Bug 2516388 (CVE-2026-72173)

Summary:	CVE-2026-72173 kernel: fs/proc/task_mmu: do not warn on seeing non-migration pmd entry
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	low	Docs Contact:
Priority:	low
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 memory management unit (MMU). The `pagemap_pmd_range_thp()` function incorrectly issued a warning when encountering certain non-present Page Middle Directory (PMD) entries. This issue arose because an assertion related to migration-only softleaf entries became outdated after the introduction of device-private PMD entries. While not directly exploitable for arbitrary code execution or privilege escalation, this flaw could lead to misleading diagnostic information within the kernel.	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 2026-08-15 06:09:51 UTC

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

fs/proc/task_mmu: do not warn on seeing non-migration pmd entry

Patch series "mm/hmm: A fix and a selftest", v3.

Patch 1 fixes a stale warning present from the time when only migration
softleaf entries were supported at the PMD level.

Patch 2 adds some code into hmm-tests.c which exercises the pagemap path
for PMD device-private entries.


This patch (of 2):

pagemap_pmd_range_thp() warns if a non-present PMD is not a migration
entry.  This became false once device-private entries at the PMD level
were added.

Therefore, remove the stale migration-only assertion.

Comment 1 gkamathe 2026-08-18 08:37:07 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081538-CVE-2026-72173-a582@gregkh/T