BUG: workqueue leaked atomic, lock or RCU: kworker/u33:8[5350]
     preempt=0x00000000 lock=0->1 RCU=0->0 workfn=hci_rx_work
1 lock held by kworker/u33:8/5350:
 #0: ffff88802a8a8518 (&chan->lock#2/1){+.+.}-{3:3}, at: l2cap_chan_lock include/net/bluetooth/l2cap.h:827 [inline]
 #0: ffff88802a8a8518 (&chan->lock#2/1){+.+.}-{3:3}, at: l2cap_conless_channel net/bluetooth/l2cap_core.c:6764 [inline]
 #0: ffff88802a8a8518 (&chan->lock#2/1){+.+.}-{3:3}, at: l2cap_recv_frame+0x14f6/0x8eb0 net/bluetooth/l2cap_core.c:6830
CPU: 2 UID: 0 PID: 5350 Comm: kworker/u33:8 Not tainted 6.11.0-rc2-syzkaller-00027-g6a0e38264012 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: hci3 hci_rx_work
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:93 [inline]
 dump_stack_lvl+0x16c/0x1f0 lib/dump_stack.c:119
 process_one_work+0x11ea/0x1b40 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
6.11.0-rc2-syzkaller-00027-g6a0e38264012 #0 Not tainted
------------------------------------------------------
kworker/u33:8/5350 is trying to acquire lock:
ffff88804676b148 ((wq_completion)hci4#2){+.+.}-{0:0}, at: process_one_work+0x1277/0x1b40 kernel/workqueue.c:3206

but task is already holding lock:
ffff88802a8a8518 (&chan->lock#2/1){+.+.}-{3:3}, at: l2cap_chan_lock include/net/bluetooth/l2cap.h:827 [inline]
ffff88802a8a8518 (&chan->lock#2/1){+.+.}-{3:3}, at: l2cap_conless_channel net/bluetooth/l2cap_core.c:6764 [inline]
ffff88802a8a8518 (&chan->lock#2/1){+.+.}-{3:3}, at: l2cap_recv_frame+0x14f6/0x8eb0 net/bluetooth/l2cap_core.c:6830

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&chan->lock#2/1){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x175/0x9c0 kernel/locking/mutex.c:752
       l2cap_chan_lock include/net/bluetooth/l2cap.h:827 [inline]
       l2cap_conless_channel net/bluetooth/l2cap_core.c:6764 [inline]
       l2cap_recv_frame+0x14f6/0x8eb0 net/bluetooth/l2cap_core.c:6830
       l2cap_recv_acldata+0x9b4/0xb70 net/bluetooth/l2cap_core.c:7513
       hci_acldata_packet net/bluetooth/hci_core.c:3790 [inline]
       hci_rx_work+0xaab/0x1610 net/bluetooth/hci_core.c:4027
       process_one_work+0x9c5/0x1b40 kernel/workqueue.c:3231
       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

-> #1 ((work_completion)(&hdev->rx_work)){+.+.}-{0:0}:
       process_one_work+0x927/0x1b40 kernel/workqueue.c:3207
       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+0x24ed/0x3cb0 kernel/locking/lockdep.c:5142
       lock_acquire kernel/locking/lockdep.c:5759 [inline]
       lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5724
       process_one_work+0x12a6/0x1b40 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:

Chain exists of:
  (wq_completion)hci4#2 --> (work_completion)(&hdev->rx_work) --> &chan->lock#2/1

 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

1 lock held by kworker/u33:8/5350:
 #0: ffff88802a8a8518 (&chan->lock#2/1){+.+.}-{3:3}, at: l2cap_chan_lock include/net/bluetooth/l2cap.h:827 [inline]
 #0: ffff88802a8a8518 (&chan->lock#2/1){+.+.}-{3:3}, at: l2cap_conless_channel net/bluetooth/l2cap_core.c:6764 [inline]
 #0: ffff88802a8a8518 (&chan->lock#2/1){+.+.}-{3:3}, at: l2cap_recv_frame+0x14f6/0x8eb0 net/bluetooth/l2cap_core.c:6830

stack backtrace:
CPU: 2 UID: 0 PID: 5350 Comm: kworker/u33:8 Not tainted 6.11.0-rc2-syzkaller-00027-g6a0e38264012 #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:93 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:119
 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+0x24ed/0x3cb0 kernel/locking/lockdep.c:5142
 lock_acquire kernel/locking/lockdep.c:5759 [inline]
 lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5724
 process_one_work+0x12a6/0x1b40 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/u33:8[5350]
     preempt=0x00000000 lock=1->0 RCU=0->0 workfn=hci_conn_timeout
INFO: lockdep is turned off.
CPU: 2 UID: 0 PID: 5350 Comm: kworker/u33:8 Not tainted 6.11.0-rc2-syzkaller-00027-g6a0e38264012 #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:93 [inline]
 dump_stack_lvl+0x16c/0x1f0 lib/dump_stack.c:119
 process_one_work+0x11ea/0x1b40 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>