Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Thu, 18 Jan 2018 23:49:24 +0100
From:   Pavel Machek <pavel@ucw.cz>
To:     Avi Kivity <avi@scylladb.com>
Cc:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: Proposal: CAP_PAYLOAD to reduce Meltdown and Spectre mitigation
 costs
Message-ID: <20180118224924.GF17196@amd>
References: <a5398c4e-be02-0de6-5c76-c37320011eef@scylladb.com>
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha1;
        protocol="application/pgp-signature"; boundary="m1UC1K4AOz1Ywdkx"
Content-Disposition: inline
In-Reply-To: <a5398c4e-be02-0de6-5c76-c37320011eef@scylladb.com>
User-Agent: Mutt/1.5.23 (2014-03-12)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


--m1UC1K4AOz1Ywdkx
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

On Sat 2018-01-06 21:33:28, Avi Kivity wrote:
> Meltdown and Spectre mitigations focus on protecting the kernel from a
> hostile userspace. However, it's not a given that the kernel is the most
> important target in the system. It is common in server workloads that a
> single userspace application contains the valuable data on a system, and =
if
> it were hostile, the game would already be over, without the need to
> compromise the kernel.
>=20
>=20
> In these workloads, a single application performs most system calls, and =
so
> it pays the cost of protection, without benefiting from it directly (since
> it is the target, rather than the kernel).
>=20
>=20
> I propose to create a new capability, CAP_PAYLOAD, that allows the system
> administrator to designate an application as the main workload in that
> system. Other processes (like sshd or monitoring daemons) exist to support
> it, and so it makes sense to protect the rest of the system from their be=
ing
> compromised.

prctl(I_AM_PAYLOAD) may do the trick. CAP_PAYLOAD is bad idea.

prctl() should require some pretty heavy capabilities, similar to
iopl() / ioperm() syscalls on x86, maybe CAP_SYS_RAWIO. Maybe it can
depend on some other capability.

But merely having the capability should definitely not change system
behaviour.

									Pavel
--=20
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo=
g.html

--m1UC1K4AOz1Ywdkx
Content-Type: application/pgp-signature; name="signature.asc"
Content-Description: Digital signature

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1

iEYEARECAAYFAlphJHQACgkQMOfwapXb+vKFjACghBiwRI5ZSJsaI7NSiRIE4g+A
BoYAn1R1JpEWGwcjFJxbQVVWhTfJnyZN
=HhHH
-----END PGP SIGNATURE-----

--m1UC1K4AOz1Ywdkx--