Debian GNU/Linux 9 syzkaller ttyS0 Warning: Permanently added '10.128.1.75' (ECDSA) to the list of known hosts. syzkaller login: [ 27.597907] IPVS: ftp: loaded support on port[0] = 21 executing program [ 28.026243] [ 28.027854] ============================================ [ 28.033275] WARNING: possible recursive locking detected [ 28.038701] 4.14.290-syzkaller #0 Not tainted [ 28.043168] -------------------------------------------- [ 28.048605] swapper/1/0 is trying to acquire lock: [ 28.053505] (&port_lock_key){-.-.}, at: [] uart_write+0x109/0x560 [ 28.061385] [ 28.061385] but task is already holding lock: [ 28.067331] (&port_lock_key){-.-.}, at: [] serial8250_handle_irq.part.0+0x20/0x330 [ 28.076763] [ 28.076763] other info that might help us debug this: [ 28.083404] Possible unsafe locking scenario: [ 28.083404] [ 28.089435] CPU0 [ 28.091988] ---- [ 28.094550] lock(&port_lock_key); [ 28.098258] lock(&port_lock_key); [ 28.101858] [ 28.101858] *** DEADLOCK *** [ 28.101858] [ 28.107895] May be due to missing lock nesting notation [ 28.107895] [ 28.114797] 3 locks held by swapper/1/0: [ 28.118828] #0: (&(&i->lock)->rlock){-.-.}, at: [] serial8250_interrupt+0x3a/0x210 [ 28.128256] #1: (&port_lock_key){-.-.}, at: [] serial8250_handle_irq.part.0+0x20/0x330 [ 28.138026] #2: (&tty->ldisc_sem){++++}, at: [] tty_ldisc_ref+0x1b/0x80 [ 28.146515] [ 28.146515] stack backtrace: [ 28.151003] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.14.290-syzkaller #0 [ 28.158186] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022 [ 28.167513] Call Trace: [ 28.170069] [ 28.172196] dump_stack+0x1b2/0x281 [ 28.175816] __lock_acquire.cold+0x180/0x97c [ 28.180204] ? __lock_acquire+0x2190/0x3f20 [ 28.184503] ? trace_hardirqs_on+0x10/0x10 [ 28.188743] ? trace_hardirqs_on+0x10/0x10 [ 28.192971] ? trace_hardirqs_on+0x10/0x10 [ 28.197182] lock_acquire+0x170/0x3f0 [ 28.200961] ? uart_write+0x109/0x560 [ 28.204757] _raw_spin_lock_irqsave+0x8c/0xc0 [ 28.209226] ? uart_write+0x109/0x560 [ 28.213262] uart_write+0x109/0x560 [ 28.216863] ? n_hdlc_buf_get+0x194/0x220 [ 28.220988] ? __uart_start.isra.0+0x1b0/0x1b0 [ 28.225546] n_hdlc_send_frames+0x241/0x410 [ 28.229847] n_hdlc_tty_wakeup+0x95/0xb0 [ 28.233885] ? n_hdlc_tty_open+0x4d0/0x4d0 [ 28.238094] tty_wakeup+0xc3/0xf0 [ 28.241523] tty_port_default_wakeup+0x26/0x40 [ 28.246101] serial8250_tx_chars+0x3fe/0xc70 [ 28.250488] serial8250_handle_irq.part.0+0x28d/0x330 [ 28.255671] serial8250_default_handle_irq+0x8a/0x1f0 [ 28.260843] serial8250_interrupt+0xf3/0x210 [ 28.265229] ? rcu_lockdep_current_cpu_online+0xed/0x140 [ 28.270656] ? serial8250_backup_timeout+0x440/0x440 [ 28.275749] __handle_irq_event_percpu+0xee/0x7f0 [ 28.280568] handle_irq_event+0xed/0x240 [ 28.284608] ? handle_irq_event_percpu+0x110/0x110 [ 28.289513] handle_edge_irq+0x224/0xc40 [ 28.293551] handle_irq+0x35/0x50 [ 28.296998] do_IRQ+0x93/0x1d0 [ 28.300169] common_interrupt+0x93/0x93 [ 28.304134] [ 28.306358] RIP: 0010:_raw_spin_unlock_irq+0x50/0x80 [ 28.311436] RSP: 0018:ffff8880b5487d58 EFLAGS: 00000282 ORIG_RAX: ffffffffffffffc8 [ 28.319138] RAX: 1ffffffff11e1343 RBX: ffff8880b5478380 RCX: 0000000000000000 [ 28.326382] RDX: dffffc0000000000 RSI: 0000000000000001 RDI: ffff8880b5478c04 [ 28.333629] RBP: ffff8880ba534400 R08: ffffffff8b9a1e98 R09: 0000000000000000 [ 28.340877] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880ba534400 [ 28.348120] R13: ffff8880b54b8500 R14: ffff888097deac80 R15: ffff8880ba534d50 [ 28.355395] ? _raw_spin_unlock_irq+0x24/0x80 [ 28.359867] finish_task_switch+0x178/0x610 [ 28.364163] ? finish_task_switch+0x14d/0x610 [ 28.368633] __schedule+0x893/0x1de0 [ 28.372322] ? hrtimer_start_range_ns+0x581/0x10b0 [ 28.377228] ? io_schedule_timeout+0x140/0x140 [ 28.381786] ? trace_hardirqs_on_caller+0x3a8/0x580 [ 28.386779] schedule_idle+0x53/0x80 [ 28.390466] do_idle+0x127/0x3c0 [ 28.393809] cpu_startup_entry+0x14/0x20 [ 28.397862] start_secondary+0x4db/0x670 [ 28.401899] ? set_cpu_sibling_map+0x1680/0x1680 [ 28.406631] secondary_startup_64+0xa5/0xb0