general protection fault in debugfs_remove

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 775d01b6 Linux 4.14.154
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=10f0a8cee00000
kernel config: https://syzkaller.appspot.com/x/.config?x=90a13857da9a45b6
dashboard link: https://syzkaller.appspot.com/bug?extid=347bae0a78ffdaeaea26
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+347bae...@syzkaller.appspotmail.com

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 0 PID: 24 Comm: kworker/0:1 Not tainted 4.14.154 #0
kobject: '7:0' (ffff888089aa96d0): kobject_add_internal: parent: 'bdi',
set: 'devices'
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: events __blk_release_queue
task: ffff8880a9e58640 task.stack: ffff8880a9e60000
RIP: 0010:__lock_acquire+0x1ba/0x4620 kernel/locking/lockdep.c:3365
kobject: '7:0' (ffff888089aa96d0): kobject_uevent_env
RSP: 0018:ffff8880a9e67a30 EFLAGS: 00010006
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000028 RSI: 0000000000000000 RDI: 0000000000000001
RBP: ffff8880a9e67bd8 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: ffff8880a9e58640 R12: 0000000000000140
R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff8880aee00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
kobject: '7:0' (ffff888089aa96d0): fill_kobj_path: path
= '/devices/virtual/bdi/7:0'
CR2: 0000000000625208 CR3: 0000000095812000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
kobject: 'loop0' (ffff88808fe08520): kobject_add_internal: parent: 'block',
set: 'devices'
lock_acquire+0x16f/0x430 kernel/locking/lockdep.c:3994
down_write+0x38/0x90 kernel/locking/rwsem.c:54
kobject: 'loop0' (ffff88808fe08520): kobject_uevent_env
inode_lock include/linux/fs.h:718 [inline]
debugfs_remove fs/debugfs/inode.c:663 [inline]
debugfs_remove+0x85/0x120 fs/debugfs/inode.c:654
blk_trace_free+0x62/0x140 kernel/trace/blktrace.c:325
blk_trace_cleanup kernel/trace/blktrace.c:351 [inline]
blk_trace_remove+0x59/0x80 kernel/trace/blktrace.c:364
blk_trace_shutdown+0x4f/0x60 kernel/trace/blktrace.c:728
__blk_release_queue+0x22e/0x4d0 block/blk-sysfs.c:830
process_one_work+0x863/0x1600 kernel/workqueue.c:2114
kobject: 'loop0' (ffff88808fe08520): kobject_uevent_env: uevent_suppress
caused the event to drop!
worker_thread+0x5d9/0x1050 kernel/workqueue.c:2248
kthread+0x319/0x430 kernel/kthread.c:232
kobject: 'holders' (ffff88809f446d80): kobject_add_internal:
parent: 'loop0', set: '<NULL>'
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404
Code:
kobject: 'slaves' (ffff8880611dda80): kobject_add_internal:
parent: 'loop0', set: '<NULL>'
00 c7 40 18 00 00 00 00 48 8d 65 d8 44 89 e0
kobject: 'loop0' (ffff88808fe08520): kobject_uevent_env
5b 41 5c 41 5d 41 5e 41 5f 5d c3 48 b8 00 00 00 00
kobject: 'loop0' (ffff88808fe08520): fill_kobj_path: path
= '/devices/virtual/block/loop0'
00 fc ff df 4c 89 e2 48 c1 ea 03 <80> 3c 02 00 0f 85
kobject: 'queue' (ffff888060790e08): kobject_add_internal: parent: 'loop0',
set: '<NULL>'
ac 2e 00 00 49 81 3c 24 a0 c2 5d 88
kobject: 'mq' (ffff888060790e48): kobject_add_internal: parent: 'loop0',
set: '<NULL>'
0f 84 43
RIP: __lock_acquire+0x1ba/0x4620 kernel/locking/lockdep.c:3365 RSP:
ffff8880a9e67a30
---[ end trace be2c1426ecb70b09 ]---
kobject: 'mq' (ffff888060790e48): kobject_uevent_env


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.