syzbot

======================================================
WARNING: possible circular locking dependency detected
6.7.0-rc6-syzkaller #0 Not tainted
------------------------------------------------------
kworker/u5:3/23027 is trying to acquire lock:
ffff8880326f8078 (&hdev->lock){+.+.}-{3:3}, at: discov_off+0x8c/0x1d0 net/bluetooth/mgmt.c:1055

but task is already holding lock:
ffffc9000344fd80 ((work_completion)(&(&hdev->discov_off)->work)){+.+.}-{0:0}, at: process_one_work+0x7eb/0x15d0 kernel/workqueue.c:2603

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}:
       __flush_work+0x103/0xa10 kernel/workqueue.c:3400
       __cancel_work_timer+0x3ef/0x590 kernel/workqueue.c:3491
       mgmt_index_removed+0x1ed/0x350 net/bluetooth/mgmt.c:9436
       hci_unregister_dev+0x472/0x600 net/bluetooth/hci_core.c:2745
       vhci_release+0x7f/0x100 drivers/bluetooth/hci_vhci.c:672
       __fput+0x270/0xb70 fs/file_table.c:394
       task_work_run+0x14d/0x240 kernel/task_work.c:180
       exit_task_work include/linux/task_work.h:38 [inline]
       do_exit+0xa8a/0x2ad0 kernel/exit.c:869
       do_group_exit+0xd4/0x2a0 kernel/exit.c:1018
       get_signal+0x23b5/0x2790 kernel/signal.c:2904
       arch_do_signal_or_restart+0x90/0x7f0 arch/x86/kernel/signal.c:309
       exit_to_user_mode_loop kernel/entry/common.c:168 [inline]
       exit_to_user_mode_prepare+0x121/0x240 kernel/entry/common.c:204
       __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline]
       syscall_exit_to_user_mode+0x1e/0x60 kernel/entry/common.c:296
       do_syscall_64+0x4d/0x110 arch/x86/entry/common.c:89
       entry_SYSCALL_64_after_hwframe+0x63/0x6b

-> #0 (&hdev->lock){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3134 [inline]
       check_prevs_add kernel/locking/lockdep.c:3253 [inline]
       validate_chain kernel/locking/lockdep.c:3869 [inline]
       __lock_acquire+0x2433/0x3b20 kernel/locking/lockdep.c:5137
       lock_acquire kernel/locking/lockdep.c:5754 [inline]
       lock_acquire+0x1ae/0x520 kernel/locking/lockdep.c:5719
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x175/0x9d0 kernel/locking/mutex.c:747
       discov_off+0x8c/0x1d0 net/bluetooth/mgmt.c:1055
       process_one_work+0x886/0x15d0 kernel/workqueue.c:2627
       process_scheduled_works kernel/workqueue.c:2700 [inline]
       worker_thread+0x8b9/0x1290 kernel/workqueue.c:2781
       kthread+0x2c6/0x3a0 kernel/kthread.c:388
       ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
       ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242

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/u5:3/23027:
 #0: ffff88807ed3f938 ((wq_completion)hci0){+.+.}-{0:0}, at: process_one_work+0x789/0x15d0 kernel/workqueue.c:2602
 #1: ffffc9000344fd80 ((work_completion)(&(&hdev->discov_off)->work)){+.+.}-{0:0}, at: process_one_work+0x7eb/0x15d0 kernel/workqueue.c:2603

stack backtrace:
CPU: 1 PID: 23027 Comm: kworker/u5:3 Not tainted 6.7.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
Workqueue: hci0 discov_off
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106
 check_noncircular+0x317/0x400 kernel/locking/lockdep.c:2187
 check_prev_add kernel/locking/lockdep.c:3134 [inline]
 check_prevs_add kernel/locking/lockdep.c:3253 [inline]
 validate_chain kernel/locking/lockdep.c:3869 [inline]
 __lock_acquire+0x2433/0x3b20 kernel/locking/lockdep.c:5137
 lock_acquire kernel/locking/lockdep.c:5754 [inline]
 lock_acquire+0x1ae/0x520 kernel/locking/lockdep.c:5719
 __mutex_lock_common kernel/locking/mutex.c:603 [inline]
 __mutex_lock+0x175/0x9d0 kernel/locking/mutex.c:747
 discov_off+0x8c/0x1d0 net/bluetooth/mgmt.c:1055
 process_one_work+0x886/0x15d0 kernel/workqueue.c:2627
 process_scheduled_works kernel/workqueue.c:2700 [inline]
 worker_thread+0x8b9/0x1290 kernel/workqueue.c:2781
 kthread+0x2c6/0x3a0 kernel/kthread.c:388
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242
 </TASK>