======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
kworker/u5:4/4330 is trying to acquire lock:
ffffffff8d5b37c8 (rfcomm_mutex){+.+.}-{3:3}, at: rfcomm_security_cfm+0x95/0x780 net/bluetooth/rfcomm/core.c:2210

but task is already holding lock:
ffffffff8d593e48 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_auth_cfm include/net/bluetooth/hci_core.h:1540 [inline]
ffffffff8d593e48 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_auth_complete_evt+0x308/0xbb0 net/bluetooth/hci_event.c:3067

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (hci_cb_list_lock){+.+.}-{3:3}:
       __mutex_lock_common+0x1e5/0x2400 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
       hci_connect_cfm include/net/bluetooth/hci_core.h:1504 [inline]
       hci_remote_features_evt+0x5d9/0xa10 net/bluetooth/hci_event.c:3367
       hci_event_packet+0x600/0x1310 net/bluetooth/hci_event.c:6455
       hci_rx_work+0x255/0xa10 net/bluetooth/hci_core.c:5190
       process_one_work+0x867/0xff0 kernel/workqueue.c:2310
       worker_thread+0xad7/0x12a0 kernel/workqueue.c:2457
       kthread+0x42e/0x520 kernel/kthread.c:334
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

-> #1 (&hdev->lock){+.+.}-{3:3}:
       __mutex_lock_common+0x1e5/0x2400 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
       l2cap_chan_connect+0xfb/0xe20 net/bluetooth/l2cap_core.c:8205
       l2cap_sock_connect+0x5a3/0x770 net/bluetooth/l2cap_sock.c:255
       kernel_connect+0x11c/0x180 net/socket.c:3498
       rfcomm_session_create net/bluetooth/rfcomm/core.c:807 [inline]
       __rfcomm_dlc_open net/bluetooth/rfcomm/core.c:384 [inline]
       rfcomm_dlc_open+0x600/0x10c0 net/bluetooth/rfcomm/core.c:427
       rfcomm_sock_connect+0x2e9/0x600 net/bluetooth/rfcomm/sock.c:421
       __sys_connect_file net/socket.c:1933 [inline]
       __sys_connect+0x3cb/0x450 net/socket.c:1950
       __do_sys_connect net/socket.c:1960 [inline]
       __se_sys_connect net/socket.c:1957 [inline]
       __x64_sys_connect+0x76/0x80 net/socket.c:1957
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #0 (rfcomm_mutex){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3053 [inline]
       check_prevs_add kernel/locking/lockdep.c:3172 [inline]
       validate_chain kernel/locking/lockdep.c:3788 [inline]
       __lock_acquire+0x2c66/0x7b50 kernel/locking/lockdep.c:5012
       lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5625
       __mutex_lock_common+0x1e5/0x2400 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
       rfcomm_security_cfm+0x95/0x780 net/bluetooth/rfcomm/core.c:2210
       hci_auth_cfm include/net/bluetooth/hci_core.h:1543 [inline]
       hci_auth_complete_evt+0x388/0xbb0 net/bluetooth/hci_event.c:3067
       hci_event_packet+0x701/0x1310 net/bluetooth/hci_event.c:6439
       hci_rx_work+0x255/0xa10 net/bluetooth/hci_core.c:5190
       process_one_work+0x867/0xff0 kernel/workqueue.c:2310
       worker_thread+0xad7/0x12a0 kernel/workqueue.c:2457
       kthread+0x42e/0x520 kernel/kthread.c:334
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

other info that might help us debug this:

Chain exists of:
  rfcomm_mutex --> &hdev->lock --> hci_cb_list_lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(hci_cb_list_lock);
                               lock(&hdev->lock);
                               lock(hci_cb_list_lock);
  lock(rfcomm_mutex);

 *** DEADLOCK ***

4 locks held by kworker/u5:4/4330:
 #0: ffff88807e4b1938 ((wq_completion)hci0#2){+.+.}-{0:0}, at: process_one_work+0x75c/0xff0 kernel/workqueue.c:-1
 #1: ffffc9000321fd00 ((work_completion)(&hdev->rx_work)){+.+.}-{0:0}, at: process_one_work+0x79e/0xff0 kernel/workqueue.c:2285
 #2: ffff8880715d0478 (&hdev->lock){+.+.}-{3:3}, at: hci_auth_complete_evt+0xbc/0xbb0 net/bluetooth/hci_event.c:3035
 #3: ffffffff8d593e48 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_auth_cfm include/net/bluetooth/hci_core.h:1540 [inline]
 #3: ffffffff8d593e48 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_auth_complete_evt+0x308/0xbb0 net/bluetooth/hci_event.c:3067

stack backtrace:
CPU: 1 PID: 4330 Comm: kworker/u5:4 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: hci0 hci_rx_work
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 check_noncircular+0x296/0x330 kernel/locking/lockdep.c:2133
 check_prev_add kernel/locking/lockdep.c:3053 [inline]
 check_prevs_add kernel/locking/lockdep.c:3172 [inline]
 validate_chain kernel/locking/lockdep.c:3788 [inline]
 __lock_acquire+0x2c66/0x7b50 kernel/locking/lockdep.c:5012
 lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5625
 __mutex_lock_common+0x1e5/0x2400 kernel/locking/mutex.c:596
 __mutex_lock kernel/locking/mutex.c:729 [inline]
 mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
 rfcomm_security_cfm+0x95/0x780 net/bluetooth/rfcomm/core.c:2210
 hci_auth_cfm include/net/bluetooth/hci_core.h:1543 [inline]
 hci_auth_complete_evt+0x388/0xbb0 net/bluetooth/hci_event.c:3067
 hci_event_packet+0x701/0x1310 net/bluetooth/hci_event.c:6439
 hci_rx_work+0x255/0xa10 net/bluetooth/hci_core.c:5190
 process_one_work+0x867/0xff0 kernel/workqueue.c:2310
 worker_thread+0xad7/0x12a0 kernel/workqueue.c:2457
 kthread+0x42e/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>