Bug 1304628 (CVE-2016-2271, xsa170)

Summary: CVE-2016-2271 xsa170 xen: guest user mode may crash guest with non-canonical RIP (XSA-170)
Product: [Other] Security Response Reporter: Martin Prpič <mprpic>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED WONTFIX QA Contact:
Severity: low Docs Contact:
Priority: low    
Version: unspecifiedCC: security-response-team
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2018-02-26 12:29:28 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Bug Depends On: 1309323    
Bug Blocks: 1304631    

Description Martin Prpič 2016-02-04 08:51:45 UTC
ISSUE DESCRIPTION
=================

VMX refuses attempts to enter a guest with an instruction pointer which doesn't satisfy certain requirements. In particular, the instruction pointer needs to be canonical when entering a guest currently in 64-bit mode. This is the case even if the VM entry information specifies an exception to be injected immediately (in which case the bad instruction pointer would possibly never get used for other than pushing onto the exception handler's stack). Provided the guest OS allows user mode to map the virtual memory space immediately below the canonical/non- canonical address boundary, a non-canonical instruction pointer can result even from normal user mode execution. VM entry failure, however, is fatal to the guest.

IMPACT
======

Malicious HVM guest user mode code may be able to crash the guest.

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

Only systems using Intel or Cyrix CPUs are affected. ARM and AMD systems are unaffected. Only HVM guests are affected.

MITIGATION
==========

Running only PV guests will avoid this vulnerability. Running HVM guests on only AMD hardware will also avoid this
vulnerability.


External References:

http://xenbits.xen.org/xsa/advisory-170.html

Acknowledgements:

Red Hat would like to thank the Xen project for reporting this issue.

Comment 1 Andrej Nemec 2016-02-17 13:23:02 UTC
Created xen tracking bugs for this issue:

Affects: fedora-all [bug 1309323]

Comment 2 Andrej Nemec 2016-02-17 13:23:17 UTC
Public via:

http://seclists.org/oss-sec/2016/q1/357

Comment 3 Fedora Update System 2016-02-26 19:23:34 UTC
xen-4.5.2-8.fc23 has been pushed to the Fedora 23 stable repository. If problems still persist, please make note of it in this bug report.

Comment 4 Fedora Update System 2016-03-06 23:18:36 UTC
xen-4.5.2-8.fc22 has been pushed to the Fedora 22 stable repository. If problems still persist, please make note of it in this bug report.