[Xen-announce] Xen Security Advisory 30 (CVE-2012-5514) - Broken error handling in guest_physmap_mark_populate_on_demand()

[Xen.org security team <security@xxxxxxx>]

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             Xen Security Advisory CVE-2012-5514 / XSA-30
                              version 4

    Broken error handling in guest_physmap_mark_populate_on_demand()

UPDATES IN VERSION 4
====================

Public release.

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

guest_physmap_mark_populate_on_demand(), before carrying out its actual
operation, checks that the subject GFNs are not in use. If that check fails,
the code prints a message and bypasses the gfn_unlock() matching the
gfn_lock() carried out before entering the loop.

Further, the function is exposed to the use of guests on their own
behalf.  While we believe that this does not cause any further issues,
we have not conducted a thorough enough review to be sure.  Rather, it
should be exposed only to privileged domains.

IMPACT
======

A malicious guest administrator can cause Xen to hang.

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

All Xen version from 3.4 on are 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.

xsa30-4.1.patch             Xen 4.1.x
xsa30-4.2.patch             Xen 4.2.x
xsa30-4.unstable.patch      xen-unstable

$ sha256sum xsa30*.patch
586adda04271e91e42f42bb53636e2aa6fc7379e2c2c4b825e7ec6e34350669e  
xsa30-4.1.patch
c410bffb90a551be30fde5ec4593c361b69e9c261878255fdb4f8447e7177418  
xsa30-4.2.patch
2270eed8b89e4e28c4c79e5a284203632a7189474d6f0a6152d6cf56b287497b  
xsa30-unstable.patch
$
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Attachment: xsa30-4.1.patch
Description: Binary data

Attachment: xsa30-4.2.patch
Description: Binary data

Attachment: xsa30-unstable.patch
Description: Binary data

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