[....] Starting enhanced syslogd: rsyslogd[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[?25l[?1c7[ ok 8[?25h[?0c. [ 28.947917] kauditd_printk_skb: 7 callbacks suppressed [ 28.947930] audit: type=1800 audit(1545659507.054:29): pid=5844 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="rc.local" dev="sda1" ino=2432 res=0 [ 28.974635] audit: type=1800 audit(1545659507.054:30): pid=5844 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="rmnologin" dev="sda1" ino=2423 res=0 Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 33.078504] sshd (5984) used greatest stack depth: 15736 bytes left Warning: Permanently added '10.128.0.63' (ECDSA) to the list of known hosts. executing program [ 563.411805] hrtimer: interrupt took 30294 ns [ 716.231878] BUG: workqueue lockup - pool cpus=1 node=0 flags=0x0 nice=0 stuck for 152s! [ 716.240543] BUG: workqueue lockup - pool cpus=1 node=0 flags=0x0 nice=-20 stuck for 147s! [ 716.248998] Showing busy workqueues and worker pools: [ 716.254408] workqueue events: flags=0x0 [ 716.258467] pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/256 [ 716.266749] pending: cache_reap [ 716.270455] [ 716.270460] ====================================================== [ 716.270464] WARNING: possible circular locking dependency detected [ 716.270466] 4.20.0 #386 Not tainted [ 716.270469] ------------------------------------------------------ [ 716.270471] swapper/0/0 is trying to acquire lock: [ 716.270473] 00000000ec31dede (console_owner){-.-.}, at: console_unlock+0x570/0x1180 [ 716.270481] [ 716.270484] but task is already holding lock: [ 716.270485] 000000005c513624 (&(&pool->lock)->rlock){-.-.}, at: show_workqueue_state.cold.50+0xad0/0x159a [ 716.270494] [ 716.270496] which lock already depends on the new lock. [ 716.270498] [ 716.270499] [ 716.270502] the existing dependency chain (in reverse order) is: [ 716.270503] [ 716.270504] -> #4 (&(&pool->lock)->rlock){-.-.}: [ 716.270512] _raw_spin_lock+0x2d/0x40 [ 716.270514] __queue_work+0x2ff/0x1440 [ 716.270517] queue_work_on+0x19a/0x1e0 [ 716.270519] put_pwq+0x175/0x1c0 [ 716.270521] put_pwq_unlocked.part.28+0x34/0x70 [ 716.270524] destroy_workqueue+0x868/0x9c0 [ 716.270526] floppy_async_init+0x1fed/0x2144 [ 716.270529] async_run_entry_fn+0x1c4/0x7f0 [ 716.270531] process_one_work+0xc90/0x1c40 [ 716.270533] worker_thread+0x17f/0x1390 [ 716.270535] kthread+0x35a/0x440 [ 716.270538] ret_from_fork+0x3a/0x50 [ 716.270539] [ 716.270540] -> #3 (&pool->lock/1){..-.}: [ 716.270549] _raw_spin_lock+0x2d/0x40 [ 716.270551] __queue_work+0x2ff/0x1440 [ 716.270553] queue_work_on+0x19a/0x1e0 [ 716.270556] tty_schedule_flip+0x14c/0x1d0 [ 716.270558] tty_flip_buffer_push+0x15/0x20 [ 716.270560] pty_write+0x19d/0x1f0 [ 716.270562] n_tty_write+0xc5b/0x11a0 [ 716.270564] tty_write+0x3f1/0x880 [ 716.270566] __vfs_write+0x119/0x9f0 [ 716.270568] vfs_write+0x1fc/0x560 [ 716.270571] ksys_write+0x101/0x260 [ 716.270573] __x64_sys_write+0x73/0xb0 [ 716.270575] do_syscall_64+0x1b9/0x820 [ 716.270578] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 716.270579] [ 716.270580] -> #2 (&(&port->lock)->rlock){-.