CVE-2022-49634 in Linux
Summary
by MITRE • 02/26/2025
In the Linux kernel, the following vulnerability has been resolved:
sysctl: Fix data-races in proc_dou8vec_minmax().
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_dou8vec_minmax() to use READ_ONCE() and WRITE_ONCE() internally to fix data-races on the sysctl side. For now, proc_dou8vec_minmax() itself is tolerant to a data-race, but we still need to add annotations on the other subsystem's side.
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Analysis
by VulDB Data Team • 02/26/2025
The vulnerability identified as CVE-2022-49634 represents a critical data-race condition within the Linux kernel's sysctl subsystem, specifically affecting the proc_dou8vec_minmax() function. This flaw manifests in a fundamental concurrency issue where sysctl variables are accessed simultaneously by multiple processes or kernel threads without proper synchronization mechanisms. The vulnerability exists in the kernel's configuration interface where users can read and modify system parameters at runtime through the /proc filesystem, creating a scenario where concurrent access can lead to inconsistent or corrupted data states. The root cause stems from the absence of proper memory barrier operations when reading from or writing to sysctl variables, allowing for load/store tearing conditions that can compromise system stability and security. This type of race condition falls under the category of memory safety issues and is particularly dangerous in kernel space where data corruption can lead to system crashes or potential privilege escalation.
The technical implementation of this vulnerability involves the proc_dou8vec_minmax() function which handles 8-bit unsigned integer vectors with minimum and maximum value constraints for sysctl parameters. When multiple threads attempt to read or write these values simultaneously, the lack of proper atomic operations creates opportunities for partial reads or writes to occur, resulting in corrupted data that may contain invalid combinations of bytes from different operations. The patch addresses this by implementing READ_ONCE() and WRITE_ONCE() macros internally within the function, which provide the necessary memory ordering guarantees to prevent data races while maintaining the function's existing behavior and interface. This approach follows established kernel development practices for handling concurrent access to shared data structures, ensuring that all memory accesses are properly ordered and visible to all concurrent threads. The solution aligns with the kernel's memory model requirements and provides a clean mechanism for protecting against the specific race condition without disrupting existing functionality.
The operational impact of this vulnerability extends beyond simple system instability to potentially compromise the integrity of critical system parameters that control kernel behavior and security policies. When data races occur in sysctl variables, the system may exhibit unpredictable behavior during parameter modifications, leading to configuration corruption that could affect network security settings, memory management policies, or other critical kernel subsystems. Attackers could potentially exploit this race condition to manipulate kernel parameters in ways that create security vulnerabilities or denial-of-service conditions, particularly in environments where sysctl parameters are frequently modified or monitored. The vulnerability is particularly concerning in multi-threaded or multi-core systems where concurrent access patterns are common, as the probability of encountering the race condition increases significantly. Additionally, the presence of such data races can mask other underlying issues in kernel subsystems, making debugging and security analysis more challenging for system administrators and security researchers.
Mitigation strategies for this vulnerability primarily focus on applying the kernel patch that implements READ_ONCE() and WRITE_ONCE() operations within the proc_dou8vec_minmax() function. System administrators should ensure that all Linux systems are updated to kernel versions containing this fix, particularly those running in security-sensitive environments or handling critical workloads. The patch approach addresses the immediate issue by providing proper memory ordering guarantees, but broader system hardening should also include monitoring for unusual sysctl parameter changes and implementing proper access controls for sysctl interfaces. Security teams should consider this vulnerability as part of their kernel security posture assessment, particularly in environments where kernel-level access is restricted or where sysctl parameters are frequently modified by automated processes. The fix aligns with common security practices for preventing race conditions in kernel space and follows the principle of least privilege by ensuring that concurrent access to system parameters is properly synchronized. Organizations should also implement regular kernel update policies to ensure that similar vulnerabilities are addressed promptly, as this type of memory safety issue can have far-reaching consequences for system integrity and security.