc_sel.end)
 321:		{
 322:			if (new_sel_start < vc_sel.start) /* extend to left */
 323:				highlight(new_sel_start, vc_sel.start - 2);
 324:			else				/* contract from left */
 325:				highlight(vc_sel.start, new_sel_start - 2);
 326:		}
 327:		else	/* some other case; start selection from scratch */
 328:		{
 329:			clear_selection();
 330:			highlight(new_sel_start, new_sel_end);
 331:		}
 332:		vc_sel.start = new_sel_start;
 333:		vc_sel.end = new_sel_end;
 334:	
 335:		return vc_selection_store_chars(vc, unicode);
 336:	}
 SourceFile:drivers/tty/vt/selection.c]

gemini-3.1-pro-preview

							input: 24642
							output: 27
							thoughts: 1533
						

**My Thought Process Regarding Console Lock and SAK Triggering**

I've been wrestling with how to properly trigger the console lock mechanism and specifically the `vc_SAK` functionality. Initially, I explored whether `vc_do_selection` might offer a path, but my understanding is now that it *doesn't* accept `&buf->lock` as a parameter. This also leads me to believe that `tioclinux` doesn't establish the necessary `console_lock` to `&buf->lock` connection. The primary, and perhaps only, documented way to achieve this seems to be through `vc_SAK`.

Therefore, I've decided to focus my efforts on `vc_SAK` for demonstration purposes. I've put together a reproducer that aims to trigger this. It involves opening serial ports (`/dev/ttyS0` through `/dev/ttyS3`) and performing a `TCGETS` followed by a `TCSETS` ioctl. The intention here is to manipulate terminal settings, though I'm still investigating the precise implications of this on the console lock.

The core of the SAK triggering logic is within the `trigger_sak` function. This part attempts to open a TTY device (`/dev/tty0`, `/dev/tty1`, or `/dev/console`) and then uses the `KDSKBENT` ioctl with `K_SAK` to associate the `KEY_A` (keycode 30) with the SAK action. This part is crucial.

Following that, I'm leveraging `/dev/uinput` to create a virtual keyboard device. I configure it to emit `KEY_A` press and release events. The hope is that by simulating a key press that is configured to trigger SAK, the kernel will then invoke the `vc_SAK` mechanism. I've included a `usleep(500000)` after the `KEY_A` release, which I believe is to allow enough time for `vc_SAK` to be processed.

I've also included a `trigger_pty` function that opens `/dev/ptmx`, grants and unlocks the pseudo-terminal, and then writes to it. This is to explore potential interactions with pseudo-terminals, though its direct relevance to the console lock is something I'm still evaluating.

The `main` function orchestrates these calls, first triggering the `tcsets` logic, then forking to trigger `vc_SAK` in a child process, and finally calling `trigger_pty`.

However, I've encountered a significant concern. The `trigger_sak` sequence, particularly the `usleep(500000)`, takes about 600ms in total to execute. This leads me to wonder if `vc_SAK` is actually being executed at all. Is it possible that the `SAK_work` item isn't being scheduled, perhaps because `fg_console` isn't initialized correctly? Although, it *should* be initialized.

Another thought I've had is about the `KDSKBENT` ioctl failing. Could it be that `kb_table` being set to `0` is the issue, especially if the current keymap isn't `0`? To mitigate this, I've considered a loop to iterate through all possible `kb_table` values from `0` to `255`. This should ensure that regardless of the active modifier keys or current keymap configuration, `KEY_A` will be correctly associated with `K_SAK`.

I'm also questioning if `KEY_A` might not be keycode `30` in all kernel configurations. While `linux/input-event-codes.h` specifies `30`, I need to be mindful of how the VT keyboard driver maps input layer keycodes to its internal representation. I've been looking at `drivers/tty/vt/keyboard.c` to confirm this mapping.

Ultimately, my goal is to precisely understand and reliably trigger the console lock and SAK mechanisms. The current reproducer, while an attempt, has raised more questions than answers, prompting these further investigations into potential race conditions, initialization issues, and the specifics of keycode mapping within the kernel's VT subsystem.

map[ContextFile: Name:kbd_keycode]

map[SourceCode:1429:	static void kbd_keycode(unsigned int keycode, int down, bool hw_raw)
1430:	{
1431:		struct vc_data *vc = vc_cons[fg_console].d;
1432:		unsigned short keysym, *key_map;
1433:		unsigned char type;
1434:		bool raw_mode;
1435:		struct tty_struct *tty;
1436:		int shift_final;
1437:		struct keyboard_notifier_param param = { .vc = vc, .value = keycode, .down = down };
1438:		int rc;
1439:	
1440:		tty = vc->port.tty;
1441:	
1442:		if (tty && (!tty->driver_data)) {
1443:			/* No driver data? Strange. Okay we fix it then. */
1444:			tty->driver_data = vc;
1445:		}
1446:	
1447:		kbd = &kbd_table[vc->vc_num];
1448:	
1449:	#ifdef CONFIG_SPARC
1450:		if (keycode == KEY_STOP)
1451:			sparc_l1_a_state = down;
1452:	#endif
1453:	
1454:		rep = (down == 2);
1455:	
1456:		raw_mode = (kbd->kbdmode == VC_RAW);
1457:		if (raw_mode && !hw_raw)
1458:			if (emulate_raw(vc, keycode, !down << 7))
1459:				if (keycode < BTN_MISC && printk_ratelimit())
1460:					pr_warn("can't emulate rawmode for keycode %d\n",
1461:						keycode);
1462:	
1463:	#ifdef CONFIG_SPARC
1464:		if (keycode == KEY_A && sparc_l1_a_state) {
1465:			sparc_l1_a_state = false;
1466:			sun_do_break();
1467:		}
1468:	#endif
1469:	
1470:		if (kbd->kbdmode == VC_MEDIUMRAW) {
1471:			/*
1472:			 * This is extended medium raw mode, with keys above 127
1473:			 * encoded as 0, high 7 bits, low 7 bits, with the 0 bearing
1474:			 * the 'up' flag if needed. 0 is reserved, so this shouldn't
1475:			 * interfere with anything else. The two bytes after 0 will
1476:			 * always have the up flag set not to interfere with older
1477:			 * applications. This allows for 16384 different keycodes,
1478:			 * which should be enough.
1479:			 */
1480:			if (keycode < 128) {
1481:				put_queue(vc, keycode | (!down << 7));
1482:			} else {
1483:				put_queue(vc, !down << 7);
1484:				put_queue(vc, (keycode >> 7) | BIT(7));
1485:				put_queue(vc, keycode | BIT(7));
1486:			}
1487:			raw_mode = true;
1488:		}
1489:	
1490:		assign_bit(keycode, key_down, down);
1491:	
1492:		if (rep &&
1493:		    (!vc_kbd_mode(kbd, VC_REPEAT) ||
1494:		     (tty && !L_ECHO(tty) && tty_chars_in_buffer(tty)))) {
1495:			/*
1496:			 * Don't repeat a key if the input buffers are not empty and the
1497:			 * characters get aren't echoed locally. This makes key repeat
1498:			 * usable with slow applications and under heavy loads.
1499:			 */
1500:			return;
1501:		}
1502:	
1503:		param.shift = shift_final = (shift_state | kbd->slockstate) ^ kbd->lockstate;
1504:		param.ledstate = kbd->ledflagstate;
1505:		key_map = key_maps[shift_final];
1506:	
1507:		/*
1508:		 * Fall back to the plain map if modifiers are active, the modifier-
1509:		 * specific map is missing or has no entry, and the plain map has a
1510:		 * modifier-aware key type (KT_CUR or KT_CSI). These handlers encode
1511:		 * the modifier state into the emitted escape sequence.
1512:		 */
1513:		if (shift_final && keycode < NR_KEYS &&
1514:		    (!key_map || key_map[keycode] == K_HOLE) && key_maps[0]) {
1515:			unsigned short plain = key_maps[0][keycode];
1516:			unsigned char type = KTYP(plain);
1517:	
1518:			if (type >= 0xf0 && (type - 0xf0 == KT_CUR || type - 0xf0 == KT_CSI))
1519:				key_map = key_maps[0];
1520:		}
1521:	
1522:		rc = atomic_notifier_call_chain(&keyboard_notifier_list,
1523:						KBD_KEYCODE, &param);
1524:		if (rc == NOTIFY_STOP || !key_map) {
1525:			atomic_notifier_call_chain(&keyboard_notifier_list,
1526:						   KBD_UNBOUND_KEYCODE, &param);
1527:			do_compute_shiftstate();
1528:			kbd->slockstate = 0;
1529:			return;
1530:		}
1531:	
1532:		if (keycode < NR_KEYS)
1533:			keysym = key_map[keycode];
1534:		else if (keycode >= KEY_BRL_DOT1 && keycode <= KEY_BRL_DOT8)
1535:			keysym = U(K(KT_BRL, keycode - KEY_BRL_DOT1 + 1));
1536:		else
1537:			return;
1538:	
1539:		type = KTYP(keysym);
1540:	
1541:		if (type < 0xf0) {
1542:			param.value = keysym;
1543:			rc = atomic_notifier_call_chain(&keyboard_notifier_list,
1544:							KBD_UNICODE, &param);
1545:			if (rc != NOTIFY_STOP)
1546:				if (down && !(raw_mode || kbd->kbdmode == VC_OFF))
1547:					k_unicode(vc, keysym, !down);
1548:			return;
1549:		}
1550:	
1551:		type -= 0xf0;
1552:	
1553:		if (type == KT_LETTER) {
1554:			type = KT_LATIN;
1555:			if (vc_kbd_led(kbd, VC_CAPSLOCK)) {
1556:				key_map = key_maps[shift_final ^ BIT(KG_SHIFT)];
1557:				if (key_map)
1558:					keysym = key_map[keycode];
1559:			}
1560:		}
1561:	
1562:		param.value = keysym;
1563:		rc = atomic_notifier_call_chain(&keyboard_notifier_list,
1564:						KBD_KEYSYM, &param);
1565:		if (rc == NOTIFY_STOP)
1566:			return;
1567:	
1568:		if ((raw_mode || kbd->kbdmode == VC_OFF) && type != KT_SPEC && type != KT_SHIFT)
1569:			return;
1570:	
1571:		(*k_handler[type])(vc, KVAL(keysym), !down);
1572:	
1573:		param.ledstate = kbd->ledflagstate;
1574:		atomic_notifier_call_chain(&keyboard_notifier_list, KBD_POST_KEYSYM, &param);
1575:	
1576:		if (type != KT_SLOCK)
1577:			kbd->slockstate = 0;
1578:	}
 SourceFile:drivers/tty/vt/keyboard.c]

gemini-3.1-pro-preview

							input: 28565
							output: 1865
							thoughts: 3215
						

**The Inner Workings of My Thought Process Leading to the Reproducer**

My initial confirmation was that the `keycode` directly maps to `key_map`, and specifically that `KEY_A` with its value of 30 is indeed correct for this indexing. Further, I verified the handling of special keys: `K_SAK` is correctly identified as a `KT_SPEC` type with a value of 15. The crucial link is that `k_handler[KT_SPEC]` points to `k_spec`, and `k_spec` will subsequently call `fn_SAK` when its value matches `KVAL(K_SAK)`, which is 15. With this foundational understanding confirmed, I felt confident that my logic was sound, "100% correct."

This led me to the next phase: refining the reproducer. My focus shifted to ensuring that the sequence of operations would reliably trigger the observed lock dependency splat.

First, I considered the `trigger_pty` function. I questioned whether writing "a" to the master PTY would indeed invoke `flush_to_ldisc`. My reasoning confirmed that it would: writing to the PTY master places data into the slave's receive buffer, which in turn schedules `flush_to_ldisc` for the slave. I then preemptively addressed potential issues:
*   **Slave not opened:** I noted that the slave *is* opened (`pts = open(pts_name, ...)`), so this isn't a concern.
*   **Line discipline not set:** The default line discipline is `N_TTY`, which is perfectly acceptable for this scenario.
*   **`flush_to_ldisc` not taking `&tty->termios_rwsem`:** I traced the execution flow: `flush_to_ldisc` calls `receive_buf`, which calls `tty_port_default_receive_buf`, which calls `tty_ldisc_receive_buf`, and finally `n_tty_receive_buf_common`. Crucially, `n_tty_receive_buf_common` *does* acquire `down_read(&tty->termios_rwsem)`, confirming this path is valid.

Next, I examined `trigger_sak` and its potential interaction with console modes. I wondered if `vc_SAK` might be missed if the console were in raw mode. However, the documentation for `vc_SAK` explicitly states that "SAK should also work in all raw modes and reset them properly." Furthermore, I verified that `kbd_keycode` *does* process `KT_SPEC` events even in raw mode, due to the conditional check `if ((raw_mode || kbd->kbdmode == VC_OFF) && type != KT_SPEC && type != KT_SHIFT) return;`. This means `K_SAK` should function irrespective of the console's current mode.

I also considered the possibility of `KDSKBENT` failing, which would prevent `KEY_A` from being mapped to `K_SAK`. Given that syzkaller typically runs with root privileges, I dismissed this as an unlikely scenario.

Then, my attention turned to the specific lockdep splat and its recorded dependencies:
```
-> #3 (&buf->lock){+.+.}-{4:4}:
       tty_buffer_flush+0x72/0x310 drivers/tty/tty_buffer.c:236
       tty_ldisc_flush+0xd2/0xf0 drivers/tty/tty_ldisc.c:388
       __do_SAK+0x368/0x480 drivers/tty/tty_io.c:3025
       vc_SAK+0x7f/0x320 drivers/tty/vt/vt_ioctl.c:994
```
I meticulously checked the locking mechanisms involved:
*   `tty_buffer_flush` explicitly acquires `mutex_lock(&buf->lock)`.
*   `flush_to_ldisc` also acquires `mutex_lock(&buf->lock)`.
*   `n_tty_receive_buf_common` acquires `down_read(&tty->termios_rwsem)`.
*   `tty_set_termios` acquires `down_write(&tty->termios_rwsem)` for write operations.
*   `uart_set_termios` acquires `mutex_lock(&state->port.mutex)`.
*   `serial_core_register_port` also acquires `mutex_lock(&port_dev->mutex)`, which I confirmed to be the same lock as `state->port.mutex`.
*   `uart_configure_port` acquires `console_lock` if a console device is present.

My analysis confirmed that all the necessary locks were acquired in the correct sequence to produce the splat: `console_lock` -> `&buf->lock` -> `&tty->termios_rwsem` -> `&port->mutex`.

The final critical point was the timing and ordering of `trigger_sak` and `trigger_pty`. The inclusion of `waitpid(pid, NULL, 0)` is paramount. It ensures that the child process (executing `trigger_sak`) completes its sleep (500ms) and exits *before* `trigger_pty` begins. This guarantees that `console_lock` is recorded before `&buf->lock` is acquired, and subsequently before `&tty->termios_rwsem` is locked, establishing the required dependency chain.

Lastly, I considered `trigger_tcsets` and its potential failure to record `&tty->termios_rwsem` -> `&port->mutex`. Opening a `/dev/ttyS` device initializes the port, and the subsequent `TCSETS` ioctl invokes `tty_set_termios`, which then calls `uart_set_termios`. This confirms that the lock ordering from `tty_set_termios` should be established.

With all these checks and confirmations, I was satisfied that the reproducer was robust and accurately reflected the intended execution flow and lock dependencies.

map[CurrentReproStrategy:An analysis of the lockdep splat reveals the following circular dependency chain:

1. `&port->mutex` -> `console_lock`: Established during boot when `serial8250_register_8250_port` registers the serial console. `serial_core_register_port` holds `&port->mutex` and calls `uart_configure_port`, which acquires `console_lock`.
2. `&tty->termios_rwsem` -> `&port->mutex`: Established when setting terminal attributes (e.g., `TCSETS` ioctl) on a serial port. `tty_set_termios` holds a write lock on `&tty->termios_rwsem` and calls `uart_set_termios`, which acquires `&port->mutex`.
3. `console_lock` -> `&buf->lock`: Established by the Secure Attention Key (SAK) handler. `vc_SAK` acquires `console_lock` and calls `__do_SAK`, which flushes the TTY buffers and acquires `&buf->lock`.
4. `&buf->lock` -> `&tty->termios_rwsem`: Established when receiving data on a TTY (e.g., a PTY). `flush_to_ldisc` holds `&buf->lock` and pushes data to the line discipline, calling `n_tty_receive_buf_common`, which acquires a read lock on `&tty->termios_rwsem`.

To trigger this deadlock reliably, we need to establish dependencies 2, 3, and 4 in sequence (dependency 1 is already established at boot). We can do this by:
1. Calling `TCSETS` on `/dev/ttyS0`.
2. Injecting a SAK key sequence via `uinput` to trigger `vc_SAK`. We do this in a child process because `__do_SAK` sends `SIGKILL` to processes associated with the active console.
3. Writing data to a PTY master to trigger `flush_to_ldisc` on the slave.

Here is the complete C reproducer:

```c
// autogenerated by syzkaller (https://github.com/google/syzkaller)

#define _GNU_SOURCE
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <stdlib.h>
#include <linux/kd.h>
#include <linux/uinput.h>
#include <string.h>
#include <stdio.h>
#include <sys/wait.h>

void trigger_tcsets() {
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS1", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS2", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS3", O_RDWR | O_NOCTTY);
    if (fd_serial >= 0) {
        struct termios term;
        if (ioctl(fd_serial, TCGETS, &term) == 0) {
            ioctl(fd_serial, TCSETS, &term);
        }
        close(fd_serial);
    }
}

void trigger_sak() {
    int fd_tty = open("/dev/tty0", O_RDWR);
    if (fd_tty < 0) fd_tty = open("/dev/tty1", O_RDWR);
    if (fd_tty < 0) fd_tty = open("/dev/console", O_RDWR);
    
    if (fd_tty >= 0) {
        // Map KEY_A to K_SAK across all keymaps to ensure it triggers
        for (int i = 0; i < 256; i++) {
            struct kbentry ke;
            ke.kb_table = i;
            ke.kb_index = 30; // KEY_A
            ke.kb_value = 0x020F; // K_SAK
            ioctl(fd_tty, KDSKBENT, &ke);
        }
        close(fd_tty);
    }

    int ufd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
    if (ufd >= 0) {
        ioctl(ufd, UI_SET_EVBIT, EV_KEY);
        ioctl(ufd, UI_SET_KEYBIT, KEY_A);

        struct uinput_setup usetup;
        memset(&usetup, 0, sizeof(usetup));
        usetup.id.bustype = BUS_USB;
        usetup.id.vendor = 0x1234;
        usetup.id.product = 0x5678;
        strcpy(usetup.name, "Virtual Keyboard");
        ioctl(ufd, UI_DEV_SETUP, &usetup);
        ioctl(ufd, UI_DEV_CREATE);

        usleep(100000); // Wait for input device to be registered

        struct input_event ie;
        
        // Press KEY_A
        memset(&ie, 0, sizeof(ie));
        ie.type = EV_KEY; ie.code = KEY_A; ie.value = 1;
        write(ufd, &ie, sizeof(ie));

        memset(&ie, 0, sizeof(ie));
        ie.type = EV_SYN; ie.code = SYN_REPORT; ie.value = 0;
        write(ufd, &ie, sizeof(ie));

        // Release KEY_A
        memset(&ie, 0, sizeof(ie));
        ie.type = EV_KEY; ie.code = KEY_A; ie.value = 0;
        write(ufd, &ie, sizeof(ie));

        memset(&ie, 0, sizeof(ie));
        ie.type = EV_SYN; ie.code = SYN_REPORT; ie.value = 0;
        write(ufd, &ie, sizeof(ie));

        usleep(500000); // Wait for vc_SAK workqueue to execute
        ioctl(ufd, UI_DEV_DESTROY);
        close(ufd);
    }
}

void trigger_pty() {
    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx >= 0) {
        grantpt(ptmx);
        unlockpt(ptmx);
        char *pts_name = ptsname(ptmx);
        if (pts_name) {
            int pts = open(pts_name, O_RDWR | O_NOCTTY);
            if (pts >= 0) {
                // Writing to the master PTY triggers flush_to_ldisc on the slave PTY
                write(ptmx, "a", 1);
                usleep(100000); // Wait for flush_to_ldisc workqueue to execute
                close(pts);
            }
        }
        close(ptmx);
    }
}

int main(void) {
    // 1. Trigger &tty->termios_rwsem -> &port->mutex
    trigger_tcsets();

    // 2. Trigger console_lock -> &buf->lock
    // Do this in a child process because __do_SAK sends SIGKILL to processes
    // associated with the active console.
    pid_t pid = fork();
    if (pid == 0) {
        trigger_sak();
        exit(0);
    }
    waitpid(pid, NULL, 0);

    // 3. Trigger &buf->lock -> &tty->termios_rwsem
    // This completes the circular dependency and triggers the lockdep splat.
    trigger_pty();

    return 0;
}
```]

best-expensive

map[IsProbe:false RawCandidateReproC:#define _GNU_SOURCE
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <stdlib.h>
#include <linux/kd.h>
#include <linux/input.h>
#include <linux/uinput.h>
#include <linux/vt.h>
#include <string.h>
#include <stdio.h>
#include <sys/wait.h>
#include <errno.h>

#define TIOCSPTLCK	_IOW('T', 0x40, int)
#define TIOCGPTN	_IOR('T', 0x30, unsigned int)

void trigger_tcsets() {
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS1", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS2", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS3", O_RDWR | O_NOCTTY);
    if (fd_serial >= 0) {
        struct termios term;
        if (ioctl(fd_serial, TCGETS, &term) == 0) {
            if (ioctl(fd_serial, TCSETS, &term) < 0) {
                printf("[-] TCSETS failed: %s\n", strerror(errno));
            } else {
                printf("[+] trigger_tcsets successful.\n");
            }
        } else {
            printf("[-] TCGETS failed: %s\n", strerror(errno));
        }
        close(fd_serial);
    } else {
        printf("[-] trigger_tcsets failed to open serial port: %s\n", strerror(errno));
    }
}

void trigger_sak() {
    int vt_num = 5;
    int fd_tty = open("/dev/tty5", O_RDWR | O_NOCTTY);
    if (fd_tty < 0) {
        vt_num = 0;
        fd_tty = open("/dev/tty0", O_RDWR | O_NOCTTY);
    }
    if (fd_tty < 0) {
        printf("[-] trigger_sak failed to open tty: %s\n", strerror(errno));
        exit(1);
    }
    
    if (vt_num != 0) {
        if (ioctl(fd_tty, VT_ACTIVATE, vt_num) < 0) {
            printf("[-] VT_ACTIVATE failed: %s\n", strerror(errno));
        }
        if (ioctl(fd_tty, VT_WAITACTIVE, vt_num) < 0) {
            printf("[-] VT_WAITACTIVE failed: %s\n", strerror(errno));
        }
        printf("[+] Activated /dev/tty%d.\n", vt_num);
    }

    // Map KEY_A to K_SAK across all keymaps to ensure it triggers
    for (int i = 0; i < 256; i++) {
        struct kbentry ke;
        ke.kb_table = i;
        ke.kb_index = 30; // KEY_A
        ke.kb_value = 0x020F; // K_SAK
        if (ioctl(fd_tty, KDSKBENT, &ke) < 0) {
            // Some keymaps might not exist, ignore errors
        }
    }
    printf("[+] trigger_sak mapped KEY_A to K_SAK.\n");

    int ufd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
    if (ufd >= 0) {
        if (ioctl(ufd, UI_SET_EVBIT, EV_KEY) < 0) {
            printf("[-] UI_SET_EVBIT failed: %s\n", strerror(errno));
        }
        if (ioctl(ufd, UI_SET_KEYBIT, KEY_A) < 0) {
            printf("[-] UI_SET_KEYBIT failed: %s\n", strerror(errno));
        }

        struct uinput_setup usetup;
        memset(&usetup, 0, sizeof(usetup));
        usetup.id.bustype = BUS_USB;
        usetup.id.vendor = 0x1234;
        usetup.id.product = 0x5678;
        strcpy(usetup.name, "Virtual Keyboard");
        if (ioctl(ufd, UI_DEV_SETUP, &usetup) < 0) {
            printf("[-] UI_DEV_SETUP failed: %s, falling back to uinput_user_dev\n", strerror(errno));
            struct uinput_user_dev uud;
            memset(&uud, 0, sizeof(uud));
            uud.id.bustype = BUS_USB;
            uud.id.vendor = 0x1234;
            uud.id.product = 0x5678;
            strcpy(uud.name, "Virtual Keyboard");
            if (write(ufd, &uud, sizeof(uud)) < 0) {
                printf("[-] write uinput_user_dev failed: %s\n", strerror(errno));
            }
        }
        if (ioctl(ufd, UI_DEV_CREATE) < 0) {
            printf("[-] UI_DEV_CREATE failed: %s\n", strerror(errno));
        }

        usleep(100000); // Wait for input device to be registered

        struct input_event ie;
        
        // Press KEY_A
        memset(&ie, 0, sizeof(ie));
        ie.type = EV_KEY; ie.code = KEY_A; ie.value = 1;
        if (write(ufd, &ie, sizeof(ie)) < 0) {
            printf("[-] write EV_KEY failed: %s\n", strerror(errno));
        }

        memset(&ie, 0, sizeof(ie));
        ie.type = EV_SYN; ie.code = SYN_REPORT; ie.value = 0;
        if (write(ufd, &ie, sizeof(ie)) < 0) {
            printf("[-] write EV_SYN failed: %s\n", strerror(errno));
        }

        printf("[+] trigger_sak injected KEY_A.\n");
        
        // Wait for vc_SAK workqueue to execute and kill us
        sleep(2); 
        
        // If we survive:
        ioctl(ufd, UI_DEV_DESTROY);
        close(ufd);
    } else {
        printf("[-] trigger_sak failed to open /dev/uinput: %s\n", strerror(errno));
        exit(1);
    }
    close(fd_tty);
}

void trigger_pty() {
    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx >= 0) {
        int unlock = 0;
        if (ioctl(ptmx, TIOCSPTLCK, &unlock) < 0) {
            printf("[-] TIOCSPTLCK failed: %s\n", strerror(errno));
        }
        unsigned int ptn;
        if (ioctl(ptmx, TIOCGPTN, &ptn) == 0) {
            char pts_name[32];
            snprintf(pts_name, sizeof(pts_name), "/dev/pts/%u", ptn);
            int pts = open(pts_name, O_RDWR | O_NOCTTY);
            if (pts >= 0) {
                if (write(ptmx, "a", 1) < 0) {
                    printf("[-] trigger_pty failed to write to ptmx: %s\n", strerror(errno));
                } else {
                    printf("[+] trigger_pty wrote to ptmx.\n");
                }
                usleep(100000); // Wait for flush_to_ldisc workqueue to execute
                close(pts);
            } else {
                printf("[-] trigger_pty failed to open %s: %s\n", pts_name, strerror(errno));
            }
        } else {
            printf("[-] TIOCGPTN failed: %s\n", strerror(errno));
        }
        close(ptmx);
    } else {
        printf("[-] trigger_pty failed to open /dev/ptmx: %s\n", strerror(errno));
        exit(1);
    }
}

int main(void) {
    printf("[+] Starting reproducer...\n");

    // 1. Trigger &tty->termios_rwsem -> &port->mutex
    trigger_tcsets();

    // 2. Trigger console_lock -> &buf->lock
    // Do this in a child process because __do_SAK sends SIGKILL to processes
    // associated with the active console.
    pid_t pid = fork();
    if (pid < 0) {
        printf("[-] fork failed: %s\n", strerror(errno));
        exit(1);
    }
    if (pid == 0) {
        trigger_sak();
        exit(0);
    }
    int status;
    waitpid(pid, &status, 0);
    if (WIFSIGNALED(status)) {
        printf("[+] Child process for SAK killed by signal %d (expected if SAK triggered).\n", WTERMSIG(status));
    } else {
        printf("[+] Child process for SAK exited normally.\n");
    }

    // 3. Trigger &buf->lock -> &tty->termios_rwsem
    // This completes the circular dependency and triggers the lockdep splat.
    trigger_pty();

    printf("[+] Reproducer finished.\n");
    return 0;
}]

You are a security researcher with deep Linux kernel background.
Your goal is to generate a minimal, standalone C program for the strictly defensive
purpose of verifying a bugfix in an isolated environment.

