CVE-2025-71294: Linux Kernel Buffer Overflow Vulnerability

CVE-2025-71294 Overview

CVE-2025-71294 is a NULL pointer dereference vulnerability in the Linux kernel's drm/amdgpu driver. The flaw occurs when the System DMA (SDMA) block is not enabled, leaving buffer_funcs uninitialized. Code paths that subsequently dereference buffer_funcs trigger a NULL pointer access, leading to a kernel oops or system crash.

The issue affects systems running AMD GPUs with the amdgpu driver loaded under configurations where SDMA initialization is skipped. Upstream maintainers have merged fixes across multiple stable branches.

Critical Impact

A NULL pointer dereference in the amdgpu driver can crash the kernel, causing denial of service on affected Linux systems using AMD graphics hardware.

Affected Products

• Linux kernel (mainline) with drm/amdgpu driver
• Linux stable kernel branches receiving the backport (multiple commits referenced)
• Systems using AMD GPUs where the SDMA block is not enabled

Discovery Timeline

• 2026-05-06 - CVE-2025-71294 published to NVD
• 2026-05-06 - Last updated in NVD database

Technical Details for CVE-2025-71294

Vulnerability Analysis

The vulnerability resides in the AMD GPU Direct Rendering Manager (DRM) driver (drm/amdgpu) in the Linux kernel. The driver exposes a buffer_funcs operations structure used for buffer management routines such as memory copies and fills between GPU buffers.

Under normal initialization, the SDMA block populates buffer_funcs with valid function pointers. When the SDMA block is disabled or fails to initialize, this structure remains NULL. Subsequent calls into buffer management code dereference the uninitialized pointer, producing a kernel NULL pointer dereference.

This class of bug is tracked as a Null Pointer Dereference and typically results in denial of service rather than memory corruption or privilege escalation.

Root Cause

The root cause is missing validation of buffer_funcs before use. The driver assumes SDMA is always enabled and that buffer_funcs is always populated. When SDMA is not enabled — for example on configurations where the SDMA block is disabled by firmware or platform policy — this assumption is violated.

The upstream patches add explicit checks before dereferencing buffer_funcs, ensuring the pointer is valid prior to invoking buffer operations.

Attack Vector

The vulnerability requires local access to a system running an affected kernel with an AMD GPU. Triggering the path that dereferences buffer_funcs typically requires interaction with the GPU subsystem through standard DRM interfaces. The EPSS score of 0.018% (percentile 4.678) indicates very low predicted exploitation likelihood, consistent with a denial-of-service-class issue.

No public proof-of-concept or exploitation in the wild has been reported. The flaw is not listed in the CISA Known Exploited Vulnerabilities catalog.

The vulnerability is described in prose only; no verified exploitation code is available. Refer to the upstream commits for technical fix details: 276028fd9b60, 29fd416e0e08, 3e849a93bff4, and 9877a865d62c.

Detection Methods for CVE-2025-71294

Indicators of Compromise

• Kernel oops or panic messages referencing amdgpu and buffer_funcs in dmesg or /var/log/kern.log
• Stack traces showing NULL pointer dereference originating from drm/amdgpu buffer management routines
• Unexpected GPU subsystem failures or display resets on systems where SDMA is not enabled

Detection Strategies

• Inventory Linux hosts with AMD GPUs and identify running kernel versions to confirm whether the patched commits are present
• Monitor kernel ring buffer logs for BUG: kernel NULL pointer dereference entries containing amdgpu symbols
• Correlate GPU-related crash signatures with hardware configurations where the SDMA block is disabled

Monitoring Recommendations

• Forward kernel logs to a centralized logging or SIEM platform and alert on repeated amdgpu fault patterns
• Track kernel version drift across the fleet to detect hosts running unpatched stable branches
• Review crash dumps from affected systems to confirm whether the NULL pointer site matches the buffer_funcs code path

How to Mitigate CVE-2025-71294

Immediate Actions Required

• Update affected Linux systems to a kernel build that includes one of the upstream fix commits referenced by the CVE
• Prioritize patching on systems where AMD GPUs are deployed and SDMA is known to be disabled or selectively enabled
• Restrict local access to multi-user systems running unpatched kernels until the update is applied

Patch Information

Fixes have been merged to multiple stable branches via commits 276028fd9b60, 29fd416e0e08, 3e849a93bff4, and 9877a865d62c. The patches add validation to ensure buffer_funcs is initialized before it is dereferenced. Apply the kernel update from your Linux distribution that incorporates these commits, then reboot to load the patched kernel.

Workarounds

• Where feasible, ensure the SDMA block is enabled in firmware and platform configuration so buffer_funcs is initialized through the normal path
• Avoid loading the amdgpu driver on systems that do not require AMD GPU acceleration if a kernel update cannot be applied immediately
• Limit unprivileged user access to GPU device nodes (/dev/dri/*) on affected hosts until patched

# Check current kernel version and confirm vendor patch level
uname -r

# Inspect kernel logs for the NULL pointer signature in amdgpu
dmesg | grep -iE 'amdgpu|buffer_funcs|NULL pointer'

# Apply distribution kernel updates (Debian/Ubuntu)
sudo apt update && sudo apt install --only-upgrade linux-image-generic
sudo reboot

# Apply distribution kernel updates (RHEL/Fedora)
sudo dnf update kernel
sudo reboot