INFO: task hung in kernfs_remove

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 934272e9 ANDROID: revert "net: ipv4: sysfs_net_ipv4: Add s..
git tree: android-4.14
console output: https://syzkaller.appspot.com/x/log.txt?x=129b63eb200000
kernel config: https://syzkaller.appspot.com/x/.config?x=7c47d7b4a5d0bfb8
dashboard link: https://syzkaller.appspot.com/bug?extid=256bac544b3ac63102a1
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+256bac...@syzkaller.appspotmail.com

[14478] 0 14478 19190 17126 43 3 0
-1000 blkid
[14479] 0 14479 16958 14901 40 3 0
-1000 blkid
[14480] 0 14480 19058 17002 44 3 0
-1000 blkid
[14481] 0 14481 5518 293 16 3 0
-1000 udevd
[14482] 0 14482 5518 293 16 3 0
-1000 udevd
INFO: task kworker/u4:7:2151 blocked for more than 140 seconds.
Not tainted 4.14.104+ #22
[14483] 0 14483 5518 293 16 3 0
-1000 udevd
[14484] 0 14484 5518 294 16 3 0
-1000 udevd
[14485] 0 14485 18924 16871 44 3 0
-1000 blkid
[14486] 0 14486 17908 15823 41 3 0
-1000 blkid
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:7 D26536 2151 2 0x80000000
Workqueue: netns cleanup_net
[14487] 0 14487 17716 15625 41 4 0
-1000 blkid
Call Trace:
[14488] 0 14488 5518 294 16 3 0
-1000 udevd
[14489] 0 14489 17438 15363 41 3 0
-1000 blkid
[14490] 0 14490 18180 16089 56 4 0
-1000 blkid
[14491] 0 14491 18294 16210 43 3 0
-1000 blkid
schedule+0x92/0x1c0 kernel/sched/core.c:3492
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3550
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x559/0x1430 kernel/locking/mutex.c:893
[14492] 0 14492 18142 16081 41 3 0
-1000 blkid
[14493] 0 14493 5518 294 16 3 0
-1000 udevd
[14494] 0 14494 5518 295 16 3 0
-1000 udevd
[14495] 0 14495 5518 294 16 3 0
-1000 udevd
[14496] 0 14496 5518 294 16 3 0
-1000 udevd
[14497] 0 14497 5518 294 16 3 0
-1000 udevd
kernfs_remove+0x17/0x30 fs/kernfs/dir.c:1329
sysfs_remove_dir+0xb1/0xf0 fs/sysfs/dir.c:97
[14498] 0 14498 5518 294 16 3 0
-1000 udevd
[14499] 0 14499 17538 15495 41 3 0
-1000 blkid
kobject_del.part.0+0x35/0xe0 lib/kobject.c:575
kobject_del lib/kobject.c:571 [inline]
kobject_cleanup lib/kobject.c:640 [inline]
kobject_release lib/kobject.c:675 [inline]
kref_put include/linux/kref.h:70 [inline]
kobject_put+0x103/0x200 lib/kobject.c:692
[14503] 0 14503 17122 15085 40 3 0
-1000 blkid
[14504] 0 14504 17106 15033 41 3 0
-1000 blkid
[14505] 0 14505 5518 295 16 3 0
-1000 udevd
[14506] 0 14506 16118 14041 37 3 0
-1000 blkid
[14507] 0 14507 16856 14770 39 3 0
-1000 blkid
[14508] 0 14508 17752 15692 42 3 0
-1000 blkid
[14509] 0 14509 5518 295 16 3 0
-1000 udevd
[14510] 0 14510 5518 295 16 3 0
-1000 udevd
[14511] 0 14511 17412 15363 42 3 0
-1000 blkid
[14512] 0 14512 5518 295 16 3 0
-1000 udevd
[14513] 0 14513 5518 295 16 3 0
-1000 udevd
[14514] 0 14514 5518 295 16 3 0
-1000 udevd
[14515] 0 14515 5518 296 16 3 0
-1000 udevd
INFO: task kworker/0:4:15753 blocked for more than 140 seconds.
[14518] 0 14518 16664 14629 39 4 0
-1000 blkid
Not tainted 4.14.104+ #22
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[14519] 0 14519 5518 295 16 3 0
-1000 udevd
kworker/0:4 D27312 15753 2 0x80000000
[14520] 0 14520 5518 295 16 3 0
-1000 udevd
Workqueue: ipv6_addrconf addrconf_verify_work
[14522] 0 14522 15570 13515 38 3 0
-1000 blkid
[14523] 0 14523 16620 14571 39 3 0
-1000 blkid
Call Trace:
[14524] 0 14524 15994 13911 38 3 0
-1000 blkid
[14526] 0 14526 5518 295 16 3 0
-1000 udevd
[14528] 0 14528 5518 295 16 3 0
-1000 udevd
schedule+0x92/0x1c0 kernel/sched/core.c:3492
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3550
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x559/0x1430 kernel/locking/mutex.c:893
[14529] 0 14529 5518 295 16 3 0
-1000 udevd
[14530] 0 14530 15790 13712 38 3 0
-1000 blkid
[14531] 0 14531 15480 13443 38 3 0
-1000 blkid
[14532] 0 14532 17362 15297 40 3 0
-1000 blkid
addrconf_verify_work+0xa/0x20 net/ipv6/addrconf.c:4431
process_one_work+0x7c6/0x14e0 kernel/workqueue.c:2114
worker_thread+0x5d7/0x1080 kernel/workqueue.c:2248
[14533] 0 14533 16438 14371 39 3 0
-1000 blkid
[14534] 0 14534 15428 13384 37 3 0
-1000 blkid
[14535] 0 14535 5518 295 16 3 0
-1000 udevd
kthread+0x310/0x420 kernel/kthread.c:232
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:402
INFO: task udevd:14803 blocked for more than 140 seconds.
[14536] 0 14536 5518 295 16 3 0
-1000 udevd
[14537] 0 14537 15082 12986 37 3 0
-1000 blkid


---
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[syzbot]

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