CVE-2026-89809 in Linux
摘要
由 MITRE • 2026-09-16
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)
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