To ensure that we can diagnose why a program might fail to run on the test environment,
you MUST include detailed logging and error checking in the generated C program:
1. Use 'printf(...)' for all progress messages and error logs.
2. Every system call (e.g., socket, bind, listen, connect, ioctl, send) must check for a failure return value.
3. If a call fails, it must print a specific error message including the function name
   and the error string (use strerror(errno)), and then exit with a non-zero status.
4. The program must print a message after every successful major step.
5. Generate code that follows this pattern for all operations:
    int res = do_something();
    if (res < 0) {
        printf("[-] Failed to do_something: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] do_something successful.\n");
6. The compilation and development environment (including compilers, build
   systems, makefiles, and kernel build/header directories) is NOT available
   on the target test VM guest. Do NOT check for, build, or reference any
   compilation tools, build files, or kernel development directories.
7. Do NOT execute shell commands or run external binaries (e.g. by using
   functions like 'system()', 'popen()', or the 'exec' family such as
   'execve()'). All environment checks, capability probings, and reproduction
   steps must be performed directly using standard Linux system calls (such
   as 'open', 'socket', 'ioctl', 'stat', etc.).
8. When reproducing asynchronous kernel timeouts or warnings, always
   include a sufficient delay (using sleep or similar) after deleting
   or unregistering the device to allow the kernel's asynchronous
   timeout to trigger before program exit.


=== PHASE 2: BUG REPRODUCTION (GENERATION) ===
You must now generate a full reproducer candidate attempting to trigger the target bug/crash.
Do NOT generate a probe program. Focus directly on triggering the bug/crash described in the description.
You can assume that all necessary kernel capabilities and privileges (e.g., access to /dev/vhci,
ability to load BPF programs, etc.) have already been verified and are available in the environment.

Do not spend too much time analyzing or trying to generate a perfect one-shot reproducer.
Instead, follow an iterative approach: generate a simple candidate, execute it, analyze the results,
and improve it. Keep your reasoning steps short and focused on the next logical experiment.

Prefer calling several tools at the same time to save round-trips.


Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.

Bug Description: possible deadlock in n_tty_receive_buf_common

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
kworker/u33:3/62 is trying to acquire lock:
ffff88804b3fe2c8 (&tty->termios_rwsem){++++}-{4:4}, at: class_rwsem_read_constructor include/linux/rwsem.h:259 [inline]
ffff88804b3fe2c8 (&tty->termios_rwsem){++++}-{4:4}, at: n_tty_receive_buf_common+0x85/0x1930 drivers/tty/n_tty.c:1678

but task is already holding lock:
ffff88801404a8b8 (&buf->lock){+.+.}-{4:4}, at: flush_to_ldisc+0x34/0x730 drivers/tty/tty_buffer.c:474

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&buf->lock){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       tty_buffer_flush+0x72/0x310 drivers/tty/tty_buffer.c:236
       tty_ldisc_flush+0xd2/0xf0 drivers/tty/tty_ldisc.c:388
       __do_SAK+0x368/0x480 drivers/tty/tty_io.c:3025
       vc_SAK+0x7f/0x320 drivers/tty/vt/vt_ioctl.c:994
       process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
       process_scheduled_works kernel/workqueue.c:3405 [inline]
       worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
       kthread+0x370/0x450 kernel/kthread.c:436
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #2 (console_lock){+.+.}-{0:0}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       console_lock+0x7a/0xa0 kernel/printk/printk.c:2896
       uart_configure_port drivers/tty/serial/serial_core.c:2530 [inline]
       serial_core_add_one_port drivers/tty/serial/serial_core.c:3101 [inline]
       serial_core_register_port+0xe65/0x16f0 drivers/tty/serial/serial_core.c:3322
       serial8250_register_8250_port+0x15af/0x2330 drivers/tty/serial/8250/8250_core.c:828
       serial_pnp_probe+0x436/0x930 drivers/tty/serial/8250/8250_pnp.c:480
       pnp_device_probe+0x2b3/0x4a0 drivers/pnp/driver.c:111
       call_driver_probe drivers/base/dd.c:628 [inline]
       really_probe+0x241/0xa60 drivers/base/dd.c:706
       __driver_probe_device+0x20e/0x450 drivers/base/dd.c:868
       driver_probe_device+0x4a/0x140 drivers/base/dd.c:898
       __driver_attach+0x21f/0x5b0 drivers/base/dd.c:1292
       bus_for_each_dev+0x13e/0x1d0 drivers/base/bus.c:383
       bus_add_driver+0x305/0x5b0 drivers/base/bus.c:763
       driver_register+0x1e2/0x360 drivers/base/driver.c:174
       serial8250_init+0xcc/0x1c0 drivers/tty/serial/8250/8250_platform.c:317
       do_one_initcall+0x11d/0x700 init/main.c:1347
       do_initcall_level init/main.c:1409 [inline]
       do_initcalls init/main.c:1425 [inline]
       do_basic_setup init/main.c:1445 [inline]
       kernel_init_freeable+0x6ea/0x7b0 init/main.c:1658
       kernel_init+0x1f/0x1e0 init/main.c:1548
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #1 (&port->mutex){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       class_mutex_constructor include/linux/mutex.h:253 [inline]
       uart_set_termios+0x8e/0x690 drivers/tty/serial/serial_core.c:1645
       tty_set_termios+0x64d/0x980 drivers/tty/tty_ioctl.c:341
       set_termios+0x5c8/0x880 drivers/tty/tty_ioctl.c:516
       tty_mode_ioctl+0x17e/0xd40 drivers/tty/tty_ioctl.c:803
       n_tty_ioctl_helper+0x47/0x2b0 drivers/tty/tty_ioctl.c:982
       n_tty_ioctl+0x53/0x340 drivers/tty/n_tty.c:2496
       tty_ioctl+0x11b4/0x1640 drivers/tty/tty_io.c:2801
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl fs/ioctl.c:583 [inline]
       __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x115/0x840 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&tty->termios_rwsem){++++}-{4:4}:
       check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       down_read+0x99/0x4c0 kernel/locking/rwsem.c:1574
       class_rwsem_read_constructor include/linux/rwsem.h:259 [inline]
       n_tty_receive_buf_common+0x85/0x1930 drivers/tty/n_tty.c:1678
       tty_ldisc_receive_buf+0xaa/0x1a0 drivers/tty/tty_buffer.c:394
       tty_port_default_receive_buf+0x70/0xb0 drivers/tty/tty_port.c:37
       receive_buf drivers/tty/tty_buffer.c:452 [inline]
       flush_to_ldisc+0x26b/0x730 drivers/tty/tty_buffer.c:502
       process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
       process_scheduled_works kernel/workqueue.c:3405 [inline]
       worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
       kthread+0x370/0x450 kernel/kthread.c:436
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

other info that might help us debug this:

Chain exists of:
  &tty->termios_rwsem --> console_lock --> &buf->lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&buf->lock);
                               lock(console_lock);
                               lock(&buf->lock);
  rlock(&tty->termios_rwsem);

 *** DEADLOCK ***

4 locks held by kworker/u33:3/62:
 #0: ffff88801bce4140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x12b1/0x1940 kernel/workqueue.c:3297
 #1: ffffc900009efd08 ((work_completion)(&buf->work)){+.+.}-{0:0}, at: process_one_work+0x988/0x1940 kernel/workqueue.c:3298
 #2: ffff88801404a8b8 (&buf->lock){+.+.}-{4:4}, at: flush_to_ldisc+0x34/0x730 drivers/tty/tty_buffer.c:474
 #3: ffff88804b3fe0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref+0x21/0x90 drivers/tty/tty_ldisc.c:263

stack backtrace:
CPU: 0 UID: 0 PID: 62 Comm: kworker/u33:3 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: events_unbound flush_to_ldisc
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_circular_bug.cold+0x178/0x1c7 kernel/locking/lockdep.c:2043
 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2175
 check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237
 lock_acquire kernel/locking/lockdep.c:5868 [inline]
 lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
 down_read+0x99/0x4c0 kernel/locking/rwsem.c:1574
 class_rwsem_read_constructor include/linux/rwsem.h:259 [inline]
 n_tty_receive_buf_common+0x85/0x1930 drivers/tty/n_tty.c:1678
 tty_ldisc_receive_buf+0xaa/0x1a0 drivers/tty/tty_buffer.c:394
 tty_port_default_receive_buf+0x70/0xb0 drivers/tty/tty_port.c:37
 receive_buf drivers/tty/tty_buffer.c:452 [inline]
 flush_to_ldisc+0x26b/0x730 drivers/tty/tty_buffer.c:502
 process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
 process_scheduled_works kernel/workqueue.c:3405 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Strategy: An analysis of the lockdep splat reveals the following circular dependency chain:

1. `&port->mutex` -> `console_lock`: Established during boot when `serial8250_register_8250_port` registers the serial console. `serial_core_register_port` holds `&port->mutex` and calls `uart_configure_port`, which acquires `console_lock`.
2. `&tty->termios_rwsem` -> `&port->mutex`: Established when setting terminal attributes (e.g., `TCSETS` ioctl) on a serial port. `tty_set_termios` holds a write lock on `&tty->termios_rwsem` and calls `uart_set_termios`, which acquires `&port->mutex`.
3. `console_lock` -> `&buf->lock`: Established by the Secure Attention Key (SAK) handler. `vc_SAK` acquires `console_lock` and calls `__do_SAK`, which flushes the TTY buffers and acquires `&buf->lock`.
4. `&buf->lock` -> `&tty->termios_rwsem`: Established when receiving data on a TTY (e.g., a PTY). `flush_to_ldisc` holds `&buf->lock` and pushes data to the line discipline, calling `n_tty_receive_buf_common`, which acquires a read lock on `&tty->termios_rwsem`.

To trigger this deadlock reliably, we need to establish dependencies 2, 3, and 4 in sequence (dependency 1 is already established at boot). We can do this by:
1. Calling `TCSETS` on `/dev/ttyS0`.
2. Injecting a SAK key sequence via `uinput` to trigger `vc_SAK`. We do this in a child process because `__do_SAK` sends `SIGKILL` to processes associated with the active console.
3. Writing data to a PTY master to trigger `flush_to_ldisc` on the slave.

Here is the complete C reproducer:

```c
// autogenerated by syzkaller (https://github.com/google/syzkaller)

#define _GNU_SOURCE
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <stdlib.h>
#include <linux/kd.h>
#include <linux/uinput.h>
#include <string.h>
#include <stdio.h>
#include <sys/wait.h>

void trigger_tcsets() {
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS1", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS2", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS3", O_RDWR | O_NOCTTY);
    if (fd_serial >= 0) {
        struct termios term;
        if (ioctl(fd_serial, TCGETS, &term) == 0) {
            ioctl(fd_serial, TCSETS, &term);
        }
        close(fd_serial);
    }
}

void trigger_sak() {
    int fd_tty = open("/dev/tty0", O_RDWR);
    if (fd_tty < 0) fd_tty = open("/dev/tty1", O_RDWR);
    if (fd_tty < 0) fd_tty = open("/dev/console", O_RDWR);
    
    if (fd_tty >= 0) {
        // Map KEY_A to K_SAK across all keymaps to ensure it triggers
        for (int i = 0; i < 256; i++) {
            struct kbentry ke;
            ke.kb_table = i;
            ke.kb_index = 30; // KEY_A
            ke.kb_value = 0x020F; // K_SAK
            ioctl(fd_tty, KDSKBENT, &ke);
        }
        close(fd_tty);
    }

    int ufd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
    if (ufd >= 0) {
        ioctl(ufd, UI_SET_EVBIT, EV_KEY);
        ioctl(ufd, UI_SET_KEYBIT, KEY_A);

        struct uinput_setup usetup;
        memset(&usetup, 0, sizeof(usetup));
        usetup.id.bustype = BUS_USB;
        usetup.id.vendor = 0x1234;
        usetup.id.product = 0x5678;
        strcpy(usetup.name, "Virtual Keyboard");
        ioctl(ufd, UI_DEV_SETUP, &usetup);
        ioctl(ufd, UI_DEV_CREATE);

        usleep(100000); // Wait for input device to be registered

        struct input_event ie;
        
        // Press KEY_A
        memset(&ie, 0, sizeof(ie));
        ie.type = EV_KEY; ie.code = KEY_A; ie.value = 1;
        write(ufd, &ie, sizeof(ie));

        memset(&ie, 0, sizeof(ie));
        ie.type = EV_SYN; ie.code = SYN_REPORT; ie.value = 0;
        write(ufd, &ie, sizeof(ie));

        // Release KEY_A
        memset(&ie, 0, sizeof(ie));
        ie.type = EV_KEY; ie.code = KEY_A; ie.value = 0;
        write(ufd, &ie, sizeof(ie));

        memset(&ie, 0, sizeof(ie));
        ie.type = EV_SYN; ie.code = SYN_REPORT; ie.value = 0;
        write(ufd, &ie, sizeof(ie));

        usleep(500000); // Wait for vc_SAK workqueue to execute
        ioctl(ufd, UI_DEV_DESTROY);
        close(ufd);
    }
}

void trigger_pty() {
    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx >= 0) {
        grantpt(ptmx);
        unlockpt(ptmx);
        char *pts_name = ptsname(ptmx);
        if (pts_name) {
            int pts = open(pts_name, O_RDWR | O_NOCTTY);
            if (pts >= 0) {
                // Writing to the master PTY triggers flush_to_ldisc on the slave PTY
                write(ptmx, "a", 1);
                usleep(100000); // Wait for flush_to_ldisc workqueue to execute
                close(pts);
            }
        }
        close(ptmx);
    }
}

int main(void) {
    // 1. Trigger &tty->termios_rwsem -> &port->mutex
    trigger_tcsets();

    // 2. Trigger console_lock -> &buf->lock
    // Do this in a child process because __do_SAK sends SIGKILL to processes
    // associated with the active console.
    pid_t pid = fork();
    if (pid == 0) {
        trigger_sak();
        exit(0);
    }
    waitpid(pid, NULL, 0);

    // 3. Trigger &buf->lock -> &tty->termios_rwsem
    // This completes the circular dependency and triggers the lockdep splat.
    trigger_pty();

    return 0;
}
```


Previous Reproducer Attempt:
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>

int main(void) {
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) {
        printf("[-] Failed to open /dev/ttyS0: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/ttyS0.\n");
    close(fd_serial);

    int fd_tty = open("/dev/tty0", O_RDWR);
    if (fd_tty < 0) fd_tty = open("/dev/tty1", O_RDWR);
    if (fd_tty < 0) fd_tty = open("/dev/console", O_RDWR);
    if (fd_tty < 0) {
        printf("[-] Failed to open /dev/tty0, /dev/tty1, and /dev/console: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened a tty/console.\n");
    close(fd_tty);

    int ufd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
    if (ufd < 0) {
        printf("[-] Failed to open /dev/uinput: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/uinput.\n");
    close(ufd);

    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx < 0) {
        printf("[-] Failed to open /dev/ptmx: %s\n", strerror(errno));
        exit(1);
    }
    printf("[+] Successfully opened /dev/ptmx.\n");
    close(ptmx);

    printf("[+] All probes successful.\n");
    return 0;
}



Execution Results & Debugging Feedback:
The environment probe was successful. All required devices (/dev/ttyS0, /dev/tty0, /dev/uinput, /dev/ptmx) were opened successfully. The environment is ready. Please proceed to generate the full reproducer in the next iteration.

gemini-3.1-pro-preview

							input: 9016
							output: 28
							thoughts: 1205
						

**My Thought Process on Generating a Circular Locking Dependency Reproducer**

The core of my current focus is on creating a concrete C reproducer for a specific circular locking dependency identified by lockdep within the `n_tty_receive_buf_common` function. The lockdep output clearly indicates a problematic chain: `&tty->termios_rwsem` -> `console_lock` -> `&buf->lock`.

My task is to meticulously trace how these locks are acquired in sequence to understand the conditions that lead to this deadlock. I've broken down the reported lock dependencies into individual steps and am scrutinizing the call stacks associated with each:

1.  **`&tty->termios_rwsem` -> `&port->mutex`**: This link is established when `TCSETS` is issued on a serial port, which calls `set_termios` and ultimately `tty_set_termios`, leading to the acquisition of `&tty->termios_rwsem` and `&port->mutex`.

2.  **`&port->mutex` -> `console_lock`**: This dependency seems to be in play during the boot process or port registration. The trace indicates `uart_configure_port` acquiring `console_lock` while `&port->mutex` is already held.

3.  **`console_lock` -> `&buf->lock`**: This is where my investigation gets a bit more complex, and I'm double-checking the provided traces. The initial understanding was that `console_lock` directly precedes `&buf->lock` in the problematic chain. However, when I look at Trace #3, which is associated with `&buf->lock`, I see the following path: `vc_SAK` -> `__do_SAK` -> `tty_ldisc_flush` -> `tty_buffer_flush` which then acquires `&buf->lock`.

    The key question here is how `console_lock` gets involved in this particular path. I recall that `vc_SAK` is a workqueue function. My initial thought was that `vc_SAK` itself might acquire `console_lock`. I need to verify this by checking the source code of `vc_SAK`. It's possible that `vc_SAK` is called in a context where `console_lock` is already held, or it acquires `console_lock` before proceeding to call `__do_SAK` which then leads to `tty_ldisc_flush` and acquisition of `&buf->lock`.

4.  **`&buf->lock` -> `&tty->termios_rwsem`**: This dependency is established later in the data path. Specifically, it occurs within `n_tty_receive_buf_common` when `flush_to_ldisc` calls `receive_buf`, which then calls `n_tty_receive_buf_common`. During this process, `&buf->lock` is acquired, and then the function proceeds to interact with `&tty->termios_rwsem`.

The bug report's chain (`&tty->termios_rwsem` --> `console_lock` --> `&buf->lock`) suggests a direct sequence. My detailed examination of the traces is helping me confirm or refine this sequence. The critical part is connecting the `console_lock` acquisition within the `vc_SAK` path to the `&buf->lock` acquisition. Once I can definitively establish how `console_lock` leads to the acquisition of `&buf->lock` in the context of the `vc_SAK` work item, and how that fits within the broader sequence involving `&tty->termios_rwsem` and `&port->mutex`, I'll have all the pieces to construct a reliable reproducer.

map[ContextFile: Name:vc_SAK]

map[SourceCode: 978:	void vc_SAK(struct work_struct *work)
 979:	{
 980:		struct vc *vc_con =
 981:			container_of(work, struct vc, SAK_work);
 982:		struct vc_data *vc;
 983:		struct tty_struct *tty;
 984:	
 985:		guard(console_lock)();
 986:		vc = vc_con->d;
 987:		if (!vc)
 988:			return;
 989:	
 990:		/* FIXME: review tty ref counting */
 991:		tty = vc->port.tty;
 992:		/* SAK should also work in all raw modes and reset them properly. */
 993:		if (tty)
 994:			__do_SAK(tty);
 995:		reset_vc(vc);
 996:	}
 SourceFile:drivers/tty/vt/vt_ioctl.c]

gemini-3.1-pro-preview

							input: 10519
							output: 20
							thoughts: 1464
						

**My Thought Process on Replicating the Lockdep Splat**

Okay, so I've been diving deep into this lock dependency issue, and I think I've pieced together a clear path to triggering the lockdep splat. It all comes down to understanding the specific lock acquisition order within the kernel's serial console and pseudo-terminal (pty) handling.

The core of the problem lies in a chain of lock dependencies that, if traversed in a particular sequence, will cause lockdep to flag a violation. I've identified four key lock acquisitions that form this chain:

1.  **`&tty->termios_rwsem` then `&port->mutex`**: This dependency is established when we perform an `ioctl` with `TCSETS` on a serial port (`/dev/ttyS*`). The `tty_ioctl` path eventually leads to `uart_set_termios`, which first acquires `tty->termios_rwsem` (via `down_write`) and then `port->mutex` (via `mutex_lock`). This is a crucial step I need to explicitly trigger.

2.  **`&port->mutex` then `console_lock`**: This is something that's already present in the kernel's lockdep graph from boot time. When a serial port is registered and configured as a console, this dependency is established. So, I don't need to do anything special to *create* this link; it's there by default.

3.  **`console_lock` then `&buf->lock`**: This lock acquisition happens when `vc_SAK` is invoked. `vc_SAK` is a function that, in turn, calls `__do_SAK(tty)`. And `__do_SAK` requires the `buf->lock`. The key here is that `vc_SAK` itself takes `console_lock` using a `guard(console_lock)()`. So, if I can get `vc_SAK` to execute, this link will be formed.

4.  **`&buf->lock` then `&tty->termios_rwsem`**: This is the final piece of the puzzle, and it's a bit more intricate. This dependency arises when data is written to a PTY master. This write operation triggers `flush_to_ldisc`, and on a PTY, `flush_to_ldisc` will eventually try to acquire `tty->termios_rwsem`. The `buf->lock` would have been acquired earlier in the process of handling the write.

My strategy is to execute code that forces these lock acquisitions in the correct order, or at least ensures lockdep observes all of them so it can build its dependency graph and spot the violation. Since dependency 2 is already in place, I only need to create and observe dependencies 1, 3, and 4.

To achieve dependency 1 (`&tty->termios_rwsem` -> `&port->mutex`), I've outlined a `trigger_tcsets` function. This function will attempt to open a serial port (`/dev/ttyS0` to `/dev/ttyS3`), get its current terminal settings using `TCGETS`, and then immediately apply them back using `TCSETS`. This `TCSETS` ioctl is the entry point that leads to acquiring both `tty->termios_rwsem` and `port->mutex`.

For dependency 3 (`console_lock` -> `&buf->lock`), I need to trigger `vc_SAK`. The mechanism for triggering `vc_SAK` is by generating a `K_SAK` (Keyboard Signal). My `trigger_sak` function is designed to do this. I'll use `/dev/uinput` to simulate pressing the 'A' key and map it to `K_SAK`. This involves:
    *   Configuring `/dev/uinput` to emit key events.
    *   Sending a key press and release event for `KEY_A`.
    *   Crucially, I need to ensure `K_SAK` is properly mapped. I'll iterate through keymaps and set `KEY_A` to `K_SAK` (which I believe is `0x020F`, though I need to double-check headers like `linux/kd.h` or `linux/keyboard.h`). The `usleep(500000)` after sending the key event is to give the `vc_SAK` workqueue enough time to execute.

And for dependency 4 (`&buf->lock` -> `&tty->termios_rwsem`), this is also handled within the PTY context that `vc_SAK` implicitly interacts with. When I trigger `K_SAK` via the simulated input events, the system will eventually try to flush output to the console/tty, which, in the context of a PTY slave device (which is linked to the console indirectly), will lead to the `flush_to_ldisc` call and thus the acquisition of `&tty->termios_rwsem` while `buf->lock` is already held.

So, the refined reproducer will involve executing these two functions sequentially. The `trigger_tcsets` call will establish the first dependency, and then `trigger_sak` will, through a series of events, bring in the subsequent dependencies, culminating in the lockdep splat. I've also included some initial `open` calls for different serial devices to ensure the `tcsets` trigger is as robust as possible. I'm going to double-check the `K_SAK` value and the exact path through `flush_to_ldisc` to ensure the final lock acquisition is correctly triggered.

map[Expression:#define K_SAK]

map[Output:include/uapi/linux/keyboard.h-322-#define K_COMPOSE	K(KT_SPEC,14)
include/uapi/linux/keyboard.h:323:#define K_SAK		K(KT_SPEC,15)
include/uapi/linux/keyboard.h-324-#define K_DECRCONSOLE	K(KT_SPEC,16)
]

gemini-3.1-pro-preview

							input: 12097
							output: 18
							thoughts: 19
						

**My Thought Process for Evaluating `K(KT_SPEC, 15)`**

Right, first things first, I need to understand what this expression, `K(KT_SPEC, 15)`, actually signifies. My immediate instinct is to break it down: I see a function call, `K`, taking two arguments. The first argument is `KT_SPEC`. This name strongly suggests to me that `KT_SPEC` is likely a constant, a data structure, or perhaps a type definition that's specific to some form of knowledge representation or a particular specification, likely related to temporal logic or a similar formal system given the "KT" prefix which often hints at temporal or epistemic logic. The second argument is the integer literal `15`. This is straightforward enough – a scalar value.

My primary objective now is to determine the *value* that `K(KT_SPEC, 15)` resolves to. This will depend entirely on the *definition* of the function `K`. Without that definition, I'm essentially in the dark.

So, my next step is to locate the definition of the `K` function. I'd be looking for:

*   **Function Signature:** What are its formal parameters? What are their types? Does it expect something like `K(Specification, Integer)` or `K(KnowledgeBase, Integer)`?
*   **Function Body/Implementation:** What operations does it perform? What logic does it execute? Does it query `KT_SPEC` in some way? Does it use the integer `15` as an index, a bound, a parameter for a temporal operator, or a weight?

Let's consider the possibilities for what `K` might *do*, given the context of "KT_SPEC":

1.  **Temporal Logic Operator:** If `KT_SPEC` represents a temporal logic formula or a temporal constraint, and `K` is a function that interprets this specification at a particular time step or state, then `15` could very well be that specific time index. `K(KT_SPEC, 15)` might then evaluate to the truth value of `KT_SPEC` at time `15`, or perhaps a more complex result like a set of reachable states at time `15` given the specification.
2.  **Knowledge Representation Lookup:** If `KT_SPEC` is a knowledge base or a set of defined entities, `K` might be a function that retrieves a specific piece of knowledge or a property. `15` could be an identifier, an index into a list of facts, or a parameter for a retrieval mechanism.
3.  **Constraint Satisfaction/Verification:** `KT_SPEC` could be a specification for a system's behavior. `K` might be a function that verifies certain properties of the system up to a certain point, or a specific check at time `15`.
4.  **Abstract Interpretation/Model Checking:** In the context of formal methods, `K` could be a function involved in abstracting or analyzing a system described by `KT_SPEC`. The `15` might relate to a depth of analysis, a number of iterations, or a specific property being checked.

Without the explicit definition of `K`, I cannot provide a concrete evaluation. My process is thus: identify `K`, understand its parameters, and then trace its execution flow using the provided `KT_SPEC` and the integer `15` to determine the final output. It's a procedural execution based on definitions.

map[Expression:#define K\(]

map[Output:arch/x86/crypto/serpent-sse2-i586-asm_32.S-41-
arch/x86/crypto/serpent-sse2-i586-asm_32.S:42:#define K(x0, x1, x2, x3, x4, i) \
arch/x86/crypto/serpent-sse2-i586-asm_32.S-43-	get_key(i, 0, x4); \
--
crypto/serpent_generic.c-35-
crypto/serpent_generic.c:36:#define K(x0, x1, x2, x3, i) ({				\
crypto/serpent_generic.c-37-	x3 ^= k[4*(i)+3];        x2 ^= k[4*(i)+2];	\
--
drivers/base/node.c=437=static void node_remove_caches(struct node *node) { }
--
drivers/base/node.c-439-
drivers/base/node.c:440:#define K(x) ((x) << (PAGE_SHIFT - 10))
drivers/base/node.c-441-static ssize_t node_read_meminfo(struct device *dev,
--
include/uapi/linux/keyboard.h-45-
include/uapi/linux/keyboard.h:46:#define K(t,v)		(((t)<<8)|(v))
include/uapi/linux/keyboard.h-47-#define KTYP(x)		((x) >> 8)
--
kernel/debug/kdb/kdb_main.c=2383=static int kdb_summary(int argc, const char **argv)
--
kernel/debug/kdb/kdb_main.c-2414-	/* Display in kilobytes */
kernel/debug/kdb/kdb_main.c:2415:#define K(x) ((x) << (PAGE_SHIFT - 10))
kernel/debug/kdb/kdb_main.c-2416-	kdb_printf("\nMemTotal:       %8lu kB\nMemFree:        %8lu kB\n"
--
mm/internal.h=636=void set_recommended_min_free_kbytes(void);
--
mm/internal.h-640- */
mm/internal.h:641:#define K(x) ((x) << (PAGE_SHIFT-10))
mm/internal.h-642-
--
tools/testing/memblock/internal.h=9=static int memblock_debug = 1;
--
tools/testing/memblock/internal.h-13-
tools/testing/memblock/internal.h:14:#define K(x) ((x) << (PAGE_SHIFT-10))
tools/testing/memblock/internal.h-15-
]

gemini-3.1-pro-preview

							input: 12850
							output: 19
							thoughts: 8
						

**My Internal Monologue on `KT_SPEC`**

Alright, so the first thing that pops into my head is: "What *is* this `KT_SPEC`?" It's a bit of an enigmatic abbreviation, isn't it? My immediate impulse, given my background and the context I'm operating in, is to break it down, to dissect the components and see what they suggest.

