CVE-2024-26697 in Linux
Summary
by MITRE • 04/03/2024
In the Linux kernel, the following vulnerability has been resolved:
nilfs2: fix data corruption in dsync block recovery for small block sizes
The helper function nilfs_recovery_copy_block() of nilfs_recovery_dsync_blocks(), which recovers data from logs created by data sync writes during a mount after an unclean shutdown, incorrectly calculates the on-page offset when copying repair data to the file's page cache. In environments where the block size is smaller than the page size, this flaw can cause data corruption and leak uninitialized memory bytes during the recovery process.
Fix these issues by correcting this byte offset calculation on the page.
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Analysis
by VulDB Data Team • 07/17/2025
The vulnerability identified as CVE-2024-26697 affects the Linux kernel's nilfs2 file system implementation, specifically targeting data recovery mechanisms during unclean shutdown scenarios. This flaw exists within the nilfs_recovery_copy_block() helper function which operates as part of the nilfs_recovery_dsync_blocks() recovery process. The issue manifests when the file system attempts to recover data from logs generated by data sync writes that occurred during an unclean shutdown event, where the system must reconstruct file data from available log entries to maintain data integrity.
The technical root cause of this vulnerability stems from an incorrect calculation of on-page offsets when copying repair data into the file's page cache. This miscalculation occurs specifically in environments where the block size is smaller than the page size, creating a mismatch between the logical data structure and the physical memory layout. The flawed offset calculation results in data being written to incorrect memory locations within the page cache, leading to systematic data corruption during the recovery process. According to CWE-129, this represents an improper validation of an offset, while the ATT&CK framework would classify this under T1490 - Data Destruction and T1565 - Data Manipulation, as the vulnerability enables unauthorized modification of stored data through recovery mechanisms.
The operational impact of this vulnerability extends beyond simple data corruption, as it also introduces potential information disclosure risks through uninitialized memory byte leakage. During the recovery process, the incorrect offset calculations cause the system to copy data from memory locations that may contain sensitive information from previous operations, potentially exposing system data to unauthorized access. This issue particularly affects systems using nilfs2 file systems with small block sizes, where the gap between block and page boundaries creates the conditions necessary for the miscalculation to occur. The vulnerability is most critical in environments where data integrity is paramount, such as financial systems, database servers, or any application requiring reliable data recovery after unexpected shutdowns.
Mitigation strategies for CVE-2024-26697 should prioritize the immediate application of the kernel patch that corrects the byte offset calculation in the nilfs_recovery_copy_block() function. System administrators should ensure all affected systems are updated to kernel versions containing the fix, as the vulnerability can lead to complete data loss or corruption during recovery operations. Additionally, organizations should implement monitoring solutions to detect potential data corruption in nilfs2 file systems, particularly after unclean shutdown events. The fix addresses the core issue by properly calculating the on-page offset based on the actual relationship between block and page boundaries, ensuring that recovery data is correctly positioned within the page cache. Security teams should also consider implementing regular data integrity checks and backup verification procedures to detect any potential corruption that may have occurred before the patch was applied, as the vulnerability could have been exploited to introduce subtle data inconsistencies that might not be immediately apparent.