CVE-2025-40288

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

drm/amdgpu: Fix NULL pointer dereference in VRAM logic for APU devices

Previously, APU platforms (and other scenarios with uninitialized VRAM managers)

triggered a NULL pointer dereference in `ttm_resource_manager_usage()`. The root

cause is not that the `struct ttm_resource_manager *man` pointer itself is NULL,

but that `man->bdev` (the backing device pointer within the manager) remains

uninitialized (NULL) on APUs—since APUs lack dedicated VRAM and do not fully

set up VRAM manager structures. When `ttm_resource_manager_usage()` attempts to

acquire `man->bdev->lru_lock`, it dereferences the NULL `man->bdev`, leading to

a kernel OOPS.

1. **amdgpu_cs.c**: Extend the existing bandwidth control check in

`amdgpu_cs_get_threshold_for_moves()` to include a check for

`ttm_resource_manager_used()`. If the manager is not used (uninitialized

`bdev`), return 0 for migration thresholds immediately—skipping VRAM-specifi

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References