Re: [PATCH 5/5] io_uring: fix use after free

Pavel Begunkov
2020-07-03T19:50:40Z

On 03/07/2020 05:39, Jann Horn wrote:
> On Mon, Jun 29, 2020 at 10:44 PM Pavel Begunkov <asml.silence@gmail.com> wrote:
>> After __io_free_req() put a ctx ref, it should assumed that the ctx may
>> already be gone. However, it can be accessed to put back fallback req.
>> Free req first and then put a req.
>
> Please stick "Fixes" tags on bug fixes to make it easy to see when the
> fixed bug was introduced (especially for ones that fix severe issues
> like UAFs). From a cursory glance, it kinda seems like this one
> _might_ have been introduced in 2b85edfc0c90ef, which would mean that
> it landed in 5.6? But I can't really tell for sure without investing
> more time; you probably know that better.

It was there from the beginning,
0ddf92e848ab7 ("io_uring: provide fallback request for OOM situations")

>
> And if this actually does affect existing releases, please also stick
> a "Cc: stable@vger.kernel.org" tag on it so that the fix can be
> shipped to users of those releases.

As mentioned in the cover letter, it's pretty unlikely to ever happen.
No one seems to have seen it since its introduction in November 2019.
And as the patch can't be backported automatically, not sure it's worth
the effort. Am I misjudging here?

--
Pavel Begunkov