====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Tainted: G S ------------------------------------------------------ kworker/u5:1/5089 is trying to acquire lock: ffffffff8f364ac8 (rfcomm_mutex){+.+.}-{3:3}, at: rfcomm_security_cfm+0x41/0x550 net/bluetooth/rfcomm/core.c:2220 but task is already holding lock: ffffffff8f341368 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_encrypt_cfm+0x2fe/0x4d0 include/net/bluetooth/hci_core.h:2077 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 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 -> #1 (&hdev->lock){+.+.}-{3:3}: __mutex_lock_common kernel/locking/mutex.c:603 [inline] __mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747 l2cap_chan_connect+0xfc/0xe30 net/bluetooth/l2cap_core.c:7195 l2cap_sock_connect+0x586/0x760 net/bluetooth/l2cap_sock.c:257 kernel_connect+0x142/0x1c0 net/socket.c:3636 rfcomm_session_create net/bluetooth/rfcomm/core.c:811 [inline] __rfcomm_dlc_open net/bluetooth/rfcomm/core.c:388 [inline] rfcomm_dlc_open+0xa1f/0xec0 net/bluetooth/rfcomm/core.c:431 rfcomm_sock_connect+0x2ed/0x600 net/bluetooth/rfcomm/sock.c:419 __sys_connect_file net/socket.c:2057 [inline] __sys_connect+0x3da/0x470 net/socket.c:2074 __do_sys_connect net/socket.c:2084 [inline] __se_sys_connect net/socket.c:2081 [inline] __x64_sys_connect+0x7a/0x90 net/socket.c:2081 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x68/0xd2 -> #0 (rfcomm_mutex){+.+.}-{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+0x3a07/0x7eb0 kernel/locking/lockdep.c:5171 lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5790 __mutex_lock_common kernel/locking/mutex.c:603 [inline] __mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747 rfcomm_security_cfm+0x41/0x550 net/bluetooth/rfcomm/core.c:2220 hci_encrypt_cfm+0x363/0x4d0 include/net/bluetooth/hci_core.h:2080 hci_encrypt_change_evt+0x5c3/0xe30 net/bluetooth/hci_event.c:3590 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 other info that might help us debug this: Chain exists of: rfcomm_mutex --> &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(rfcomm_mutex); *** DEADLOCK *** 4 locks held by kworker/u5:1/5089: #0: ffff88805d721538 ((wq_completion)hci1#2){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline] #0: ffff88805d721538 ((wq_completion)hci1#2){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734 #1: ffffc9000fe57d00 ((work_completion)(&hdev->rx_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline] #1: ffffc9000fe57d00 ((work_completion)(&hdev->rx_work)){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734 #2: ffff888065a740b8 (&hdev->lock){+.+.}-{3:3}, at: hci_encrypt_change_evt+0x93/0xe30 net/bluetooth/hci_event.c:3543 #3: ffffffff8f341368 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_encrypt_cfm+0x2fe/0x4d0 include/net/bluetooth/hci_core.h:2077 stack backtrace: CPU: 0 PID: 5089 Comm: kworker/u5:1 Tainted: G S syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 Workqueue: hci1 hci_rx_work Call Trace: dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106 check_noncircular+0x2fc/0x400 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+0x3a07/0x7eb0 kernel/locking/lockdep.c:5171 lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5790 __mutex_lock_common kernel/locking/mutex.c:603 [inline] __mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747 rfcomm_security_cfm+0x41/0x550 net/bluetooth/rfcomm/core.c:2220 hci_encrypt_cfm+0x363/0x4d0 include/net/bluetooth/hci_core.h:2080 hci_encrypt_change_evt+0x5c3/0xe30 net/bluetooth/hci_event.c:3590 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 hcon ffff88804587c000 hci1: handle 0xc9 reason 0x05 hcon ffff88804587c000 orig refcnt 0 kcov: kcov_move_area: ffffc900146ba000 1048576 <= ffffc9000ca91000 878300 Bluetooth: hci1: command 0x0406 tx timeout hci1: err 0x6e hci1 cmd_cnt 1 cmd queued 1 hci1: skb ffff88807eede8c0 hci1 type 1 len 6 Bluetooth: hci1: command 0x0406 tx timeout hci1: err 0x6e hci1 cmd_cnt 1 cmd queued 0 hci1 cmd_cnt 1 cmd queued 1 hci1: skb ffff888045786a00 hci1 type 1 len 6 Bluetooth: hci1: command 0x0406 tx timeout hci1: err 0x6e hci1 cmd_cnt 1 cmd queued 0