cbcvebase.
CVE-2025-40288
published 2025-12-06

CVE-2025-40288: In the Linux kernel, the following vulnerability has been resolved: drm/amdgpu: Fix NULL pointer dereference in VRAM logic for APU devices Previously, APU…

PriorityP424high7.8
EPSS
0.18%
8.1th percentile
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 logic that would trigger the NULL dereference. 2. **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. 3. **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 ch

Affected

21 ranges
VendorProductVersion rangeFixed in
debianlinux< linux 6.1.159-1 (bookworm)linux 6.1.159-1 (bookworm)
debianlinux-6.1< linux 6.1.159-1 (bookworm)linux 6.1.159-1 (bookworm)
linuxlinux
linuxlinux>= d38ceaf99ed015f2a0b9af3499791bd3a3daae21 < e70113b741ba253886cd71dbadfe3ea444bb2f5ce70113b741ba253886cd71dbadfe3ea444bb2f5c
linuxlinux>= d38ceaf99ed015f2a0b9af3499791bd3a3daae21 < 1243e396148a65bb6c42a2b70fe43e50c16c494f1243e396148a65bb6c42a2b70fe43e50c16c494f
linuxlinux>= d38ceaf99ed015f2a0b9af3499791bd3a3daae21 < 43aa61c18a3a45042b098b7a1186ffb29364002c43aa61c18a3a45042b098b7a1186ffb29364002c
linuxlinux>= d38ceaf99ed015f2a0b9af3499791bd3a3daae21 < 070bdce18fb12a49eb9c421e57df17d2ad29bf5f070bdce18fb12a49eb9c421e57df17d2ad29bf5f
linuxlinux>= d38ceaf99ed015f2a0b9af3499791bd3a3daae21 < 883f309add55060233bf11c1ea6947140372920f883f309add55060233bf11c1ea6947140372920f
linuxlinux_kernel>= 0 < 6.1.159-16.1.159-1
linuxlinux_kernel>= 0 < 6.12.63-16.12.63-1
linuxlinux_kernel>= 0 < 6.17.9-16.17.9-1
linuxlinux_kernel>= 0 < 6.8.0-106.1066.8.0-106.106
linuxlinux_kernel>= 0 < 6.17.0-14.146.17.0-14.14
linuxlinux_kernel>= 4.2.0 < 6.1.1596.1.159
linuxlinux_kernel>= 6.13.0 < 6.17.96.17.9
linuxlinux_kernel>= 6.2.0 < 6.6.1176.6.117
linuxlinux_kernel>= 6.7.0 < 6.12.596.12.59
msrcazl3_kernel_6.6.112.1-2_on_azure_linux_3.0
ubuntulinux-aws
ubuntulinux-oracle
ubuntulinux-xilinx

CVSS provenance

vendor_ubuntu7.8HIGH
osv3.2LOW
vendor_msrc4.7MEDIUM
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