Re: [syzbot] [bluetooth?] WARNING: bad unlock balance in l2cap_recv_frame

[Dmitry Vyukov]

On Sat, 15 Apr 2023 at 13:54, syzbot
<syzbot+9519d6b5b79cf7787cf3@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    95abc817ab3a Merge tag 'acpi-6.3-rc7' of git://git.kernel...
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=13c85123c80000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=c21559e740385326
> dashboard link: https://syzkaller.appspot.com/bug?extid=9519d6b5b79cf7787cf3
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, 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/87e400f90ed9/disk-95abc817.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/cf7aa6546e50/vmlinux-95abc817.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/a44d83ac79a7/bzImage-95abc817.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+9519d6b5b79cf7787cf3@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> =====================================
> WARNING: bad unlock balance detected!
> 6.3.0-rc6-syzkaller-00168-g95abc817ab3a #0 Not tainted
> -------------------------------------
> kworker/u5:7/5124 is trying to release lock (&conn->chan_lock) at:
> [<ffffffff89148e14>] l2cap_disconnect_rsp net/bluetooth/l2cap_core.c:4697 [inline]
> [<ffffffff89148e14>] l2cap_le_sig_cmd net/bluetooth/l2cap_core.c:6426 [inline]
> [<ffffffff89148e14>] l2cap_le_sig_channel net/bluetooth/l2cap_core.c:6464 [inline]
> [<ffffffff89148e14>] l2cap_recv_frame+0x85a4/0x9390 net/bluetooth/l2cap_core.c:7796
> but there are no more locks to release!
>
> other info that might help us debug this:
> 2 locks held by kworker/u5:7/5124:
>  #0: ffff88801ecca938 ((wq_completion)hci1#2){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
>  #0: ffff88801ecca938 ((wq_completion)hci1#2){+.+.}-{0:0}, at: arch_atomic_long_set include/linux/atomic/atomic-long.h:41 [inline]
>  #0: ffff88801ecca938 ((wq_completion)hci1#2){+.+.}-{0:0}, at: atomic_long_set include/linux/atomic/atomic-instrumented.h:1280 [inline]
>  #0: ffff88801ecca938 ((wq_completion)hci1#2){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:639 [inline]
>  #0: ffff88801ecca938 ((wq_completion)hci1#2){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:666 [inline]
>  #0: ffff88801ecca938 ((wq_completion)hci1#2){+.+.}-{0:0}, at: process_one_work+0x87a/0x15c0 kernel/workqueue.c:2361
>  #1: ffffc9000468fda8 ((work_completion)(&hdev->rx_work)){+.+.}-{0:0}, at: process_one_work+0x8ae/0x15c0 kernel/workqueue.c:2365
>
> stack backtrace:
> CPU: 1 PID: 5124 Comm: kworker/u5:7 Not tainted 6.3.0-rc6-syzkaller-00168-g95abc817ab3a #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023
> Workqueue: hci1 hci_rx_work
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0xd9/0x150 lib/dump_stack.c:106
>  __lock_release kernel/locking/lockdep.c:5346 [inline]
>  lock_release+0x4f1/0x670 kernel/locking/lockdep.c:5689
>  __mutex_unlock_slowpath+0x99/0x5e0 kernel/locking/mutex.c:907
>  l2cap_disconnect_rsp net/bluetooth/l2cap_core.c:4697 [inline]
>  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+0x85a4/0x9390 net/bluetooth/l2cap_core.c:7796
>  l2cap_recv_acldata+0xa80/0xbf0 net/bluetooth/l2cap_core.c:8504
>  hci_acldata_packet net/bluetooth/hci_core.c:3828 [inline]
>  hci_rx_work+0x709/0x1340 net/bluetooth/hci_core.c:4063

/\/\/\/\/\/\/\/\

This is on the receiving path. Can this be triggered remotely?

>  process_one_work+0x991/0x15c0 kernel/workqueue.c:2390
>  worker_thread+0x669/0x1090 kernel/workqueue.c:2537
>  kthread+0x2e8/0x3a0 kernel/kthread.c:376
>  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308
>  </TASK>
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.