CVE-2024-50279 is a vulnerability identified in the Linux kernel's device-mapper cache (dm-cache) subsystem. The flaw arises from an out-of-bounds memory access when resizing the dirty bitset during the shrinking of the fast device in a cache setup. Specifically, dm-cache maintains a bitset to track which cache blocks are 'dirty' (i.e., modified but not yet written back to the underlying storage). When the fast device is shrunk, dm-cache iterates over this dirty bitset to determine which blocks to drop. However, an indexing bug in the bitset iteration logic causes the code to access memory beyond the allocated bounds of the dirty bitset array. This can lead to a kernel memory read beyond the intended limits, as demonstrated by Kernel Address Sanitizer (KASAN) reports showing out-of-bounds reads at specific virtual addresses during cache device resizing operations. The vulnerability is triggered by a sequence of dmsetup commands that create cache devices with specific sizes and then shrink the fast device, causing the out-of-bounds access. The root cause is an incorrect post-increment of the index used to iterate over the dirty bitset, which was fixed by adjusting the index increment logic. While the vulnerability does not appear to have known exploits in the wild yet, it represents a flaw in kernel memory safety that could potentially be leveraged in more complex attack scenarios. The affected versions are specific Linux kernel commits identified by the hash f494a9c6b1b6dd9a9f21bbb75d9210d478eeb498, indicating a narrow window of vulnerable kernel builds. No CVSS score has been assigned yet, and no direct evidence of remote exploitability or privilege escalation is provided in the disclosure.

For European organizations, the impact of CVE-2024-50279 depends largely on their use of Linux systems employing dm-cache for storage acceleration or caching. This vulnerability could lead to kernel memory corruption or crashes (denial of service) when resizing cache devices, potentially disrupting critical services relying on affected storage configurations. Although no direct privilege escalation or remote code execution is documented, out-of-bounds memory access in the kernel can be a stepping stone for attackers to escalate privileges or cause system instability. Organizations running data centers, cloud infrastructure, or enterprise Linux servers with dm-cache enabled could face service interruptions or require emergency patching. Given the kernel-level nature of the flaw, it affects the integrity and availability of systems rather than confidentiality directly. The absence of known exploits reduces immediate risk, but the potential for future exploitation mandates proactive mitigation. European entities with compliance requirements around system stability and data integrity (e.g., financial institutions, healthcare providers) should prioritize addressing this vulnerability to avoid operational disruptions.

1. Apply the official Linux kernel patches that fix the dm-cache dirty bitset indexing bug as soon as they become available from trusted Linux distribution vendors or the kernel mainline. 2. If patching is delayed, avoid resizing dm-cache fast devices dynamically, especially shrinking operations, to prevent triggering the out-of-bounds access. 3. Audit and monitor systems using dm-cache for unusual kernel logs or crashes that might indicate attempts to exploit this vulnerability. 4. Employ kernel hardening techniques such as Kernel Address Sanitizer (KASAN) in testing environments to detect similar memory safety issues proactively. 5. For critical production systems, consider disabling dm-cache if it is not essential or replacing it with alternative caching mechanisms until patches are applied. 6. Maintain up-to-date backups and recovery plans to mitigate potential service disruptions caused by kernel crashes. 7. Coordinate with Linux distribution security advisories to receive timely updates and verify that the applied kernel versions include the fix for CVE-2024-50279.