======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
kworker/u5:3/4377 is trying to acquire lock:
ffff0000cace4428 (&hdev->lock){+.+.}-{3:3}, at: hci_le_conn_update+0xbc/0x290 net/bluetooth/hci_conn.c:607

but task is already holding lock:
ffff800020c67c40 ((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:1817
       l2cap_disconn_cfm+0x90/0xdc net/bluetooth/l2cap_core.c:7656
       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+0x810/0x1004 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+0x58/0x12c 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

-> #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
       hci_le_conn_update+0xbc/0x290 net/bluetooth/hci_conn.c:607
       l2cap_conn_param_update_req net/bluetooth/l2cap_core.c:4796 [inline]
       l2cap_le_sig_cmd net/bluetooth/l2cap_core.c:5665 [inline]
       l2cap_le_sig_channel net/bluetooth/l2cap_core.c:5742 [inline]
       l2cap_recv_frame+0xa4b4/0xcf94 net/bluetooth/l2cap_core.c:7170
       process_pending_rx+0x48/0x9c net/bluetooth/l2cap_core.c:7188
       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/u5:3/4377:
 #0: ffff0000d8746938 ((wq_completion)hci0#2){+.+.}-{0:0}, at: process_one_work+0x69c/0x13bc kernel/workqueue.c:-1
 #1: ffff800020c67c40 ((work_completion)(&conn->pending_rx_work)){+.+.}-{0:0}, at: process_one_work+0x6e8/0x13bc kernel/workqueue.c:2267

stack backtrace:
CPU: 0 PID: 4377 Comm: kworker/u5:3 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/23/2026
Workqueue: hci0 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: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
 hci_le_conn_update+0xbc/0x290 net/bluetooth/hci_conn.c:607
 l2cap_conn_param_update_req net/bluetooth/l2cap_core.c:4796 [inline]
 l2cap_le_sig_cmd net/bluetooth/l2cap_core.c:5665 [inline]
 l2cap_le_sig_channel net/bluetooth/l2cap_core.c:5742 [inline]
 l2cap_recv_frame+0xa4b4/0xcf94 net/bluetooth/l2cap_core.c:7170
 process_pending_rx+0x48/0x9c net/bluetooth/l2cap_core.c:7188
 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: hci0: command 0x2016 tx timeout
Bluetooth: hci2: command 0x0409 tx timeout
Bluetooth: hci2: command 0x041b tx timeout
Bluetooth: hci0: command 0x2016 tx timeout
Bluetooth: hci0: command 0x2016 tx timeout
Bluetooth: hci0: command 0x2016 tx timeout