------------[ cut here ]------------
refcnt < 0
WARNING: net/bluetooth/hci_conn.c:567 at hci_conn_timeout+0xff/0x2c0 net/bluetooth/hci_conn.c:567, CPU#0: kworker/u5:1/4663
Modules linked in:
CPU: 0 UID: 0 PID: 4663 Comm: kworker/u5:1 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: hci0 hci_conn_timeout
RIP: 0010:hci_conn_timeout+0xff/0x2c0 net/bluetooth/hci_conn.c:567
Code: 48 89 df e8 83 99 09 00 eb 07 e8 dc 04 23 f7 b0 13 0f b6 f0 48 89 df 5b 41 5c 41 5e 41 5f 5d e9 87 a8 fe ff e8 c2 04 23 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: 0000:ffffc9000fbbfad0 EFLAGS: 00010293
RAX: ffffffff8aa296ae RBX: ffff88801255c000 RCX: ffff88801cfa8000
RDX: 0000000000000000 RSI: 00000000ffffffff RDI: 0000000000000000
RBP: 00000000ffffffff R08: ffff88801255c013 R09: 1ffff110024ab802
R10: dffffc0000000000 R11: ffffed10024ab803 R12: dffffc0000000000
R13: ffff88801fa8a018 R14: ffff88801255ca40 R15: ffff88801255c010
FS:  0000000000000000(0000) GS:ffff88808ca58000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f5f66503008 CR3: 0000000041b92000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 process_one_work kernel/workqueue.c:3275 [inline]
 process_scheduled_works+0xb02/0x1830 kernel/workqueue.c:3358
 worker_thread+0xa50/0xfc0 kernel/workqueue.c:3439
 kthread+0x388/0x470 kernel/kthread.c:467
 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>