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

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Date:   Tue, 31 May 2022 03:07:10 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     Hao Xu <haoxu.linux@...oud.com>,
        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 3:05 AM, Dmitry Vyukov wrote:
> On Tue, 31 May 2022 at 11:01, Jens Axboe <axboe@...nel.dk> wrote:
>>
>> On 5/31/22 3:00 AM, Hao Xu wrote:
>>> 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.
>>
>> Yeah that's what I did, just rebased it to get rid of it:
>>
>> https://git.kernel.dk/cgit/linux-block/commit/?h=io_uring-5.19&id=fcde59feb1affb6d56aecadc3868df4631480da5
> 
> If you are rebasing it, please add the following tag so that the bug
> is closed later:
> 
> Tested-by: syzbot+b6c9b65b6753d333d833@...kaller.appspotmail.com

Sorry, missed that, would be a bit confusing? 5.20 branch is rebased
on top of that too. Can we just do:

#syz fix: io_uring: add io_op_defs 'def' pointer in req init and issue

?

-- 
Jens Axboe