====================================================== WARNING: possible circular locking dependency detected 5.15.182-syzkaller #0 Not tainted ------------------------------------------------------ syz.2.1659/12374 is trying to acquire lock: ffff888028540a28 (&p->pi_lock){-.-.}-{2:2}, at: try_to_wake_up+0x5c/0x1050 kernel/sched/core.c:4030 but task is already holding lock: ffff88807daf3528 (&tty->write_wait){-.-.}-{2:2}, at: __wake_up_common_lock kernel/sched/wait.c:137 [inline] ffff88807daf3528 (&tty->write_wait){-.-.}-{2:2}, at: __wake_up+0xed/0x180 kernel/sched/wait.c:157 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #4 (&tty->write_wait){-.-.}-{2:2}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162 __wake_up_common_lock kernel/sched/wait.c:137 [inline] __wake_up+0xed/0x180 kernel/sched/wait.c:157 tty_port_default_wakeup+0xa5/0xf0 drivers/tty/tty_port.c:51 serial8250_tx_chars+0x629/0x830 drivers/tty/serial/8250/8250_port.c:1828 serial8250_handle_irq+0x519/0x610 drivers/tty/serial/8250/8250_port.c:1924 serial8250_default_handle_irq+0xb4/0x1a0 drivers/tty/serial/8250/8250_port.c:1941 serial8250_interrupt+0x9b/0x1c0 drivers/tty/serial/8250/8250_core.c:127 __handle_irq_event_percpu+0x291/0x9b0 kernel/irq/handle.c:156 handle_irq_event_percpu kernel/irq/handle.c:196 [inline] handle_irq_event+0xa5/0x220 kernel/irq/handle.c:213 handle_edge_irq+0x243/0xb20 kernel/irq/chip.c:819 generic_handle_irq_desc include/linux/irqdesc.h:158 [inline] handle_irq arch/x86/kernel/irq.c:233 [inline] __common_interrupt+0xd7/0x1e0 arch/x86/kernel/irq.c:252 common_interrupt+0xb0/0xd0 arch/x86/kernel/irq.c:242 asm_common_interrupt+0x22/0x40 arch/x86/include/asm/idtentry.h:667 native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline] arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline] default_idle+0xb/0x10 arch/x86/kernel/process.c:722 default_idle_call+0x81/0xc0 kernel/sched/idle.c:112 cpuidle_idle_call kernel/sched/idle.c:194 [inline] do_idle+0x21b/0x5b0 kernel/sched/idle.c:306 cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:403 start_kernel+0x486/0x530 init/main.c:1140 secondary_startup_64_no_verify+0xb1/0xbb -> #3 (&port_lock_key){-.-.}-{2:2}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162 serial8250_console_write+0x170/0xf80 drivers/tty/serial/8250/8250_port.c:3363 call_console_drivers kernel/printk/printk.c:-1 [inline] console_unlock+0xc86/0x1200 kernel/printk/printk.c:2744 vprintk_emit+0xc0/0x150 kernel/printk/printk.c:2274 _printk+0xcc/0x110 kernel/printk/printk.c:2299 register_console+0x682/0x960 kernel/printk/printk.c:3107 univ8250_console_init+0x41/0x50 drivers/tty/serial/8250/8250_core.c:690 console_init+0x177/0x5d0 kernel/printk/printk.c:3207 start_kernel+0x2f9/0x530 init/main.c:1076 secondary_startup_64_no_verify+0xb1/0xbb -> #2 (console_owner){-.-.}-{0:0}: console_lock_spinning_enable+0x51/0x60 kernel/printk/printk.c:1805 console_unlock+0x9f8/0x1200 kernel/printk/printk.c:2741 vprintk_emit+0xc0/0x150 kernel/printk/printk.c:2274 _printk+0xcc/0x110 kernel/printk/printk.c:2299 fail_dump lib/fault-inject.c:45 [inline] should_fail+0x36d/0x4c0 lib/fault-inject.c:146 strncpy_from_user+0x32/0x360 lib/strncpy_from_user.c:118 strncpy_from_user_nofault+0x6d/0x140 mm/maccess.c:295 bpf_probe_read_user_str_common kernel/trace/bpf_trace.c:194 [inline] ____bpf_probe_read_user_str kernel/trace/bpf_trace.c:203 [inline] bpf_probe_read_user_str+0x26/0x70 kernel/trace/bpf_trace.c:200 0xffffffffa003633d bpf_dispatcher_nop_func include/linux/bpf.h:790 [inline] __bpf_prog_run include/linux/filter.h:628 [inline] bpf_prog_run include/linux/filter.h:635 [inline] __bpf_trace_run kernel/trace/bpf_trace.c:1878 [inline] bpf_trace_run3+0x17e/0x320 kernel/trace/bpf_trace.c:1916 __traceiter_sched_switch+0x83/0xb0 include/trace/events/sched.h:220 trace_sched_switch include/trace/events/sched.h:220 [inline] __schedule+0x1d8b/0x43b0 kernel/sched/core.c:6373 preempt_schedule_irq+0xb1/0x150 kernel/sched/core.c:6780 irqentry_exit+0x63/0x70 kernel/entry/common.c:432 asm_sysvec_reschedule_ipi+0x16/0x20 arch/x86/include/asm/idtentry.h:681 vfs_write+0x89e/0xd00 fs/read_write.c:604 ksys_write+0x14d/0x250 fs/read_write.c:647 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 -> #1 (&rq->__lock){-.