======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.3.55/4657 is trying to acquire lock:
ffff888066264478 (&hdev->lock){+.+.}-{3:3}
, at: l2cap_chan_connect+0xfb/0xe20 net/bluetooth/l2cap_core.c:8232

but task is already holding lock:
ffffffff8d5b4408 (rfcomm_mutex){+.+.}-{3:3}, at: rfcomm_dlc_open+0x99/0x10c0 net/bluetooth/rfcomm/core.c:425

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (rfcomm_mutex){+.+.}-{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
       rfcomm_security_cfm+0x95/0x780 net/bluetooth/rfcomm/core.c:2216
       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

-> #1 (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

-> #0 (&hdev->lock){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3120 [inline]
       check_prevs_add kernel/locking/lockdep.c:3239 [inline]
       validate_chain kernel/locking/lockdep.c:3855 [inline]
       __lock_acquire+0x38f7/0x7d40 kernel/locking/lockdep.c:5120
       lock_acquire+0x19f/0x400 kernel/locking/lockdep.c:5737
       __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:8232
       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:419
       __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

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.3.55/4657:
 #0: ffffffff8d5b4408
 (rfcomm_mutex
){+.+.}-{3:3}, at: rfcomm_dlc_open+0x99/0x10c0 net/bluetooth/rfcomm/core.c:425

stack backtrace:
CPU: 0 PID: 4657 Comm: syz.3.55 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 check_noncircular+0x2f8/0x400 kernel/locking/lockdep.c:2178
 check_prev_add kernel/locking/lockdep.c:3120 [inline]
 check_prevs_add kernel/locking/lockdep.c:3239 [inline]
 validate_chain kernel/locking/lockdep.c:3855 [inline]
 __lock_acquire+0x38f7/0x7d40 kernel/locking/lockdep.c:5120
 lock_acquire+0x19f/0x400 kernel/locking/lockdep.c:5737
 __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:8232
 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:419
 __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
RIP: 0033:0x7f1212a58199
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:00007f1210c8f028 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00007f1212ce0090 RCX: 00007f1212a58199
RDX: 000000000000000a RSI: 00002000000000c0 RDI: 0000000000000005
RBP: 00007f1212aef0b8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1212ce0128 R14: 00007f1212ce0090 R15: 00007ffe481634a8
 </TASK>
hci1 dst 0e:aa:aa:aa:aa:aa
hci1 orig refcnt 14
hci1: conn ffff8880605c0000
hcon ffff8880605c0000 orig refcnt 0
hcon ffff8880605c0000
cache ffff888066265488, 0e:aa:aa:aa:aa:aa
hci1 opcode 0x0405 plen 13
hci1: skb len 16
hci1 hcon ffff8880605c0000
hcon ffff8880605c0000 conn ffff88802c173800 hchan ffff88806052d100
conn ffff88802c173800, psm 0x03, dcid 0x0000
chan ffff888060736000 orig refcnt 2
hcon ffff8880605c0000 orig refcnt 1
hcon ffff8880605c0000 orig refcnt 2
chan ffff888060736000 BT_BOUND -> BT_CONNECT
chan ffff888060736000 state BT_CONNECT timeout 4000
chan ffff888060736000 orig refcnt 3
hci1 orig refcnt 15
sk ffff88805f9d0000
ffff888060c46000
dlc ffff888060c46000 session ffff8880254c3500
session ffff8880254c3500 state 3
dlc ffff888060c46000 state 7 timeout 3000
sk ffff88805f9d1000
sock ffff888070441200, sk ffff8880738cb000
sock ffff888070441200, sk ffff8880738cb000
sk ffff8880738cb000 state 2 socket ffff888070441200
sk ffff8880738cb000 state 2 refcnt 2
sk ffff8880738cb000 dlc ffff88805f1b5400
ffff88805f1b5400
sock ffff888074ba8600, sk ffff88805f9d1000
sock ffff888074ba8600, sk ffff88805f9d1000
sk ffff88805f9d1000 state 5 socket ffff888074ba8600
dlc ffff888060c46000 state 7 dlci 6 err 0
dlc ffff888060c46000 state 7 dlci 6 err 0 session ffff8880254c3500
dlc ffff888060c46000 state 7
dlc ffff888060c46000 state 9 err 0
dlc ffff888060c46000 refcnt 2 session ffff8880254c3500
session ffff8880254c3500 state 3 timeout 200
sk ffff88805f9d1000 state 9 refcnt 2
sk ffff88805f9d1000 dlc ffff888060c46000
ffff888060c46000
sock ffff88807044da00, sk ffff8880288fd000
parent ffff8880288fd000 state BT_CONNECT
parent ffff8880288fd000
sock ffff88807044da00, sk ffff8880288fd000, how 2
Handling sock shutdown
chan ffff8880288fc000 orig refcnt 4
chan ffff8880288fc000 state BT_CONNECT
chan ffff8880288fc000 state BT_CONNECT
chan ffff8880288fc000 orig refcnt 5
chan ffff8880288fc000, err 0, state BT_CONNECT
chan ffff8880288fc000 state BT_CONNECT
chan ffff8880288fc000 orig refcnt 4
hcon ffff88805bbb4000 orig refcnt 1
chan ffff8880288fc000 orig refcnt 3
Sock shutdown complete err: 0
chan ffff8880288fc000 orig refcnt 2
sk ffff8880288fd000 state BT_CLOSED
chan ffff8880288fc000 orig refcnt 3
sk ffff8880288fd000
chan ffff8880288fc000 orig refcnt 2
chan ffff8880288fc000 orig refcnt 1
chan ffff8880288fc000