---
id: CVE-2026-80876
title: 'ring-buffer: Fix event length with forced 8-byte alignment'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ring-buffer: Fix event length with forced 8-byte alignment

  When RB_FORCE_8BYTE_ALIGNMENT is true, rb_calculate_event_length()
  reserves the space of event->array[0] for…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 2271048d1b3b0aabf83d25b29c20646dcabedc05 <
    7c9f0ccf9f04142458d2ac3d39414f4acae242f0
  - >-
    Linux >= 2271048d1b3b0aabf83d25b29c20646dcabedc05 <
    24c3fa71f9947b0e1f3b954db1b769b44140192e
  - >-
    Linux >= 2271048d1b3b0aabf83d25b29c20646dcabedc05 <
    14057268e79654c3e8ea2c9b5204cb9644b2964d
  - >-
    Linux >= 2271048d1b3b0aabf83d25b29c20646dcabedc05 <
    dbcb8635b1eb7603818591cf745c7b1d714f7ac6
  - >-
    Linux >= 2271048d1b3b0aabf83d25b29c20646dcabedc05 <
    cfada73fabe2ccc06ec77fe2ceaa088689213326
  - >-
    Linux >= 2271048d1b3b0aabf83d25b29c20646dcabedc05 <
    ec5e96aee75d27779b9a860307679f13f33adb0c
  - >-
    Linux >= 2271048d1b3b0aabf83d25b29c20646dcabedc05 <
    3a63a11897c7ba32d1be7a3fdbc48a8b01cf4992
  - >-
    Linux >= 2271048d1b3b0aabf83d25b29c20646dcabedc05 <
    c37e0a4b79a6bbb96ce5ffe279d7c001e20529e0
  - Linux 2.6.34
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-06T17:04:06.894723Z'
published: '2026-09-04'
updated: '2026-11-06'
sourceUpdated: '2026-11-06T17:05:55.519Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-80876'
references:
  - url: 'https://git.kernel.org/stable/c/7c9f0ccf9f04142458d2ac3d39414f4acae242f0'
  - url: 'https://git.kernel.org/stable/c/24c3fa71f9947b0e1f3b954db1b769b44140192e'
  - url: 'https://git.kernel.org/stable/c/14057268e79654c3e8ea2c9b5204cb9644b2964d'
  - url: 'https://git.kernel.org/stable/c/dbcb8635b1eb7603818591cf745c7b1d714f7ac6'
  - url: 'https://git.kernel.org/stable/c/cfada73fabe2ccc06ec77fe2ceaa088689213326'
  - url: 'https://git.kernel.org/stable/c/ec5e96aee75d27779b9a860307679f13f33adb0c'
  - url: 'https://git.kernel.org/stable/c/3a63a11897c7ba32d1be7a3fdbc48a8b01cf4992'
  - url: 'https://git.kernel.org/stable/c/c37e0a4b79a6bbb96ce5ffe279d7c001e20529e0'
tags:
  - cve.org
epss: 0.0022
epssPercentile: 0.12541
ingestedAt: '2026-11-06T18:00:12.531Z'
---

## Overview

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

ring-buffer: Fix event length with forced 8-byte alignment

When RB_FORCE_8BYTE_ALIGNMENT is true, rb_calculate_event_length()
reserves the space of event->array[0] for placing the data length and
rb_update_event() stores the data length in event->array[0]
accordingly. As a result the whole event length will add extra 4 bytes
for sizeof(event.array[0]) unconditionally.

But ring_buffer_event_length() only subtracts the
sizeof(event->array[0]) for events larger than RB_MAX_SMALL_DATA +
sizeof(event->array[0]). As a result, small events on architectures
with RB_FORCE_8BYTE_ALIGNMENT=true report a data length that is 4
bytes larger than expected.

To fix it, add the RB_FORCE_8BYTE_ALIGNMENT as a condition to subtract
the size of that length field whenever RB_FORCE_8BYTE_ALIGNMENT is
true.

This issue is observed in a riscv64 kernel with
CONFIG_HAVE_64BIT_ALIGNED_ACCESS set to y, when we run ftrace selftest
trace_marker_raw.tc, we get the weird log: for cases where the id is
1..100, the number of data field is 8*N, but once id exceeds 100, the
number of data field becomes 8*N+4:
 # 1 buf: 58 00 00 00 80 5e d1 63 (number of data field is 8*1)
 ...
 # a buf: 58 ...                  (number of data field is 8*2)
 ...
 # 64 buf: 58 ...                 (number of data field is 8*13)
 # 65 buf: 58 ...                 (number of data field is 8*13+4)

After applying this change, the number of data field keeps being 8*N+4
consistently.

## Affected

- `Linux >= 2271048d1b3b0aabf83d25b29c20646dcabedc05 < 7c9f0ccf9f04142458d2ac3d39414f4acae242f0`
- `Linux >= 2271048d1b3b0aabf83d25b29c20646dcabedc05 < 24c3fa71f9947b0e1f3b954db1b769b44140192e`
- `Linux >= 2271048d1b3b0aabf83d25b29c20646dcabedc05 < 14057268e79654c3e8ea2c9b5204cb9644b2964d`
- `Linux >= 2271048d1b3b0aabf83d25b29c20646dcabedc05 < dbcb8635b1eb7603818591cf745c7b1d714f7ac6`
- `Linux >= 2271048d1b3b0aabf83d25b29c20646dcabedc05 < cfada73fabe2ccc06ec77fe2ceaa088689213326`
- `Linux >= 2271048d1b3b0aabf83d25b29c20646dcabedc05 < ec5e96aee75d27779b9a860307679f13f33adb0c`
- `Linux >= 2271048d1b3b0aabf83d25b29c20646dcabedc05 < 3a63a11897c7ba32d1be7a3fdbc48a8b01cf4992`
- `Linux >= 2271048d1b3b0aabf83d25b29c20646dcabedc05 < c37e0a4b79a6bbb96ce5ffe279d7c001e20529e0`
- `Linux 2.6.34`

## Remediation

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