linux-kernel - Re: [PATCH 1/1] Add a new sysctl to disable io

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 28 Jun 2023 13:36:04 +0200
From:   Ricardo Ribalda <ribalda@...omium.org>
To:     Matteo Rizzo <matteorizzo@...gle.com>
Cc:     Bart Van Assche <bvanassche@....org>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, io-uring@...r.kernel.org,
        jordyzomer@...gle.com, evn@...gle.com, poprdi@...gle.com,
        corbet@....net, axboe@...nel.dk, asml.silence@...il.com,
        akpm@...ux-foundation.org, keescook@...omium.org,
        rostedt@...dmis.org, dave.hansen@...ux.intel.com,
        chenhuacai@...nel.org, steve@....org, gpiccoli@...lia.com,
        ldufour@...ux.ibm.com
Subject: Re: [PATCH 1/1] Add a new sysctl to disable io_uring system-wide

Hi Matteo

On Tue, 27 Jun 2023 at 20:15, Matteo Rizzo <matteorizzo@...gle.com> wrote:
>
> On Tue, 27 Jun 2023 at 19:10, Bart Van Assche <bvanassche@....org> wrote:
> > I'm using fio + io_uring all the time on Android devices. I think we need a
> > better solution than disabling io_uring system-wide, e.g. a mechanism based
> > on SELinux that disables io_uring for apps and that keeps io_uring enabled
> > for processes started via 'adb root && adb shell ...'
>
> Android already uses seccomp to prevent untrusted applications from using
> io_uring. This patch is aimed at server/desktop environments where there is
> no easy way to set a system-wide seccomp policy and right now the only way
> to disable io_uring system-wide is to compile it out of the kernel entirely
> (not really feasible for e.g. a general-purpose distro).
>
> I thought about adding a capability check that lets privileged processes
> bypass this sysctl, but it wasn't clear to me which capability I should use.
> For userfaultfd the kernel uses CAP_SYS_PTRACE, but I wasn't sure that's
> the best choice here since io_uring has nothing to do with ptrace.
> If anyone has any suggestions please let me know. A LSM hook also sounds
> like an option but it would be more complicated to implement and use.

Have you considered that the new sysctl is "sticky like kexec_load_disabled.
When the user disables it there is no way to turn it back on until the
system is rebooted.

Best regards!

-- 
Ricardo Ribalda