syzbot

BUG: workqueue leaked atomic, lock or RCU: kworker/u9:0[52]
     preempt=0x00000000 lock=0->1 RCU=0->0 workfn=hci_rx_work
1 lock held by kworker/u9:0/52:
 #0: ffff0000d9876518 (&chan->lock/1){+.+.}-{3:3}, at: l2cap_chan_lock include/net/bluetooth/l2cap.h:827 [inline]
 #0: ffff0000d9876518 (&chan->lock/1){+.+.}-{3:3}, at: l2cap_conless_channel net/bluetooth/l2cap_core.c:6764 [inline]
 #0: ffff0000d9876518 (&chan->lock/1){+.+.}-{3:3}, at: l2cap_recv_frame+0x610/0xc934 net/bluetooth/l2cap_core.c:6830
CPU: 1 PID: 52 Comm: kworker/u9:0 Not tainted 6.10.0-rc7-syzkaller-gef445d1539dd #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
Workqueue: hci0 hci_rx_work
Call trace:
 dump_backtrace+0x1b8/0x1e4 arch/arm64/kernel/stacktrace.c:317
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:324
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xe4/0x150 lib/dump_stack.c:114
 dump_stack+0x1c/0x28 lib/dump_stack.c:123
 process_one_work+0xdc0/0x15b8 kernel/workqueue.c:3269
 process_scheduled_works kernel/workqueue.c:3329 [inline]
 worker_thread+0x938/0xecc kernel/workqueue.c:3409
 kthread+0x288/0x310 kernel/kthread.c:389
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:860

======================================================
WARNING: possible circular locking dependency detected
6.10.0-rc7-syzkaller-gef445d1539dd #0 Not tainted
------------------------------------------------------
kworker/u9:0/52 is trying to acquire lock:
ffff0000d385e948 ((wq_completion)hci0#2){+.+.}-{0:0}, at: process_one_work+0x624/0x15b8 kernel/workqueue.c:3222

but task is already holding lock:
ffff0000d9876518 (&chan->lock/1){+.+.}-{3:3}, at: l2cap_chan_lock include/net/bluetooth/l2cap.h:827 [inline]
ffff0000d9876518 (&chan->lock/1){+.+.}-{3:3}, at: l2cap_conless_channel net/bluetooth/l2cap_core.c:6764 [inline]
ffff0000d9876518 (&chan->lock/1){+.+.}-{3:3}, at: l2cap_recv_frame+0x610/0xc934 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+0x334/0x9b8 kernel/locking/lockdep.c:5774
       process_one_work+0x8a0/0x15b8 kernel/workqueue.c:3255
       process_scheduled_works kernel/workqueue.c:3329 [inline]
       worker_thread+0x938/0xecc kernel/workqueue.c:3409
       kthread+0x288/0x310 kernel/kthread.c:389
       ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:860

-> #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+0x3384/0x763c kernel/locking/lockdep.c:5137
       lock_acquire+0x240/0x728 kernel/locking/lockdep.c:5754
       process_one_work+0x668/0x15b8 kernel/workqueue.c:3223
       process_scheduled_works kernel/workqueue.c:3329 [inline]
       worker_thread+0x938/0xecc kernel/workqueue.c:3409
       kthread+0x288/0x310 kernel/kthread.c:389
       ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:860

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/u9:0/52:
 #0: ffff0000d9876518 (&chan->lock/1){+.+.}-{3:3}, at: l2cap_chan_lock include/net/bluetooth/l2cap.h:827 [inline]
 #0: ffff0000d9876518 (&chan->lock/1){+.+.}-{3:3}, at: l2cap_conless_channel net/bluetooth/l2cap_core.c:6764 [inline]
 #0: ffff0000d9876518 (&chan->lock/1){+.+.}-{3:3}, at: l2cap_recv_frame+0x610/0xc934 net/bluetooth/l2cap_core.c:6830

stack backtrace:
CPU: 1 PID: 52 Comm: kworker/u9:0 Not tainted 6.10.0-rc7-syzkaller-gef445d1539dd #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
Workqueue: hci0 hci_cmd_timeout
Call trace:
 dump_backtrace+0x1b8/0x1e4 arch/arm64/kernel/stacktrace.c:317
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:324
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xe4/0x150 lib/dump_stack.c:114
 dump_stack+0x1c/0x28 lib/dump_stack.c:123
 print_circular_bug+0x150/0x1b8 kernel/locking/lockdep.c:2060
 check_noncircular+0x310/0x404 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+0x3384/0x763c kernel/locking/lockdep.c:5137
 lock_acquire+0x240/0x728 kernel/locking/lockdep.c:5754
 process_one_work+0x668/0x15b8 kernel/workqueue.c:3223
 process_scheduled_works kernel/workqueue.c:3329 [inline]
 worker_thread+0x938/0xecc kernel/workqueue.c:3409
 kthread+0x288/0x310 kernel/kthread.c:389
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:860
Bluetooth: hci0: command tx timeout
BUG: workqueue leaked atomic, lock or RCU: kworker/u9:0[52]
     preempt=0x00000000 lock=1->0 RCU=0->0 workfn=hci_cmd_timeout
INFO: lockdep is turned off.
CPU: 1 PID: 52 Comm: kworker/u9:0 Not tainted 6.10.0-rc7-syzkaller-gef445d1539dd #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
Workqueue: hci0 hci_cmd_timeout
Call trace:
 dump_backtrace+0x1b8/0x1e4 arch/arm64/kernel/stacktrace.c:317
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:324
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xe4/0x150 lib/dump_stack.c:114
 dump_stack+0x1c/0x28 lib/dump_stack.c:123
 process_one_work+0xdc0/0x15b8 kernel/workqueue.c:3269
 process_scheduled_works kernel/workqueue.c:3329 [inline]
 worker_thread+0x938/0xecc kernel/workqueue.c:3409
 kthread+0x288/0x310 kernel/kthread.c:389
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:860
Bluetooth: hci0: command tx timeout
Bluetooth: hci0: command tx timeout
Bluetooth: hci0: command tx timeout