[v6.1] possible deadlock in discov_off

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: a356197db198 Linux 6.1.54
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=173504a6680000
kernel config: https://syzkaller.appspot.com/x/.config?x=86626d0659ddddaf
dashboard link: https://syzkaller.appspot.com/bug?extid=40005e4555ce0d58443f
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c61f5c33e733/disk-a356197d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f3643a8f0c53/vmlinux-a356197d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a3fcbc0d79f3/bzImage-a356197d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+40005e...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.1.54-syzkaller #0 Not tainted
------------------------------------------------------
kworker/u5:0/12543 is trying to acquire lock:
ffff88807361c078 (&hdev->lock){+.+.}-{3:3}, at: discov_off+0x8e/0x1f0 net/bluetooth/mgmt.c:1049

but task is already holding lock:
ffffc9000611fd20 ((work_completion)(&(&hdev->discov_off)->work)){+.+.}-{0:0}, at: process_one_work+0x7bd/0x11f0 kernel/workqueue.c:2267

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 ((work_completion)(&(&hdev->discov_off)->work)){+.+.}-{0:0}:
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5661
__flush_work+0xeb/0x1a0 kernel/workqueue.c:3072
__cancel_work_timer+0x519/0x6a0 kernel/workqueue.c:3163
mgmt_index_removed+0x2f6/0x440 net/bluetooth/mgmt.c:9436
hci_unregister_dev+0x2b4/0x480 net/bluetooth/hci_core.c:2736
vhci_release+0x7f/0xd0 drivers/bluetooth/hci_vhci.c:568
__fput+0x3b7/0x890 fs/file_table.c:320
task_work_run+0x246/0x300 kernel/task_work.c:179
exit_task_work include/linux/task_work.h:38 [inline]
do_exit+0x6fb/0x2300 kernel/exit.c:869
do_group_exit+0x202/0x2b0 kernel/exit.c:1019
__do_sys_exit_group kernel/exit.c:1030 [inline]
__se_sys_exit_group kernel/exit.c:1028 [inline]
__x64_sys_exit_group+0x3b/0x40 kernel/exit.c:1028
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #0 (&hdev->lock){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3090 [inline]
check_prevs_add kernel/locking/lockdep.c:3209 [inline]
validate_chain+0x1667/0x58e0 kernel/locking/lockdep.c:3824
__lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5048
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5661
__mutex_lock_common+0x1d4/0x2520 kernel/locking/mutex.c:603
__mutex_lock kernel/locking/mutex.c:747 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:799
discov_off+0x8e/0x1f0 net/bluetooth/mgmt.c:1049
process_one_work+0x8aa/0x11f0 kernel/workqueue.c:2292
worker_thread+0xa5f/0x1210 kernel/workqueue.c:2439
kthread+0x26e/0x300 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock((work_completion)(&(&hdev->discov_off)->work));
lock(&hdev->lock);
lock((work_completion)(&(&hdev->discov_off)->work));
lock(&hdev->lock);

*** DEADLOCK ***

2 locks held by kworker/u5:0/12543:
#0: ffff888078516938 ((wq_completion)hci0){+.+.}-{0:0}, at: process_one_work+0x77a/0x11f0
#1: ffffc9000611fd20 ((work_completion)(&(&hdev->discov_off)->work)){+.+.}-{0:0}, at: process_one_work+0x7bd/0x11f0 kernel/workqueue.c:2267

stack backtrace:
CPU: 0 PID: 12543 Comm: kworker/u5:0 Not tainted 6.1.54-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/04/2023
Workqueue: hci0 discov_off
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
check_noncircular+0x2fa/0x3b0 kernel/locking/lockdep.c:2170
check_prev_add kernel/locking/lockdep.c:3090 [inline]
check_prevs_add kernel/locking/lockdep.c:3209 [inline]
validate_chain+0x1667/0x58e0 kernel/locking/lockdep.c:3824
__lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5048
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5661
__mutex_lock_common+0x1d4/0x2520 kernel/locking/mutex.c:603
__mutex_lock kernel/locking/mutex.c:747 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:799
discov_off+0x8e/0x1f0 net/bluetooth/mgmt.c:1049
process_one_work+0x8aa/0x11f0 kernel/workqueue.c:2292
worker_thread+0xa5f/0x1210 kernel/workqueue.c:2439
kthread+0x26e/0x300 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
</TASK>


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[syzbot]

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