Bug 1891091 (CVE-2020-27671) - CVE-2020-27671 xen: undue deferral of IOMMU TLB flushes (XSA-346)
Summary: CVE-2020-27671 xen: undue deferral of IOMMU TLB flushes (XSA-346)
Keywords:
Status: CLOSED NOTABUG
Alias: CVE-2020-27671
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: 1891093
Blocks: 1891100
TreeView+ depends on / blocked
 
Reported: 2020-10-23 18:54 UTC by Guilherme de Almeida Suckevicz
Modified: 2021-02-16 19:01 UTC (History)
25 users (show)

Fixed In Version:
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A flaw was found to occur in the Xen optimization to coalesce per-page IOMMU TLB flushes. This flaw allows malicious x86 HVM and PVH guests to cause host data corruption and data leaks, resulting in a denial of service (DoS) or potential privilege escalation. The highest threat from this vulnerability is to confidentiality and integrity as well as system availability.
Clone Of:
Environment:
Last Closed: 2020-11-02 20:21:26 UTC

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Description Guilherme de Almeida Suckevicz 2020-10-23 18:54:32 UTC 
An issue was discovered in all Xen versions from 4.2 onwards, allowing x86 HVM and PVH guest OS users to cause a denial of service (data corruption), cause a data leak, or possibly gain privileges because coalescing of per-page IOMMU TLB flushes is mishandled.
Comment 1 Guilherme de Almeida Suckevicz 2020-10-23 18:54:50 UTC 
Created xen tracking bugs for this issue:

Affects: fedora-all [bug 1891093]
Comment 2 Mauro Matteo Cascella 2020-11-02 14:38:36 UTC 
Acknowledgments:

Name: the Xen project
Comment 3 Mauro Matteo Cascella 2020-11-02 14:39:27 UTC 
External References:

https://xenbits.xen.org/xsa/advisory-346.html
Comment 4 Mauro Matteo Cascella 2020-11-02 15:06:43 UTC 
Upstream fix:
https://xenbits.xen.org/xsa/xsa346/xsa346-1.patch
https://xenbits.xen.org/xsa/xsa346/xsa346-2.patch
Comment 5 Product Security DevOps Team 2020-11-02 20:21:26 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-2020-27671
Comment 6 Mauro Matteo Cascella 2020-11-03 13:06:29 UTC 
Statement:

All Xen versions from 4.2 onwards are vulnerable. Red Hat Enterprise Linux 5 is not affected by this flaw, as it shipped with an older version of Xen.
Comment 8 RaTasha Tillery-Smith 2020-12-07 18:20:24 UTC 
Mitigation:

Avoid passing through physical devices to untrusted guests. Refer to the XSA-346 advisory for additional information.
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