CVE-2026-89809 drm/amdkfd: fix scope of mqd_mgr dereference in pqm_debugfs_mqds
A local attacker can cause a kernel crash by reading a debugfs file while a KFD queue is active, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-89809?
CVE-2026-89809 is a vulnerability in Linux, published on 16 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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)
Which versions are affected by CVE-2026-89809?
How do I fix CVE-2026-89809?
Apply the vendor's patch.
Is CVE-2026-89809 being exploited?
There is no known exploitation of CVE-2026-89809 in the wild and no public exploit code.
Sources
Also known as AZL-101625, DEBIAN-CVE-2026-89809, GHSA-634r-724x-3g6w, UBUNTU-CVE-2026-89809.