======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.2.3259/18075 is trying to acquire lock:
ffff88805d2040b8 (&hdev->lock){+.+.}-{3:3}, at: l2cap_chan_connect+0xfc/0xe30 net/bluetooth/l2cap_core.c:7195

but task is already holding lock:
ffffffff8e5651c8 (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_dev_activate+0x72/0xe0 net/bluetooth/rfcomm/tty.c:115
       tty_port_open+0x1d3/0x2a0 drivers/tty/tty_port.c:781
       rfcomm_tty_open+0xbc/0x480 net/bluetooth/rfcomm/tty.c:751
       tty_open+0x48c/0xcc0 drivers/tty/tty_io.c:2144
       chrdev_open+0x58c/0x600 fs/char_dev.c:414
       do_dentry_open+0x880/0x14b0 fs/open.c:929
       do_open fs/namei.c:3683 [inline]
       path_openat+0x284f/0x3270 fs/namei.c:3844
       do_filp_open+0x1f2/0x430 fs/namei.c:3871
       do_sys_openat2+0x134/0x1d0 fs/open.c:1422
       do_sys_open fs/open.c:1437 [inline]
       __do_sys_openat fs/open.c:1453 [inline]
       __se_sys_openat fs/open.c:1448 [inline]
       __x64_sys_openat+0x139/0x160 fs/open.c:1448
       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 ***

3 locks held by syz.2.3259/18075:
 #0: ffff88807d04c1c0 (&tty->legacy_mutex){+.+.}-{3:3}, at: tty_init_dev+0x74/0x4c0 drivers/tty/tty_io.c:1413
 #1: ffff88801c72e2a8 (&port->mutex){+.+.}-{3:3}, at: tty_port_open+0x129/0x2a0 drivers/tty/tty_port.c:776
 #2: ffffffff8e5651c8 (rfcomm_mutex){+.+.}-{3:3}, at: rfcomm_dlc_open+0x95/0xec0 net/bluetooth/rfcomm/core.c:429

stack backtrace:
CPU: 1 PID: 18075 Comm: syz.2.3259 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
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_dev_activate+0x72/0xe0 net/bluetooth/rfcomm/tty.c:115
 tty_port_open+0x1d3/0x2a0 drivers/tty/tty_port.c:781
 rfcomm_tty_open+0xbc/0x480 net/bluetooth/rfcomm/tty.c:751
 tty_open+0x48c/0xcc0 drivers/tty/tty_io.c:2144
 chrdev_open+0x58c/0x600 fs/char_dev.c:414
 do_dentry_open+0x880/0x14b0 fs/open.c:929
 do_open fs/namei.c:3683 [inline]
 path_openat+0x284f/0x3270 fs/namei.c:3844
 do_filp_open+0x1f2/0x430 fs/namei.c:3871
 do_sys_openat2+0x134/0x1d0 fs/open.c:1422
 do_sys_open fs/open.c:1437 [inline]
 __do_sys_openat fs/open.c:1453 [inline]
 __se_sys_openat fs/open.c:1448 [inline]
 __x64_sys_openat+0x139/0x160 fs/open.c:1448
 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: 0033:0x7fba29d9e199
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:00007fba2ace4028 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fba2a025fa0 RCX: 00007fba29d9e199
RDX: 0000000000000802 RSI: 0000200000000300 RDI: ffffffffffffff9c
RBP: 00007fba29e358e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fba2a026038 R14: 00007fba2a025fa0 R15: 00007ffe982a9768
 </TASK>