------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 1 PID: 10908 at lib/refcount.c:28 refcount_warn_saturate+0x11a/0x1d0
Modules linked in:
CPU: 1 UID: 0 PID: 10908 Comm: kbnepd bnep0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:refcount_warn_saturate+0x11a/0x1d0
Code: 00 b3 e2 8b e8 37 34 bb fc 90 0f 0b 90 90 eb d7 e8 8b 95 f7 fc c6 05 2c 70 c5 0a 01 90 48 c7 c7 60 b3 e2 8b e8 17 34 bb fc 90 <0f> 0b 90 90 eb b7 e8 6b 95 f7 fc c6 05 09 70 c5 0a 01 90 48 c7 c7
RSP: 0018:ffffc9000441f700 EFLAGS: 00010246
RAX: 4e372597fa7fea00 RBX: 0000000000000003 RCX: ffff88803cfc3980
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000002
RBP: 0000000000000000 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff1bfa1ec R12: dffffc0000000000
R13: ffff8881101cd460 R14: ffff8881101cd478 R15: ffffffff86002530
FS:  0000000000000000(0000) GS:ffff8881a3c14000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000011e48a000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 klist_dec_and_del+0x3c7/0x3d0
 klist_del+0xa6/0x110
 device_del+0x280/0x8e0
 unregister_netdevice_many_notify+0x1a6b/0x1ff0
 unregister_netdevice_queue+0x33c/0x380
 unregister_netdev+0x1f/0x60
 bnep_session+0x294d/0x2b40
 kthread+0x711/0x8a0
 ret_from_fork+0x3fc/0x770
 ret_from_fork_asm+0x1a/0x30
 </TASK>
