Bug 1284919 (CVE-2015-8339, CVE-2015-8340, xsa159)

Summary: CVE-2015-8339 CVE-2015-8340 xen: XENMEM_exchange error handling may cause DoS to host
Product: [Other] Security Response Reporter: Adam Mariš <amaris>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED WONTFIX QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: ailan, drjones, imammedo, knoel, mrezanin, osoukup, pbonzini, rkrcmar, security-response-team, vkuznets, wmealing, xen-maint
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
A malicious guest administrator may be able to deny service by crashing the host or causing a deadlock by timing memory handling events between the guest and the host.
 Story Points: ---
Clone Of: Environment:
Last Closed: 2017-10-19 08:50:37 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 1289568    
Bug Blocks: 1284949    
Attachments:
Description Flags
xen-unstable, Xen 4.6.x, Xen 4.5.x, Xen 4.4.x, Xen 4.3.x none

Description Adam Mariš 2015-11-24 13:17:53 UTC 
CVE-2015-8339:
Error handling in the operation may involve handing back pages to the domain. This operation may fail when in parallel the domain gets torn down. So far this failure unconditionally resulted in the host being brought down due to an internal error being assumed.

CVE-2015-8340:
Furthermore error handling so far wrongly included the release of a lock. That lock, however, was either not acquired or already released on all paths leading to the error handling sequence.

A malicious guest administrator may be able to deny service by crashing the host or causing a deadlock.

All Xen versions from at least 3.2 onwards are vulnerable. Older versions have not been inspected.

The vulnerability can be avoided if the guest kernel is controlled by the host rather than guest administrator, provided that further steps are taken to prevent the guest administrator from loading code into the kernel (e.g. by disabling loadable modules etc) or from using other mechanisms which allow them to run code at kernel privilege. In Xen HVM, controlling the guest's kernel would involve locking down the bootloader.
Comment 1 Adam Mariš 2015-11-24 13:30:50 UTC 
Created attachment 1098198 [details]
xen-unstable, Xen 4.6.x, Xen 4.5.x, Xen 4.4.x, Xen 4.3.x
Comment 3 Martin Prpič 2015-12-08 12:28:46 UTC 
External References:

http://xenbits.xen.org/xsa/advisory-159.html
Comment 4 Martin Prpič 2015-12-08 12:42:33 UTC 
Created xen tracking bugs for this issue:

Affects: fedora-all [bug 1289568]
Comment 5 Fedora Update System 2015-12-17 07:26:51 UTC 
xen-4.5.2-5.fc23 has been pushed to the Fedora 23 stable repository. If problems still persist, please make note of it in this bug report.
Comment 6 Fedora Update System 2015-12-20 00:23:03 UTC 
xen-4.5.2-5.fc22 has been pushed to the Fedora 22 stable repository. If problems still persist, please make note of it in this bug report.
Comment 7 Wade Mealing 2017-10-19 08:29:12 UTC 
Statement:
Comment 8 Wade Mealing 2017-10-19 08:29:24 UTC 
Statement:

This issue does not affect the Linux kernel packages as shipped with Red Hat
Enterprise Linux 6, 7, MRG-2 and realtime kernels.

At this time, there is no plans to fix this issue, if you feel that this issue
is affecting your deployment and have an EUS subscription, please contact
support to have this issue correctly prioritized
Comment 11 Wade Mealing 2017-10-19 08:37:49 UTC 
Mitigation:

The vulnerability can be avoided if the guest kernel is controlled by the host rather than guest administrator, provided that further steps are taken to prevent the guest administrator from loading code into the kernel (e.g. by disabling loadable modules etc) or from using other mechanisms which allow them to run code at kernel privilege. In Xen HVM, controlling the guest's kernel would involve locking down the bootloader.