CVE-2026-68257 in Linux
Summary
by MITRE • 08/10/2026
In the Linux kernel, the following vulnerability has been resolved:
drm/amdkfd: fix 32-bit overflow in CWSR total size calculation
total_cwsr_size was computed in 32-bit before being used as a BO/SVM allocation size. With large ctx_save_restore_area_size and debug_memory_size multiplied by the XCC count, the product can wrap, yielding an undersized CWSR save area that firmware later overruns.
Promote total_cwsr_size to u64 and use check_add_overflow()/ check_mul_overflow() in both kfd_queue_acquire_buffers() and kfd_queue_release_buffers().
(cherry picked from commit 319f7e13423ae3f486b9aea82f9ad2d6af0ee608)
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 08/10/2026
The vulnerability in question affects the Linux kernel's graphics driver subsystem, specifically within the amdkfd component that manages AMD GPU compute operations. This issue stems from a critical 32-bit integer overflow that occurs during the calculation of CWSR (Compute Workgroup Save Restore) total size parameters. The flaw manifests when computing the total_cwsr_size variable which is initially calculated using 32-bit arithmetic before being utilized for buffer object and SVM (Shared Virtual Memory) allocation operations. When dealing with large context save restore area sizes combined with debug memory sizes multiplied by the XCC (Cross-Connect Cluster) count, the mathematical operations can cause integer wrapping behavior that results in significantly undersized CWSR save areas.
The technical implementation of this vulnerability exploits the fundamental limitations of 32-bit integer arithmetic within kernel space memory management operations. The total_cwsr_size calculation involves multiplying large values representing context save restore area sizes with debug memory sizes, then scaling by XCC counts that can exceed typical 32-bit capacity limits. When these multiplicative operations exceed the maximum value representable in 32 bits, the result wraps around to a much smaller positive value or negative number due to integer overflow behavior. This computed undersized value is then used as the allocation size for buffer objects and SVM regions, creating a scenario where firmware components attempt to write data beyond the allocated memory boundaries, leading to potential memory corruption and system instability.
The operational impact of this vulnerability extends beyond simple memory corruption to potentially enable privilege escalation and system compromise within graphics compute environments. When firmware overruns the undersized CWSR save area, it can overwrite adjacent memory regions including kernel data structures, function pointers, or other critical control information. This behavior aligns with common attack patterns described in the attack technique matrix where integer overflows serve as entry points for memory corruption exploits. The vulnerability specifically affects systems utilizing AMD GPUs with compute capabilities that rely on the amdkfd driver for managing compute workloads, making it particularly relevant to high-performance computing environments, machine learning workloads, and graphics-intensive applications that utilize GPU acceleration.
The fix implemented addresses this vulnerability through careful arithmetic type promotion and overflow checking mechanisms. The solution promotes the total_cwsr_size variable from 32-bit to 64-bit unsigned integer (u64) to accommodate larger calculations without overflow conditions. Additionally, the implementation incorporates explicit overflow detection using check_add_overflow() and check_mul_overflow() functions within both kfd_queue_acquire_buffers() and kfd_queue_release_buffers() functions. This approach follows established security practices for preventing integer overflows as recommended in common weakness enumeration standards such as CWE-190, which specifically addresses integer overflow conditions. The fix also includes cherry-picking the correction from a specific commit, indicating that this represents a well-tested solution that has been integrated into stable kernel releases, demonstrating adherence to proper vulnerability remediation practices.
The mitigation strategy relies on both architectural changes and defensive programming techniques that align with established security frameworks like MITRE ATT&CK's T1068 for local privilege escalation through kernel exploits. By promoting integer types and implementing explicit overflow checks, the solution prevents the wraparound conditions that previously enabled memory corruption scenarios. The implementation ensures that all arithmetic operations involving potentially large values are properly validated before being used in critical allocation operations, reducing the attack surface significantly. This approach also provides better error handling and prevents silent failures that could otherwise lead to more subtle security issues.
This vulnerability represents a classic example of how seemingly minor integer arithmetic issues can have severe security implications in kernel space operations. The fix demonstrates proper defensive programming practices including type safety improvements and explicit overflow detection, which are essential components of secure system design. The solution addresses the underlying root cause rather than merely masking symptoms, providing robust protection against similar classes of vulnerabilities in the graphics driver subsystem. The implementation follows industry best practices for kernel security hardening and represents a mature approach to vulnerability remediation that considers both immediate fixes and long-term maintainability.