Bug 1851472 (CVE-2020-15567)

Summary: CVE-2020-15567 xen: non-atomic modification of live EPT PTE leads to DoS (XSA-328)
Product: [Other] Security Response Reporter: Dhananjay Arunesh <darunesh>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED NOTABUG QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: acaringi, ailan, bhu, bmasney, brdeoliv, dhoward, drjones, dvlasenk, fhrbata, gsuckevi, hkrzesin, imammedo, jforbes, jshortt, jstancek, knoel, m.a.young, mrezanin, nmurray, pbonzini, ptalbert, robinlee.sysu, rvrbovsk, security-response-team, vkuznets, xen-maint
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A race condition flaw was found in Xen in the mapping of guest EPT tables (nested paging). Under certain circumstances, a guest user might be able to cause Denial of Service (DoS), data corruption, or privilege escalation.
Story Points: ---
Clone Of: Environment:
Last Closed: 2020-07-07 19:29:58 UTC Type: ---
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 1854464    
Bug Blocks: 1851487    

Description Dhananjay Arunesh 2020-06-26 16:27:46 UTC
A vulnerability was found in xen, where a guest administrator or perhaps even unprivileged guest user might be able to cause denial of service, data corruption, or privilege escalation.

Comment 1 Mauro Matteo Cascella 2020-07-01 15:48:24 UTC
Acknowledgments:

Name: the Xen project

Comment 2 Mauro Matteo Cascella 2020-07-01 17:34:12 UTC
This flaw affects systems using Intel CPUs with support for nested virtualization, and only HVM and PVH guests can exploit the vulnerability (PV guests are not affected). Note that, as of Xen 4.4, nested HVM on Intel CPUs is considered "tech preview" and not recommended to be used in a production environment [1].

[1] https://wiki.xenproject.org/wiki/Nested_Virtualization_in_Xen

Comment 3 Mauro Matteo Cascella 2020-07-06 14:15:54 UTC
Statement:

This flaw affects systems using Intel CPUs with support for nested paging (HAP). Only HVM and PVH guests can exploit the vulnerability, PV guests are not affected by this flaw.

Comment 4 Mauro Matteo Cascella 2020-07-06 14:15:57 UTC
Mitigation:

Switching to shadow paging (e.g. using the `hap=0` xl domain domain configuration file parameter) will avoid exposing the vulnerability to those guests.

Comment 5 Guilherme de Almeida Suckevicz 2020-07-06 18:47:27 UTC
*** Bug 1854208 has been marked as a duplicate of this bug. ***

Comment 6 Mauro Matteo Cascella 2020-07-07 14:02:17 UTC
External References:

https://xenbits.xen.org/xsa/advisory-328.html

Comment 7 Mauro Matteo Cascella 2020-07-07 14:03:13 UTC
Created xen tracking bugs for this issue:

Affects: fedora-all [bug 1854464]

Comment 8 Product Security DevOps Team 2020-07-07 19:29:58 UTC
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s):

https://access.redhat.com/security/cve/cve-2020-15567