---
id: CVE-2025-21722
title: 'nilfs2: do not force clear folio if buffer is referenced'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  nilfs2: do not force clear folio if buffer is referenced

  Patch series "nilfs2: protect busy buffer heads from being force-cleared".

  This series fixes the buffer head …
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
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 8c26c4e2694a163d525976e804d81cd955bbb40c <
    7d0544bacc11d6aa26ecd7debf9353193c7a3328
  - >-
    Linux >= 8c26c4e2694a163d525976e804d81cd955bbb40c <
    4d042811c72f71be7c14726db2c72b67025a7cb5
  - >-
    Linux >= 8c26c4e2694a163d525976e804d81cd955bbb40c <
    f51ff43c4c5a6c8e72d0aca89e4d5e688938412f
  - >-
    Linux >= 8c26c4e2694a163d525976e804d81cd955bbb40c <
    19296737024cd220a1d6590bf4c092bca8c99497
  - >-
    Linux >= 8c26c4e2694a163d525976e804d81cd955bbb40c <
    8458c686d50a804611b97038dd6e75a474ac2221
  - >-
    Linux >= 8c26c4e2694a163d525976e804d81cd955bbb40c <
    1098bb8d52419d262a3358d099a1598a920b730f
  - >-
    Linux >= 8c26c4e2694a163d525976e804d81cd955bbb40c <
    557ccf5e49f1fb848a29698585bcab2e50a597ef
  - >-
    Linux >= 8c26c4e2694a163d525976e804d81cd955bbb40c <
    ca76bb226bf47ff04c782cacbd299f12ddee1ec1
  - Linux 3.10
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2025-02-27T18:14:37.739187Z'
published: '2025-02-27'
updated: '2026-10-21'
sourceUpdated: '2026-10-21T12:35:56.141Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2025-21722'
references:
  - url: 'https://git.kernel.org/stable/c/7d0544bacc11d6aa26ecd7debf9353193c7a3328'
  - url: 'https://git.kernel.org/stable/c/4d042811c72f71be7c14726db2c72b67025a7cb5'
  - url: 'https://git.kernel.org/stable/c/f51ff43c4c5a6c8e72d0aca89e4d5e688938412f'
  - url: 'https://git.kernel.org/stable/c/19296737024cd220a1d6590bf4c092bca8c99497'
  - url: 'https://git.kernel.org/stable/c/8458c686d50a804611b97038dd6e75a474ac2221'
  - url: 'https://git.kernel.org/stable/c/1098bb8d52419d262a3358d099a1598a920b730f'
  - url: 'https://git.kernel.org/stable/c/557ccf5e49f1fb848a29698585bcab2e50a597ef'
  - url: 'https://git.kernel.org/stable/c/ca76bb226bf47ff04c782cacbd299f12ddee1ec1'
tags:
  - cve.org
epss: 0.00272
epssPercentile: 0.19449
ingestedAt: '2026-10-21T12:48:53.719Z'
---

## Overview

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

nilfs2: do not force clear folio if buffer is referenced

Patch series "nilfs2: protect busy buffer heads from being force-cleared".

This series fixes the buffer head state inconsistency issues reported by
syzbot that occurs when the filesystem is corrupted and falls back to
read-only, and the associated buffer head use-after-free issue.


This patch (of 2):

Syzbot has reported that after nilfs2 detects filesystem corruption and
falls back to read-only, inconsistencies in the buffer state may occur.

