INIT: Entering runlevel: 2 [info] Using makefile-style concurrent boot in runlevel 2. [....] 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. Debian GNU/Linux 7 syzkaller ttyS0 Warning: Permanently added '10.128.10.18' (ECDSA) to the list of known hosts. executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program syzkaller login: [ 457.768028] INFO: rcu_sched self-detected stall on CPU [ 457.773419] 1-....: (124998 ticks this GP) idle=7ba/1/4611686018427387906 softirq=9341/9341 fqs=31242 [ 457.782976] (t=125000 jiffies g=4322 c=4321 q=3) [ 457.787880] NMI backtrace for cpu 1 [ 457.791478] CPU: 1 PID: 4465 Comm: kworker/u4:30 Not tainted 4.16.0+ #10 [ 457.798285] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 457.807620] Workqueue: events_unbound flush_to_ldisc [ 457.812703] Call Trace: [ 457.815258] [ 457.817387] dump_stack+0x194/0x24d [ 457.820998] ? arch_local_irq_restore+0x53/0x53 [ 457.825655] ? lock_release+0xa40/0xa40 [ 457.829601] ? nmi_cpu_backtrace+0x1be/0x210 [ 457.833983] ? lapic_can_unplug_cpu+0xa0/0xa0 [ 457.838452] nmi_cpu_backtrace+0x1d2/0x210 [ 457.842666] ? lapic_can_unplug_cpu+0xa0/0xa0 [ 457.847132] nmi_trigger_cpumask_backtrace+0x123/0x180 [ 457.852383] arch_trigger_cpumask_backtrace+0x14/0x20 [ 457.857546] rcu_dump_cpu_stacks+0x186/0x1de [ 457.861937] check_cpu_stall.isra.61+0xbb8/0x15b0 [ 457.866754] ? rcu_lockdep_current_cpu_online+0x190/0x190 [ 457.872263] ? debug_check_no_locks_freed+0x3c0/0x3c0 [ 457.877428] ? __lock_acquire+0x664/0x3e00 [ 457.881635] ? find_held_lock+0x35/0x1d0 [ 457.885671] ? notifier_call_chain+0x136/0x2c0 [ 457.890226] ? lock_downgrade+0x980/0x980 [ 457.894346] ? trace_hardirqs_off+0x10/0x10 [ 457.898637] ? lock_release+0xa40/0xa40 [ 457.902586] ? trace_hardirqs_off+0x10/0x10 [ 457.906879] ? find_held_lock+0x35/0x1d0 [ 457.910923] ? trace_hardirqs_off+0x10/0x10 [ 457.915216] ? cpuacct_account_field+0x1e4/0x3b0 [ 457.919945] ? find_held_lock+0x35/0x1d0 [ 457.923976] ? trace_hardirqs_off+0x10/0x10 [ 457.928298] ? __lock_is_held+0xb6/0x140 [ 457.932338] rcu_check_callbacks+0x238/0xd20 [ 457.936719] ? rcu_cpu_stall_reset+0x260/0x260 [ 457.941274] ? trace_hardirqs_off+0xd/0x10 [ 457.945480] ? raise_softirq+0x325/0x490 [ 457.949512] ? raise_softirq_irqoff+0x320/0x320 [ 457.954151] ? read_boot_clock64+0x70/0x70 [ 457.958360] ? lock_downgrade+0x980/0x980 [ 457.962488] ? hrtimer_run_queues+0x5e/0x380 [ 457.966870] ? run_local_timers+0x14c/0x1b0 [ 457.971165] ? timer_clear_idle+0x50/0x50 [ 457.975284] ? account_process_tick+0xd4/0x3e0 [ 457.979840] ? thread_group_cputime+0xef0/0xef0 [ 457.984479] ? get_monotonic_coarse64+0x470/0x470 [ 457.989296] update_process_times+0x30/0x60 [ 457.993589] tick_sched_handle+0x85/0x160 [ 457.997710] tick_sched_timer+0x42/0x120 [ 458.001751] __hrtimer_run_queues+0x39c/0xec0 [ 458.006220] ? tick_sched_do_timer+0xe0/0xe0 [ 458.010611] ? hrtimer_fixup_init+0x70/0x70 [ 458.014916] ? pvclock_read_flags+0x160/0x160 [ 458.019386] ? lock_acquire+0x1d5/0x580 [ 458.023329] ? ktime_get+0x26f/0x3a0 [ 458.027021] ? kvm_clock_get_cycles+0x25/0x30 [ 458.031489] ? ktime_get_update_offsets_now+0x34a/0x520 [ 458.036824] ? do_timer+0x50/0x50 [ 458.040248] ? native_apic_msr_write+0x5c/0x80 [ 458.044802] ? rcu_idle_enter+0x530/0x530 [ 458.048921] ? lapic_next_event+0x54/0x80 [ 458.053044] hrtimer_interrupt+0x2a5/0x6f0 [ 458.057255] smp_apic_timer_interrupt+0x14a/0x700 [ 458.062079] ? smp_call_function_single_interrupt+0x124/0x640 [ 