CVE-2022-49893 in Linux
Summary
by MITRE • 05/01/2025
In the Linux kernel, the following vulnerability has been resolved:
cxl/region: Fix cxl_region leak, cleanup targets at region delete
When a region is deleted any targets that have been previously assigned to that region hold references to it. Trigger those references to drop by detaching all targets at unregister_region() time.
Otherwise that region object will leak as userspace has lost the ability to detach targets once region sysfs is torn down.
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Analysis
by VulDB Data Team • 11/11/2025
This vulnerability exists within the Linux kernel's CXL (Compute Express Link) subsystem, specifically affecting how region objects are managed during cleanup operations. The issue manifests as a memory leak that occurs when CXL regions are deleted from the system. The vulnerability is particularly concerning because it represents a resource management failure that can lead to progressive system degradation over time. The CXL subsystem is designed to provide high-performance interconnect for memory expansion and storage, making proper resource management critical for system stability and performance. When a region is deleted, the kernel fails to properly release all references to that region object, creating a dangling reference that prevents proper memory deallocation. This behavior violates fundamental principles of resource management and can lead to exhaustion of system resources, ultimately impacting system availability and performance.
The technical flaw stems from improper cleanup handling within the cxl_region subsystem where the unregister_region() function does not adequately detach all associated targets before releasing the region object. This creates a scenario where target objects maintain references to the deleted region, preventing the kernel's memory management subsystem from properly reclaiming the allocated memory. The vulnerability is classified as a memory leak according to CWE-401 and represents a failure in proper resource cleanup. The issue occurs during the sysfs teardown process where userspace applications lose the ability to detach targets, leaving the region object in a partially cleaned state. This improper cleanup mechanism violates the principle of deterministic resource management and can lead to accumulation of leaked objects over time, especially in systems with frequent CXL region creation and deletion operations.
The operational impact of this vulnerability can be significant in production environments where CXL devices are actively used for memory expansion or storage acceleration. Systems experiencing this leak may show progressive memory consumption increases, potentially leading to performance degradation, system instability, or complete resource exhaustion. The vulnerability particularly affects systems that dynamically create and destroy CXL regions, such as those using memory expansion cards or storage devices that require frequent region reconfiguration. Attackers could potentially exploit this memory leak to cause denial of service conditions by repeatedly creating and deleting regions, leading to system resource exhaustion. Additionally, the vulnerability impacts system reliability by creating unpredictable memory usage patterns that can interfere with other critical system processes. This issue aligns with ATT&CK technique T1490 which involves resource exhaustion attacks, and represents a failure in system stability and resource management that can be leveraged to degrade system performance.
Mitigation strategies for this vulnerability include applying the kernel patch that ensures proper target detachment during region deletion operations. System administrators should prioritize updating their kernel versions to include the fix, particularly in production environments where CXL devices are deployed. The patch implementation requires modifying the unregister_region() function to explicitly detach all targets before allowing the region object to be freed. Monitoring systems should be implemented to track memory usage patterns and detect potential memory leaks in CXL subsystems. Regular system audits should verify proper cleanup of CXL resources and identify any lingering references to deleted regions. Organizations using CXL-enabled systems should implement automated processes to periodically validate region management operations and ensure that resource cleanup occurs properly. The fix addresses the root cause by ensuring that all references are properly dropped during cleanup, preventing the accumulation of leaked objects and maintaining system stability. This vulnerability demonstrates the importance of proper reference counting and cleanup procedures in kernel subsystems, particularly those dealing with hardware interfaces that require dynamic resource management.