[ OK ] Started Getty on tty2. [ OK ] Reached target Login Prompts. [ OK ] Started OpenBSD Secure Shell server. [ OK ] Listening on Load/Save RF Kill Switch Status /dev/rfkill Watch. [ OK ] Reached target Multi-User System. [ OK ] Reached target Graphical Interface. Starting Update UTMP about System Runlevel Changes... Starting Load/Save RF Kill Switch Status... [ OK ] Started Load/Save RF Kill Switch Status. [ OK ] Started Update UTMP about System Runlevel Changes. Debian GNU/Linux 9 syzkaller ttyS0 Warning: Permanently added '10.128.0.66' (ECDSA) to the list of known hosts. executing program executing program executing program executing program executing program executing program syzkaller login: [ 33.088673] hrtimer: interrupt took 34700 ns executing program executing program executing program executing program executing program executing program [ 33.923311] [ 33.924944] ============================================ [ 33.930372] WARNING: possible recursive locking detected [ 33.935904] 4.19.211-syzkaller #0 Not tainted [ 33.940373] -------------------------------------------- [ 33.945808] swapper/1/0 is trying to acquire lock: [ 33.950722] 00000000aa437ef3 (&port_lock_key){-.-.}, at: uart_write+0x1ce/0x6f0 [ 33.958167] [ 33.958167] but task is already holding lock: [ 33.964206] 00000000aa437ef3 (&port_lock_key){-.-.}, at: serial8250_handle_irq.part.0+0x21/0x3d0 [ 33.973118] [ 33.973118] other info that might help us debug this: [ 33.979939] Possible unsafe locking scenario: [ 33.979939] [ 33.985975] CPU0 [ 33.988540] ---- [ 33.991103] lock(&port_lock_key); [ 33.994710] lock(&port_lock_key); [ 33.998670] [ 33.998670] *** DEADLOCK *** [ 33.998670] [ 34.004706] May be due to missing lock nesting notation [ 34.004706] [ 34.011613] 3 locks held by swapper/1/0: [ 34.015646] #0: 00000000c43b8c65 (&(&i->lock)->rlock){-.-.}, at: serial8250_interrupt+0x3a/0x240 [ 34.024645] #1: 00000000aa437ef3 (&port_lock_key){-.-.}, at: serial8250_handle_irq.part.0+0x21/0x3d0 [ 34.034004] #2: 000000007a2c7520 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref+0x1d/0x80 [ 34.042581] [ 34.042581] stack backtrace: [ 34.047149] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.19.211-syzkaller #0 [ 34.054224] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022 [ 34.063567] Call Trace: [ 34.066132] [ 34.068264] dump_stack+0x1fc/0x2ef [ 34.071870] __lock_acquire.cold+0x121/0x57e [ 34.076262] ? mark_held_locks+0xf0/0xf0 [ 34.080303] ? mark_held_locks+0xf0/0xf0 [ 34.084360] lock_acquire+0x170/0x3c0 [ 34.088163] ? uart_write+0x1ce/0x6f0 [ 34.091955] _raw_spin_lock_irqsave+0x8c/0xc0 [ 34.096436] ? uart_write+0x1ce/0x6f0 [ 34.100225] uart_write+0x1ce/0x6f0 [ 34.103832] ? lock_downgrade+0x720/0x720 [ 34.107967] ? lock_acquire+0x170/0x3c0 [ 34.111921] ? __uart_start.isra.0+0x1c0/0x1c0 [ 34.116484] ? _raw_spin_unlock_irqrestore+0x66/0xe0 [ 34.122786] ? n_hdlc_buf_get+0x1ab/0x240 [ 34.126928] ? __uart_start.isra.0+0x1c0/0x1c0 [ 34.131500] n_hdlc_send_frames+0x278/0x470 [ 34.135824] n_hdlc_tty_wakeup+0xa0/0xc0 [ 34.139883] ? n_hdlc_tty_open+0x510/0x510 [ 34.144103] tty_wakeup+0xd4/0x110 [ 34.147634] tty_port_default_wakeup+0x26/0x40 [ 34.152205] serial8250_tx_chars+0x490/0xaf0 [ 34.156614] serial8250_handle_irq.part.0+0x31f/0x3d0 [ 34.161790] serial8250_default_handle_irq+0xae/0x220 [ 34.166967] serial8250_interrupt+0x101/0x240 [ 34.171443] ? serial8250_backup_timeout+0x4d0/0x4d0 [ 34.176527] __handle_irq_event_percpu+0x27e/0x8e0 [ 34.181436] handle_irq_event+0x102/0x290 [ 34.185563] ? handle_irq_event_percpu+0x160/0x160 [ 34.190473] ? handle_edge_irq+0x29/0xcf0 [ 34.194670] handle_edge_irq+0x260/0xcf0 [ 34.198720] handle_irq+0x35/0x50 [ 34.202157] do_IRQ+0x93/0x1c0 [ 34.205339] common_interrupt+0xf/0xf [ 34.209136] [ 34.211358] RIP: 0010:native_safe_halt+0xe/0x10 [ 34.216182] 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 [ 34.235065] RSP: 0018:ffff8880b5a9fd40 EFLAGS: 00000282 ORIG_RAX: ffffffffffffffd2 [ 34.242772] RAX: 1ffffffff13e3054 RBX: dffffc0000000000 RCX: 0000000000000000 [ 34.250033] RDX: dffffc0000000000 RSI: 0000000000000001 RDI: ffff8880b5a86c44 [ 34.257305] RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000000 [ 34.264559] R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff89f18290 [ 34.271807] R13: 1ffff11016b53fb2 R14: 0000000000000000 R15: 0000000000000000 [ 34.279068] default_idle+0x49/0x310 [ 34.282850] do_idle+0x2ec/0x4b0 [ 34.286198] ? arch_cpu_idle_exit+0x70/0x70 [ 34.290504] ? _raw_spin_unlock_irqrestore+0x79/0xe0 [ 34.295676] ? lockdep_hardirqs_on+0x3a8/0x5c0 [ 34.300244] cpu_startup_entry+0xc5/0xe0 [ 34.304284] ? cpu_in_idle+0x20/0x20 [ 34.307977] ? _raw_spin_unlock_irqrestore+0x79/0xe0 [ 34.313065] ? lockdep_hardirqs_on+0x3a8/0x5c0 [ 34.317747] start_secondary+0x435/0x5c0 [ 34.321814] ? set_cpu_sibling_map+0x17b0/0x17b0 [ 34.326554] secondary_startup_64+0xa4/0xb0