GHSA-5ppv-prh8-hj77

Опубликовано: 07 дек. 2025

Источник: github

Github: Не прошло ревью

Описание

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.

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-...

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

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

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-specific logic that would trigger the NULL dereference.
amdgpu_kms.c: Update the AMDGPU_INFO_VRAM_USAGE ioctl and memory info reporting to use a conditional: if the manager is used, return the real VRAM usage; otherwise, return 0. This avoids accessing man->bdev when it is NULL.
amdgpu_virt.c: Modify the vf2pf (virtual function to physical function) data write path. Use ttm_resource_manager_used() to check validity: if the manager is usable, calculate fb_usage from VRAM usage; otherwise, set fb_usage to 0 (APUs have no discrete framebuffer to report).

This approach is more robust than APU-specific checks because it:

Works for all scenarios where the VRAM manager is uninitialized (not just APUs),
Aligns with TTM's design by using its native helper function,
Preserves correct behavior for discrete GPUs (which have fully initialized man->bdev and pass the ttm_resource_manager_used() check).

v4: use ttm_resource_manager_used(&adev->mman.vram_mgr.manager) instead of checking the adev->gmc.is_app_apu flag (Christian)

Ссылки

EPSS

Процентиль: 14%

0.00045

Низкий

CVE ID

CVE-2025-40288

Связанные уязвимости

CVE-2025-40288

ubuntu

около 2 месяцев назад

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-specific log...