CVE-2023-52932 is a vulnerability identified in the Linux kernel, specifically within the memory management subsystem related to swap file handling. The issue arises in the get_swap_pages() function, which is responsible for managing swap pages under memory pressure conditions. The vulnerability manifests as a softlockup—a state where a CPU core is stuck in a non-preemptible loop—caused by the absence of a conditional reschedule (cond_resched()) call within the get_swap_pages() function. Under extreme memory pressure, such as when using 64 CPU cores, 64GB of memory, and multiple zram devices configured with small disk sizes and equal priority to system memory, the function's internal loop (plist_for_each_entry_safe()) can iterate tens of thousands of times attempting to find available swap space. Without cond_resched(), this loop prevents the kernel scheduler from preempting the task, leading to a softlockup and frequent out-of-memory (OOM) conditions. The fix involves adding cond_resched() calls within get_swap_pages() to allow the scheduler to regain control and prevent the CPU from being locked in this loop. This vulnerability does not appear to have known exploits in the wild and does not have an assigned CVSS score yet. It primarily affects Linux kernel versions identified by the commit hash 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and similar builds. The issue is triggered under very specific high-memory pressure scenarios, often involving stress testing tools like stress-ng and configurations with multiple zram devices.

For European organizations relying on Linux-based systems, particularly those running high-performance computing environments, large-scale servers, or systems with complex memory configurations (e.g., multiple zram devices), this vulnerability could lead to system instability and denial of service due to softlockups and frequent OOM events. This can disrupt critical services, degrade performance, and potentially cause downtime. Organizations using Linux in cloud infrastructure, data centers, or embedded systems with constrained memory resources are at risk of encountering these issues under heavy load. While the vulnerability does not directly lead to privilege escalation or data breaches, the availability impact can be significant, especially for sectors requiring high uptime such as finance, healthcare, telecommunications, and public services. The lack of known exploits reduces immediate risk, but unpatched systems under heavy memory pressure remain vulnerable to operational disruptions.

To mitigate this vulnerability, European organizations should prioritize updating their Linux kernels to versions that include the patch adding cond_resched() calls in get_swap_pages(). Kernel updates should be tested and deployed promptly, especially on systems with high memory usage or multiple zram devices. Additionally, organizations should monitor system logs for softlockup warnings and OOM events to detect potential exploitation of this issue. Configurations that create extreme memory pressure, such as stress testing or unusual zram setups, should be reviewed and adjusted to avoid triggering the vulnerability. Implementing resource limits and memory pressure monitoring can help prevent conditions that lead to softlockups. For critical systems, consider isolating workloads to reduce memory contention and using kernel tuning parameters to optimize swap and memory management behavior. Finally, maintain regular backups and ensure incident response plans include procedures for addressing kernel-level availability issues.