---
id: CVE-2026-43065
title: 'ext4: always drain queued discard work in ext4_mb_release()'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ext4: always drain queued discard work in ext4_mb_release()

  While reviewing recent ext4 patch[1], Sashiko raised the following
  concern[2]:

  > If the filesystem is init…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 55cdd0af2bc5ffc92a2deb745627755aecd5db33 <
    e96c2354b170aaa53300c8e8fd59e41b133160f7
  - >-
    Linux >= 55cdd0af2bc5ffc92a2deb745627755aecd5db33 <
    c360e9d0def4f4ae03254a67c683103908555b75
  - >-
    Linux >= 55cdd0af2bc5ffc92a2deb745627755aecd5db33 <
    1c82f863f090ab899085bdfade073313384b514b
  - >-
    Linux >= 55cdd0af2bc5ffc92a2deb745627755aecd5db33 <
    9b4d9dda6a71ad3425c8109d27c4c6bfb9da97b8
  - >-
    Linux >= 55cdd0af2bc5ffc92a2deb745627755aecd5db33 <
    812b6a7cd3e7f3a3e8a24db85bc6313c26cb1098
  - >-
    Linux >= 55cdd0af2bc5ffc92a2deb745627755aecd5db33 <
    b4737e26d4688b8aea88ad6ea4dbfeb6e78b0327
  - >-
    Linux >= 55cdd0af2bc5ffc92a2deb745627755aecd5db33 <
    9ee29d20aab228adfb02ca93f87fb53c56c2f3af
  - Linux 5.15
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-06T15:27:46.955616Z'
published: '2026-05-05'
updated: '2026-11-06'
sourceUpdated: '2026-11-06T15:32:29.604Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-43065'
references:
  - url: 'https://git.kernel.org/stable/c/e96c2354b170aaa53300c8e8fd59e41b133160f7'
  - url: 'https://git.kernel.org/stable/c/c360e9d0def4f4ae03254a67c683103908555b75'
  - url: 'https://git.kernel.org/stable/c/1c82f863f090ab899085bdfade073313384b514b'
  - url: 'https://git.kernel.org/stable/c/9b4d9dda6a71ad3425c8109d27c4c6bfb9da97b8'
  - url: 'https://git.kernel.org/stable/c/812b6a7cd3e7f3a3e8a24db85bc6313c26cb1098'
  - url: 'https://git.kernel.org/stable/c/b4737e26d4688b8aea88ad6ea4dbfeb6e78b0327'
  - url: 'https://git.kernel.org/stable/c/9ee29d20aab228adfb02ca93f87fb53c56c2f3af'
tags:
  - cve.org
epss: 0.00117
epssPercentile: 0.01648
ingestedAt: '2026-11-06T15:54:04.028Z'
---

## Overview

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

ext4: always drain queued discard work in ext4_mb_release()

While reviewing recent ext4 patch[1], Sashiko raised the following
concern[2]:

> If the filesystem is initially mounted with the discard option,
> deleting files will populate sbi->s_discard_list and queue
> s_discard_work. If it is then remounted with nodiscard, the
> EXT4_MOUNT_DISCARD flag is cleared, but the pending s_discard_work is
> neither cancelled nor flushed.

[1] https://lore.kernel.org/r/20260319094545.19291-1-qiang.zhang@linux.dev/
[2] https://sashiko.dev/#/patchset/20260319094545.19291-1-qiang.zhang%40linux.dev

The concern was valid, but it had nothing to do with the patch[1].
One of the problems with Sashiko in its current (early) form is that
it will detect pre-existing issues and report it as a problem with the
patch that it is reviewing.

In practice, it would be hard to hit deliberately (unless you are a
malicious syzkaller fuzzer), since it would involve mounting the file
system with -o discard, and then deleting a large number of files,
remounting the file system with -o nodiscard, and then immediately
unmounting the file system before the queued discard work has a change
to drain on its own.

Fix it because it's a real bug, and to avoid Sashiko from raising this
concern when analyzing future patches to mballoc.c.

## Affected

- `Linux >= 55cdd0af2bc5ffc92a2deb745627755aecd5db33 < e96c2354b170aaa53300c8e8fd59e41b133160f7`
- `Linux >= 55cdd0af2bc5ffc92a2deb745627755aecd5db33 < c360e9d0def4f4ae03254a67c683103908555b75`
- `Linux >= 55cdd0af2bc5ffc92a2deb745627755aecd5db33 < 1c82f863f090ab899085bdfade073313384b514b`
- `Linux >= 55cdd0af2bc5ffc92a2deb745627755aecd5db33 < 9b4d9dda6a71ad3425c8109d27c4c6bfb9da97b8`
- `Linux >= 55cdd0af2bc5ffc92a2deb745627755aecd5db33 < 812b6a7cd3e7f3a3e8a24db85bc6313c26cb1098`
- `Linux >= 55cdd0af2bc5ffc92a2deb745627755aecd5db33 < b4737e26d4688b8aea88ad6ea4dbfeb6e78b0327`
- `Linux >= 55cdd0af2bc5ffc92a2deb745627755aecd5db33 < 9ee29d20aab228adfb02ca93f87fb53c56c2f3af`
- `Linux 5.15`

## Remediation

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