BUG: workqueue leaked atomic, lock or RCU: kworker/u33:0[66]
     preempt=0x00000000 lock=0->1 RCU=0->0 workfn=hci_rx_work
1 lock held by kworker/u33:0/66:
 #0: ffff88800057d518 (&chan->lock#2/1){+.+.}-{3:3}, at: l2cap_chan_lock include/net/bluetooth/l2cap.h:827 [inline]
 #0: ffff88800057d518 (&chan->lock#2/1){+.+.}-{3:3}, at: l2cap_conless_channel net/bluetooth/l2cap_core.c:6764 [inline]
 #0: ffff88800057d518 (&chan->lock#2/1){+.+.}-{3:3}, at: l2cap_recv_frame+0x14f6/0x8e20 net/bluetooth/l2cap_core.c:6830
CPU: 1 PID: 66 Comm: kworker/u33:0 Not tainted 6.10.0-syzkaller-04472-g51835949dda3 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: hci4 hci_rx_work
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x16c/0x1f0 lib/dump_stack.c:114
 process_one_work+0x1170/0x1ad0 kernel/workqueue.c:3252
 process_scheduled_works kernel/workqueue.c:3312 [inline]
 worker_thread+0x6c8/0xf20 kernel/workqueue.c:3390
 kthread+0x2c1/0x3a0 kernel/kthread.c:389
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>

======================================================
WARNING: possible circular locking dependency detected
6.10.0-syzkaller-04472-g51835949dda3 #0 Not tainted
------------------------------------------------------
kworker/u33:0/66 is trying to acquire lock:
ffff88802753b148 ((wq_completion)hci4#2){+.+.}-{0:0}, at: process_one_work+0x11f0/0x1ad0 kernel/workqueue.c:3206

but task is already holding lock:
ffff88800057d518 (&chan->lock#2/1){+.+.}-{3:3}, at: l2cap_chan_lock include/net/bluetooth/l2cap.h:827 [inline]
ffff88800057d518 (&chan->lock#2/1){+.+.}-{3:3}, at: l2cap_conless_channel net/bluetooth/l2cap_core.c:6764 [inline]
ffff88800057d518 (&chan->lock#2/1){+.+.}-{3:3}, at: l2cap_recv_frame+0x14f6/0x8e20 net/bluetooth/l2cap_core.c:6830

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&chan->lock#2/1){+.+.}-{3:3}:
       __lock_release kernel/locking/lockdep.c:5467 [inline]
       lock_release+0x33e/0x6c0 kernel/locking/lockdep.c:5773
       process_one_work+0xa27/0x1ad0 kernel/workqueue.c:3238
       process_scheduled_works kernel/workqueue.c:3312 [inline]
       worker_thread+0x6c8/0xf20 kernel/workqueue.c:3390
       kthread+0x2c1/0x3a0 kernel/kthread.c:389
       ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

-> #0 ((wq_completion)hci4#2){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3133 [inline]
       check_prevs_add kernel/locking/lockdep.c:3252 [inline]
       validate_chain kernel/locking/lockdep.c:3868 [inline]
       __lock_acquire+0x2478/0x3b30 kernel/locking/lockdep.c:5136
       lock_acquire kernel/locking/lockdep.c:5753 [inline]
       lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5718
       process_one_work+0x1220/0x1ad0 kernel/workqueue.c:3206
       process_scheduled_works kernel/workqueue.c:3312 [inline]
       worker_thread+0x6c8/0xf20 kernel/workqueue.c:3390
       kthread+0x2c1/0x3a0 kernel/kthread.c:389
       ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&chan->lock#2/1);
                               lock((wq_completion)hci4#2);
                               lock(&chan->lock#2/1);
  lock((wq_completion)hci4#2);

 *** DEADLOCK ***

1 lock held by kworker/u33:0/66:
 #0: ffff88800057d518 (&chan->lock#2/1){+.+.}-{3:3}, at: l2cap_chan_lock include/net/bluetooth/l2cap.h:827 [inline]
 #0: ffff88800057d518 (&chan->lock#2/1){+.+.}-{3:3}, at: l2cap_conless_channel net/bluetooth/l2cap_core.c:6764 [inline]
 #0: ffff88800057d518 (&chan->lock#2/1){+.+.}-{3:3}, at: l2cap_recv_frame+0x14f6/0x8e20 net/bluetooth/l2cap_core.c:6830

stack backtrace:
CPU: 1 PID: 66 Comm: kworker/u33:0 Not tainted 6.10.0-syzkaller-04472-g51835949dda3 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: hci4 hci_conn_timeout
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:114
 check_noncircular+0x31a/0x400 kernel/locking/lockdep.c:2186
 check_prev_add kernel/locking/lockdep.c:3133 [inline]
 check_prevs_add kernel/locking/lockdep.c:3252 [inline]
 validate_chain kernel/locking/lockdep.c:3868 [inline]
 __lock_acquire+0x2478/0x3b30 kernel/locking/lockdep.c:5136
 lock_acquire kernel/locking/lockdep.c:5753 [inline]
 lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5718
 process_one_work+0x1220/0x1ad0 kernel/workqueue.c:3206
 process_scheduled_works kernel/workqueue.c:3312 [inline]
 worker_thread+0x6c8/0xf20 kernel/workqueue.c:3390
 kthread+0x2c1/0x3a0 kernel/kthread.c:389
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
BUG: workqueue leaked atomic, lock or RCU: kworker/u33:0[66]
     preempt=0x00000000 lock=1->0 RCU=0->0 workfn=hci_conn_timeout
INFO: lockdep is turned off.
CPU: 1 PID: 66 Comm: kworker/u33:0 Not tainted 6.10.0-syzkaller-04472-g51835949dda3 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: hci4 hci_conn_timeout
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x16c/0x1f0 lib/dump_stack.c:114
 process_one_work+0x1170/0x1ad0 kernel/workqueue.c:3252
 process_scheduled_works kernel/workqueue.c:3312 [inline]
 worker_thread+0x6c8/0xf20 kernel/workqueue.c:3390
 kthread+0x2c1/0x3a0 kernel/kthread.c:389
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>