====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ kworker/1:3/1226 is trying to acquire lock: ffff88813feba0b8 (&buf->lock){+.+.}-{4:4}, at: tty_buffer_flush+0x72/0x310 drivers/tty/tty_buffer.c:236 but task is already holding lock: ffffffff8e7d1a60 (console_lock){+.+.}-{0:0}, at: class_console_lock_constructor include/linux/console.h:736 [inline] ffffffff8e7d1a60 (console_lock){+.+.}-{0:0}, at: vc_SAK+0x13/0x320 drivers/tty/vt/vt_ioctl.c:985 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (console_lock){+.+.}-{0:0}: console_lock+0x7a/0xa0 kernel/printk/printk.c:2896 uart_configure_port drivers/tty/serial/serial_core.c:2522 [inline] serial_core_add_one_port drivers/tty/serial/serial_core.c:3086 [inline] serial_core_register_port+0xe87/0x1740 drivers/tty/serial/serial_core.c:3307 serial8250_register_8250_port+0x155a/0x2240 drivers/tty/serial/8250/8250_core.c:822 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:631 [inline] really_probe+0x241/0xa60 drivers/base/dd.c:709 __driver_probe_device+0x22e/0x480 drivers/base/dd.c:871 driver_probe_device+0x4c/0x1b0 drivers/base/dd.c:901 __driver_attach+0x21f/0x5d0 drivers/base/dd.c:1295 bus_for_each_dev+0x13e/0x1d0 drivers/base/bus.c:383 bus_add_driver+0x305/0x5b0 drivers/base/bus.c:756 driver_register+0x1e2/0x360 drivers/base/driver.c:249 serial8250_init+0xcc/0x1b0 drivers/tty/serial/8250/8250_platform.c:317 do_one_initcall+0x121/0x750 init/main.c:1392 do_initcall_level init/main.c:1454 [inline] do_initcalls init/main.c:1470 [inline] do_basic_setup init/main.c:1490 [inline] kernel_init_freeable+0x6ea/0x7b0 init/main.c:1703 kernel_init+0x1f/0x1e0 init/main.c:1593 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 (&port->mutex){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x1a4/0x1b10 kernel/locking/mutex.c:820 class_mutex_constructor include/linux/mutex.h:253 [inline] uart_set_termios+0x8e/0x6a0 drivers/tty/serial/serial_core.c:1649 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+0x53/0x350 drivers/tty/n_tty.c:2496 tty_ioctl+0x11c2/0x1640 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+0x10b/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (&tty->termios_rwsem){++++}-{4:4}: down_read+0x99/0x450 kernel/locking/rwsem.c:1568 class_rwsem_read_constructor include/linux/rwsem.h:259 [inline] n_tty_receive_buf_common+0x85/0x1950 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+0xa0e/0x1980 kernel/workqueue.c:3302 process_scheduled_works kernel/workqueue.c:3385 [inline] worker_thread+0x5ef/0xe50 kernel/workqueue.c:3466 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 -> #0 (&buf->lock){+.+.}-{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+0x14b8/0x2630 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x1b1/0x370 kernel/locking/lockdep.c:5825 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x1a4/0x1b10 kernel/locking/mutex.c:820 tty_buffer_flush+0x72/0x310 drivers/tty/tty_buffer.c:236 tty_ldisc_flush+0x68/0xf0 drivers/tty/tty_ldisc.c:388 __do_SAK+0x38f/0x4d0 drivers/tty/tty_io.c:3025 vc_SAK+0x7f/0x320 drivers/tty/vt/vt_ioctl.c:994 process_one_work+0xa0e/0x1980 kernel/workqueue.c:3302 process_scheduled_works kernel/workqueue.c:3385 [inline] worker_thread+0x5ef/0xe50 kernel/workqueue.c:3466 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: &buf->lock --> &port->mutex --> console_lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(console_lock); lock(&port->mutex); lock(console_lock); lock(&buf->lock); *** DEADLOCK *** 4 locks held by kworker/1:3/1226: #0: ffff88813fe5b140 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x12d6/0x1980 kernel/workqueue.c:3277 #1: ffffc9000592fd08 ((work_completion)(&vc_cons[currcons].SAK_work)){+.+.}-{0:0}, at: process_one_work+0x973/0x1980 kernel/workqueue.c:3278 #2: ffffffff8e7d1a60 (console_lock){+.+.}-{0:0}, at: class_console_lock_constructor include/linux/console.h:736 [inline] #2: ffffffff8e7d1a60 (console_lock){+.+.}-{0:0}, at: vc_SAK+0x13/0x320 drivers/tty/vt/vt_ioctl.c:985 #3: ffff88801df430a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref drivers/tty/tty_ldisc.c:263 [inline] #3: ffff88801df430a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_flush+0x1c/0xf0 drivers/tty/tty_ldisc.c:386 stack backtrace: CPU: 1 UID: 0 PID: 1226 Comm: kworker/1:3 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026 Workqueue: events vc_SAK Call Trace: __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 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+0x14b8/0x2630 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x1b1/0x370 kernel/locking/lockdep.c:5825 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x1a4/0x1b10 kernel/locking/mutex.c:820 tty_buffer_flush+0x72/0x310 drivers/tty/tty_buffer.c:236 tty_ldisc_flush+0x68/0xf0 drivers/tty/tty_ldisc.c:388 __do_SAK+0x38f/0x4d0 drivers/tty/tty_io.c:3025 vc_SAK+0x7f/0x320 drivers/tty/vt/vt_ioctl.c:994 process_one_work+0xa0e/0x1980 kernel/workqueue.c:3302 process_scheduled_works kernel/workqueue.c:3385 [inline] worker_thread+0x5ef/0xe50 kernel/workqueue.c:3466 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