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Date: Mon, 25 Oct 2021 08:16:59 +0800
From: Gao Xiang <hsiangkao@linux.alibaba.com>
To: syzbot <syzbot+d8aaffc3719597e8cfb4@syzkaller.appspotmail.com>
Subject: Re: [syzbot] WARNING in z_erofs_lz4_decompress
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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+d8aaffc3719597e8cfb4@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

> 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>
> 
> 
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@googlegroups.com.
> 
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.