[syzbot] WARNING in z_erofs_lz4_decompress

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 60e8840126bd Add linux-next specific files for 20211018
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=125932af300000
kernel config: https://syzkaller.appspot.com/x/.config?x=4bd44cafcda7632e
dashboard link: https://syzkaller.appspot.com/bug?extid=d8aaffc3719597e8cfb4
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d8aaff...@syzkaller.appspotmail.com

erofs: (device loop4): z_erofs_lz4_decompress_mem: failed to decompress -4100 in[4096, 0] out[9000]
------------[ cut here ]------------
WARNING: CPU: 1 PID: 9895 at fs/erofs/decompressor.c:230 z_erofs_lz4_decompress_mem fs/erofs/decompressor.c:227 [inline]
WARNING: CPU: 1 PID: 9895 at fs/erofs/decompressor.c:230 z_erofs_lz4_decompress+0x841/0x1400 fs/erofs/decompressor.c:289
Modules linked in:
CPU: 1 PID: 9895 Comm: kworker/u5:3 Not tainted 5.15.0-rc5-next-20211018-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: erofs_unzipd z_erofs_decompressqueue_work
RIP: 0010:z_erofs_lz4_decompress_mem fs/erofs/decompressor.c:230 [inline]
RIP: 0010:z_erofs_lz4_decompress+0x841/0x1400 fs/erofs/decompressor.c:289
Code: e9 03 80 3c 11 00 0f 85 8c 0a 00 00 41 56 48 8b 7d 00 45 89 e9 89 d9 48 c7 c2 20 eb fb 89 48 c7 c6 40 ed fb 89 e8 ee 5d 85 05 <0f> 0b 48 b8 00 00 00 00 00 fc ff df 48 8b 4c 24 08 5f 48 89 ca 48
RSP: 0018:ffffc90001b3f718 EFLAGS: 00010286
RAX: 0000000000000000 RBX: ffffffffffffeffc RCX: 0000000000000000
RDX: ffff8880795b3a00 RSI: ffffffff815ef308 RDI: fffff52000367ed3
RBP: ffffc90001b3f858 R08: 0000000000000063 R09: 0000000000000000
R10: ffffffff815e90de R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000002328 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2ef25000 CR3: 000000002b3f7000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
z_erofs_decompress_pcluster.isra.0+0x1389/0x2450 fs/erofs/zdata.c:977
z_erofs_decompress_queue fs/erofs/zdata.c:1055 [inline]
z_erofs_decompressqueue_work+0xe0/0x170 fs/erofs/zdata.c:1066
process_one_work+0x9b2/0x1690 kernel/workqueue.c:2297
worker_thread+0x658/0x11f0 kernel/workqueue.c:2444
kthread+0x405/0x4f0 kernel/kthread.c:327
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>


---
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[Gao Xiang]

Hi,

On Sat, Oct 23, 2021 at 07:25:20PM -0700, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 60e8840126bd Add linux-next specific files for 20211018
> git tree: linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=125932af300000
> kernel config: https://syzkaller.appspot.com/x/.config?x=4bd44cafcda7632e
> dashboard link: https://syzkaller.appspot.com/bug?extid=d8aaffc3719597e8cfb4
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+d8aaff...@syzkaller.appspotmail.com
>
> erofs: (device loop4): z_erofs_lz4_decompress_mem: failed to decompress -4100 in[4096, 0] out[9000]
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 9895 at fs/erofs/decompressor.c:230 z_erofs_lz4_decompress_mem fs/erofs/decompressor.c:227 [inline]
> WARNING: CPU: 1 PID: 9895 at fs/erofs/decompressor.c:230 z_erofs_lz4_decompress+0x841/0x1400 fs/erofs/decompressor.c:289

If you fuzz compressed data, that is what you'd expect..

Thanks,
Gao Xiang

[Gao Xiang]

Hi Dmitry,

On Mon, Oct 25, 2021 at 08:55:51AM +0200, Dmitry Vyukov wrote:

> On Mon, 25 Oct 2021 at 02:17, Gao Xiang <hsia...@linux.alibaba.com> wrote:
> >
> > Hi,
> >
> > On Sat, Oct 23, 2021 at 07:25:20PM -0700, syzbot wrote:
> > > Hello,
> > >
> > > syzbot found the following issue on:
> > >
> > > HEAD commit: 60e8840126bd Add linux-next specific files for 20211018
> > > git tree: linux-next
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=125932af300000
> > > kernel config: https://syzkaller.appspot.com/x/.config?x=4bd44cafcda7632e
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=d8aaffc3719597e8cfb4
> > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > >
> > > Unfortunately, I don't have any reproducer for this issue yet.
> > >
> > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > Reported-by: syzbot+d8aaff...@syzkaller.appspotmail.com
> > >
> > > erofs: (device loop4): z_erofs_lz4_decompress_mem: failed to decompress -4100 in[4096, 0] out[9000]
> > > ------------[ cut here ]------------
> > > WARNING: CPU: 1 PID: 9895 at fs/erofs/decompressor.c:230 z_erofs_lz4_decompress_mem fs/erofs/decompressor.c:227 [inline]
> > > WARNING: CPU: 1 PID: 9895 at fs/erofs/decompressor.c:230 z_erofs_lz4_decompress+0x841/0x1400 fs/erofs/decompressor.c:289
> >
> > If you fuzz compressed data, that is what you'd expect..
>

> Hi Gao,
>
> If you mean this is not a kernel bug, then the code should not use WARN.
> WARN if for kernel bugs and is recognized as such by all testing
> systems and humans.
>
> Please fix it to use pr_err. If it's intended for the end user, pr_err
> can also give a meaningful message and no stack trace (which is I
> assume only huge clutter in this case).

