Openwall GNU/*/Linux - a small security-enhanced Linux distro for servers
[<prev] [next>] [day] [month] [year] [list]
Date: Thu, 10 Oct 2013 12:22:40 +0000
From: Xen.org security team <security@....org>
To: xen-announce@...ts.xen.org, xen-devel@...ts.xen.org,
 xen-users@...ts.xen.org, oss-security@...ts.openwall.com
CC: Xen.org security team <security@....org>
Subject: Xen Security Advisory 67 (CVE-2013-4368) - Information leak
 through outs instruction emulation

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

             Xen Security Advisory CVE-2013-4368 / XSA-67
                              version 2

         Information leak through outs instruction emulation

UPDATES IN VERSION 2
====================

Public release.

ISSUE DESCRIPTION
=================

The emulation of the outs instruction for 64-bit PV guests uses an
uninitialized variable as the segment base for the source data if an FS: or
GS: segment override is used, and if the segment descriptor the respective
non-null selector in the corresponding selector register points to cannot be
read by the emulation code (this is possible if the segment register was
loaded before a more recent GDT or LDT update, i.e. the segment register
contains stale data).

A malicious guest might be able to get hold of contents of the hypervisor
stack, through the fault address passed to the page fault handler if the outs
raises such a fault (which is mostly under guest control).  Other methods for
indirectly deducing information also exist.

IMPACT
======

A malicious 64-bit PV guest might conceivably gain access to sensitive data
relating to other guests.

VULNERABLE SYSTEMS
==================

Xen 3.1.x and later are vulnerable.

Only 64-bit PV guests can take advantage of this vulnerability.

MITIGATION
==========

Running only HVM or 32-bit PV guests will avoid this issue.

CREDITS
=======

This issue was discovered by Coverity Scan and Matthew Daley.

RESOLUTION
==========

Applying the attached patch resolves this issue.

xsa67.patch             Xen 4.2.x, Xen 4.3.x, xen-unstable

$ sha256sum xsa67*.patch
7de3ac9baa6cd9fead46e68912dfa0189e900095317645d0e33d85346fc8a028  xsa67.patch
$
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.12 (GNU/Linux)

iQEcBAEBAgAGBQJSVpv2AAoJEIP+FMlX6CvZBl4H/RAC7wtn0iA5AGj8197NJC0q
kZDOT0h9QAgecWtYLaZ249MIWeFRGDLjw5IQKxQG+0c/BJyTZzyvLqbfAA/rjjX2
FVSi9+6qtr23WTIgoMKDuSvO/MaC55Y2hkZ/9+j8c+jUD9OyOdbGpjYMF+n3ARB7
GYJkDomxTD/5N8D25wCciaR3fKepM4eaBayXrjIVP2S/k6aQ8QQCjSLP+ito8EG8
RD+MaRlYyBYrO3Q9hZdNju6AREKphpS0WEHqlChmql8Ij8+88ZFYXVHHmhw70G6D
1d6OSm1kFikmroWby9AD97qDwX+estTA4kwKnXYxmcrgyWvkE7O9/uVQJbGGNwg=
=thOF
-----END PGP SIGNATURE-----

Download attachment "xsa67.patch" of type "application/octet-stream" (1307 bytes)

Powered by blists - more mailing lists

Your e-mail address:

Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.