Bug 2536571 (CVE-2026-90272)

Summary:	CVE-2026-90272 kernel: perf: arm_pmuv3: Zero initialize hw_id branch stack field
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 `perf: arm_pmuv3` component. The `hw_id` branch stack field, which is passed to userspace, was not properly initialized by the Branch Record Buffer Extension (BRBE) driver. This could lead to the disclosure of uninitialized memory to userspace, potentially allowing an attacker to gain sensitive information or cause unexpected behavior.	Story Points:	---
Clone Of:		Environment:
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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 2026-09-17 18:28:03 UTC

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

perf: arm_pmuv3: Zero initialize hw_id branch stack field

PERF_SAMPLE_BRANCH_HW_INDEX is supported by BRBE so hw_id is passed to
userspace, but it's never set by the BRBE driver. Zero initialize it as
it should be according to the docs:

   * For the architectures whose raw branch records are
   * already stored in age order, the hw_idx should be 0.

It's probably too risky to remove PERF_SAMPLE_BRANCH_HW_INDEX from BRBE
now in case anyone is setting it and reading the value, but zero
initializing the whole struct also protects against the same issue with
new fields that are added in the future.

Comment 1 gkamathe 2026-09-23 23:30:23 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-90272.mbox