Linux Kernel up to 7.2.4/7.3-rc1 amdkfd mqds pqm_debugfs_mqds pqn null pointer dereference

Summaryinfo

A vulnerability has been found in Linux Kernel up to 7.2.4/7.3-rc1 and classified as problematic. Affected by this vulnerability is the function pqm_debugfs_mqds of the file /sys/kernel/debug/kfd/mqds of the component amdkfd. This manipulation of the argument pqn causes null pointer dereference. This vulnerability is registered as CVE-2026-89809. The attack needs to be launched locally. No exploit is available. The affected component should be upgraded.

Detailsinfo

A vulnerability has been found in Linux Kernel up to 7.2.4/7.3-rc1 and classified as problematic. Affected by this vulnerability is the function pqm_debugfs_mqds of the file /sys/kernel/debug/kfd/mqds of the component amdkfd. The manipulation of the argument pqn with an unknown input leads to a null pointer dereference vulnerability. The CWE definition for the vulnerability is CWE-476. A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit. As an impact it is known to affect availability. The summary by CVE is:

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)

The advisory is shared at git.kernel.org. This vulnerability is known as CVE-2026-89809 since 09/11/2026. The exploitation appears to be easy. An attack has to be approached locally. The exploitation requires an enhanced level of successful authentication. Technical details are known, but no exploit is available.

Upgrading to version 7.2.5 or 7.3-rc2 eliminates this vulnerability. Applying the patch 58e866711b234571b0ce342c43d153a4786b32b8/012a026bae0212952b423a842b7e2c0bf21f8e7a is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 7.2.0
• 7.2.1
• 7.2.2
• 7.2.3
• 7.2.4
• 7.3-rc1

License

• open-source

Website

• Vendor: https://www.kernel.org/

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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