Bug 2425137 (CVE-2023-54081)

Summary:	CVE-2023-54081 kernel: Linux kernel: Denial of Service in Xen grant table reclaim via memory leak
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	rhel-process-autobot, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in the Linux kernel's Xen grant table reclaim mechanism. A remote attacker, by controlling a remote domain in a Xen environment, could exploit this vulnerability. By continuously holding grant references, the attacker can cause the deferred list in the grant table to grow excessively. This leads to a massive memory leak, ultimately resulting in a Denial of Service (DoS) as the guest virtual machine (VM) freezes due to memory exhaustion.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2025-12-24 14:05:41 UTC

In the Linux kernel, the following vulnerability has been resolved:

xen: speed up grant-table reclaim

When a grant entry is still in use by the remote domain, Linux must put
it on a deferred list.  Normally, this list is very short, because
the PV network and block protocols expect the backend to unmap the grant
first.  However, Qubes OS's GUI protocol is subject to the constraints
of the X Window System, and as such winds up with the frontend unmapping
the window first.  As a result, the list can grow very large, resulting
in a massive memory leak and eventual VM freeze.

To partially solve this problem, make the number of entries that the VM
will attempt to free at each iteration tunable.  The default is still
10, but it can be overridden via a module parameter.

This is Cc: stable because (when combined with appropriate userspace
changes) it fixes a severe performance and stability problem for Qubes
OS users.

Comment 1 Alexander B 2025-12-24 23:47:49 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025122403-CVE-2023-54081-3fc3@gregkh/T