Kernel bug: BUG: workqueue leaked atomic, lock or RCU: kworker/u33:NUM[NUM]
Subsystem: bluetooth
Status: fixed

Crash report:
BUG: workqueue leaked atomic, lock or RCU: kworker/u33:2[5195]
     preempt=0x00000000 lock=0->1 RCU=0->0 workfn=hci_rx_work
1 lock held by kworker/u33:2/5195:
 #0: ffff88801ac26518 (&chan->lock/1){+.+.}-{3:3}, at: l2cap_chan_lock include/net/bluetooth/l2cap.h:827 [inline]
 #0: ffff88801ac26518 (&chan->lock/1){+.+.}-{3:3}, at: l2cap_conless_channel net/bluetooth/l2cap_core.c:6764 [inline]
 #0: ffff88801ac26518 (&chan->lock/1){+.+.}-{3:3}, at: l2cap_recv_frame+0x14f2/0x8ea0 net/bluetooth/l2cap_core.c:6830
CPU: 3 PID: 5195 Comm: kworker/u33:2 Not tainted 6.10.0-rc6-syzkaller-00215-g22f902dfc51e #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: hci0 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+0x11ea/0x1b40 kernel/workqueue.c:3269
 process_scheduled_works kernel/workqueue.c:3329 [inline]
 worker_thread+0x6c8/0xf30 kernel/workqueue.c:3409
 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-rc6-syzkaller-00215-g22f902dfc51e #0 Not tainted
------------------------------------------------------
kworker/u33:2/5195 is trying to acquire lock:
ffff88801ef0a948 ((wq_completion)hci0#2){+.+.}-{0:0}, at: process_one_work+0x1277/0x1b40 kernel/workqueue.c:3223

but task is already holding lock:
ffff88801ac26518 (&chan->lock/1){+.+.}-{3:3}, at: l2cap_chan_lock include/net/bluetooth/l2cap.h:827 [inline]
ffff88801ac26518 (&chan->lock/1){+.+.}-{3:3}, at: l2cap_conless_channel net/bluetooth/l2cap_core.c:6764 [inline]
ffff88801ac26518 (&chan->lock/1){+.+.}-{3:3}, at: l2cap_recv_frame+0x14f2/0x8ea0 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/1){+.+.}-{3:3}:
       __lock_release kernel/locking/lockdep.c:5468 [inline]
       lock_release+0x33e/0x6c0 kernel/locking/lockdep.c:5774
       process_one_work+0xa96/0x1b40 kernel/workqueue.c:3255
       process_scheduled_works kernel/workqueue.c:3329 [inline]
       worker_thread+0x6c8/0xf30 kernel/workqueue.c:3409
       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)hci0#2){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3134 [inline]
       check_prevs_add kernel/locking/lockdep.c:3253 [inline]
       validate_chain kernel/locking/lockdep.c:3869 [inline]
       __lock_acquire+0x2478/0x3b30 kernel/locking/lockdep.c:5137
       lock_acquire kernel/locking/lockdep.c:5754 [inline]
       lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5719
       process_one_work+0x12a6/0x1b40 kernel/workqueue.c:3223
       process_scheduled_works kernel/workqueue.c:3329 [inline]
       worker_thread+0x6c8/0xf30 kernel/workqueue.c:3409
       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/1);
                               lock((wq_completion)hci0#2);
                               lock(&chan->lock/1);
  lock((wq_completion)hci0#2);

 *** DEADLOCK ***

1 lock held by kworker/u33:2/5195:
 #0: ffff88801ac26518 (&chan->lock/1){+.+.}-{3:3}, at: l2cap_chan_lock include/net/bluetooth/l2cap.h:827 [inline]
 #0: ffff88801ac26518 (&chan->lock/1){+.+.}-{3:3}, at: l2cap_conless_channel net/bluetooth/l2cap_core.c:6764 [inline]
 #0: ffff88801ac26518 (&chan->lock/1){+.+.}-{3:3}, at: l2cap_recv_frame+0x14f2/0x8ea0 net/bluetooth/l2cap_core.c:6830

stack backtrace:
CPU: 2 PID: 5195 Comm: kworker/u33:2 Not tainted 6.10.0-rc6-syzkaller-00215-g22f902dfc51e #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: hci0 hci_cmd_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:2187
 check_prev_add kernel/locking/lockdep.c:3134 [inline]
 check_prevs_add kernel/locking/lockdep.c:3253 [inline]
 validate_chain kernel/locking/lockdep.c:3869 [inline]
 __lock_acquire+0x2478/0x3b30 kernel/locking/lockdep.c:5137
 lock_acquire kernel/locking/lockdep.c:5754 [inline]
 lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5719
 process_one_work+0x12a6/0x1b40 kernel/workqueue.c:3223
 process_scheduled_works kernel/workqueue.c:3329 [inline]
 worker_thread+0x6c8/0xf30 kernel/workqueue.c:3409
 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>
Bluetooth: hci0: command tx timeout
BUG: workqueue leaked atomic, lock or RCU: kworker/u33:2[5195]
     preempt=0x00000000 lock=1->0 RCU=0->0 workfn=hci_cmd_timeout
INFO: lockdep is turned off.
CPU: 2 PID: 5195 Comm: kworker/u33:2 Not tainted 6.10.0-rc6-syzkaller-00215-g22f902dfc51e #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: hci0 hci_cmd_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+0x11ea/0x1b40 kernel/workqueue.c:3269
 process_scheduled_works kernel/workqueue.c:3329 [inline]
 worker_thread+0x6c8/0xf30 kernel/workqueue.c:3409
 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>
Bluetooth: hci0: command tx timeout
Bluetooth: hci0: command tx timeout
Bluetooth: hci0: command tx timeout