-.}-{2:2}: _raw_spin_lock_nested+0x2e/0x40 kernel/locking/spinlock.c:368 raw_spin_rq_lock_nested+0x26/0x140 kernel/sched/core.c:475 raw_spin_rq_lock kernel/sched/sched.h:1326 [inline] rq_lock kernel/sched/sched.h:1621 [inline] task_fork_fair+0x5c/0x350 kernel/sched/fair.c:11499 sched_cgroup_fork+0x2c6/0x320 kernel/sched/core.c:4466 copy_process+0x22bd/0x3e60 kernel/fork.c:2319 kernel_clone+0x219/0x930 kernel/fork.c:2603 kernel_thread+0xc8/0x120 kernel/fork.c:2655 rest_init+0x21/0x330 init/main.c:706 start_kernel+0x486/0x530 init/main.c:1140 secondary_startup_64_no_verify+0xb1/0xbb -> #0 (&p->pi_lock){-.-.}-{2:2}: check_prev_add kernel/locking/lockdep.c:3053 [inline] check_prevs_add kernel/locking/lockdep.c:3172 [inline] validate_chain kernel/locking/lockdep.c:3788 [inline] __lock_acquire+0x2c33/0x7c60 kernel/locking/lockdep.c:5012 lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162 try_to_wake_up+0x5c/0x1050 kernel/sched/core.c:4030 __wake_up_common+0x2a4/0x4e0 kernel/sched/wait.c:108 __wake_up_common_lock kernel/sched/wait.c:138 [inline] __wake_up+0x108/0x180 kernel/sched/wait.c:157 n_tty_read+0x1308/0x1a30 drivers/tty/n_tty.c:2259 iterate_tty_read drivers/tty/tty_io.c:868 [inline] tty_read+0x291/0x580 drivers/tty/tty_io.c:944 do_iter_readv_writev+0x497/0x600 fs/read_write.c:-1 do_iter_read+0x20b/0x7c0 fs/read_write.c:790 vfs_readv fs/read_write.c:910 [inline] do_readv+0x237/0x3e0 fs/read_write.c:947 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 other info that might help us debug this: Chain exists of: &p->pi_lock --> &port_lock_key --> &tty->write_wait Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&tty->write_wait); lock(&port_lock_key); lock(&tty->write_wait); lock(&p->pi_lock); *** DEADLOCK *** 4 locks held by syz.2.1659/12374: #0: ffff88807daf5098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:252 #1: ffffc900012082e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x5ba/0x1a30 drivers/tty/n_tty.c:2158 #2: ffff88807daf52e8 (&tty->termios_rwsem){++++}-{3:3}, at: n_tty_read+0xeb2/0x1a30 drivers/tty/n_tty.c:2227 #3: ffff88807daf3528 (&tty->write_wait){-.-.}-{2:2}, at: __wake_up_common_lock kernel/sched/wait.c:137 [inline] #3: ffff88807daf3528 (&tty->write_wait){-.-.}-{2:2}, at: __wake_up+0xed/0x180 kernel/sched/wait.c:157 stack backtrace: CPU: 1 PID: 12374 Comm: syz.2.1659 Not tainted 5.15.182-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025 Call Trace: dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106 check_noncircular+0x274/0x310 kernel/locking/lockdep.c:2133 check_prev_add kernel/locking/lockdep.c:3053 [inline] check_prevs_add kernel/locking/lockdep.c:3172 [inline] validate_chain kernel/locking/lockdep.c:3788 [inline] __lock_acquire+0x2c33/0x7c60 kernel/locking/lockdep.c:5012 lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162 try_to_wake_up+0x5c/0x1050 kernel/sched/core.c:4030 __wake_up_common+0x2a4/0x4e0 kernel/sched/wait.c:108 __wake_up_common_lock kernel/sched/wait.c:138 [inline] __wake_up+0x108/0x180 kernel/sched/wait.c:157 n_tty_read+0x1308/0x1a30 drivers/tty/n_tty.c:2259 iterate_tty_read drivers/tty/tty_io.c:868 [inline] tty_read+0x291/0x580 drivers/tty/tty_io.c:944 do_iter_readv_writev+0x497/0x600 fs/read_write.c:-1 do_iter_read+0x20b/0x7c0 fs/read_write.c:790 vfs_readv fs/read_write.c:910 [inline] do_readv+0x237/0x3e0 fs/read_write.c:947 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 RIP: 0033:0x7f1571bb4969 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f156fa1c038 EFLAGS: 00000246 ORIG_RAX: 0000000000000013 RAX: ffffffffffffffda RBX: 00007f1571ddbfa0 RCX: 00007f1571bb4969 RDX: 0000000000000004 RSI: 0000200000001500 RDI: 0000000000000003 RBP: 00007f1571c36ab1 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f1571ddbfa0 R15: 00007ffdd2d304c8