====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.2.374/5898 is trying to acquire lock: ffff888058d08478 (&hdev->lock){+.+.}-{3:3}, at: l2cap_chan_connect+0xfb/0xe20 net/bluetooth/l2cap_core.c:8205 but task is already holding lock: ffffffff8d5b37c8 (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:2210 hci_encrypt_cfm+0x363/0x4d0 include/net/bluetooth/hci_core.h:1583 hci_encrypt_change_evt+0x62d/0xdd0 net/bluetooth/hci_event.c:3243 hci_event_packet+0x67e/0x1310 net/bluetooth/hci_event.c:6447 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:3053 [inline] check_prevs_add kernel/locking/lockdep.c:3172 [inline] validate_chain kernel/locking/lockdep.c:3788 [inline] __lock_acquire+0x2c66/0x7b50 kernel/locking/lockdep.c:5012 lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5625 __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:8205 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:421 __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.2.374/5898: #0: ffffffff8d5b37c8 (rfcomm_mutex){+.+.}-{3:3}, at: rfcomm_dlc_open+0x99/0x10c0 net/bluetooth/rfcomm/core.c:425 stack backtrace: CPU: 1 PID: 5898 Comm: syz.2.374 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026 Call Trace: dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106 check_noncircular+0x296/0x330 kernel/locking/lockdep.c:2133 check_prev_add kernel/locking/lockdep.c:3053 [inline] check_prevs_add kernel/locking/lockdep.c:3172 [inline] validate_chain kernel/locking/lockdep.c:3788 [inline] __lock_acquire+0x2c66/0x7b50 kernel/locking/lockdep.c:5012 lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5625 __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:8205 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:421 __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: 0033:0x7f84b4c0f159 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:00007f84b2e67028 EFLAGS: 00000246 ORIG_RAX: 000000000000002a RAX: ffffffffffffffda RBX: 00007f84b4e96fa0 RCX: 00007f84b4c0f159 RDX: 000000000000000a RSI: 0000200000000040 RDI: 0000000000000004 RBP: 00007f84b4ca606b R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f84b4e97038 R14: 00007f84b4e96fa0 R15: 00007fff9f38bf48