---
id: CVE-2021-47040
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  io_uring: fix overflows checks in provide buffers

  Colin reported before possible overflow and sign extension problems in
  io_provide_buffers_prep()
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  io_uring: fix overflows checks in provide buffers

  Colin reported before possible overflow and sign extension problems in
  io_provide_buffers_prep(). As Linus pointed ou…
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-120
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 5.8, < 5.10.37'
  - 'linux_kernel >= 5.11, < 5.11.21'
  - 'linux_kernel >= 5.12, < 5.12.4'
patched:
  - linux_kernel 5.12.4
published: '2024-02-28'
updated: '2026-08-04'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2021-47040'
references:
  - url: 'https://git.kernel.org/stable/c/38134ada0ceea3e848fe993263c0ff6207fd46e7'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/51bf90901952aaac564bbdb36b2b503050c53dd9'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/84b8c266c4bfe9ed5128e13253c388deb74b1b03'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/cbbc13b115b8f18e0a714d89f87fbdc499acfe2d'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/38134ada0ceea3e848fe993263c0ff6207fd46e7'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://git.kernel.org/stable/c/51bf90901952aaac564bbdb36b2b503050c53dd9'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://git.kernel.org/stable/c/84b8c266c4bfe9ed5128e13253c388deb74b1b03'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://git.kernel.org/stable/c/cbbc13b115b8f18e0a714d89f87fbdc499acfe2d'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.0026
epssPercentile: 0.15783
ingestedAt: '2026-08-04T10:39:39.508Z'
---

## Overview

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

io_uring: fix overflows checks in provide buffers

Colin reported before possible overflow and sign extension problems in
io_provide_buffers_prep(). As Linus pointed out previous attempt did nothing
useful, see d81269fecb8ce ("io_uring: fix provide_buffers sign extension").

Do that with help of check_<op>_overflow helpers. And fix struct
io_provide_buf::len type, as it doesn't make much sense to keep it
signed.

## Affected

- `linux_kernel >= 5.8, < 5.10.37`
- `linux_kernel >= 5.11, < 5.11.21`
- `linux_kernel >= 5.12, < 5.12.4`

## Remediation

Upgrade past the affected range:

- `linux_kernel 5.12.4`