Re: CVE-2023-52656: io_uring: drop any code related to SCM_RIGHTS

[Jens Axboe]

On 5/25/24 9:09 AM, Eduardo' Vela" <Nava> wrote:
> On Sat, 25 May 2024, 09:15 Greg Kroah-Hartman, <gregkh@xxxxxxxxxxxxxxxxxxx <mailto:gregkh@xxxxxxxxxxxxxxxxxxx>> wrote:
> 
>     On Fri, May 24, 2024 at 10:57:07AM -0600, Jens Axboe wrote:
>     > On 5/24/24 10:45 AM, Gabriel Krisman Bertazi wrote:
>     > > Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx <mailto:gregkh@xxxxxxxxxxxxxxxxxxx>> writes:
>     > >
>     > >> Description
>     > >> ===========
>     > >>
>     > >> In the Linux kernel, the following vulnerability has been resolved:
>     > >>
>     > >> io_uring: drop any code related to SCM_RIGHTS
>     > >>
>     > >> This is dead code after we dropped support for passing io_uring fds
>     > >> over SCM_RIGHTS, get rid of it.
>     > >>
>     > >> The Linux kernel CVE team has assigned CVE-2023-52656 to this issue.
>     > >
>     > > Hello Greg,
>     > >
>     > > [+Jens in Cc]
>     > >
>     > > This is stable material, but doesn't deserve CVE status.  There is
>     > > nothing exploitable that is fixed here. Instead, this commit is dropping
>     > > unreachable code after the removal of a feature, following another CVE
>     > > report.  Doing the clean up in the original patch would have made the
>     > > real security fix harder to review.
>     > >
>     > > The real issue was reported as CVE-2023-52654 and handled by a different
>     > > commit.
>     >
>     > FWIW, the same is true for a number of other commits recently. They are
>     > nowhere near CVE material, it's just generic bug fixes.
> 
>     Ok, glad to revoke them if you do not think they are user triggerable
>     issues.  I'll go reject this one right now, thanks.
> 
> 
> Good day!
> 
> So, either I'm completely lost or CVE-2023-52656 shouldn't have been
> rejected. Forgive me for mudding the problem even more.
> 
> I think we need to unreject this CVE (CVE-2023-52656) or
> CVE-2023-52654 should be amended to include the dead code removal
> commit.. that said, that'll be weirder than just unrejecting this
> commit.
> 
> The reason is that the commit "io_uring/af_unix: disable sending
> io_uring over sockets" is not enough to fix the vulnerability in
> stable branches, because e.g. bcedd497b3b4a0be56f3adf7c7542720eced0792
> on 5.15 only fixes one path (io_sqe_file_register) to reach
> unix_inflight(), but it is still reachable via another path
> (io_sqe_fileS_register) which is only removed by
> d909d381c3152393421403be4b6435f17a2378b4 ("io_uring: drop any code
> related to SCM_RIGHTS").
> 
> Although that patch claims "it is dead code", this claim was only true
> on upstream, but not on stable branches (or at least on 5.15 where the
> vulnerability was proven to be reachable).
> 
> What a mess! ?

Ah right, yeah it was a mess because of the stable backports, it was not
for the upstream front. Agree Greg, let's just keep it because of the
stable side.

-- 
Jens Axboe