CVE-2024-56583 is a vulnerability identified in the Linux kernel scheduler's deadline scheduling subsystem, specifically within the function migrate_enable related to boosted tasks. The issue arises when tasks that have been priority-boosted (e.g., via real-time mutex priority inheritance mechanisms) are requeued during CPU affinity changes using set_cpus_allowed. The Linux kernel scheduler uses deadline scheduling to manage task execution with timing constraints. When set_cpus_allowed is called, it dequeues and enqueues tasks with the ENQUEUE_RESTORE flag. However, if the task is already boosted, the scheduler attempts to call setup_new_dl_entity again unnecessarily, triggering a kernel warning (WARN_ON). This warning indicates a potential logic flaw where the scheduler tries to reinitialize scheduling parameters for a task that already has them set, which could lead to instability or unexpected behavior. The vulnerability does not appear to be exploitable for privilege escalation or arbitrary code execution but may cause kernel warnings and potentially impact system stability under specific workloads that heavily use CPU affinity changes and real-time priority boosting. The patch involves adding a check to avoid calling setup_new_dl_entity for tasks that are already boosted, preventing the warning and ensuring correct scheduler behavior. This vulnerability was discovered through stress testing using the stress-ng tool with cyclic CPU load and affinity changes, which triggered the warning consistently. No known exploits are reported in the wild, and no CVSS score has been assigned yet.

For European organizations, the impact of CVE-2024-56583 is primarily related to system stability and reliability rather than direct security compromise. Organizations running Linux servers or embedded systems with real-time workloads or those that frequently modify CPU affinity for tasks (e.g., high-performance computing, telecommunications, industrial control systems) may experience kernel warnings or potential scheduler anomalies. This could lead to degraded performance, unexpected task scheduling delays, or in rare cases, system crashes if the scheduler's internal state becomes inconsistent. While this does not directly expose sensitive data or allow unauthorized access, the operational disruption could affect critical infrastructure, especially in sectors relying on Linux-based real-time systems such as manufacturing, energy, and telecommunications prevalent in Europe. Systems running older or unpatched Linux kernels are at risk until updated. The lack of known exploits reduces immediate threat but does not eliminate the risk of future exploitation or stability issues.

European organizations should prioritize updating Linux kernels to versions that include the fix for CVE-2024-56583 as soon as patches become available from their Linux distribution vendors. Specifically, kernel maintainers have addressed this by adding logic to detect boosted tasks and avoid redundant setup calls in the scheduler. Until patches are applied, organizations should monitor kernel logs for warnings related to sched/deadline and migrate_enable, especially on systems running workloads that stress CPU affinity and real-time scheduling. Reducing or avoiding frequent CPU affinity changes on boosted tasks can mitigate triggering the warning. For critical real-time systems, thorough testing under load with stress-ng or similar tools can help identify if the issue manifests. Additionally, organizations should ensure robust kernel crash dump and monitoring infrastructure to quickly detect and respond to any stability issues. Coordination with Linux distribution vendors and timely patch management processes are essential to minimize exposure.