syzbot

------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 0 PID: 8288 at lib/refcount.c:280 refcount_dec_not_one+0x1bc/0x1d0 lib/refcount.c:280
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 8288 Comm: systemd-udevd Not tainted 4.19.211-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/16/2023
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
 panic+0x26a/0x50e kernel/panic.c:186
 __warn.cold+0x20/0x5a kernel/panic.c:541
 report_bug+0x262/0x2b0 lib/bug.c:183
 fixup_bug arch/x86/kernel/traps.c:178 [inline]
 fixup_bug arch/x86/kernel/traps.c:173 [inline]
 do_error_trap+0x1d7/0x310 arch/x86/kernel/traps.c:296
 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:1038
RIP: 0010:refcount_dec_not_one+0x1bc/0x1d0 lib/refcount.c:280
Code: 1d d5 96 98 07 31 ff 89 de e8 f0 71 ec fd 84 db 75 89 e8 b7 70 ec fd 48 c7 c7 e0 c0 b3 88 c6 05 b5 96 98 07 01 e8 89 a8 7c 04 <0f> 0b 41 bc 01 00 00 00 e9 6a ff ff ff e8 22 91 c1 fd 66 90 41 54
RSP: 0018:ffff8880af76fbd0 EFLAGS: 00010282
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff814dff01 RDI: ffffed1015eedf6c
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000005 R11: 0000000000000000 R12: 00000000ffffffff
R13: 1ffff11015eedf7b R14: ffff8880af76fbf8 R15: ffff8880a9470868
 refcount_dec_and_mutex_lock+0x1c/0x80 lib/refcount.c:308
 nbd_put drivers/block/nbd.c:228 [inline]
 nbd_config_put+0x5bb/0x870 drivers/block/nbd.c:1185
 nbd_release+0xf4/0x170 drivers/block/nbd.c:1461
 __blkdev_put+0x636/0x870 fs/block_dev.c:1819
 blkdev_close+0x86/0xb0 fs/block_dev.c:1888
 __fput+0x2ce/0x890 fs/file_table.c:278
 task_work_run+0x148/0x1c0 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:193 [inline]
 exit_to_usermode_loop+0x251/0x2a0 arch/x86/entry/common.c:167
 prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:271 [inline]
 do_syscall_64+0x538/0x620 arch/x86/entry/common.c:296
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7fab95d3a270
Code: 73 01 c3 48 8b 0d 38 7d 20 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 83 3d 59 c1 20 00 00 75 10 b8 03 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 ee fb ff ff 48 89 04 24
RSP: 002b:00007ffd4343bc18 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000007 RCX: 00007fab95d3a270
RDX: 000000000aba9500 RSI: 0000000000000000 RDI: 0000000000000007
RBP: 00007fab96bf4710 R08: 0000000000000045 R09: 0000000000000018
R10: 000055ca705ee1b8 R11: 0000000000000246 R12: 0000000000000000
R13: 000055ca705e96e0 R14: 0000000000000003 R15: 000000000000000e
Kernel Offset: disabled
Rebooting in 86400 seconds..