====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ kworker/u5:4/5786 is trying to acquire lock: ffff8880643300b8 (&hdev->lock){+.+.}-{3:3}, at: hci_le_conn_update+0xd0/0x320 net/bluetooth/hci_conn.c:502 but task is already holding lock: ffff88807f0ca338 (&conn->lock#2){+.+.}-{3:3}, at: l2cap_recv_acldata+0xe2/0x11a0 net/bluetooth/l2cap_core.c:7731 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&conn->lock#2){+.+.}-{3:3}: __mutex_lock_common kernel/locking/mutex.c:603 [inline] __mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747 l2cap_conn_ready net/bluetooth/l2cap_core.c:1654 [inline] l2cap_connect_cfm+0x663/0x1160 net/bluetooth/l2cap_core.c:7498 hci_connect_cfm include/net/bluetooth/hci_core.h:2004 [inline] hci_remote_features_evt+0x59b/0x900 net/bluetooth/hci_event.c:3719 hci_event_func net/bluetooth/hci_event.c:7500 [inline] hci_event_packet+0x807/0x1280 net/bluetooth/hci_event.c:7552 hci_rx_work+0x43a/0xd60 net/bluetooth/hci_core.c:4017 process_one_work kernel/workqueue.c:2657 [inline] process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815 kthread+0x2fa/0x390 kernel/kthread.c:388 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293 -> #1 (hci_cb_list_lock){+.+.}-{3:3}: __mutex_lock_common kernel/locking/mutex.c:603 [inline] __mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747 hci_connect_cfm include/net/bluetooth/hci_core.h:2001 [inline] hci_remote_features_evt+0x535/0x900 net/bluetooth/hci_event.c:3719 hci_event_func net/bluetooth/hci_event.c:7500 [inline] hci_event_packet+0x807/0x1280 net/bluetooth/hci_event.c:7552 hci_rx_work+0x43a/0xd60 net/bluetooth/hci_core.c:4017 process_one_work kernel/workqueue.c:2657 [inline] process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815 kthread+0x2fa/0x390 kernel/kthread.c:388 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293 -> #0 (&hdev->lock){+.+.}-{3:3}: check_prev_add kernel/locking/lockdep.c:3134 [inline] check_prevs_add kernel/locking/lockdep.c:3253 [inline] validate_chain kernel/locking/lockdep.c:3869 [inline] __lock_acquire+0x37ef/0x7d80 kernel/locking/lockdep.c:5137 lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5756 __mutex_lock_common kernel/locking/mutex.c:603 [inline] __mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747 hci_le_conn_update+0xd0/0x320 net/bluetooth/hci_conn.c:502 l2cap_conn_param_update_req net/bluetooth/l2cap_core.c:4740 [inline] l2cap_le_sig_cmd net/bluetooth/l2cap_core.c:5558 [inline] l2cap_le_sig_channel net/bluetooth/l2cap_core.c:5635 [inline] l2cap_recv_frame+0xce07/0x10090 net/bluetooth/l2cap_core.c:7040 l2cap_recv_acldata+0x50b/0x11a0 net/bluetooth/l2cap_core.c:7756 hci_acldata_packet net/bluetooth/hci_core.c:3784 [inline] hci_rx_work+0x545/0xd60 net/bluetooth/hci_core.c:4022 process_one_work kernel/workqueue.c:2657 [inline] process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815 kthread+0x2fa/0x390 kernel/kthread.c:388 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293 other info that might help us debug this: Chain exists of: &hdev->lock --> hci_cb_list_lock --> &conn->lock#2 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&conn->lock#2); lock(hci_cb_list_lock); lock(&conn->lock#2); lock(&hdev->lock); *** DEADLOCK *** 3 locks held by kworker/u5:4/5786: #0: ffff88802e0f8138 ((wq_completion)hci2#2){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline] #0: ffff88802e0f8138 ((wq_completion)hci2#2){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734 #1: ffffc900046dfd00 ((work_completion)(&hdev->rx_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline] #1: ffffc900046dfd00 ((work_completion)(&hdev->rx_work)){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734 #2: ffff88807f0ca338 (&conn->lock#2){+.+.}-{3:3}, at: l2cap_recv_acldata+0xe2/0x11a0 net/bluetooth/l2cap_core.c:7731 stack backtrace: CPU: 1 PID: 5786 Comm: kworker/u5:4 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026 Workqueue: hci2 hci_rx_work Call Trace: dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106 check_noncircular+0x2fc/0x400 kernel/locking/lockdep.c:2187 check_prev_add kernel/locking/lockdep.c:3134 [inline] check_prevs_add kernel/locking/lockdep.c:3253 [inline] validate_chain kernel/locking/lockdep.c:3869 [inline] __lock_acquire+0x37ef/0x7d80 kernel/locking/lockdep.c:5137 lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5756 __mutex_lock_common kernel/locking/mutex.c:603 [inline] __mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747 hci_le_conn_update+0xd0/0x320 net/bluetooth/hci_conn.c:502 l2cap_conn_param_update_req net/bluetooth/l2cap_core.c:4740 [inline] l2cap_le_sig_cmd net/bluetooth/l2cap_core.c:5558 [inline] l2cap_le_sig_channel net/bluetooth/l2cap_core.c:5635 [inline] l2cap_recv_frame+0xce07/0x10090 net/bluetooth/l2cap_core.c:7040 l2cap_recv_acldata+0x50b/0x11a0 net/bluetooth/l2cap_core.c:7756 hci_acldata_packet net/bluetooth/hci_core.c:3784 [inline] hci_rx_work+0x545/0xd60 net/bluetooth/hci_core.c:4022 process_one_work kernel/workqueue.c:2657 [inline] process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815 kthread+0x2fa/0x390 kernel/kthread.c:388 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293 Bluetooth: hci2: command 0x0406 tx timeout Bluetooth: hci2: command 0x0406 tx timeout