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ESB-2014.1045.2 - UPDATE [UNIX/Linux][Virtual] Xen: Access confidential data - Existing account

Date: 11 July 2014

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Click here for PGP verifiable version
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===========================================================================
             AUSCERT External Security Bulletin Redistribution

                              ESB-2014.1045.2
                       Xen Security Advisory XSA-101
                               11 July 2014

===========================================================================

        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           Xen
Publisher:         Xen
Operating System:  UNIX variants (UNIX, Linux, OSX)
                   Xen
Impact/Access:     Access Confidential Data -- Existing Account
Resolution:        Patch/Upgrade
CVE Names:         CVE-2014-4022  

Original Bulletin: 
   http://xenbits.xenproject.org/xsa/advisory-101.html

Revision History:  July 11 2014: Provide the CVE.
                   June 27 2014: Initial Release

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           Xen Security Advisory CVE-2014-4022 / XSA-101
                            version 3

            information leak via gnttab_setup_table on ARM

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

Provide the CVE.

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

When initialising an internal data structure on ARM platform Xen was
not correctly initialising the memory containing the list of a
domain's grant table pages. This list is returned by the
GNTTABOP_setup_table subhypercall, leading to an information leak.

IMPACT
======

Malicious guest administrators can obtain some of the memory contents
of other domains:

Up to 8*max_nr_grant_frames bytes of uninitialised memory can be
leaked to the calling domain. This memory may have been previously
used by either the hypervisor or other guests.

The default max_nr_grant_frames is 32, hence by default 256 bytes may
be leaked in this way.  However this can be overridden via the
"gnttab_max_nr_frames" hypervisor command line option.

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

Both 32- and 64-bit ARM systems are vulnerable from Xen 4.4 onward.

MITIGATION
==========

None.

CREDITS
=======

This issue was discovered by Julien Grall.

RESOLUTION
==========

Applying the attached patch resolves this issue.

xsa101.patch        xen-unstable, Xen 4.4.x

$ sha256sum xsa101*.patch
12ea475265a0804a3a42f620d7065a7408a5ae4b017c871847424c7247c204e9  xsa101.patch
$
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===========================================================================
Australian Computer Emergency Response Team
The University of Queensland
Brisbane
Qld 4072

Internet Email: auscert@auscert.org.au
Facsimile:      (07) 3365 7031
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                On call after hours for member emergencies only.
===========================================================================
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