[  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 '10.128.0.242' (ECDSA) to the list of known hosts.
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syzkaller login: [   29.771872] refcount_t: underflow; use-after-free.
[   29.777196] ------------[ cut here ]------------
[   29.781945] WARNING: CPU: 1 PID: 8118 at lib/refcount.c:281 refcount_dec_not_one.cold+0x18/0x25
[   29.790755] Kernel panic - not syncing: panic_on_warn set ...
[   29.790755] 
[   29.798095] CPU: 1 PID: 8118 Comm: systemd-udevd Not tainted 4.14.223-syzkaller #0
[   29.805775] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
[   29.815120] Call Trace:
[   29.817689]  dump_stack+0x1b2/0x281
[   29.821313]  panic+0x1f9/0x42d
[   29.824482]  ? add_taint.cold+0x16/0x16
[   29.828453]  ? refcount_dec_not_one.cold+0x18/0x25
[   29.833362]  ? refcount_dec_not_one.cold+0x18/0x25
[   29.838271]  __warn.cold+0x20/0x44
[   29.841789]  ? ist_end_non_atomic+0x10/0x10
[   29.846095]  ? refcount_dec_not_one.cold+0x18/0x25
[   29.851011]  report_bug+0x208/0x250
[   29.854616]  do_error_trap+0x195/0x2d0
[   29.858482]  ? math_error+0x2d0/0x2d0
[   29.862366]  ? ___preempt_schedule+0x16/0x18
[   29.866753]  ? trace_hardirqs_off_thunk+0x1a/0x1c
[   29.871592]  invalid_op+0x1b/0x40
[   29.875025] RIP: 0010:refcount_dec_not_one.cold+0x18/0x25
[   29.880550] RSP: 0018:ffff8880b045fc38 EFLAGS: 00010286
[   29.885893] RAX: 0000000000000026 RBX: 0000000000000000 RCX: 0000000000000000
[   29.893142] RDX: 0000000000000000 RSI: ffffffff878bbb80 RDI: ffffed101608bf7d
[   29.900388] RBP: ffff8880b3349158 R08: 0000000000000026 R09: 0000000000000000
[   29.907634] R10: 0000000000000000 R11: 0000000000000000 R12: 00000000ffffffff
[   29.914898] R13: 0000000000000000 R14: ffffed1011c7832e R15: ffff8880b3349168
[   29.922167]  ? refcount_dec_not_one.cold+0x18/0x25
[   29.927077]  ? trace_hardirqs_on_caller+0x3a8/0x580
[   29.932681]  refcount_dec_and_mutex_lock+0x1a/0x60
[   29.937589]  nbd_config_put+0x506/0x810
[   29.941544]  nbd_release+0xdf/0x150
[   29.945164]  ? nbd_queue_rq+0xc50/0xc50
[   29.949114]  __blkdev_put+0x5aa/0x800
[   29.952941]  ? revalidate_disk+0x1f0/0x1f0
[   29.957197]  ? locks_remove_file+0x2cd/0x420
[   29.961582]  ? blkdev_put+0x75/0x4c0
[   29.965276]  ? blkdev_put+0x4c0/0x4c0
[   29.969053]  blkdev_close+0x86/0xb0
[   29.972677]  __fput+0x25f/0x7a0
[   29.975947]  task_work_run+0x11f/0x190
[   29.979871]  exit_to_usermode_loop+0x1ad/0x200
[   29.984466]  do_syscall_64+0x4a3/0x640
[   29.988338]  entry_SYSCALL_64_after_hwframe+0x46/0xbb
[   29.993508] RIP: 0033:0x7f66f1928270
[   29.997195] RSP: 002b:00007ffc114d93e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
[   30.004967] RAX: 0000000000000000 RBX: 0000000000000007 RCX: 00007f66f1928270
[   30.012226] RDX: 000000000aba9500 RSI: 0000000000000000 RDI: 0000000000000007
[   30.019493] RBP: 00007f66f27e1710 R08: 0000000000000045 R09: 0000000000000018
[   30.026752] R10: 000055f39a88d6c8 R11: 0000000000000246 R12: 0000000000000000
[   30.034000] R13: 000055f39a87cfd0 R14: 0000000000000003 R15: 000000000000000e
[   30.041976] Kernel Offset: disabled
[   30.045641] Rebooting in 86400 seconds..