---
id: CVE-2026-80807
title: 'nilfs2: reject invalid block index in GC ioctl'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  nilfs2: reject invalid block index in GC ioctl

  Syzbot reported list corruption caused by a double list_add_tail() call on
  bh->b_assoc_buffers within nilfs_lookup_dirty…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 7942b919f7321f95a777d396ff7894a7a83dc9b0 <
    898404cdf882d7b54f1132f75570984ca3214796
  - >-
    Linux >= 7942b919f7321f95a777d396ff7894a7a83dc9b0 <
    ba8a8b563a28d358c45c62a306d421434a058648
  - >-
    Linux >= 7942b919f7321f95a777d396ff7894a7a83dc9b0 <
    3bd064ccc70b85f9a3d53aece29dc8473be5a226
  - >-
    Linux >= 7942b919f7321f95a777d396ff7894a7a83dc9b0 <
    a5e776e2937581d67ec5b9b4d27b0f70d7baa6b1
  - >-
    Linux >= 7942b919f7321f95a777d396ff7894a7a83dc9b0 <
    68aa9ab6f8f2895713aa6ddf781463ed8ea5ba44
  - >-
    Linux >= 7942b919f7321f95a777d396ff7894a7a83dc9b0 <
    e447f7edb99bd00cec63d6f3049e2e5074946f71
  - >-
    Linux >= 7942b919f7321f95a777d396ff7894a7a83dc9b0 <
    ec6ddf271dfa4c7e3147bc2c8b2bad4315f316a1
  - >-
    Linux >= 7942b919f7321f95a777d396ff7894a7a83dc9b0 <
    fbcfb75c20d71a5b542ad4ac3b79d10b997c8152
  - >-
    Linux >= 7942b919f7321f95a777d396ff7894a7a83dc9b0 <
    a1735eae55448bc79c2da6593455791e886f6ed8
  - Linux 2.6.30
published: '2026-09-04'
updated: '2026-10-19'
sourceUpdated: '2026-10-19T08:44:00.360Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-80807'
references:
  - url: 'https://git.kernel.org/stable/c/898404cdf882d7b54f1132f75570984ca3214796'
  - url: 'https://git.kernel.org/stable/c/ba8a8b563a28d358c45c62a306d421434a058648'
  - url: 'https://git.kernel.org/stable/c/3bd064ccc70b85f9a3d53aece29dc8473be5a226'
  - url: 'https://git.kernel.org/stable/c/a5e776e2937581d67ec5b9b4d27b0f70d7baa6b1'
  - url: 'https://git.kernel.org/stable/c/68aa9ab6f8f2895713aa6ddf781463ed8ea5ba44'
  - url: 'https://git.kernel.org/stable/c/e447f7edb99bd00cec63d6f3049e2e5074946f71'
  - url: 'https://git.kernel.org/stable/c/ec6ddf271dfa4c7e3147bc2c8b2bad4315f316a1'
  - url: 'https://git.kernel.org/stable/c/fbcfb75c20d71a5b542ad4ac3b79d10b997c8152'
  - url: 'https://git.kernel.org/stable/c/a1735eae55448bc79c2da6593455791e886f6ed8'
tags:
  - cve.org
epss: 0.00201
epssPercentile: 0.0926
ingestedAt: '2026-10-19T09:16:01.525Z'
---

## Overview

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

nilfs2: reject invalid block index in GC ioctl

Syzbot reported list corruption caused by a double list_add_tail() call on
bh->b_assoc_buffers within nilfs_lookup_dirty_data_buffers().

Analysis revealed that the root cause was the insertion of a page/folio
with a page index of ULONG_MAX into the page cache via the GC ioctl.
filemap_get_folios_tag(), called by nilfs_lookup_dirty_data_buffers(),
repeatedly detects a dirty folio with a page index of ULONG_MAX due to
index wrap-around, leading to duplicate processing of dirty buffers.

As a preparatory step, the GC ioctl loads the page/folio of the block to
be moved during GC and inserts it into the page cache based on information
in the nilfs_vdesc structure passed as an argument.  Normally, this does
not cause issues because the user-space GC library configures the
nilfs_vdesc structure properly.  However, since there is no range check on
the parameters determining the page index, a request with artificially
crafted parameters -- such as those generated by Syzbot -- can result in a
page/folio being inserted with a page index of ULONG_MAX, triggering the
above problem.

This resolves the issue by checking the ranges of 'vd_offset' and
'vd_vblocknr' in the nilfs_vdesc structure that determine the page index,
thereby preventing the invalid page/folio insertions.

## Affected

- `Linux >= 7942b919f7321f95a777d396ff7894a7a83dc9b0 < 898404cdf882d7b54f1132f75570984ca3214796`
- `Linux >= 7942b919f7321f95a777d396ff7894a7a83dc9b0 < ba8a8b563a28d358c45c62a306d421434a058648`
- `Linux >= 7942b919f7321f95a777d396ff7894a7a83dc9b0 < 3bd064ccc70b85f9a3d53aece29dc8473be5a226`
- `Linux >= 7942b919f7321f95a777d396ff7894a7a83dc9b0 < a5e776e2937581d67ec5b9b4d27b0f70d7baa6b1`
- `Linux >= 7942b919f7321f95a777d396ff7894a7a83dc9b0 < 68aa9ab6f8f2895713aa6ddf781463ed8ea5ba44`
- `Linux >= 7942b919f7321f95a777d396ff7894a7a83dc9b0 < e447f7edb99bd00cec63d6f3049e2e5074946f71`
- `Linux >= 7942b919f7321f95a777d396ff7894a7a83dc9b0 < ec6ddf271dfa4c7e3147bc2c8b2bad4315f316a1`
- `Linux >= 7942b919f7321f95a777d396ff7894a7a83dc9b0 < fbcfb75c20d71a5b542ad4ac3b79d10b997c8152`
- `Linux >= 7942b919f7321f95a777d396ff7894a7a83dc9b0 < a1735eae55448bc79c2da6593455791e886f6ed8`
- `Linux 2.6.30`

## Remediation

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