====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.0.233/5551 is trying to acquire lock: ffff88802b756358 (&p->pi_lock){-.-.}-{2:2}, at: try_to_wake_up+0x5c/0x1080 kernel/sched/core.c:4112 but task is already holding lock: ffff88807e5ca528 (&tty->write_wait){-.-.}-{2:2}, at: __wake_up_common_lock kernel/sched/wait.c:137 [inline] ffff88807e5ca528 (&tty->write_wait){-.-.}-{2:2}, at: __wake_up+0xf4/0x190 kernel/sched/wait.c:160 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+0xf4/0x190 kernel/sched/wait.c:160 tty_port_default_wakeup+0x9e/0xf0 drivers/tty/tty_port.c:71 serial8250_tx_chars+0x629/0x830 drivers/tty/serial/8250/8250_port.c:1854 serial8250_handle_irq+0x516/0x6d0 drivers/tty/serial/8250/8250_port.c:1961 serial8250_default_handle_irq+0xb4/0x1a0 drivers/tty/serial/8250/8250_port.c:1981 serial8250_interrupt+0x9b/0x1c0 drivers/tty/serial/8250/8250_core.c:126 __handle_irq_event_percpu+0x298/0xa30 kernel/irq/handle.c:158 handle_irq_event_percpu kernel/irq/handle.c:193 [inline] handle_irq_event+0x87/0x1e0 kernel/irq/handle.c:210 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:682 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:741 default_idle_call+0x84/0xc0 kernel/sched/idle.c:109 cpuidle_idle_call kernel/sched/idle.c:191 [inline] do_idle+0x1fc/0x570 kernel/sched/idle.c:303 cpu_startup_entry+0x3f/0x60 kernel/sched/idle.c:401 rest_init+0x2dc/0x300 init/main.c:745 start_kernel+0x0/0x539 init/main.c:905 start_kernel+0x490/0x539 init/main.c:1152 secondary_startup_64_no_verify+0xcf/0xdb -> #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+0x169/0x17a0 drivers/tty/serial/8250/8250_port.c:3432 call_console_driver kernel/printk/printk.c:1977 [inline] console_emit_next_record+0x947/0xc90 kernel/printk/printk.c:2777 console_flush_all kernel/printk/printk.c:-1 [inline] console_unlock+0x223/0x630 kernel/printk/printk.c:2906 vprintk_emit+0x489/0x680 kernel/printk/printk.c:2303 _printk+0xcc/0x110 kernel/printk/printk.c:2328 register_console+0x6c6/0x9c0 kernel/printk/printk.c:3269 univ8250_console_init+0x41/0x43 drivers/tty/serial/8250/8250_core.c:687 console_init+0x1bc/0x78e kernel/printk/printk.c:3359 start_kernel+0x303/0x539 init/main.c:1088 secondary_startup_64_no_verify+0xcf/0xdb -> #2 (console_owner){....}-{0:0}: console_lock_spinning_enable kernel/printk/printk.c:1818 [inline] console_emit_next_record+0x84c/0xc90 kernel/printk/printk.c:2774 console_flush_all kernel/printk/printk.c:-1 [inline] console_unlock+0x223/0x630 kernel/printk/printk.c:2906 vprintk_emit+0x489/0x680 kernel/printk/printk.c:2303 _printk+0xcc/0x110 kernel/printk/printk.c:2328 fail_dump lib/fault-inject.c:45 [inline] should_fail_ex+0x37a/0x4d0 lib/fault-inject.c:147 strncpy_from_user+0x32/0x350 lib/strncpy_from_user.c:118 strncpy_from_user_nofault+0x6d/0x140 mm/maccess.c:186 bpf_trace_copy_string kernel/bpf/helpers.c:746 [inline] bpf_bprintf_prepare+0xba0/0x13d0 kernel/bpf/helpers.c:971 ____bpf_trace_printk kernel/trace/bpf_trace.c:384 [inline] bpf_trace_printk+0xd8/0x190 kernel/trace/bpf_trace.c:374 0xffffffffa00006a1 bpf_dispatcher_nop_func include/linux/bpf.h:1012 [inline] __bpf_prog_run include/linux/filter.h:607 [inline] bpf_prog_run include/linux/filter.h:614 [inline] __bpf_trace_run kernel/trace/bpf_trace.c:2285 [inline] bpf_trace_run2+0x1cd/0x3d0 kernel/trace/bpf_trace.c:2324 trace_contention_begin+0x142/0x190 include/trace/events/lock.h:95 __pv_queued_spin_lock_slowpath+0xdc/0x9c0 kernel/locking/qspinlock.c:405 pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:591 [inline] queued_spin_lock_slowpath+0x43/0x50 arch/x86/include/asm/qspinlock.h:51 queued_spin_lock include/asm-generic/qspinlock.h:114 [inline] do_raw_spin_lock+0x217/0x280 kernel/locking/spinlock_debug.c:115 raw_spin_rq_lock_nested+0xa5/0x140 kernel/sched/core.c:546 raw_spin_rq_lock kernel/sched/sched.h:1362 [inline] rq_lock kernel/sched/sched.h:1652 [inline] __schedule+0x2ed/0x40b0 kernel/sched/core.c:6478 preempt_schedule_common+0x82/0xd0 kernel/sched/core.c:6731 preempt_schedule+0xa7/0xb0 kernel/sched/core.c:6755 preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:34 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline] _raw_spin_unlock_irqrestore+0xf6/0x100 kernel/locking/spinlock.c:194 poll_wait include/linux/poll.h:45 [inline] snd_seq_pool_poll_wait+0x59/0x140 sound/core/seq/seq_memory.c:368 snd_seq_kernel_client_write_poll+0x97/0xe0 sound/core/seq/seq_clientmgr.c:2384 snd_seq_oss_poll+0x13b/0x1c0 sound/core/seq/oss/seq_oss_rw.c:197 vfs_poll include/linux/poll.h:92 [inline] do_select+0xf6b/0x1850 fs/select.c:535 core_sys_select+0x6ad/0x8b0 fs/select.c:678 do_pselect fs/select.c:760 [inline] __do_sys_pselect6 fs/select.c:801 [inline] __se_sys_pselect6+0x2ed/0x3a0 fs/select.c:792 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x68/0xd2 -> #1 (&rq->__lock){-.