======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz-executor/4330 is trying to acquire lock:
ffff0000cee9cbb8 ((work_completion)(&(&hdev->discov_off)->work)){+.+.}-{0:0}, at: __flush_work+0xe4/0x1ec kernel/workqueue.c:3069

but task is already holding lock:
ffff0000cee9c428 (&hdev->lock
){+.+.}-{3:3}
, at: hci_unregister_dev+0x29c/0x4c8 net/bluetooth/hci_core.c:2722

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1
 (&hdev->lock
){+.+.}-{3:3}:
       __mutex_lock_common+0x1a0/0x1f3c kernel/locking/mutex.c:603
       __mutex_lock kernel/locking/mutex.c:747 [inline]
       mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799
       discov_off+0x94/0x230 net/bluetooth/mgmt.c:1034
       process_one_work+0x7e4/0x13bc kernel/workqueue.c:2292
       worker_thread+0x8cc/0xfe8 kernel/workqueue.c:2439
       kthread+0x254/0x2e0 kernel/kthread.c:376
       ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850

-> #0 ((work_completion)(&(&hdev->discov_off)->work)){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3095 [inline]
       check_prevs_add kernel/locking/lockdep.c:3214 [inline]
       validate_chain kernel/locking/lockdep.c:3830 [inline]
       __lock_acquire+0x2808/0x6634 kernel/locking/lockdep.c:5063
       lock_acquire+0x20c/0x638 kernel/locking/lockdep.c:5676
       __flush_work+0x10c/0x1ec kernel/workqueue.c:3072
       __cancel_work_timer+0x2f8/0x450 kernel/workqueue.c:3163
       cancel_delayed_work_sync+0x24/0x38 kernel/workqueue.c:3304
       mgmt_index_removed+0x1f8/0x290 net/bluetooth/mgmt.c:9490
       hci_unregister_dev+0x2a4/0x4c8 net/bluetooth/hci_core.c:2723
       vhci_release+0x7c/0xcc drivers/bluetooth/hci_vhci.c:565
       __fput+0x1b4/0x7b0 fs/file_table.c:320
       ____fput+0x20/0x30 fs/file_table.c:348
       task_work_run+0x1f4/0x280 kernel/task_work.c:203
       exit_task_work include/linux/task_work.h:39 [inline]
       do_exit+0x54c/0x19ac kernel/exit.c:887
       do_group_exit+0x198/0x238 kernel/exit.c:1030
       get_signal+0x11f4/0x133c kernel/signal.c:2880
       do_signal arch/arm64/kernel/signal.c:1095 [inline]
       do_notify_resume+0x364/0x2c84 arch/arm64/kernel/signal.c:1148
       prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline]
       exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline]
       el0_svc+0x98/0x128 arch/arm64/kernel/entry-common.c:638
       el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
       el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

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/4330:
 #0: ffff0000cee9c428 (&hdev->lock){+.+.}-{3:3}, at: hci_unregister_dev+0x29c/0x4c8 net/bluetooth/hci_core.c:2722

stack backtrace:
CPU: 0 PID: 4330 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/07/2026
Call trace:
 dump_backtrace+0x1c4/0x1f0 arch/arm64/kernel/stacktrace.c:158
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf4/0x15c lib/dump_stack.c:106
 dump_stack+0x1c/0x5c lib/dump_stack.c:113
 print_circular_bug+0x148/0x1b0 kernel/locking/lockdep.c:2048
 check_noncircular+0x264/0x2f8 kernel/locking/lockdep.c:2170
 check_prev_add kernel/locking/lockdep.c:3095 [inline]
 check_prevs_add kernel/locking/lockdep.c:3214 [inline]
 validate_chain kernel/locking/lockdep.c:3830 [inline]
 __lock_acquire+0x2808/0x6634 kernel/locking/lockdep.c:5063
 lock_acquire+0x20c/0x638 kernel/locking/lockdep.c:5676
 __flush_work+0x10c/0x1ec kernel/workqueue.c:3072
 __cancel_work_timer+0x2f8/0x450 kernel/workqueue.c:3163
 cancel_delayed_work_sync+0x24/0x38 kernel/workqueue.c:3304
 mgmt_index_removed+0x1f8/0x290 net/bluetooth/mgmt.c:9490
 hci_unregister_dev+0x2a4/0x4c8 net/bluetooth/hci_core.c:2723
 vhci_release+0x7c/0xcc drivers/bluetooth/hci_vhci.c:565
 __fput+0x1b4/0x7b0 fs/file_table.c:320
 ____fput+0x20/0x30 fs/file_table.c:348
 task_work_run+0x1f4/0x280 kernel/task_work.c:203
 exit_task_work include/linux/task_work.h:39 [inline]
 do_exit+0x54c/0x19ac kernel/exit.c:887
 do_group_exit+0x198/0x238 kernel/exit.c:1030
 get_signal+0x11f4/0x133c kernel/signal.c:2880
 do_signal arch/arm64/kernel/signal.c:1095 [inline]
 do_notify_resume+0x364/0x2c84 arch/arm64/kernel/signal.c:1148
 prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline]
 exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline]
 el0_svc+0x98/0x128 arch/arm64/kernel/entry-common.c:638
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585