syzbot

======================================================
WARNING: possible circular locking dependency detected
6.1.56-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.0/6024 is trying to acquire lock:
ffff888076720a90 ((work_completion)(&(&hdev->discov_off)->work)){+.+.}-{0:0}, at: __flush_work+0xe5/0xad0 kernel/workqueue.c:3072

but task is already holding lock:
ffff888076720078 (&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.0/6024:
 #0: ffff888076720078 (&hdev->lock){+.+.}-{3:3}, at: hci_unregister_dev+0x2ac/0x480 net/bluetooth/hci_core.c:2739

stack backtrace:
CPU: 0 PID: 6024 Comm: syz-executor.0 Not tainted 6.1.56-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: 0033:0x7f3f0d87cae9
Code: Unable to access opcode bytes at 0x7f3f0d87cabf.
RSP: 002b:00007f3f0e5af078 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: 0000000000000000 RBX: 00007f3f0d99bf80 RCX: 00007f3f0d87cae9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007f3f0d8c847a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f3f0d99bf80 R15: 00007ffcfde0ac78
 </TASK>