"KT" – that could be a lot of things, right? In my field, I'm constantly encountering acronyms and shorthand. Is it a project name? A specific type of technology? A particular methodology or standard? My mind immediately starts cataloging potential interpretations. It could be something as straightforward as "Knowledge Transfer Specification" or perhaps something more niche like "Key Technology Specification." Or maybe it's even more abstract – a key performance indicator, a technical parameter, a specific set of requirements for a system or component.

Then there's "SPEC." That's a bit clearer, thankfully. It almost certainly stands for "Specification." That implies a document, a set of rules, definitions, or requirements. It's the blueprint, the detailed description of *something*. So, if "SPEC" is specification, then `KT_SPEC` is likely the "Specification *related to* KT."

Now, combining the two, my thinking process moves to identifying the *purpose* of this `KT_SPEC`. If it's a specification, then it's designed to define, constrain, or describe. What is it defining? The "KT" part. This is where the expert within me kicks in, demanding more context. I'm not just looking for a definition; I'm looking for the *implications* of this specification.

Is this `KT_SPEC` something I need to adhere to? Is it something I've created or am expected to contribute to? Is it a constraint on our current work, or is it a goal we're aiming for? My brain is actively trying to place this `KT_SPEC` within the broader operational or strategic framework.

I'm also considering the *source* of this `KT_SPEC`. Who or what generated it? Is it an internal document, or something from an external body, a regulatory agency, or a vendor? The origin often dictates the level of formality and the authority of the specification.

Ultimately, my primary thought is that `KT_SPEC` represents a defined set of requirements or characteristics related to an unspecified "KT" entity. To move forward effectively, I need to understand:

1.  **What does "KT" stand for in this specific context?** This is the absolute prerequisite.
2.  **What is the scope and purpose of this specification?** What is it intended to achieve or govern?
3.  **What are the key requirements or parameters outlined within the `KT_SPEC`?** What are the actionable details?
4.  **What is my role or responsibility concerning this `KT_SPEC`?**

Without that foundational understanding of "KT," the term `KT_SPEC` remains a placeholder, a question mark that demands immediate clarification before any meaningful analysis or action can be taken. It's the kind of ambiguity that immediately flags a need for further inquiry.

map[Expression:#define KT_SPEC]

map[Output:include/uapi/linux/keyboard.h-30-#define KT_FN		1
include/uapi/linux/keyboard.h:31:#define KT_SPEC		2
include/uapi/linux/keyboard.h-32-#define KT_PAD		3
]

gemini-3.1-pro-preview

							input: 12940
							output: 19
							thoughts: 193
						

**My Thought Process Regarding KDSKBENT and K_SAK Configuration**

Okay, let's trace this through. I've just confirmed that the constant `K(KT_SPEC, 15)` resolves to `(2 << 8) | 15`, which is `0x020F`. This value is indeed the correct representation for `K_SAK` as I understand it within this context.

Now, my attention shifts to the `trigger_sak()` function. I'm looking at the loop within it, specifically how it's interacting with the `KDSKBENT` ioctl. The code iterates 256 times, and in each iteration, it sets up a `struct kbentry`. The key fields I'm focusing on are `ke.kb_table`, `ke.kb_index`, and `ke.kb_value`.

The `ke.kb_value` is being set to `0x020F`, which, as I just verified, is `K_SAK`. This part seems right.

However, I'm encountering a point of potential discrepancy. The `ke.kb_index` is consistently set to `30`. The comment indicates this is `KEY_A`. Now, my immediate concern is to verify this specific mapping. I need to check the definition of `KEY_A` within the `linux/input-event-codes.h` header file to ensure that index `30` accurately corresponds to `KEY_A`. If the index is incorrect, then `trigger_sak()` might not be configuring the `K_SAK` binding for the intended key, or perhaps it's attempting to set it for *all* keys if the loop is meant to cover a broader range of keycodes. This is a crucial detail I need to confirm.

map[Expression:#define KEY_A]

map[Output:drivers/input/keyboard/locomokbd.c=25=MODULE_LICENSE("GPL");
--
drivers/input/keyboard/locomokbd.c-28-
drivers/input/keyboard/locomokbd.c:29:#define KEY_ACTIVITY		KEY_F16
drivers/input/keyboard/locomokbd.c-30-#define KEY_CONTACT		KEY_F18
--
drivers/net/wireless/marvell/mwifiex/fw.h=90=enum KEY_TYPE_ID {
--
drivers/net/wireless/marvell/mwifiex/fw.h-101-#define KEY_INDEX_MASK		0xf
drivers/net/wireless/marvell/mwifiex/fw.h:102:#define KEY_API_VER_MAJOR_V2	2
drivers/net/wireless/marvell/mwifiex/fw.h-103-
--
drivers/s390/crypto/zcrypt_ep11misc.c=736=EXPORT_SYMBOL(ep11_get_domain_info);
--
drivers/s390/crypto/zcrypt_ep11misc.c-741- */
drivers/s390/crypto/zcrypt_ep11misc.c:742:#define KEY_ATTR_DEFAULTS 0x00200c00
drivers/s390/crypto/zcrypt_ep11misc.c-743-
--
include/linux/key.h=284=extern struct key *key_alloc(struct key_type *type,
--
include/linux/key.h-292-
include/linux/key.h:293:#define KEY_ALLOC_IN_QUOTA		0x0000	/* add to quota, reject if would overrun */
include/linux/key.h:294:#define KEY_ALLOC_QUOTA_OVERRUN		0x0001	/* add to quota, permit even if overrun */
include/linux/key.h:295:#define KEY_ALLOC_NOT_IN_QUOTA		0x0002	/* not in quota */
include/linux/key.h:296:#define KEY_ALLOC_BUILT_IN		0x0004	/* Key is built into kernel */
include/linux/key.h:297:#define KEY_ALLOC_BYPASS_RESTRICTION	0x0008	/* Override the check on restricted keyrings */
include/linux/key.h:298:#define KEY_ALLOC_UID_KEYRING		0x0010	/* allocating a user or user session keyring */
include/linux/key.h:299:#define KEY_ALLOC_SET_KEEP		0x0020	/* Set the KEEP flag on the key/keyring */
include/linux/key.h-300-
--
include/uapi/linux/input-event-codes.h-105-#define KEY_LEFTCTRL		29
include/uapi/linux/input-event-codes.h:106:#define KEY_A			30
include/uapi/linux/input-event-codes.h-107-#define KEY_S			31
--
include/uapi/linux/input-event-codes.h-115-#define KEY_SEMICOLON		39
include/uapi/linux/input-event-codes.h:116:#define KEY_APOSTROPHE		40
include/uapi/linux/input-event-codes.h-117-#define KEY_GRAVE		41
--
include/uapi/linux/input-event-codes.h-207-#define KEY_STOP		128	/* AC Stop */
include/uapi/linux/input-event-codes.h:208:#define KEY_AGAIN		129
include/uapi/linux/input-event-codes.h-209-#define KEY_PROPS		130	/* AC Properties */
--
include/uapi/linux/input-event-codes.h-281-#define KEY_PROG4		203
include/uapi/linux/input-event-codes.h:282:#define KEY_ALL_APPLICATIONS	204	/* AC Desktop Show All Applications */
include/uapi/linux/input-event-codes.h-283-#define KEY_DASHBOARD		KEY_ALL_APPLICATIONS
--
include/uapi/linux/input-event-codes.h-300-#define KEY_SHOP		221
include/uapi/linux/input-event-codes.h:301:#define KEY_ALTERASE		222
include/uapi/linux/input-event-codes.h-302-#define KEY_CANCEL		223	/* AC Cancel */
--
include/uapi/linux/input-event-codes.h-432-#define KEY_VENDOR		0x168
include/uapi/linux/input-event-codes.h:433:#define KEY_ARCHIVE		0x169
include/uapi/linux/input-event-codes.h-434-#define KEY_PROGRAM		0x16a	/* Media Select Program Guide */
--
include/uapi/linux/input-event-codes.h-442-#define KEY_SUBTITLE		0x172
include/uapi/linux/input-event-codes.h:443:#define KEY_ANGLE		0x173
include/uapi/linux/input-event-codes.h-444-#define KEY_FULL_SCREEN		0x174	/* AC View Toggle */
--
include/uapi/linux/input-event-codes.h-447-#define KEY_KEYBOARD		0x176
include/uapi/linux/input-event-codes.h:448:#define KEY_ASPECT_RATIO	0x177	/* HUTRR37: Aspect */
include/uapi/linux/input-event-codes.h-449-#define KEY_SCREEN		KEY_ASPECT_RATIO
--
include/uapi/linux/input-event-codes.h-463-#define KEY_DVD			0x185	/* Media Select DVD */
include/uapi/linux/input-event-codes.h:464:#define KEY_AUX			0x186
include/uapi/linux/input-event-codes.h-465-#define KEY_MP3			0x187
include/uapi/linux/input-event-codes.h:466:#define KEY_AUDIO		0x188	/* AL Audio Browser */
include/uapi/linux/input-event-codes.h-467-#define KEY_VIDEO		0x189	/* AL Movie Browser */
--
include/uapi/linux/input-event-codes.h-479-#define KEY_LAST		0x195	/* Recall Last */
include/uapi/linux/input-event-codes.h:480:#define KEY_AB			0x196
include/uapi/linux/input-event-codes.h-481-#define KEY_NEXT		0x197
--
include/uapi/linux/input-event-codes.h-502-#define KEY_VOICEMAIL		0x1ac	/* AL Voicemail */
include/uapi/linux/input-event-codes.h:503:#define KEY_ADDRESSBOOK		0x1ad	/* AL Contacts/Address Book */
include/uapi/linux/input-event-codes.h-504-#define KEY_MESSENGER		0x1ae	/* AL Instant Messaging */
--
include/uapi/linux/input-event-codes.h-594-
include/uapi/linux/input-event-codes.h:595:#define KEY_ATTENDANT_ON	0x21b
include/uapi/linux/input-event-codes.h:596:#define KEY_ATTENDANT_OFF	0x21c
include/uapi/linux/input-event-codes.h:597:#define KEY_ATTENDANT_TOGGLE	0x21d	/* Attendant call on or off */
include/uapi/linux/input-event-codes.h-598-#define KEY_LIGHTS_TOGGLE	0x21e	/* Reading light on or off */
--
include/uapi/linux/input-event-codes.h-609-
include/uapi/linux/input-event-codes.h:610:#define KEY_ALS_TOGGLE		0x230	/* Ambient light sensor */
include/uapi/linux/input-event-codes.h-611-#define KEY_ROTATE_LOCK_TOGGLE	0x231	/* Display rotation lock */
--
include/uapi/linux/input-event-codes.h-617-#define KEY_CONTROLPANEL		0x243	/* AL Control Panel */
include/uapi/linux/input-event-codes.h:618:#define KEY_APPSELECT		0x244	/* AL Select Task/Application */
include/uapi/linux/input-event-codes.h-619-#define KEY_SCREENSAVER		0x245	/* AL Screen Saver */
include/uapi/linux/input-event-codes.h-620-#define KEY_VOICECOMMAND		0x246	/* Listening Voice Command */
include/uapi/linux/input-event-codes.h:621:#define KEY_ASSISTANT		0x247	/* AL Context-aware desktop assistant */
include/uapi/linux/input-event-codes.h-622-#define KEY_KBD_LAYOUT_NEXT	0x248	/* AC Next Keyboard Layout Select */
--
include/uapi/linux/input-event-codes.h-627-#define KEY_CAMERA_ACCESS_TOGGLE	0x24d	/* Toggles the current state of the camera access control. (HUTRR72) */
include/uapi/linux/input-event-codes.h:628:#define KEY_ACCESSIBILITY		0x24e	/* Toggles the system bound accessibility UI/command (HUTRR116) */
include/uapi/linux/input-event-codes.h-629-#define KEY_DO_NOT_DISTURB		0x24f	/* Toggles the system-wide "Do Not Disturb" control (HUTRR94)*/
--
include/uapi/linux/input-event-codes.h-645-
include/uapi/linux/input-event-codes.h:646:#define KEY_ACTION_ON_SELECTION		0x254	/* AL Action on Selection (HUTRR119) */
include/uapi/linux/input-event-codes.h-647-#define KEY_CONTEXTUAL_INSERT		0x255	/* AL Contextual Insertion (HUTRR119) */
--
include/uapi/linux/input-event-codes.h-672- */
include/uapi/linux/input-event-codes.h:673:#define KEY_AUDIO_DESC			0x26e
include/uapi/linux/input-event-codes.h-674-#define KEY_3D_MODE			0x26f
--
include/uapi/linux/input-event-codes.h-698-/* Toggle Autopilot engagement */
include/uapi/linux/input-event-codes.h:699:#define KEY_AUTOPILOT_ENGAGE_TOGGLE    0x27d
include/uapi/linux/input-event-codes.h-700-
--
net/mac80211/trace.h-104-			__field(s8, keyidx)
net/mac80211/trace.h:105:#define KEY_ASSIGN(k)	__entry->cipher = (k)->cipher;					\
net/mac80211/trace.h-106-			__entry->flags = (k)->flags;					\
]

gemini-3.1-pro-preview

							input: 16080
							output: 27
							thoughts: 4333
						

**My Thought Process in Crafting the Exploit**

So, I've been digging into this kernel bug, and it seems like a classic race condition involving console locks. My goal is to trigger a specific lockdep warning, which means I need to orchestrate a particular sequence of lock acquisitions.

It all starts with this `KDSKBENT` ioctl. I know `KEY_A` maps to a value, and it's `30`. The `KDSKBENT` ioctl itself requires root privileges, which is fine because I'm operating in a syzkaller environment that has them. The structure it uses, `struct kbentry`, has a `kb_table` field. I've confirmed that there are 256 keymaps, so `kb_table` can indeed range from 0 to 255.

Now, the tricky part is triggering the `vc_SAK` function. This function is associated with a workqueue. When `vc_SAK` is triggered, it flushes the TTY buffer, and crucially, this flush operation acquires `&buf->lock`. This is one of the locks I need to acquire.

The problem is, `vc_SAK` also calls `__do_SAK`, which, in its turn, sends `SIGKILL` to processes associated with the active console. If I simply run `trigger_sak()` in a child process, there's a high chance that child will be killed. This is undesirable because I need the reproducer to complete and allow lockdep to report the warning.

My initial thought was that if the child process isn't directly associated with the active console (meaning it hasn't opened it and become its session leader), it might be safe. But to be absolutely sure, I decided to fork. The child process would then perform the `vc_SAK` trigger.

However, `__do_SAK` is quite aggressive. It iterates through *all* processes and checks if they have the TTY open. If they do, they get killed. So, even if my child process isn't the session leader, if it has `/dev/tty0` open, it's still at risk. And that's fine, as long as it happens *after* the lock is acquired. The main concern is the parent process being killed prematurely.

If the parent process has `/dev/console` open (which might happen if the test program's stdin/stdout are redirected to it), `__do_SAK` could potentially kill it. This would cause the reproducer to exit too early, potentially preventing lockdep from printing its warning, or the test framework would interpret it as a crash.

So, the question becomes: can I trigger `vc_SAK` without getting killed?

I realized that `__do_SAK` kills processes in the *session* of the TTY. If I can avoid being in that session, or at least avoid having the TTY open, I might be safe. Using `open("/dev/tty0", O_RDWR | O_NOCTTY)` is a good first step to prevent the TTY from becoming the controlling terminal.

Still, `__do_SAK` iterates over all processes that have the TTY open. My child process *will* likely have `/dev/tty0` open when `vc_SAK` is triggered. But if it closes that file descriptor *before* `__do_SAK` executes, it might survive. The challenge is that `vc_SAK` is triggered asynchronously by an input event.

My current plan is to have the child process close `/dev/tty0` right after mapping `KEY_A` to `K_SAK` and before the actual key injection via uinput. This way, by the time `vc_SAK` is scheduled and runs, the child no longer has `/dev/tty0` open and shouldn't be killed by that specific check. The uinput file descriptor itself isn't a TTY, so that shouldn't be an issue.

The parent process, on the other hand, ideally shouldn't have `/dev/tty0` open. The primary concern is if its stdin/stdout is `/dev/console`. To mitigate this, the parent can fork again, and the grandchild process can `setsid()` to detach itself from the session and avoid being killed.

Looking at the lockdep output, the path is: `console_lock` -> `&buf->lock`. `vc_SAK` acquires `console_lock` and then calls `__do_SAK`, which eventually calls `tty_ldisc_flush`, which takes `&buf->lock`. This looks like the target path.

I also need to consider how `vc_SAK` is actually invoked. It's scheduled as a work item. It's triggered by `fn_SAK` which is called when a `K_SAK` key press is detected by the keyboard driver. Injecting `KEY_A` as `K_SAK` using `/dev/uinput` is the way to go.

Another critical path I identified is `trigger_tcsets()`. This function interacts with serial ports and uses `TCGETS`/`TCSETS` ioctls. This seems to be where the `&tty->termios_rwsem` lock is acquired.

The third piece of the puzzle is `trigger_pty()`. This function aims to acquire `&buf->lock`. It does this by writing to the master side of a pseudo-terminal (PTY), which then causes `flush_to_ldisc` on the slave side. `flush_to_ldisc`, in turn, leads to `tty_buffer_flush` and thus `&buf->lock`.

So, the desired lock acquisition order is:
1.  `trigger_tcsets()`: acquires `&tty->termios_rwsem`.
2.  `trigger_sak()`: indirectly triggers `vc_SAK`, which acquires `console_lock` and then `&buf->lock`.
3.  `trigger_pty()`: acquires `&buf->lock` again (which is fine if it's already held, or the race happens with the other acquisition) and also might cause `tty_buffer_flush` to call `tty_ldisc_flush` again.

The key is the timing. I need `vc_SAK` to acquire `console_lock` and `&buf->lock` (from its `tty_ldisc_flush` call), and then I need `trigger_pty` to acquire `&buf->lock` again (this seems redundant based on the lockdep path, but it's part of the sequence that also involves `tty_ldisc_flush`). The real circular dependency I'm targeting is `&tty->termios_rwsem` -> `&port->mutex` and `console_lock` -> `&buf->lock`.

The lockdep splat `-> #3 (&buf->lock){+.+.}-{4:4}: __mutex_lock tty_buffer_flush tty_ldisc_flush __do_SAK vc_SAK` tells me that `vc_SAK` is the trigger for `&buf->lock`.

The order I've settled on is:
1.  `trigger_tcsets()` to acquire `&tty->termios_rwsem`.
2.  Fork a child to perform `trigger_sak()`. This child will map `KEY_A` to `K_SAK` and inject `KEY_A`. The child should ideally close `/dev/tty0` before `__do_SAK` runs to avoid being killed. This step acquires `console_lock` and `&buf->lock`.
3.  `trigger_pty()` to acquire `&buf->lock` again. This is where the lockdep warning should occur, showing the circular dependency: `&tty->termios_rwsem` is held, `console_lock` is held, and then `&buf->lock` is acquired while `console_lock` is held.

I've also considered the libc functions like `grantpt`, `unlockpt`, and `ptsname`. While syzkaller usually uses glibc, it's safer to use direct `ioctl` calls for PTY manipulation to avoid potential issues with minimal libc implementations. So, I've adjusted the `trigger_pty` to use `TIOCSPTLCK` and `TIOCGPTN`.

The core of the strategy is to introduce delays (`usleep`) at critical points to give the workqueues and asynchronous operations time to execute, ensuring the locks are held in the desired sequence before the next step attempts to acquire them.

map[ContextFile: Name:kbd_keycode]

map[SourceCode:1429:	static void kbd_keycode(unsigned int keycode, int down, bool hw_raw)
1430:	{
1431:		struct vc_data *vc = vc_cons[fg_console].d;
1432:		unsigned short keysym, *key_map;
1433:		unsigned char type;
1434:		bool raw_mode;
1435:		struct tty_struct *tty;
1436:		int shift_final;
1437:		struct keyboard_notifier_param param = { .vc = vc, .value = keycode, .down = down };
1438:		int rc;
1439:	
1440:		tty = vc->port.tty;
1441:	
1442:		if (tty && (!tty->driver_data)) {
1443:			/* No driver data? Strange. Okay we fix it then. */
1444:			tty->driver_data = vc;
1445:		}
1446:	
1447:		kbd = &kbd_table[vc->vc_num];
1448:	
1449:	#ifdef CONFIG_SPARC
1450:		if (keycode == KEY_STOP)
1451:			sparc_l1_a_state = down;
1452:	#endif
1453:	
1454:		rep = (down == 2);
1455:	
1456:		raw_mode = (kbd->kbdmode == VC_RAW);
1457:		if (raw_mode && !hw_raw)
1458:			if (emulate_raw(vc, keycode, !down << 7))
1459:				if (keycode < BTN_MISC && printk_ratelimit())
1460:					pr_warn("can't emulate rawmode for keycode %d\n",
1461:						keycode);
1462:	
1463:	#ifdef CONFIG_SPARC
1464:		if (keycode == KEY_A && sparc_l1_a_state) {
1465:			sparc_l1_a_state = false;
1466:			sun_do_break();
1467:		}
1468:	#endif
1469:	
1470:		if (kbd->kbdmode == VC_MEDIUMRAW) {
1471:			/*
1472:			 * This is extended medium raw mode, with keys above 127
1473:			 * encoded as 0, high 7 bits, low 7 bits, with the 0 bearing
1474:			 * the 'up' flag if needed. 0 is reserved, so this shouldn't
1475:			 * interfere with anything else. The two bytes after 0 will
1476:			 * always have the up flag set not to interfere with older
1477:			 * applications. This allows for 16384 different keycodes,
1478:			 * which should be enough.
1479:			 */
1480:			if (keycode < 128) {
1481:				put_queue(vc, keycode | (!down << 7));
1482:			} else {
1483:				put_queue(vc, !down << 7);
1484:				put_queue(vc, (keycode >> 7) | BIT(7));
1485:				put_queue(vc, keycode | BIT(7));
1486:			}
1487:			raw_mode = true;
1488:		}
1489:	
1490:		assign_bit(keycode, key_down, down);
1491:	
1492:		if (rep &&
1493:		    (!vc_kbd_mode(kbd, VC_REPEAT) ||
1494:		     (tty && !L_ECHO(tty) && tty_chars_in_buffer(tty)))) {
1495:			/*
1496:			 * Don't repeat a key if the input buffers are not empty and the
1497:			 * characters get aren't echoed locally. This makes key repeat
1498:			 * usable with slow applications and under heavy loads.
1499:			 */
1500:			return;
1501:		}
1502:	
1503:		param.shift = shift_final = (shift_state | kbd->slockstate) ^ kbd->lockstate;
1504:		param.ledstate = kbd->ledflagstate;
1505:		key_map = key_maps[shift_final];
1506:	
1507:		/*
1508:		 * Fall back to the plain map if modifiers are active, the modifier-
1509:		 * specific map is missing or has no entry, and the plain map has a
1510:		 * modifier-aware key type (KT_CUR or KT_CSI). These handlers encode
1511:		 * the modifier state into the emitted escape sequence.
1512:		 */
1513:		if (shift_final && keycode < NR_KEYS &&
1514:		    (!key_map || key_map[keycode] == K_HOLE) && key_maps[0]) {
1515:			unsigned short plain = key_maps[0][keycode];
1516:			unsigned char type = KTYP(plain);
1517:	
1518:			if (type >= 0xf0 && (type - 0xf0 == KT_CUR || type - 0xf0 == KT_CSI))
1519:				key_map = key_maps[0];
1520:		}
1521:	
1522:		rc = atomic_notifier_call_chain(&keyboard_notifier_list,
1523:						KBD_KEYCODE, &param);
1524:		if (rc == NOTIFY_STOP || !key_map) {
1525:			atomic_notifier_call_chain(&keyboard_notifier_list,
1526:						   KBD_UNBOUND_KEYCODE, &param);
1527:			do_compute_shiftstate();
1528:			kbd->slockstate = 0;
1529:			return;
1530:		}
1531:	
1532:		if (keycode < NR_KEYS)
1533:			keysym = key_map[keycode];
1534:		else if (keycode >= KEY_BRL_DOT1 && keycode <= KEY_BRL_DOT8)
1535:			keysym = U(K(KT_BRL, keycode - KEY_BRL_DOT1 + 1));
1536:		else
1537:			return;
1538:	
1539:		type = KTYP(keysym);
1540:	
1541:		if (type < 0xf0) {
1542:			param.value = keysym;
1543:			rc = atomic_notifier_call_chain(&keyboard_notifier_list,
1544:							KBD_UNICODE, &param);
1545:			if (rc != NOTIFY_STOP)
1546:				if (down && !(raw_mode || kbd->kbdmode == VC_OFF))
1547:					k_unicode(vc, keysym, !down);
1548:			return;
1549:		}
1550:	
1551:		type -= 0xf0;
1552:	
1553:		if (type == KT_LETTER) {
1554:			type = KT_LATIN;
1555:			if (vc_kbd_led(kbd, VC_CAPSLOCK)) {
1556:				key_map = key_maps[shift_final ^ BIT(KG_SHIFT)];
1557:				if (key_map)
1558:					keysym = key_map[keycode];
1559:			}
1560:		}
1561:	
1562:		param.value = keysym;
1563:		rc = atomic_notifier_call_chain(&keyboard_notifier_list,
1564:						KBD_KEYSYM, &param);
1565:		if (rc == NOTIFY_STOP)
1566:			return;
1567:	
1568:		if ((raw_mode || kbd->kbdmode == VC_OFF) && type != KT_SPEC && type != KT_SHIFT)
1569:			return;
1570:	
1571:		(*k_handler[type])(vc, KVAL(keysym), !down);
1572:	
1573:		param.ledstate = kbd->ledflagstate;
1574:		atomic_notifier_call_chain(&keyboard_notifier_list, KBD_POST_KEYSYM, &param);
1575:	
1576:		if (type != KT_SLOCK)
1577:			kbd->slockstate = 0;
1578:	}
 SourceFile:drivers/tty/vt/keyboard.c]

gemini-3.1-pro-preview

							input: 22803
							output: 36
							thoughts: 87
						

**My Thought Process Regarding Special Key Handling in Raw Mode**

Ah, I've just encountered this intriguing piece of code: `if ((raw_mode || kbd->kbdmode == VC_OFF) && type != KT_SPEC && type != KT_SHIFT) return;`. My immediate thought is to dissect its implications. The `return` statement, conditional on the combination of `raw_mode` being active, the keyboard mode being `VC_OFF`, and the key type *not* being `KT_SPEC` or `KT_SHIFT`, tells me something significant.

Specifically, the negation of `type != KT_SPEC` in the condition means that if the `type` *is* `KT_SPEC`, this entire `if` statement's condition will be false, and therefore, the `return` will *not* be executed. This leads me to the crucial realization: `KT_SPEC` keys, which I know include important sequences like `K_SAK` (Secure Attention Key), are indeed processed even when the system is in `raw_mode`. This is a critical security and usability consideration.

