======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.17/5930 is trying to acquire lock:
ffff8880227380b8 (&hdev->lock){+.+.}-{3:3}, at: l2cap_chan_connect+0xfc/0xe30 net/bluetooth/l2cap_core.c:7195

but task is already holding lock:
ffffffff8f364ac8 (rfcomm_mutex){+.+.}-{3:3}, at: rfcomm_dlc_open+0x95/0xec0 net/bluetooth/rfcomm/core.c:429

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (rfcomm_mutex){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747
       rfcomm_security_cfm+0x41/0x550 net/bluetooth/rfcomm/core.c:2220
       hci_encrypt_cfm+0x363/0x4d0 include/net/bluetooth/hci_core.h:2080
       hci_encrypt_change_evt+0x5c3/0xe30 net/bluetooth/hci_event.c:3590
       hci_event_func net/bluetooth/hci_event.c:7500 [inline]
       hci_event_packet+0x807/0x1280 net/bluetooth/hci_event.c:7552
       hci_rx_work+0x43a/0xd60 net/bluetooth/hci_core.c:4017
       process_one_work kernel/workqueue.c:2657 [inline]
       process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734
       worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815
       kthread+0x2fa/0x390 kernel/kthread.c:388
       ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
       ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293

-> #1 (hci_cb_list_lock){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747
       hci_connect_cfm include/net/bluetooth/hci_core.h:2001 [inline]
       hci_remote_features_evt+0x535/0x900 net/bluetooth/hci_event.c:3719
       hci_event_func net/bluetooth/hci_event.c:7500 [inline]
       hci_event_packet+0x807/0x1280 net/bluetooth/hci_event.c:7552
       hci_rx_work+0x43a/0xd60 net/bluetooth/hci_core.c:4017
       process_one_work kernel/workqueue.c:2657 [inline]
       process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734
       worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815
       kthread+0x2fa/0x390 kernel/kthread.c:388
       ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
       ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293

-> #0 (&hdev->lock){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3162 [inline]
       check_prevs_add kernel/locking/lockdep.c:3281 [inline]
       validate_chain kernel/locking/lockdep.c:3897 [inline]
       __lock_acquire+0x3a07/0x7eb0 kernel/locking/lockdep.c:5171
       lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5790
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747
       l2cap_chan_connect+0xfc/0xe30 net/bluetooth/l2cap_core.c:7195
       l2cap_sock_connect+0x586/0x760 net/bluetooth/l2cap_sock.c:257
       kernel_connect+0x142/0x1c0 net/socket.c:3636
       rfcomm_session_create net/bluetooth/rfcomm/core.c:811 [inline]
       __rfcomm_dlc_open net/bluetooth/rfcomm/core.c:388 [inline]
       rfcomm_dlc_open+0xa1f/0xec0 net/bluetooth/rfcomm/core.c:431
       rfcomm_sock_connect+0x2ed/0x600 net/bluetooth/rfcomm/sock.c:419
       __sys_connect_file net/socket.c:2057 [inline]
       __sys_connect+0x3da/0x470 net/socket.c:2074
       __do_sys_connect net/socket.c:2084 [inline]
       __se_sys_connect net/socket.c:2081 [inline]
       __x64_sys_connect+0x7a/0x90 net/socket.c:2081
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

other info that might help us debug this:

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

 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

1 lock held by syz.0.17/5930:
 #0: ffffffff8f364ac8 (rfcomm_mutex){+.+.}-{3:3}, at: rfcomm_dlc_open+0x95/0xec0 net/bluetooth/rfcomm/core.c:429

stack backtrace:
CPU: 0 PID: 5930 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 check_noncircular+0x2fc/0x400 kernel/locking/lockdep.c:2215
 check_prev_add kernel/locking/lockdep.c:3162 [inline]
 check_prevs_add kernel/locking/lockdep.c:3281 [inline]
 validate_chain kernel/locking/lockdep.c:3897 [inline]
 __lock_acquire+0x3a07/0x7eb0 kernel/locking/lockdep.c:5171
 lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5790
 __mutex_lock_common kernel/locking/mutex.c:603 [inline]
 __mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747
 l2cap_chan_connect+0xfc/0xe30 net/bluetooth/l2cap_core.c:7195
 l2cap_sock_connect+0x586/0x760 net/bluetooth/l2cap_sock.c:257
 kernel_connect+0x142/0x1c0 net/socket.c:3636
 rfcomm_session_create net/bluetooth/rfcomm/core.c:811 [inline]
 __rfcomm_dlc_open net/bluetooth/rfcomm/core.c:388 [inline]
 rfcomm_dlc_open+0xa1f/0xec0 net/bluetooth/rfcomm/core.c:431
 rfcomm_sock_connect+0x2ed/0x600 net/bluetooth/rfcomm/sock.c:419
 __sys_connect_file net/socket.c:2057 [inline]
 __sys_connect+0x3da/0x470 net/socket.c:2074
 __do_sys_connect net/socket.c:2084 [inline]
 __se_sys_connect net/socket.c:2081 [inline]
 __x64_sys_connect+0x7a/0x90 net/socket.c:2081
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f73e979e1d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd99bfc2b8 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00007f73e9a25fa0 RCX: 00007f73e979e1d9
RDX: 000000000000000a RSI: 0000200000000000 RDI: 0000000000000004
RBP: 00007f73e9835888 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f73e9a25fac R14: 00007f73e9a25fa0 R15: 00007f73e9a25fa0
 </TASK>