---
id: CVE-2026-74307
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ext4: validate donor file superblock early in EXT4_IOC_MOVE_EXT

  Reject the EXT4_IOC_MOVE_EXT ioctl early if the donor file does not
  belong to the same superblock as th…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ext4: validate donor file superblock early in EXT4_IOC_MOVE_EXT

  Reject the EXT4_IOC_MOVE_EXT ioctl early if the donor file does not
  belong to the same superblock as th…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= fcf6b1b729bcd23f2b49a84fb33ffbb44712ee6a <
    74796e886ca39fcb0d3fd36ea6a39c62784ab6fb
  - >-
    Linux >= fcf6b1b729bcd23f2b49a84fb33ffbb44712ee6a <
    29e07ec352f0ad06c833a18bf47d82c81f55544f
  - >-
    Linux >= fcf6b1b729bcd23f2b49a84fb33ffbb44712ee6a <
    fb52013cad9e9b7d3a6a14ea1bcd841e41da7c6c
  - >-
    Linux >= fcf6b1b729bcd23f2b49a84fb33ffbb44712ee6a <
    c143957520c6c9b5cd72e0de8b52b814f0c576fe
  - Linux 3.18
published: '2026-08-15'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T11:17:44.937'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-74307'
references:
  - url: 'https://git.kernel.org/stable/c/29e07ec352f0ad06c833a18bf47d82c81f55544f'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/74796e886ca39fcb0d3fd36ea6a39c62784ab6fb'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/c143957520c6c9b5cd72e0de8b52b814f0c576fe'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/fb52013cad9e9b7d3a6a14ea1bcd841e41da7c6c'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
epss: 0.00206
epssPercentile: 0.09998
ingestedAt: '2026-10-15T11:00:41.679Z'
---

## Overview

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

ext4: validate donor file superblock early in EXT4_IOC_MOVE_EXT

Reject the EXT4_IOC_MOVE_EXT ioctl early if the donor file does not
belong to the same superblock as the original file.  Currently, this
validation is performed inside ext4_move_extents() by
mext_check_validity(), but only after lock_two_nondirectories() has
already acquired the inode locks.  When the donor fd refers to a file
on a different filesystem (e.g., overlayfs), this late validation
creates a circular lock dependency:

  CPU0 (overlayfs write)            CPU1 (ext4 ioctl)
  ----                              ----
  inode_lock(ovl_inode)
                                    mnt_want_write_file(filp)
                                      sb_start_write(ext4_sb)   [sb_writers]
    backing_file_write_iter()
      vfs_iter_write(real_file)
        file_start_write(real_file)
          sb_start_write(ext4_sb)   [blocked by freeze]
                                    lock_two_nondirectories()
                                      inode_lock(ovl_inode)     [blocked]

With a concurrent freeze operation holding sb_writers write side, this
forms a deadlock cycle: CPU0 waits for freeze to complete, freeze waits
for CPU1's sb_writers reader to exit, CPU1 waits for CPU0's inode lock.

Since EXT4_IOC_MOVE_EXT exchanges physical extents between two files,
it fundamentally requires both files to reside on the same ext4
filesystem.  Moving the superblock check before any lock acquisition
is both semantically correct and eliminates the circular dependency
by ensuring that cross-filesystem donor fds are rejected before
sb_writers or inode locks are taken.

## Remediation

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