-.}: [ 716.270588] _raw_spin_lock_irqsave+0x99/0xd0 [ 716.270590] tty_port_tty_get+0x20/0x80 [ 716.270593] tty_port_default_wakeup+0x15/0x40 [ 716.270595] tty_port_tty_wakeup+0x5d/0x70 [ 716.270597] uart_write_wakeup+0x44/0x60 [ 716.270600] serial8250_tx_chars+0x4be/0xb60 [ 716.270602] serial8250_handle_irq.part.23+0x1ee/0x280 [ 716.270605] serial8250_default_handle_irq+0xc8/0x150 [ 716.270607] serial8250_interrupt+0xef/0x190 [ 716.270610] __handle_irq_event_percpu+0x1e6/0xb00 [ 716.270613] handle_irq_event_percpu+0xa0/0x1d0 [ 716.270615] handle_irq_event+0xa7/0x135 [ 716.270617] handle_edge_irq+0x227/0x880 [ 716.270619] handle_irq+0x252/0x3d8 [ 716.270621] do_IRQ+0x98/0x1c0 [ 716.270623] ret_from_intr+0x0/0x1e [ 716.270626] _raw_spin_unlock_irqrestore+0xaf/0xd0 [ 716.270628] uart_write+0x4b2/0x740 [ 716.270630] n_tty_write+0x6c1/0x11a0 [ 716.270632] tty_write+0x3f1/0x880 [ 716.270635] redirected_tty_write+0xaf/0xc0 [ 716.270637] __vfs_write+0x119/0x9f0 [ 716.270639] vfs_write+0x1fc/0x560 [ 716.270641] ksys_write+0x101/0x260 [ 716.270643] __x64_sys_write+0x73/0xb0 [ 716.270646] do_syscall_64+0x1b9/0x820 [ 716.270650] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 716.270652] [ 716.270653] -> #1 (&port_lock_key){-.-.}: [ 716.270661] _raw_spin_lock_irqsave+0x99/0xd0 [ 716.270663] serial8250_console_write+0x8dd/0xb10 [ 716.270666] univ8250_console_write+0x5f/0x70 [ 716.270668] console_unlock+0xcd5/0x1180 [ 716.270670] vprintk_emit+0x39c/0x990 [ 716.270672] vprintk_default+0x28/0x30 [ 716.270675] vprintk_func+0x7e/0x181 [ 716.270677] printk+0xa7/0xcf [ 716.270679] register_console+0x7a5/0xbb0 [ 716.270681] univ8250_console_init+0x3f/0x4b [ 716.270684] console_init+0x6b4/0x9e7 [ 716.270686] start_kernel+0x5de/0x8fd [ 716.270688] x86_64_start_reservations+0x29/0x2b [ 716.270691] x86_64_start_kernel+0x76/0x79 [ 716.270693] secondary_startup_64+0xa4/0xb0 [ 716.270694] [ 716.270695] -> #0 (console_owner){-.-.}: [ 716.270703] lock_acquire+0x1ed/0x520 [ 716.270705] console_unlock+0x5dd/0x1180 [ 716.270707] vprintk_emit+0x39c/0x990 [ 716.270709] vprintk_default+0x28/0x30 [ 716.270712] vprintk_func+0x7e/0x181 [ 716.270714] printk+0xa7/0xcf [ 716.270717] show_workqueue_state.cold.50+0xc6c/0x159a [ 716.270719] wq_watchdog_timer_fn+0x6ea/0x810 [ 716.270721] call_timer_fn+0x272/0x920 [ 716.270724] __run_timers+0x7e5/0xc70 [ 716.270726] run_timer_softirq+0x88/0xb0 [ 716.270728] __do_softirq+0x30c/0xb2e [ 716.270730] irq_exit+0x17f/0x1c0 [ 716.270733] smp_apic_timer_interrupt+0x1cb/0x760 [ 716.270735] apic_timer_interrupt+0xf/0x20 [ 716.270738] native_safe_halt+0x6/0x10 [ 716.270740] default_idle+0xbf/0x490 [ 716.270742] arch_cpu_idle+0x10/0x20 [ 716.270744] default_idle_call+0x6d/0x90 [ 716.270746] do_idle+0x3db/0x5b0 [ 716.270749] cpu_startup_entry+0x18/0x20 [ 716.270751] rest_init+0x243/0x372 [ 716.270753] arch_call_rest_init+0xe/0x1b [ 716.270755] start_kernel+0x8c2/0x8fd [ 716.270758] x86_64_start_reservations+0x29/0x2b [ 716.270761] x86_64_start_kernel+0x76/0x79 [ 716.270763] secondary_startup_64+0xa4/0xb0 [ 716.270764] [ 716.270767] other info that might help us debug this: [ 716.270768] [ 716.270770] Chain exists of: [ 716.270771] console_owner --> &pool->lock/1 --> &(&pool->lock)->rlock [ 716.270782] [ 716.270784] Possible unsafe locking scenario: [ 716.270785] [ 716.270787] CPU0 CPU1 [ 716.270790] ---- ---- [ 716.270791] lock(&(&pool->lock)->rlock); [ 716.270796] lock(&pool->lock/1); [ 716.270802] lock(&(&pool->lock)->rlock); [ 716.270807] lock(console_owner); [ 716.270811] [ 716.270813] *** DEADLOCK *** [ 716.270814] [ 716.270816] 4 locks held by swapper/0/0: [ 716.270817] #0: 00000000a9f7b97d ((&wq_watchdog_timer)){+.-.}, at: call_timer_fn+0x1db/0x920 [ 716.270826] #1: 00000000cd7c2495 (rcu_read_lock_sched){....}, at: show_workqueue_state+0x0/0x1d0 [ 716.270836] #2: 000000005c513624 (&(&pool->lock)->rlock){-.-.}, at: show_workqueue_state.cold.50+0xad0/0x159a [ 716.270845] #3: 00000000ae2cda28 (console_lock){+.+.}, at: vprintk_emit+0x37d/0x990 [ 716.270854] [ 716.270856] stack backtrace: [ 716.270859] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.20.0 #386 [ 716.270863] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 716.270865] Call Trace: [ 716.270867] [ 716.270869] dump_stack+0x1d3/0x2c6 [ 716.270871] ? dump_stack_print_info.cold.1+0x20/0x20 [ 716.270873] ? vprintk_func+0x85/0x181 [ 716.270876] print_circular_bug.isra.33.cold.54+0x1bd/0x27d [ 716.270878] ? save_trace+0xe0/0x290 [ 716.270881] __lock_acquire+0x3360/0x4c20 [ 716.270883] ? mark_held_locks+0x130/0x130 [ 716.270885] ? kasan_check_read+0x11/0x20 [ 716.270888] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 716.270890] ? put_dec+0x3b/0xf0 [ 716.270893] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 716.270895] ? __sanitizer_cov_trace_const_cmp4+0x20/0x20 [ 716.270898] ? __sanitizer_cov_trace_const_cmp1+0x1a/0x20 [ 716.270901] ? enable_ptr_key_workfn+0x30/0x30 [ 716.270902] ? put_dec+0xf0/0xf0 [ 716.270905] ? __sanitizer_cov_trace_const_cmp8+0x18/0x20 [ 716.270907] ? vsnprintf+0x20d/0x1b60 [ 716.270909] lock_acquire+0x1ed/0x520 [ 716.270912] ? console_unlock+0x570/0x1180 [ 716.270914] ? lock_release+0xa00/0xa00 [ 716.270916] ? kasan_check_read+0x11/0x20 [ 716.270918] ? do_raw_spin_unlock+0xa7/0x330 [ 716.270921] ? do_raw_spin_trylock+0x270/0x270 [ 716.270923] ? msg_print_text+0x19a/0x1d0 [ 716.270925] console_unlock+0x5dd/0x1180 [ 716.270927] ? console_unlock+0x570/0x1180 [ 716.270930] ? devkmsg_read+0xbb0/0xbb0 [ 716.270932] ? trace_hardirqs_on+0x310/0x310 [ 716.270934] ? vprintk_emit+0x37d/0x990 [ 716.270937] ? _raw_spin_unlock_irqrestore+0x6d/0xd0 [ 716.270939] ? vprintk_emit+0x37d/0x990 [ 716.270942] ? __down_trylock_console_sem+0x155/0x200 [ 716.270944] vprintk_emit+0x39c/0x990 [ 716.270946] ? wake_up_klogd+0x180/0x180 [ 716.270948] ? graph_lock+0x270/0x270 [ 716.270950] ? print_usage_bug+0xc0/0xc0 [ 716.270952] ? up+0xea/0x1c0 [ 