[syzbot] WARNING: kobject bug in erofs_unregister_sysfs

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 91265a6da44d Add linux-next specific files for 20220303
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=11007413700000
kernel config: https://syzkaller.appspot.com/x/.config?x=617f79440a35673a
dashboard link: https://syzkaller.appspot.com/bug?extid=f05ba4652c0471416eaf
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=137f17d9700000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=114ebabd700000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f05ba4...@syzkaller.appspotmail.com

RBP: 00007fff8eeb06e0 R08: 00007fff8eeb0720 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000286 R12: 00000000200000b0
R13: 0000000000000004 R14: 0000000000000005 R15: 0000000000000002
</TASK>
------------[ cut here ]------------
kobject: '(null)' (ffff888077324190): is not initialized, yet kobject_put() is being called.
WARNING: CPU: 0 PID: 3610 at lib/kobject.c:750 kobject_put+0x22b/0x540 lib/kobject.c:750
Modules linked in:
CPU: 0 PID: 3610 Comm: syz-executor471 Not tainted 5.17.0-rc6-next-20220303-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:kobject_put+0x22b/0x540 lib/kobject.c:750
Code: e8 6a 83 67 fd 48 89 e8 48 c1 e8 03 42 80 3c 20 00 0f 85 94 02 00 00 48 8b 75 00 48 89 ea 48 c7 c7 c0 0d 2a 8a e8 c1 5b 07 05 <0f> 0b e9 32 fe ff ff e8 39 83 67 fd 4d 89 f9 48 89 e9 4c 89 f2 49
RSP: 0018:ffffc90003b9fc48 EFLAGS: 00010286
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff88801c67ba80 RSI: ffffffff81602878 RDI: fffff52000773f7b
RBP: ffff888077324190 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff815fd23e R11: 0000000000000000 R12: dffffc0000000000
R13: ffff8880773241cc R14: ffff888073799cf8 R15: ffff8880207dc068
FS: 0000555556165300(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fff8eeb1000 CR3: 000000001ac3f000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
erofs_unregister_sysfs+0x46/0x60 fs/erofs/sysfs.c:225
erofs_put_super+0x37/0xb0 fs/erofs/super.c:771
generic_shutdown_super+0x14c/0x400 fs/super.c:462
kill_block_super+0x97/0xf0 fs/super.c:1394
erofs_kill_sb+0x60/0x190 fs/erofs/super.c:752
deactivate_locked_super+0x94/0x160 fs/super.c:332
get_tree_bdev+0x573/0x760 fs/super.c:1294
vfs_get_tree+0x89/0x2f0 fs/super.c:1497
do_new_mount fs/namespace.c:3025 [inline]
path_mount+0x1320/0x1fa0 fs/namespace.c:3355
do_mount fs/namespace.c:3368 [inline]
__do_sys_mount fs/namespace.c:3576 [inline]
__se_sys_mount fs/namespace.c:3553 [inline]
__x64_sys_mount+0x27f/0x300 fs/namespace.c:3553
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7fa80fa1344a
Code: 48 c7 c2 c0 ff ff ff f7 d8 64 89 02 b8 ff ff ff ff eb d2 e8 a8 00 00 00 0f 1f 84 00 00 00 00 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff8eeb06c8 EFLAGS: 00000286 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fff8eeb0720 RCX: 00007fa80fa1344a
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007fff8eeb06e0
RBP: 00007fff8eeb06e0 R08: 00007fff8eeb0720 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000286 R12: 00000000200000b0
R13: 0000000000000004 R14: 0000000000000005 R15: 0000000000000002
</TASK>


---
This report is generated by a bot. It may contain errors.
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syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

[Gao Xiang]

On Fri, Mar 18, 2022 at 09:39:20AM -0700, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 91265a6da44d Add linux-next specific files for 20220303
> git tree: linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=11007413700000
> kernel config: https://syzkaller.appspot.com/x/.config?x=617f79440a35673a
> dashboard link: https://syzkaller.appspot.com/bug?extid=f05ba4652c0471416eaf
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=137f17d9700000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=114ebabd700000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+f05ba4...@syzkaller.appspotmail.com

It has already been fixed with
https://lore.kernel.org/r/20220315132814...@hust.edu.cn

#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs.git dev

Thanks,
Gao Xiang

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+f05ba4...@syzkaller.appspotmail.com

Tested on:

commit: a1108dcd erofs: rename ctime to mtime
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs.git dev
kernel config: https://syzkaller.appspot.com/x/.config?x=442f8ac61e60a75e

dashboard link: https://syzkaller.appspot.com/bug?extid=f05ba4652c0471416eaf
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

Note: no patches were applied.
Note: testing is done by a robot and is best-effort only.

