====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.2.1356/9688 is trying to acquire lock: ffff0000f4f88428 (&hdev->lock){+.+.}-{3:3}, at: l2cap_chan_connect+0xd0/0xba0 net/bluetooth/l2cap_core.c:7308 but task is already holding lock: ffff800017bc9128 (rfcomm_mutex){+.+.}-{3:3}, at: rfcomm_dlc_open+0xa8/0xcf4 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+0x1a0/0x1f3c kernel/locking/mutex.c:603 __mutex_lock kernel/locking/mutex.c:747 [inline] mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799 rfcomm_security_cfm+0x9c/0x674 net/bluetooth/rfcomm/core.c:2216 hci_auth_cfm include/net/bluetooth/hci_core.h:1857 [inline] hci_auth_complete_evt+0x2e4/0xa68 net/bluetooth/hci_event.c:3494 hci_event_func net/bluetooth/hci_event.c:7314 [inline] hci_event_packet+0x698/0xe60 net/bluetooth/hci_event.c:7366 hci_rx_work+0x310/0xa70 net/bluetooth/hci_core.c:4006 process_one_work+0x7e4/0x13bc kernel/workqueue.c:2292 worker_thread+0x8cc/0xfe8 kernel/workqueue.c:2439 kthread+0x254/0x2e0 kernel/kthread.c:376 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850 -> #1 (hci_cb_list_lock){+.+.}-{3:3}: __mutex_lock_common+0x1a0/0x1f3c kernel/locking/mutex.c:603 __mutex_lock kernel/locking/mutex.c:747 [inline] mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799 hci_connect_cfm include/net/bluetooth/hci_core.h:1818 [inline] hci_remote_features_evt+0x410/0x840 net/bluetooth/hci_event.c:3734 hci_event_func net/bluetooth/hci_event.c:7314 [inline] hci_event_packet+0x698/0xe60 net/bluetooth/hci_event.c:7366 hci_rx_work+0x310/0xa70 net/bluetooth/hci_core.c:4006 process_one_work+0x7e4/0x13bc kernel/workqueue.c:2292 worker_thread+0x8cc/0xfe8 kernel/workqueue.c:2439 kthread+0x254/0x2e0 kernel/kthread.c:376 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850 -> #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+0x3504/0x7280 kernel/locking/lockdep.c:5171 lock_acquire+0x210/0x63c kernel/locking/lockdep.c:5790 __mutex_lock_common+0x1a0/0x1f3c kernel/locking/mutex.c:603 __mutex_lock kernel/locking/mutex.c:747 [inline] mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799 l2cap_chan_connect+0xd0/0xba0 net/bluetooth/l2cap_core.c:7308 l2cap_sock_connect+0x414/0x600 net/bluetooth/l2cap_sock.c:257 kernel_connect+0x124/0x190 net/socket.c:3555 rfcomm_session_create net/bluetooth/rfcomm/core.c:807 [inline] __rfcomm_dlc_open net/bluetooth/rfcomm/core.c:384 [inline] rfcomm_dlc_open+0x4f4/0xcf4 net/bluetooth/rfcomm/core.c:427 rfcomm_sock_connect+0x25c/0x57c net/bluetooth/rfcomm/sock.c:419 __sys_connect_file net/socket.c:2011 [inline] __sys_connect+0x28c/0x2b4 net/socket.c:2028 __do_sys_connect net/socket.c:2038 [inline] __se_sys_connect net/socket.c:2035 [inline] __arm64_sys_connect+0x7c/0x94 net/socket.c:2035 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204 el0_svc+0x58/0x12c arch/arm64/kernel/entry-common.c:637 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585 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.2.1356/9688: #0: ffff800017bc9128 (rfcomm_mutex){+.+.