CVE-2025-71083: Linux Kernel TTM NULL Pointer Vulnerability

CVE-2025-71083 Overview

CVE-2025-71083 is a null pointer dereference vulnerability in the Linux kernel's DRM/TTM (Translation Table Manager) subsystem. The vulnerability occurs when the devcoredump functionality attempts to read the contents of buffer objects (BOs) that have been evicted and are no longer associated with a resource. This can result in a kernel crash or denial of service condition when the system attempts to generate a coredump containing GPU buffer information.

Critical Impact

Systems with active GPU workloads using TTM-based memory management may experience kernel panics when devcoredump attempts to access evicted buffer objects, potentially causing system instability and denial of service.

Affected Products

• Linux Kernel (versions with DRM/TTM subsystem)
• Systems using TTM-based GPU drivers (AMD, Nouveau, VMware, etc.)
• Linux distributions with affected kernel versions

Discovery Timeline

• January 13, 2026 - CVE CVE-2025-71083 published to NVD
• January 13, 2026 - Last updated in NVD database

Technical Details for CVE-2025-71083

Vulnerability Analysis

The vulnerability resides in the Linux kernel's DRM/TTM memory management subsystem, specifically in the code path responsible for dumping buffer object contents during devcoredump operations. When a GPU driver triggers a coredump (typically after a GPU hang or error condition), the devcoredump mechanism iterates through all buffer objects to capture their contents for debugging purposes.

The flaw occurs because the code does not properly validate whether a buffer object is currently associated with a valid memory resource before attempting to access it. Buffer objects can exist in an evicted state where they have been temporarily removed from GPU-accessible memory but remain tracked by the TTM subsystem. When devcoredump encounters such an evicted BO with a NULL resource pointer and attempts to dereference it, a null pointer dereference occurs, resulting in a kernel oops or panic.

The fix implements proper validation to check for NULL resource pointers before attempting to access buffer contents. When an evicted BO is encountered, the code now records ENODATA instead of the buffer contents, gracefully handling the condition without crashing.

Root Cause

The root cause is a missing null pointer check in the devcoredump buffer reading logic within the DRM/TTM subsystem. The code assumed that all buffer objects being iterated would have a valid associated resource, failing to account for the legitimate scenario where BOs can exist without an associated resource due to memory pressure-induced eviction. This represents an improper input validation issue where the code did not validate the state of internal data structures before dereferencing pointers.

Attack Vector

This vulnerability is primarily a local denial of service vector. An attacker with local access to a system running a TTM-based GPU driver could potentially trigger the vulnerability by:

1. Causing heavy GPU memory pressure to force buffer object eviction
2. Triggering a GPU error condition that initiates a devcoredump
3. The combination of evicted BOs and coredump generation could cause a kernel crash

While the attack requires local access and specific conditions to trigger, it could be exploited to cause system instability or denial of service on workstation and server systems using affected GPU drivers.

Detection Methods for CVE-2025-71083

Indicators of Compromise

• Unexpected kernel panics or oops messages referencing the DRM/TTM subsystem
• Kernel log entries showing null pointer dereference in ttm_ prefixed functions
• System crashes occurring during GPU error recovery or coredump generation
• Increased frequency of GPU-related kernel errors followed by system reboots

Detection Strategies

• Monitor kernel logs (dmesg, /var/log/kern.log) for null pointer dereference messages in DRM/TTM code paths
• Implement kernel crash dump analysis to identify crashes originating from TTM buffer operations
• Use kernel tracing tools (ftrace, eBPF) to monitor devcoredump invocations on systems with TTM-based GPU drivers
• Deploy audit rules to track GPU driver error recovery events

Monitoring Recommendations

• Configure kdump or similar crash collection mechanisms to capture kernel crashes for analysis
• Enable kernel logging at appropriate verbosity levels for DRM subsystem messages
• Implement automated alerting for repeated kernel crashes on systems with GPU workloads
• Monitor system uptime metrics for anomalous reboot patterns on affected systems

How to Mitigate CVE-2025-71083

Immediate Actions Required

• Update to a patched Linux kernel version that includes the fix for this vulnerability
• Review kernel changelogs for your distribution to confirm the patch is included
• Prioritize patching on systems running GPU-intensive workloads or multi-tenant environments
• Consider temporarily disabling devcoredump functionality if patching is not immediately possible

Patch Information

The vulnerability has been addressed through multiple kernel commits across stable branches. The fix adds proper null pointer validation before accessing buffer object resources during devcoredump operations. When an evicted BO is encountered, the code now gracefully records ENODATA instead of attempting to read non-existent buffer contents.

Relevant kernel patches are available at:

• Kernel Git Commit 3d004f7341d4
• Kernel Git Commit 491adc6a0f99
• Kernel Git Commit 4b9944493c6d
• Kernel Git Commit 5a81095d3e1b
• Kernel Git Commit b94182b3d722

Workarounds

• Disable GPU coredump functionality if not required by adding appropriate kernel module parameters
• Implement resource limits on GPU memory usage to reduce eviction frequency
• Consider using kernel live patching solutions if immediate reboots are not feasible
• On non-critical systems, monitor and restart services rather than applying workarounds if patches can be deployed quickly

# Configuration example
# Temporarily disable GPU devcoredump (if supported by your driver)
# Check your specific GPU driver documentation for exact parameters

# For AMD GPU (amdgpu driver), you can disable GPU recovery which triggers coredumps
echo "options amdgpu gpu_recovery=0" >> /etc/modprobe.d/amdgpu.conf

# Rebuild initramfs after modprobe changes
update-initramfs -u

# Verify kernel version after patching
uname -r