{"id":"CVE-2025-40288","title":"In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/amdgpu: Fix NULL pointer dereference in VRAM logic for APU devices\n\nPreviously, APU platforms (and other scenarios with uninitialized VRAM managers)\ntriggered a NUL…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/amdgpu: Fix NULL pointer dereference in VRAM logic for APU devices\n\nPreviously, APU platforms (and other scenarios with uninitialized VRAM managers)\ntriggered a NUL…","severity":"none","published":"2025-12-06","updated":"2026-10-14","sourceUpdated":"2026-10-14T22:10:00.210","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2025-40288","references":[{"url":"https://git.kernel.org/stable/c/070bdce18fb12a49eb9c421e57df17d2ad29bf5f","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/1243e396148a65bb6c42a2b70fe43e50c16c494f","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/43aa61c18a3a45042b098b7a1186ffb29364002c","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/883f309add55060233bf11c1ea6947140372920f","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/e70113b741ba253886cd71dbadfe3ea444bb2f5c","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"tags":["nvd"],"epss":0.00186,"epssPercentile":0.07629,"ingestedAt":"2026-10-14T23:00:02.008Z","slug":"CVE-2025-40288","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\ndrm/amdgpu: Fix NULL pointer dereference in VRAM logic for APU devices\n\nPreviously, APU platforms (and other scenarios with uninitialized VRAM managers)\ntriggered a NULL pointer dereference in `ttm_resource_manager_usage()`. The root\ncause is not that the `struct ttm_resource_manager *man` pointer itself is NULL,\nbut that `man->bdev` (the backing device pointer within the manager) remains\nuninitialized (NULL) on APUs—since APUs lack dedicated VRAM and do not fully\nset up VRAM manager structures. When `ttm_resource_manager_usage()` attempts to\nacquire `man->bdev->lru_lock`, it dereferences the NULL `man->bdev`, leading to\na kernel OOPS.\n\n1. **amdgpu_cs.c**: Extend the existing bandwidth control check in\n   `amdgpu_cs_get_threshold_for_moves()` to include a check for\n   `ttm_resource_manager_used()`. If the manager is not used (uninitialized\n   `bdev`), return 0 for migration thresholds immediately—skipping VRAM-specific\n   logic that would trigger the NULL dereference.\n\n2. **amdgpu_kms.c**: Update the `AMDGPU_INFO_VRAM_USAGE` ioctl and memory info\n   reporting to use a conditional: if the manager is used, return the real VRAM\n   usage; otherwise, return 0. This avoids accessing `man->bdev` when it is\n   NULL.\n\n3. **amdgpu_virt.c**: Modify the vf2pf (virtual function to physical function)\n   data write path. Use `ttm_resource_manager_used()` to check validity: if the\n   manager is usable, calculate `fb_usage` from VRAM usage; otherwise, set\n   `fb_usage` to 0 (APUs have no discrete framebuffer to report).\n\nThis approach is more robust than APU-specific checks because it:\n- Works for all scenarios where the VRAM manager is uninitialized (not just APUs),\n- Aligns with TTM's design by using its native helper function,\n- Preserves correct behavior for discrete GPUs (which have fully initialized\n  `man->bdev` and pass the `ttm_resource_manager_used()` check).\n\nv4: use ttm_resource_manager_used(&adev->mman.vram_mgr.manager) instead of checking the adev->gmc.is_app_apu flag (Christian)\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}