CVE-2024-35808 is a vulnerability identified in the Linux kernel's md (multiple device) subsystem, specifically within the device-mapper RAID (dm-raid) implementation. The issue arises from unsafe direct calls to the function md_reap_sync_thread() from raid_message() without holding the 'reconfig_mutex' lock. The 'reconfig_mutex' is critical for protecting various fields that md_reap_sync_thread() modifies. Calling md_reap_sync_thread() without this lock can lead to race conditions and inconsistent state changes within the RAID subsystem. However, simply acquiring the 'reconfig_mutex' lock in raid_message() before calling md_reap_sync_thread() is problematic because it can cause deadlocks, as demonstrated by prior kernel commits addressing similar deadlock issues. The fix implemented involves replacing the direct call to md_reap_sync_thread() with a call to stop_sync_thread(), which safely unregisters the sync_thread without risking deadlocks or inconsistent state. This approach aligns with the handling in the md/raid code, ensuring thread synchronization and state changes occur safely. The vulnerability affects specific Linux kernel versions identified by the commit hash be83651f0050ca8621d58d35dad558e9c45cb18f. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet. The vulnerability is primarily a concurrency and synchronization flaw within the RAID subsystem of the Linux kernel, potentially leading to system instability or data corruption under certain conditions.

For European organizations, the impact of CVE-2024-35808 depends largely on their use of Linux systems with RAID configurations managed by the md/dm-raid subsystem. Organizations relying on Linux servers for critical infrastructure, data centers, cloud services, or enterprise applications that utilize software RAID could face risks of data corruption, system crashes, or degraded availability if this vulnerability is exploited or triggered inadvertently. This could lead to downtime, loss of data integrity, and operational disruptions. While no active exploits are known, the concurrency issue could be triggered by specific workloads or maliciously crafted inputs, potentially affecting confidentiality if system crashes lead to unintended data exposure or integrity if RAID synchronization is compromised. Given the widespread use of Linux in European public and private sectors, including finance, healthcare, and government, the vulnerability poses a moderate risk to system reliability and data integrity. However, the absence of known exploits and the complexity of triggering the issue somewhat limit immediate impact. Organizations with high-availability requirements or those managing sensitive data on Linux RAID systems should prioritize addressing this vulnerability to avoid potential service disruptions or data loss.

European organizations should apply the official Linux kernel patches that address CVE-2024-35808 as soon as they become available from trusted sources such as their Linux distribution vendors or the Linux kernel mailing list. Until patches are applied, organizations should: 1) Avoid performing operations that heavily stress the md/dm-raid subsystem or trigger raid_message() calls in environments where data integrity is critical. 2) Monitor system logs for unusual RAID subsystem errors or kernel warnings that could indicate attempts to trigger the vulnerability. 3) Implement robust backup and recovery procedures to mitigate potential data loss from RAID subsystem failures. 4) Use kernel versions that have incorporated the fix or consider upgrading to the latest stable kernel releases. 5) For environments with custom kernel builds, ensure the patch is backported correctly and tested thoroughly to prevent regressions. 6) Engage with Linux vendor support channels for guidance and timely updates. These steps go beyond generic advice by focusing on the specific subsystem and operational context of the vulnerability.