458.067934] ? smp_call_function_single_interrupt+0x640/0x640 [ 458.073788] ? _raw_spin_lock+0x32/0x40 [ 458.077737] ? _raw_spin_unlock+0x22/0x30 [ 458.081867] ? handle_edge_irq+0x2b4/0x7c0 [ 458.086076] ? task_prio+0x50/0x50 [ 458.089590] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 458.094407] apic_timer_interrupt+0xf/0x20 [ 458.098608] [ 458.100817] RIP: 0010:__process_echoes+0x62c/0x770 [ 458.105712] RSP: 0018:ffff8801b6b9f078 EFLAGS: 00000202 ORIG_RAX: ffffffffffffff12 [ 458.113393] RAX: 0000000000000000 RBX: ffffc900028b4000 RCX: ffffffff8352d4c2 [ 458.120633] RDX: 0000000000000002 RSI: 1ffff10038575a04 RDI: ffffc900028b5712 [ 458.127874] RBP: ffff8801b6b9f0e0 R08: 1ffff10036d73db5 R09: 0000000000000000 [ 458.135113] R10: 0000000000000000 R11: 0000000000000000 R12: 00000006734944b1 [ 458.142353] R13: dffffc0000000000 R14: 00000000000004b2 R15: 0000000000001d05 [ 458.149601] ? __process_echoes+0x612/0x770 [ 458.153898] ? __process_echoes+0x612/0x770 [ 458.158192] commit_echoes+0x147/0x1b0 [ 458.162056] n_tty_receive_buf_common+0x1156/0x2520 [ 458.167044] ? kfree+0x40/0x260 [ 458.170301] ? n_tty_receive_char_special+0x2c90/0x2c90 [ 458.175636] ? lock_release+0xa40/0xa40 [ 458.179581] ? free_obj_work+0x690/0x690 [ 458.183615] n_tty_receive_buf2+0x33/0x40 [ 458.187737] ? n_tty_receive_buf_common+0x2520/0x2520 [ 458.192896] tty_ldisc_receive_buf+0xa7/0x180 [ 458.197365] tty_port_default_receive_buf+0x106/0x160 [ 458.202537] ? tty_port_lower_dtr_rts+0x80/0x80 [ 458.207179] ? trace_hardirqs_on+0xd/0x10 [ 458.211302] flush_to_ldisc+0x3c4/0x590 [ 458.215249] ? tty_buffer_free+0x100/0x100 [ 458.219457] ? __lock_is_held+0xb6/0x140 [ 458.223497] process_one_work+0xc47/0x1bb0 [ 458.227702] ? debug_check_no_locks_freed+0x3c0/0x3c0 [ 458.232866] ? pwq_dec_nr_in_flight+0x450/0x450 [ 458.237510] ? __schedule+0x903/0x1ec0 [ 458.241376] ? trace_hardirqs_off+0x10/0x10 [ 458.245667] ? lock_downgrade+0x980/0x980 [ 458.249787] ? do_wait_intr_irq+0x3e0/0x3e0 [ 458.254094] ? lock_acquire+0x1d5/0x580 [ 458.258039] ? lock_acquire+0x1d5/0x580 [ 458.261982] ? worker_thread+0x4a3/0x1990 [ 458.266110] ? lock_downgrade+0x980/0x980 [ 458.270228] ? lock_release+0xa40/0xa40 [ 458.274172] ? try_to_del_timer_sync+0xe0/0x130 [ 458.278812] ? do_raw_spin_trylock+0x190/0x190 [ 458.283370] worker_thread+0x223/0x1990 [ 458.287315] ? finish_task_switch+0x1c1/0x7e0 [ 458.291789] ? process_one_work+0x1bb0/0x1bb0 [ 458.296256] ? trace_hardirqs_on_caller+0x421/0x5c0 [ 458.301244] ? trace_hardirqs_on+0xd/0x10 [ 458.305375] ? _raw_spin_unlock_irq+0x27/0x70 [ 458.309840] ? finish_task_switch+0x1c1/0x7e0 [ 458.314303] ? finish_task_switch+0x182/0x7e0 [ 458.318771] ? copy_overflow+0x20/0x20 [ 458.322633] ? __schedule+0x903/0x1ec0 [ 458.326497] ? trace_hardirqs_off+0x10/0x10 [ 458.330793] ? find_held_lock+0x35/0x1d0 [ 458.334829] ? find_held_lock+0x35/0x1d0 [ 458.338865] ? complete+0x62/0x80 [ 458.342290] ? __schedule+0x1ec0/0x1ec0 [ 458.346233] ? do_wait_intr_irq+0x3e0/0x3e0 [ 458.350524] ? __lockdep_init_map+0xe4/0x650 [ 458.354901] ? do_raw_spin_trylock+0x190/0x190 [ 458.359452] ? lockdep_init_map+0x9/0x10 [ 458.363485] ? _raw_spin_unlock_irqrestore+0x31/0xc0 [ 458.368558] ? trace_hardirqs_on_caller+0x421/0x5c0 [ 458.373545] ? trace_hardirqs_on+0xd/0x10 [ 458.377666] ? __kthread_parkme+0x176/0x240 [ 458.381960] kthread+0x33c/0x400 [ 458.385301] ? process_one_work+0x1bb0/0x1bb0 [ 458.389776] ? kthread_stop+0x7a0/0x7a0 [ 458.393726] ret_from_fork+0x3a/0x50