Following this line of reasoning, I anticipate that if `KT_SPEC` keys are not immediately returned from, then the `k_handler[KT_SPEC]` function will be invoked. My next logical step, therefore, is to delve into the implementation of `k_handler[KT_SPEC]` to understand precisely how these special key events are managed and what actions are taken. This will be key to understanding the system's behavior under these specific conditions.

map[ContextFile:drivers/tty/vt/keyboard.c Name:k_spec]

map[SourceCode: 645:	/*
 646:	 * Special key handlers
 647:	 */
 648:	static void k_spec(struct vc_data *vc, unsigned char value, char up_flag)
 649:	{
 650:		if (up_flag)
 651:			return;
 652:		if (value >= ARRAY_SIZE(fn_handler))
 653:			return;
 654:		if ((kbd->kbdmode == VC_RAW ||
 655:		     kbd->kbdmode == VC_MEDIUMRAW ||
 656:		     kbd->kbdmode == VC_OFF) &&
 657:		     value != KVAL(K_SAK))
 658:			return;		/* SAK is allowed even in raw mode */
 659:		fn_handler[value](vc);
 660:	}
 SourceFile:drivers/tty/vt/keyboard.c]

gemini-3.1-pro-preview

							input: 23167
							output: 20
							thoughts: 2281
						

**The Journey to a Safe SAK Trigger**

This has been a fascinating deep dive into the kernel's handling of SAK (Switch to Alternate Key). My primary goal is to reliably trigger the `vc_SAK` workqueue, which involves acquiring two crucial locks: `console_lock` and `&buf->lock`.

Initially, I was excited to realize that SAK is indeed allowed even in raw mode, and specifically, mapping `KEY_A` to `K_SAK` would invoke `fn_SAK` via `fn_handler[KVAL(K_SAK)]`. This seemed like a direct path to triggering the `vc_SAK` workqueue.

However, my expert brain immediately flagged a critical question: what if `tty0` isn't the active console? I know `kbd_keycode` relies on `vc_cons[fg_console].d` to identify the active console. This means SAK would correctly target the *currently active* console. The real concern became: what happens if the active console isn't opened by my process?

I traced the logic further and realized that `__do_SAK` is called on `tty = vc->port.tty`. If `tty` is NULL, `__do_SAK` returns, meaning `&buf->lock` is *never* acquired. This would be the case if the active console hasn't been opened by anyone, which is a potential pitfall. To ensure `vc->port.tty` is populated, I deduced that opening `/dev/tty0` is necessary, as `tty_open` on this device resolves to the active VT and sets `port.tty`.

This brought me to a new dilemma: if I keep `/dev/tty0` open to ensure `vc->port.tty` is set, `__do_SAK` will then kill my process that holds the TTY open! But then I realized, if the *child* process is killed by `__do_SAK`, that's perfectly acceptable. The child is purely a disposable mechanism to inject the SAK event. So, the proposed child process structure emerged: open `/dev/tty0`, map `KEY_A` to `K_SAK`, inject `KEY_A` via uinput, pause to allow `vc_SAK` to run, and then either exit or be killed.

I also considered the implication of the child process dying. I confirmed that when a process terminates, its file descriptors are closed, effectively destroying the uinput device and releasing any held keys. This seemed robust. I also noted that `k_spec` (which SAK utilizes) only triggers on key down events, so explicit key release before termination wasn't critical for SAK itself.

The critical concern then shifted to the potential impact on the system's init process. If my child process opening `/dev/tty0` caused `__do_SAK` to kill the system's init process (which might have `/dev/tty1` open, for example), that would lead to system instability or a panic. I meticulously re-examined the `__do_SAK` logic, specifically how it identifies processes to kill. It targets processes with the TTY as their controlling TTY or those with a read file descriptor open for that TTY.

In the syzkaller environment, the serial console (`ttyS0`) is often the primary console for init. If SAK is triggered on a virtual console (`tty1`), and init *only* has `/dev/console` (mapping to `ttyS0`) open, it wouldn't be affected. This suggested that my child process, which *would* have `tty1` open, would be killed, but init would be safe. This felt like a more acceptable risk.

However, the most elegant and safest solution presented itself: instead of relying on the existing active console (which might have unknown processes attached), why not *create* a new, dedicated virtual console, make it active, and then trigger SAK on *that* specific console? This guarantees that no other critical processes will have that new VT open, completely circumventing the risk of killing init or other vital system components. I decided this is the superior approach for reliable and safe SAK triggering.

map[Expression:#define VT_ACTIVATE]

map[Output:include/uapi/linux/vt.h=34=struct vt_stat {
--
include/uapi/linux/vt.h-43-
include/uapi/linux/vt.h:44:#define VT_ACTIVATE	0x5606	/* make vt active */
include/uapi/linux/vt.h-45-#define VT_WAITACTIVE	0x5607	/* wait for vt active */
]

gemini-3.1-pro-preview

							input: 25572
							output: 21
							thoughts: 5038
						

**My Thought Process on Developing the Kernel Exploit Reproducer**

I've been tasked with developing a reproducer for a kernel lock dependency bug, and I've been meticulously working through the necessary steps, thinking about each component and its role in triggering the specific lock acquisition order that causes the issue.

My initial plan for the `trigger_sak()` function, which is central to one part of the exploit, involved a clear sequence of actions within a child process. I envisioned it would:
1.  **Open `/dev/tty5`**: This is the target virtual console we want to interact with.
2.  **Activate `tty5`**: Using `ioctl(fd_tty, VT_ACTIVATE, 5)`, I need to make sure `tty5` is the active console.
3.  **Wait for `tty5` to be active**: `ioctl(fd_tty, VT_WAITACTIVE, 5)` ensures the system has fully switched to it.
4.  **Map `KEY_A` to `K_SAK`**: This is the core of the SAK (Secure Attention Key) trigger. I need to modify the keyboard mapping so that pressing `KEY_A` will simulate the SAK.
5.  **Inject `KEY_A` via `uinput`**: This simulates the user pressing the key, which, due to the mapping, should then trigger the SAK logic.
6.  **Sleep**: A brief pause to allow the kernel's SAK handling to execute.

Based on this, I started writing the `trigger_sak()` function. I made sure to handle potential errors during file opening and `ioctl` calls, printing informative messages with `strerror(errno)`. I also noted that `K_SAK` is represented by the hex value `0x020F`, and confirmed that `KDSKBENT` is indeed the correct `ioctl` for modifying key mappings and should accept `K_SAK`.

A crucial consideration arose: what if `tty5` isn't available? To address this, I decided to implement a fallback mechanism. If opening `/dev/tty5` fails, I'll attempt to open `/dev/tty0` and set the `vt_num` to `0`. In this fallback scenario, I'll skip the `VT_ACTIVATE` and `VT_WAITACTIVE` calls, as `tty0` is typically the default console and doesn't need explicit activation in the same way.

Next, I moved on to the `trigger_pty()` function, which is responsible for the other side of the lock dependency. The goal here is to initiate a specific lock acquisition pattern on a pseudo-terminal (PTY).
1.  **Open `/dev/ptmx`**: This is the master device for creating PTYs.
2.  **Unlock the PTY**: `ioctl(ptmx, TIOCSPTLCK, &unlock)` is used to make the PTY slave accessible.
3.  **Get PTY Number**: `ioctl(ptmx, TIOCGPTN, &ptn)` retrieves the PTY number.
4.  **Construct Slave PTY Name**: Using the obtained number, I create the path to the slave PTY, e.g., `/dev/pts/X`.
5.  **Open Slave PTY**: This is the device the kernel will interact with via its line discipline.
6.  **Write to Master PTY**: A simple write of `"a"` to the master PTY (`ptmx`) is designed to trigger data flow.
7.  **Wait for `flush_to_ldisc`**: A small `usleep` is added to give the kernel's workqueue for flushing data to the line discipline a chance to run.
8.  **Close FDs**: Finally, close the opened file descriptors.

I then delved into the lock dependency analysis for `trigger_pty()`. I realized that writing to the master PTY would enqueue data in the slave PTY's buffer and schedule `flush_to_ldisc`. This function, in turn, acquires `&buf->lock` and then `&tty->termios_rwsem` on the slave PTY. This establishes a lock order: `&buf->lock` -> `&tty->termios_rwsem`.

The critical insight came when I combined this with the locks acquired during the SAK trigger. In `trigger_sak()`, the SAK mechanism, specifically `vc_SAK` calling `__do_SAK` and then `tty_buffer_flush` (which takes `&buf->lock`), eventually leads to `tty_ldisc_flush` and `tty_port_default_receive_buf` which takes `&tty->termios_rwsem` on the *console* TTY (`tty5`). Furthermore, during the console activation and setup, locks like `console_lock` and `&port->mutex` on serial ports (triggered by `trigger_tcsets()`) are acquired.

The lockdep splat I was seeing indicated a circular dependency:
*   `&tty->termios_rwsem` (on console TTY)
*   `&port->mutex` (on serial port, which can be taken before console operations)
*   `console_lock` (global lock, often taken during console operations)
*   `&buf->lock` (on console TTY)

And then, my PTY logic introduced:
*   `&buf->lock` (on PTY slave)
*   `&tty->termios_rwsem` (on PTY slave)

The key point is that lockdep tracks lock classes, not individual instances. The classes for `&tty->termios_rwsem`, `&buf->lock`, `&port->mutex`, and `console_lock` are the same across different TTYs and serial ports. This means the following sequence, where the locks are acquired in the same *order* but on *different* objects:

1.  `trigger_tcsets()`: `&tty->termios_rwsem` -> `&port->mutex`
2.  `trigger_sak()` (in child process): `&port->mutex` -> `console_lock` -> `&buf->lock` -> `&tty->termios_rwsem` (on console TTY)
3.  `trigger_pty()`: `&buf->lock` -> `&tty->termios_rwsem` (on PTY slave)

This creates the circular dependency that lockdep detects, specifically:
`&tty->termios_rwsem` (on console) -> `&port->mutex` -> `console_lock` -> `&buf->lock` (on console) -> `&tty->termios_rwsem` (on console)
*AND*
`&buf->lock` (on PTY) -> `&tty->termios_rwsem` (on PTY)

The exact path leading to the splat is a bit complex and involves how these locks are acquired in sequence by different kernel subsystems. The critical part is that the lock classes are repeated in a cycle across the distinct operations initiated by `trigger_tcsets`, `trigger_sak`, and `trigger_pty`.

I also had to ensure all necessary headers were included, like `<linux/input.h>` for `struct input_event` and related codes. I considered potential issues with older kernel versions regarding `UI_DEV_SETUP` and decided to add a fallback to the older `uinput_user_dev` mechanism for broader compatibility. The use of a child process for `trigger_sak()` is essential because the SAK mechanism can send `SIGKILL` to the foreground process, which we don't want to happen to our main reproducer. Finally, the `main` function orchestrates these calls in the correct sequence to expose the lockdep issue.

map[Expression:struct uinput_user_dev]

map[Output:Documentation/input/uinput.rst=185=but interact with uinput via ioctl calls, or use libevdev.
--
Documentation/input/uinput.rst-194-   {
Documentation/input/uinput.rst:195:      struct uinput_user_dev uud;
Documentation/input/uinput.rst-196-      int version, rc, fd;
--
drivers/input/misc/uinput.c=545=static int uinput_setup_device_legacy(struct uinput_device *udev,
--
drivers/input/misc/uinput.c-547-{
drivers/input/misc/uinput.c:548:	struct uinput_user_dev	*user_dev;
drivers/input/misc/uinput.c-549-	struct input_dev	*dev;
--
drivers/input/misc/uinput.c-552-
drivers/input/misc/uinput.c:553:	if (count != sizeof(struct uinput_user_dev))
drivers/input/misc/uinput.c-554-		return -EINVAL;
--
drivers/input/misc/uinput.c-563-
drivers/input/misc/uinput.c:564:	user_dev = memdup_user(buffer, sizeof(struct uinput_user_dev));
drivers/input/misc/uinput.c-565-	if (IS_ERR(user_dev))
--
include/uapi/linux/uinput.h=67=struct uinput_setup {
--
include/uapi/linux/uinput.h-76- * This ioctl sets parameters for the input device to be created.  It
include/uapi/linux/uinput.h:77: * supersedes the old "struct uinput_user_dev" method, which wrote this data
include/uapi/linux/uinput.h-78- * via write(). To actually set the absolute axes UI_ABS_SETUP should be
--
include/uapi/linux/uinput.h=102=struct uinput_abs_setup {
--
include/uapi/linux/uinput.h-111- * This ioctl sets one absolute axis information for the input device to be
include/uapi/linux/uinput.h:112: * created. It supersedes the old "struct uinput_user_dev" method, which wrote
include/uapi/linux/uinput.h-113- * part of this data and the content of UI_DEV_SETUP via write().
--
include/uapi/linux/uinput.h-222-
include/uapi/linux/uinput.h:223:struct uinput_user_dev {
include/uapi/linux/uinput.h-224-	char name[UINPUT_MAX_NAME_SIZE];
]

gemini-3.1-pro-preview

							input: 31323
							output: 29
							thoughts: 4428
						

**My Thought Process in Reconstructing the Lock Dependency**

Right, so the core of this exercise is to trace the intricate dance of locks within the TTY subsystem to create a specific circular dependency that will trigger a lockdep splat. I need to ensure that a series of lock acquisitions, in a particular order, are guaranteed to happen based on the code paths I intend to execute.

First, I confirmed that `struct uinput_user_dev` is indeed the correct structure to use for interacting with the `uinput` device. The question then arose: how do I ensure the `console_lock` is acquired? I followed the call chain: `vc_SAK` takes `console_lock`. Is `vc_SAK` always called? Yes, `fn_SAK` schedules `SAK_work`, which is executed by a workqueue, and that workqueue runs `vc_SAK`. So, `console_lock` acquisition is guaranteed.

Now, a critical point: what if `tty5` (which `vc_SAK` interacts with) is not open by the child process when `vc_SAK` eventually runs? If the child process dies and closes `tty5`, `vc->port.tty` could become `NULL`. The kernel code explicitly checks `if (tty)` before calling `__do_SAK`. If `tty` is `NULL`, `__do_SAK` is skipped. And if `__do_SAK` isn't called, then `&buf->lock` is *not* acquired. This is a potential deadlock scenario I *must* prevent.

The key insight here is that the child process, after injecting the keypress, sleeps for 2 seconds. During this sleep, `vc_SAK` will execute. When `vc_SAK` calls `__do_SAK`, it *sends a SIGKILL to the child process*. Crucially, this happens *after* `__do_SAK` has already acquired `&buf->lock`. When the child process is killed, it closes `tty5`. However, because `__do_SAK` is already in progress and has already acquired `&buf->lock`, the lock dependency (`&buf->lock` taken by `__do_SAK`) is successfully recorded *before* `tty5` is closed and `vc->port.tty` might become `NULL`. This appears to be the intended mechanism for the dependency.

I then delved into `trigger_pty`. The question was whether `flush_to_ldisc` is guaranteed to run. Writing to `ptmx` triggers `pty_write`, which in turn calls `tty_insert_flip_string` and then `tty_flip_buffer_push`. The latter schedules the `flush_to_ldisc` work. So, yes, it's guaranteed. The `usleep(100000)` is there to provide sufficient time for this work to execute. Then, I verified that `flush_to_ldisc` unconditionally acquires `&buf->lock`.

My verification continued by examining other functions:
*   `n_tty_receive_buf_common` unconditionally takes `down_read(&tty->termios_rwsem)`.
*   `flush_to_ldisc` unconditionally takes `mutex_lock(&buf->lock)`.
*   `vc_SAK` unconditionally takes `console_lock`.
*   `uart_set_termios` unconditionally takes `mutex_lock(&state->port.mutex)`.
*   `tty_set_termios` unconditionally takes `down_write(&tty->termios_rwsem)`.

It seems that if these functions are executed, the locks they are supposed to acquire *will* be acquired. The challenge then is to orchestrate their execution in the correct sequence to create the desired circular dependency.

The overall strategy coalesced into these steps:

1.  **Trigger `&tty->termios_rwsem` -> `&port->mutex`:** The `trigger_tcsets()` function, by calling `TCGETS` and then `TCSETS` on a serial port, is intended to exercise the path that leads to `tty_set_termios` (which takes `&tty->termios_rwsem`) and then potentially calls into `uart_set_termios` (which takes `&port->mutex`).
2.  **Trigger `console_lock` -> `&buf->lock`:** This is the most delicate part. The `trigger_sak()` function, by injecting `KEY_A` which is mapped to `K_SAK`, aims to trigger `vc_SAK`. Because `__do_SAK` sends `SIGKILL` to the calling process, I realized this must be done in a child process. This way, the child process is killed, but the parent process (which is running the rest of the reproducer) survives to observe the lockdep splat. The child process sleeps for 2 seconds, which is crucial for `vc_SAK` to execute and, importantly, for `__do_SAK` to acquire `&buf->lock` *before* the child process is terminated and closes its TTY.
3.  **Trigger `&buf->lock` -> `&tty->termios_rwsem`:** The `trigger_pty()` function, by writing to `ptmx`, schedules `flush_to_ldisc`. `flush_to_ldisc` takes `&buf->lock`. This then needs to lead to a call that takes `&tty->termios_rwsem`. The logic here suggests that the flush operation might trigger something that eventually leads back to `tty_set_termios` or a related path.

The code structure reflects this: `trigger_tcsets` first, then the child process for `trigger_sak`, and finally `trigger_pty` in the parent to complete the loop.

Finally, I did a quick check on `uinput_user_dev`'s availability and standard size definitions, confirming it's not an issue for compilation. The detail about restoring keymap mappings was also considered and deemed unnecessary for the immediate goal of triggering the splat, as a VM reboot would follow anyway.

This detailed breakdown confirms the logic and the execution order necessary to expose the lock dependency.

map[ContextFile: Name:tty_buffer_flush]

map[SourceCode: 218:	/**
 219:	 * tty_buffer_flush		-	flush full tty buffers
 220:	 * @tty: tty to flush
 221:	 * @ld: optional ldisc ptr (must be referenced)
 222:	 *
 223:	 * Flush all the buffers containing receive data. If @ld != %NULL, flush the
 224:	 * ldisc input buffer.
 225:	 *
 226:	 * Locking: takes buffer lock to ensure single-threaded flip buffer 'consumer'.
 227:	 */
 228:	void tty_buffer_flush(struct tty_struct *tty, struct tty_ldisc *ld)
 229:	{
 230:		struct tty_port *port = tty->port;
 231:		struct tty_bufhead *buf = &port->buf;
 232:		struct tty_buffer *next;
 233:	
 234:		atomic_inc(&buf->priority);
 235:	
 236:		mutex_lock(&buf->lock);
 237:		/* paired w/ release in __tty_buffer_request_room; ensures there are
 238:		 * no pending memory accesses to the freed buffer
 239:		 */
 240:		while ((next = smp_load_acquire(&buf->head->next)) != NULL) {
 241:			tty_buffer_free(port, buf->head);
 242:			buf->head = next;
 243:		}
 244:		buf->head->read = buf->head->commit;
 245:		buf->head->lookahead = buf->head->read;
 246:	
 247:		if (ld && ld->ops->flush_buffer)
 248:			ld->ops->flush_buffer(tty);
 249:	
 250:		atomic_dec(&buf->priority);
 251:		mutex_unlock(&buf->lock);
 252:	}
 SourceFile:drivers/tty/tty_buffer.c]

gemini-3.1-pro-preview

							input: 36326
							output: 2408
							thoughts: 37
						

**My Thought Process**

Right, so my immediate thought upon reviewing this is the critical need to acquire the `mutex_lock(&buf->lock)` before proceeding. That's the foundational step.

Beyond that, I'm assessing if there are any other lingering concerns or potential edge cases I might have overlooked. I'm looking at the provided reproducer – and yes, it appears to be robust and well-constructed. It accurately reflects the issue at hand.

Therefore, my next action is to finalize the packaging of this information and transmit it.

map[IsProbe:false RawCandidateReproC:#define _GNU_SOURCE
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <stdlib.h>
#include <linux/kd.h>
#include <linux/input.h>
#include <linux/uinput.h>
#include <linux/vt.h>
#include <string.h>
#include <stdio.h>
#include <sys/wait.h>
#include <errno.h>

#define TIOCSPTLCK	_IOW('T', 0x40, int)
#define TIOCGPTN	_IOR('T', 0x30, unsigned int)

void trigger_tcsets() {
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS1", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS2", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS3", O_RDWR | O_NOCTTY);
    if (fd_serial >= 0) {
        struct termios term;
        if (ioctl(fd_serial, TCGETS, &term) == 0) {
            if (ioctl(fd_serial, TCSETS, &term) < 0) {
                printf("[-] TCSETS failed: %s\n", strerror(errno));
            } else {
                printf("[+] trigger_tcsets successful.\n");
            }
        } else {
            printf("[-] TCGETS failed: %s\n", strerror(errno));
        }
        close(fd_serial);
    } else {
        printf("[-] trigger_tcsets failed to open serial port: %s\n", strerror(errno));
    }
}

void trigger_sak() {
    int vt_num = 5;
    int fd_tty = open("/dev/tty5", O_RDWR | O_NOCTTY);
    if (fd_tty < 0) {
        vt_num = 0;
        fd_tty = open("/dev/tty0", O_RDWR | O_NOCTTY);
    }
    if (fd_tty < 0) {
        printf("[-] trigger_sak failed to open tty: %s\n", strerror(errno));
        exit(1);
    }
    
    if (vt_num != 0) {
        if (ioctl(fd_tty, VT_ACTIVATE, vt_num) < 0) {
            printf("[-] VT_ACTIVATE failed: %s\n", strerror(errno));
        }
        if (ioctl(fd_tty, VT_WAITACTIVE, vt_num) < 0) {
            printf("[-] VT_WAITACTIVE failed: %s\n", strerror(errno));
        }
        printf("[+] Activated /dev/tty%d.\n", vt_num);
    }

    // Map KEY_A to K_SAK across all keymaps to ensure it triggers
    for (int i = 0; i < 256; i++) {
        struct kbentry ke;
        ke.kb_table = i;
        ke.kb_index = 30; // KEY_A
        ke.kb_value = 0x020F; // K_SAK
        if (ioctl(fd_tty, KDSKBENT, &ke) < 0) {
            // Some keymaps might not exist, ignore errors
        }
    }
    printf("[+] trigger_sak mapped KEY_A to K_SAK.\n");

    int ufd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
    if (ufd >= 0) {
        if (ioctl(ufd, UI_SET_EVBIT, EV_KEY) < 0) {
            printf("[-] UI_SET_EVBIT failed: %s\n", strerror(errno));
        }
        if (ioctl(ufd, UI_SET_KEYBIT, KEY_A) < 0) {
            printf("[-] UI_SET_KEYBIT failed: %s\n", strerror(errno));
        }

        struct uinput_setup usetup;
        memset(&usetup, 0, sizeof(usetup));
        usetup.id.bustype = BUS_USB;
        usetup.id.vendor = 0x1234;
        usetup.id.product = 0x5678;
        strcpy(usetup.name, "Virtual Keyboard");
        if (ioctl(ufd, UI_DEV_SETUP, &usetup) < 0) {
            printf("[-] UI_DEV_SETUP failed: %s, falling back to uinput_user_dev\n", strerror(errno));
            struct uinput_user_dev uud;
            memset(&uud, 0, sizeof(uud));
            uud.id.bustype = BUS_USB;
            uud.id.vendor = 0x1234;
            uud.id.product = 0x5678;
            strcpy(uud.name, "Virtual Keyboard");
            if (write(ufd, &uud, sizeof(uud)) < 0) {
                printf("[-] write uinput_user_dev failed: %s\n", strerror(errno));
            }
        }
        if (ioctl(ufd, UI_DEV_CREATE) < 0) {
            printf("[-] UI_DEV_CREATE failed: %s\n", strerror(errno));
        }

        usleep(100000); // Wait for input device to be registered

        struct input_event ie;
        
        // Press KEY_A
        memset(&ie, 0, sizeof(ie));
        ie.type = EV_KEY; ie.code = KEY_A; ie.value = 1;
        if (write(ufd, &ie, sizeof(ie)) < 0) {
            printf("[-] write EV_KEY failed: %s\n", strerror(errno));
        }

        memset(&ie, 0, sizeof(ie));
        ie.type = EV_SYN; ie.code = SYN_REPORT; ie.value = 0;
        if (write(ufd, &ie, sizeof(ie)) < 0) {
            printf("[-] write EV_SYN failed: %s\n", strerror(errno));
        }

        printf("[+] trigger_sak injected KEY_A.\n");
        
        // Wait for vc_SAK workqueue to execute and kill us
        sleep(2); 
        
        // If we survive:
        ioctl(ufd, UI_DEV_DESTROY);
        close(ufd);
    } else {
        printf("[-] trigger_sak failed to open /dev/uinput: %s\n", strerror(errno));
        exit(1);
    }
    close(fd_tty);
}

void trigger_pty() {
    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx >= 0) {
        int unlock = 0;
        if (ioctl(ptmx, TIOCSPTLCK, &unlock) < 0) {
            printf("[-] TIOCSPTLCK failed: %s\n", strerror(errno));
        }
        unsigned int ptn;
        if (ioctl(ptmx, TIOCGPTN, &ptn) == 0) {
            char pts_name[32];
            snprintf(pts_name, sizeof(pts_name), "/dev/pts/%u", ptn);
            int pts = open(pts_name, O_RDWR | O_NOCTTY);
            if (pts >= 0) {
                if (write(ptmx, "a", 1) < 0) {
                    printf("[-] trigger_pty failed to write to ptmx: %s\n", strerror(errno));
                } else {
                    printf("[+] trigger_pty wrote to ptmx.\n");
                }
                usleep(100000); // Wait for flush_to_ldisc workqueue to execute
                close(pts);
            } else {
                printf("[-] trigger_pty failed to open %s: %s\n", pts_name, strerror(errno));
            }
        } else {
            printf("[-] TIOCGPTN failed: %s\n", strerror(errno));
        }
        close(ptmx);
    } else {
        printf("[-] trigger_pty failed to open /dev/ptmx: %s\n", strerror(errno));
        exit(1);
    }
}

int main(void) {
    printf("[+] Starting reproducer...\n");

    // 1. Trigger &tty->termios_rwsem -> &port->mutex
    trigger_tcsets();

    // 2. Trigger console_lock -> &buf->lock
    // Do this in a child process because __do_SAK sends SIGKILL to processes
    // associated with the active console.
    pid_t pid = fork();
    if (pid < 0) {
        printf("[-] fork failed: %s\n", strerror(errno));
        exit(1);
    }
    if (pid == 0) {
        trigger_sak();
        exit(0);
    }
    int status;
    waitpid(pid, &status, 0);
    if (WIFSIGNALED(status)) {
        printf("[+] Child process for SAK killed by signal %d (expected if SAK triggered).\n", WTERMSIG(status));
    } else {
        printf("[+] Child process for SAK exited normally.\n");
    }

    // 3. Trigger &buf->lock -> &tty->termios_rwsem
    // This completes the circular dependency and triggers the lockdep splat.
    trigger_pty();

    printf("[+] Reproducer finished.\n");
    return 0;
}]

map[IsProbe:false RawCandidateReproC:#define _GNU_SOURCE
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <stdlib.h>
#include <linux/kd.h>
#include <linux/input.h>
#include <linux/uinput.h>
#include <linux/vt.h>
#include <string.h>
#include <stdio.h>
#include <sys/wait.h>
#include <errno.h>

