---
id: CVE-2026-89771
title: 'ring-buffer: Fix subbuf resize race with ring buffer readers'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ring-buffer: Fix subbuf resize race with ring buffer readers

  trace_buffer subbuf_size is read lockless in ring_buffer_read_page() and
  ring_buffer_read_start(), while i…
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
cwe:
  - CWE-366
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= f9b94daa542a8d2532f0930f01cd9aec2d19621b <
    6d666f0b8b36c0765cf19fbe6de5a7ba5a73aad9
  - >-
    Linux >= f9b94daa542a8d2532f0930f01cd9aec2d19621b <
    50f4a793c4ff24826efb0ac700989a5063cc53df
  - >-
    Linux >= f9b94daa542a8d2532f0930f01cd9aec2d19621b <
    0c7c517827a453128a8f58bfd849546a29813b27
  - >-
    Linux >= f9b94daa542a8d2532f0930f01cd9aec2d19621b <
    8a5f63637890f03177146efddaba5ec7a1b4d61f
  - Linux 6.8
published: '2026-09-11'
updated: '2026-10-19'
sourceUpdated: '2026-10-19T08:52:24.715Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-89771'
references:
  - url: 'https://git.kernel.org/stable/c/6d666f0b8b36c0765cf19fbe6de5a7ba5a73aad9'
  - url: 'https://git.kernel.org/stable/c/50f4a793c4ff24826efb0ac700989a5063cc53df'
  - url: 'https://git.kernel.org/stable/c/0c7c517827a453128a8f58bfd849546a29813b27'
  - url: 'https://git.kernel.org/stable/c/8a5f63637890f03177146efddaba5ec7a1b4d61f'
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89771.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-89771'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2532138'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-89771'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89771'
  - url: >-
      https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89771.mbox
tags:
  - cve.org
  - csaf
  - vex
  - red-hat
  - score-dispute
epss: 0.0012
epssPercentile: 0.01798
scores:
  cna: 7.8
  vendor: 5.5
ingestedAt: '2026-09-14T15:23:07.472Z'
---

## Overview

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

ring-buffer: Fix subbuf resize race with ring buffer readers

trace_buffer subbuf_size is read lockless in ring_buffer_read_page() and
ring_buffer_read_start(), while it can simultaneously be resized with
ring_buffer_subbuf_order_set().

Instead of trace_buffer::subbuf_size, use bpage::order in
ring_buffer_read_start() and ring_buffer_read_page().

In ring_buffer_read_start(), even with resize_disabled, there is still a
possibility of a race with a buffer modification. Hold the trace_buffer
mutex to synchronise with any pending ring buffer order modification.

trace_buffer::subbuf_size is now actually useless, remove it. Also,
create accessors rb_subbuf_capacity() and rb_page_capacity() which
return the actual size available for storing events, while
rb_subbuf_size() returns the actual subbuf page-size.

## Affected

- `Linux >= f9b94daa542a8d2532f0930f01cd9aec2d19621b < 6d666f0b8b36c0765cf19fbe6de5a7ba5a73aad9`
- `Linux >= f9b94daa542a8d2532f0930f01cd9aec2d19621b < 50f4a793c4ff24826efb0ac700989a5063cc53df`
- `Linux >= f9b94daa542a8d2532f0930f01cd9aec2d19621b < 0c7c517827a453128a8f58bfd849546a29813b27`
- `Linux >= f9b94daa542a8d2532f0930f01cd9aec2d19621b < 8a5f63637890f03177146efddaba5ec7a1b4d61f`
- `Linux 6.8`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Vendor advisories

- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 10, Red Hat OpenShift Container Platform 4 · updated 2026-09-15 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89771.json)