Bug 1905668 (CVE-2020-29479)

Summary:	CVE-2020-29479 xen: oxenstored: permissions not checked on root node (XSA-353)
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:	jforbes, m.a.young, robinlee.sysu, security-response-team
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2020-12-15 22:20:04 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:	1908002
Bug Blocks:	1903644

Description Guilherme de Almeida Suckevicz 2020-12-08 19:18:42 UTC

In the Ocaml xenstored implementation, the internal representation of
the tree has special cases for the root node, because this node has no
parent.

Unfortunately, permissions were not checked for certain operations on
the root node.

Unprivileged guests can get and modify permissions, list, and delete
the root node.  Deleting the whole xenstore tree is a hostwide denial
of service.  Depending on the circumstances, the vulnerability can
also be leveraged into an ability to gain write access to any part of
xenstore.

Comment 1 Guilherme de Almeida Suckevicz 2020-12-15 16:28:21 UTC

External References:

https://www.openwall.com/lists/oss-security/2020/12/15/13

Comment 2 Guilherme de Almeida Suckevicz 2020-12-15 16:28:46 UTC

Created xen tracking bugs for this issue:

Affects: fedora-all [bug 1908002]

Comment 3 Product Security DevOps Team 2020-12-15 22:20:04 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.