======================================================
WARNING: possible circular locking dependency detected
6.16.0-rc5-syzkaller-00266-g3f31a806a62e #0 Not tainted
------------------------------------------------------
kworker/2:4/6147 is trying to acquire lock:
ffff88801c784338 (&conn->lock#2){+.+.}-{4:4}, at: l2cap_info_timeout+0x79/0xa0 net/bluetooth/l2cap_core.c:1668

but task is already holding lock:
ffffc900042efd10 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3214

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:3924 [inline]
       start_flush_work kernel/workqueue.c:4178 [inline]
       __flush_work+0x4e4/0xcc0 kernel/workqueue.c:4210
       __cancel_work_sync+0x10c/0x130 kernel/workqueue.c:4366
       l2cap_conn_del+0x5af/0x730 net/bluetooth/l2cap_core.c:1796
       l2cap_disconn_cfm net/bluetooth/l2cap_core.c:7309 [inline]
       l2cap_disconn_cfm+0x96/0xd0 net/bluetooth/l2cap_core.c:7302
       hci_disconn_cfm include/net/bluetooth/hci_core.h:2070 [inline]
       hci_conn_hash_flush+0x10b/0x260 net/bluetooth/hci_conn.c:2560
       hci_dev_close_sync+0x602/0x11d0 net/bluetooth/hci_sync.c:5294
       hci_dev_do_close+0x2e/0x90 net/bluetooth/hci_core.c:501
       hci_rfkill_set_block+0x225/0x360 net/bluetooth/hci_core.c:929
       rfkill_set_block+0x1fe/0x550 net/rfkill/core.c:346
       rfkill_fop_write+0x2c0/0x580 net/rfkill/core.c:1301
       vfs_write+0x2a0/0x1150 fs/read_write.c:684
       ksys_write+0x1f8/0x250 fs/read_write.c:738
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0x4c0 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:3168 [inline]
       check_prevs_add kernel/locking/lockdep.c:3287 [inline]
       validate_chain kernel/locking/lockdep.c:3911 [inline]
       __lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5240
       lock_acquire kernel/locking/lockdep.c:5871 [inline]
       lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828
       __mutex_lock_common kernel/locking/mutex.c:602 [inline]
       __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:747
       l2cap_info_timeout+0x79/0xa0 net/bluetooth/l2cap_core.c:1668
       process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3238
       process_scheduled_works kernel/workqueue.c:3321 [inline]
       worker_thread+0x6c8/0xf10 kernel/workqueue.c:3402
       kthread+0x3c5/0x780 kernel/kthread.c:464
       ret_from_fork+0x5d7/0x6f0 arch/x86/kernel/process.c:148
       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((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/2:4/6147:
 #0: ffff88801b884d48 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3213
 #1: ffffc900042efd10 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3214

stack backtrace:
CPU: 2 UID: 0 PID: 6147 Comm: kworker/2:4 Not tainted 6.16.0-rc5-syzkaller-00266-g3f31a806a62e #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:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_circular_bug+0x275/0x350 kernel/locking/lockdep.c:2046
 check_noncircular+0x14c/0x170 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 kernel/locking/lockdep.c:3911 [inline]
 __lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5240
 lock_acquire kernel/locking/lockdep.c:5871 [inline]
 lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828
 __mutex_lock_common kernel/locking/mutex.c:602 [inline]
 __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:747
 l2cap_info_timeout+0x79/0xa0 net/bluetooth/l2cap_core.c:1668
 process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3238
 process_scheduled_works kernel/workqueue.c:3321 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3402
 kthread+0x3c5/0x780 kernel/kthread.c:464
 ret_from_fork+0x5d7/0x6f0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>