CVE-2024-56779 is a vulnerability identified in the Linux kernel's NFS server daemon (nfsd) related to the handling of concurrent NFSv4 open operations. The flaw arises when multiple rpc_task instances are generated simultaneously by the NFS client attempting to open the same file, while the server's nfsd processes concurrently handle these requests. Specifically, when an NFS client issues an open request, the server attempts to find or allocate an nfs4_openowner structure representing the open owner state. If an nfs4_openowner is found but not marked as confirmed (NFS4_OO_CONFIRMED), it is released and unhashed. However, due to concurrency, two rpc_task instances can cause the server to allocate multiple nfs4_openowner objects for the same client state, leading to memory leaks because the released openowner is not properly cleaned up or found during client destruction. Additionally, forced unmount operations (umount -f) on the client side attempt to kill all rpc_task instances, which can cause one rpc_task to return early with an error (-512), while another rpc_task continues processing, exacerbating the race condition and memory leak. The leak affects multiple kernel memory caches including nfsd_file and nfsd_file_mark slabs, resulting in objects remaining allocated even during shutdown, which can degrade system stability and performance over time. The vulnerability does not appear to require authentication or user interaction beyond normal NFS client operations, and it can be triggered by legitimate concurrent file open requests. No known exploits are reported in the wild yet, and no CVSS score has been assigned. The issue was fixed in Linux kernel version 6.12.0-rc6+ and involves complex interactions between client-side forced unmounts and server-side openowner state management.

For European organizations, the impact of CVE-2024-56779 can be significant, especially for those relying heavily on NFSv4 for file sharing and storage services in enterprise environments. Memory leaks in the NFS server daemon can lead to gradual resource exhaustion, causing degraded performance, increased latency, and potential denial of service (DoS) conditions on critical file servers. This can disrupt business operations, data availability, and workflows dependent on shared file systems. Organizations using Linux-based NFS servers in data centers, cloud infrastructure, or network-attached storage appliances are particularly at risk. The vulnerability could also complicate maintenance and recovery procedures due to instability during forced unmount operations. While exploitation does not appear to allow privilege escalation or direct data corruption, the resulting DoS and system instability can indirectly impact confidentiality and integrity by forcing emergency shutdowns or failovers. Given the widespread use of Linux in European public sector, financial institutions, and technology companies, the vulnerability poses a moderate to high operational risk if left unpatched.

To mitigate CVE-2024-56779, European organizations should: 1) Immediately update Linux kernel versions to 6.12.0-rc6+ or later where the fix is applied. 2) Audit and monitor NFS server logs and memory usage patterns to detect abnormal resource consumption indicative of memory leaks. 3) Avoid forced unmount operations (umount -f) on NFS mounts during high concurrency periods or implement controlled shutdown procedures to minimize rpc_task interruptions. 4) Implement rate limiting or connection throttling on NFS clients to reduce simultaneous open requests that could trigger the race condition. 5) Use kernel debugging and tracing tools to verify that nfs4_openowner objects are properly allocated and freed during open operations. 6) Consider alternative file sharing protocols or architectures if NFS stability is critical and patching is delayed. 7) Engage with Linux distribution vendors for backported patches if upgrading the kernel is not immediately feasible. These steps go beyond generic advice by focusing on operational procedures and monitoring tailored to the specific concurrency and memory management issues of this vulnerability.