CVE-2024-57946 is a vulnerability identified in the Linux kernel's virtio-blk driver, which is responsible for handling block device I/O in virtualized environments. The issue arises from the handling of the virtqueue during system suspend operations. Specifically, the vulnerability concerns the use of queue freezing in the power management (PM) callbacks of virtio-blk. The original implementation replaced queue quiesce with queue freeze to drain in-flight I/O requests before suspending the system. However, freezing the queue for the entire suspend context can lead to deadlocks because any attempt to enter the bio_queue (block I/O queue) while the queue is frozen can cause the system to hang. This is due to the fact that various suspend callbacks may attempt to interact with the queue, and a frozen queue blocks these operations, triggering lock dependency warnings and potential deadlocks. The fix involves reverting to the previous behavior of keeping the queue quiesced (paused but not frozen) during suspend, while still ensuring that in-flight I/O requests are properly drained by temporarily freezing and unfreezing the queue as needed. This approach balances the need to safely suspend the system without causing deadlocks or blocking critical I/O operations. The vulnerability is present in specific Linux kernel versions identified by the commit hash 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2. No known exploits are reported in the wild, and no CVSS score has been assigned yet.

For European organizations, the impact of CVE-2024-57946 primarily affects systems running Linux kernels with the vulnerable virtio-blk implementation, especially those operating in virtualized environments such as cloud infrastructure, data centers, and enterprise virtualization platforms. The vulnerability can lead to system hangs or deadlocks during suspend operations, potentially causing denial of service (DoS) conditions. This can disrupt critical services, affect availability of virtual machines, and impair maintenance operations that rely on suspend/resume cycles. While the vulnerability does not directly expose confidentiality or integrity risks, the availability impact can be significant for organizations relying on high uptime and stable virtualization platforms. Industries with heavy reliance on Linux-based virtualization, such as finance, telecommunications, and public sector entities in Europe, could experience operational disruptions if unpatched systems encounter this issue. Additionally, the deadlock risk may complicate system recovery and increase administrative overhead. However, since exploitation requires system suspend operations and the issue is related to kernel-level I/O handling, the attack surface is limited to environments where suspend/resume is actively used and the affected kernel versions are deployed.

To mitigate CVE-2024-57946, European organizations should: 1) Apply the official Linux kernel patches that revert the queue handling to the safer quiesce/unfreeze approach as soon as they become available from trusted Linux distributions or kernel maintainers. 2) Identify and inventory all Linux systems running the affected kernel versions, focusing on virtualized environments using virtio-blk devices. 3) Where immediate patching is not feasible, avoid using system suspend/resume operations on affected systems to prevent triggering the deadlock condition. 4) Monitor system logs and kernel messages for lockdep warnings or signs of deadlock related to virtio-blk queues. 5) Test kernel updates in staging environments to ensure compatibility and stability before wide deployment, especially in critical infrastructure. 6) Engage with Linux distribution vendors for backported fixes if using long-term support kernels. 7) Implement robust backup and recovery procedures to minimize downtime in case of system hangs. These steps go beyond generic advice by emphasizing operational controls around suspend usage and proactive monitoring for deadlock symptoms.