Bug 1296539 (CVE-2016-1570, xsa167)

Summary: CVE-2016-1570 xen: PV superpage functionality missing sanity checks
Product: [Other] Security Response Reporter: Adam Mariš <amaris>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED NOTABUG QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: ailan, drjones, imammedo, knoel, mrezanin, osoukup, pbonzini, rkrcmar, security-response-team, vkuznets, xen-maint
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 11:52:02 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: 1300345    
Bug Blocks: 1296546    
Attachments:
Description Flags
Patch for xen-unstable, Xen 4.6.x, Xen 4.5.x
none
Patch for Xen 4.3.x, 4.4.x
none
Xen 4.6.x none

Description Adam Mariš 2016-01-07 13:24:46 UTC 
It was found that PV superpage functionality lacks certain validity checks on data being passed to the hypervisor by guests. This is the case for the page identifier (MFN) passed to MMUEXT_MARK_SUPER and MMUEXT_UNMARK_SUPER sub-ops of the HYPERVISOR_mmuext_op hypercall as well as for various forms of page table updates.

Use of the feature, which is disabled by default, may have unknown effects, ranging from information leaks through Denial of Service to privilege escalation.

Only systems which enable the PV superpage feature are affected. That is, only systems with an `allowsuperpage' setting on the hypervisor command line. Note that in Xen 4.0.x and 3.4.x the option is named `allowhugepage'. Xen versions 3.4.0, 3.4.1, and from 4.1 onwards are affected. Only x86 systems are affected. Only PV guests can exploit the vulnerability.

Running only HVM guests will avoid this issue. Not enabling PV superpage support (by omitting the `allowsuperpage' or `allowhugepage' hypervisor command line options) will avoid exposing the issue.
Comment 1 Adam Mariš 2016-01-07 13:27:23 UTC 
Created attachment 1112460 [details]
Patch for xen-unstable, Xen 4.6.x, Xen 4.5.x
Comment 2 Adam Mariš 2016-01-07 13:28:06 UTC 
Created attachment 1112462 [details]
Patch for Xen 4.3.x, 4.4.x
Comment 3 Adam Mariš 2016-01-07 13:28:54 UTC 
Created attachment 1112463 [details]
Xen 4.6.x
Comment 5 Andrej Nemec 2016-01-20 14:15:38 UTC 
Created xen tracking bugs for this issue:

Affects: fedora-all [bug 1300345]
Comment 6 Andrej Nemec 2016-01-20 14:16:28 UTC 
Public via:

http://seclists.org/oss-sec/2016/q1/155
Comment 7 Fedora Update System 2016-01-28 18:24:36 UTC 
xen-4.5.2-7.fc23 has been pushed to the Fedora 23 stable repository. If problems still persist, please make note of it in this bug report.
Comment 8 Fedora Update System 2016-02-01 06:29:40 UTC 
xen-4.5.2-7.fc22 has been pushed to the Fedora 22 stable repository. If problems still persist, please make note of it in this bug report.