---
id: CVE-2026-72367
title: 'iomap: guard io_size EOF trim against concurrent truncate underflow'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  iomap: guard io_size EOF trim against concurrent truncate underflow

  iomap: fix zero padding data issue in concurrent append writes
  changed ioend accounting so that io_…
severity: high
cvss: 8.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 82c59a86a247a8970d353d10f52a37e5564fb137 <
    cc1d6af0bee27d6595908b497424f338161299fc
  - >-
    Linux >= 51d20d1dacbec589d459e11fc88fbca419f84a99 <
    1f38f65bf965fce9aa159d45c5347538f56c5973
  - >-
    Linux >= 51d20d1dacbec589d459e11fc88fbca419f84a99 <
    7f7780abb4c0fdc9a2603aea8e985ff14ee900e0
  - >-
    Linux >= 51d20d1dacbec589d459e11fc88fbca419f84a99 <
    55ec50d046c03b3724741957f7b007856e36dbe7
  - Linux >= 6.12.10 < 6.12.114
  - Linux 6.13
published: '2026-08-15'
updated: '2026-10-21'
sourceUpdated: '2026-10-21T12:44:42.934Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-72367'
references:
  - url: 'https://git.kernel.org/stable/c/cc1d6af0bee27d6595908b497424f338161299fc'
  - url: 'https://git.kernel.org/stable/c/1f38f65bf965fce9aa159d45c5347538f56c5973'
  - url: 'https://git.kernel.org/stable/c/7f7780abb4c0fdc9a2603aea8e985ff14ee900e0'
  - url: 'https://git.kernel.org/stable/c/55ec50d046c03b3724741957f7b007856e36dbe7'
tags:
  - cve.org
epss: 0.00581
epssPercentile: 0.46771
ingestedAt: '2026-10-21T12:48:53.590Z'
---

## Overview

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

iomap: guard io_size EOF trim against concurrent truncate underflow

iomap: fix zero padding data issue in concurrent append writes
changed ioend accounting so that io_size tracks only valid data
within EOF.  This trims io_size when a writeback range extends
past end_pos:

    ioend->io_size += map_len;
    if (ioend->io_offset + ioend->io_size > end_pos)
        ioend->io_size = end_pos - ioend->io_offset;

However, if end_pos ends up below ioend->io_offset, the subtraction
becomes negative and is stored in size_t io_size, causing an unsigned
wrap to a huge value.  This can happen when writeback continues past
byte-level EOF up to a block-aligned range, or when a concurrent
truncate shrinks the file after end_pos was sampled in
iomap_writeback_handle_eof().

A wrapped io_size can mislead append detection and corrupt
completion-time size handling, since filesystem end_io paths consume
io_size for decisions such as on-disk EOF updates and unwritten/COW
completion ranges.

Fix this by clamping io_size to zero when EOF has moved to or before
the ioend start offset.  This preserves the original intent of trimming
io_size to valid in-EOF data while avoiding the underflow.

## Affected

- `Linux >= 82c59a86a247a8970d353d10f52a37e5564fb137 < cc1d6af0bee27d6595908b497424f338161299fc`
- `Linux >= 51d20d1dacbec589d459e11fc88fbca419f84a99 < 1f38f65bf965fce9aa159d45c5347538f56c5973`
- `Linux >= 51d20d1dacbec589d459e11fc88fbca419f84a99 < 7f7780abb4c0fdc9a2603aea8e985ff14ee900e0`
- `Linux >= 51d20d1dacbec589d459e11fc88fbca419f84a99 < 55ec50d046c03b3724741957f7b007856e36dbe7`
- `Linux >= 6.12.10 < 6.12.114`
- `Linux 6.13`

## Remediation

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