CVE-2024-42077 is a vulnerability identified in the Linux kernel's OCFS2 (Oracle Cluster File System version 2) filesystem implementation. The flaw arises from improper handling of transaction credits during direct I/O (DIO) write operations on heavily fragmented OCFS2 filesystems. Specifically, the function ocfs2_dio_end_io_write() estimates the number of transaction credits required using ocfs2_calc_extend_credits(), but this calculation does not account for arbitrarily large I/O operations containing numerous extents. Extents represent contiguous blocks of storage, and in cases where the I/O contains many single-block extents, the code path repeatedly calls ocfs2_replace_extent_rec() without extending the current transaction. This leads to exhaustion of transaction credits, triggering a WARN_ON condition in the journaling layer (jbd2_handle_buffer_credits) and causing the OCFS2 filesystem to abort. The abort manifests as a kernel panic with a forced system crash, as documented by the panic stack trace provided. This issue was observed in real-world scenarios on heavily fragmented OCFS2 filesystems, indicating practical impact. The fix involves ensuring that before each call to ocfs2_mark_extent_written(), the transaction has enough credits for at least one extent insert, preventing premature exhaustion of credits and subsequent panics. No CVSS score has been assigned yet, and no known exploits are reported in the wild. The vulnerability affects Linux kernel versions identified by the commit hash c15471f79506830f80eca0e7fe09b8213953ab5f and similar revisions containing the vulnerable code.

For European organizations, the impact of CVE-2024-42077 can be significant in environments utilizing the OCFS2 filesystem, particularly in clustered or high-availability Linux server deployments where OCFS2 is chosen for shared storage. A kernel panic triggered by this vulnerability results in an immediate system crash, causing denial of service (DoS) conditions. This can disrupt critical services, data processing, or storage availability, especially in enterprise data centers, cloud providers, or industries relying on Linux-based clustered storage solutions. Since the vulnerability is triggered by heavily fragmented filesystems and large direct I/O operations, workloads involving intensive file writes or database operations on OCFS2 may be particularly vulnerable. The forced kernel panic also risks potential data loss or corruption if the system crashes during critical write operations. Although no remote code execution or privilege escalation is indicated, the availability impact alone can lead to operational downtime, financial loss, and reputational damage. European organizations with Linux infrastructure using OCFS2 should consider this vulnerability a serious stability and availability risk.

1. Immediate patching: Apply the Linux kernel update or backported patch that addresses CVE-2024-42077 as soon as it becomes available from trusted Linux distribution vendors or kernel maintainers. 2. Filesystem assessment: Audit and monitor OCFS2 filesystem fragmentation levels and consider defragmentation or migration to alternative filesystems if fragmentation is high and cannot be controlled. 3. Workload tuning: Limit or segment large direct I/O write operations that could trigger the exhaustion of transaction credits, especially on heavily fragmented OCFS2 filesystems. 4. Monitoring and alerting: Implement kernel and system monitoring to detect early signs of WARN_ON conditions related to journaling or transaction credit exhaustion, enabling proactive intervention before a panic occurs. 5. Backup and recovery planning: Ensure robust backup strategies and disaster recovery plans are in place to mitigate data loss risks from unexpected kernel panics. 6. Testing: Before deploying patches in production, test them in staging environments to confirm stability and compatibility with existing workloads and clustered configurations. 7. Vendor coordination: Engage with Linux distribution vendors and OCFS2 maintainers for guidance and timely updates.