------------[ cut here ]------------
refcnt < 0
WARNING: net/bluetooth/hci_conn.c:634 at hci_conn_timeout+0xff/0x2c0, CPU#0: kworker/u11:3/5620
Modules linked in:
CPU: 0 UID: 0 PID: 5620 Comm: kworker/u11:3 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
Workqueue: hci4 hci_conn_timeout
RIP: 0010:hci_conn_timeout+0xff/0x2c0
Code: 48 89 df e8 e3 ad 09 00 eb 07 e8 dc 24 2d f7 b0 13 0f b6 f0 48 89 df 5b 41 5c 41 5e 41 5f 5d e9 e7 9f fe ff e8 c2 24 2d f7 90 <0f> 0b 90 eb 8c 44 89 f9 80 e1 07 80 c1 03 38 c1 0f 8c 31 ff ff ff
RSP: 0018:ffffc9000614fad0 EFLAGS: 00010293
RAX: ffffffff8a981c0e RBX: ffff8881153a0000 RCX: ffff888117e15940
RDX: 0000000000000000 RSI: 00000000ffffffff RDI: 0000000000000000
RBP: 00000000ffffffff R08: ffff8881153a0013 R09: 1ffff11022a74002
R10: dffffc0000000000 R11: ffffed1022a74003 R12: dffffc0000000000
R13: dffffc0000000000 R14: ffff8881153a0a40 R15: ffff8881153a0010
FS:  0000000000000000(0000) GS:ffff88818dcb8000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f74bb5ea540 CR3: 00000001127e0000 CR4: 00000000000006f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <TASK>
 process_scheduled_works+0xa8e/0x14e0
 worker_thread+0xa47/0xfb0
 kthread+0x389/0x470
 ret_from_fork+0x514/0xb70
 ret_from_fork_asm+0x1a/0x30
 </TASK>
