---
id: CVE-2026-89742
title: 'rapidio: mport_cdev: fix use-after-free in dma_req_free()'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  rapidio: mport_cdev: fix use-after-free in dma_req_free()

  dma_req_free() acquires buf_mutex through req->map, drops the mapping
  reference with kref_put(), and then der…
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'
cvssSource: cna
cwe:
  - CWE-825
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= e8de370188d098bb49483c287b44925957c3c9b6 <
    00c5ed913b0dc563fbeb8a97ea8916c03bbbbf6a
  - >-
    Linux >= e8de370188d098bb49483c287b44925957c3c9b6 <
    fc79c07cdcde02c5b17633d78777de6ac2c14b29
  - >-
    Linux >= e8de370188d098bb49483c287b44925957c3c9b6 <
    26ccfe7d69e27b0d933ae0a64a23a0cb9b9a85a6
  - >-
    Linux >= e8de370188d098bb49483c287b44925957c3c9b6 <
    bd8881c24a9520f9c3d3e855d866197f63e471a7
  - >-
    Linux >= e8de370188d098bb49483c287b44925957c3c9b6 <
    9a9929ec875ff20922c90c96fd544ae8a2a61a8d
  - >-
    Linux >= e8de370188d098bb49483c287b44925957c3c9b6 <
    e6e925cc1f8067c65c7bec3da50a0ead3b3ef4e0
  - >-
    Linux >= e8de370188d098bb49483c287b44925957c3c9b6 <
    211c68d817a3d9dc14c0026a59da7cac30f8147e
  - >-
    Linux >= e8de370188d098bb49483c287b44925957c3c9b6 <
    5cbef379a94b161726c5f504598bf4791d45cedc
  - Linux 4.6
published: '2026-09-11'
updated: '2026-10-19'
sourceUpdated: '2026-10-19T08:51:56.183Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-89742'
references:
  - url: 'https://git.kernel.org/stable/c/00c5ed913b0dc563fbeb8a97ea8916c03bbbbf6a'
  - url: 'https://git.kernel.org/stable/c/fc79c07cdcde02c5b17633d78777de6ac2c14b29'
  - url: 'https://git.kernel.org/stable/c/26ccfe7d69e27b0d933ae0a64a23a0cb9b9a85a6'
  - url: 'https://git.kernel.org/stable/c/bd8881c24a9520f9c3d3e855d866197f63e471a7'
  - url: 'https://git.kernel.org/stable/c/9a9929ec875ff20922c90c96fd544ae8a2a61a8d'
  - url: 'https://git.kernel.org/stable/c/e6e925cc1f8067c65c7bec3da50a0ead3b3ef4e0'
  - url: 'https://git.kernel.org/stable/c/211c68d817a3d9dc14c0026a59da7cac30f8147e'
  - url: 'https://git.kernel.org/stable/c/5cbef379a94b161726c5f504598bf4791d45cedc'
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89742.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-89742'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2532155'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-89742'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89742'
  - url: >-
      https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89742.mbox
tags:
  - cve.org
  - csaf
  - vex
  - red-hat
  - score-dispute
epss: 0.00164
epssPercentile: 0.05552
scores:
  cna: 7.8
  vendor: 5.5
ingestedAt: '2026-09-14T15:23:07.449Z'
---

## Overview

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

rapidio: mport_cdev: fix use-after-free in dma_req_free()

dma_req_free() acquires buf_mutex through req->map, drops the mapping
reference with kref_put(), and then dereferences req->map again to unlock
the mutex.

If kref_put() drops the last reference, mport_release_mapping() frees the
mapping, and the subsequent mutex_unlock() dereferences a freed object. 
This is a use-after-free.

Fix this by caching map and md before kref_put(), clearing req->map while
holding buf_mutex, and using the cached md for mutex unlocking.

The bug is reachable from userspace via the RapidIO mport character device
interface.

## Affected

- `Linux >= e8de370188d098bb49483c287b44925957c3c9b6 < 00c5ed913b0dc563fbeb8a97ea8916c03bbbbf6a`
- `Linux >= e8de370188d098bb49483c287b44925957c3c9b6 < fc79c07cdcde02c5b17633d78777de6ac2c14b29`
- `Linux >= e8de370188d098bb49483c287b44925957c3c9b6 < 26ccfe7d69e27b0d933ae0a64a23a0cb9b9a85a6`
- `Linux >= e8de370188d098bb49483c287b44925957c3c9b6 < bd8881c24a9520f9c3d3e855d866197f63e471a7`
- `Linux >= e8de370188d098bb49483c287b44925957c3c9b6 < 9a9929ec875ff20922c90c96fd544ae8a2a61a8d`
- `Linux >= e8de370188d098bb49483c287b44925957c3c9b6 < e6e925cc1f8067c65c7bec3da50a0ead3b3ef4e0`
- `Linux >= e8de370188d098bb49483c287b44925957c3c9b6 < 211c68d817a3d9dc14c0026a59da7cac30f8147e`
- `Linux >= e8de370188d098bb49483c287b44925957c3c9b6 < 5cbef379a94b161726c5f504598bf4791d45cedc`
- `Linux 4.6`

## Remediation

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

## Vendor advisories

- **Red Hat VEX** · Moderate · updated 2026-09-21 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89742.json)