Bug 2525481 (CVE-2026-80724)

Summary:	CVE-2026-80724 kernel: ptp: vmclock: prevent read-only mappings from becoming writable
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 vmclock component. This vulnerability allows a guest operating system, through a userspace process, to change a shared memory page from read-only to writable. This occurs because the vmclock_miscdev_mmap() function fails to properly restrict permission upgrades. As a result, the guest can corrupt critical host-written timekeeping data, such as the sequence counter and Coordinated Universal Time (UTC), leading to data integrity issues.	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 2026-08-28 07:47:12 UTC

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

ptp: vmclock: prevent read-only mappings from becoming writable

vmclock_miscdev_mmap() rejects writable mappings of the shared vmclock
ABI page with -EROFS, but leaves VM_MAYWRITE set.  Userspace can map the
page read-only and then upgrade it to writable with mprotect(), after
which the guest can corrupt the host-written timekeeping data (sequence
counter, UTC time, TSC offset) that the vmclock ABI defines as read-only.

Clear VM_MAYWRITE on the read-only path so the mapping cannot be
upgraded, as i915 does for its read-only objects and as fixed in drm/vc4
(CVE-2026-68445) and drm/panthor (CVE-2024-53071).

Comment 1 gkamathe 2026-08-31 14:36:30 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026082811-CVE-2026-80724-bc86@gregkh/T