Bug 2034940 (CVE-2021-28711, CVE-2021-28712, CVE-2021-28713, XSA-391)

Summary:	CVE-2021-28711 CVE-2021-28712 CVE-2021-28713 xen: rogue backends can cause DoS of guests via high frequency events
Product:	[Other] Security Response	Reporter:	Guilherme de Almeida Suckevicz <gsuckevi>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED UPSTREAM	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	acaringi, bdettelb, bhu, brdeoliv, chwhite, crwood, dhoward, dvlasenk, fhrbata, fpacheco, hkrzesin, jarod, jburrell, jfaracco, jforbes, jlelli, jshortt, jstancek, kcarcia, kernel-mgr, lgoncalv, lzampier, m.a.young, nmurray, ptalbert, qzhao, rvrbovsk, scweaver, vkumar, walters, williams
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:	Linux kernel 5.16-rc7	Doc Type:	If docs needed, set a value
Doc Text:	A denial of service flaw for virtual machine guests in the Linux kernel's Xen hypervisor subsystem was found in the way users call some interrupts with high frequency from one of the guests. A local user could use this flaw to starve the resources resulting in a denial of service.	Story Points:	---
Clone Of:		Environment:
Last Closed:	2021-12-22 15:19:57 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:	2034941, 2036918, 2036919, 2036921, 2037393, 2037394
Bug Blocks:	2034965

Description Guilherme de Almeida Suckevicz 2021-12-22 14:29:08 UTC

Xen offers the ability to run PV backends in regular unprivileged guests, typically referred to as "driver domains". Running PV backends in driver domains has one primary security advantage: if a driver domain gets compromised, it doesn't have the privileges to take over the system.

However, a malicious driver domain could try to attack other guests via sending events at a high frequency leading to a Denial of Service in the guest due to trying to service interrupts for elongated amounts of time.

There are three affected backends:
 * blkfront          patch 1, CVE-2021-28711
 * netfront          patch 2, CVE-2021-28712
 * hvc_xen (console) patch 3, CVE-2021-28713

Reference:
https://xenbits.xen.org/xsa/advisory-391.html

Comment 1 Guilherme de Almeida Suckevicz 2021-12-22 14:29:20 UTC

Created xen tracking bugs for this issue:

Affects: fedora-all [bug 2034941]

Comment 2 Product Security DevOps Team 2021-12-22 15:19:55 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.