CVE-2021-47660 in Linux
Summary
by MITRE • 02/26/2025
In the Linux kernel, the following vulnerability has been resolved:
fs/ntfs3: Fix some memory leaks in an error handling path of 'log_replay()'
All error handling paths lead to 'out' where many resources are freed.
Do it as well here instead of a direct return, otherwise 'log', 'ra' and 'log->one_page_buf' (at least) will leak.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 03/19/2025
The vulnerability CVE-2021-47660 represents a memory leak issue within the Linux kernel's ntfs3 file system driver, specifically affecting the log replay functionality. This flaw exists in the error handling path of the log_replay() function which is responsible for replaying transaction logs during file system recovery operations. The ntfs3 driver implements the New Technology File System version 3 which is designed for compatibility with Microsoft's NTFS file system while maintaining Linux kernel standards and security practices. The vulnerability occurs when the system encounters errors during log replay operations, which are critical for maintaining file system consistency after unexpected shutdowns or system failures.
The technical flaw manifests in the improper handling of resource cleanup during error conditions within the ntfs3 file system implementation. When errors occur during log replay processing, the code follows a standard error handling pattern that should clean up allocated resources before exiting. However, in this specific case, the error handling path does not properly release memory allocated for logging structures including the 'log' structure itself, the 'ra' (readahead) structure, and the 'log->one_page_buf' buffer. This direct return from error handling rather than following the established cleanup routine results in these memory resources becoming permanently allocated without proper deallocation, creating a memory leak scenario that can accumulate over time.
The operational impact of this vulnerability extends beyond simple memory consumption issues to potentially affect system stability and performance. While individual memory leaks may appear minor, when multiplied across multiple error conditions during log replay operations, they can contribute to gradual memory exhaustion, particularly in systems handling high volumes of file system operations or those with limited memory resources. The vulnerability affects systems running Linux kernels with ntfs3 file system support, making it relevant to various server and desktop environments that utilize NTFS formatted storage devices. This includes enterprise environments where file system reliability and memory management are critical components of overall system performance and stability.
Mitigation strategies for CVE-2021-47660 involve applying the official kernel patches that correct the error handling path to properly release all allocated resources before returning from error conditions. System administrators should prioritize updating their Linux kernel versions to include the fix, which typically involves upgrading to kernel versions that contain the specific patch addressing this memory leak issue. The vulnerability aligns with CWE-401: "Improper Release of Memory" which classifies memory leak vulnerabilities as a fundamental weakness in resource management. From an attack perspective, while this vulnerability does not directly enable privilege escalation or remote code execution, it represents a potential denial of service vector through memory exhaustion attacks, particularly in resource-constrained environments where multiple memory leaks could accumulate and degrade system performance. The fix implemented follows standard security practices for resource management and aligns with ATT&CK technique T1490: "Inhibit System Recovery" by preventing memory exhaustion that could impact system stability and recovery mechanisms.