CVE-2022-48897 is a vulnerability identified in the Linux kernel specifically affecting the arm64 architecture's memory management subsystem. The issue arises from an incorrect handling of page table entries when splitting hugepages, which are large memory pages used to optimize memory management and performance. The vulnerability is rooted in the function pmd_leaf() returning true even if the Page Middle Directory (PMD) entry is invalid, due to the pmd_present_invalid() check. This causes an imbalance in the file_map_count reference counter during the invalidation and setting of page table entries. Specifically, in the pmdp_invalidate() function, the file_map_count is both decreased and then increased erroneously, and subsequently increased again in set_pte_at(). This leads to an unexpected BUG_ON() kernel panic triggered by the page_table_check() mechanism, which is designed to catch inconsistencies in page table entries. The kernel panic manifests as an internal error (Oops) and can cause system instability or crashes. The root cause is a missing check for !pmd_present_invalid() in the pmd_user_accessible_page() function, which was added to fix the problem. This vulnerability affects Linux kernel versions prior to the fix and is particularly relevant for systems running on arm64 processors that utilize hugepages. No known exploits are reported in the wild as of the publication date, and no CVSS score has been assigned yet. The vulnerability is technical and low-level, involving kernel memory management internals and page table handling, which are critical for system stability and security.

For European organizations, the impact of CVE-2022-48897 primarily concerns systems running Linux on arm64 architectures, which are increasingly common in cloud environments, edge computing, and IoT devices. A kernel panic caused by this vulnerability can lead to denial of service (DoS) conditions, resulting in system crashes and downtime. This can disrupt critical services, especially in sectors relying on high availability such as finance, healthcare, telecommunications, and industrial control systems. Although no direct remote code execution or privilege escalation is indicated, the instability can be exploited indirectly by attackers to cause service interruptions or to facilitate further attacks during recovery phases. Organizations using arm64-based Linux servers or embedded devices must be aware that this vulnerability affects kernel memory management and could compromise system reliability. The lack of known exploits suggests a lower immediate threat, but the potential for DoS and system crashes makes timely patching important to maintain operational continuity and security posture.

To mitigate CVE-2022-48897, organizations should: 1) Apply the official Linux kernel patches that include the fix adding the !pmd_present_invalid() check in pmd_user_accessible_page(). This is the definitive resolution to prevent the incorrect file_map_count manipulation and kernel panics. 2) For systems where immediate patching is not feasible, consider disabling hugepage usage on affected arm64 systems as a temporary workaround, although this may impact performance. 3) Monitor kernel logs for BUG_ON() triggers or Oops messages related to page_table_check to detect potential exploitation or system instability. 4) Implement robust system monitoring and automated reboot mechanisms to minimize downtime in case of kernel panics. 5) Ensure that system firmware and bootloaders are up to date to support kernel updates and maintain system integrity. 6) Coordinate with Linux distribution vendors for timely updates and backports, especially for enterprise and embedded Linux distributions common in European infrastructure.