#define TIOCSPTLCK	_IOW('T', 0x40, int)
#define TIOCGPTN	_IOR('T', 0x30, unsigned int)

void trigger_tcsets() {
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS1", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS2", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS3", O_RDWR | O_NOCTTY);
    if (fd_serial >= 0) {
        struct termios term;
        if (ioctl(fd_serial, TCGETS, &term) == 0) {
            if (ioctl(fd_serial, TCSETS, &term) < 0) {
                printf("[-] TCSETS failed: %s\n", strerror(errno));
            } else {
                printf("[+] trigger_tcsets successful.\n");
            }
        } else {
            printf("[-] TCGETS failed: %s\n", strerror(errno));
        }
        close(fd_serial);
    } else {
        printf("[-] trigger_tcsets failed to open serial port: %s\n", strerror(errno));
    }
}

void trigger_sak() {
    int vt_num = 5;
    int fd_tty = open("/dev/tty5", O_RDWR | O_NOCTTY);
    if (fd_tty < 0) {
        vt_num = 0;
        fd_tty = open("/dev/tty0", O_RDWR | O_NOCTTY);
    }
    if (fd_tty < 0) {
        printf("[-] trigger_sak failed to open tty: %s\n", strerror(errno));
        exit(1);
    }
    
    if (vt_num != 0) {
        if (ioctl(fd_tty, VT_ACTIVATE, vt_num) < 0) {
            printf("[-] VT_ACTIVATE failed: %s\n", strerror(errno));
        }
        if (ioctl(fd_tty, VT_WAITACTIVE, vt_num) < 0) {
            printf("[-] VT_WAITACTIVE failed: %s\n", strerror(errno));
        }
        printf("[+] Activated /dev/tty%d.\n", vt_num);
    }

    // Map KEY_A to K_SAK across all keymaps to ensure it triggers
    for (int i = 0; i < 256; i++) {
        struct kbentry ke;
        ke.kb_table = i;
        ke.kb_index = 30; // KEY_A
        ke.kb_value = 0x020F; // K_SAK
        if (ioctl(fd_tty, KDSKBENT, &ke) < 0) {
            // Some keymaps might not exist, ignore errors
        }
    }
    printf("[+] trigger_sak mapped KEY_A to K_SAK.\n");

    int ufd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
    if (ufd >= 0) {
        if (ioctl(ufd, UI_SET_EVBIT, EV_KEY) < 0) {
            printf("[-] UI_SET_EVBIT failed: %s\n", strerror(errno));
        }
        if (ioctl(ufd, UI_SET_KEYBIT, KEY_A) < 0) {
            printf("[-] UI_SET_KEYBIT failed: %s\n", strerror(errno));
        }

        struct uinput_setup usetup;
        memset(&usetup, 0, sizeof(usetup));
        usetup.id.bustype = BUS_USB;
        usetup.id.vendor = 0x1234;
        usetup.id.product = 0x5678;
        strcpy(usetup.name, "Virtual Keyboard");
        if (ioctl(ufd, UI_DEV_SETUP, &usetup) < 0) {
            printf("[-] UI_DEV_SETUP failed: %s, falling back to uinput_user_dev\n", strerror(errno));
            struct uinput_user_dev uud;
            memset(&uud, 0, sizeof(uud));
            uud.id.bustype = BUS_USB;
            uud.id.vendor = 0x1234;
            uud.id.product = 0x5678;
            strcpy(uud.name, "Virtual Keyboard");
            if (write(ufd, &uud, sizeof(uud)) < 0) {
                printf("[-] write uinput_user_dev failed: %s\n", strerror(errno));
            }
        }
        if (ioctl(ufd, UI_DEV_CREATE) < 0) {
            printf("[-] UI_DEV_CREATE failed: %s\n", strerror(errno));
        }

        usleep(100000); // Wait for input device to be registered

        struct input_event ie;
        
        // Press KEY_A
        memset(&ie, 0, sizeof(ie));
        ie.type = EV_KEY; ie.code = KEY_A; ie.value = 1;
        if (write(ufd, &ie, sizeof(ie)) < 0) {
            printf("[-] write EV_KEY failed: %s\n", strerror(errno));
        }

        memset(&ie, 0, sizeof(ie));
        ie.type = EV_SYN; ie.code = SYN_REPORT; ie.value = 0;
        if (write(ufd, &ie, sizeof(ie)) < 0) {
            printf("[-] write EV_SYN failed: %s\n", strerror(errno));
        }

        printf("[+] trigger_sak injected KEY_A.\n");
        
        // Wait for vc_SAK workqueue to execute and kill us
        sleep(2); 
        
        // If we survive:
        ioctl(ufd, UI_DEV_DESTROY);
        close(ufd);
    } else {
        printf("[-] trigger_sak failed to open /dev/uinput: %s\n", strerror(errno));
        exit(1);
    }
    close(fd_tty);
}

void trigger_pty() {
    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx >= 0) {
        int unlock = 0;
        if (ioctl(ptmx, TIOCSPTLCK, &unlock) < 0) {
            printf("[-] TIOCSPTLCK failed: %s\n", strerror(errno));
        }
        unsigned int ptn;
        if (ioctl(ptmx, TIOCGPTN, &ptn) == 0) {
            char pts_name[32];
            snprintf(pts_name, sizeof(pts_name), "/dev/pts/%u", ptn);
            int pts = open(pts_name, O_RDWR | O_NOCTTY);
            if (pts >= 0) {
                if (write(ptmx, "a", 1) < 0) {
                    printf("[-] trigger_pty failed to write to ptmx: %s\n", strerror(errno));
                } else {
                    printf("[+] trigger_pty wrote to ptmx.\n");
                }
                usleep(100000); // Wait for flush_to_ldisc workqueue to execute
                close(pts);
            } else {
                printf("[-] trigger_pty failed to open %s: %s\n", pts_name, strerror(errno));
            }
        } else {
            printf("[-] TIOCGPTN failed: %s\n", strerror(errno));
        }
        close(ptmx);
    } else {
        printf("[-] trigger_pty failed to open /dev/ptmx: %s\n", strerror(errno));
        exit(1);
    }
}

int main(void) {
    printf("[+] Starting reproducer...\n");

    // 1. Trigger &tty->termios_rwsem -> &port->mutex
    trigger_tcsets();

    // 2. Trigger console_lock -> &buf->lock
    // Do this in a child process because __do_SAK sends SIGKILL to processes
    // associated with the active console.
    pid_t pid = fork();
    if (pid < 0) {
        printf("[-] fork failed: %s\n", strerror(errno));
        exit(1);
    }
    if (pid == 0) {
        trigger_sak();
        exit(0);
    }
    int status;
    waitpid(pid, &status, 0);
    if (WIFSIGNALED(status)) {
        printf("[+] Child process for SAK killed by signal %d (expected if SAK triggered).\n", WTERMSIG(status));
    } else {
        printf("[+] Child process for SAK exited normally.\n");
    }

    // 3. Trigger &buf->lock -> &tty->termios_rwsem
    // This completes the circular dependency and triggers the lockdep splat.
    trigger_pty();

    printf("[+] Reproducer finished.\n");
    return 0;
}]

map[CurrentCandidateReproC:#define _GNU_SOURCE
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <stdlib.h>
#include <linux/kd.h>
#include <linux/input.h>
#include <linux/uinput.h>
#include <linux/vt.h>
#include <string.h>
#include <stdio.h>
#include <sys/wait.h>
#include <errno.h>

#define TIOCSPTLCK	_IOW('T', 0x40, int)
#define TIOCGPTN	_IOR('T', 0x30, unsigned int)

void trigger_tcsets() {
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS1", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS2", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS3", O_RDWR | O_NOCTTY);
    if (fd_serial >= 0) {
        struct termios term;
        if (ioctl(fd_serial, TCGETS, &term) == 0) {
            if (ioctl(fd_serial, TCSETS, &term) < 0) {
                printf("[-] TCSETS failed: %s\n", strerror(errno));
            } else {
                printf("[+] trigger_tcsets successful.\n");
            }
        } else {
            printf("[-] TCGETS failed: %s\n", strerror(errno));
        }
        close(fd_serial);
    } else {
        printf("[-] trigger_tcsets failed to open serial port: %s\n", strerror(errno));
    }
}

void trigger_sak() {
    int vt_num = 5;
    int fd_tty = open("/dev/tty5", O_RDWR | O_NOCTTY);
    if (fd_tty < 0) {
        vt_num = 0;
        fd_tty = open("/dev/tty0", O_RDWR | O_NOCTTY);
    }
    if (fd_tty < 0) {
        printf("[-] trigger_sak failed to open tty: %s\n", strerror(errno));
        exit(1);
    }
    
    if (vt_num != 0) {
        if (ioctl(fd_tty, VT_ACTIVATE, vt_num) < 0) {
            printf("[-] VT_ACTIVATE failed: %s\n", strerror(errno));
        }
        if (ioctl(fd_tty, VT_WAITACTIVE, vt_num) < 0) {
            printf("[-] VT_WAITACTIVE failed: %s\n", strerror(errno));
        }
        printf("[+] Activated /dev/tty%d.\n", vt_num);
    }

    // Map KEY_A to K_SAK across all keymaps to ensure it triggers
    for (int i = 0; i < 256; i++) {
        struct kbentry ke;
        ke.kb_table = i;
        ke.kb_index = 30; // KEY_A
        ke.kb_value = 0x020F; // K_SAK
        if (ioctl(fd_tty, KDSKBENT, &ke) < 0) {
            // Some keymaps might not exist, ignore errors
        }
    }
    printf("[+] trigger_sak mapped KEY_A to K_SAK.\n");

    int ufd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
    if (ufd >= 0) {
        if (ioctl(ufd, UI_SET_EVBIT, EV_KEY) < 0) {
            printf("[-] UI_SET_EVBIT failed: %s\n", strerror(errno));
        }
        if (ioctl(ufd, UI_SET_KEYBIT, KEY_A) < 0) {
            printf("[-] UI_SET_KEYBIT failed: %s\n", strerror(errno));
        }

        struct uinput_setup usetup;
        memset(&usetup, 0, sizeof(usetup));
        usetup.id.bustype = BUS_USB;
        usetup.id.vendor = 0x1234;
        usetup.id.product = 0x5678;
        strcpy(usetup.name, "Virtual Keyboard");
        if (ioctl(ufd, UI_DEV_SETUP, &usetup) < 0) {
            printf("[-] UI_DEV_SETUP failed: %s, falling back to uinput_user_dev\n", strerror(errno));
            struct uinput_user_dev uud;
            memset(&uud, 0, sizeof(uud));
            uud.id.bustype = BUS_USB;
            uud.id.vendor = 0x1234;
            uud.id.product = 0x5678;
            strcpy(uud.name, "Virtual Keyboard");
            if (write(ufd, &uud, sizeof(uud)) < 0) {
                printf("[-] write uinput_user_dev failed: %s\n", strerror(errno));
            }
        }
        if (ioctl(ufd, UI_DEV_CREATE) < 0) {
            printf("[-] UI_DEV_CREATE failed: %s\n", strerror(errno));
        }

        usleep(100000); // Wait for input device to be registered

        struct input_event ie;
        
        // Press KEY_A
        memset(&ie, 0, sizeof(ie));
        ie.type = EV_KEY; ie.code = KEY_A; ie.value = 1;
        if (write(ufd, &ie, sizeof(ie)) < 0) {
            printf("[-] write EV_KEY failed: %s\n", strerror(errno));
        }

        memset(&ie, 0, sizeof(ie));
        ie.type = EV_SYN; ie.code = SYN_REPORT; ie.value = 0;
        if (write(ufd, &ie, sizeof(ie)) < 0) {
            printf("[-] write EV_SYN failed: %s\n", strerror(errno));
        }

        printf("[+] trigger_sak injected KEY_A.\n");
        
        // Wait for vc_SAK workqueue to execute and kill us
        sleep(2); 
        
        // If we survive:
        ioctl(ufd, UI_DEV_DESTROY);
        close(ufd);
    } else {
        printf("[-] trigger_sak failed to open /dev/uinput: %s\n", strerror(errno));
        exit(1);
    }
    close(fd_tty);
}

void trigger_pty() {
    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx >= 0) {
        int unlock = 0;
        if (ioctl(ptmx, TIOCSPTLCK, &unlock) < 0) {
            printf("[-] TIOCSPTLCK failed: %s\n", strerror(errno));
        }
        unsigned int ptn;
        if (ioctl(ptmx, TIOCGPTN, &ptn) == 0) {
            char pts_name[32];
            snprintf(pts_name, sizeof(pts_name), "/dev/pts/%u", ptn);
            int pts = open(pts_name, O_RDWR | O_NOCTTY);
            if (pts >= 0) {
                if (write(ptmx, "a", 1) < 0) {
                    printf("[-] trigger_pty failed to write to ptmx: %s\n", strerror(errno));
                } else {
                    printf("[+] trigger_pty wrote to ptmx.\n");
                }
                usleep(100000); // Wait for flush_to_ldisc workqueue to execute
                close(pts);
            } else {
                printf("[-] trigger_pty failed to open %s: %s\n", pts_name, strerror(errno));
            }
        } else {
            printf("[-] TIOCGPTN failed: %s\n", strerror(errno));
        }
        close(ptmx);
    } else {
        printf("[-] trigger_pty failed to open /dev/ptmx: %s\n", strerror(errno));
        exit(1);
    }
}

int main(void) {
    printf("[+] Starting reproducer...\n");

    // 1. Trigger &tty->termios_rwsem -> &port->mutex
    trigger_tcsets();

    // 2. Trigger console_lock -> &buf->lock
    // Do this in a child process because __do_SAK sends SIGKILL to processes
    // associated with the active console.
    pid_t pid = fork();
    if (pid < 0) {
        printf("[-] fork failed: %s\n", strerror(errno));
        exit(1);
    }
    if (pid == 0) {
        trigger_sak();
        exit(0);
    }
    int status;
    waitpid(pid, &status, 0);
    if (WIFSIGNALED(status)) {
        printf("[+] Child process for SAK killed by signal %d (expected if SAK triggered).\n", WTERMSIG(status));
    } else {
        printf("[+] Child process for SAK exited normally.\n");
    }

    // 3. Trigger &buf->lock -> &tty->termios_rwsem
    // This completes the circular dependency and triggers the lockdep splat.
    trigger_pty();

    printf("[+] Reproducer finished.\n");
    return 0;
}]

map[CompilerError: FormattedReproC:#define _GNU_SOURCE
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <stdlib.h>
#include <linux/kd.h>
#include <linux/input.h>
#include <linux/uinput.h>
#include <linux/vt.h>
#include <string.h>
#include <stdio.h>
#include <sys/wait.h>
#include <errno.h>

#define TIOCSPTLCK	_IOW('T', 0x40, int)
#define TIOCGPTN	_IOR('T', 0x30, unsigned int)

void trigger_tcsets() {
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS1", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS2", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS3", O_RDWR | O_NOCTTY);
    if (fd_serial >= 0) {
        struct termios term;
        if (ioctl(fd_serial, TCGETS, &term) == 0) {
            if (ioctl(fd_serial, TCSETS, &term) < 0) {
                printf("[-] TCSETS failed: %s\n", strerror(errno));
            } else {
                printf("[+] trigger_tcsets successful.\n");
            }
        } else {
            printf("[-] TCGETS failed: %s\n", strerror(errno));
        }
        close(fd_serial);
    } else {
        printf("[-] trigger_tcsets failed to open serial port: %s\n", strerror(errno));
    }
}

void trigger_sak() {
    int vt_num = 5;
    int fd_tty = open("/dev/tty5", O_RDWR | O_NOCTTY);
    if (fd_tty < 0) {
        vt_num = 0;
        fd_tty = open("/dev/tty0", O_RDWR | O_NOCTTY);
    }
    if (fd_tty < 0) {
        printf("[-] trigger_sak failed to open tty: %s\n", strerror(errno));
        exit(1);
    }
    
    if (vt_num != 0) {
        if (ioctl(fd_tty, VT_ACTIVATE, vt_num) < 0) {
            printf("[-] VT_ACTIVATE failed: %s\n", strerror(errno));
        }
        if (ioctl(fd_tty, VT_WAITACTIVE, vt_num) < 0) {
            printf("[-] VT_WAITACTIVE failed: %s\n", strerror(errno));
        }
        printf("[+] Activated /dev/tty%d.\n", vt_num);
    }

    // Map KEY_A to K_SAK across all keymaps to ensure it triggers
    for (int i = 0; i < 256; i++) {
        struct kbentry ke;
        ke.kb_table = i;
        ke.kb_index = 30; // KEY_A
        ke.kb_value = 0x020F; // K_SAK
        if (ioctl(fd_tty, KDSKBENT, &ke) < 0) {
            // Some keymaps might not exist, ignore errors
        }
    }
    printf("[+] trigger_sak mapped KEY_A to K_SAK.\n");

    int ufd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
    if (ufd >= 0) {
        if (ioctl(ufd, UI_SET_EVBIT, EV_KEY) < 0) {
            printf("[-] UI_SET_EVBIT failed: %s\n", strerror(errno));
        }
        if (ioctl(ufd, UI_SET_KEYBIT, KEY_A) < 0) {
            printf("[-] UI_SET_KEYBIT failed: %s\n", strerror(errno));
        }

        struct uinput_setup usetup;
        memset(&usetup, 0, sizeof(usetup));
        usetup.id.bustype = BUS_USB;
        usetup.id.vendor = 0x1234;
        usetup.id.product = 0x5678;
        strcpy(usetup.name, "Virtual Keyboard");
        if (ioctl(ufd, UI_DEV_SETUP, &usetup) < 0) {
            printf("[-] UI_DEV_SETUP failed: %s, falling back to uinput_user_dev\n", strerror(errno));
            struct uinput_user_dev uud;
            memset(&uud, 0, sizeof(uud));
            uud.id.bustype = BUS_USB;
            uud.id.vendor = 0x1234;
            uud.id.product = 0x5678;
            strcpy(uud.name, "Virtual Keyboard");
            if (write(ufd, &uud, sizeof(uud)) < 0) {
                printf("[-] write uinput_user_dev failed: %s\n", strerror(errno));
            }
        }
        if (ioctl(ufd, UI_DEV_CREATE) < 0) {
            printf("[-] UI_DEV_CREATE failed: %s\n", strerror(errno));
        }

        usleep(100000); // Wait for input device to be registered

        struct input_event ie;
        
        // Press KEY_A
        memset(&ie, 0, sizeof(ie));
        ie.type = EV_KEY; ie.code = KEY_A; ie.value = 1;
        if (write(ufd, &ie, sizeof(ie)) < 0) {
            printf("[-] write EV_KEY failed: %s\n", strerror(errno));
        }

        memset(&ie, 0, sizeof(ie));
        ie.type = EV_SYN; ie.code = SYN_REPORT; ie.value = 0;
        if (write(ufd, &ie, sizeof(ie)) < 0) {
            printf("[-] write EV_SYN failed: %s\n", strerror(errno));
        }

        printf("[+] trigger_sak injected KEY_A.\n");
        
        // Wait for vc_SAK workqueue to execute and kill us
        sleep(2); 
        
        // If we survive:
        ioctl(ufd, UI_DEV_DESTROY);
        close(ufd);
    } else {
        printf("[-] trigger_sak failed to open /dev/uinput: %s\n", strerror(errno));
        exit(1);
    }
    close(fd_tty);
}

void trigger_pty() {
    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx >= 0) {
        int unlock = 0;
        if (ioctl(ptmx, TIOCSPTLCK, &unlock) < 0) {
            printf("[-] TIOCSPTLCK failed: %s\n", strerror(errno));
        }
        unsigned int ptn;
        if (ioctl(ptmx, TIOCGPTN, &ptn) == 0) {
            char pts_name[32];
            snprintf(pts_name, sizeof(pts_name), "/dev/pts/%u", ptn);
            int pts = open(pts_name, O_RDWR | O_NOCTTY);
            if (pts >= 0) {
                if (write(ptmx, "a", 1) < 0) {
                    printf("[-] trigger_pty failed to write to ptmx: %s\n", strerror(errno));
                } else {
                    printf("[+] trigger_pty wrote to ptmx.\n");
                }
                usleep(100000); // Wait for flush_to_ldisc workqueue to execute
                close(pts);
            } else {
                printf("[-] trigger_pty failed to open %s: %s\n", pts_name, strerror(errno));
            }
        } else {
            printf("[-] TIOCGPTN failed: %s\n", strerror(errno));
        }
        close(ptmx);
    } else {
        printf("[-] trigger_pty failed to open /dev/ptmx: %s\n", strerror(errno));
        exit(1);
    }
}

int main(void) {
    printf("[+] Starting reproducer...\n");

    // 1. Trigger &tty->termios_rwsem -> &port->mutex
    trigger_tcsets();

    // 2. Trigger console_lock -> &buf->lock
    // Do this in a child process because __do_SAK sends SIGKILL to processes
    // associated with the active console.
    pid_t pid = fork();
    if (pid < 0) {
        printf("[-] fork failed: %s\n", strerror(errno));
        exit(1);
    }
    if (pid == 0) {
        trigger_sak();
        exit(0);
    }
    int status;
    waitpid(pid, &status, 0);
    if (WIFSIGNALED(status)) {
        printf("[+] Child process for SAK killed by signal %d (expected if SAK triggered).\n", WTERMSIG(status));
    } else {
        printf("[+] Child process for SAK exited normally.\n");
    }

    // 3. Trigger &buf->lock -> &tty->termios_rwsem
    // This completes the circular dependency and triggers the lockdep splat.
    trigger_pty();

    printf("[+] Reproducer finished.\n");
    return 0;
}]

map[CompilerError:]

map[CandidateBugTitle:possible deadlock in n_tty_flush_buffer CandidateCrashReport:======================================================
WARNING: possible circular locking dependency detected
syzkaller #1 Not tainted
------------------------------------------------------
kworker/0:5/5693 is trying to acquire lock:
ffff8881fafd02c8 (&tty->termios_rwsem){++++}-{4:4}, at: class_rwsem_write_constructor include/linux/rwsem.h:270 [inline]
ffff8881fafd02c8 (&tty->termios_rwsem){++++}-{4:4}, at: n_tty_flush_buffer+0x30/0x230 drivers/tty/n_tty.c:349

but task is already holding lock:
ffff8881961b50b8 (&buf->lock){+.+.}-{4:4}, at: tty_buffer_flush+0x74/0x2b0 drivers/tty/tty_buffer.c:236

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&buf->lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
       tty_buffer_flush+0x74/0x2b0 drivers/tty/tty_buffer.c:236
       tty_ldisc_flush+0x6b/0xc0 drivers/tty/tty_ldisc.c:388
       __do_SAK+0x25e/0x680 drivers/tty/tty_io.c:3025
       vc_SAK+0x78/0x220 drivers/tty/vt/vt_ioctl.c:994
       process_one_work kernel/workqueue.c:3322 [inline]
       process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
       worker_thread+0x92d/0xe10 kernel/workqueue.c:3486
       kthread+0x388/0x470 kernel/kthread.c:436
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #2 (console_lock){+.+.}-{0:0}:
       console_lock+0x76/0x90 kernel/printk/printk.c:2896
       uart_configure_port drivers/tty/serial/serial_core.c:2530 [inline]
       serial_core_add_one_port drivers/tty/serial/serial_core.c:3101 [inline]
       serial_core_register_port+0xc47/0x2840 drivers/tty/serial/serial_core.c:3322
       serial8250_register_8250_port+0x16b4/0x2090 drivers/tty/serial/8250/8250_core.c:828
       serial_pnp_probe+0x56a/0x7f0 drivers/tty/serial/8250/8250_pnp.c:480
       pnp_device_probe+0x30b/0x4c0 drivers/pnp/driver.c:111
       call_driver_probe drivers/base/dd.c:-1 [inline]
       really_probe+0x254/0xae0 drivers/base/dd.c:706
       __driver_probe_device+0x1e8/0x360 drivers/base/dd.c:868
       driver_probe_device+0x4f/0x240 drivers/base/dd.c:898
       __driver_attach+0x339/0x600 drivers/base/dd.c:1292
       bus_for_each_dev+0x23b/0x2c0 drivers/base/bus.c:383
       bus_add_driver+0x345/0x670 drivers/base/bus.c:763
       driver_register+0x23a/0x320 drivers/base/driver.c:174
       serial8250_init+0x8f/0x160 drivers/tty/serial/8250/8250_platform.c:317
       do_one_initcall+0x250/0x870 init/main.c:1347
       do_initcall_level+0x10a/0x1a0 init/main.c:1409
       do_initcalls+0x59/0xa0 init/main.c:1425
       kernel_init_freeable+0x29d/0x3e0 init/main.c:1658
       kernel_init+0x1d/0x1d0 init/main.c:1548
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #1 (&port->mutex){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
       class_mutex_constructor include/linux/mutex.h:253 [inline]
       uart_set_termios+0x81/0x710 drivers/tty/serial/serial_core.c:1645
       tty_set_termios+0xcaf/0x1800 drivers/tty/tty_ioctl.c:341
       set_termios+0x53d/0x6c0 drivers/tty/tty_ioctl.c:516
       tty_mode_ioctl+0x49c/0x7c0 drivers/tty/tty_ioctl.c:-1
       tty_ioctl+0x9bd/0xdd0 drivers/tty/tty_io.c:2801
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&tty->termios_rwsem){++++}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x1520/0x2cf0 kernel/locking/lockdep.c:5237
       lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
       down_write+0x96/0x200 kernel/locking/rwsem.c:1631
       class_rwsem_write_constructor include/linux/rwsem.h:270 [inline]
       n_tty_flush_buffer+0x30/0x230 drivers/tty/n_tty.c:349
       tty_buffer_flush+0x1ec/0x2b0 drivers/tty/tty_buffer.c:248
       tty_ldisc_flush+0x6b/0xc0 drivers/tty/tty_ldisc.c:388
       __do_SAK+0x25e/0x680 drivers/tty/tty_io.c:3025
       vc_SAK+0x78/0x220 drivers/tty/vt/vt_ioctl.c:994
       process_one_work kernel/workqueue.c:3322 [inline]
       process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
       worker_thread+0x92d/0xe10 kernel/workqueue.c:3486
       kthread+0x388/0x470 kernel/kthread.c:436
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

other info that might help us debug this:

Chain exists of:
  &tty->termios_rwsem --> console_lock --> &buf->lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&buf->lock);
                               lock(console_lock);
                               lock(&buf->lock);
  lock(&tty->termios_rwsem);