716.270954] ? lock_downgrade+0x900/0x900 [ 716.270957] vprintk_default+0x28/0x30 [ 716.270959] vprintk_func+0x7e/0x181 [ 716.270961] ? printk+0xa7/0xcf [ 716.270962] printk+0xa7/0xcf [ 716.270965] ? kmsg_dump_rewind_nolock+0xe4/0xe4 [ 716.270968] show_workqueue_state.cold.50+0xc6c/0x159a [ 716.270970] ? console_unlock+0x9b8/0x1180 [ 716.270973] ? print_worker_info+0x540/0x540 [ 716.270975] ? console_trylock+0x15/0xa0 [ 716.270977] ? __sanitizer_cov_trace_cmp8+0x18/0x20 [ 716.270980] ? radix_tree_next_chunk+0x5b9/0xe20 [ 716.270982] ? radix_tree_cpu_dead+0x160/0x160 [ 716.270985] ? vprintk_emit+0x297/0x990 [ 716.270987] ? graph_lock+0x270/0x270 [ 716.270989] ? wake_up_klogd+0x180/0x180 [ 716.270991] ? find_held_lock+0x36/0x1c0 [ 716.270994] ? wq_watchdog_timer_fn+0x5b4/0x810 [ 716.270996] ? lock_downgrade+0x900/0x900 [ 716.270998] ? check_preemption_disabled+0x48/0x280 [ 716.271001] ? rcu_read_unlock_special+0x1d0/0x1d0 [ 716.271003] ? kasan_check_read+0x11/0x20 [ 716.271006] ? rcu_dynticks_curr_cpu_in_eqs+0xa2/0x170 [ 716.271008] ? rcu_softirq_qs+0x20/0x20 [ 716.271010] wq_watchdog_timer_fn+0x6ea/0x810 [ 716.271013] ? mark_held_locks+0x130/0x130 [ 716.271015] ? show_workqueue_state+0x1d0/0x1d0 [ 716.271017] ? find_held_lock+0x36/0x1c0 [ 716.271019] ? graph_lock+0x270/0x270 [ 716.271022] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 716.271025] ? check_preemption_disabled+0x48/0x280 [ 716.271027] ? __lock_is_held+0xb5/0x140 [ 716.271029] call_timer_fn+0x272/0x920 [ 716.271041] ? show_workqueue_state+0x1d0/0x1d0 [ 716.271043] ? process_timeout+0x40/0x40 [ 716.271046] ? __run_timers+0x7da/0xc70 [ 716.271048] ? _raw_spin_unlock_irq+0x27/0x80 [ 716.271050] ? _raw_spin_unlock_irq+0x27/0x80 [ 716.271053] ? show_workqueue_state+0x1d0/0x1d0 [ 716.271055] ? lockdep_hardirqs_on+0x19e/0x5c0 [ 716.271057] ? trace_hardirqs_on+0xbd/0x310 [ 716.271060] ? kasan_check_read+0x11/0x20 [ 716.271062] ? __run_timers+0x7da/0xc70 [ 716.271065] ? __bpf_trace_preemptirq_template+0x30/0x30 [ 716.271067] ? show_workqueue_state+0x1d0/0x1d0 [ 716.271069] __run_timers+0x7e5/0xc70 [ 716.271072] ? __bpf_trace_timer_expire_entry+0x30/0x30 [ 716.271075] ? __sanitizer_cov_trace_const_cmp4+0x16/0x20 [ 716.271077] ? check_preemption_disabled+0x48/0x280 [ 716.271080] ? trace_hardirqs_on_thunk+0x1a/0x1 [ 716.271085] Lost 76 message(s)! [ 717.318823] workqueue events_power_efficient: flags=0x80 [ 717.324361] pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=3/256 [ 717.330499] pending: gc_worker, neigh_periodic_work, check_lifetime [ 717.337578] workqueue mm_percpu_wq: flags=0x8 [ 717.342113] pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/256 [ 717.348259] pending: vmstat_update [ 717.352215] workqueue kblockd: flags=0x18 [ 717.356345] pwq 3: cpus=1 node=0 flags=0x0 nice=-20 active=1/256 [ 717.362654] pending: blk_mq_timeout_work [ 717.367145] workqueue ipv6_addrconf: flags=0x40008 [ 717.372064] pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/1 [ 717.378030] pending: addrconf_verify_work