Bug 2536450 (CVE-2026-90266)

Summary:	CVE-2026-90266 kernel: btrfs: zoned: don't force read-only on transient -EAGAIN from reloc merge
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
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
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in the Linux kernel's btrfs zoned filesystem. When metadata over-commitment occurs during a reclaim operation, the `btrfs_delayed_refs_rsv_refill()` function may return a transient error (`-EAGAIN`). This error can cause the current transaction to abort, leading to the filesystem being forced into a read-only state. This could result in a denial of service, preventing further write operations until the system is restarted or the issue is manually resolved.	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 2026-09-17 17:58:02 UTC

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

btrfs: zoned: don't force read-only on transient -EAGAIN from reloc merge

On a zoned FS, btrfs_delayed_refs_rsv_refill() returns -EAGAIN whenever
the over-committed metadata plus the zone_unusable bytes exceeds the
usable size in a metadata block-group to avoid heavy over-commit of
metadata and early ENOSPC in one transaction.

If this happens while doing reclaim, the transaction is getting aborted.

Treat -EAGAIN as a soft, retryable condition in case of block-group
reclaim.

Comment 1 gkamathe 2026-09-23 22:32:53 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-90266.mbox