======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.17/5920 is trying to acquire lock:
ffff8880366740b8 (&hdev->lock){+.+.}-{4:4}, at: l2cap_chan_connect+0xac/0x2110 net/bluetooth/l2cap_core.c:7281

but task is already holding lock:
ffffffff90f82800 (rfcomm_mutex){+.+.}-{4:4}, at: rfcomm_dlc_open+0x92/0xac0 net/bluetooth/rfcomm/core.c:426

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (rfcomm_mutex){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5942 [inline]
       lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       rfcomm_security_cfm+0x3f/0x4b0 net/bluetooth/rfcomm/core.c:2222
       hci_auth_cfm include/net/bluetooth/hci_core.h:2202 [inline]
       hci_auth_complete_evt+0x811/0x1180 net/bluetooth/hci_event.c:3554
       hci_event_func net/bluetooth/hci_event.c:7887 [inline]
       hci_event_packet+0x8e9/0xcd0 net/bluetooth/hci_event.c:7938
       hci_rx_work+0x451/0xfc0 net/bluetooth/hci_core.c:4053
       process_one_work+0xac7/0x1b10 kernel/workqueue.c:3396
       process_scheduled_works kernel/workqueue.c:3479 [inline]
       worker_thread+0x5ef/0xe50 kernel/workqueue.c:3560
       kthread+0x373/0x450 kernel/kthread.c:436
       ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #1 (hci_cb_list_lock){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5942 [inline]
       lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       hci_connect_cfm include/net/bluetooth/hci_core.h:2163 [inline]
       hci_remote_features_evt+0x485/0x9b0 net/bluetooth/hci_event.c:3786
       hci_event_func net/bluetooth/hci_event.c:7887 [inline]
       hci_event_packet+0x8e9/0xcd0 net/bluetooth/hci_event.c:7938
       hci_rx_work+0x451/0xfc0 net/bluetooth/hci_core.c:4053
       process_one_work+0xac7/0x1b10 kernel/workqueue.c:3396
       process_scheduled_works kernel/workqueue.c:3479 [inline]
       worker_thread+0x5ef/0xe50 kernel/workqueue.c:3560
       kthread+0x373/0x450 kernel/kthread.c:436
       ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #0 (&hdev->lock){+.+.}-{4:4}:
       check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3209
       check_prevs_add kernel/locking/lockdep.c:3328 [inline]
       validate_chain kernel/locking/lockdep.c:3952 [inline]
       __lock_acquire+0x1528/0x1f40 kernel/locking/lockdep.c:5288
       lock_acquire kernel/locking/lockdep.c:5942 [inline]
       lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       l2cap_chan_connect+0xac/0x2110 net/bluetooth/l2cap_core.c:7281
       l2cap_sock_connect+0x37a/0x770 net/bluetooth/l2cap_sock.c:255
       kernel_connect+0x107/0x160 net/socket.c:3755
       rfcomm_session_create net/bluetooth/rfcomm/core.c:808 [inline]
       __rfcomm_dlc_open net/bluetooth/rfcomm/core.c:385 [inline]
       rfcomm_dlc_open+0x838/0xac0 net/bluetooth/rfcomm/core.c:428
       rfcomm_sock_connect+0x42c/0x690 net/bluetooth/rfcomm/sock.c:419
       connect_socket net/socket.c:2141 [inline]
       connect_socket net/socket.c:2131 [inline]
       __sys_connect_file+0x146/0x1a0 net/socket.c:2166
       __sys_connect+0x141/0x170 net/socket.c:2183
       __do_sys_connect net/socket.c:2189 [inline]
       __se_sys_connect net/socket.c:2186 [inline]
       __x64_sys_connect+0x72/0xb0 net/socket.c:2186
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

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 ***

locks held by syz.0.17/5920: 1, last CPU#1:
 #0: ffffffff90f82800 (rfcomm_mutex){+.+.}-{4:4}, at: rfcomm_dlc_open+0x92/0xac0 net/bluetooth/rfcomm/core.c:426

stack backtrace:
CPU: 1 UID: 0 PID: 5920 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_circular_bug.cold+0x178/0x1be kernel/locking/lockdep.c:2087
 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2219
 check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3209
 check_prevs_add kernel/locking/lockdep.c:3328 [inline]
 validate_chain kernel/locking/lockdep.c:3952 [inline]
 __lock_acquire+0x1528/0x1f40 kernel/locking/lockdep.c:5288
 lock_acquire kernel/locking/lockdep.c:5942 [inline]
 lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
 __mutex_lock_common kernel/locking/mutex.c:646 [inline]
 __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
 l2cap_chan_connect+0xac/0x2110 net/bluetooth/l2cap_core.c:7281
 l2cap_sock_connect+0x37a/0x770 net/bluetooth/l2cap_sock.c:255
 kernel_connect+0x107/0x160 net/socket.c:3755
 rfcomm_session_create net/bluetooth/rfcomm/core.c:808 [inline]
 __rfcomm_dlc_open net/bluetooth/rfcomm/core.c:385 [inline]
 rfcomm_dlc_open+0x838/0xac0 net/bluetooth/rfcomm/core.c:428
 rfcomm_sock_connect+0x42c/0x690 net/bluetooth/rfcomm/sock.c:419
 connect_socket net/socket.c:2141 [inline]
 connect_socket net/socket.c:2131 [inline]
 __sys_connect_file+0x146/0x1a0 net/socket.c:2166
 __sys_connect+0x141/0x170 net/socket.c:2183
 __do_sys_connect net/socket.c:2189 [inline]
 __se_sys_connect net/socket.c:2186 [inline]
 __x64_sys_connect+0x72/0xb0 net/socket.c:2186
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb857d9e159
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:00007ffc289ba9f8 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00007fb858025fa0 RCX: 00007fb857d9e159
RDX: 000000000000000a RSI: 00002000000003c0 RDI: 0000000000000004
RBP: 00007fb857e3506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb858025fac R14: 00007fb858025fa0 R15: 00007fb858025fa0
 </TASK>