CVE-2023-52490 is a medium-severity vulnerability in the Linux kernel related to the memory management subsystem, specifically the page migration mechanism. The flaw arises during concurrent operations involving page migration and memory hotplugging, as observed under stress-ng testing. The vulnerability manifests as a kernel crash triggered by a NULL pointer dereference at virtual address 0x0, caused by incorrect handling of the target page's mapping field during migration. In detail, when one thread migrates a page, it temporarily stores an 'anon_vma' pointer in the target page's ->mapping field without setting the PAGE_MAPPING_ANON flag. Concurrently, another thread performing memory hotplug attempts to offline the same page. The page's reference count is 1, preventing offlining but leading to a page dump operation. During this dump, the kernel calls page_mapping() on the target page, which returns an incorrect file mapping due to the missing PAGE_MAPPING_ANON flag, causing a NULL pointer dereference and kernel panic. The root cause is the misuse of the ->mapping field to store anon_vma without proper flagging, confusing PFN walkers and compaction routines that call page_mapping() without holding the page lock. The fix chosen involves using the target page's ->private field to store the anon_vma pointer and page state bits, isolating this temporary state from the ->mapping field and preventing incorrect mapping returns. This approach avoids confusing PFN walkers and improves stability during page migration and memory hotplug operations. The vulnerability is rated with a CVSS 3.1 score of 5.5 (medium), with an attack vector of local access, low complexity, requiring privileges but no user interaction, and impacts availability by causing kernel crashes. No known exploits are reported in the wild at this time.

For European organizations, this vulnerability poses a risk primarily to systems running vulnerable Linux kernel versions, especially those utilizing memory hotplug features or running workloads that stress page migration, such as high-performance computing, virtualization hosts, or cloud infrastructure. The impact is a denial of service via kernel crashes, potentially causing system outages, data loss, or service interruptions. Critical infrastructure, data centers, and cloud service providers in Europe relying on affected Linux kernels could experience operational disruptions. Although the vulnerability does not directly compromise confidentiality or integrity, the availability impact can affect business continuity and service reliability. Systems with high uptime requirements or those running containerized or virtualized environments may be particularly sensitive. The absence of known exploits reduces immediate risk, but the vulnerability's medium severity and kernel-level impact warrant prompt attention to avoid potential exploitation or accidental crashes in production environments.

European organizations should implement the following specific mitigations: 1) Identify and inventory Linux systems running affected kernel versions, particularly those involved in memory hotplug or heavy memory migration workloads. 2) Apply the official Linux kernel patches that implement the fix using the ->private field for anon_vma storage as soon as they become available from trusted Linux distributions or kernel maintainers. 3) For systems where immediate patching is not feasible, consider disabling memory hotplug features or workloads that trigger frequent page migration to reduce exposure. 4) Monitor kernel logs for signs of page migration or memory hotplug related errors or crashes to detect potential exploitation or instability. 5) Employ robust system monitoring and automated recovery mechanisms to minimize downtime in case of kernel crashes. 6) Coordinate with Linux distribution vendors for timely updates and backports, especially for long-term support kernels common in enterprise environments. 7) Conduct controlled stress testing in staging environments to validate stability post-patching before production deployment. These steps go beyond generic advice by focusing on workload characteristics and kernel feature usage that influence exposure to this vulnerability.