======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.4.1890/15032 is trying to acquire lock:
ffff888067f400b8 (&hdev->lock){+.+.}-{3:3}, at: l2cap_chan_connect+0xfc/0xe30 net/bluetooth/l2cap_core.c:7171

but task is already holding lock:
ffffffff8e562248 (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:2214
       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:3134 [inline]
       check_prevs_add kernel/locking/lockdep.c:3253 [inline]
       validate_chain kernel/locking/lockdep.c:3869 [inline]
       __lock_acquire+0x37ef/0x7d80 kernel/locking/lockdep.c:5137
       lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5756
       __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:7171
       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:421
       __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.4.1890/15032:
 #0: ffffffff8e562248 (rfcomm_mutex){+.+.}-{3:3}, at: rfcomm_dlc_open+0x95/0xec0 net/bluetooth/rfcomm/core.c:429

stack backtrace:
CPU: 0 PID: 15032 Comm: syz.4.1890 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:2187
 check_prev_add kernel/locking/lockdep.c:3134 [inline]
 check_prevs_add kernel/locking/lockdep.c:3253 [inline]
 validate_chain kernel/locking/lockdep.c:3869 [inline]
 __lock_acquire+0x37ef/0x7d80 kernel/locking/lockdep.c:5137
 lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5756
 __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:7171
 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:421
 __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: 0033:0x7f11c379e159
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:00007f11c467a028 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00007f11c3a26090 RCX: 00007f11c379e159
RDX: 0000000000000014 RSI: 0000200000000200 RDI: 0000000000000009
RBP: 00007f11c383506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f11c3a26128 R14: 00007f11c3a26090 R15: 00007ffee0fd9bf8
 </TASK>
hci0: dst 00:00:00:00:f8:00
hci0: dst 00:00:00:00:f8:00 handle 0x0f00
hci0 orig refcnt 13
hci0: conn ffff888065d04000
hcon ffff888065d04000 orig refcnt 0
hci0 hcon ffff888065d04000
hcon ffff888065d04000 conn ffff888079cd7800 hchan ffff88802f8a0300
conn ffff888079cd7800, psm 0x03, dcid 0x0000
chan ffff88807a65c000 orig refcnt 1
hcon ffff888065d04000 orig refcnt 1
hcon ffff888065d04000 orig refcnt 2
chan ffff88807a65c000 BT_BOUND -> BT_CONNECT
chan ffff88807a65c000 state BT_CONNECT timeout 4000
chan ffff88807a65c000 orig refcnt 2
hci0 orig refcnt 14
sk ffff88807a65a000
ffff888068e83000
dlc ffff888068e83000 session ffff88802fa31b00
session ffff88802fa31b00 state 3
dlc ffff888068e83000 state 7 timeout 3000
sk ffff88807a65f000
kcov: kcov_task_exit: t = ffff8880187ebc00, kcov->t = ffff8880187ebc00