Bug 2541254 (CVE-2026-97534)

Summary:	CVE-2026-97534 kernel: f2fs: accurately adjust free_sections during free_segment_range
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 Flash-Friendly File System (F2FS). When segment ranges are truncated, the file system fails to properly adjust the free section counter for sections that were already marked free, leading to an overestimation of available storage during background garbage collection. A local user could exploit this flaw under low-space conditions to trigger allocation failures or kernel assertion errors, resulting in a Denial of Service (DoS).	Story Points:	---
Clone Of:		Environment:
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 2026-09-25 11:11:11 UTC

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

f2fs: accurately adjust free_sections during free_segment_range

In free_segment_range(), MAIN_SECS(sbi) is temporarily reduced by `secs`
to restrict block allocation to the safe remaining main area while valid
blocks in the truncated range are evacuated by GC.

However, FREE_I(sbi)->free_sections tracks the total number of free
sections across the whole filesystem. If any sections within the
truncated range were already free upon entering free_segment_range(),
failing to deduct them from free_sections causes the filesystem to
overestimate available free sections in the active, reduced main area.
This leads to inconsistent free section accounting during GC data
migration and can trigger unexpected allocation failures or assertion
errors when space is tight.

Fix this by calculating the number of already-free sections in the
truncated range, deducting them from free_sections upon entering
free_segment_range(), and restoring them on exit.

Comment 1 gkamathe 2026-09-28 20:36:04 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-97534.mbox