====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ kworker/u5:1/4330 is trying to acquire lock: ffff0000f1694428 (&hdev->lock){+.+.}-{3:3}, at: hci_le_conn_update+0xbc/0x290 net/bluetooth/hci_conn.c:607 but task is already holding lock: ffff8000210d7c40 ((work_completion)(&conn->pending_rx_work)){+.+.}-{0:0}, at: process_one_work+0x6e8/0x13bc kernel/workqueue.c:2267 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 ((work_completion)(&conn->pending_rx_work)){+.+.}-{0:0}: __flush_work+0x10c/0x1ec kernel/workqueue.c:3072 __cancel_work_timer+0x2f8/0x450 kernel/workqueue.c:3163 cancel_work_sync+0x24/0x38 kernel/workqueue.c:3199 l2cap_conn_del+0x80/0x564 net/bluetooth/l2cap_core.c:1814 l2cap_disconn_cfm+0x90/0xdc net/bluetooth/l2cap_core.c:7632 hci_disconn_cfm include/net/bluetooth/hci_core.h:1836 [inline] hci_conn_hash_flush+0x108/0x26c net/bluetooth/hci_conn.c:2563 hci_dev_close_sync+0x810/0xff0 net/bluetooth/hci_sync.c:5312 hci_dev_do_close net/bluetooth/hci_core.c:523 [inline] hci_unregister_dev+0x20c/0x4c8 net/bluetooth/hci_core.c:2718 vhci_release+0x7c/0xcc drivers/bluetooth/hci_vhci.c:565 __fput+0x1b4/0x7b0 fs/file_table.c:320 ____fput+0x20/0x30 fs/file_table.c:348 task_work_run+0x1f4/0x280 kernel/task_work.c:203 exit_task_work include/linux/task_work.h:39 [inline] do_exit+0x54c/0x19ac kernel/exit.c:887 do_group_exit+0x198/0x238 kernel/exit.c:1030 __do_sys_exit_group kernel/exit.c:1041 [inline] __se_sys_exit_group kernel/exit.c:1039 [inline] __wake_up_parent+0x0/0x60 kernel/exit.c:1039 __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+0x58/0x128 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 -> #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:3095 [inline] check_prevs_add kernel/locking/lockdep.c:3214 [inline] validate_chain kernel/locking/lockdep.c:3830 [inline] __lock_acquire+0x2808/0x6634 kernel/locking/lockdep.c:5063 lock_acquire+0x20c/0x638 kernel/locking/lockdep.c:5678 __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_le_conn_update+0xbc/0x290 net/bluetooth/hci_conn.c:607 l2cap_conn_param_update_req net/bluetooth/l2cap_core.c:4786 [inline] l2cap_le_sig_cmd net/bluetooth/l2cap_core.c:5654 [inline] l2cap_le_sig_channel net/bluetooth/l2cap_core.c:5731 [inline] l2cap_recv_frame+0xa538/0xd1a4 net/bluetooth/l2cap_core.c:7146 process_pending_rx+0x48/0x9c net/bluetooth/l2cap_core.c:7164 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 other info that might help us debug this: Chain exists of: &hdev->lock --> hci_cb_list_lock --> (work_completion)(&conn->pending_rx_work) Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock((work_completion)(&conn->pending_rx_work)); lock(hci_cb_list_lock); lock((work_completion)(&conn->pending_rx_work)); lock(&hdev->lock); *** DEADLOCK *** 2 locks held by kworker/u5:1/4330: #0: ffff0000ca733938 ((wq_completion)hci4#2){+.+.}-{0:0}, at: process_one_work+0x69c/0x13bc kernel/workqueue.c:-1 #1: ffff8000210d7c40 ((work_completion)(&conn->pending_rx_work)){+.+.}-{0:0}, at: process_one_work+0x6e8/0x13bc kernel/workqueue.c:2267 stack backtrace: CPU: 0 PID: 4330 Comm: kworker/u5:1 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/14/2026 Workqueue: hci4 process_pending_rx 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:2048 check_noncircular+0x264/0x2f8 kernel/locking/lockdep.c:2170 check_prev_add kernel/locking/lockdep.c:3095 [inline] check_prevs_add kernel/locking/lockdep.c:3214 [inline] validate_chain kernel/locking/lockdep.c:3830 [inline] __lock_acquire+0x2808/0x6634 kernel/locking/lockdep.c:5063 lock_acquire+0x20c/0x638 kernel/locking/lockdep.c:5678 __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_le_conn_update+0xbc/0x290 net/bluetooth/hci_conn.c:607 l2cap_conn_param_update_req net/bluetooth/l2cap_core.c:4786 [inline] l2cap_le_sig_cmd net/bluetooth/l2cap_core.c:5654 [inline] l2cap_le_sig_channel net/bluetooth/l2cap_core.c:5731 [inline] l2cap_recv_frame+0xa538/0xd1a4 net/bluetooth/l2cap_core.c:7146 process_pending_rx+0x48/0x9c net/bluetooth/l2cap_core.c:7164 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 Bluetooth: hci4: link tx timeout Bluetooth: hci4: killing stalled connection 10:aa:aa:aa:aa:aa Bluetooth: hci4: link tx timeout Bluetooth: hci4: killing stalled connection 11:aa:aa:aa:aa:aa Bluetooth: hci4: link tx timeout Bluetooth: hci4: killing stalled connection 10:aa:aa:aa:aa:aa Bluetooth: hci4: link tx timeout Bluetooth: hci4: killing stalled connection 11:aa:aa:aa:aa:aa Bluetooth: hci1: command 0x0409 tx timeout