CVE-2024-35985 is a vulnerability identified in the Linux kernel's scheduler component, specifically within the eevdf (Earliest Eligible Virtual Deadline First) scheduling class. The flaw arises in the function reweight_eevdf(), which is responsible for recalculating the scheduling weight (vlag) of entities (tasks or processes) in the scheduler. The vulnerability is due to a failure to properly limit the vlag value during computation, leading to a potential 64-bit signed integer multiplication overflow. This overflow causes the vruntime (virtual runtime) to be incorrectly calculated, which in turn causes the entity_eligible() function to return a false negative. As a result, the pick_eevdf() function may return NULL, leading to a NULL pointer dereference and subsequent kernel crash (kernel panic). This is a rare but fatal bug that can cause denial of service by crashing the Linux kernel. The root cause is the lack of bounds checking on vlag in reweight_eevdf(), unlike in update_entity_lag(), which properly limits vlag. The fix involves constraining vlag within safe limits to prevent overflow and ensure correct eligibility checks. This vulnerability affects Linux kernel versions identified by specific commits (hashes provided), and no known exploits are currently reported in the wild. The issue is critical because it impacts the core kernel scheduler, which is fundamental to system stability and process management.

For European organizations, this vulnerability poses a risk primarily in environments running vulnerable Linux kernel versions, especially in servers, cloud infrastructure, and embedded systems relying on the eevdf scheduler. A successful exploitation leads to a kernel crash, causing denial of service and potential disruption of critical services. This can impact availability of business-critical applications, cloud services, and network infrastructure. Organizations in sectors such as finance, healthcare, telecommunications, and government, which heavily depend on Linux-based systems, could face operational downtime and associated financial and reputational damage. Additionally, while no remote code execution or privilege escalation is indicated, the denial of service could be leveraged as part of a broader attack chain or to disrupt incident response activities. The rarity of the bug and the requirement for specific kernel versions limit the scope, but the severity of impact on system availability is significant.

To mitigate this vulnerability, European organizations should: 1) Identify and inventory Linux systems running affected kernel versions by checking kernel commit hashes or version numbers corresponding to the vulnerability. 2) Apply the official Linux kernel patches that address CVE-2024-35985 as soon as they become available from trusted sources such as the Linux kernel mailing list or vendor security advisories. 3) For systems where immediate patching is not feasible, consider temporarily disabling or avoiding the use of the eevdf scheduler if possible, or use alternative scheduling classes until patched. 4) Monitor system logs and kernel crash reports for signs of NULL pointer dereferences or unexpected kernel panics related to scheduling. 5) Implement robust kernel crash recovery mechanisms and maintain up-to-date backups to minimize downtime impact. 6) Engage with Linux distribution vendors for backported patches and security updates tailored to their supported kernel versions. 7) Incorporate this vulnerability into vulnerability management and incident response plans to ensure timely detection and remediation.