[  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 '10.128.0.104' (ECDSA) to the list of known hosts.
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syzkaller login: [   28.872130] refcount_t: underflow; use-after-free.
[   28.877460] ------------[ cut here ]------------
[   28.882211] WARNING: CPU: 1 PID: 8094 at lib/refcount.c:281 refcount_dec_not_one.cold+0x18/0x25
[   28.891020] Kernel panic - not syncing: panic_on_warn set ...
[   28.891020] 
[   28.898364] CPU: 1 PID: 8094 Comm: systemd-udevd Not tainted 4.14.284-syzkaller #0
[   28.906142] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
[   28.915483] Call Trace:
[   28.918053]  dump_stack+0x1b2/0x281
[   28.921662]  panic+0x1f9/0x42d
[   28.924831]  ? add_taint.cold+0x16/0x16
[   28.928785]  ? refcount_dec_not_one.cold+0x18/0x25
[   28.933693]  ? refcount_dec_not_one.cold+0x18/0x25
[   28.938598]  __warn.cold+0x20/0x44
[   28.942121]  ? ist_end_non_atomic+0x10/0x10
[   28.946429]  ? refcount_dec_not_one.cold+0x18/0x25
[   28.951354]  report_bug+0x208/0x250
[   28.954981]  do_error_trap+0x195/0x2d0
[   28.958848]  ? math_error+0x2d0/0x2d0
[   28.962625]  ? ___preempt_schedule+0x16/0x18
[   28.967012]  ? trace_hardirqs_off_thunk+0x1a/0x1c
[   28.971834]  invalid_op+0x1b/0x40
[   28.975273] RIP: 0010:refcount_dec_not_one.cold+0x18/0x25
[   28.980793] RSP: 0018:ffff8880b353fc38 EFLAGS: 00010286
[   28.986141] RAX: 0000000000000026 RBX: 0000000000000000 RCX: 0000000000000000
[   28.993391] RDX: 0000000000000000 RSI: ffffffff878bc800 RDI: ffffed10166a7f7d
[   29.000638] RBP: ffff8880ab40ab18 R08: 0000000000000026 R09: 0000000000000000
[   29.007888] R10: 0000000000000000 R11: 0000000000000000 R12: 00000000ffffffff
[   29.015313] R13: 0000000000000000 R14: ffffed1011c71d26 R15: ffff8880ab40ab28
[   29.022577]  ? refcount_dec_not_one.cold+0x18/0x25
[   29.027500]  ? trace_hardirqs_on_caller+0x3a8/0x580
[   29.032512]  refcount_dec_and_mutex_lock+0x1a/0x60
[   29.037427]  nbd_config_put+0x442/0x6c0
[   29.041411]  nbd_release+0xdf/0x150
[   29.045015]  ? nbd_ioctl+0xac0/0xac0
[   29.048702]  __blkdev_put+0x5aa/0x800
[   29.052485]  ? revalidate_disk+0x1f0/0x1f0
[   29.056695]  ? locks_remove_file+0x2cd/0x420
[   29.061081]  ? blkdev_put+0x75/0x4c0
[   29.064772]  ? blkdev_put+0x4c0/0x4c0
[   29.068551]  blkdev_close+0x86/0xb0
[   29.072946]  __fput+0x25f/0x7a0
[   29.076209]  task_work_run+0x11f/0x190
[   29.080087]  exit_to_usermode_loop+0x1ad/0x200
[   29.084672]  do_syscall_64+0x4a3/0x640
[   29.088546]  entry_SYSCALL_64_after_hwframe+0x46/0xbb
[   29.094772] RIP: 0033:0x7fb2b47fa270
[   29.098458] RSP: 002b:00007ffe79f8c918 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
[   29.106140] RAX: 0000000000000000 RBX: 0000000000000007 RCX: 00007fb2b47fa270
[   29.113393] RDX: 000000000aba9500 RSI: 0000000000000000 RDI: 0000000000000007
[   29.120642] RBP: 00007fb2b56b4710 R08: 0000000000000045 R09: 0000000000000018
[   29.127894] R10: 000055877e0be208 R11: 0000000000000246 R12: 0000000000000000
[   29.135144] R13: 000055877e0b06e0 R14: 0000000000000003 R15: 000000000000000e
[   29.142868] Kernel Offset: disabled
[   29.146538] Rebooting in 86400 seconds..