oss-security - Xen Security Advisory 35 (CVE-2013-0152) - Nested HVM exposes host to being driven out of memory by guest

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Message-Id: <E1TxcYd-0007H4-74@xenbits.xen.org>
Date: Tue, 22 Jan 2013 12:02:27 +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 35 (CVE-2013-0152) - Nested HVM exposes
 host to being driven out of memory by guest

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

	     Xen Security Advisory CVE-2013-0152 / XSA-35
                           version 3

       Nested HVM exposes host to being driven out of memory by guest

UPDATES IN VERSION 3
====================

Public release.

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

Guests are currently permitted to enable nested virtualization on
themselves. Missing error handling cleanup in the handling code makes
it possible for a guest, particularly a multi-vCPU one, to repeatedly
invoke this operation, thus causing a leak of - over time - unbounded
amounts of memory.

IMPACT
======

A malicious domain can mount a denial of service attack affecting the
whole system.

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

Only Xen 4.2 and Xen unstable are vulnerable. Xen 4.1 and earlier are
not vulnerable.

The vulnerability is only exposed by HVM guests.

MITIGATION
==========

Running only PV guests will avoid this vulnerability.

RESOLUTION
==========

Applying the appropriate attached patch resolves this issue.

To fix both XSA 34 and XSA 35, first apply xsa34-4.2.patch from XSA 34
and then *also* apply xsa35-4.2-with-xsa34.patch from this advisory.

To fix this issue without addressing XSA 34, use xsa35.patch.

$ sha256sum xsa35*.patch
8372322e986bc2210f0d35b4d35a029301bd28fc1dffb789dff1436eb2024723  xsa35-4.2-with-xsa34.patch
e69b01033b0fa4c3d175697566d2f0b161337e8d206654919937f77721dbf866  xsa35.patch
$
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Download attachment "xsa35-4.2-with-xsa34.patch" of type "application/octet-stream" (773 bytes)

Download attachment "xsa35.patch" of type "application/octet-stream" (919 bytes)

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