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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Tue, 31 May 2022 11:05:18 +0200
Message-ID: <CACT4Y+aqriNp1F5CJofqaxNMM+-3cxNR2nY0tHEtb4YDqDuHtg@mail.gmail.com>
Subject: Re: [syzbot] UBSAN: array-index-out-of-bounds in io_submit_sqes
To:     Jens Axboe <axboe@kernel.dk>
Cc:     Hao Xu <haoxu.linux@icloud.com>,
        syzbot <syzbot+b6c9b65b6753d333d833@syzkaller.appspotmail.com>,
        asml.silence@gmail.com, io-uring@vger.kernel.org,
        linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com
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On Tue, 31 May 2022 at 11:01, Jens Axboe <axboe@kernel.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@syzkaller.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@syzkaller.appspotmail.com