======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.1.18/4477 is trying to acquire lock:
ffff88807e6820f0 (kn->active#61){++++}-{0:0}, at: __kernfs_remove+0x3f4/0x6c0 fs/kernfs/dir.c:1461

but task is already holding lock:
ffffffff8d841188 (serio_mutex){+.+.}-{3:3}, at: serio_unregister_port+0x2b/0x150 drivers/input/serio/serio.c:704

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (serio_mutex){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x12d/0xae0 kernel/locking/mutex.c:747
       drvctl_store+0x2a/0xae0 drivers/input/serio/serio.c:385
       kernfs_fop_write_iter+0x3a0/0x520 fs/kernfs/file.c:352
       call_write_iter include/linux/fs.h:2265 [inline]
       new_sync_write fs/read_write.c:491 [inline]
       vfs_write+0x482/0x9a0 fs/read_write.c:584
       ksys_write+0x14d/0x260 fs/read_write.c:637
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #0 (kn->active#61){++++}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3095 [inline]
       check_prevs_add kernel/locking/lockdep.c:3214 [inline]
       validate_chain kernel/locking/lockdep.c:3830 [inline]
       __lock_acquire+0x2d18/0x7c40 kernel/locking/lockdep.c:5063
       lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5676
       kernfs_drain+0x31a/0x6d0 fs/kernfs/dir.c:499
       __kernfs_remove+0x3f4/0x6c0 fs/kernfs/dir.c:1461
       kernfs_remove_by_name_ns+0xd8/0x150 fs/kernfs/dir.c:1667
       kernfs_remove_by_name include/linux/kernfs.h:622 [inline]
       remove_files fs/sysfs/group.c:28 [inline]
       sysfs_remove_group+0xfd/0x290 fs/sysfs/group.c:288
       sysfs_remove_groups+0x50/0xa0 fs/sysfs/group.c:312
       device_remove_groups drivers/base/core.c:2759 [inline]
       device_remove_attrs+0x1c8/0x270 drivers/base/core.c:2973
       device_del+0x637/0xa80 drivers/base/core.c:3899
       serio_destroy_port+0x34a/0x470 drivers/input/serio/serio.c:570
       serio_unregister_port+0x12c/0x150 drivers/input/serio/serio.c:706
       userio_char_release+0x7f/0xb0 drivers/input/serio/userio.c:111
       __fput+0x20a/0x8b0 fs/file_table.c:320
       task_work_run+0x1d0/0x260 kernel/task_work.c:203
       resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
       exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
       exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
       __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
       syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
       do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(serio_mutex);
                               lock(kn->active#61);
                               lock(serio_mutex);
  lock(kn->active#61);

 *** DEADLOCK ***

1 lock held by syz.1.18/4477:
 #0: ffffffff8d841188 (serio_mutex){+.+.}-{3:3}, at: serio_unregister_port+0x2b/0x150 drivers/input/serio/serio.c:704

stack backtrace:
CPU: 0 PID: 4477 Comm: syz.1.18 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
 check_noncircular+0x296/0x330 kernel/locking/lockdep.c:2170
 check_prev_add kernel/locking/lockdep.c:3095 [inline]
 check_prevs_add kernel/locking/lockdep.c:3214 [inline]
 validate_chain kernel/locking/lockdep.c:3830 [inline]
 __lock_acquire+0x2d18/0x7c40 kernel/locking/lockdep.c:5063
 lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5676
 kernfs_drain+0x31a/0x6d0 fs/kernfs/dir.c:499
 __kernfs_remove+0x3f4/0x6c0 fs/kernfs/dir.c:1461
 kernfs_remove_by_name_ns+0xd8/0x150 fs/kernfs/dir.c:1667
 kernfs_remove_by_name include/linux/kernfs.h:622 [inline]
 remove_files fs/sysfs/group.c:28 [inline]
 sysfs_remove_group+0xfd/0x290 fs/sysfs/group.c:288
 sysfs_remove_groups+0x50/0xa0 fs/sysfs/group.c:312
 device_remove_groups drivers/base/core.c:2759 [inline]
 device_remove_attrs+0x1c8/0x270 drivers/base/core.c:2973
 device_del+0x637/0xa80 drivers/base/core.c:3899
 serio_destroy_port+0x34a/0x470 drivers/input/serio/serio.c:570
 serio_unregister_port+0x12c/0x150 drivers/input/serio/serio.c:706
 userio_char_release+0x7f/0xb0 drivers/input/serio/userio.c:111
 __fput+0x20a/0x8b0 fs/file_table.c:320
 task_work_run+0x1d0/0x260 kernel/task_work.c:203
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f46f559e0d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffdff0b77e8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007ffdff0b78d0 RCX: 00007f46f559e0d9
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 0000000000017974 R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b2e020000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f46f5825fac R14: 00007f46f5825fa8 R15: 00007f46f5825fa0
 </TASK>