Bug 2532120 (CVE-2026-89567)

Summary:	CVE-2026-89567 kernel: jbd2: bound shrinker scans by examined checkpoint buffers
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's jbd2 shrinker. This component, which manages journal buffers, does not correctly account for busy checkpoint buffers. This oversight can cause the shrinker to hold a critical system lock for an extended period when processing many busy buffers. The prolonged lock contention can lead to system unresponsiveness, such as soft lockups or RCU stalls, ultimately resulting in a Denial of Service (DoS).	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 2026-09-11 20:45:53 UTC

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

jbd2: bound shrinker scans by examined checkpoint buffers

The jbd2 shrinker currently accounts only checkpoint buffers that it
successfully releases against nr_to_scan.  Busy buffers therefore do not
consume the scan budget.

If a checkpoint transaction contains mostly busy buffers, the shrinker
can scan its entire checkpoint list while holding journal->j_list_lock.
Large checkpoint lists can result in excessive lock hold times and leave
other CPUs spinning on j_list_lock, causing soft lockups or RCU stalls.

Pass nr_to_scan into journal_shrink_one_cp_list() and decrement it for
every buffer examined, including busy buffers.  Pass NULL from checkpoint
cleanup paths so their existing full-list behavior is preserved.

This restores the scan-budget semantics that existed before
journal_shrink_one_cp_list() was changed to always scan a complete
checkpoint list.

Comment 1 gkamathe 2026-09-15 15:41:27 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89567.mbox