Subject: [syzbot] [bluetooth?] WARNING: bad unlock balance in l2cap_disconnect_rsp

From: syzbot <[email-masked]>
Date: Wed, 19 Apr 2023 01:59:58 -0700

Hello,

syzbot found the following issue on:

HEAD commit:    327bf9bb94cf Merge branch 'for-next/core' into for-kernelci
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=107f83b7c80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=64943844c9bf6c7e
dashboard link: https://syzkaller.appspot.com/bug?extid=180f35f8e76c7af067d2
compiler:       Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2
userspace arch: arm64

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/66410afe54f5/disk-327bf9bb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2757ce5e2a55/vmlinux-327bf9bb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7d54ee97c182/Image-327bf9bb.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

=====================================
WARNING: bad unlock balance detected!
6.3.0-rc7-syzkaller-g327bf9bb94cf #0 Not tainted
-------------------------------------
kworker/u5:3/6019 is trying to release lock (&conn->chan_lock) at:
[<ffff80001157e164>] l2cap_disconnect_rsp+0x210/0x30c net/bluetooth/l2cap_core.c:4697
but there are no more locks to release!

other info that might help us debug this:
2 locks held by kworker/u5:3/6019:
 #0: ffff0000c0e30938 ((wq_completion)hci0#2){+.+.}-{0:0}, at: process_one_work+0x664/0x12d4 kernel/workqueue.c:2363
 #1: ffff80001ea87c20 ((work_completion)(&hdev->rx_work)){+.+.}-{0:0}, at: process_one_work+0x6a8/0x12d4 kernel/workqueue.c:2365

stack backtrace:
CPU: 1 PID: 6019 Comm: kworker/u5:3 Not tainted 6.3.0-rc7-syzkaller-g327bf9bb94cf #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023
Workqueue: hci0 hci_rx_work
Call trace:
 dump_backtrace+0x1b8/0x1e4 arch/arm64/kernel/stacktrace.c:233
 show_stack+0x2c/0x44 arch/arm64/kernel/stacktrace.c:240
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd0/0x124 lib/dump_stack.c:106
 dump_stack+0x1c/0x28 lib/dump_stack.c:113
 print_unlock_imbalance_bug+0x250/0x2a4 kernel/locking/lockdep.c:5109
 lock_release+0x4ac/0x9ac kernel/locking/lockdep.c:5689
 __mutex_unlock_slowpath+0xe0/0x6b4 kernel/locking/mutex.c:907
 mutex_unlock+0x18/0x24 kernel/locking/mutex.c:543
 l2cap_disconnect_rsp+0x210/0x30c net/bluetooth/l2cap_core.c:4697
 l2cap_le_sig_cmd net/bluetooth/l2cap_core.c:6426 [inline]
 l2cap_le_sig_channel net/bluetooth/l2cap_core.c:6464 [inline]
 l2cap_recv_frame+0x18b4/0x6a14 net/bluetooth/l2cap_core.c:7796
 l2cap_recv_acldata+0x4f4/0x163c net/bluetooth/l2cap_core.c:8504
 hci_acldata_packet net/bluetooth/hci_core.c:3828 [inline]
 hci_rx_work+0x2cc/0x8b8 net/bluetooth/hci_core.c:4063
 process_one_work+0x788/0x12d4 kernel/workqueue.c:2390
 worker_thread+0x8e0/0xfe8 kernel/workqueue.c:2537
 kthread+0x24c/0x2d4 kernel/kthread.c:376
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:870

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