From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marek =?utf-8?Q?Marczykowski-G=C3=B3recki?= Subject: Re: Xen Security Advisory 155 (CVE-2015-8550) - paravirtualized drivers incautious about shared memory Date: Mon, 4 Jan 2016 17:56:28 +0100 Message-ID: <20160104165628.GU4892@mail-itl> References: <20160104130632.GF4892@mail-itl> <568A9C48.6000904@citrix.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============4594689096316985402==" Return-path: In-Reply-To: <568A9C48.6000904@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: David Vrabel Cc: security@xen.org, "xen-devel@lists.xen.org" , Stefano Stabellini , Eric Shelton List-Id: xen-devel@lists.xenproject.org --===============4594689096316985402== Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="f61P+fpdnY2FZS1u" Content-Disposition: inline --f61P+fpdnY2FZS1u Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Jan 04, 2016 at 04:22:32PM +0000, David Vrabel wrote: > On 04/01/16 13:06, Marek Marczykowski-G=C3=B3recki wrote: > > On Tue, Dec 22, 2015 at 10:06:25AM -0500, Eric Shelton wrote: > >> The XSA mentions that "PV frontend patches will be developed and > >> released (publicly) after the embargo date." Has anything been done > >> towards this that should also be incorporated into MiniOS? On a > >> system utilizing a "driver domain," where a backend is running on a > >> domain that is considered unprivileged and untrusted (such as the > >> example described in http://wiki.xenproject.org/wiki/Driver_Domain), > >> it seems XSA-155-style double fetch vulnerabilities in the frontends > >> are also a potential security concern, and should be eliminated. > >> However, perhaps that does not include pcifront, since pciback would > >> always be running in dom0. > >=20 > > And BTW the same applies to Linux frontends, for which also I haven't s= een > > any public development. In attachment my email to > > xen-security-issues-discuss list (sent during embargo), with patches > > attached there. I haven't got any response. >=20 > There are no similar security concerns with frontends since they trust > the backend. >=20 > I note that you say: >=20 > "But in some cases (namely: if driver domains are in use), frontends > may be more trusted/privileged than backends." >=20 > But this cannot be the case since the backend can always trivially DoS > the frontend by (for example) not unmapping grant references when > required by the protocol. DoS is one thing, code execution is another. --=20 Best Regards, Marek Marczykowski-G=C3=B3recki Invisible Things Lab A: Because it messes up the order in which people normally read text. Q: Why is top-posting such a bad thing? --f61P+fpdnY2FZS1u Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQEcBAEBCAAGBQJWiqQ8AAoJENuP0xzK19csdJ8H/2q8RX/wMpgfhBMk7u2JFmh2 vv6S1NeWaPb3aVPSwlcVJu5uwfYqxD2fuZkO7GXtVOfdC0nWa72p0Ko43ccV9j66 QJ1NArKH4SVET7Z+Joss6GK2kRhWmaIG8LuHkf9sbpLAVTn9oHdhW39e82VmQj4L cjL2BcLYtk1OieqW1CpzsCMGDvejj7WQNIGOJepFNKjG865Z8F8jJylP3w50EMVC 17z3a7z7ehPzmWNmWXjvGEGnwWSDBgATazPPUb+ntH/MNg01xqtCfhQkchd6B3e1 AySLuDphO+kJq1osvmmOYltrl4zrIv8SVWxl+7WT2uk8NZWm405PPPXKcdKF+Hw= =KPO4 -----END PGP SIGNATURE----- --f61P+fpdnY2FZS1u-- --===============4594689096316985402== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel --===============4594689096316985402==--