====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ kworker/u5:5/4960 is trying to acquire lock: ffff88805abb4120 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1744 [inline] ffff88805abb4120 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}, at: sco_conn_ready net/bluetooth/sco.c:1123 [inline] ffff88805abb4120 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}, at: sco_connect_cfm+0x149/0x8e0 net/bluetooth/sco.c:1214 but task is already holding lock: ffffffff8d591268 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_connect_cfm include/net/bluetooth/hci_core.h:1504 [inline] ffffffff8d591268 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_sync_conn_complete_evt+0x45e/0x9d0 net/bluetooth/hci_event.c:4578 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (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:3369 hci_event_packet+0x600/0x1310 net/bluetooth/hci_event.c:6456 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 (&hdev->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 sco_sock_connect+0x189/0x940 net/bluetooth/sco.c:602 __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 -> #0 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}: 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:5623 lock_sock_nested+0x44/0x100 net/core/sock.c:3259 lock_sock include/net/sock.h:1744 [inline] sco_conn_ready net/bluetooth/sco.c:1123 [inline] sco_connect_cfm+0x149/0x8e0 net/bluetooth/sco.c:1214 hci_connect_cfm include/net/bluetooth/hci_core.h:1507 [inline] hci_sync_conn_complete_evt+0x4be/0x9d0 net/bluetooth/hci_event.c:4578 hci_event_packet+0x8cf/0x1310 net/bluetooth/hci_event.c:6518 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 other info that might help us debug this: Chain exists of: sk_lock-AF_BLUETOOTH-BTPROTO_SCO --> &hdev->lock --> hci_cb_list_lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(hci_cb_list_lock); lock(&hdev->lock); lock(hci_cb_list_lock); lock(sk_lock-AF_BLUETOOTH-BTPROTO_SCO); *** DEADLOCK *** 4 locks held by kworker/u5:5/4960: #0: ffff88807dcb8138 ((wq_completion)hci4#2){+.+.}-{0:0}, at: process_one_work+0x75c/0xff0 kernel/workqueue.c:-1 #1: ffffc9000319fd00 ((work_completion)(&hdev->rx_work)){+.+.}-{0:0}, at: process_one_work+0x79e/0xff0 kernel/workqueue.c:2285 #2: ffff88807db00478 (&hdev->lock){+.+.}-{3:3}, at: hci_sync_conn_complete_evt+0xb8/0x9d0 net/bluetooth/hci_event.c:4498 #3: ffffffff8d591268 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_connect_cfm include/net/bluetooth/hci_core.h:1504 [inline] #3: ffffffff8d591268 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_sync_conn_complete_evt+0x45e/0x9d0 net/bluetooth/hci_event.c:4578 stack backtrace: CPU: 0 PID: 4960 Comm: kworker/u5:5 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026 Workqueue: hci4 hci_rx_work 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:5623 lock_sock_nested+0x44/0x100 net/core/sock.c:3259 lock_sock include/net/sock.h:1744 [inline] sco_conn_ready net/bluetooth/sco.c:1123 [inline] sco_connect_cfm+0x149/0x8e0 net/bluetooth/sco.c:1214 hci_connect_cfm include/net/bluetooth/hci_core.h:1507 [inline] hci_sync_conn_complete_evt+0x4be/0x9d0 net/bluetooth/hci_event.c:4578 hci_event_packet+0x8cf/0x1310 net/bluetooth/hci_event.c:6518 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 Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection Bluetooth: hci4: Ignoring connect complete event for existing connection