====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ kworker/u5:0/52 is trying to acquire lock: ffffffff8f57ac48 (rfcomm_mutex){+.+.}-{3:3}, at: rfcomm_security_cfm+0x41/0x550 net/bluetooth/rfcomm/core.c:2276 but task is already holding lock: ffffffff8f557408 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_encrypt_cfm+0x2fe/0x4d0 include/net/bluetooth/hci_core.h:2080 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+0x135/0xce0 kernel/locking/mutex.c:747 hci_connect_cfm include/net/bluetooth/hci_core.h:2004 [inline] hci_remote_features_evt+0x535/0x900 net/bluetooth/hci_event.c:3735 hci_event_func net/bluetooth/hci_event.c:7481 [inline] hci_event_packet+0x66e/0xe60 net/bluetooth/hci_event.c:7530 hci_rx_work+0x43a/0xd60 net/bluetooth/hci_core.c:4060 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+0x135/0xce0 kernel/locking/mutex.c:747 hci_release_dev+0x123/0x14f0 net/bluetooth/hci_core.c:2760 bt_host_release+0x93/0xa0 net/bluetooth/hci_sysfs.c:100 device_release+0xbc/0x1e0 drivers/base/core.c:-1 kobject_cleanup lib/kobject.c:689 [inline] kobject_release lib/kobject.c:720 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0x21b/0x450 lib/kobject.c:737 device_release+0xbc/0x1e0 drivers/base/core.c:-1 kobject_cleanup lib/kobject.c:689 [inline] kobject_release lib/kobject.c:720 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0x21b/0x450 lib/kobject.c:737 hci_conn_put include/net/bluetooth/hci_core.h:1574 [inline] l2cap_conn_free net/bluetooth/l2cap_core.c:1847 [inline] kref_put include/linux/kref.h:65 [inline] l2cap_conn_put net/bluetooth/l2cap_core.c:1860 [inline] l2cap_chan_destroy net/bluetooth/l2cap_core.c:497 [inline] kref_put include/linux/kref.h:65 [inline] l2cap_chan_put+0x1f8/0x2e0 net/bluetooth/l2cap_core.c:524 l2cap_sock_release+0x17d/0x1e0 net/bluetooth/l2cap_sock.c:1493 __sock_release net/socket.c:659 [inline] sock_release+0x7f/0x140 net/socket.c:687 rfcomm_session_del+0x141/0x200 net/bluetooth/rfcomm/core.c:785 rfcomm_process_sessions net/bluetooth/rfcomm/core.c:-1 [inline] rfcomm_run+0x4692/0x5f60 net/bluetooth/rfcomm/core.c:2258 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 (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+0x135/0xce0 kernel/locking/mutex.c:747 rfcomm_security_cfm+0x41/0x550 net/bluetooth/rfcomm/core.c:2276 hci_encrypt_cfm+0x363/0x4d0 include/net/bluetooth/hci_core.h:2083 hci_encrypt_change_evt+0x5c3/0xe30 net/bluetooth/hci_event.c:3606 hci_event_func net/bluetooth/hci_event.c:7481 [inline] hci_event_packet+0x66e/0xe60 net/bluetooth/hci_event.c:7530 hci_rx_work+0x43a/0xd60 net/bluetooth/hci_core.c:4060 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/u5:0/52: #0: ffff88802768d138 ((wq_completion)hci1#2){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline] #0: ffff88802768d138 ((wq_completion)hci1#2){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734 #1: ffffc90000bcfd00 ((work_completion)(&hdev->rx_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline] #1: ffffc90000bcfd00 ((work_completion)(&hdev->rx_work)){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734 #2: ffff8880548940b8 (&hdev->lock){+.+.}-{3:3}, at: hci_encrypt_change_evt+0x93/0xe30 net/bluetooth/hci_event.c:3559 #3: ffffffff8f557408 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_encrypt_cfm+0x2fe/0x4d0 include/net/bluetooth/hci_core.h:2080 stack backtrace: CPU: 0 PID: 52 Comm: kworker/u5:0 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/06/2026 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+0x135/0xce0 kernel/locking/mutex.c:747 rfcomm_security_cfm+0x41/0x550 net/bluetooth/rfcomm/core.c:2276 hci_encrypt_cfm+0x363/0x4d0 include/net/bluetooth/hci_core.h:2083 hci_encrypt_change_evt+0x5c3/0xe30 net/bluetooth/hci_event.c:3606 hci_event_func net/bluetooth/hci_event.c:7481 [inline] hci_event_packet+0x66e/0xe60 net/bluetooth/hci_event.c:7530 hci_rx_work+0x43a/0xd60 net/bluetooth/hci_core.c:4060 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