====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ kworker/0:7/5337 is trying to acquire lock: ffff888011600338 (&conn->lock#2){+.+.}-{4:4}, at: l2cap_info_timeout+0x60/0xa0 net/bluetooth/l2cap_core.c:1669 but task is already holding lock: ffffc9000dedfbc0 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3233 [inline] ffffc9000dedfbc0 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x1770 kernel/workqueue.c:3340 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}: touch_work_lockdep_map kernel/workqueue.c:3955 [inline] start_flush_work kernel/workqueue.c:4209 [inline] __flush_work+0x6b8/0xbc0 kernel/workqueue.c:4241 __cancel_work_sync+0xbe/0x110 kernel/workqueue.c:4397 l2cap_conn_del+0x402/0x5b0 net/bluetooth/l2cap_core.c:1797 l2cap_connect_cfm+0x122/0x10e0 net/bluetooth/l2cap_core.c:7260 hci_connect_cfm include/net/bluetooth/hci_core.h:2131 [inline] hci_conn_failed+0x1ce/0x340 net/bluetooth/hci_conn.c:1336 hci_abort_conn_sync+0x658/0xe30 net/bluetooth/hci_sync.c:5721 hci_disconnect_all_sync+0x1b5/0x350 net/bluetooth/hci_sync.c:5744 hci_suspend_sync+0x3fc/0xc90 net/bluetooth/hci_sync.c:6220 hci_suspend_dev+0x28d/0x530 net/bluetooth/hci_core.c:2849 hci_suspend_notifier+0xf2/0x2f0 net/bluetooth/hci_core.c:2420 notifier_call_chain+0x19d/0x3a0 kernel/notifier.c:85 notifier_call_chain_robust kernel/notifier.c:120 [inline] blocking_notifier_call_chain_robust+0x85/0x100 kernel/notifier.c:345 pm_notifier_call_chain_robust+0x2c/0x60 kernel/power/main.c:172 snapshot_open+0x19c/0x280 kernel/power/user.c:77 misc_open+0x2d5/0x350 drivers/char/misc.c:163 chrdev_open+0x4cc/0x5e0 fs/char_dev.c:414 do_dentry_open+0x7ce/0x1420 fs/open.c:962 vfs_open+0x3b/0x340 fs/open.c:1094 do_open fs/namei.c:4628 [inline] path_openat+0x340e/0x3dd0 fs/namei.c:4787 do_filp_open+0x1fa/0x410 fs/namei.c:4814 do_sys_openat2+0x121/0x200 fs/open.c:1430 do_sys_open fs/open.c:1436 [inline] __do_sys_openat fs/open.c:1452 [inline] __se_sys_openat fs/open.c:1447 [inline] __x64_sys_openat+0x138/0x170 fs/open.c:1447 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (&conn->lock#2){+.+.}-{4:4}: 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+0x15a6/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0x107/0x340 kernel/locking/lockdep.c:5868 __mutex_lock_common kernel/locking/mutex.c:614 [inline] __mutex_lock+0x187/0x1350 kernel/locking/mutex.c:776 l2cap_info_timeout+0x60/0xa0 net/bluetooth/l2cap_core.c:1669 process_one_work kernel/workqueue.c:3257 [inline] process_scheduled_works+0xad1/0x1770 kernel/workqueue.c:3340 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3421 kthread+0x711/0x8a0 kernel/kthread.c:463 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock((work_completion)(&(&conn->info_timer)->work)); lock(&conn->lock#2); lock((work_completion)(&(&conn->info_timer)->work)); lock(&conn->lock#2); *** DEADLOCK *** 2 locks held by kworker/0:7/5337: #0: ffff88801a467548 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3232 [inline] #0: ffff88801a467548 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x1770 kernel/workqueue.c:3340 #1: ffffc9000dedfbc0 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3233 [inline] #1: ffffc9000dedfbc0 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x1770 kernel/workqueue.c:3340 stack backtrace: CPU: 0 UID: 0 PID: 5337 Comm: kworker/0:7 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 Workqueue: events l2cap_info_timeout Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2043 check_noncircular+0x12e/0x150 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+0x15a6/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0x107/0x340 kernel/locking/lockdep.c:5868 __mutex_lock_common kernel/locking/mutex.c:614 [inline] __mutex_lock+0x187/0x1350 kernel/locking/mutex.c:776 l2cap_info_timeout+0x60/0xa0 net/bluetooth/l2cap_core.c:1669 process_one_work kernel/workqueue.c:3257 [inline] process_scheduled_works+0xad1/0x1770 kernel/workqueue.c:3340 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3421 kthread+0x711/0x8a0 kernel/kthread.c:463 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246