Bug 2532296 (CVE-2026-89568)

Summary:	CVE-2026-89568 kernel: kho: fix size calculation in kho_preserved_memory_reserve()
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:	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
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in the Linux kernel. The `kho_preserved_memory_reserve()` function, responsible for reserving memory, incorrectly calculates the size of these reservations. This issue arises because it uses a 32-bit integer for bit shifting, which limits the maximum reservation size to 2 Gigabytes (GiB). Consequently, attempts to reserve memory larger than 2 GiB can lead to undefined behavior, potentially causing system instability or a denial of service.	Story Points:	---
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Last Closed:		Type:	---
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Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-09-11 22:11:57 UTC

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

kho: fix size calculation in kho_preserved_memory_reserve()

kho_preserved_memory_reserve() calculates the size of a preservation by
doing 1 << (order + PAGE_SHIFT). Since the '1' is a 32-bit integer, it
can only be shifted by 31. That is, it will only work for preservations
up to 2 GiB. Larger preservations will trigger undefined behaviour.

While preservations larger than 2 GiB can't be obtained via folios
currently, they can be obtained via kho_preserve_pages().

For example, memblock reserve_mem uses kho_preserve_pages().
Reservations larger than 2 GiB are valid and will trigger this bug if
properly aligned.

Fix it by using 1UL for shifting.

Comment 1 Keith Grant 2026-09-18 16:11:08 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89568.mbox