====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Tainted: G L ------------------------------------------------------ krfcommd/3206 is trying to acquire lock: ffff888037d3d948 ((wq_completion)hci2#2){+.+.}-{0:0}, at: touch_wq_lockdep_map+0xb5/0x180 kernel/workqueue.c:4272 but task is already holding lock: ffffffff91825f00 (rfcomm_mutex){+.+.}-{4:4}, at: rfcomm_process_sessions+0x2c6/0x9690 net/bluetooth/rfcomm/core.c:2150 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #4 (rfcomm_mutex){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x197/0x15a0 kernel/locking/mutex.c:821 rfcomm_security_cfm+0x90/0x820 net/bluetooth/rfcomm/core.c:2277 hci_auth_cfm include/net/bluetooth/hci_core.h:2250 [inline] hci_auth_complete_evt+0x39f/0xc80 net/bluetooth/hci_event.c:3635 hci_event_func net/bluetooth/hci_event.c:8021 [inline] hci_event_packet+0x6cd/0xf10 net/bluetooth/hci_event.c:8072 hci_rx_work+0x2b4/0x1110 net/bluetooth/hci_core.c:4124 process_one_work kernel/workqueue.c:3495 [inline] process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3578 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3659 kthread+0x38b/0x480 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #3 (hci_cb_list_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x197/0x15a0 kernel/locking/mutex.c:821 hci_connect_cfm include/net/bluetooth/hci_core.h:2211 [inline] hci_remote_features_evt+0x53d/0x950 net/bluetooth/hci_event.c:3892 hci_event_func net/bluetooth/hci_event.c:8021 [inline] hci_event_packet+0x6cd/0xf10 net/bluetooth/hci_event.c:8072 hci_rx_work+0x2b4/0x1110 net/bluetooth/hci_core.c:4124 process_one_work kernel/workqueue.c:3495 [inline] process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3578 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3659 kthread+0x38b/0x480 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #2 (&hdev->lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x197/0x15a0 kernel/locking/mutex.c:821 hci_send_cmd_sync net/bluetooth/hci_core.c:4163 [inline] hci_cmd_work+0xa0/0x850 net/bluetooth/hci_core.c:4212 process_one_work kernel/workqueue.c:3495 [inline] process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3578 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3659 kthread+0x38b/0x480 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #1 ((work_completion)(&hdev->cmd_work)){+.+.}-{0:0}: process_one_work kernel/workqueue.c:3471 [inline] process_scheduled_works+0xc03/0x1630 kernel/workqueue.c:3578 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3659 kthread+0x38b/0x480 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #0 ((wq_completion)hci2#2){+.+.}-{0:0}: check_prev_add kernel/locking/lockdep.c:3209 [inline] check_prevs_add kernel/locking/lockdep.c:3328 [inline] validate_chain kernel/locking/lockdep.c:3952 [inline] __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942 touch_wq_lockdep_map+0xcb/0x180 kernel/workqueue.c:4272 __flush_workqueue+0x148/0x10b0 kernel/workqueue.c:4314 drain_workqueue+0xce/0x380 kernel/workqueue.c:4478 destroy_workqueue+0xbe/0x7b0 kernel/workqueue.c:6372 hci_release_dev+0xe3/0x1510 net/bluetooth/hci_core.c:2728 bt_host_release+0x93/0xa0 net/bluetooth/hci_sysfs.c:100 device_release+0xc4/0x1f0 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+0x222/0x550 lib/kobject.c:737 device_release+0xc4/0x1f0 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+0x222/0x550 lib/kobject.c:737 hci_conn_put include/net/bluetooth/hci_core.h:1737 [inline] l2cap_conn_free net/bluetooth/l2cap_core.c:1933 [inline] kref_put include/linux/kref.h:65 [inline] l2cap_conn_put net/bluetooth/l2cap_core.c:1946 [inline] l2cap_chan_destroy net/bluetooth/l2cap_core.c:495 [inline] kref_put include/linux/kref.h:65 [inline] l2cap_chan_put+0x1fd/0x350 net/bluetooth/l2cap_core.c:522 l2cap_sock_release+0x1a2/0x230 net/bluetooth/l2cap_sock.c:1536 __sock_release net/socket.c:735 [inline] sock_release+0x85/0x150 net/socket.c:763 rfcomm_session_del+0x14b/0x270 net/bluetooth/rfcomm/core.c:782 rfcomm_process_sessions+0x7456/0x9690 net/bluetooth/rfcomm/core.c:-1 rfcomm_run+0x3f5/0x620 net/bluetooth/rfcomm/core.c:2259 kthread+0x38b/0x480 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 other info that might help us debug this: Chain exists of: (wq_completion)hci2#2 --> hci_cb_list_lock --> rfcomm_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(rfcomm_mutex); lock(hci_cb_list_lock); lock(rfcomm_mutex); lock((wq_completion)hci2#2); *** DEADLOCK *** locks held by krfcommd/3206: 1, last CPU#1: #0: ffffffff91825f00 (rfcomm_mutex){+.+.}-{4:4}, at: rfcomm_process_sessions+0x2c6/0x9690 net/bluetooth/rfcomm/core.c:2150 stack backtrace: CPU: 1 UID: 0 PID: 3206 Comm: krfcommd Tainted: G L syzkaller #0 PREEMPT(full) Tainted: [L]=SOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2087 check_noncircular+0x12f/0x150 kernel/locking/lockdep.c:2219 check_prev_add kernel/locking/lockdep.c:3209 [inline] check_prevs_add kernel/locking/lockdep.c:3328 [inline] validate_chain kernel/locking/lockdep.c:3952 [inline] __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942 touch_wq_lockdep_map+0xcb/0x180 kernel/workqueue.c:4272 __flush_workqueue+0x148/0x10b0 kernel/workqueue.c:4314 drain_workqueue+0xce/0x380 kernel/workqueue.c:4478 destroy_workqueue+0xbe/0x7b0 kernel/workqueue.c:6372 hci_release_dev+0xe3/0x1510 net/bluetooth/hci_core.c:2728 bt_host_release+0x93/0xa0 net/bluetooth/hci_sysfs.c:100 device_release+0xc4/0x1f0 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+0x222/0x550 lib/kobject.c:737 device_release+0xc4/0x1f0 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+0x222/0x550 lib/kobject.c:737 hci_conn_put include/net/bluetooth/hci_core.h:1737 [inline] l2cap_conn_free net/bluetooth/l2cap_core.c:1933 [inline] kref_put include/linux/kref.h:65 [inline] l2cap_conn_put net/bluetooth/l2cap_core.c:1946 [inline] l2cap_chan_destroy net/bluetooth/l2cap_core.c:495 [inline] kref_put include/linux/kref.h:65 [inline] l2cap_chan_put+0x1fd/0x350 net/bluetooth/l2cap_core.c:522 l2cap_sock_release+0x1a2/0x230 net/bluetooth/l2cap_sock.c:1536 __sock_release net/socket.c:735 [inline] sock_release+0x85/0x150 net/socket.c:763 rfcomm_session_del+0x14b/0x270 net/bluetooth/rfcomm/core.c:782 rfcomm_process_sessions+0x7456/0x9690 net/bluetooth/rfcomm/core.c:-1 rfcomm_run+0x3f5/0x620 net/bluetooth/rfcomm/core.c:2259 kthread+0x38b/0x480 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245