One of the inconsistencies is that when nilfs2 calls mark_buffer_dirty()
to set a data or metadata buffer as dirty, but it detects that the buffer
is not in the uptodate state:

 WARNING: CPU: 0 PID: 6049 at fs/buffer.c:1177 mark_buffer_dirty+0x2e5/0x520
  fs/buffer.c:1177
 ...
 Call Trace:
  <TASK>
  nilfs_palloc_commit_alloc_entry+0x4b/0x160 fs/nilfs2/alloc.c:598
  nilfs_ifile_create_inode+0x1dd/0x3a0 fs/nilfs2/ifile.c:73
  nilfs_new_inode+0x254/0x830 fs/nilfs2/inode.c:344
  nilfs_mkdir+0x10d/0x340 fs/nilfs2/namei.c:218
  vfs_mkdir+0x2f9/0x4f0 fs/namei.c:4257
  do_mkdirat+0x264/0x3a0 fs/namei.c:4280
  __do_sys_mkdirat fs/namei.c:4295 [inline]
  __se_sys_mkdirat fs/namei.c:4293 [inline]
  __x64_sys_mkdirat+0x87/0xa0 fs/namei.c:4293
  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
  do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
  entry_SYSCALL_64_after_hwframe+0x77/0x7f

The other is when nilfs_btree_propagate(), which propagates the dirty
state to the ancestor nodes of a b-tree that point to a dirty buffer,
detects that the origin buffer is not dirty, even though it should be:

 WARNING: CPU: 0 PID: 5245 at fs/nilfs2/btree.c:2089
  nilfs_btree_propagate+0xc79/0xdf0 fs/nilfs2/btree.c:2089
 ...
 Call Trace:
  <TASK>
  nilfs_bmap_propagate+0x75/0x120 fs/nilfs2/bmap.c:345
  nilfs_collect_file_data+0x4d/0xd0 fs/nilfs2/segment.c:587
  nilfs_segctor_apply_buffers+0x184/0x340 fs/nilfs2/segment.c:1006
  nilfs_segctor_scan_file+0x28c/0xa50 fs/nilfs2/segment.c:1045
  nilfs_segctor_collect_blocks fs/nilfs2/segment.c:1216 [inline]
  nilfs_segctor_collect fs/nilfs2/segment.c:1540 [inline]
  nilfs_segctor_do_construct+0x1c28/0x6b90 fs/nilfs2/segment.c:2115
  nilfs_segctor_construct+0x181/0x6b0 fs/nilfs2/segment.c:2479
  nilfs_segctor_thread_construct fs/nilfs2/segment.c:2587 [inline]
  nilfs_segctor_thread+0x69e/0xe80 fs/nilfs2/segment.c:2701
  kthread+0x2f0/0x390 kernel/kthread.c:389
  ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
  </TASK>

Both of these issues are caused by the callbacks that handle the
page/folio write requests, forcibly clear various states, including the
working state of the buffers they hold, at unexpected times when they
detect read-only fallback.

Fix these issues by checking if the buffer is referenced before clearing
the page/folio state, and skipping the clear if it is.

## Affected

- `Linux >= 8c26c4e2694a163d525976e804d81cd955bbb40c < 7d0544bacc11d6aa26ecd7debf9353193c7a3328`
- `Linux >= 8c26c4e2694a163d525976e804d81cd955bbb40c < 4d042811c72f71be7c14726db2c72b67025a7cb5`
- `Linux >= 8c26c4e2694a163d525976e804d81cd955bbb40c < f51ff43c4c5a6c8e72d0aca89e4d5e688938412f`
- `Linux >= 8c26c4e2694a163d525976e804d81cd955bbb40c < 19296737024cd220a1d6590bf4c092bca8c99497`
- `Linux >= 8c26c4e2694a163d525976e804d81cd955bbb40c < 8458c686d50a804611b97038dd6e75a474ac2221`
- `Linux >= 8c26c4e2694a163d525976e804d81cd955bbb40c < 1098bb8d52419d262a3358d099a1598a920b730f`
- `Linux >= 8c26c4e2694a163d525976e804d81cd955bbb40c < 557ccf5e49f1fb848a29698585bcab2e50a597ef`
- `Linux >= 8c26c4e2694a163d525976e804d81cd955bbb40c < ca76bb226bf47ff04c782cacbd299f12ddee1ec1`
- `Linux 3.10`

## Remediation

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