---
id: CVE-2026-89809
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  drm/amdkfd: fix scope of mqd_mgr dereference in pqm_debugfs_mqds

  Reading /sys/kernel/debug/kfd/mqds while a process holds an active KFD
  queue triggers a NULL pointer d…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  drm/amdkfd: fix scope of mqd_mgr dereference in pqm_debugfs_mqds

  Reading /sys/kernel/debug/kfd/mqds while a process holds an active KFD
  queue triggers a NULL pointer d…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    58e866711b234571b0ce342c43d153a4786b32b8
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    012a026bae0212952b423a842b7e2c0bf21f8e7a
  - Linux < 7.2.5
  - Linux (all versions)
published: '2026-09-16'
updated: '2026-09-17'
sourceUpdated: '2026-09-17T10:17:04.047'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89809'
references:
  - url: 'https://git.kernel.org/stable/c/012a026bae0212952b423a842b7e2c0bf21f8e7a'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/58e866711b234571b0ce342c43d153a4786b32b8'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-16T10:53:54.006Z'
epss: 0.00189
epssPercentile: 0.08818
---

## Overview

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

drm/amdkfd: fix scope of mqd_mgr dereference in pqm_debugfs_mqds

Reading /sys/kernel/debug/kfd/mqds while a process holds an active KFD
queue triggers a NULL pointer dereference because the for loop that
calls mqd_mgr->debugfs_show_mqd() is incorrectly placed outside the
if (pqn->q) block that initializes mqd_mgr.

The queue list can contain entries where pqn->q is NULL (kernel queues
where only pqn->kq is valid). In the original code:

  if (pqn->q) {
      ...
      mqd_mgr = q->device->dqm->mqd_mgrs[mqd_type];
      size = mqd_mgr->mqd_stride(...);
  }

  for (xcc = 0; xcc < num_xccs; xcc++) {  // WRONG: outside if block
      mqd = q->mqd + size * xcc;
      r = mqd_mgr->debugfs_show_mqd(m, mqd);
  }

When iterating over a queue node where pqn->q is NULL:
1. The if (pqn->q) block is skipped
2. mqd_mgr remains uninitialized (NULL from declaration)
3. The for loop executes anyway
4. mqd_mgr->debugfs_show_mqd(m, mqd) dereferences NULL

The crash manifests as:

  BUG: kernel NULL pointer dereference, address: 0000000000000000
  #PF: supervisor instruction fetch in kernel mode
  RIP: 0010:0x0
  Call Trace:
   pqm_debugfs_mqds+0x10c/0x1d0 [amdgpu]
   kfd_debugfs_mqds_by_process+0x9b/0x110 [amdgpu]
   seq_read_iter+0x132/0x4b0
   ...

Fix by moving the for loop inside the if (pqn->q) block, so mqd_mgr
and related variables are only used when properly initialized.

(cherry picked from commit 8bfe29d5c798940f797aa24135d2734c3ffce9de)

## Remediation

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