Warning: Permanently added '10.128.0.57' (ECDSA) to the list of known hosts.
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syzkaller login: [   28.865275] refcount_t: underflow; use-after-free.
[   28.870594] ------------[ cut here ]------------
[   28.875394] WARNING: CPU: 1 PID: 8129 at lib/refcount.c:281 refcount_dec_not_one.cold+0x18/0x25
[   28.884275] Kernel panic - not syncing: panic_on_warn set ...
[   28.884275] 
[   28.891621] CPU: 1 PID: 8129 Comm: systemd-udevd Not tainted 4.14.280-syzkaller #0
[   28.899304] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
[   28.908644] Call Trace:
[   28.911219]  dump_stack+0x1b2/0x281
[   28.914943]  panic+0x1f9/0x42d
[   28.918121]  ? add_taint.cold+0x16/0x16
[   28.922085]  ? refcount_dec_not_one.cold+0x18/0x25
[   28.927000]  ? refcount_dec_not_one.cold+0x18/0x25
[   28.931921]  __warn.cold+0x20/0x44
[   28.935448]  ? ist_end_non_atomic+0x10/0x10
[   28.939756]  ? refcount_dec_not_one.cold+0x18/0x25
[   28.944666]  report_bug+0x208/0x250
[   28.948286]  do_error_trap+0x195/0x2d0
[   28.952160]  ? math_error+0x2d0/0x2d0
[   28.955940]  ? ___preempt_schedule+0x16/0x18
[   28.960331]  ? trace_hardirqs_off_thunk+0x1a/0x1c
[   28.965150]  invalid_op+0x1b/0x40
[   28.968608] RIP: 0010:refcount_dec_not_one.cold+0x18/0x25
[   28.974303] RSP: 0018:ffff8880b1087c38 EFLAGS: 00010286
[   28.979857] RAX: 0000000000000026 RBX: 0000000000000000 RCX: 0000000000000000
[   28.987465] RDX: 0000000000000000 RSI: ffffffff878bc600 RDI: ffffed1016210f7d
[   28.994724] RBP: ffff8880ab5d6ad8 R08: 0000000000000026 R09: 0000000000000000
[   29.001993] R10: 0000000000000000 R11: 0000000000000000 R12: 00000000ffffffff
[   29.009394] R13: 0000000000000000 R14: ffffed1011bea536 R15: ffff8880ab5d6ae8
[   29.016771]  ? refcount_dec_not_one.cold+0x18/0x25
[   29.021701]  ? trace_hardirqs_on_caller+0x3a8/0x580
[   29.026711]  refcount_dec_and_mutex_lock+0x1a/0x60
[   29.031632]  nbd_config_put+0x506/0x810
[   29.035594]  nbd_release+0xdf/0x150
[   29.039258]  ? nbd_queue_rq+0xc50/0xc50
[   29.043219]  __blkdev_put+0x5aa/0x800
[   29.047005]  ? revalidate_disk+0x1f0/0x1f0
[   29.051237]  ? locks_remove_file+0x2cd/0x420
[   29.055644]  ? blkdev_put+0x75/0x4c0
[   29.059345]  ? blkdev_put+0x4c0/0x4c0
[   29.063130]  blkdev_close+0x86/0xb0
[   29.066735]  __fput+0x25f/0x7a0
[   29.070006]  task_work_run+0x11f/0x190
[   29.073889]  exit_to_usermode_loop+0x1ad/0x200
[   29.078464]  do_syscall_64+0x4a3/0x640
[   29.082332]  entry_SYSCALL_64_after_hwframe+0x46/0xbb
[   29.087517] RIP: 0033:0x7f7876878270
[   29.091218] RSP: 002b:00007ffca2a7dc38 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
[   29.098915] RAX: 0000000000000000 RBX: 0000000000000007 RCX: 00007f7876878270
[   29.106169] RDX: 000000000aba9500 RSI: 0000000000000000 RDI: 0000000000000007
[   29.113420] RBP: 00007f7877732710 R08: 000055ba4faf9ee0 R09: 0000000000000018
[   29.120702] R10: 000055ba4fafabd8 R11: 0000000000000246 R12: 0000000000000000
[   29.127954] R13: 000055ba4faf56e0 R14: 0000000000000003 R15: 000000000000000e
[   29.135589] Kernel Offset: disabled
[   29.139251] Rebooting in 86400 seconds..