Thanks, I will submit a patch to address that.

Thanks,
Gao Xiang

[Dmitry Vyukov]

On Mon, 25 Oct 2021 at 02:17, Gao Xiang <hsia...@linux.alibaba.com> wrote:
>

> Hi,
>
> On Sat, Oct 23, 2021 at 07:25:20PM -0700, syzbot wrote:
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit: 60e8840126bd Add linux-next specific files for 20211018
> > git tree: linux-next
> > console output: https://syzkaller.appspot.com/x/log.txt?x=125932af300000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=4bd44cafcda7632e
> > dashboard link: https://syzkaller.appspot.com/bug?extid=d8aaffc3719597e8cfb4
> > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> >
> > Unfortunately, I don't have any reproducer for this issue yet.
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+d8aaff...@syzkaller.appspotmail.com
> >
> > erofs: (device loop4): z_erofs_lz4_decompress_mem: failed to decompress -4100 in[4096, 0] out[9000]
> > ------------[ cut here ]------------
> > WARNING: CPU: 1 PID: 9895 at fs/erofs/decompressor.c:230 z_erofs_lz4_decompress_mem fs/erofs/decompressor.c:227 [inline]
> > WARNING: CPU: 1 PID: 9895 at fs/erofs/decompressor.c:230 z_erofs_lz4_decompress+0x841/0x1400 fs/erofs/decompressor.c:289
>
> If you fuzz compressed data, that is what you'd expect..

Hi Gao,

If you mean this is not a kernel bug, then the code should not use WARN.
WARN if for kernel bugs and is recognized as such by all testing
systems and humans.

Please fix it to use pr_err. If it's intended for the end user, pr_err
can also give a meaningful message and no stack trace (which is I
assume only huge clutter in this case).

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 9ae1fbdeabd3 Add linux-next specific files for 20211025
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1300f7c4b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=aeb17e42bc109064

dashboard link: https://syzkaller.appspot.com/bug?extid=d8aaffc3719597e8cfb4
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=103ac24ab00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=177194e2b00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d8aaff...@syzkaller.appspotmail.com

erofs: (device loop0): z_erofs_lz4_decompress_mem: failed to decompress -4099 in[4096, 0] out[9000]
------------[ cut here ]------------
WARNING: CPU: 1 PID: 45 at fs/erofs/decompressor.c:230 z_erofs_lz4_decompress_mem fs/erofs/decompressor.c:227 [inline]
WARNING: CPU: 1 PID: 45 at fs/erofs/decompressor.c:230 z_erofs_lz4_decompress+0x841/0x1400 fs/erofs/decompressor.c:289
Modules linked in:
CPU: 1 PID: 45 Comm: kworker/u5:0 Not tainted 5.15.0-rc6-next-20211025-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: erofs_unzipd z_erofs_decompressqueue_work
RIP: 0010:z_erofs_lz4_decompress_mem fs/erofs/decompressor.c:230 [inline]
RIP: 0010:z_erofs_lz4_decompress+0x841/0x1400 fs/erofs/decompressor.c:289

Code: e9 03 80 3c 11 00 0f 85 8c 0a 00 00 41 56 48 8b 7d 00 45 89 e9 89 d9 48 c7 c2 00 f0 fb 89 48 c7 c6 20 f2 fb 89 e8 fc 4a 85 05 <0f> 0b 48 b8 00 00 00 00 00 fc ff df 48 8b 4c 24 08 5f 48 89 ca 48
RSP: 0018:ffffc9000115f710 EFLAGS: 00010282
RAX: 0000000000000000 RBX: ffffffffffffeffd RCX: 0000000000000000
RDX: ffff88801599d7c0 RSI: ffffffff815f17d8 RDI: fffff5200022bed2
RBP: ffffc9000115f850 R08: 0000000000000063 R09: 0000000000000000
R10: ffffffff815eb5ae R11: 0000000000000000 R12: 0000000000000000

R13: 0000000000000000 R14: 0000000000002328 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 000056199e7f9008 CR3: 000000007f362000 CR4: 00000000003506e0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>

z_erofs_decompress_pcluster.isra.0+0x1301/0x2250 fs/erofs/zdata.c:975
z_erofs_decompress_queue fs/erofs/zdata.c:1053 [inline]
z_erofs_decompressqueue_work+0xe1/0x170 fs/erofs/zdata.c:1064
process_one_work+0x9b2/0x1690 kernel/workqueue.c:2298
worker_thread+0x658/0x11f0 kernel/workqueue.c:2445