---
cve: "CVE-2026-89809"
severity: "LOW"
cvss: 3.1
epss: "2.5%"
vendor: "Linux"
kev: false
exploited: false
published: "2026-09-16 11:16:46"
tags: [cve, security, low]
source: tsecurity.de CVE-Dossier
exported: "2026-09-18T07:48:11+02:00"
---

# CVE-2026-89809

> 3.1 LOW

## Beschreibung

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)

## Patch verfügbar (OSV)

- Kernel ≥ 7.2.5

## Referenzen

- <https://git.kernel.org/stable/c/58e866711b234571b0ce342c43d153a4786b32b8>
- <https://git.kernel.org/stable/c/012a026bae0212952b423a842b7e2c0bf21f8e7a>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-89809) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_