linux-kernel - Re: [PATCH v1 0/2] Add LSM access controls for io_uring

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Message-ID: <CAEjxPJ7xiqKAbfX2JhN2NBbWsdgEesE18RG4d81ELyee6bfOkQ@mail.gmail.com>
Date:   Thu, 10 Aug 2023 08:27:55 -0400
From:   Stephen Smalley <stephen.smalley.work@...il.com>
To:     Dmytro Maluka <dmy@...ihalf.com>
Cc:     Paul Moore <paul@...l-moore.com>,
        Jeffrey Vander Stoep <jeffv@...gle.com>,
        Gil Cukierman <cukie@...gle.com>, Jens Axboe <axboe@...nel.dk>,
        Pavel Begunkov <asml.silence@...il.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Eric Paris <eparis@...isplace.org>, kernel-team@...roid.com,
        linux-kernel@...r.kernel.org, io-uring@...r.kernel.org,
        linux-security-module@...r.kernel.org, selinux@...r.kernel.org,
        Joel Granados <j.granados@...sung.com>,
        Jeff Xu <jeffxu@...gle.com>,
        Takaya Saeki <takayas@...omium.org>,
        Tomasz Nowicki <tn@...ihalf.com>,
        Matteo Rizzo <matteorizzo@...gle.com>,
        Andres Freund <andres@...razel.de>
Subject: Re: [PATCH v1 0/2] Add LSM access controls for io_uring_setup

On Thu, Aug 10, 2023 at 5:08 AM Dmytro Maluka <dmy@...ihalf.com> wrote:
>
> On 8/9/23 19:28, Dmytro Maluka wrote:
> >   So one of the questions I'm wondering about is: if Android implemented
> >   preventing execution of any io_uring code by non-trusted processes
> >   (via seccomp or any other way), how much would it help to reduce the
> >   risk of attacks, compared to its current SELinux based solution?
>
> And why exactly I'm wondering about that: AFAICT, Android folks are
> concerned about the high likelihood of vulnerabilities in io_uring code
> just like we (ChromeOS folks) are, and that is the main reason why
> Android takes care of restricting io_uring usage in the first place.

I think if you audit the io_uring syscalls and find a code path that
is not already mediated by a LSM hook (potentially at an earlier point
during setup / fd creation) that accesses any shared resource or
performs a privileged action, we would be open to adding a LSM hook to
cover that code path. But you'd have to do the work to identify and
propose such cases.