 *** DEADLOCK ***

5 locks held by kworker/0:5/5693:
 #0: ffff88810006b140 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3297 [inline]
 #0: ffff88810006b140 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3405
 #1: ffffc90003ea7c40 ((work_completion)(&vc_cons[currcons].SAK_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3297 [inline]
 #1: ffffc90003ea7c40 ((work_completion)(&vc_cons[currcons].SAK_work)){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3405
 #2: ffffffff8eb55920 (console_lock){+.+.}-{0:0}, at: class_console_lock_constructor include/linux/console.h:734 [inline]
 #2: ffffffff8eb55920 (console_lock){+.+.}-{0:0}, at: vc_SAK+0x28/0x220 drivers/tty/vt/vt_ioctl.c:985
 #3: ffff8881fafd00a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref drivers/tty/tty_ldisc.c:263 [inline]
 #3: ffff8881fafd00a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_flush+0x20/0xc0 drivers/tty/tty_ldisc.c:386
 #4: ffff8881961b50b8 (&buf->lock){+.+.}-{4:4}, at: tty_buffer_flush+0x74/0x2b0 drivers/tty/tty_buffer.c:236

stack backtrace:
CPU: 0 UID: 0 PID: 5693 Comm: kworker/0:5 Not tainted syzkaller #1 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: events vc_SAK
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043
 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3165 [inline]
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x1520/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
 down_write+0x96/0x200 kernel/locking/rwsem.c:1631
 class_rwsem_write_constructor include/linux/rwsem.h:270 [inline]
 n_tty_flush_buffer+0x30/0x230 drivers/tty/n_tty.c:349
 tty_buffer_flush+0x1ec/0x2b0 drivers/tty/tty_buffer.c:248
 tty_ldisc_flush+0x6b/0xc0 drivers/tty/tty_ldisc.c:388
 __do_SAK+0x25e/0x680 drivers/tty/tty_io.c:3025
 vc_SAK+0x78/0x220 drivers/tty/vt/vt_ioctl.c:994
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0x92d/0xe10 kernel/workqueue.c:3486
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
tty tty5: SAK: killed process 5856 (syz-executor241): by fd#3
 CandidateReproduced:true ConsoleOutput:[   70.393413][   T33] kauditd_printk_skb: 10 callbacks suppressed
[   70.393425][   T33] audit: type=1400 audit(1786492918.814:201): avc:  denied  { transition } for  pid=5830 comm="sshd-session" path="/bin/sh" dev="sda1" ino=90 scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   70.402610][   T33] audit: type=1400 audit(1786492918.814:202): avc:  denied  { noatsecure } for  pid=5830 comm="sshd-session" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   70.408936][   T33] audit: type=1400 audit(1786492918.814:203): avc:  denied  { rlimitinh } for  pid=5830 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   70.414729][   T33] audit: type=1400 audit(1786492918.814:204): avc:  denied  { siginh } for  pid=5830 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   71.829223][ T1376] ieee802154 phy0 wpan0: encryption failed: -22
[   71.831342][ T1376] ieee802154 phy1 wpan1: encryption failed: -22
[   72.855342][   T33] audit: type=1400 audit(1786492921.274:205): avc:  denied  { write } for  pid=5832 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   72.905174][   T33] audit: type=1400 audit(1786492921.324:206): avc:  denied  { write } for  pid=5835 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   73.606571][   T33] audit: type=1400 audit(1786492922.024:207): avc:  denied  { write } for  pid=5842 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   73.660017][   T33] audit: type=1400 audit(1786492922.084:208): avc:  denied  { write } for  pid=5845 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
Warning: Permanently added '[localhost]:59174' (ED25519) to the list of known hosts.
[   74.426076][   T33] audit: type=1400 audit(1786492922.844:209): avc:  denied  { write } for  pid=5856 comm="syz-executor241" name="uinput" dev="devtmpfs" ino=924 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:event_device_t tclass=chr_file permissive=1
[   74.429762][ T5856] input: Virtual Keyboard as /devices/virtual/input/input4
[   74.435675][   T33] audit: type=1400 audit(1786492922.844:210): avc:  denied  { open } for  pid=5856 comm="syz-executor241" path="/dev/uinput" dev="devtmpfs" ino=924 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:event_device_t tclass=chr_file permissive=1
[   74.550716][ T5693] 
[   74.550723][ T5693] ======================================================
[   74.550727][ T5693] WARNING: possible circular locking dependency detected
[   74.550731][ T5693] syzkaller #1 Not tainted
[   74.550735][ T5693] ------------------------------------------------------
[   74.550738][ T5693] kworker/0:5/5693 is trying to acquire lock:
[   74.550743][ T5693] ffff8881fafd02c8 (&tty->termios_rwsem){++++}-{4:4}, at: n_tty_flush_buffer+0x30/0x230
[   74.550771][ T5693] 
[   74.550771][ T5693] but task is already holding lock:
[   74.550773][ T5693] ffff8881961b50b8 (&buf->lock){+.+.}-{4:4}, at: tty_buffer_flush+0x74/0x2b0
[   74.550791][ T5693] 
[   74.550791][ T5693] which lock already depends on the new lock.
[   74.550791][ T5693] 
[   74.550794][ T5693] 
[   74.550794][ T5693] the existing dependency chain (in reverse order) is:
[   74.550797][ T5693] 
[   74.550797][ T5693] -> #3 (&buf->lock){+.+.}-{4:4}:
[   74.550807][ T5693]        __mutex_lock+0x19d/0x1550
[   74.550815][ T5693]        tty_buffer_flush+0x74/0x2b0
[   74.550823][ T5693]        tty_ldisc_flush+0x6b/0xc0
[   74.550830][ T5693]        __do_SAK+0x25e/0x680
[   74.550838][ T5693]        vc_SAK+0x78/0x220
[   74.550844][ T5693]        process_scheduled_works+0xa8e/0x14e0
[   74.550853][ T5693]        worker_thread+0x92d/0xe10
[   74.550862][ T5693]        kthread+0x388/0x470
[   74.550868][ T5693]        ret_from_fork+0x514/0xb70
[   74.550879][ T5693]        ret_from_fork_asm+0x1a/0x30
[   74.550890][ T5693] 
[   74.550890][ T5693] -> #2 (console_lock){+.+.}-{0:0}:
[   74.550900][ T5693]        console_lock+0x76/0x90
[   74.550908][ T5693]        serial_core_register_port+0xc47/0x2840
[   74.550916][ T5693]        serial8250_register_8250_port+0x16b4/0x2090
[   74.550923][ T5693]        serial_pnp_probe+0x56a/0x7f0
[   74.550930][ T5693]        pnp_device_probe+0x30b/0x4c0
[   74.550937][ T5693]        really_probe+0x254/0xae0
[   74.550945][ T5693]        __driver_probe_device+0x1e8/0x360
[   74.550952][ T5693]        driver_probe_device+0x4f/0x240
[   74.550960][ T5693]        __driver_attach+0x339/0x600
[   74.550967][ T5693]        bus_for_each_dev+0x23b/0x2c0
[   74.550976][ T5693]        bus_add_driver+0x345/0x670
[   74.550985][ T5693]        driver_register+0x23a/0x320
[   74.550993][ T5693]        serial8250_init+0x8f/0x160
[   74.551005][ T5693]        do_one_initcall+0x250/0x870
[   74.551015][ T5693]        do_initcall_level+0x10a/0x1a0
[   74.551023][ T5693]        do_initcalls+0x59/0xa0
[   74.551028][ T5693]        kernel_init_freeable+0x29d/0x3e0
[   74.551034][ T5693]        kernel_init+0x1d/0x1d0
[   74.551043][ T5693]        ret_from_fork+0x514/0xb70
[   74.551053][ T5693]        ret_from_fork_asm+0x1a/0x30
[   74.551062][ T5693] 
[   74.551062][ T5693] -> #1 (&port->mutex){+.+.}-{4:4}:
[   74.551073][ T5693]        __mutex_lock+0x19d/0x1550
[   74.551079][ T5693]        uart_set_termios+0x81/0x710
[   74.551087][ T5693]        tty_set_termios+0xcaf/0x1800
[   74.551094][ T5693]        set_termios+0x53d/0x6c0
[   74.551100][ T5693]        tty_mode_ioctl+0x49c/0x7c0
[   74.551106][ T5693]        tty_ioctl+0x9bd/0xdd0
[   74.551113][ T5693]        __se_sys_ioctl+0xfc/0x170
[   74.551123][ T5693]        do_syscall_64+0x174/0x580
[   74.551130][ T5693]        entry_SYSCALL_64_after_hwframe+0x77/0x7f
[   74.551137][ T5693] 
[   74.551137][ T5693] -> #0 (&tty->termios_rwsem){++++}-{4:4}:
[   74.551147][ T5693]        __lock_acquire+0x1520/0x2cf0
[   74.551153][ T5693]        lock_acquire+0x106/0x350
[   74.551159][ T5693]        down_write+0x96/0x200
[   74.551166][ T5693]        n_tty_flush_buffer+0x30/0x230
[   74.551175][ T5693]        tty_buffer_flush+0x1ec/0x2b0
[   74.551183][ T5693]        tty_ldisc_flush+0x6b/0xc0
[   74.551190][ T5693]        __do_SAK+0x25e/0x680
[   74.551197][ T5693]        vc_SAK+0x78/0x220
[   74.551203][ T5693]        process_scheduled_works+0xa8e/0x14e0
[   74.551211][ T5693]        worker_thread+0x92d/0xe10
[   74.551219][ T5693]        kthread+0x388/0x470
[   74.551225][ T5693]        ret_from_fork+0x514/0xb70
[   74.551234][ T5693]        ret_from_fork_asm+0x1a/0x30
[   74.551244][ T5693] 
[   74.551244][ T5693] other info that might help us debug this:
[   74.551244][ T5693] 
[   74.551247][ T5693] Chain exists of:
[   74.551247][ T5693]   &tty->termios_rwsem --> console_lock --> &buf->lock
[   74.551247][ T5693] 
[   74.551259][ T5693]  Possible unsafe locking scenario:
[   74.551259][ T5693] 
[   74.551261][ T5693]        CPU0                    CPU1
[   74.551285][ T5693]        ----                    ----
[   74.551288][ T5693]   lock(&buf->lock);
[   74.551294][ T5693]                                lock(console_lock);
[   74.551299][ T5693]                                lock(&buf->lock);
[   74.551305][ T5693]   lock(&tty->termios_rwsem);
[   74.551310][ T5693] 
[   74.551310][ T5693]  *** DEADLOCK ***
[   74.551310][ T5693] 
[   74.551312][ T5693] 5 locks held by kworker/0:5/5693:
[   74.551316][ T5693]  #0: ffff88810006b140 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0
[   74.551336][ T5693]  #1: ffffc90003ea7c40 ((work_completion)(&vc_cons[currcons].SAK_work)){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0
[   74.551391][ T5693]  #2: ffffffff8eb55920 (console_lock){+.+.}-{0:0}, at: vc_SAK+0x28/0x220
[   74.551407][ T5693]  #3: ffff8881fafd00a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_flush+0x20/0xc0
[   74.551425][ T5693]  #4: ffff8881961b50b8 (&buf->lock){+.+.}-{4:4}, at: tty_buffer_flush+0x74/0x2b0
[   74.551443][ T5693] 
[   74.551443][ T5693] stack backtrace:
[   74.551462][ T5693] CPU: 0 UID: 0 PID: 5693 Comm: kworker/0:5 Not tainted syzkaller #1 PREEMPT(full) 
[   74.551470][ T5693] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[   74.551475][ T5693] Workqueue: events vc_SAK
[   74.551482][ T5693] Call Trace:
[   74.551486][ T5693]  <TASK>
[   74.551490][ T5693]  dump_stack_lvl+0xe8/0x150
[   74.551500][ T5693]  print_circular_bug+0x2e1/0x300
[   74.551509][ T5693]  check_noncircular+0x12e/0x150
[   74.551522][ T5693]  __lock_acquire+0x1520/0x2cf0
[   74.551529][ T5693]  ? __pfx___mutex_trylock_common+0x10/0x10
[   74.551538][ T5693]  ? rcu_is_watching+0x15/0xb0
[   74.551547][ T5693]  ? trace_contention_end+0x3d/0x140
[   74.551555][ T5693]  ? n_tty_flush_buffer+0x30/0x230
[   74.551564][ T5693]  lock_acquire+0x106/0x350
[   74.551570][ T5693]  ? n_tty_flush_buffer+0x30/0x230
[   74.551582][ T5693]  down_write+0x96/0x200
[   74.551589][ T5693]  ? n_tty_flush_buffer+0x30/0x230
[   74.551599][ T5693]  ? __pfx_down_write+0x10/0x10
[   74.551608][ T5693]  ? __pfx_n_tty_flush_buffer+0x10/0x10
[   74.551622][ T5693]  n_tty_flush_buffer+0x30/0x230
[   74.551635][ T5693]  ? tty_buffer_flush+0x1df/0x2b0
[   74.551648][ T5693]  ? __pfx_n_tty_flush_buffer+0x10/0x10
[   74.551658][ T5693]  tty_buffer_flush+0x1ec/0x2b0
[   74.551666][ T5693]  tty_ldisc_flush+0x6b/0xc0
[   74.551674][ T5693]  __do_SAK+0x25e/0x680
[   74.551683][ T5693]  ? _raw_spin_unlock_irqrestore+0x30/0x80
[   74.551694][ T5693]  vc_SAK+0x78/0x220
[   74.551700][ T5693]  ? process_scheduled_works+0xa20/0x14e0
[   74.551709][ T5693]  process_scheduled_works+0xa8e/0x14e0
[   74.551721][ T5693]  ? __pfx_process_scheduled_works+0x10/0x10
[   74.551729][ T5693]  ? do_raw_spin_lock+0x12b/0x2f0
[   74.551741][ T5693]  worker_thread+0x92d/0xe10
[   74.551751][ T5693]  ? _raw_spin_unlock_irqrestore+0x30/0x80
[   74.551763][ T5693]  kthread+0x388/0x470
[   74.551769][ T5693]  ? __pfx_worker_thread+0x10/0x10
[   74.551778][ T5693]  ? __pfx_kthread+0x10/0x10
[   74.551784][ T5693]  ret_from_fork+0x514/0xb70
[   74.551795][ T5693]  ? __pfx_ret_from_fork+0x10/0x10
[   74.551805][ T5693]  ? __switch_to+0xc89/0x1420
[   74.551814][ T5693]  ? __pfx_kthread+0x10/0x10
[   74.551820][ T5693]  ret_from_fork_asm+0x1a/0x30
[   74.551833][ T5693]  </TASK>
[   74.552445][ T5693] tty tty5: SAK: killed process 5856 (syz-executor241): by fd#3
[+] Starting reproducer...
[+] trigger_tcsets successful.
[+] Child process for SAK killed by signal 9 (expected if SAK triggered).
[-] TIOCSPTLCK failed: Inappropriate ioctl for device
[-] trigger_pty failed to open /dev/pts/0: Input/output error
[+] Reproducer finished.
[   76.613056][   T33] kauditd_printk_skb: 11 callbacks suppressed
[   76.613066][   T33] audit: type=1400 audit(1786492925.034:222): avc:  denied  { write } for  pid=5890 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   76.646560][   T33] audit: type=1400 audit(1786492925.064:223): avc:  denied  { write } for  pid=5893 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   82.069355][    T9] cfg80211: failed to load regulatory.db
 OtherCrashReports:<nil> StraceOutput: TestError:]

map[TruncatedConsoleOutput:[   70.393413][   T33] kauditd_printk_skb: 10 callbacks suppressed
[   70.393425][   T33] audit: type=1400 audit(1786492918.814:201): avc:  denied  { transition } for  pid=5830 comm="sshd-session" path="/bin/sh" dev="sda1" ino=90 scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   70.402610][   T33] audit: type=1400 audit(1786492918.814:202): avc:  denied  { noatsecure } for  pid=5830 comm="sshd-session" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   70.408936][   T33] audit: type=1400 audit(1786492918.814:203): avc:  denied  { rlimitinh } for  pid=5830 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   70.414729][   T33] audit: type=1400 audit(1786492918.814:204): avc:  denied  { siginh } for  pid=5830 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   71.829223][ T1376] ieee802154 phy0 wpan0: encryption failed: -22
[   71.831342][ T1376] ieee802154 phy1 wpan1: encryption failed: -22
[   72.855342][   T33] audit: type=1400 audit(1786492921.274:205): avc:  denied  { write } for  pid=5832 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   72.905174][   T33] audit: type=1400 audit(1786492921.324:206): avc:  denied  { write } for  pid=5835 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   73.606571][   T33] audit: type=1400 audit(1786492922.024:207): avc:  denied  { write } for  pid=5842 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   73.660017][   T33] audit: type=1400 audit(1786492922.084:208): avc:  denied  { write } for  pid=5845 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
Warning: Permanently added '[localhost]:59174' (ED25519) to the list of known hosts.
[   74.426076][   T33] audit: type=1400 audit(1786492922.844:209): avc:  denied  { write } for  pid=5856 comm="syz-executor241" name="uinput" dev="devtmpfs" ino=924 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:event_device_t tclass=chr_file permissive=1
[   74.429762][ T5856] input: Virtual Keyboard as /devices/virtual/input/input4
[   74.435675][   T33] audit: type=1400 audit(1786492922.844:210): avc:  denied  { open } for  pid=5856 comm="syz-executor241" path="/dev/uinput" dev="devtmpfs" ino=924 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:event_device_t tclass=chr_file permissive=1
[   74.550716][ T5693] 
[   74.550723][ T5693] ======================================================
[   74.550727][ T5693] WARNING: possible circular locking dependency detected
[   74.550731][ T5693] syzkaller #1 Not tainted
[   74.550735][ T5693] ------------------------------------------------------
[   74.550738][ T5693] kworker/0:5/5693 is trying to acquire lock:
[   74.550743][ T5693] ffff8881fafd02c8 (&tty->termios_rwsem){++++}-{4:4}, at: n_tty_flush_buffer+0x30/0x230
[   74.550771][ T5693] 
[   74.550771][ T5693] but task is already holding lock:
[   74.550773][ T5693] ffff8881961b50b8 (&buf->lock){+.+.}-{4:4}, at: tty_buffer_flush+0x74/0x2b0
[   74.550791][ T5693] 
[   74.550791][ T5693] which lock already depends on the new lock.
[   74.550791][ T5693] 
[   74.550794][ T5693] 
[   74.550794][ T5693] the existing dependency chain (in reverse order) is:
[   74.550797][ T5693] 
[   74.550797][ T5693] -> #3 (&buf->lock){+.+.}-{4:4}:
[   74.550807][ T5693]        __mutex_lock+0x19d/0x1550
[   74.550815][ T5693]        tty_buffer_flush+0x74/0x2b0
[   74.550823][ T5693]        tty_ldisc_flush+0x6b/0xc0
[   74.550830][ T5693]        __do_SAK+0x25e/0x680
[   74.550838][ T5693]        vc_SAK+0x78/0x220
[   74.550844][ T5693]        process_scheduled_works+0xa8e/0x14e0
[   74.550853][ T5693]        worker_thread+0x92d/0xe10
[   74.550862][ T5693]        kthread+0x388/0x470
[   74.550868][ T5693]        ret_from_fork+0x514/0xb70
[   74.550879][ T5693]        ret_from_fork_asm+0x1a/0x30
[   74.550890][ T5693] 
[   74.550890][ T5693] -> #2 (console_lock){+.+.}-{0:0}:
[   74.550900][ T5693]        console_lock+0x76/0x90
[   74.550908][ T5693]        serial_core_register_port+0xc47/0x2840
[   74.550916][ T5693]        serial8250_register_8250_port+0x16b4/0x2090
[   74.550923][ T5693]        serial_pnp_probe+0x56a/0x7f0
[   74.550930][ T5693]        pnp_device_probe+0x30b/0x4c0
[   74.550937][ T5693]        really_probe+0x254/0xae0
[   74.550945][ T5693]        __driver_probe_device+0x1e8/0x360
[   74.550952][ T5693]        driver_probe_device+0x4f/0x240
[   74.550960][ T5693]        __driver_attach+0x339/0x600
[   74.550967][ T5693]        bus_for_each_dev+0x23b/0x2c0
[   74.550976][ T5693]        bus_add_driver+0x345/0x670
[   74.550985][ T5693]        driver_register+0x23a/0x320
[   74.550993][ T5693]        serial8250_init+0x8f/0x160
[   74.551005][ T5693]        do_one_initcall+0x250/0x870
[   74.551015][ T5693]        do_initcall_level+0x10a/0x1a0
[   74.551023][ T5693]        do_initcalls+0x59/0xa0
[   74.551028][ T5693]        kernel_init_freeable+0x29d/0x3e0
[   74.551034][ T5693]        kernel_init+0x1d/0x1d0
[   74.551043][ T5693]        ret_from_fork+0x514/0xb70
[   74.551053][ T5693]        ret_from_fork_asm+0x1a/0x30
[   74.551062][ T5693] 
[   74.551062][ T5693] -> #1 (&port->mutex){+.+.}-{4:4}:
[   74.551073][ T5693]        __mutex_lock+0x19d/0x1550
[   74.551079][ T5693]        uart_set_termios+0x81/0x710
[   74.551087][ T5693]        tty_set_termios+0xcaf/0x1800
[   74.551094][ T5693]        set_termios+0x53d/0x6c0
[   74.551100][ T5693]        tty_mode_ioctl+0x49c/0x7c0
[   74.551106][ T5693]        tty_ioctl+0x9bd/0xdd0
[   74.551113][ T5693]        __se_sys_ioctl+0xfc/0x170
[   74.551123][ T5693]        do_syscall_64+0x174/0x580
[   74.551130][ T5693]        entry_SYSCALL_64_after_hwframe+0x77/0x7f
[   74.551137][ T5693] 
[   74.551137][ T5693] -> #0 (&tty->termios_rwsem){++++}-{4:4}:
[   74.551147][ T5693]        __lock_acquire+0x1520/0x2cf0
[   74.551153][ T5693]        lock_acquire+0x106/0x350
[   74.551159][ T5693]        down_write+0x96/0x200
[   74.551166][ T5693]        n_tty_flush_buffer+0x30/0x230
[   74.551175][ T5693]        tty_buffer_flush+0x1ec/0x2b0
[   74.551183][ T5693]        tty_ldisc_flush+0x6b/0xc0
[   74.551190][ T5693]        __do_SAK+0x25e/0x680
[   74.551197][ T5693]        vc_SAK+0x78/0x220
[   74.551203][ T5693]        process_scheduled_works+0xa8e/0x14e0
[   74.551211][ T5693]        worker_thread+0x92d/0xe10
[   74.551219][ T5693]        kthread+0x388/0x470
[   74.551225][ T5693]        ret_from_fork+0x514/0xb70
[   74.551234][ T5693]        ret_from_fork_asm+0x1a/0x30
[   74.551244][ T5693] 
[   74.551244][ T5693] other info that might help us debug this:
[   74.551244][ T5693] 
[   74.551247][ T5693] Chain exists of:
[   74.551247][ T5693]   &tty->termios_rwsem --> console_lock --> &buf->lock
[   74.551247][ T5693] 
[   74.551259][ T5693]  Possible unsafe locking scenario:
[   74.551259][ T5693] 
[   74.551261][ T5693]        CPU0                    CPU1
[   74.551285][ T5693]        ----                    ----
[   74.551288][ T5693]   lock(&buf->lock);
[   74.551294][ T5693]                                lock(console_lock);
[   74.551299][ T5693]                                lock(&buf->lock);
[   74.551305][ T5693]   lock(&tty->termios_rwsem);
[   74.551310][ T5693] 
[   74.551310][ T5693]  *** DEADLOCK ***
[   74.551310][ T5693] 
[   74.551312][ T5693] 5 locks held by kworker/0:5/5693:
[   74.551316][ T5693]  #0: ffff88810006b140 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0
[   74.551336][ T5693]  #1: ffffc90003ea7c40 ((work_completion)(&vc_cons[currcons].SAK_work)){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0
[   74.551391][ T5693]  #2: ffffffff8eb55920 (console_lock){+.+.}-{0:0}, at: vc_SAK+0x28/0x220
[   74.551407][ T5693]  #3: ffff8881fafd00a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_flush+0x20/0xc0
[   74.551425][ T5693]  #4: ffff8881961b50b8 (&buf->lock){+.+.}-{4:4}, at: tty_buffer_flush+0x74/0x2b0
[   74.551443][ T5693] 
[   74.551443][ T5693] stack backtrace:
[   74.551462][ T5693] CPU: 0 UID: 0 PID: 5693 Comm: kworker/0:5 Not tainted syzkaller #1 PREEMPT(full) 
[   74.551470][ T5693] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[   74.551475][ T5693] Workqueue: events vc_SAK
[   74.551482][ T5693] Call Trace:
[   74.551486][ T5693]  <TASK>
[   74.551490][ T5693]  dump_stack_lvl+0xe8/0x150
[   74.551500][ T5693]  print_circular_bug+0x2e1/0x300
[   74.551509][ T5693]  check_noncircular+0x12e/0x150
[   74.551522][ T5693]  __lock_acquire+0x1520/0x2cf0
[   74.551529][ T5693]  ? __pfx___mutex_trylock_common+0x10/0x10
[   74.551538][ T5693]  ? rcu_is_watching+0x15/0xb0
[   74.551547][ T5693]  ? trace_contention_end+0x3d/0x140
[   74.551555][ T5693]  ? n_tty_flush_buffer+0x30/0x230
[   74.551564][ T5693]  lock_acquire+0x106/0x350
[   74.551570][ T5693]  ? n_tty_flush_buffer+0x30/0x230
[   74.551582][ T5693]  down_write+0x96/0x200
[   74.551589][ T5693]  ? n_tty_flush_buffer+0x30/0x230
[   74.551599][ T5693]  ? __pfx_down_write+0x10/0x10
[   74.551608][ T5693]  ? __pfx_n_tty_flush_buffer+0x10/0x10
[   74.551622][ T5693]  n_tty_flush_buffer+0x30/0x230
[   74.551635][ T5693]  ? tty_buffer_flush+0x1df/0x2b0
[   74.551648][ T5693]  ? __pfx_n_tty_flush_buffer+0x10/0x10
[   74.551658][ T5693]  tty_buffer_flush+0x1ec/0x2b0
[   74.551666][ T5693]  tty_ldisc_flush+0x6b/0xc0
[   74.551674][ T5693]  __do_SAK+0x25e/0x680
[   74.551683][ T5693]  ? _raw_spin_unlock_irqrestore+0x30/0x80
[   74.551694][ T5693]  vc_SAK+0x78/0x220
[   74.551700][ T5693]  ? process_scheduled_works+0xa20/0x14e0
[   74.551709][ T5693]  process_scheduled_works+0xa8e/0x14e0
[   74.551721][ T5693]  ? __pfx_process_scheduled_works+0x10/0x10
[   74.551729][ T5693]  ? do_raw_spin_lock+0x12b/0x2f0
[   74.551741][ T5693]  worker_thread+0x92d/0xe10
[   74.551751][ T5693]  ? _raw_spin_unlock_irqrestore+0x30/0x80
[   74.551763][ T5693]  kthread+0x388/0x470
[   74.551769][ T5693]  ? __pfx_worker_thread+0x10/0x10
[   74.551778][ T5693]  ? __pfx_kthread+0x10/0x10
[   74.551784][ T5693]  ret_from_fork+0x514/0xb70
[   74.551795][ T5693]  ? __pfx_ret_from_fork+0x10/0x10
[   74.551805][ T5693]  ? __switch_to+0xc89/0x1420
[   74.551814][ T5693]  ? __pfx_kthread+0x10/0x10
[   74.551820][ T5693]  ret_from_fork_asm+0x1a/0x30
[   74.551833][ T5693]  </TASK>
[   74.552445][ T5693] tty tty5: SAK: killed process 5856 (syz-executor241): by fd#3
[+] Starting reproducer...
[+] trigger_tcsets successful.
[+] Child process for SAK killed by signal 9 (expected if SAK triggered).
[-] TIOCSPTLCK failed: Inappropriate ioctl for device
[-] trigger_pty failed to open /dev/pts/0: Input/output error
[+] Reproducer finished.
[   76.613056][   T33] kauditd_printk_skb: 11 callbacks suppressed
[   76.613066][   T33] audit: type=1400 audit(1786492925.034:222): avc:  denied  { write } for  pid=5890 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   76.646560][   T33] audit: type=1400 audit(1786492925.064:223): avc:  denied  { write } for  pid=5893 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   82.069355][    T9] cfg80211: failed to load regulatory.db
 TruncatedCrashReport:======================================================
WARNING: possible circular locking dependency detected
syzkaller #1 Not tainted
------------------------------------------------------
kworker/0:5/5693 is trying to acquire lock:
ffff8881fafd02c8 (&tty->termios_rwsem){++++}-{4:4}, at: class_rwsem_write_constructor include/linux/rwsem.h:270 [inline]
ffff8881fafd02c8 (&tty->termios_rwsem){++++}-{4:4}, at: n_tty_flush_buffer+0x30/0x230 drivers/tty/n_tty.c:349

but task is already holding lock:
ffff8881961b50b8 (&buf->lock){+.+.}-{4:4}, at: tty_buffer_flush+0x74/0x2b0 drivers/tty/tty_buffer.c:236