[syzbot]

syzbot has bisected this issue to:

commit 2768c206f2c3e95c0e5cf2e7f846103fda7cd429
Author: Muchun Song <songm...@bytedance.com>
Date: Thu Mar 3 01:15:36 2022 +0000

mm: list_lru: allocate list_lru_one only when needed

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1495694d700000
start commit: 91265a6da44d Add linux-next specific files for 20220303
git tree: linux-next
final oops: https://syzkaller.appspot.com/x/report.txt?x=1695694d700000
console output: https://syzkaller.appspot.com/x/log.txt?x=1295694d700000

kernel config: https://syzkaller.appspot.com/x/.config?x=617f79440a35673a
dashboard link: https://syzkaller.appspot.com/bug?extid=f05ba4652c0471416eaf

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=137f17d9700000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=114ebabd700000

Reported-by: syzbot+f05ba4...@syzkaller.appspotmail.com
Fixes: 2768c206f2c3 ("mm: list_lru: allocate list_lru_one only when needed")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[Muchun Song]

Does this patch [1] fix the issue? If yes, I am confused why the Fixes tag
should be the commit 2768c206f2c3? What am I missing here?

[1] https://lore.kernel.org/r/20220315132814...@hust.edu.cn

Thanks.

[Gao Xiang]

I think it was an incorrect bisect so we could just ignore it.
The fix is already pending for the next merge window.

Thanks,
Gao Xiang

>
> Thanks.

[Dongliang Mu]

Sometimes syzkaller bisection may make mistakes. Please ignore it.

>
> [1] https://lore.kernel.org/r/20220315132814...@hust.edu.cn
>
> Thanks.
>
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[Dmitry Vyukov]

On Sun, 20 Mar 2022 at 05:19, Dongliang Mu <mudongl...@gmail.com> wrote:
>
> On Sat, Mar 19, 2022 at 10:21 AM Muchun Song <songm...@bytedance.com> wrote:
> >
> > On Sat, Mar 19, 2022 at 6:33 AM syzbot
> > <syzbot+f05ba4...@syzkaller.appspotmail.com> wrote:
> > >
> > > syzbot has bisected this issue to:
> > >
> > > commit 2768c206f2c3e95c0e5cf2e7f846103fda7cd429
> > > Author: Muchun Song <songm...@bytedance.com>
> > > Date: Thu Mar 3 01:15:36 2022 +0000
> > >
> > > mm: list_lru: allocate list_lru_one only when needed
> > >
> > > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1495694d700000
> > > start commit: 91265a6da44d Add linux-next specific files for 20220303
> > > git tree: linux-next
> > > final oops: https://syzkaller.appspot.com/x/report.txt?x=1695694d700000
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=1295694d700000
> > > kernel config: https://syzkaller.appspot.com/x/.config?x=617f79440a35673a
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=f05ba4652c0471416eaf
> > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=137f17d9700000
> > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=114ebabd700000
> > >
> > > Reported-by: syzbot+f05ba4...@syzkaller.appspotmail.com
> > > Fixes: 2768c206f2c3 ("mm: list_lru: allocate list_lru_one only when needed")
> >
> > Does this patch [1] fix the issue? If yes, I am confused why the Fixes tag
> > should be the commit 2768c206f2c3? What am I missing here?
>
> Sometimes syzkaller bisection may make mistakes. Please ignore it.
>
> >
> > [1] https://lore.kernel.org/r/20220315132814...@hust.edu.cn
>

Let's tell syzbot so that it reports new bugs in future:

#syz fix: fs: erofs: add sanity check for kobject in erofs_unregister_sysfs

[Gao Xiang]

Thanks! The fix has been landed upstream now.

Thanks,
Gao Xiang