CVE-2026-89809

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)