CVE-2022-49641 in Linux
Summary
by MITRE • 02/26/2025
In the Linux kernel, the following vulnerability has been resolved:
sysctl: Fix data races in proc_douintvec().
A sysctl variable is accessed concurrently, and there is always a chance of data-race. So, all readers and writers need some basic protection to avoid load/store-tearing.
This patch changes proc_douintvec() to use READ_ONCE() and WRITE_ONCE() internally to fix data-races on the sysctl side. For now, proc_douintvec() itself is tolerant to a data-race, but we still need to add annotations on the other subsystem's side.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 04/17/2025
The vulnerability identified as CVE-2022-49641 resides within the Linux kernel's sysctl subsystem, specifically affecting the proc_douintvec() function that handles unsigned integer vector sysctl variables. This issue represents a classic data race condition that can occur when multiple threads or processes attempt to access the same sysctl variable simultaneously, creating potential inconsistencies in system behavior and undermining the reliability of kernel configuration management. The vulnerability stems from insufficient synchronization mechanisms when reading from and writing to sysctl variables, particularly those that are unsigned integers, which are commonly used for system parameters such as network timeouts, buffer sizes, and other critical kernel configuration values.
The technical flaw manifests in the proc_douintvec() function's failure to properly protect against concurrent access patterns that could lead to load/store-tearing conditions. When multiple processes attempt to read or modify sysctl variables simultaneously, the lack of proper atomic operations can result in partial reads or writes that corrupt the underlying data structures. This type of data race vulnerability is particularly dangerous in kernel space where inconsistent data can lead to system instability, unpredictable behavior, or even security implications. The vulnerability affects the fundamental mechanism by which kernel parameters are exposed through the /proc filesystem and can be accessed programmatically through sysctl system calls.
The operational impact of this vulnerability extends beyond simple performance degradation to potentially compromising system stability and security. When data races occur in kernel sysctl handling, it can lead to incorrect parameter values being applied to system components, causing network stack anomalies, memory management issues, or other subsystem malfunctions. The vulnerability is particularly concerning because sysctl variables are frequently accessed during normal system operation and can be modified by both privileged processes and potentially unprivileged users depending on system configuration. This creates an attack surface where malicious actors could potentially exploit the data race to cause system instability or manipulate kernel behavior through carefully timed concurrent access patterns.
The fix implemented in this patch addresses the vulnerability by incorporating READ_ONCE() and WRITE_ONCE() macros within the proc_douintvec() function to ensure proper atomic access to sysctl variables. These macros provide the necessary memory ordering guarantees to prevent load/store-tearing conditions while maintaining the performance characteristics of the sysctl subsystem. However, the patch acknowledges that while proc_douintvec() itself is now protected, additional annotations and synchronization mechanisms are required on other subsystem sides to provide comprehensive protection. This approach aligns with the principle of least privilege and defense in depth, ensuring that all kernel interfaces handling shared data structures are properly protected against concurrent access. The solution follows established kernel development practices and addresses the underlying CWE-362 weakness related to concurrent access to shared resources, which is categorized under the broader ATT&CK technique of privilege escalation through system configuration manipulation.