linux-kernel - Re: [syzbot] Monthly io-uring report

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Message-ID: <75a684d6-8aca-8438-d303-f900b4db865d@kernel.dk>
Date:   Mon, 27 Mar 2023 13:20:53 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Aleksandr Nogikh <nogikh@...gle.com>
Cc:     syzbot <syzbot+lista29bb0eabb2ddbae6f4a@...kaller.appspotmail.com>,
        io-uring@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] Monthly io-uring report

On 3/27/23 1:12?PM, Aleksandr Nogikh wrote:
> On Mon, Mar 27, 2023 at 8:23?PM Jens Axboe <axboe@...nel.dk> wrote:
>>
>> On 3/27/23 5:01?AM, syzbot wrote:
>>> 1873    Yes   WARNING in split_huge_page_to_list (2)
>>>               https://syzkaller.appspot.com/bug?extid=07a218429c8d19b1fb25
>>> 38      Yes   KASAN: use-after-free Read in nfc_llcp_find_local
>>>               https://syzkaller.appspot.com/bug?extid=e7ac69e6a5d806180b40
>>
>> These two are not io_uring. Particularly for the latter, I think syzbot
>> has a tendency to guess it's io_uring if any kind of task_work is
>> involved. That means anything off fput ends up in that bucket. Can we
>> get that improved please?
> 
> Sure, I'll update the rules and rerun the subsystem recognition.
> 
> Currently syzbot sets io_uring if at least one is true
> a) The crash stack trace points to the io_uring sources (according to
> MAINTAINERS)
> b) At least one reproducer has the syz_io_uring_setup call (that's a
> helper function that's part of syzkaller).
> 
> In general syzbot tries to minimize the reproducer, but unfortunately
> sometimes there remain some calls, which are not necessary per se. It
> definitely tried to get rid of them, but the reproducer was just not
> working with those calls cut out. Maybe they were just somehow
> affecting the global state and in the execution log there didn't exist
> any other call candidates, which could have fulfilled the purpose just
> as well.
> 
> I can update b) to "all reproducers have syz_io_uring_setup". Then
> those two bugs won't match the criteria.
> If it doesn't suffice and there are still too many false positives, I
> can drop b) completely.

Whatever cuts down on the noise is good with me. Not sure how 38 above
got lumped in? Maybe someone else did syz_io_uring_setup at some point?

> By the way, should F: fs/io-wq.c also be added to the IO_URING's
> record in the MAINTAINERS file?

I think you're looking at a really old tree, none of the supported
stable trees even have any io_uring code in fs/ anymore. Maybe they need
a MAINTAINERS update though? But even 5.10-stable has io-wq included,
though it's pointing at the wrong path now...

-- 
Jens Axboe