====================================================== WARNING: possible circular locking dependency detected 6.16.0-rc3-syzkaller-00902-gbeead7eea896 #0 Not tainted ------------------------------------------------------ syz.0.4363/21902 is trying to acquire lock: ffff888057d70840 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] ffff888057d70840 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline] ffff888057d70840 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}, at: start_flush_work kernel/workqueue.c:4152 [inline] ffff888057d70840 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}, at: __flush_work+0xd2/0xbc0 kernel/workqueue.c:4210 but task is already holding lock: ffff888057d70b38 (&conn->lock#2){+.+.}-{4:4}, at: l2cap_conn_del+0x70/0x680 net/bluetooth/l2cap_core.c:1762 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&conn->lock#2){+.+.}-{4:4}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871 __mutex_lock_common kernel/locking/mutex.c:602 [inline] __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:747 l2cap_info_timeout+0x60/0xa0 net/bluetooth/l2cap_core.c:1668 process_one_work kernel/workqueue.c:3238 [inline] process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402 kthread+0x70e/0x8a0 kernel/kthread.c:464 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148 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:3168 [inline] check_prevs_add kernel/locking/lockdep.c:3287 [inline] validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3911 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871 touch_work_lockdep_map kernel/workqueue.c:3924 [inline] start_flush_work kernel/workqueue.c:4178 [inline] __flush_work+0x6b8/0xbc0 kernel/workqueue.c:4210 __cancel_work_sync+0xbe/0x110 kernel/workqueue.c:4366 l2cap_conn_del+0x4f0/0x680 net/bluetooth/l2cap_core.c:1796 hci_disconn_cfm include/net/bluetooth/hci_core.h:2071 [inline] hci_conn_hash_flush+0x10a/0x230 net/bluetooth/hci_conn.c:2560 hci_dev_close_sync+0xaef/0x1330 net/bluetooth/hci_sync.c:5250 hci_dev_do_close net/bluetooth/hci_core.c:501 [inline] hci_dev_close+0x108/0x200 net/bluetooth/hci_core.c:526 sock_do_ioctl+0xd9/0x300 net/socket.c:1238 sock_ioctl+0x576/0x790 net/socket.c:1359 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:907 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:893 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f 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 *** 5 locks held by syz.0.4363/21902: #0: ffff888033cc4dc0 (&hdev->req_lock){+.+.}-{4:4}, at: hci_dev_do_close net/bluetooth/hci_core.c:499 [inline] #0: ffff888033cc4dc0 (&hdev->req_lock){+.+.}-{4:4}, at: hci_dev_close+0x100/0x200 net/bluetooth/hci_core.c:526 #1: ffff888033cc40b8 (&hdev->lock){+.+.}-{4:4}, at: hci_dev_close_sync+0x66a/0x1330 net/bluetooth/hci_sync.c:5238 #2: ffffffff8f6795a8 (hci_cb_list_lock){+.+.}-{4:4}, at: hci_disconn_cfm include/net/bluetooth/hci_core.h:2068 [inline] #2: ffffffff8f6795a8 (hci_cb_list_lock){+.+.}-{4:4}, at: hci_conn_hash_flush+0xa1/0x230 net/bluetooth/hci_conn.c:2560 #3: ffff888057d70b38 (&conn->lock#2){+.+.}-{4:4}, at: l2cap_conn_del+0x70/0x680 net/bluetooth/l2cap_core.c:1762 #4: ffffffff8e13ee60 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #4: ffffffff8e13ee60 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline] #4: ffffffff8e13ee60 (rcu_read_lock){....}-{1:3}, at: start_flush_work kernel/workqueue.c:4152 [inline] #4: ffffffff8e13ee60 (rcu_read_lock){....}-{1:3}, at: __flush_work+0xd2/0xbc0 kernel/workqueue.c:4210 stack backtrace: CPU: 1 UID: 0 PID: 21902 Comm: syz.0.4363 Not tainted 6.16.0-rc3-syzkaller-00902-gbeead7eea896 #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 Call Trace: dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2046 check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2178 check_prev_add kernel/locking/lockdep.c:3168 [inline] check_prevs_add kernel/locking/lockdep.c:3287 [inline] validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3911 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871 touch_work_lockdep_map kernel/workqueue.c:3924 [inline] start_flush_work kernel/workqueue.c:4178 [inline] __flush_work+0x6b8/0xbc0 kernel/workqueue.c:4210 __cancel_work_sync+0xbe/0x110 kernel/workqueue.c:4366 l2cap_conn_del+0x4f0/0x680 net/bluetooth/l2cap_core.c:1796 hci_disconn_cfm include/net/bluetooth/hci_core.h:2071 [inline] hci_conn_hash_flush+0x10a/0x230 net/bluetooth/hci_conn.c:2560 hci_dev_close_sync+0xaef/0x1330 net/bluetooth/hci_sync.c:5250 hci_dev_do_close net/bluetooth/hci_core.c:501 [inline] hci_dev_close+0x108/0x200 net/bluetooth/hci_core.c:526 sock_do_ioctl+0xd9/0x300 net/socket.c:1238 sock_ioctl+0x576/0x790 net/socket.c:1359 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:907 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:893 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fde4fb8e929 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fde50955038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fde4fdb5fa0 RCX: 00007fde4fb8e929 RDX: 0000000000000000 RSI: 00000000400448ca RDI: 000000000000000a RBP: 00007fde4fc10b39 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007fde4fdb5fa0 R15: 00007fff7e70fe08