linux-kernel - Re: [syzbot] UBSAN: array-index-out-of-bounds in io_submit

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Date:   Tue, 31 May 2022 17:00:23 +0800
From:   Hao Xu <haoxu.linux@...oud.com>
To:     Jens Axboe <axboe@...nel.dk>,
        syzbot <syzbot+b6c9b65b6753d333d833@...kaller.appspotmail.com>,
        asml.silence@...il.com, io-uring@...r.kernel.org,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] UBSAN: array-index-out-of-bounds in io_submit_sqes

On 5/31/22 16:45, Jens Axboe wrote:
> On 5/31/22 1:55 AM, syzbot wrote:
>> Hello,
>>
>> syzbot found the following issue on:
>>
>> HEAD commit:    3b46e4e44180 Add linux-next specific files for 20220531
>> git tree:       linux-next
>> console output: https://syzkaller.appspot.com/x/log.txt?x=16e151f5f00000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=ccb8d66fc9489ef
>> dashboard link: https://syzkaller.appspot.com/bug?extid=b6c9b65b6753d333d833
>> 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+b6c9b65b6753d333d833@...kaller.appspotmail.com
>>
>> ================================================================================
>> ================================================================================
>> UBSAN: array-index-out-of-bounds in fs/io_uring.c:8860:19
>> index 75 is out of range for type 'io_op_def [47]'
> 
> 'def' is just set here, it's not actually used after 'opcode' has been
> verified.
> 

Maybe we can move it to be below the opcode check to comfort UBSAN.