[v6.1] possible deadlock in hci_unregister_dev (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d23900f974e0 Linux 6.1.55
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=10cbf992680000
kernel config: https://syzkaller.appspot.com/x/.config?x=5bcd925baa8f3696
dashboard link: https://syzkaller.appspot.com/bug?extid=1908fcb1afad2b8a2be1
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/bdd6d6e750b0/disk-d23900f9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a43703f89e81/vmlinux-d23900f9.xz
kernel image: https://storage.googleapis.com/syzbot-assets/30f239dbfd4c/bzImage-d23900f9.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1908fc...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.1.55-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.1/27927 is trying to acquire lock:
ffff88807d2d0a90 ((work_completion)(&(&hdev->discov_off)->work)){+.+.}-{0:0}, at: __flush_work+0xe5/0xad0 kernel/workqueue.c:3072

but task is already holding lock:
ffff88807d2d0078 (&hdev->lock){+.+.}-{3:3}, at: hci_unregister_dev+0x2ac/0x480 net/bluetooth/hci_core.c:2739

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&hdev->lock){+.+.}-{3:3}:
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5661
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x132/0xd80 kernel/locking/mutex.c:747
discov_off+0x8e/0x1f0 net/bluetooth/mgmt.c:1049
process_one_work+0x8a9/0x11d0 kernel/workqueue.c:2292
worker_thread+0xa47/0x1200 kernel/workqueue.c:2439
kthread+0x28d/0x320 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306

-> #0 ((work_completion)(&(&hdev->discov_off)->work)){+.+.}-{0:0}:
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
__flush_work+0xfe/0xad0 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:2740
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+0xa73/0x26a0 kernel/exit.c:869
do_group_exit+0x202/0x2b0 kernel/exit.c:1019
get_signal+0x16f7/0x17d0 kernel/signal.c:2862
arch_do_signal_or_restart+0xb0/0x1a10 arch/x86/kernel/signal.c:871
exit_to_user_mode_loop+0x6a/0x100 kernel/entry/common.c:168
exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:204
__syscall_exit_to_user_mode_work kernel/entry/common.c:286 [inline]
syscall_exit_to_user_mode+0x60/0x270 kernel/entry/common.c:297
ret_from_fork+0x15/0x30 arch/x86/entry/entry_64.S:299

other info that might help us debug this:

Possible unsafe locking scenario:

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

*** DEADLOCK ***

1 lock held by syz-executor.1/27927:
#0: ffff88807d2d0078 (&hdev->lock){+.+.}-{3:3}, at: hci_unregister_dev+0x2ac/0x480 net/bluetooth/hci_core.c:2739

stack backtrace:
CPU: 0 PID: 27927 Comm: syz-executor.1 Not tainted 6.1.55-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
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
__flush_work+0xfe/0xad0 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:2740
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+0xa73/0x26a0 kernel/exit.c:869
do_group_exit+0x202/0x2b0 kernel/exit.c:1019
get_signal+0x16f7/0x17d0 kernel/signal.c:2862
arch_do_signal_or_restart+0xb0/0x1a10 arch/x86/kernel/signal.c:871
exit_to_user_mode_loop+0x6a/0x100 kernel/entry/common.c:168
exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:204
__syscall_exit_to_user_mode_work kernel/entry/common.c:286 [inline]
syscall_exit_to_user_mode+0x60/0x270 kernel/entry/common.c:297
ret_from_fork+0x15/0x30 arch/x86/entry/entry_64.S:299
RIP: 0033:0x7fda04c7cae9
Code: Unable to access opcode bytes at 0x7fda04c7cabf.
RSP: 002b:00007fda059be078 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: 0000000000000000 RBX: 00007fda04d9bf80 RCX: 00007fda04c7cae9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007fda04cc847a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007fda04d9bf80 R15: 00007ffc02f44ab8
</TASK>


---
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[syzbot]

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