CVE-2024-42317 is a vulnerability identified in the Linux kernel, specifically related to the handling of huge memory pages on ARM64 architectures with a base page size of 64KB. The issue arises from the Linux kernel's memory management subsystem, particularly within the 'mm/huge_memory' code that manages huge pages and the page cache. The vulnerability is due to the xarray data structure's inability to support arbitrary page cache sizes beyond a defined maximum (MAX_PAGECACHE_ORDER). However, on ARM64 systems with 64KB base page size, it is possible to have a 512MB page cache in the huge memory collapsing path, which exceeds this limitation. This discrepancy causes the kernel to raise warnings and potentially leads to unstable behavior or memory corruption during operations that involve splitting xarray entries, such as collapsing huge pages or truncating page cache ranges. The vulnerability manifests when a user-space process performs a sequence of memory management operations involving mmap, madvise with MADV_NOHUGEPAGE, MADV_POPULATE_READ, MADV_HUGEPAGE, and MADV_COLLAPSE, followed by file operations that punch holes in files (fallocate with FALLOC_FL_PUNCH_HOLE). This sequence triggers the kernel to split xarray entries improperly, leading to warnings and potential kernel instability. The kernel warning trace indicates the problem occurs in the function xas_split_alloc, which is critical for managing xarray entries representing page cache mappings. This vulnerability affects Linux kernel versions around 6.10.0-rc7 and likely other versions that share the same memory management implementation. It is specific to ARM64 systems with 64KB base page size, which is common in certain server and embedded environments. The vulnerability does not have a known exploit in the wild yet, and no CVSS score has been assigned. However, the underlying issue could lead to kernel crashes or memory corruption, which may be leveraged for denial of service or potentially privilege escalation if combined with other vulnerabilities.

For European organizations, the impact of CVE-2024-42317 depends largely on their deployment of ARM64-based Linux systems with 64KB base page size. Such systems are increasingly used in cloud infrastructure, edge computing, and specialized server environments. A successful exploitation could cause kernel panics or memory corruption, leading to denial of service conditions on critical servers or devices. This could disrupt business operations, especially for organizations relying on ARM64 hardware for virtualization, container orchestration, or high-performance computing. Although no direct exploit is known, the vulnerability could be a vector for attackers to destabilize systems or potentially escalate privileges if chained with other vulnerabilities. This risk is higher in environments where untrusted users or processes have the ability to perform the memory management operations described. The impact on confidentiality and integrity is indirect but possible if kernel memory corruption leads to unauthorized access or data leakage. Availability impact is more immediate due to potential system crashes. European organizations in sectors such as telecommunications, cloud service providers, research institutions, and government agencies that deploy ARM64 Linux servers should be particularly vigilant. The vulnerability could also affect embedded systems used in critical infrastructure, increasing the risk profile for industrial control systems and IoT deployments.

1. Apply Kernel Updates: Organizations should promptly apply Linux kernel patches that address this vulnerability once available from their Linux distribution vendors or upstream kernel sources. Monitoring vendor advisories for updated kernel packages is critical. 2. Restrict Access: Limit the ability of unprivileged users or processes to perform the specific sequence of memory management operations that trigger the vulnerability. This includes controlling access to mmap, madvise, and fallocate system calls through mandatory access controls (e.g., SELinux, AppArmor) or container runtime restrictions. 3. Hardware and Architecture Awareness: Identify and inventory ARM64 systems with 64KB base page size in the environment. Prioritize patching and monitoring on these systems as they are directly affected. 4. Monitoring and Logging: Enable detailed kernel logging and monitor for warning messages similar to those described (e.g., warnings from xas_split_alloc). Early detection of attempts to exploit or trigger the vulnerability can aid in incident response. 5. Limit Huge Page Usage: Where feasible, configure systems to limit or disable huge page collapsing features on affected ARM64 systems until patches are applied. 6. Test Updates in Staging: Due to the complexity of kernel memory management, test kernel updates in staging environments to ensure stability before wide deployment. 7. Incident Response Preparedness: Prepare for potential denial of service incidents by having recovery procedures and backups in place for affected systems.