Bug 2532027 (CVE-2026-89593)

Summary:	CVE-2026-89593 kernel: hugetlb: only adjust reservation during unmapping if mapcount is 0
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:	akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
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Doc Text:	A flaw was found in the Linux kernel's huge page (hugetlb) subsystem. This vulnerability occurs when a huge page of memory is shared between a parent and a child process. If the parent process unmaps the huge page before the child, the system can incorrectly reduce the count of reserved huge pages. This error can lead to system instability or a denial of service, making the system unresponsive or unavailable.	Story Points:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-09-11 20:05:21 UTC

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

hugetlb: only adjust reservation during unmapping if mapcount is 0

Since df7a6d1f6405, __unmap_hugepage_range can adjust reservations.  In
the case of folio mapped in both a parent and a child, if the parent
unmaps the range first, the reservation adjustment will result in an
underflow of the reserved count.  Once the child unmaps the range, the
count is restored.  Change __unmap_hugepage_range() to check the mapcount
before adjusting the reservation.

Comment 1 Mauro Matteo Cascella 2026-09-14 09:25:04 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89593.mbox