Bug 2532017 (CVE-2026-89503)

Summary:	CVE-2026-89503 kernel: ring-buffer: Fix subbuf resize race with ring_buffer_alloc_read_page()
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 ring-buffer component. A race condition exists in the `ring_buffer_alloc_read_page()` function when it interacts with `ring_buffer_subbuf_order_set`. This can lead to an incorrect memory allocation where the buffer page's order (`bpage->order`) does not match the actual allocated memory. This mismatch could potentially cause system instability or a denial of service.	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 20:00:29 UTC

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

ring-buffer: Fix subbuf resize race with ring_buffer_alloc_read_page()

ring_buffer_alloc_read_page() is racy with ring_buffer_subbuf_order_set,
it can allocate a reader page with an outdated order. This isn't a big
issue, the user can still re-allocate a new reader page and try again.

However, what is more problematic is if the value of subbuf_order
changes in the middle of ring_buffer_alloc_read_page(). In that case,
bpage->order might not match the actual allocated memory.

Use bpage->order for the allocation to prevent this race.

Comment 1 Mauro Matteo Cascella 2026-09-14 07:58:51 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89503.mbox