[....] Starting OpenBSD Secure Shell server: sshd[?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 Warning: Permanently added '10.128.0.157' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 365.043668][ T7887] block nbd0: Device being setup by another task [ 365.165649][ T7883] block nbd0: shutting down sockets [ 527.360581][ T1070] INFO: task syz-executor039:7883 blocked for more than 143 seconds. [ 527.368765][ T1070] Not tainted 5.4.0-rc4+ #0 [ 527.373869][ T1070] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 527.384067][ T1070] syz-executor039 D27984 7883 7880 0x00004004 [ 527.390436][ T1070] Call Trace: [ 527.393818][ T1070] __schedule+0x74b/0xb80 [ 527.398153][ T1070] schedule+0x131/0x1e0 [ 527.402391][ T1070] schedule_timeout+0x46/0x240 [ 527.407672][ T1070] do_wait_for_common+0x2e7/0x4d0 [ 527.415887][ T1070] ? console_conditional_schedule+0x40/0x40 [ 527.423540][ T1070] ? do_task_dead+0xc0/0xc0 [ 527.428049][ T1070] wait_for_completion+0x47/0x60 [ 527.433264][ T1070] flush_workqueue+0x60d/0x14b0 [ 527.438351][ T1070] ? __dev_printk+0x184/0x1ad [ 527.446466][ T1070] ? _dev_warn+0xb9/0xdb [ 527.451822][ T1070] nbd_ioctl+0x9d2/0xac0 [ 527.456615][ T1070] ? init_wait_entry+0xe0/0xe0 [ 527.464513][ T1070] ? nbd_release+0x120/0x120 [ 527.471807][ T1070] blkdev_ioctl+0x807/0x2980 [ 527.476403][ T1070] ? tomoyo_path_number_perm+0x53e/0x640 [ 527.482522][ T1070] block_ioctl+0xbd/0x100 [ 527.487387][ T1070] ? blkdev_iopoll+0x100/0x100 [ 527.492252][ T1070] do_vfs_ioctl+0x744/0x1730 [ 527.497505][ T1070] ? __fget+0x3f1/0x510 [ 527.502706][ T1070] ? tomoyo_file_ioctl+0x23/0x30 [ 527.507943][ T1070] ? security_file_ioctl+0xa1/0xd0 [ 527.513098][ T1070] __x64_sys_ioctl+0xe3/0x120 [ 527.518251][ T1070] do_syscall_64+0xf7/0x1c0 [ 527.523205][ T1070] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 527.529288][ T1070] RIP: 0033:0x4496e9 [ 527.533224][ T1070] Code: 00 61 64 64 69 6e 67 20 61 20 72 75 6c 65 73 65 74 2d 73 70 65 63 69 66 69 63 20 22 6d 61 69 6e 22 20 71 75 65 75 65 00 00 70 <72> 6f 63 65 73 73 42 61 74 63 68 3a 20 62 61 74 63 68 20 6f 66 20 [ 527.553395][ T1070] RSP: 002b:00007fd715da2ce8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 [ 527.565329][ T1070] RAX: ffffffffffffffda RBX: 00000000006dac48 RCX: 00000000004496e9 [ 527.574055][ T1070] RDX: 0000000000000000 RSI: 000000000000ab03 RDI: 0000000000000005 [ 527.582134][ T1070] RBP: 00000000006dac40 R08: 0000000000000000 R09: 0000000000000000 [ 527.591239][ T1070] R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dac4c [ 527.604430][ T1070] R13: 00007ffd73e6239f R14: 00007fd715da39c0 R15: 20c49ba5e353f7cf [ 527.623135][ T1070] [ 527.623135][ T1070] Showing all locks held in the system: [ 527.631291][ T1070] 1 lock held by khungtaskd/1070: [ 527.636400][ T1070] #0: ffffffff888d3f80 (rcu_read_lock){....}, at: rcu_lock_acquire+0x4/0x30 [ 527.645406][ T1070] 2 locks held by kworker/u5:0/1527: [ 527.650736][ T1070] #0: ffff88809fa37d28 ((wq_completion)knbd0-recv){+.+.}, at: process_one_work+0x75d/0x10e0 [ 527.661047][ T1070] #1: ffff8880a637fd78 ((work_completion)(&args->work)){+.+.