---
id: CVE-2025-21939
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  drm/xe/hmm: Don't dereference struct page pointers without notifier lock

  The pnfs that we obtain from hmm_range_fault() point to pages that
  we don't have a reference o…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  drm/xe/hmm: Don't dereference struct page pointers without notifier lock

  The pnfs that we obtain from hmm_range_fault() point to pages that
  we don't have a reference o…
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'
cwe:
  - CWE-476
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 6.10, < 6.12.19'
  - 'linux_kernel >= 6.13, < 6.13.7'
  - linux_kernel = 6.14
patched:
  - linux_kernel 6.13.7
published: '2025-04-01'
updated: '2026-07-30'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-21939'
references:
  - url: 'https://git.kernel.org/stable/c/0a98219bcc961edd3388960576e4353e123b4a51'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/2a24c98f0e4cc994334598d4f3a851972064809d'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/f9326f529da7298a95643c3267f1c0fdb0db55eb'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
epss: 0.00212
epssPercentile: 0.10241
ingestedAt: '2026-07-30T18:55:15.060Z'
---

## Overview

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

drm/xe/hmm: Don't dereference struct page pointers without notifier lock

The pnfs that we obtain from hmm_range_fault() point to pages that
we don't have a reference on, and the guarantee that they are still
in the cpu page-tables is that the notifier lock must be held and the
notifier seqno is still valid.

So while building the sg table and marking the pages accesses / dirty
we need to hold this lock with a validated seqno.

However, the lock is reclaim tainted which makes
sg_alloc_table_from_pages_segment() unusable, since it internally
allocates memory.

Instead build the sg-table manually. For the non-iommu case
this might lead to fewer coalesces, but if that's a problem it can
be fixed up later in the resource cursor code. For the iommu case,
the whole sg-table may still be coalesced to a single contigous
device va region.

This avoids marking pages that we don't own dirty and accessed, and
it also avoid dereferencing struct pages that we don't own.

v2:
- Use assert to check whether hmm pfns are valid (Matthew Auld)
- Take into account that large pages may cross range boundaries
  (Matthew Auld)

v3:
- Don't unnecessarily check for a non-freed sg-table. (Matthew Auld)
- Add a missing up_read() in an error path. (Matthew Auld)

(cherry picked from commit ea3e66d280ce2576664a862693d1da8fd324c317)

## Affected

- `linux_kernel >= 6.10, < 6.12.19`
- `linux_kernel >= 6.13, < 6.13.7`
- `linux_kernel = 6.14`

## Remediation

Upgrade past the affected range:

- `linux_kernel 6.13.7`