CVE-2024-49957 is a vulnerability identified in the Linux kernel, specifically within the OCFS2 (Oracle Cluster File System version 2) component. The flaw arises during the mounting process of the OCFS2 filesystem when the journal loading fails due to an insufficiently sized journal. The vulnerability is triggered when the function journal_reset() fails because the journal is too short, causing jbd2_journal_load() to fail and return a NULL pointer for the journal superblock buffer (j_sb_buffer). Subsequently, ocfs2_journal_shutdown() calls a chain of functions including jbd2_journal_flush(), jbd2_cleanup_journal_tail(), __jbd2_update_log_tail(), and jbd2_journal_update_sb_log_tail(), which attempts to lock the journal buffer via lock_buffer(journal->j_sb_buffer). Since j_sb_buffer is NULL, this results in a null pointer dereference (NULL-ptr-deref) error, leading to a kernel crash (kernel panic) or denial of service (DoS). The root cause is the lack of proper verification that the journal was successfully loaded before proceeding with journal shutdown operations. The fix involves checking the JBD2_LOADED flag to confirm the journal's proper loading and using the journal pointer instead of osb->journal directly to simplify and secure the code path. This vulnerability affects Linux kernel versions containing the specified commit hash f6f50e28f0cb8d7bcdfaacc83129f005dede11b1 and potentially other versions with similar OCFS2 journal handling code. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet.

The primary impact of CVE-2024-49957 is a denial of service condition caused by a kernel crash due to a null pointer dereference in the OCFS2 filesystem journal handling code. For European organizations, especially those relying on Linux servers with OCFS2 filesystems—commonly used in clustered environments and enterprise storage solutions—this vulnerability could lead to unexpected system crashes, service interruptions, and potential data availability issues. While this vulnerability does not directly lead to privilege escalation or data corruption, the resulting denial of service could disrupt critical business operations, particularly in sectors such as finance, telecommunications, and cloud service providers that depend heavily on high-availability Linux clusters. Additionally, recovery from kernel panics may require manual intervention, increasing operational overhead and downtime. Since OCFS2 is a specialized clustered filesystem, the impact is more pronounced in environments using clustered Linux storage or high-availability configurations. The absence of known exploits reduces immediate risk, but the vulnerability should be addressed promptly to prevent potential exploitation or accidental triggering by malformed journal data.

To mitigate CVE-2024-49957, organizations should: 1) Apply the official Linux kernel patches that include the fix for this vulnerability as soon as they become available from trusted Linux distributions or kernel maintainers. 2) Audit and monitor systems using OCFS2 filesystems to identify any instances where journal loading failures occur, and implement alerting for abnormal kernel messages or crashes related to OCFS2. 3) Where feasible, consider migrating critical workloads from OCFS2 to more widely used and actively maintained filesystems such as ext4 or XFS, which do not exhibit this vulnerability. 4) Implement robust backup and recovery procedures to minimize downtime in case of kernel panics caused by this issue. 5) Limit access to systems running OCFS2 filesystems to trusted users and networks to reduce the risk of accidental or malicious triggering of the vulnerability. 6) Regularly update Linux kernels and monitor vendor advisories for any additional patches or mitigations related to OCFS2 and journaling subsystems.