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&buf->lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
       tty_buffer_flush+0x74/0x2b0 drivers/tty/tty_buffer.c:236
       tty_ldisc_flush+0x6b/0xc0 drivers/tty/tty_ldisc.c:388
       __do_SAK+0x25e/0x680 drivers/tty/tty_io.c:3025
       vc_SAK+0x78/0x220 drivers/tty/vt/vt_ioctl.c:994
       process_one_work kernel/workqueue.c:3322 [inline]
       process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
       worker_thread+0x92d/0xe10 kernel/workqueue.c:3486
       kthread+0x388/0x470 kernel/kthread.c:436
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #2 (console_lock){+.+.}-{0:0}:
       console_lock+0x76/0x90 kernel/printk/printk.c:2896
       uart_configure_port drivers/tty/serial/serial_core.c:2530 [inline]
       serial_core_add_one_port drivers/tty/serial/serial_core.c:3101 [inline]
       serial_core_register_port+0xc47/0x2840 drivers/tty/serial/serial_core.c:3322
       serial8250_register_8250_port+0x16b4/0x2090 drivers/tty/serial/8250/8250_core.c:828
       serial_pnp_probe+0x56a/0x7f0 drivers/tty/serial/8250/8250_pnp.c:480
       pnp_device_probe+0x30b/0x4c0 drivers/pnp/driver.c:111
       call_driver_probe drivers/base/dd.c:-1 [inline]
       really_probe+0x254/0xae0 drivers/base/dd.c:706
       __driver_probe_device+0x1e8/0x360 drivers/base/dd.c:868
       driver_probe_device+0x4f/0x240 drivers/base/dd.c:898
       __driver_attach+0x339/0x600 drivers/base/dd.c:1292
       bus_for_each_dev+0x23b/0x2c0 drivers/base/bus.c:383
       bus_add_driver+0x345/0x670 drivers/base/bus.c:763
       driver_register+0x23a/0x320 drivers/base/driver.c:174
       serial8250_init+0x8f/0x160 drivers/tty/serial/8250/8250_platform.c:317
       do_one_initcall+0x250/0x870 init/main.c:1347
       do_initcall_level+0x10a/0x1a0 init/main.c:1409
       do_initcalls+0x59/0xa0 init/main.c:1425
       kernel_init_freeable+0x29d/0x3e0 init/main.c:1658
       kernel_init+0x1d/0x1d0 init/main.c:1548
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #1 (&port->mutex){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
       class_mutex_constructor include/linux/mutex.h:253 [inline]
       uart_set_termios+0x81/0x710 drivers/tty/serial/serial_core.c:1645
       tty_set_termios+0xcaf/0x1800 drivers/tty/tty_ioctl.c:341
       set_termios+0x53d/0x6c0 drivers/tty/tty_ioctl.c:516
       tty_mode_ioctl+0x49c/0x7c0 drivers/tty/tty_ioctl.c:-1
       tty_ioctl+0x9bd/0xdd0 drivers/tty/tty_io.c:2801
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&tty->termios_rwsem){++++}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x1520/0x2cf0 kernel/locking/lockdep.c:5237
       lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
       down_write+0x96/0x200 kernel/locking/rwsem.c:1631
       class_rwsem_write_constructor include/linux/rwsem.h:270 [inline]
       n_tty_flush_buffer+0x30/0x230 drivers/tty/n_tty.c:349
       tty_buffer_flush+0x1ec/0x2b0 drivers/tty/tty_buffer.c:248
       tty_ldisc_flush+0x6b/0xc0 drivers/tty/tty_ldisc.c:388
       __do_SAK+0x25e/0x680 drivers/tty/tty_io.c:3025
       vc_SAK+0x78/0x220 drivers/tty/vt/vt_ioctl.c:994
       process_one_work kernel/workqueue.c:3322 [inline]
       process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
       worker_thread+0x92d/0xe10 kernel/workqueue.c:3486
       kthread+0x388/0x470 kernel/kthread.c:436
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

other info that might help us debug this:

Chain exists of:
  &tty->termios_rwsem --> console_lock --> &buf->lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&buf->lock);
                               lock(console_lock);
                               lock(&buf->lock);
  lock(&tty->termios_rwsem);

 *** DEADLOCK ***

5 locks held by kworker/0:5/5693:
 #0: ffff88810006b140 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3297 [inline]
 #0: ffff88810006b140 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3405
 #1: ffffc90003ea7c40 ((work_completion)(&vc_cons[currcons].SAK_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3297 [inline]
 #1: ffffc90003ea7c40 ((work_completion)(&vc_cons[currcons].SAK_work)){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3405
 #2: ffffffff8eb55920 (console_lock){+.+.}-{0:0}, at: class_console_lock_constructor include/linux/console.h:734 [inline]
 #2: ffffffff8eb55920 (console_lock){+.+.}-{0:0}, at: vc_SAK+0x28/0x220 drivers/tty/vt/vt_ioctl.c:985
 #3: ffff8881fafd00a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref drivers/tty/tty_ldisc.c:263 [inline]
 #3: ffff8881fafd00a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_flush+0x20/0xc0 drivers/tty/tty_ldisc.c:386
 #4: ffff8881961b50b8 (&buf->lock){+.+.}-{4:4}, at: tty_buffer_flush+0x74/0x2b0 drivers/tty/tty_buffer.c:236

stack backtrace:
CPU: 0 UID: 0 PID: 5693 Comm: kworker/0:5 Not tainted syzkaller #1 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: events vc_SAK
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043
 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3165 [inline]
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x1520/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
 down_write+0x96/0x200 kernel/locking/rwsem.c:1631
 class_rwsem_write_constructor include/linux/rwsem.h:270 [inline]
 n_tty_flush_buffer+0x30/0x230 drivers/tty/n_tty.c:349
 tty_buffer_flush+0x1ec/0x2b0 drivers/tty/tty_buffer.c:248
 tty_ldisc_flush+0x6b/0xc0 drivers/tty/tty_ldisc.c:388
 __do_SAK+0x25e/0x680 drivers/tty/tty_io.c:3025
 vc_SAK+0x78/0x220 drivers/tty/vt/vt_ioctl.c:994
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0x92d/0xe10 kernel/workqueue.c:3486
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
tty tty5: SAK: killed process 5856 (syz-executor241): by fd#3
 TruncatedStraceOutput:]

best-expensive

map[Feedback:The reproducer successfully triggered the circular locking dependency. Although the exact function where `&tty->termios_rwsem` is acquired differs slightly (`n_tty_flush_buffer` instead of `n_tty_receive_buf_common`), the underlying deadlock cycle is identical. Both crashes involve a task holding `&buf->lock` and attempting to acquire `&tty->termios_rwsem`, conflicting with the established dependency chain `&tty->termios_rwsem` -> `console_lock` -> `&buf->lock`. This confirms the reproducer triggers the exact same root cause. ProbePassed:false TerminalError: TitleMatches:true]

You are a security researcher with deep Linux kernel background.
Analyze the results of running the generated program.

=== CRITICAL ENVIRONMENT & TARGET CLASSIFICATION ===
Set 'TerminalError' to a descriptive error message ONLY if:
1. The execution failed due to missing hardware device nodes, subsystems, kernel modules, or privilege limits
   that cannot be loaded, created, or bypassed by user-space C code edits in the VM guest.
2. The target source files or functions described in the bug description do not exist in the checked-out codebase,
   meaning the codebase version is mismatched and the target code is absent.

=== CRITICAL PROHIBITIONS ===
- Do NOT classify a run as a terminal failure or assume a bug is fixed based on git log entries, commit titles,
  or commit messages. Reproducibility can ONLY be determined by executing reproducer candidates in the VM.
- Do NOT suggest C code strategies, repairs, or namespace bypasses when setting 'TerminalError'.


=== PHASE 2: BUG REPRODUCTION (EVALUATION) ===
The executed program was a full reproducer candidate attempting to trigger the target bug/crash.
Use this to guide your classification and feedback:
1. If a crash was triggered (Reproduced is true):
   - Determine if the triggered crash matches the expected bug.
   - If you conclude they represent the same underlying bug (the same root cause)
     despite different titles, crash signatures, or call traces, set TitleMatches
     to true and provide a detailed, technical, and verbose explanation of the
     equivalence in the 'Feedback' field.
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     set TitleMatches to false and explain the collision in 'Feedback'.
   - If they match exactly, set TitleMatches to true and provide a brief confirmation in 'Feedback'.
2. If the execution was successful (exit 0) WITHOUT a crash (Reproduced is false):
   - The reproduction attempt failed to trigger the bug. Analyze the console/strace output
     to understand why the bug did not trigger (e.g., timing, input arguments, environment setup)
     and provide feedback on how to improve the reproducer logic to trigger the crash.

Critical Diagnostic Rule for Reproduction Failures:
If the reproduction attempt fails (e.g., a system call returns an error, or a
warning/error message appears in the console log), you MUST:
1. Identify the failing system call from the execution trace or strace output.
2. Identify any corresponding warning or error messages in the console log.
3. Immediately search the kernel source tree for the warning message strings or
   the code of the failing system call/subsystem to locate the validation logic.
4. Trace the kernel's validation logic to diagnose the exact constraint violation
   or input mismatch in the generated program.
5. Provide a technical diagnosis in the feedback explaining the exact kernel constraint that was violated and why.

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Bug Description: possible deadlock in n_tty_receive_buf_common

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
kworker/u33:3/62 is trying to acquire lock:
ffff88804b3fe2c8 (&tty->termios_rwsem){++++}-{4:4}, at: class_rwsem_read_constructor include/linux/rwsem.h:259 [inline]
ffff88804b3fe2c8 (&tty->termios_rwsem){++++}-{4:4}, at: n_tty_receive_buf_common+0x85/0x1930 drivers/tty/n_tty.c:1678

but task is already holding lock:
ffff88801404a8b8 (&buf->lock){+.+.}-{4:4}, at: flush_to_ldisc+0x34/0x730 drivers/tty/tty_buffer.c:474

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&buf->lock){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       tty_buffer_flush+0x72/0x310 drivers/tty/tty_buffer.c:236
       tty_ldisc_flush+0xd2/0xf0 drivers/tty/tty_ldisc.c:388
       __do_SAK+0x368/0x480 drivers/tty/tty_io.c:3025
       vc_SAK+0x7f/0x320 drivers/tty/vt/vt_ioctl.c:994
       process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
       process_scheduled_works kernel/workqueue.c:3405 [inline]
       worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
       kthread+0x370/0x450 kernel/kthread.c:436
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #2 (console_lock){+.+.}-{0:0}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       console_lock+0x7a/0xa0 kernel/printk/printk.c:2896
       uart_configure_port drivers/tty/serial/serial_core.c:2530 [inline]
       serial_core_add_one_port drivers/tty/serial/serial_core.c:3101 [inline]
       serial_core_register_port+0xe65/0x16f0 drivers/tty/serial/serial_core.c:3322
       serial8250_register_8250_port+0x15af/0x2330 drivers/tty/serial/8250/8250_core.c:828
       serial_pnp_probe+0x436/0x930 drivers/tty/serial/8250/8250_pnp.c:480
       pnp_device_probe+0x2b3/0x4a0 drivers/pnp/driver.c:111
       call_driver_probe drivers/base/dd.c:628 [inline]
       really_probe+0x241/0xa60 drivers/base/dd.c:706
       __driver_probe_device+0x20e/0x450 drivers/base/dd.c:868
       driver_probe_device+0x4a/0x140 drivers/base/dd.c:898
       __driver_attach+0x21f/0x5b0 drivers/base/dd.c:1292
       bus_for_each_dev+0x13e/0x1d0 drivers/base/bus.c:383
       bus_add_driver+0x305/0x5b0 drivers/base/bus.c:763
       driver_register+0x1e2/0x360 drivers/base/driver.c:174
       serial8250_init+0xcc/0x1c0 drivers/tty/serial/8250/8250_platform.c:317
       do_one_initcall+0x11d/0x700 init/main.c:1347
       do_initcall_level init/main.c:1409 [inline]
       do_initcalls init/main.c:1425 [inline]
       do_basic_setup init/main.c:1445 [inline]
       kernel_init_freeable+0x6ea/0x7b0 init/main.c:1658
       kernel_init+0x1f/0x1e0 init/main.c:1548
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #1 (&port->mutex){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       class_mutex_constructor include/linux/mutex.h:253 [inline]
       uart_set_termios+0x8e/0x690 drivers/tty/serial/serial_core.c:1645
       tty_set_termios+0x64d/0x980 drivers/tty/tty_ioctl.c:341
       set_termios+0x5c8/0x880 drivers/tty/tty_ioctl.c:516
       tty_mode_ioctl+0x17e/0xd40 drivers/tty/tty_ioctl.c:803
       n_tty_ioctl_helper+0x47/0x2b0 drivers/tty/tty_ioctl.c:982
       n_tty_ioctl+0x53/0x340 drivers/tty/n_tty.c:2496
       tty_ioctl+0x11b4/0x1640 drivers/tty/tty_io.c:2801
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl fs/ioctl.c:583 [inline]
       __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x115/0x840 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&tty->termios_rwsem){++++}-{4:4}:
       check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       down_read+0x99/0x4c0 kernel/locking/rwsem.c:1574
       class_rwsem_read_constructor include/linux/rwsem.h:259 [inline]
       n_tty_receive_buf_common+0x85/0x1930 drivers/tty/n_tty.c:1678
       tty_ldisc_receive_buf+0xaa/0x1a0 drivers/tty/tty_buffer.c:394
       tty_port_default_receive_buf+0x70/0xb0 drivers/tty/tty_port.c:37
       receive_buf drivers/tty/tty_buffer.c:452 [inline]
       flush_to_ldisc+0x26b/0x730 drivers/tty/tty_buffer.c:502
       process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
       process_scheduled_works kernel/workqueue.c:3405 [inline]
       worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
       kthread+0x370/0x450 kernel/kthread.c:436
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

other info that might help us debug this:

Chain exists of:
  &tty->termios_rwsem --> console_lock --> &buf->lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&buf->lock);
                               lock(console_lock);
                               lock(&buf->lock);
  rlock(&tty->termios_rwsem);

 *** DEADLOCK ***

4 locks held by kworker/u33:3/62:
 #0: ffff88801bce4140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x12b1/0x1940 kernel/workqueue.c:3297
 #1: ffffc900009efd08 ((work_completion)(&buf->work)){+.+.}-{0:0}, at: process_one_work+0x988/0x1940 kernel/workqueue.c:3298
 #2: ffff88801404a8b8 (&buf->lock){+.+.}-{4:4}, at: flush_to_ldisc+0x34/0x730 drivers/tty/tty_buffer.c:474
 #3: ffff88804b3fe0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref+0x21/0x90 drivers/tty/tty_ldisc.c:263

stack backtrace:
CPU: 0 UID: 0 PID: 62 Comm: kworker/u33:3 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: events_unbound flush_to_ldisc
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_circular_bug.cold+0x178/0x1c7 kernel/locking/lockdep.c:2043
 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2175
 check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237
 lock_acquire kernel/locking/lockdep.c:5868 [inline]
 lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
 down_read+0x99/0x4c0 kernel/locking/rwsem.c:1574
 class_rwsem_read_constructor include/linux/rwsem.h:259 [inline]
 n_tty_receive_buf_common+0x85/0x1930 drivers/tty/n_tty.c:1678
 tty_ldisc_receive_buf+0xaa/0x1a0 drivers/tty/tty_buffer.c:394
 tty_port_default_receive_buf+0x70/0xb0 drivers/tty/tty_port.c:37
 receive_buf drivers/tty/tty_buffer.c:452 [inline]
 flush_to_ldisc+0x26b/0x730 drivers/tty/tty_buffer.c:502
 process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
 process_scheduled_works kernel/workqueue.c:3405 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

IsProbe: false
Reproduced: true
Console Output: [   70.393413][   T33] kauditd_printk_skb: 10 callbacks suppressed
[   70.393425][   T33] audit: type=1400 audit(1786492918.814:201): avc:  denied  { transition } for  pid=5830 comm="sshd-session" path="/bin/sh" dev="sda1" ino=90 scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   70.402610][   T33] audit: type=1400 audit(1786492918.814:202): avc:  denied  { noatsecure } for  pid=5830 comm="sshd-session" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   70.408936][   T33] audit: type=1400 audit(1786492918.814:203): avc:  denied  { rlimitinh } for  pid=5830 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   70.414729][   T33] audit: type=1400 audit(1786492918.814:204): avc:  denied  { siginh } for  pid=5830 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[   71.829223][ T1376] ieee802154 phy0 wpan0: encryption failed: -22
[   71.831342][ T1376] ieee802154 phy1 wpan1: encryption failed: -22
[   72.855342][   T33] audit: type=1400 audit(1786492921.274:205): avc:  denied  { write } for  pid=5832 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   72.905174][   T33] audit: type=1400 audit(1786492921.324:206): avc:  denied  { write } for  pid=5835 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   73.606571][   T33] audit: type=1400 audit(1786492922.024:207): avc:  denied  { write } for  pid=5842 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   73.660017][   T33] audit: type=1400 audit(1786492922.084:208): avc:  denied  { write } for  pid=5845 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
Warning: Permanently added '[localhost]:59174' (ED25519) to the list of known hosts.
[   74.426076][   T33] audit: type=1400 audit(1786492922.844:209): avc:  denied  { write } for  pid=5856 comm="syz-executor241" name="uinput" dev="devtmpfs" ino=924 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:event_device_t tclass=chr_file permissive=1
[   74.429762][ T5856] input: Virtual Keyboard as /devices/virtual/input/input4
[   74.435675][   T33] audit: type=1400 audit(1786492922.844:210): avc:  denied  { open } for  pid=5856 comm="syz-executor241" path="/dev/uinput" dev="devtmpfs" ino=924 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:event_device_t tclass=chr_file permissive=1
[   74.550716][ T5693] 
[   74.550723][ T5693] ======================================================
[   74.550727][ T5693] WARNING: possible circular locking dependency detected
[   74.550731][ T5693] syzkaller #1 Not tainted
[   74.550735][ T5693] ------------------------------------------------------
[   74.550738][ T5693] kworker/0:5/5693 is trying to acquire lock:
[   74.550743][ T5693] ffff8881fafd02c8 (&tty->termios_rwsem){++++}-{4:4}, at: n_tty_flush_buffer+0x30/0x230
[   74.550771][ T5693] 
[   74.550771][ T5693] but task is already holding lock:
[   74.550773][ T5693] ffff8881961b50b8 (&buf->lock){+.+.}-{4:4}, at: tty_buffer_flush+0x74/0x2b0
[   74.550791][ T5693] 
[   74.550791][ T5693] which lock already depends on the new lock.
[   74.550791][ T5693] 
[   74.550794][ T5693] 
[   74.550794][ T5693] the existing dependency chain (in reverse order) is:
[   74.550797][ T5693] 
[   74.550797][ T5693] -> #3 (&buf->lock){+.+.}-{4:4}:
[   74.550807][ T5693]        __mutex_lock+0x19d/0x1550
[   74.550815][ T5693]        tty_buffer_flush+0x74/0x2b0
[   74.550823][ T5693]        tty_ldisc_flush+0x6b/0xc0
[   74.550830][ T5693]        __do_SAK+0x25e/0x680
[   74.550838][ T5693]        vc_SAK+0x78/0x220
[   74.550844][ T5693]        process_scheduled_works+0xa8e/0x14e0
[   74.550853][ T5693]        worker_thread+0x92d/0xe10
[   74.550862][ T5693]        kthread+0x388/0x470
[   74.550868][ T5693]        ret_from_fork+0x514/0xb70
[   74.550879][ T5693]        ret_from_fork_asm+0x1a/0x30
[   74.550890][ T5693] 
[   74.550890][ T5693] -> #2 (console_lock){+.+.}-{0:0}:
[   74.550900][ T5693]        console_lock+0x76/0x90
[   74.550908][ T5693]        serial_core_register_port+0xc47/0x2840
[   74.550916][ T5693]        serial8250_register_8250_port+0x16b4/0x2090
[   74.550923][ T5693]        serial_pnp_probe+0x56a/0x7f0
[   74.550930][ T5693]        pnp_device_probe+0x30b/0x4c0
[   74.550937][ T5693]        really_probe+0x254/0xae0
[   74.550945][ T5693]        __driver_probe_device+0x1e8/0x360
[   74.550952][ T5693]        driver_probe_device+0x4f/0x240
[   74.550960][ T5693]        __driver_attach+0x339/0x600
[   74.550967][ T5693]        bus_for_each_dev+0x23b/0x2c0
[   74.550976][ T5693]        bus_add_driver+0x345/0x670
[   74.550985][ T5693]        driver_register+0x23a/0x320
[   74.550993][ T5693]        serial8250_init+0x8f/0x160
[   74.551005][ T5693]        do_one_initcall+0x250/0x870
[   74.551015][ T5693]        do_initcall_level+0x10a/0x1a0
[   74.551023][ T5693]        do_initcalls+0x59/0xa0
[   74.551028][ T5693]        kernel_init_freeable+0x29d/0x3e0
[   74.551034][ T5693]        kernel_init+0x1d/0x1d0
[   74.551043][ T5693]        ret_from_fork+0x514/0xb70
[   74.551053][ T5693]        ret_from_fork_asm+0x1a/0x30
[   74.551062][ T5693] 
[   74.551062][ T5693] -> #1 (&port->mutex){+.+.}-{4:4}:
[   74.551073][ T5693]        __mutex_lock+0x19d/0x1550
[   74.551079][ T5693]        uart_set_termios+0x81/0x710
[   74.551087][ T5693]        tty_set_termios+0xcaf/0x1800
[   74.551094][ T5693]        set_termios+0x53d/0x6c0
[   74.551100][ T5693]        tty_mode_ioctl+0x49c/0x7c0
[   74.551106][ T5693]        tty_ioctl+0x9bd/0xdd0
[   74.551113][ T5693]        __se_sys_ioctl+0xfc/0x170
[   74.551123][ T5693]        do_syscall_64+0x174/0x580
[   74.551130][ T5693]        entry_SYSCALL_64_after_hwframe+0x77/0x7f
[   74.551137][ T5693] 
[   74.551137][ T5693] -> #0 (&tty->termios_rwsem){++++}-{4:4}:
[   74.551147][ T5693]        __lock_acquire+0x1520/0x2cf0
[   74.551153][ T5693]        lock_acquire+0x106/0x350
[   74.551159][ T5693]        down_write+0x96/0x200
[   74.551166][ T5693]        n_tty_flush_buffer+0x30/0x230
[   74.551175][ T5693]        tty_buffer_flush+0x1ec/0x2b0
[   74.551183][ T5693]        tty_ldisc_flush+0x6b/0xc0
[   74.551190][ T5693]        __do_SAK+0x25e/0x680
[   74.551197][ T5693]        vc_SAK+0x78/0x220
[   74.551203][ T5693]        process_scheduled_works+0xa8e/0x14e0
[   74.551211][ T5693]        worker_thread+0x92d/0xe10
[   74.551219][ T5693]        kthread+0x388/0x470
[   74.551225][ T5693]        ret_from_fork+0x514/0xb70
[   74.551234][ T5693]        ret_from_fork_asm+0x1a/0x30
[   74.551244][ T5693] 
[   74.551244][ T5693] other info that might help us debug this:
[   74.551244][ T5693] 
[   74.551247][ T5693] Chain exists of:
[   74.551247][ T5693]   &tty->termios_rwsem --> console_lock --> &buf->lock
[   74.551247][ T5693] 
[   74.551259][ T5693]  Possible unsafe locking scenario:
[   74.551259][ T5693] 
[   74.551261][ T5693]        CPU0                    CPU1
[   74.551285][ T5693]        ----                    ----
[   74.551288][ T5693]   lock(&buf->lock);
[   74.551294][ T5693]                                lock(console_lock);
[   74.551299][ T5693]                                lock(&buf->lock);
[   74.551305][ T5693]   lock(&tty->termios_rwsem);
[   74.551310][ T5693] 
[   74.551310][ T5693]  *** DEADLOCK ***
[   74.551310][ T5693] 
[   74.551312][ T5693] 5 locks held by kworker/0:5/5693:
[   74.551316][ T5693]  #0: ffff88810006b140 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0
[   74.551336][ T5693]  #1: ffffc90003ea7c40 ((work_completion)(&vc_cons[currcons].SAK_work)){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0
[   74.551391][ T5693]  #2: ffffffff8eb55920 (console_lock){+.+.}-{0:0}, at: vc_SAK+0x28/0x220
[   74.551407][ T5693]  #3: ffff8881fafd00a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_flush+0x20/0xc0
[   74.551425][ T5693]  #4: ffff8881961b50b8 (&buf->lock){+.+.}-{4:4}, at: tty_buffer_flush+0x74/0x2b0
[   74.551443][ T5693] 
[   74.551443][ T5693] stack backtrace:
[   74.551462][ T5693] CPU: 0 UID: 0 PID: 5693 Comm: kworker/0:5 Not tainted syzkaller #1 PREEMPT(full) 
[   74.551470][ T5693] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[   74.551475][ T5693] Workqueue: events vc_SAK
[   74.551482][ T5693] Call Trace:
[   74.551486][ T5693]  <TASK>
[   74.551490][ T5693]  dump_stack_lvl+0xe8/0x150
[   74.551500][ T5693]  print_circular_bug+0x2e1/0x300
[   74.551509][ T5693]  check_noncircular+0x12e/0x150
[   74.551522][ T5693]  __lock_acquire+0x1520/0x2cf0
[   74.551529][ T5693]  ? __pfx___mutex_trylock_common+0x10/0x10
[   74.551538][ T5693]  ? rcu_is_watching+0x15/0xb0
[   74.551547][ T5693]  ? trace_contention_end+0x3d/0x140
[   74.551555][ T5693]  ? n_tty_flush_buffer+0x30/0x230
[   74.551564][ T5693]  lock_acquire+0x106/0x350
[   74.551570][ T5693]  ? n_tty_flush_buffer+0x30/0x230
[   74.551582][ T5693]  down_write+0x96/0x200
[   74.551589][ T5693]  ? n_tty_flush_buffer+0x30/0x230
[   74.551599][ T5693]  ? __pfx_down_write+0x10/0x10
[   74.551608][ T5693]  ? __pfx_n_tty_flush_buffer+0x10/0x10
[   74.551622][ T5693]  n_tty_flush_buffer+0x30/0x230
[   74.551635][ T5693]  ? tty_buffer_flush+0x1df/0x2b0
[   74.551648][ T5693]  ? __pfx_n_tty_flush_buffer+0x10/0x10
[   74.551658][ T5693]  tty_buffer_flush+0x1ec/0x2b0
[   74.551666][ T5693]  tty_ldisc_flush+0x6b/0xc0
[   74.551674][ T5693]  __do_SAK+0x25e/0x680
[   74.551683][ T5693]  ? _raw_spin_unlock_irqrestore+0x30/0x80
[   74.551694][ T5693]  vc_SAK+0x78/0x220
[   74.551700][ T5693]  ? process_scheduled_works+0xa20/0x14e0
[   74.551709][ T5693]  process_scheduled_works+0xa8e/0x14e0
[   74.551721][ T5693]  ? __pfx_process_scheduled_works+0x10/0x10
[   74.551729][ T5693]  ? do_raw_spin_lock+0x12b/0x2f0
[   74.551741][ T5693]  worker_thread+0x92d/0xe10
[   74.551751][ T5693]  ? _raw_spin_unlock_irqrestore+0x30/0x80
[   74.551763][ T5693]  kthread+0x388/0x470
[   74.551769][ T5693]  ? __pfx_worker_thread+0x10/0x10
[   74.551778][ T5693]  ? __pfx_kthread+0x10/0x10
[   74.551784][ T5693]  ret_from_fork+0x514/0xb70
[   74.551795][ T5693]  ? __pfx_ret_from_fork+0x10/0x10
[   74.551805][ T5693]  ? __switch_to+0xc89/0x1420
[   74.551814][ T5693]  ? __pfx_kthread+0x10/0x10
[   74.551820][ T5693]  ret_from_fork_asm+0x1a/0x30
[   74.551833][ T5693]  </TASK>
[   74.552445][ T5693] tty tty5: SAK: killed process 5856 (syz-executor241): by fd#3
[+] Starting reproducer...
[+] trigger_tcsets successful.
[+] Child process for SAK killed by signal 9 (expected if SAK triggered).
[-] TIOCSPTLCK failed: Inappropriate ioctl for device
[-] trigger_pty failed to open /dev/pts/0: Input/output error
[+] Reproducer finished.
[   76.613056][   T33] kauditd_printk_skb: 11 callbacks suppressed
[   76.613066][   T33] audit: type=1400 audit(1786492925.034:222): avc:  denied  { write } for  pid=5890 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   76.646560][   T33] audit: type=1400 audit(1786492925.064:223): avc:  denied  { write } for  pid=5893 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[   82.069355][    T9] cfg80211: failed to load regulatory.db

