syzbot

======================================================
WARNING: possible circular locking dependency detected
6.2.0-rc5-syzkaller-00013-g2475bf0250de #0 Not tainted
------------------------------------------------------
syz-executor.3/5095 is trying to acquire lock:
ffff888027194a00 ((work_completion)(&(&hdev->discov_off)->work)){+.+.}-{0:0}, at: __flush_work+0xdd/0xaf0 kernel/workqueue.c:3066

but task is already holding lock:
ffff888027194078 (&hdev->lock){+.+.}-{3:3}, at: hci_unregister_dev+0x396/0x580 net/bluetooth/hci_core.c:2707

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&hdev->lock){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x12f/0x1360 kernel/locking/mutex.c:747
       discov_off+0x8c/0x1a0 net/bluetooth/mgmt.c:1037
       process_one_work+0x9bf/0x1710 kernel/workqueue.c:2289
       worker_thread+0x669/0x1090 kernel/workqueue.c:2436
       kthread+0x2e8/0x3a0 kernel/kthread.c:376
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

-> #0 ((work_completion)(&(&hdev->discov_off)->work)){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3097 [inline]
       check_prevs_add kernel/locking/lockdep.c:3216 [inline]
       validate_chain kernel/locking/lockdep.c:3831 [inline]
       __lock_acquire+0x2a43/0x56d0 kernel/locking/lockdep.c:5055
       lock_acquire kernel/locking/lockdep.c:5668 [inline]
       lock_acquire+0x1e3/0x630 kernel/locking/lockdep.c:5633
       __flush_work+0x109/0xaf0 kernel/workqueue.c:3069
       __cancel_work_timer+0x3f9/0x570 kernel/workqueue.c:3160
       mgmt_index_removed+0x21c/0x340 net/bluetooth/mgmt.c:9432
       hci_unregister_dev+0x39e/0x580 net/bluetooth/hci_core.c:2708
       vhci_release+0x80/0xf0 drivers/bluetooth/hci_vhci.c:568
       __fput+0x27c/0xa90 fs/file_table.c:320
       task_work_run+0x16f/0x270 kernel/task_work.c:179
       exit_task_work include/linux/task_work.h:38 [inline]
       do_exit+0xaa8/0x2950 kernel/exit.c:867
       do_group_exit+0xd4/0x2a0 kernel/exit.c:1012
       __do_sys_exit_group kernel/exit.c:1023 [inline]
       __se_sys_exit_group kernel/exit.c:1021 [inline]
       __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1021
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x63/0xcd

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.3/5095:
 #0: ffff888027194078 (&hdev->lock){+.+.}-{3:3}, at: hci_unregister_dev+0x396/0x580 net/bluetooth/hci_core.c:2707

stack backtrace:
CPU: 0 PID: 5095 Comm: syz-executor.3 Not tainted 6.2.0-rc5-syzkaller-00013-g2475bf0250de #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/12/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd1/0x138 lib/dump_stack.c:106
 check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2177
 check_prev_add kernel/locking/lockdep.c:3097 [inline]
 check_prevs_add kernel/locking/lockdep.c:3216 [inline]
 validate_chain kernel/locking/lockdep.c:3831 [inline]
 __lock_acquire+0x2a43/0x56d0 kernel/locking/lockdep.c:5055
 lock_acquire kernel/locking/lockdep.c:5668 [inline]
 lock_acquire+0x1e3/0x630 kernel/locking/lockdep.c:5633
 __flush_work+0x109/0xaf0 kernel/workqueue.c:3069
 __cancel_work_timer+0x3f9/0x570 kernel/workqueue.c:3160
 mgmt_index_removed+0x21c/0x340 net/bluetooth/mgmt.c:9432
 hci_unregister_dev+0x39e/0x580 net/bluetooth/hci_core.c:2708
 vhci_release+0x80/0xf0 drivers/bluetooth/hci_vhci.c:568
 __fput+0x27c/0xa90 fs/file_table.c:320
 task_work_run+0x16f/0x270 kernel/task_work.c:179
 exit_task_work include/linux/task_work.h:38 [inline]
 do_exit+0xaa8/0x2950 kernel/exit.c:867
 do_group_exit+0xd4/0x2a0 kernel/exit.c:1012
 __do_sys_exit_group kernel/exit.c:1023 [inline]
 __se_sys_exit_group kernel/exit.c:1021 [inline]
 __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1021
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f93fb68c0c9
Code: Unable to access opcode bytes at 0x7f93fb68c09f.
RSP: 002b:00007fff6e1e3298 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007fff6e1e3440 RCX: 00007f93fb68c0c9
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000043
RBP: 0000000000000000 R08: 0000000000000025 R09: 00007fff6e1e3440
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f93fb6e7aba
R13: 000000000000001c R14: 000000000000001c R15: 00007fff6e1e3480
 </TASK>