CVE-2023-53137 in Linux
Summary
by MITRE • 05/02/2025
In the Linux kernel, the following vulnerability has been resolved:
ext4: Fix possible corruption when moving a directory
When we are renaming a directory to a different directory, we need to update '..' entry in the moved directory. However nothing prevents moved directory from being modified and even converted from the inline format to the normal format. When such race happens the rename code gets confused and we crash. Fix the problem by locking the moved directory.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 05/12/2026
The vulnerability in question affects the ext4 filesystem implementation within the Linux kernel and represents a race condition that can lead to filesystem corruption during directory renaming operations. This issue occurs specifically when moving a directory from one location to another within the same filesystem, where the rename operation must update the '..' entry in the moved directory to point to its new parent directory. The flaw arises from insufficient synchronization mechanisms during this critical operation, creating a window where concurrent modifications can interfere with the rename process. When a directory is being moved, the kernel code attempts to update its internal metadata while simultaneously allowing other processes to modify the directory structure, potentially converting it from inline format to regular format during the operation. This race condition fundamentally breaks the consistency model of the filesystem operations and can result in severe data corruption or system crashes.
The technical root cause of this vulnerability stems from the lack of proper locking mechanisms around the directory movement operation, particularly when dealing with the '..' entry updates in the moved directory. According to CWE-362, this represents a classic race condition where multiple threads or processes can access shared resources concurrently without proper synchronization. The vulnerability manifests when the rename code path does not adequately protect the moved directory from concurrent modifications, allowing for scenarios where the directory structure changes during the rename operation. This can occur when a directory is converted from inline format to normal format while the rename operation is in progress, causing the kernel's internal logic to become confused about the directory's current state and resulting in memory corruption or system crashes. The issue is particularly dangerous because it operates at the kernel level within the filesystem driver, potentially affecting the stability and integrity of the entire system.
The operational impact of this vulnerability extends beyond simple filesystem corruption to potentially compromise system stability and data integrity across all Linux systems utilizing ext4 filesystems. Attackers could potentially exploit this race condition to cause system crashes or induce data corruption in scenarios involving concurrent directory operations, file system management tasks, or automated processes that frequently move directories. The vulnerability affects systems where multiple processes or threads are simultaneously operating on directory structures, particularly in environments with high I/O loads or complex file system operations. From an ATT&CK perspective, this vulnerability could be leveraged as part of a broader attack chain targeting system stability or availability, potentially enabling denial-of-service conditions or data integrity breaches that could impact critical infrastructure. The flaw is particularly concerning in enterprise environments where ext4 filesystems are commonly used for storage, database operations, or containerized applications that frequently perform directory management tasks.
The fix for this vulnerability involves implementing proper locking mechanisms around the directory movement operation to prevent concurrent modifications during the critical phase of the rename process. This approach directly addresses the race condition by ensuring that the moved directory remains in a consistent state throughout the entire rename operation, preventing the conversion from inline to normal format during the update of the '..' entry. The solution requires that the kernel code acquire appropriate locks before beginning the directory movement and maintain these locks until the entire operation completes successfully. This approach aligns with established best practices for concurrent programming in kernel space and follows the principles of atomic operations for filesystem metadata updates. System administrators should ensure that all systems running ext4 filesystems are updated with patches that implement this locking mechanism, particularly in environments where directory operations are frequent or where high availability is critical. The fix effectively prevents the scenario where the rename code becomes confused by concurrent modifications, thereby maintaining filesystem integrity and preventing both crashes and data corruption. Regular system updates and patch management procedures should include verification that the ext4 filesystem implementation properly implements these synchronization mechanisms to prevent exploitation of this class of vulnerabilities.