# CVE-2026-89809: drm/amdkfd: fix scope of mqd_mgr dereference in pqm_debugfs_mqds

CVE-2026-89809 is fixed in linux on 1 platform by DEBIAN-CVE-2026-89809 (version 7.2.6-1), released September 23, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-89809
- Priority: Routine
- CVSS: 5.5 (Moderate)
- EPSS: 0.0020
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 16, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-89809

## Description

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)

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 14 | 7.2.6-1 | [DEBIAN-CVE-2026-89809](https://patchblox.com/security/data/fix/linux/debian-cve-2026-89809.md) | Sep 23, 2026 |

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