CVE-2024-47679 is a race condition vulnerability in the Linux kernel's Virtual File System (VFS) layer, specifically involving inode reference counting and eviction processes. The issue arises from a concurrency flaw between the iput() function, which decrements the inode's reference count (i_count) and potentially frees the inode, and generic_shutdown_super(), which evicts inodes during filesystem shutdown. The vulnerability manifests when two threads simultaneously operate on the same inode (e.g., inode number 261) without proper synchronization. One thread calls iput(), reducing i_count to zero and initiating inode finalization, while another concurrently calls generic_shutdown_super(), evicting inodes and checking i_count. Due to a race, the inode remains linked in the superblock's lists without the I_FREEING or I_WILL_FREE flags set, allowing btrfs_iget() to find and operate on this inode concurrently. This leads to two threads simultaneously evicting the same inode, triggering kernel BUG() conditions related to inode state inconsistencies (I_CLEAR flag). The root cause is the lack of a recheck of i_count after acquiring the inode lock (i_lock), which the patch addresses by adding this revalidation to prevent double eviction. This vulnerability affects Linux kernel versions prior to the fix and is particularly relevant for filesystems like Btrfs that rely heavily on inode management. Exploitation could cause kernel crashes (denial of service) or potentially lead to undefined behavior due to corrupted inode state. No known exploits are reported in the wild yet, and no CVSS score has been assigned. The fix involves modifying the inode reference count handling to ensure atomicity and proper locking, preventing concurrent eviction races.

For European organizations, the impact of CVE-2024-47679 primarily involves potential denial of service (DoS) conditions on Linux systems using affected kernel versions, especially those utilizing Btrfs or similar filesystems. Many European enterprises, government agencies, and service providers rely on Linux servers for critical infrastructure, cloud services, and data centers. A kernel crash caused by this race condition could disrupt services, leading to downtime and potential data loss if inode corruption occurs. While the vulnerability does not directly enable privilege escalation or remote code execution, the resulting instability can affect availability and integrity of systems. Organizations running multi-threaded workloads or heavy filesystem operations are at higher risk. Additionally, embedded Linux devices or network appliances used in European critical infrastructure may also be vulnerable if not updated. The absence of known exploits reduces immediate risk, but the complexity of the bug and its presence in core kernel code necessitate prompt patching to avoid future exploitation attempts. The vulnerability's impact on confidentiality is minimal, but integrity and availability risks are significant in affected environments.

1. Immediate deployment of the official Linux kernel patch that rechecks inode reference counts after acquiring the inode lock to prevent race conditions. 2. Prioritize patching on systems running Btrfs or other filesystems heavily dependent on inode management, especially in multi-threaded or high I/O environments. 3. Implement kernel live patching solutions where possible to reduce downtime during patch application. 4. Monitor kernel logs for BUG() messages or inode-related errors that could indicate exploitation attempts or triggering of the race condition. 5. Conduct thorough testing of updated kernels in staging environments to ensure stability before production rollout. 6. For critical infrastructure, consider temporarily limiting concurrent shutdown or unmount operations that could trigger generic_shutdown_super() during patch deployment. 7. Maintain up-to-date backups and disaster recovery plans to mitigate potential data loss from unexpected kernel crashes. 8. Engage with Linux distribution vendors for timely updates and security advisories specific to their kernel versions and backports.