}-{3:3}, at: rfcomm_dlc_open+0xa8/0xcf4 net/bluetooth/rfcomm/core.c:425 stack backtrace: CPU: 1 PID: 9688 Comm: syz.2.1356 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/23/2026 dump_backtrace(regs = 0000000000000000 tsk = 0000000000000000) Call trace: dump_backtrace+0x1c4/0x1f0 arch/arm64/kernel/stacktrace.c:158 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165 __dump_stack+0x30/0x40 lib/dump_stack.c:88 dump_stack_lvl+0xf4/0x15c lib/dump_stack.c:106 dump_stack+0x1c/0x5c lib/dump_stack.c:113 print_circular_bug+0x148/0x1b0 kernel/locking/lockdep.c:2088 check_noncircular+0x290/0x370 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+0x3504/0x7280 kernel/locking/lockdep.c:5171 lock_acquire+0x210/0x63c kernel/locking/lockdep.c:5790 __mutex_lock_common+0x1a0/0x1f3c kernel/locking/mutex.c:603 __mutex_lock kernel/locking/mutex.c:747 [inline] mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799 l2cap_chan_connect+0xd0/0xba0 net/bluetooth/l2cap_core.c:7308 l2cap_sock_connect+0x414/0x600 net/bluetooth/l2cap_sock.c:257 kernel_connect+0x124/0x190 net/socket.c:3555 rfcomm_session_create net/bluetooth/rfcomm/core.c:807 [inline] __rfcomm_dlc_open net/bluetooth/rfcomm/core.c:384 [inline] rfcomm_dlc_open+0x4f4/0xcf4 net/bluetooth/rfcomm/core.c:427 rfcomm_sock_connect+0x25c/0x57c net/bluetooth/rfcomm/sock.c:419 __sys_connect_file net/socket.c:2011 [inline] __sys_connect+0x28c/0x2b4 net/socket.c:2028 __do_sys_connect net/socket.c:2038 [inline] __se_sys_connect net/socket.c:2035 [inline] __arm64_sys_connect+0x7c/0x94 net/socket.c:2035 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204 el0_svc+0x58/0x12c arch/arm64/kernel/entry-common.c:637 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585 hci3: dst 0e:aa:aa:aa:aa:aa hci3: dst 0e:aa:aa:aa:aa:aa handle 0x0f00 hci3 orig refcnt 13 hci3: conn 00000000565731ab hcon 00000000565731ab orig refcnt 0 hcon 00000000565731ab cache 00000000c3d6a361, 0e:aa:aa:aa:aa:aa hci3 opcode 0x0405 plen 13 hci3: skb len 16 hci3 hcon 00000000565731ab hcon 00000000565731ab conn 00000000b84d03ae hchan 00000000168111f9 conn 00000000b84d03ae, psm 0x03, dcid 0x0000 chan 00000000eadd4d84 orig refcnt 1 hcon 00000000565731ab orig refcnt 1 hcon 00000000565731ab orig refcnt 2 chan 00000000eadd4d84 BT_BOUND -> BT_CONNECT chan 00000000eadd4d84 state BT_CONNECT timeout 4000 chan 00000000eadd4d84 orig refcnt 2 hci3 orig refcnt 14 sk 000000004bf9b17a 00000000012be94a dlc 00000000012be94a session 000000001f46ef1f session 000000001f46ef1f state 3 dlc 00000000012be94a state 7 timeout 3000 sk 000000007f8442b4 sock 00000000977f1dbe, sk 000000007f8442b4 sock 00000000977f1dbe, sk 000000007f8442b4 sk 000000007f8442b4 state 5 socket 00000000977f1dbe dlc 00000000012be94a state 7 dlci 6 err 0 dlc 00000000012be94a state 7 dlci 6 err 0 session 000000001f46ef1f dlc 00000000012be94a state 7 dlc 00000000012be94a state 9 err 0 dlc 00000000012be94a refcnt 2 session 000000001f46ef1f session 000000001f46ef1f state 3 timeout 200 sk 000000007f8442b4 state 9 refcnt 2 sk 000000007f8442b4 dlc 00000000012be94a 00000000012be94a kcov: kcov_task_exit: t = ffff0000dea41c00, kcov->t = ffff0000dea41c00