}, at: process_one_work+0x79f/0x10e0 [ 527.671972][ T1070] 1 lock held by rsyslogd/7770: [ 527.676798][ T1070] #0: ffff8880a04f7420 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x243/0x2e0 [ 527.685729][ T1070] 2 locks held by getty/7860: [ 527.690435][ T1070] #0: ffff88809b3bd090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 [ 527.699699][ T1070] #1: ffffc90005f352e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x221/0x1b00 [ 527.709326][ T1070] 2 locks held by getty/7861: [ 527.714037][ T1070] #0: ffff888090daf090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 [ 527.723291][ T1070] #1: ffffc90005f212e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x221/0x1b00 [ 527.734701][ T1070] 2 locks held by getty/7862: [ 527.739641][ T1070] #0: ffff8880a3a20090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 [ 527.749010][ T1070] #1: ffffc90005f392e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x221/0x1b00 [ 527.758688][ T1070] 2 locks held by getty/7863: [ 527.763407][ T1070] #0: ffff8880a7bcc090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 [ 527.772741][ T1070] #1: ffffc90005f152e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x221/0x1b00 [ 527.782439][ T1070] 2 locks held by getty/7864: [ 527.787099][ T1070] #0: ffff8880a35b0090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 [ 527.797029][ T1070] #1: ffffc90005f192e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x221/0x1b00 [ 527.806623][ T1070] 2 locks held by getty/7865: [ 527.811328][ T1070] #0: ffff8880a2541090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 [ 527.829039][ T1070] #1: ffffc90005f2d2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x221/0x1b00 [ 527.843953][ T1070] 2 locks held by getty/7866: [ 527.848625][ T1070] #0: ffff88809b0f8090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x25/0x70 [ 527.857951][ T1070] #1: ffffc90005f012e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x221/0x1b00 [ 527.867552][ T1070] [ 527.869870][ T1070] ============================================= [ 527.869870][ T1070] [ 527.878307][ T1070] NMI backtrace for cpu 1 [ 527.882662][ T1070] CPU: 1 PID: 1070 Comm: khungtaskd Not tainted 5.4.0-rc4+ #0 [ 527.890293][ T1070] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 527.900340][ T1070] Call Trace: [ 527.903701][ T1070] dump_stack+0x1d8/0x2f8 [ 527.908013][ T1070] nmi_cpu_backtrace+0xaf/0x1a0 [ 527.912836][ T1070] ? nmi_trigger_cpumask_backtrace+0x16d/0x290 [ 527.918990][ T1070] ? arch_trigger_cpumask_backtrace+0x20/0x20 [ 527.925036][ T1070] nmi_trigger_cpumask_backtrace+0x174/0x290 [ 527.930988][ T1070] arch_trigger_cpumask_backtrace+0x10/0x20 [ 527.936916][ T1070] trigger_all_cpu_backtrace+0x17/0x20 [ 527.942349][ T1070] watchdog+0xbb9/0xbd0 [ 527.946480][ T1070] kthread+0x332/0x350 [ 527.950529][ T1070] ? hungtask_pm_notify+0x50/0x50 [ 527.955531][ T1070] ? kthread_blkcg+0xe0/0xe0 [ 527.960109][ T1070] ret_from_fork+0x24/0x30 [ 527.964589][ T1070] Sending NMI from CPU 1 to CPUs 0: [ 527.969923][ C0] NMI backtrace for cpu 0 skipped: idling at native_safe_halt+0xe/0x10 [ 527.970804][ T1070] Kernel panic - not syncing: hung_task: blocked tasks [ 527.985011][ T1070] CPU: 1 PID: 1070 Comm: khungtaskd Not tainted 5.4.0-rc4+ #0 [ 527.992438][ T1070] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 528.002465][ T1070] Call Trace: [ 528.005734][ T1070] dump_stack+0x1d8/0x2f8 [ 528.010082][ T1070] panic+0x264/0x7a9 [ 528.013952][ T1070] ? nmi_trigger_cpumask_backtrace+0x21a/0x290 [ 528.020098][ T1070] watchdog+0xbcc/0xbd0 [ 528.024251][ T1070] kthread+0x332/0x350 [ 528.028295][ T1070] ? hungtask_pm_notify+0x50/0x50 [ 528.033298][ T1070] ? kthread_blkcg+0xe0/0xe0 [ 528.037877][ T1070] ret_from_fork+0x24/0x30 [ 528.043753][ T1070] Kernel Offset: disabled [ 528.048077][ T1070] Rebooting in 86400 seconds..