syzbot

================================
WARNING: inconsistent lock state
syzkaller #0 Tainted: G             L     
--------------------------------
inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
syz.4.4899/23451 [HC0[0]:SC0[2]:HE1:SE0] takes:
ffff8880333c1068 (&dev->spinlock){?...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:347 [inline]
ffff8880333c1068 (&dev->spinlock){?...}-{3:3}, at: waveform_ao_cancel+0x96/0x150 drivers/comedi/drivers/comedi_test.c:628
{IN-HARDIRQ-W} state was registered at:
  lock_acquire kernel/locking/lockdep.c:5868 [inline]
  lock_acquire+0x1cf/0x380 kernel/locking/lockdep.c:5825
  __raw_spin_lock include/linux/spinlock_api_smp.h:158 [inline]
  _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
  spin_lock include/linux/spinlock.h:341 [inline]
  das16m1_interrupt+0x68/0x120 drivers/comedi/drivers/das16m1.c:460
  __handle_irq_event_percpu+0x232/0x8e0 kernel/irq/handle.c:209
  handle_irq_event_percpu kernel/irq/handle.c:246 [inline]
  handle_irq_event+0xab/0x1e0 kernel/irq/handle.c:263
  handle_edge_irq+0x375/0x970 kernel/irq/chip.c:855
  generic_handle_irq_desc include/linux/irqdesc.h:186 [inline]
  handle_irq arch/x86/kernel/irq.c:262 [inline]
  call_irq_handler arch/x86/kernel/irq.c:318 [inline]
  __common_interrupt+0xd8/0x2f0 arch/x86/kernel/irq.c:333
  common_interrupt+0xb9/0xe0 arch/x86/kernel/irq.c:326
  asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:688
  __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:178 [inline]
  _raw_spin_unlock_irqrestore+0x31/0x80 kernel/locking/spinlock.c:194
  spin_unlock_irqrestore include/linux/spinlock.h:407 [inline]
  uart_port_unlock_irqrestore include/linux/serial_core.h:788 [inline]
  autoconfig drivers/tty/serial/8250/8250_port.c:1201 [inline]
  serial8250_config_port drivers/tty/serial/8250/8250_port.c:3097 [inline]
  serial8250_config_port+0x1897/0x4ec0 drivers/tty/serial/8250/8250_port.c:3080
  univ8250_config_port+0x25a/0x380 drivers/tty/serial/8250/8250_rsa.c:72
  uart_do_autoconfig drivers/tty/serial/serial_core.c:1173 [inline]
  uart_ioctl+0x14cc/0x2ef0 drivers/tty/serial/serial_core.c:1565
  tty_ioctl+0x26a/0x1690 drivers/tty/tty_io.c:2792
  vfs_ioctl fs/ioctl.c:51 [inline]
  __do_sys_ioctl fs/ioctl.c:597 [inline]
  __se_sys_ioctl fs/ioctl.c:583 [inline]
  __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
  do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94
  entry_SYSCALL_64_after_hwframe+0x77/0x7f
irq event stamp: 291252
hardirqs last  enabled at (291251): [<ffffffff8b93d1e2>] __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:178 [inline]
hardirqs last  enabled at (291251): [<ffffffff8b93d1e2>] _raw_spin_unlock_irqrestore+0x52/0x80 kernel/locking/spinlock.c:194
hardirqs last disabled at (291250): [<ffffffff8b93cef2>] __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:130 [inline]
hardirqs last disabled at (291250): [<ffffffff8b93cef2>] _raw_spin_lock_irqsave+0x52/0x60 kernel/locking/spinlock.c:162
softirqs last  enabled at (291198): [<ffffffff81c9240f>] __do_softirq kernel/softirq.c:656 [inline]
softirqs last  enabled at (291198): [<ffffffff81c9240f>] invoke_softirq kernel/softirq.c:496 [inline]
softirqs last  enabled at (291198): [<ffffffff81c9240f>] __irq_exit_rcu+0xef/0x150 kernel/softirq.c:723
softirqs last disabled at (291252): [<ffffffff88f58a46>] spin_lock_bh include/linux/spinlock.h:347 [inline]
softirqs last disabled at (291252): [<ffffffff88f58a46>] waveform_ao_cancel+0x96/0x150 drivers/comedi/drivers/comedi_test.c:628

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&dev->spinlock);
  <Interrupt>
    lock(&dev->spinlock);

 *** DEADLOCK ***

1 lock held by syz.4.4899/23451:
 #0: ffff8880333c10f8 (&dev->mutex#4){+.+.}-{4:4}, at: comedi_close+0x7b/0x470 drivers/comedi/comedi_fops.c:3029

stack backtrace:
CPU: 0 UID: 0 PID: 23451 Comm: syz.4.4899 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_usage_bug.part.0+0x257/0x340 kernel/locking/lockdep.c:4042
 print_usage_bug kernel/locking/lockdep.c:4010 [inline]
 valid_state kernel/locking/lockdep.c:4056 [inline]
 mark_lock_irq kernel/locking/lockdep.c:4267 [inline]
 mark_lock+0x74a/0xa20 kernel/locking/lockdep.c:4753
 mark_usage kernel/locking/lockdep.c:4662 [inline]
 __lock_acquire+0x7f1/0x2630 kernel/locking/lockdep.c:5191
 lock_acquire kernel/locking/lockdep.c:5868 [inline]
 lock_acquire+0x1cf/0x380 kernel/locking/lockdep.c:5825
 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:150 [inline]
 _raw_spin_lock_bh+0x33/0x40 kernel/locking/spinlock.c:178
 spin_lock_bh include/linux/spinlock.h:347 [inline]
 waveform_ao_cancel+0x96/0x150 drivers/comedi/drivers/comedi_test.c:628
 do_cancel+0xf4/0x180 drivers/comedi/comedi_fops.c:818
 comedi_close+0x2f6/0x470 drivers/comedi/comedi_fops.c:3036
 __fput+0x3ff/0xb40 fs/file_table.c:469
 task_work_run+0x150/0x240 kernel/task_work.c:233
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x8b8/0x2b60 kernel/exit.c:976
 do_group_exit+0xd5/0x2a0 kernel/exit.c:1118
 get_signal+0x1ec7/0x21e0 kernel/signal.c:3034
 arch_do_signal_or_restart+0x91/0x7a0 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
 exit_to_user_mode_loop+0x86/0x4a0 kernel/entry/common.c:98
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
 do_syscall_64+0x67c/0xf80 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff95299c799
Code: Unable to access opcode bytes at 0x7ff95299c76f.
RSP: 002b:00007ff95388b028 EFLAGS: 00000246 ORIG_RAX: 000000000000012b
RAX: 0000000000010106 RBX: 00007ff952c16090 RCX: 00007ff95299c799
RDX: 0000000000010106 RSI: 00002000000000c0 RDI: 0000000000000003
RBP: 00007ff952a32c99 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff952c16128 R14: 00007ff952c16090 R15: 00007ffc7c0256d8
 </TASK>