====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ kworker/u9:8/5843 is trying to acquire lock: ffff88804be98040 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}, at: touch_work_lockdep_map kernel/workqueue.c:4005 [inline] ffff88804be98040 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}, at: start_flush_work kernel/workqueue.c:4259 [inline] ffff88804be98040 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}, at: __flush_work+0x4ca/0xcb0 kernel/workqueue.c:4291 but task is already holding lock: ffff88804be982f8 (&conn->lock#2){+.+.}-{4:4}, at: l2cap_conn_del+0x80/0x770 net/bluetooth/l2cap_core.c:1755 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&conn->lock#2){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:614 [inline] __mutex_lock+0x1a2/0x1b90 kernel/locking/mutex.c:776 l2cap_info_timeout+0x79/0xa0 net/bluetooth/l2cap_core.c:1661 process_one_work+0x9d7/0x1920 kernel/workqueue.c:3275 process_scheduled_works kernel/workqueue.c:3358 [inline] worker_thread+0x5da/0xe40 kernel/workqueue.c:3439 kthread+0x370/0x450 kernel/kthread.c:467 ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #0 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}: check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x14b8/0x2630 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x1cf/0x380 kernel/locking/lockdep.c:5825 touch_work_lockdep_map kernel/workqueue.c:4005 [inline] start_flush_work kernel/workqueue.c:4259 [inline] __flush_work+0x4de/0xcb0 kernel/workqueue.c:4291 __cancel_work_sync kernel/workqueue.c:4447 [inline] cancel_delayed_work_sync+0xd1/0xf0 kernel/workqueue.c:4521 l2cap_conn_del+0x5d1/0x770 net/bluetooth/l2cap_core.c:1791 l2cap_connect_cfm+0x9bb/0x1050 net/bluetooth/l2cap_core.c:7323 hci_connect_cfm include/net/bluetooth/hci_core.h:2139 [inline] hci_conn_failed+0x188/0x360 net/bluetooth/hci_conn.c:1342 hci_abort_conn_sync+0x7d9/0xb20 net/bluetooth/hci_sync.c:5753 abort_conn_sync+0x142/0x350 net/bluetooth/hci_conn.c:3074 hci_cmd_sync_work+0x1c0/0x470 net/bluetooth/hci_sync.c:332 process_one_work+0x9d7/0x1920 kernel/workqueue.c:3275 process_scheduled_works kernel/workqueue.c:3358 [inline] worker_thread+0x5da/0xe40 kernel/workqueue.c:3439 kthread+0x370/0x450 kernel/kthread.c:467 ret_from_fork+0x754/0xd80 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: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&conn->lock#2); lock((work_completion)(&(&conn->info_timer)->work)); lock(&conn->lock#2); lock((work_completion)(&(&conn->info_timer)->work)); *** DEADLOCK *** 7 locks held by kworker/u9:8/5843: #0: ffff888056dc9148 ((wq_completion)hci4){+.+.}-{0:0}, at: process_one_work+0x1287/0x1920 kernel/workqueue.c:3250 #1: ffffc90003a77d08 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: process_one_work+0x93c/0x1920 kernel/workqueue.c:3251 #2: ffff888054268ec0 (&hdev->req_lock){+.+.}-{4:4}, at: hci_cmd_sync_work+0x18a/0x470 net/bluetooth/hci_sync.c:331 #3: ffff8880542680c0 (&hdev->lock){+.+.}-{4:4}, at: hci_abort_conn_sync+0x141/0xb20 net/bluetooth/hci_sync.c:5734 #4: ffffffff908abb28 (hci_cb_list_lock){+.+.}-{4:4}, at: hci_connect_cfm include/net/bluetooth/hci_core.h:2136 [inline] #4: ffffffff908abb28 (hci_cb_list_lock){+.+.}-{4:4}, at: hci_conn_failed+0x119/0x360 net/bluetooth/hci_conn.c:1342 #5: ffff88804be982f8 (&conn->lock#2){+.+.}-{4:4}, at: l2cap_conn_del+0x80/0x770 net/bluetooth/l2cap_core.c:1755 #6: ffffffff8e7e93e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:312 [inline] #6: ffffffff8e7e93e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:850 [inline] #6: ffffffff8e7e93e0 (rcu_read_lock){....}-{1:3}, at: start_flush_work kernel/workqueue.c:4233 [inline] #6: ffffffff8e7e93e0 (rcu_read_lock){....}-{1:3}, at: __flush_work+0xfd/0xcb0 kernel/workqueue.c:4291 stack backtrace: CPU: 1 UID: 0 PID: 5843 Comm: kworker/u9:8 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026 Workqueue: hci4 hci_cmd_sync_work Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120 print_circular_bug.cold+0x178/0x1c7 kernel/locking/lockdep.c:2043 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2175 check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x14b8/0x2630 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x1cf/0x380 kernel/locking/lockdep.c:5825 touch_work_lockdep_map kernel/workqueue.c:4005 [inline] start_flush_work kernel/workqueue.c:4259 [inline] __flush_work+0x4de/0xcb0 kernel/workqueue.c:4291 __cancel_work_sync kernel/workqueue.c:4447 [inline] cancel_delayed_work_sync+0xd1/0xf0 kernel/workqueue.c:4521 l2cap_conn_del+0x5d1/0x770 net/bluetooth/l2cap_core.c:1791 l2cap_connect_cfm+0x9bb/0x1050 net/bluetooth/l2cap_core.c:7323 hci_connect_cfm include/net/bluetooth/hci_core.h:2139 [inline] hci_conn_failed+0x188/0x360 net/bluetooth/hci_conn.c:1342 hci_abort_conn_sync+0x7d9/0xb20 net/bluetooth/hci_sync.c:5753 abort_conn_sync+0x142/0x350 net/bluetooth/hci_conn.c:3074 hci_cmd_sync_work+0x1c0/0x470 net/bluetooth/hci_sync.c:332 process_one_work+0x9d7/0x1920 kernel/workqueue.c:3275 process_scheduled_works kernel/workqueue.c:3358 [inline] worker_thread+0x5da/0xe40 kernel/workqueue.c:3439 kthread+0x370/0x450 kernel/kthread.c:467 ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245