Bug 2025046 (CVE-2021-28710)

Summary:	CVE-2021-28710 xen: Certain VT-d IOMMUs may not work in shared page table mode
Product:	[Other] Security Response	Reporter:	Pedro Sampaio <psampaio>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED UPSTREAM	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	jforbes, m.a.young
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
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Last Closed:	2021-11-19 19:19:28 UTC	Type:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	2025047
Bug Blocks:

Description Pedro Sampaio 2021-11-19 18:51:27 UTC

For efficiency reasons, address translation control structures (page
tables) may (and, on suitable hardware, by default will) be shared
between CPUs, for second-level translation (EPT), and IOMMUs.  These
page tables are presently set up to always be 4 levels deep.  However,
an IOMMU may require the use of just 3 page table levels.  In such a
configuration the lop level table needs to be stripped before
inserting the root table's address into the hardware pagetable base
register.  When sharing page tables, Xen erroneously skipped this
stripping.  Consequently, the guest is able to write to leaf page
table entries.

References:

https://xenbits.xen.org/xsa/advisory-390.html

Comment 1 Pedro Sampaio 2021-11-19 18:51:39 UTC

Created xen tracking bugs for this issue:

Affects: fedora-all [bug 2025047]

Comment 2 Product Security DevOps Team 2021-11-19 19:19:26 UTC

This CVE Bugzilla entry is for community support informational purposes only as it does not affect a package in a commercially supported Red Hat product. Refer to the dependent bugs for status of those individual community products.