------------[ cut here ]------------
refcnt < 0
WARNING: net/bluetooth/hci_conn.c:631 at hci_conn_timeout+0xff/0x2c0 net/bluetooth/hci_conn.c:631, CPU#0: kworker/u5:2/5276
Modules linked in:
CPU: 0 UID: 0 PID: 5276 Comm: kworker/u5:2 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:631
Code: 48 89 df e8 c3 cc 09 00 eb 07 e8 3c 2d ff f6 b0 13 0f b6 f0 48 89 df 5b 41 5c 41 5e 41 5f 5d e9 b7 a0 fe ff e8 22 2d ff f6 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:ffffc9000df97ad0 EFLAGS: 00010293
RAX: ffffffff8ac7e4be RBX: ffff888012ecc000 RCX: ffff888012bc8000
RDX: 0000000000000000 RSI: 00000000ffffffff RDI: 0000000000000000
RBP: 00000000ffffffff R08: ffff888012ecc013 R09: 1ffff110025d9802
R10: dffffc0000000000 R11: ffffed10025d9803 R12: dffffc0000000000
R13: dffffc0000000000 R14: ffff888012ecca40 R15: ffff888012ecc010
FS:  0000000000000000(0000) GS:ffff88808c53e000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc626f8dd80 CR3: 000000001d367000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>