Bug 1891096 (CVE-2020-27672) - CVE-2020-27672 xen: x86: race condition in Xen mapping code (XSA-345)
Summary: CVE-2020-27672 xen: x86: race condition in Xen mapping code (XSA-345)
Keywords:
Status: CLOSED NOTABUG
Alias: CVE-2020-27672
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 1891097
Blocks: 1891100
TreeView+ depends on / blocked
 
Reported: 2020-10-23 19:00 UTC by Guilherme de Almeida Suckevicz
Modified: 2021-02-16 19:01 UTC (History)
25 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
A race condition flaw was found in the Xen code responsible for handling the updating of the hypervisor's own page tables. This flaw allows a malicious guest to cause a denial of service, host data corruption, or potential privilege escalation. The highest threat from this vulnerability is to confidentiality, integrity as well as system availability.
Clone Of:
Environment:
Last Closed: 2020-11-02 20:21:30 UTC
Embargoed:

Attachments (Terms of Use)

Description Guilherme de Almeida Suckevicz 2020-10-23 19:00:15 UTC 
An issue was discovered in versions of Xen from at least 3.2 onward, allowing x86 guest OS users to cause a host OS denial of service, achieve data corruption, or possibly gain privileges by exploiting a race condition that leads to a use-after-free involving 2MiB and 1GiB superpages.
Comment 1 Guilherme de Almeida Suckevicz 2020-10-23 19:00:37 UTC 
Created xen tracking bugs for this issue:

Affects: fedora-all [bug 1891097]
Comment 2 Mauro Matteo Cascella 2020-11-02 14:38:25 UTC 
Acknowledgments:

Name: the Xen project
Comment 3 Mauro Matteo Cascella 2020-11-02 14:39:46 UTC 
External References:

https://xenbits.xen.org/xsa/advisory-345.html
Comment 4 Mauro Matteo Cascella 2020-11-02 15:13:58 UTC 
Upstream fix:
https://xenbits.xen.org/xsa/xsa345/0001-x86-mm-Refactor-map_pages_to_xen-to-have-only-a-sing.patch
https://xenbits.xen.org/xsa/xsa345/0002-x86-mm-Refactor-modify_xen_mappings-to-have-one-exit.patch
https://xenbits.xen.org/xsa/xsa345/0003-x86-mm-Prevent-some-races-in-hypervisor-mapping-upda.patch
Comment 5 Product Security DevOps Team 2020-11-02 20:21:30 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-2020-27672
Comment 6 Mauro Matteo Cascella 2020-11-03 13:13:41 UTC 
Statement:

All Xen versions from 3.2 onwards are vulnerable. Red Hat Enterprise Linux 5 is not affected by this flaw, as it shipped with an older version of Xen.
Comment 7 Mauro Matteo Cascella 2020-11-03 13:13:44 UTC 
Mitigation:

Running all guests in HVM or PVH mode, in each case with HAP enabled, will prevent those guests from exploiting the vulnerability.
Note You need to log in before you can comment on or make changes to this bug.