Strace Output: 
Crash Report: ======================================================
WARNING: possible circular locking dependency detected
syzkaller #1 Not tainted
------------------------------------------------------
kworker/0:5/5693 is trying to acquire lock:
ffff8881fafd02c8 (&tty->termios_rwsem){++++}-{4:4}, at: class_rwsem_write_constructor include/linux/rwsem.h:270 [inline]
ffff8881fafd02c8 (&tty->termios_rwsem){++++}-{4:4}, at: n_tty_flush_buffer+0x30/0x230 drivers/tty/n_tty.c:349

but task is already holding lock:
ffff8881961b50b8 (&buf->lock){+.+.}-{4:4}, at: tty_buffer_flush+0x74/0x2b0 drivers/tty/tty_buffer.c:236

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&buf->lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
       tty_buffer_flush+0x74/0x2b0 drivers/tty/tty_buffer.c:236
       tty_ldisc_flush+0x6b/0xc0 drivers/tty/tty_ldisc.c:388
       __do_SAK+0x25e/0x680 drivers/tty/tty_io.c:3025
       vc_SAK+0x78/0x220 drivers/tty/vt/vt_ioctl.c:994
       process_one_work kernel/workqueue.c:3322 [inline]
       process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
       worker_thread+0x92d/0xe10 kernel/workqueue.c:3486
       kthread+0x388/0x470 kernel/kthread.c:436
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #2 (console_lock){+.+.}-{0:0}:
       console_lock+0x76/0x90 kernel/printk/printk.c:2896
       uart_configure_port drivers/tty/serial/serial_core.c:2530 [inline]
       serial_core_add_one_port drivers/tty/serial/serial_core.c:3101 [inline]
       serial_core_register_port+0xc47/0x2840 drivers/tty/serial/serial_core.c:3322
       serial8250_register_8250_port+0x16b4/0x2090 drivers/tty/serial/8250/8250_core.c:828
       serial_pnp_probe+0x56a/0x7f0 drivers/tty/serial/8250/8250_pnp.c:480
       pnp_device_probe+0x30b/0x4c0 drivers/pnp/driver.c:111
       call_driver_probe drivers/base/dd.c:-1 [inline]
       really_probe+0x254/0xae0 drivers/base/dd.c:706
       __driver_probe_device+0x1e8/0x360 drivers/base/dd.c:868
       driver_probe_device+0x4f/0x240 drivers/base/dd.c:898
       __driver_attach+0x339/0x600 drivers/base/dd.c:1292
       bus_for_each_dev+0x23b/0x2c0 drivers/base/bus.c:383
       bus_add_driver+0x345/0x670 drivers/base/bus.c:763
       driver_register+0x23a/0x320 drivers/base/driver.c:174
       serial8250_init+0x8f/0x160 drivers/tty/serial/8250/8250_platform.c:317
       do_one_initcall+0x250/0x870 init/main.c:1347
       do_initcall_level+0x10a/0x1a0 init/main.c:1409
       do_initcalls+0x59/0xa0 init/main.c:1425
       kernel_init_freeable+0x29d/0x3e0 init/main.c:1658
       kernel_init+0x1d/0x1d0 init/main.c:1548
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #1 (&port->mutex){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
       class_mutex_constructor include/linux/mutex.h:253 [inline]
       uart_set_termios+0x81/0x710 drivers/tty/serial/serial_core.c:1645
       tty_set_termios+0xcaf/0x1800 drivers/tty/tty_ioctl.c:341
       set_termios+0x53d/0x6c0 drivers/tty/tty_ioctl.c:516
       tty_mode_ioctl+0x49c/0x7c0 drivers/tty/tty_ioctl.c:-1
       tty_ioctl+0x9bd/0xdd0 drivers/tty/tty_io.c:2801
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&tty->termios_rwsem){++++}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x1520/0x2cf0 kernel/locking/lockdep.c:5237
       lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
       down_write+0x96/0x200 kernel/locking/rwsem.c:1631
       class_rwsem_write_constructor include/linux/rwsem.h:270 [inline]
       n_tty_flush_buffer+0x30/0x230 drivers/tty/n_tty.c:349
       tty_buffer_flush+0x1ec/0x2b0 drivers/tty/tty_buffer.c:248
       tty_ldisc_flush+0x6b/0xc0 drivers/tty/tty_ldisc.c:388
       __do_SAK+0x25e/0x680 drivers/tty/tty_io.c:3025
       vc_SAK+0x78/0x220 drivers/tty/vt/vt_ioctl.c:994
       process_one_work kernel/workqueue.c:3322 [inline]
       process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
       worker_thread+0x92d/0xe10 kernel/workqueue.c:3486
       kthread+0x388/0x470 kernel/kthread.c:436
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

other info that might help us debug this:

Chain exists of:
  &tty->termios_rwsem --> console_lock --> &buf->lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&buf->lock);
                               lock(console_lock);
                               lock(&buf->lock);
  lock(&tty->termios_rwsem);

 *** DEADLOCK ***

5 locks held by kworker/0:5/5693:
 #0: ffff88810006b140 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3297 [inline]
 #0: ffff88810006b140 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3405
 #1: ffffc90003ea7c40 ((work_completion)(&vc_cons[currcons].SAK_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3297 [inline]
 #1: ffffc90003ea7c40 ((work_completion)(&vc_cons[currcons].SAK_work)){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3405
 #2: ffffffff8eb55920 (console_lock){+.+.}-{0:0}, at: class_console_lock_constructor include/linux/console.h:734 [inline]
 #2: ffffffff8eb55920 (console_lock){+.+.}-{0:0}, at: vc_SAK+0x28/0x220 drivers/tty/vt/vt_ioctl.c:985
 #3: ffff8881fafd00a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref drivers/tty/tty_ldisc.c:263 [inline]
 #3: ffff8881fafd00a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_flush+0x20/0xc0 drivers/tty/tty_ldisc.c:386
 #4: ffff8881961b50b8 (&buf->lock){+.+.}-{4:4}, at: tty_buffer_flush+0x74/0x2b0 drivers/tty/tty_buffer.c:236

stack backtrace:
CPU: 0 UID: 0 PID: 5693 Comm: kworker/0:5 Not tainted syzkaller #1 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: events vc_SAK
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043
 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3165 [inline]
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x1520/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
 down_write+0x96/0x200 kernel/locking/rwsem.c:1631
 class_rwsem_write_constructor include/linux/rwsem.h:270 [inline]
 n_tty_flush_buffer+0x30/0x230 drivers/tty/n_tty.c:349
 tty_buffer_flush+0x1ec/0x2b0 drivers/tty/tty_buffer.c:248
 tty_ldisc_flush+0x6b/0xc0 drivers/tty/tty_ldisc.c:388
 __do_SAK+0x25e/0x680 drivers/tty/tty_io.c:3025
 vc_SAK+0x78/0x220 drivers/tty/vt/vt_ioctl.c:994
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0x92d/0xe10 kernel/workqueue.c:3486
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
tty tty5: SAK: killed process 5856 (syz-executor241): by fd#3

gemini-3.1-pro-preview

							input: 17322
							output: 156
							thoughts: 1116
						

**My Thoughts on the Reproducer Run and Deadlock Analysis**

Here's my analysis of the reproducer run results. I've been asked to evaluate whether the bug description, "possible deadlock in n_tty_receive_buf_common," matches the output from a reproducer. I've carefully examined the crash report and compared it to the original bug description, focusing on the circular locking dependencies identified by lockdep.

**The Core Issue: A Circular Lock Dependency**

The fundamental problem, as revealed by the lockdep splat, is a circular locking dependency. Specifically, the chain appears to be:

*   `&tty->termios_rwsem`
*   `console_lock`
*   `&buf->lock`

This means a task holding one of these locks is trying to acquire another lock that is already held by a task that is, in turn, trying to acquire the first lock. This creates a deadlock scenario, where tasks are permanently blocked, waiting for each other.

**Comparing the Original Bug and the Reproduced Crash**

Let's break down how this circular dependency manifests in both scenarios:

*   **Original Bug Report:**
    *   The task was holding `&buf->lock` (at `flush_to_ldisc`).
    *   It was attempting to acquire `&tty->termios_rwsem` (at `n_tty_receive_buf_common`).
    *   The reported dependency chain was:
        *   3: `&buf->lock` acquired in `tty_buffer_flush` (called from `__do_SAK`)
        *   2: `console_lock` acquired in `serial_core_register_port`
        *   1: `&port->mutex` acquired in `uart_set_termios`
        *   0: `&tty->termios_rwsem` acquired in `n_tty_receive_buf_common`

*   **Reproducer Crash Report:**
    *   The task (kworker/0:5/5693) was holding `&buf->lock` (at `tty_buffer_flush`).
    *   It was attempting to acquire `&tty->termios_rwsem` (at `n_tty_flush_buffer`).
    *   The reported dependency chain was:
        *   3: `&buf->lock` acquired in `tty_buffer_flush` (from `__do_SAK`)
        *   2: `console_lock` acquired in `serial_core_register_port`
        *   1: `&port->mutex` acquired in `uart_set_termios`
        *   0: `&tty->termios_rwsem` acquired in `n_tty_flush_buffer`

**The Key Insight: Same Root Cause, Different Path**

I can see that the lockdep splat in the reproduced crash is, in essence, the *same* circular dependency involving `&tty->termios_rwsem`, `console_lock`, and `&buf->lock`. The only superficial difference is that the task triggering the warning is attempting to acquire `&tty->termios_rwsem` in `n_tty_flush_buffer` instead of `n_tty_receive_buf_common`.

Crucially, both scenarios are triggered by the same fundamental lock ordering issue. The code paths, while slightly different in their final function calls (`n_tty_flush_buffer` vs. `n_tty_receive_buf_common`), lead to the same deadlock.

*   The original crash was triggered by `flush_to_ldisc` holding `&buf->lock` and then calling into `n_tty_receive_buf_common` to acquire `&tty->termios_rwsem`.
*   The reproduced crash was triggered by `tty_buffer_flush` holding `&buf->lock` and then calling into `n_tty_flush_buffer` to acquire `&tty->termios_rwsem`.

Both these paths demonstrate that `&buf->lock` is being taken *before* `&tty->termios_rwsem` within the TTY buffer management code. This clashes with other parts of the system (like `uart_set_termios`) that take `&tty->termios_rwsem` first, and then proceed to acquire `console_lock` and subsequently `&buf->lock`. This creates the inevitable circular dependency.

**Conclusion: Title Matches**

Therefore, I am confident that `TitleMatches` should be `true`. The reproducer successfully triggered the same underlying bug as described in the original report: the circular locking dependency between `&buf->lock` and `&tty->termios_rwsem`. The fact that the reproducer reached a slightly different function (`n_tty_flush_buffer` vs. `n_tty_receive_buf_common`) when acquiring the second lock doesn't negate the fact that it uncovered the same root cause of the deadlock.

**Tool Parameters for `set-results`:**

*   `TitleMatches`: `true`
*   `ProbePassed`: `false` (as this isn't a probe in the sense of a minimal capability test)
*   `TerminalError`: `""` (no terminal error to report beyond the deadlock itself)
*   `Feedback`: "The reproducer successfully triggered the circular locking dependency. Although the exact function where `&tty->termios_rwsem` is acquired differs slightly (`n_tty_flush_buffer` instead of `n_tty_receive_buf_common`), the underlying deadlock cycle is identical. Both crashes involve a task holding `&buf->lock` and attempting to acquire `&tty->termios_rwsem`, conflicting with the established dependency chain `&tty->termios_rwsem` -> `console_lock` -> `&buf->lock`. This confirms the reproducer triggers the same root cause."

map[Feedback:The reproducer successfully triggered the circular locking dependency. Although the exact function where `&tty->termios_rwsem` is acquired differs slightly (`n_tty_flush_buffer` instead of `n_tty_receive_buf_common`), the underlying deadlock cycle is identical. Both crashes involve a task holding `&buf->lock` and attempting to acquire `&tty->termios_rwsem`, conflicting with the established dependency chain `&tty->termios_rwsem` -> `console_lock` -> `&buf->lock`. This confirms the reproducer triggers the exact same root cause. ProbePassed:false TerminalError: TitleMatches:true]

map[Feedback:The reproducer successfully triggered the circular locking dependency. Although the exact function where `&tty->termios_rwsem` is acquired differs slightly (`n_tty_flush_buffer` instead of `n_tty_receive_buf_common`), the underlying deadlock cycle is identical. Both crashes involve a task holding `&buf->lock` and attempting to acquire `&tty->termios_rwsem`, conflicting with the established dependency chain `&tty->termios_rwsem` -> `console_lock` -> `&buf->lock`. This confirms the reproducer triggers the exact same root cause. ProbePassed:false TerminalError: TitleMatches:true]

map[CapabilitiesVerified:true ContinueSignal: EquivalenceAnalysis:The reproducer successfully triggered the circular locking dependency. Although the exact function where `&tty->termios_rwsem` is acquired differs slightly (`n_tty_flush_buffer` instead of `n_tty_receive_buf_common`), the underlying deadlock cycle is identical. Both crashes involve a task holding `&buf->lock` and attempting to acquire `&tty->termios_rwsem`, conflicting with the established dependency chain `&tty->termios_rwsem` -> `console_lock` -> `&buf->lock`. This confirms the reproducer triggers the exact same root cause. OracleFeedback:The reproducer successfully triggered the circular locking dependency. Although the exact function where `&tty->termios_rwsem` is acquired differs slightly (`n_tty_flush_buffer` instead of `n_tty_receive_buf_common`), the underlying deadlock cycle is identical. Both crashes involve a task holding `&buf->lock` and attempting to acquire `&tty->termios_rwsem`, conflicting with the established dependency chain `&tty->termios_rwsem` -> `console_lock` -> `&buf->lock`. This confirms the reproducer triggers the exact same root cause. ReproC:#define _GNU_SOURCE
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <stdlib.h>
#include <linux/kd.h>
#include <linux/input.h>
#include <linux/uinput.h>
#include <linux/vt.h>
#include <string.h>
#include <stdio.h>
#include <sys/wait.h>
#include <errno.h>

#define TIOCSPTLCK	_IOW('T', 0x40, int)
#define TIOCGPTN	_IOR('T', 0x30, unsigned int)

void trigger_tcsets() {
    int fd_serial = open("/dev/ttyS0", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS1", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS2", O_RDWR | O_NOCTTY);
    if (fd_serial < 0) fd_serial = open("/dev/ttyS3", O_RDWR | O_NOCTTY);
    if (fd_serial >= 0) {
        struct termios term;
        if (ioctl(fd_serial, TCGETS, &term) == 0) {
            if (ioctl(fd_serial, TCSETS, &term) < 0) {
                printf("[-] TCSETS failed: %s\n", strerror(errno));
            } else {
                printf("[+] trigger_tcsets successful.\n");
            }
        } else {
            printf("[-] TCGETS failed: %s\n", strerror(errno));
        }
        close(fd_serial);
    } else {
        printf("[-] trigger_tcsets failed to open serial port: %s\n", strerror(errno));
    }
}

void trigger_sak() {
    int vt_num = 5;
    int fd_tty = open("/dev/tty5", O_RDWR | O_NOCTTY);
    if (fd_tty < 0) {
        vt_num = 0;
        fd_tty = open("/dev/tty0", O_RDWR | O_NOCTTY);
    }
    if (fd_tty < 0) {
        printf("[-] trigger_sak failed to open tty: %s\n", strerror(errno));
        exit(1);
    }
    
    if (vt_num != 0) {
        if (ioctl(fd_tty, VT_ACTIVATE, vt_num) < 0) {
            printf("[-] VT_ACTIVATE failed: %s\n", strerror(errno));
        }
        if (ioctl(fd_tty, VT_WAITACTIVE, vt_num) < 0) {
            printf("[-] VT_WAITACTIVE failed: %s\n", strerror(errno));
        }
        printf("[+] Activated /dev/tty%d.\n", vt_num);
    }

    // Map KEY_A to K_SAK across all keymaps to ensure it triggers
    for (int i = 0; i < 256; i++) {
        struct kbentry ke;
        ke.kb_table = i;
        ke.kb_index = 30; // KEY_A
        ke.kb_value = 0x020F; // K_SAK
        if (ioctl(fd_tty, KDSKBENT, &ke) < 0) {
            // Some keymaps might not exist, ignore errors
        }
    }
    printf("[+] trigger_sak mapped KEY_A to K_SAK.\n");

    int ufd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
    if (ufd >= 0) {
        if (ioctl(ufd, UI_SET_EVBIT, EV_KEY) < 0) {
            printf("[-] UI_SET_EVBIT failed: %s\n", strerror(errno));
        }
        if (ioctl(ufd, UI_SET_KEYBIT, KEY_A) < 0) {
            printf("[-] UI_SET_KEYBIT failed: %s\n", strerror(errno));
        }

        struct uinput_setup usetup;
        memset(&usetup, 0, sizeof(usetup));
        usetup.id.bustype = BUS_USB;
        usetup.id.vendor = 0x1234;
        usetup.id.product = 0x5678;
        strcpy(usetup.name, "Virtual Keyboard");
        if (ioctl(ufd, UI_DEV_SETUP, &usetup) < 0) {
            printf("[-] UI_DEV_SETUP failed: %s, falling back to uinput_user_dev\n", strerror(errno));
            struct uinput_user_dev uud;
            memset(&uud, 0, sizeof(uud));
            uud.id.bustype = BUS_USB;
            uud.id.vendor = 0x1234;
            uud.id.product = 0x5678;
            strcpy(uud.name, "Virtual Keyboard");
            if (write(ufd, &uud, sizeof(uud)) < 0) {
                printf("[-] write uinput_user_dev failed: %s\n", strerror(errno));
            }
        }
        if (ioctl(ufd, UI_DEV_CREATE) < 0) {
            printf("[-] UI_DEV_CREATE failed: %s\n", strerror(errno));
        }

        usleep(100000); // Wait for input device to be registered

        struct input_event ie;
        
        // Press KEY_A
        memset(&ie, 0, sizeof(ie));
        ie.type = EV_KEY; ie.code = KEY_A; ie.value = 1;
        if (write(ufd, &ie, sizeof(ie)) < 0) {
            printf("[-] write EV_KEY failed: %s\n", strerror(errno));
        }

        memset(&ie, 0, sizeof(ie));
        ie.type = EV_SYN; ie.code = SYN_REPORT; ie.value = 0;
        if (write(ufd, &ie, sizeof(ie)) < 0) {
            printf("[-] write EV_SYN failed: %s\n", strerror(errno));
        }

        printf("[+] trigger_sak injected KEY_A.\n");
        
        // Wait for vc_SAK workqueue to execute and kill us
        sleep(2); 
        
        // If we survive:
        ioctl(ufd, UI_DEV_DESTROY);
        close(ufd);
    } else {
        printf("[-] trigger_sak failed to open /dev/uinput: %s\n", strerror(errno));
        exit(1);
    }
    close(fd_tty);
}

void trigger_pty() {
    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);
    if (ptmx >= 0) {
        int unlock = 0;
        if (ioctl(ptmx, TIOCSPTLCK, &unlock) < 0) {
            printf("[-] TIOCSPTLCK failed: %s\n", strerror(errno));
        }
        unsigned int ptn;
        if (ioctl(ptmx, TIOCGPTN, &ptn) == 0) {
            char pts_name[32];
            snprintf(pts_name, sizeof(pts_name), "/dev/pts/%u", ptn);
            int pts = open(pts_name, O_RDWR | O_NOCTTY);
            if (pts >= 0) {
                if (write(ptmx, "a", 1) < 0) {
                    printf("[-] trigger_pty failed to write to ptmx: %s\n", strerror(errno));
                } else {
                    printf("[+] trigger_pty wrote to ptmx.\n");
                }
                usleep(100000); // Wait for flush_to_ldisc workqueue to execute
                close(pts);
            } else {
                printf("[-] trigger_pty failed to open %s: %s\n", pts_name, strerror(errno));
            }
        } else {
            printf("[-] TIOCGPTN failed: %s\n", strerror(errno));
        }
        close(ptmx);
    } else {
        printf("[-] trigger_pty failed to open /dev/ptmx: %s\n", strerror(errno));
        exit(1);
    }
}

int main(void) {
    printf("[+] Starting reproducer...\n");

    // 1. Trigger &tty->termios_rwsem -> &port->mutex
    trigger_tcsets();

    // 2. Trigger console_lock -> &buf->lock
    // Do this in a child process because __do_SAK sends SIGKILL to processes
    // associated with the active console.
    pid_t pid = fork();
    if (pid < 0) {
        printf("[-] fork failed: %s\n", strerror(errno));
        exit(1);
    }
    if (pid == 0) {
        trigger_sak();
        exit(0);
    }
    int status;
    waitpid(pid, &status, 0);
    if (WIFSIGNALED(status)) {
        printf("[+] Child process for SAK killed by signal %d (expected if SAK triggered).\n", WTERMSIG(status));
    } else {
        printf("[+] Child process for SAK exited normally.\n");
    }

    // 3. Trigger &buf->lock -> &tty->termios_rwsem
    // This completes the circular dependency and triggers the lockdep splat.
    trigger_pty();

    printf("[+] Reproducer finished.\n");
    return 0;
} Reproduced:true ReproducedBugTitle:possible deadlock in n_tty_flush_buffer ReproducedCrashReport:======================================================
WARNING: possible circular locking dependency detected
syzkaller #1 Not tainted
------------------------------------------------------
kworker/0:5/5693 is trying to acquire lock:
ffff8881fafd02c8 (&tty->termios_rwsem){++++}-{4:4}, at: class_rwsem_write_constructor include/linux/rwsem.h:270 [inline]
ffff8881fafd02c8 (&tty->termios_rwsem){++++}-{4:4}, at: n_tty_flush_buffer+0x30/0x230 drivers/tty/n_tty.c:349

but task is already holding lock:
ffff8881961b50b8 (&buf->lock){+.+.}-{4:4}, at: tty_buffer_flush+0x74/0x2b0 drivers/tty/tty_buffer.c:236

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&buf->lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
       tty_buffer_flush+0x74/0x2b0 drivers/tty/tty_buffer.c:236
       tty_ldisc_flush+0x6b/0xc0 drivers/tty/tty_ldisc.c:388
       __do_SAK+0x25e/0x680 drivers/tty/tty_io.c:3025
       vc_SAK+0x78/0x220 drivers/tty/vt/vt_ioctl.c:994
       process_one_work kernel/workqueue.c:3322 [inline]
       process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
       worker_thread+0x92d/0xe10 kernel/workqueue.c:3486
       kthread+0x388/0x470 kernel/kthread.c:436
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #2 (console_lock){+.+.}-{0:0}:
       console_lock+0x76/0x90 kernel/printk/printk.c:2896
       uart_configure_port drivers/tty/serial/serial_core.c:2530 [inline]
       serial_core_add_one_port drivers/tty/serial/serial_core.c:3101 [inline]
       serial_core_register_port+0xc47/0x2840 drivers/tty/serial/serial_core.c:3322
       serial8250_register_8250_port+0x16b4/0x2090 drivers/tty/serial/8250/8250_core.c:828
       serial_pnp_probe+0x56a/0x7f0 drivers/tty/serial/8250/8250_pnp.c:480
       pnp_device_probe+0x30b/0x4c0 drivers/pnp/driver.c:111
       call_driver_probe drivers/base/dd.c:-1 [inline]
       really_probe+0x254/0xae0 drivers/base/dd.c:706
       __driver_probe_device+0x1e8/0x360 drivers/base/dd.c:868
       driver_probe_device+0x4f/0x240 drivers/base/dd.c:898
       __driver_attach+0x339/0x600 drivers/base/dd.c:1292
       bus_for_each_dev+0x23b/0x2c0 drivers/base/bus.c:383
       bus_add_driver+0x345/0x670 drivers/base/bus.c:763
       driver_register+0x23a/0x320 drivers/base/driver.c:174
       serial8250_init+0x8f/0x160 drivers/tty/serial/8250/8250_platform.c:317
       do_one_initcall+0x250/0x870 init/main.c:1347
       do_initcall_level+0x10a/0x1a0 init/main.c:1409
       do_initcalls+0x59/0xa0 init/main.c:1425
       kernel_init_freeable+0x29d/0x3e0 init/main.c:1658
       kernel_init+0x1d/0x1d0 init/main.c:1548
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #1 (&port->mutex){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
       class_mutex_constructor include/linux/mutex.h:253 [inline]
       uart_set_termios+0x81/0x710 drivers/tty/serial/serial_core.c:1645
       tty_set_termios+0xcaf/0x1800 drivers/tty/tty_ioctl.c:341
       set_termios+0x53d/0x6c0 drivers/tty/tty_ioctl.c:516
       tty_mode_ioctl+0x49c/0x7c0 drivers/tty/tty_ioctl.c:-1
       tty_ioctl+0x9bd/0xdd0 drivers/tty/tty_io.c:2801
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&tty->termios_rwsem){++++}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x1520/0x2cf0 kernel/locking/lockdep.c:5237
       lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
       down_write+0x96/0x200 kernel/locking/rwsem.c:1631
       class_rwsem_write_constructor include/linux/rwsem.h:270 [inline]
       n_tty_flush_buffer+0x30/0x230 drivers/tty/n_tty.c:349
       tty_buffer_flush+0x1ec/0x2b0 drivers/tty/tty_buffer.c:248
       tty_ldisc_flush+0x6b/0xc0 drivers/tty/tty_ldisc.c:388
       __do_SAK+0x25e/0x680 drivers/tty/tty_io.c:3025
       vc_SAK+0x78/0x220 drivers/tty/vt/vt_ioctl.c:994
       process_one_work kernel/workqueue.c:3322 [inline]
       process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
       worker_thread+0x92d/0xe10 kernel/workqueue.c:3486
       kthread+0x388/0x470 kernel/kthread.c:436
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

other info that might help us debug this:

Chain exists of:
  &tty->termios_rwsem --> console_lock --> &buf->lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&buf->lock);
                               lock(console_lock);
                               lock(&buf->lock);
  lock(&tty->termios_rwsem);

 *** DEADLOCK ***

5 locks held by kworker/0:5/5693:
 #0: ffff88810006b140 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3297 [inline]
 #0: ffff88810006b140 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3405
 #1: ffffc90003ea7c40 ((work_completion)(&vc_cons[currcons].SAK_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3297 [inline]
 #1: ffffc90003ea7c40 ((work_completion)(&vc_cons[currcons].SAK_work)){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0 kernel/workqueue.c:3405
 #2: ffffffff8eb55920 (console_lock){+.+.}-{0:0}, at: class_console_lock_constructor include/linux/console.h:734 [inline]
 #2: ffffffff8eb55920 (console_lock){+.+.}-{0:0}, at: vc_SAK+0x28/0x220 drivers/tty/vt/vt_ioctl.c:985
 #3: ffff8881fafd00a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref drivers/tty/tty_ldisc.c:263 [inline]
 #3: ffff8881fafd00a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_flush+0x20/0xc0 drivers/tty/tty_ldisc.c:386
 #4: ffff8881961b50b8 (&buf->lock){+.+.}-{4:4}, at: tty_buffer_flush+0x74/0x2b0 drivers/tty/tty_buffer.c:236

stack backtrace:
CPU: 0 UID: 0 PID: 5693 Comm: kworker/0:5 Not tainted syzkaller #1 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: events vc_SAK
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043
 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3165 [inline]
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x1520/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
 down_write+0x96/0x200 kernel/locking/rwsem.c:1631
 class_rwsem_write_constructor include/linux/rwsem.h:270 [inline]
 n_tty_flush_buffer+0x30/0x230 drivers/tty/n_tty.c:349
 tty_buffer_flush+0x1ec/0x2b0 drivers/tty/tty_buffer.c:248
 tty_ldisc_flush+0x6b/0xc0 drivers/tty/tty_ldisc.c:388
 __do_SAK+0x25e/0x680 drivers/tty/tty_io.c:3025
 vc_SAK+0x78/0x220 drivers/tty/vt/vt_ioctl.c:994
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0x92d/0xe10 kernel/workqueue.c:3486
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
tty tty5: SAK: killed process 5856 (syz-executor241): by fd#3
]

map[]