[ OK ] Started OpenBSD Secure Shell server. [ OK ] Reached target Multi-User System. [ OK ] Reached target Graphical Interface. Starting Update UTMP about System Runlevel Changes... [ OK ] Started Update UTMP about System Runlevel Changes. Debian GNU/Linux 9 syzkaller ttyS0 Warning: Permanently added '10.128.0.63' (ECDSA) to the list of known hosts. executing program executing program syzkaller login: [ 33.525117] [ 33.526855] ============================================ [ 33.532279] WARNING: possible recursive locking detected [ 33.537719] 4.19.211-syzkaller #0 Not tainted [ 33.542186] -------------------------------------------- [ 33.547612] swapper/1/0 is trying to acquire lock: [ 33.552514] 0000000011fc4e56 (&port_lock_key){-.-.}, at: uart_write+0x1ce/0x6f0 [ 33.559960] [ 33.559960] but task is already holding lock: [ 33.565907] 0000000011fc4e56 (&port_lock_key){-.-.}, at: serial8250_handle_irq.part.0+0x21/0x3d0 [ 33.574834] [ 33.574834] other info that might help us debug this: [ 33.581473] Possible unsafe locking scenario: [ 33.581473] [ 33.587514] CPU0 [ 33.590068] ---- [ 33.592801] lock(&port_lock_key); [ 33.596684] lock(&port_lock_key); [ 33.600291] [ 33.600291] *** DEADLOCK *** [ 33.600291] [ 33.606598] May be due to missing lock nesting notation [ 33.606598] [ 33.613538] 3 locks held by swapper/1/0: [ 33.617575] #0: 00000000f475064a (&(&i->lock)->rlock){-.-.}, at: serial8250_interrupt+0x3a/0x240 [ 33.626668] #1: 0000000011fc4e56 (&port_lock_key){-.-.}, at: serial8250_handle_irq.part.0+0x21/0x3d0 [ 33.636018] #2: 0000000045fd0db3 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref+0x1d/0x80 [ 33.644153] [ 33.644153] stack backtrace: [ 33.648637] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.19.211-syzkaller #0 [ 33.655716] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022 [ 33.665047] Call Trace: [ 33.667622] [ 33.669755] dump_stack+0x1fc/0x2ef [ 33.673366] __lock_acquire.cold+0x121/0x57e [ 33.677768] ? mark_held_locks+0xf0/0xf0 [ 33.681809] ? mark_held_locks+0xf0/0xf0 [ 33.685849] lock_acquire+0x170/0x3c0 [ 33.689628] ? uart_write+0x1ce/0x6f0 [ 33.693420] _raw_spin_lock_irqsave+0x8c/0xc0 [ 33.697889] ? uart_write+0x1ce/0x6f0 [ 33.701676] uart_write+0x1ce/0x6f0 [ 33.705293] ? lock_downgrade+0x720/0x720 [ 33.709419] ? lock_acquire+0x170/0x3c0 [ 33.713451] ? __uart_start.isra.0+0x1c0/0x1c0 [ 33.718014] ? _raw_spin_unlock_irqrestore+0x66/0xe0 [ 33.723095] ? n_hdlc_buf_get+0x1ab/0x240 [ 33.727226] ? __uart_start.isra.0+0x1c0/0x1c0 [ 33.731799] n_hdlc_send_frames+0x278/0x470 [ 33.736102] n_hdlc_tty_wakeup+0xa0/0xc0 [ 33.740156] ? n_hdlc_tty_open+0x510/0x510 [ 33.744371] tty_wakeup+0xd4/0x110 [ 33.747898] tty_port_default_wakeup+0x26/0x40 [ 33.752489] serial8250_tx_chars+0x490/0xaf0 [ 33.756894] serial8250_handle_irq.part.0+0x31f/0x3d0 [ 33.762073] serial8250_default_handle_irq+0xae/0x220 [ 33.767259] serial8250_interrupt+0x101/0x240 [ 33.771731] ? serial8250_backup_timeout+0x4d0/0x4d0 [ 33.776814] __handle_irq_event_percpu+0x27e/0x8e0 [ 33.781731] handle_irq_event+0x102/0x290 [ 33.785859] ? handle_irq_event_percpu+0x160/0x160 [ 33.790764] ? handle_edge_irq+0x29/0xcf0 [ 33.794897] handle_edge_irq+0x260/0xcf0 [ 33.798937] handle_irq+0x35/0x50 [ 33.802367] do_IRQ+0x93/0x1c0 [ 33.805551] common_interrupt+0xf/0xf [ 33.809335] [ 33.811813] RIP: 0010:native_safe_halt+0xe/0x10 [ 33.816468] Code: 48 89 df e8 f4 20 7f f9 e9 2e ff ff ff 48 89 df e8 e7 20 7f f9 eb 82 90 90 90 90 90 e9 07 00 00 00 0f 00 2d 14 43 4e 00 fb f4 90 e9 07 00 00 00 0f 00 2d 04 43 4e 00 f4 c3 90 90 41 56 41 55 [ 33.835472] RSP: 0018:ffff8880b5a9fd40 EFLAGS: 00000282 ORIG_RAX: ffffffffffffffd5 [ 33.843168] RAX: 1ffffffff13e3054 RBX: dffffc0000000000 RCX: 0000000000000000 [ 33.850436] RDX: dffffc0000000000 RSI: 0000000000000001 RDI: ffff8880b5a86c44 [ 33.857777] RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000000 [ 33.865032] R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff89f18290 [ 33.872462] R13: 1ffff11016b53fb2 R14: 0000000000000000 R15: 0000000000000000 [ 33.879813] default_idle+0x49/0x310 [ 33.883693] do_idle+0x2ec/0x4b0 [ 33.887050] ? arch_cpu_idle_exit+0x70/0x70 [ 33.891356] ? _raw_spin_unlock_irqrestore+0x79/0xe0 [ 33.896436] ? lockdep_hardirqs_on+0x3a8/0x5c0 [ 33.900998] cpu_startup_entry+0xc5/0xe0 [ 33.905061] ? cpu_in_idle+0x20/0x20 [ 33.908771] ? _raw_spin_unlock_irqrestore+0x79/0xe0 [ 33.913857] ? lockdep_hardirqs_on+0x3a8/0x5c0 [ 33.918439] start_secondary+0x435/0x5c0 [ 33.922495] ? set_cpu_sibling_map+0x17b0/0x17b0 [ 33.927289] secondary_startup_64+0xa4/0xb0