Bug 1012550 (CVE-2013-4368)

Summary: CVE-2013-4368 xen: information leak through outs instruction emulation (XSA-67)
Product: [Other] Security Response Reporter: Vincent Danen <vdanen>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED ERRATA QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: agordeev, anton, dhoward, drjones, imammedo, jkurik, lwang, mrezanin, pbonzini, plougher, pmatouse, prasad, rkrcmar, rvrbovsk, security-response-team
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard: impact=moderate,public=20131010,reported=20130926,source=upstream,cvss2=2.3/AV:A/AC:M/Au:S/C:P/I:N/A:N,rhel-5/kernel-xen=affected,fedora-all/xen=affected
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2014-06-10 06:00:07 EDT Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---
Bug Depends On: 1012958, 1012959, 1017843    
Bug Blocks: 1012558    

Description Vincent Danen 2013-09-26 11:52:00 EDT
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.

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


Red Hat would like to thank the Xen project for reporting this issue.
Comment 6 Vincent Danen 2013-10-10 12:19:57 EDT
External References:

Comment 7 Vincent Danen 2013-10-10 12:22:34 EDT
Created xen tracking bugs for this issue:

Affects: fedora-all [bug 1017843]
Comment 8 errata-xmlrpc 2013-10-22 13:31:21 EDT
This issue has been addressed in following products:

  Red Hat Enterprise Linux 5

Via RHSA-2013:1449 https://rhn.redhat.com/errata/RHSA-2013-1449.html
Comment 9 Fedora Update System 2013-10-22 23:34:09 EDT
xen-4.2.3-4.fc18 has been pushed to the Fedora 18 stable repository.  If problems still persist, please make note of it in this bug report.
Comment 10 Fedora Update System 2013-10-22 23:41:03 EDT
xen-4.2.3-4.fc19 has been pushed to the Fedora 19 stable repository.  If problems still persist, please make note of it in this bug report.