CVE-2024-56613 is a vulnerability identified in the Linux kernel's scheduler NUMA (Non-Uniform Memory Access) subsystem, specifically related to a memory leak caused by improper handling of the vma->numab_state pointer. The issue arises when multiple threads concurrently access a shared virtual memory area (VMA) structure, leading to a race condition where the vma->numab_state pointer can be overwritten or improperly allocated. This results in a memory leak detectable by the kernel memory leak detector (kmemleak) when running multi-threaded workloads such as the hackbench program from the Linux Test Project (LTP). The problem manifests under high concurrency scenarios with many threads (e.g., 20 threads creating 800 tasks), particularly on high-core-count servers (192, 256, and 448 cores tested). The root cause is that multiple cores simultaneously observe vma->numab_state as NULL and attempt to allocate or overwrite it without proper atomic synchronization. Although the kernel attempts to limit scanning to one thread per NUMA scan period, the timing allows another thread to enter before the allocation completes, causing the race. The vulnerability does not appear when using multiple processes instead of threads, indicating the issue is specific to thread concurrency and shared memory structures. The fix involves using an atomic compare-and-exchange (cmpxchg) operation to ensure only one thread performs the assignment to vma->numab_state, preventing concurrent overwrites and eliminating the memory leak. This patch ensures thread-safe updates to the NUMA state within the scheduler. No known exploits are reported in the wild, and the vulnerability primarily causes resource leakage rather than direct code execution or privilege escalation. However, memory leaks in kernel space can degrade system stability and performance, especially on large-scale, high-core-count servers running intensive multi-threaded workloads.

For European organizations, the impact of CVE-2024-56613 depends largely on their use of Linux servers, particularly those with high core counts running multi-threaded applications or workloads similar to hackbench. The vulnerability leads to memory leaks in the kernel scheduler's NUMA subsystem, which can cause gradual degradation of system performance and stability due to unreclaimed memory. This may result in increased system crashes, degraded throughput, or unexpected behavior in critical infrastructure relying on Linux servers. Organizations operating data centers, cloud services, or HPC (High Performance Computing) clusters with Linux kernels vulnerable to this issue could experience reduced reliability and increased maintenance overhead. Although this vulnerability does not directly enable remote code execution or privilege escalation, the indirect effects on availability and system health can impact service continuity and operational efficiency. Given the prevalence of Linux in European enterprise and public sector IT environments, especially in industries such as finance, telecommunications, and research institutions, the vulnerability poses a moderate risk. Systems running older or unpatched Linux kernels with high concurrency workloads are most at risk. The lack of known exploits reduces immediate threat, but the vulnerability should be addressed promptly to avoid potential stability issues and to maintain compliance with security best practices.

1. Apply the official Linux kernel patch that uses the atomic cmpxchg operation to safely assign vma->numab_state, eliminating the race condition and memory leak. Ensure all Linux servers, especially those with high core counts and multi-threaded workloads, are updated to a kernel version containing this fix. 2. For environments where immediate patching is not feasible, monitor kernel memory leak reports via kmemleak or similar tools to detect signs of this vulnerability manifesting. 3. Limit the use of high concurrency multi-threaded workloads that stress the NUMA scheduler until patches are applied. Consider using multi-process workloads as a temporary workaround, since the issue does not reproduce with multiple processes. 4. Implement rigorous testing of kernel updates in staging environments that replicate production concurrency levels to verify the fix and avoid regressions. 5. Maintain up-to-date kernel versions and subscribe to Linux kernel security advisories to promptly respond to similar concurrency-related vulnerabilities. 6. For critical systems, consider deploying kernel live patching solutions that can apply fixes without requiring full system reboots, minimizing downtime. 7. Review system monitoring and alerting to detect early signs of memory leaks or performance degradation related to kernel memory management.