---
id: CVE-2026-64472
title: 'vfio/mlx5: Fix racy bitfields and tighten struct layout'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  vfio/mlx5: Fix racy bitfields and tighten struct layout

  Bitfield operations are not atomic, they use a read-modify-write
  pattern, therefore we should be careful not to…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 61a2f1460fd03285ea34c1a235f2f50f71e13a1f <
    1dd99b8f4e143592e12e5a77e7b538bc698116cb
  - >-
    Linux >= 61a2f1460fd03285ea34c1a235f2f50f71e13a1f <
    f1db80a67da928a92ba460ede1be52d8941f46be
  - >-
    Linux >= 61a2f1460fd03285ea34c1a235f2f50f71e13a1f <
    399d806f998f7a25405fc1b97227e579aead24af
  - >-
    Linux >= 61a2f1460fd03285ea34c1a235f2f50f71e13a1f <
    7ed120b1a007bace57c461805519d70e1af44e59
  - >-
    Linux >= 61a2f1460fd03285ea34c1a235f2f50f71e13a1f <
    39d163627b51886492bf31f66cb02c94613d2287
  - >-
    Linux >= 61a2f1460fd03285ea34c1a235f2f50f71e13a1f <
    f2365a63b02ddea32e7db78b742c2503ec7b81f1
  - Linux 5.19
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-06T16:39:33.414588Z'
published: '2026-07-25'
updated: '2026-11-06'
sourceUpdated: '2026-11-06T16:44:53.516Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-64472'
references:
  - url: 'https://git.kernel.org/stable/c/1dd99b8f4e143592e12e5a77e7b538bc698116cb'
  - url: 'https://git.kernel.org/stable/c/f1db80a67da928a92ba460ede1be52d8941f46be'
  - url: 'https://git.kernel.org/stable/c/399d806f998f7a25405fc1b97227e579aead24af'
  - url: 'https://git.kernel.org/stable/c/7ed120b1a007bace57c461805519d70e1af44e59'
  - url: 'https://git.kernel.org/stable/c/39d163627b51886492bf31f66cb02c94613d2287'
  - url: 'https://git.kernel.org/stable/c/f2365a63b02ddea32e7db78b742c2503ec7b81f1'
tags:
  - cve.org
epss: 0.00181
epssPercentile: 0.07708
ingestedAt: '2026-11-06T16:57:43.167Z'
---

## Overview

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

vfio/mlx5: Fix racy bitfields and tighten struct layout

Bitfield operations are not atomic, they use a read-modify-write
pattern, therefore we should be careful not to pack bitfields that
can be concurrently updated into the same storage unit.

This split takes a binary approach: flags that are only modified
pre/post open/close remain bitfields, flags modified from user
action, including actions that reach across to another device (ex.
reset) use dedicated storage units.

Note mlx5_vhca_page_tracker.status is relocated to fill the alignment
hole this split exposes.

Bitfield justifications:

  migrate_cap: written only in mlx5vf_cmd_set_migratable() at probe
  chunk_mode: written only in mlx5vf_cmd_set_migratable() at probe
  mig_state_cap: written only in mlx5vf_cmd_set_migratable() at probe

Dedicated storage units:

  mdev_detach: written in the VF attach/detach event notifier
               mlx5fv_vf_event() at runtime
  log_active: written in mlx5vf_start_page_tracker()/
              mlx5vf_stop_page_tracker() during runtime dirty tracking
  deferred_reset: written in mlx5vf_state_mutex_unlock()/
                  mlx5vf_pci_aer_reset_done() during runtime reset handling
  is_err: set by tracker error handling and dirty-log polling at runtime
  object_changed: set by tracker event handling and cleared by dirty-log
                  polling at runtime

## Affected

- `Linux >= 61a2f1460fd03285ea34c1a235f2f50f71e13a1f < 1dd99b8f4e143592e12e5a77e7b538bc698116cb`
- `Linux >= 61a2f1460fd03285ea34c1a235f2f50f71e13a1f < f1db80a67da928a92ba460ede1be52d8941f46be`
- `Linux >= 61a2f1460fd03285ea34c1a235f2f50f71e13a1f < 399d806f998f7a25405fc1b97227e579aead24af`
- `Linux >= 61a2f1460fd03285ea34c1a235f2f50f71e13a1f < 7ed120b1a007bace57c461805519d70e1af44e59`
- `Linux >= 61a2f1460fd03285ea34c1a235f2f50f71e13a1f < 39d163627b51886492bf31f66cb02c94613d2287`
- `Linux >= 61a2f1460fd03285ea34c1a235f2f50f71e13a1f < f2365a63b02ddea32e7db78b742c2503ec7b81f1`
- `Linux 5.19`

## Remediation

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