-.}-{2:2}: _raw_spin_lock_nested+0x2e/0x40 kernel/locking/spinlock.c:378 raw_spin_rq_lock_nested+0x26/0x140 kernel/sched/core.c:538 raw_spin_rq_lock kernel/sched/sched.h:1362 [inline] rq_lock kernel/sched/sched.h:1652 [inline] task_fork_fair+0x5c/0x350 kernel/sched/fair.c:11928 sched_cgroup_fork+0x32c/0x3c0 kernel/sched/core.c:4686 copy_process+0x24b8/0x4020 kernel/fork.c:2464 kernel_clone+0x225/0x8b0 kernel/fork.c:2762 user_mode_thread+0xda/0x130 kernel/fork.c:2838 rest_init+0x23/0x300 init/main.c:710 start_kernel+0x0/0x539 init/main.c:905 start_kernel+0x490/0x539 init/main.c:1152 secondary_startup_64_no_verify+0xcf/0xdb -> #0 (&p->pi_lock){-.-.}-{2:2}: check_prev_add kernel/locking/lockdep.c:3090 [inline] check_prevs_add kernel/locking/lockdep.c:3209 [inline] validate_chain kernel/locking/lockdep.c:3825 [inline] __lock_acquire+0x2cf8/0x7c50 kernel/locking/lockdep.c:5049 lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662 __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/0x1080 kernel/sched/core.c:4112 __pollwake fs/select.c:205 [inline] pollwake+0x162/0x200 fs/select.c:215 __wake_up_common+0x2a4/0x4e0 kernel/sched/wait.c:107 __wake_up_common_lock kernel/sched/wait.c:138 [inline] __wake_up+0x10e/0x190 kernel/sched/wait.c:160 pty_close+0x265/0x440 drivers/tty/pty.c:68 tty_release+0x383/0x1600 drivers/tty/tty_io.c:1753 __fput+0x22c/0x920 fs/file_table.c:320 task_work_run+0x1ca/0x250 kernel/task_work.c:203 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline] syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82 entry_SYSCALL_64_after_hwframe+0x68/0xd2 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 *** 2 locks held by syz.0.233/5551: #0: ffff88807e5c81c0 (&tty->legacy_mutex){+.+.}-{3:3}, at: tty_release+0x71/0x1600 drivers/tty/tty_io.c:1735 #1: ffff88807e5ca528 (&tty->write_wait){-.-.}-{2:2}, at: __wake_up_common_lock kernel/sched/wait.c:137 [inline] #1: ffff88807e5ca528 (&tty->write_wait){-.-.}-{2:2}, at: __wake_up+0xf4/0x190 kernel/sched/wait.c:160 stack backtrace: CPU: 1 PID: 5551 Comm: syz.0.233 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Call Trace: dump_stack_lvl+0x168/0x22e lib/dump_stack.c:106 check_noncircular+0x274/0x310 kernel/locking/lockdep.c:2170 check_prev_add kernel/locking/lockdep.c:3090 [inline] check_prevs_add kernel/locking/lockdep.c:3209 [inline] validate_chain kernel/locking/lockdep.c:3825 [inline] __lock_acquire+0x2cf8/0x7c50 kernel/locking/lockdep.c:5049 lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662 __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/0x1080 kernel/sched/core.c:4112 __pollwake fs/select.c:205 [inline] pollwake+0x162/0x200 fs/select.c:215 __wake_up_common+0x2a4/0x4e0 kernel/sched/wait.c:107 __wake_up_common_lock kernel/sched/wait.c:138 [inline] __wake_up+0x10e/0x190 kernel/sched/wait.c:160 pty_close+0x265/0x440 drivers/tty/pty.c:68 tty_release+0x383/0x1600 drivers/tty/tty_io.c:1753 __fput+0x22c/0x920 fs/file_table.c:320 task_work_run+0x1ca/0x250 kernel/task_work.c:203 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline] syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82 entry_SYSCALL_64_after_hwframe+0x68/0xd2 RIP: 0033:0x7ffac058f749 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:00007fff3e18d218 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4 RAX: 0000000000000000 RBX: 00007ffac07e7da0 RCX: 00007ffac058f749 RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003 RBP: 00007ffac07e7da0 R08: 00000000000001dc R09: 0000001a3e18d50f R10: 00007ffac07e7cb0 R11: 0000000000000246 R12: 000000000004168d R13: 00007ffac07e6090 R14: ffffffffffffffff R15: 00007fff3e18d330