[v6.1] WARNING: bad unlock balance in l2cap_bredr_sig_cmd

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: ca48fc16c493 Linux 6.1.27
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=118779c4280000
kernel config: https://syzkaller.appspot.com/x/.config?x=47d3bbfdb3b1ddd2
dashboard link: https://syzkaller.appspot.com/bug?extid=f361c6432ae5d7e28e52
compiler: Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/658765c915fa/disk-ca48fc16.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d69e8a1aff2d/vmlinux-ca48fc16.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0317a9546209/bzImage-ca48fc16.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f361c6...@syzkaller.appspotmail.com

=====================================
WARNING: bad unlock balance detected!
6.1.27-syzkaller #0 Not tainted
-------------------------------------
kworker/u5:5/3599 is trying to release lock (&conn->chan_lock) at:
[<ffffffff89946727>] l2cap_bredr_sig_cmd+0xb07/0x9fb0 net/bluetooth/l2cap_core.c:5748
but there are no more locks to release!

other info that might help us debug this:
2 locks held by kworker/u5:5/3599:
#0: ffff888076318138 ((wq_completion)hci1#2){+.+.}-{0:0}, at: process_one_work+0x77a/0x11f0
#1: ffffc90003e5fd20 ((work_completion)(&hdev->rx_work)){+.+.}-{0:0}, at: process_one_work+0x7bd/0x11f0 kernel/workqueue.c:2264

stack backtrace:
CPU: 1 PID: 3599 Comm: kworker/u5:5 Not tainted 6.1.27-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023
Workqueue: hci1 hci_rx_work
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
print_unlock_imbalance_bug+0x24e/0x2c0 kernel/locking/lockdep.c:5109
__lock_release kernel/locking/lockdep.c:5346 [inline]
lock_release+0x5ad/0xa20 kernel/locking/lockdep.c:5689
__mutex_unlock_slowpath+0xde/0x750 kernel/locking/mutex.c:907
l2cap_bredr_sig_cmd+0xb07/0x9fb0 net/bluetooth/l2cap_core.c:5748
l2cap_sig_channel net/bluetooth/l2cap_core.c:6507 [inline]
l2cap_recv_frame+0xa59/0x8890 net/bluetooth/l2cap_core.c:7786
hci_acldata_packet net/bluetooth/hci_core.c:3828 [inline]
hci_rx_work+0x39b/0xa80 net/bluetooth/hci_core.c:4063
process_one_work+0x8aa/0x11f0 kernel/workqueue.c:2289
worker_thread+0xa5f/0x1210 kernel/workqueue.c:2436
kthread+0x26e/0x300 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
</TASK>
Bluetooth: Wrong link type (-22)


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.