CVE-2022-49896 in Linux
Summary
by MITRE • 05/01/2025
In the Linux kernel, the following vulnerability has been resolved:
cxl/pmem: Fix cxl_pmem_region and cxl_memdev leak
When a cxl_nvdimm object goes through a ->remove() event (device physically removed, nvdimm-bridge disabled, or nvdimm device disabled), then any associated regions must also be disabled. As highlighted by the cxl-create-region.sh test [1], a single device may host multiple
regions, but the driver was only tracking one region at a time. This leads to a situation where only the last enabled region per nvdimm device is cleaned up properly. Other regions are leaked, and this also causes cxl_memdev reference leaks.
Fix the tracking by allowing cxl_nvdimm objects to track multiple region associations.
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Analysis
by VulDB Data Team • 08/10/2025
The vulnerability described in CVE-2022-49896 represents a critical resource management flaw within the Linux kernel's CXL (Compute Express Link) memory subsystem, specifically affecting the persistent memory driver component. This issue manifests in the cxl_pmem driver which handles CXL persistent memory devices, creating a scenario where memory regions and device references are not properly cleaned up during device removal events. The root cause stems from an insufficient tracking mechanism within the kernel's CXL subsystem that fails to maintain proper associations between nvdimm objects and their multiple associated memory regions. The vulnerability impacts systems utilizing CXL persistent memory technology, particularly those employing nvdimm bridges and devices that support multiple memory regions per physical device.
The technical flaw resides in the driver's inability to properly track multiple memory regions associated with a single cxl_nvdimm object, creating a memory leak condition when devices undergo removal operations. During normal operation, a single CXL nvdimm device may host multiple memory regions that must be properly disabled and cleaned up when the device is removed or disabled. However, the existing implementation only maintains tracking for a single region, causing the driver to only clean up the last enabled region while leaving other associated regions in memory. This improper cleanup results in both cxl_pmem_region and cxl_memdev reference leaks, where kernel memory structures remain allocated and referenced even after the physical device has been removed or disabled. The issue is particularly concerning because it affects the fundamental resource management capabilities of the kernel's persistent memory subsystem, potentially leading to gradual memory exhaustion over time.
The operational impact of this vulnerability extends beyond simple memory leaks, as it compromises the stability and reliability of systems utilizing CXL persistent memory technologies. When multiple regions per nvdimm device are not properly cleaned up, the system experiences resource consumption degradation where kernel memory becomes increasingly fragmented and unavailable for other operations. This can lead to system instability, performance degradation, and potentially system crashes in severe cases where memory exhaustion occurs. The vulnerability is particularly dangerous in server environments where persistent memory devices are frequently hot-plugged and removed, as the cumulative effect of these leaks can cause systems to become unresponsive over extended periods of operation. Additionally, the reference leaks create potential for kernel memory corruption and can interfere with proper device reinitialization processes, making system maintenance and management operations more challenging.
The fix implemented addresses the core tracking mechanism by modifying the cxl_nvdimm object to properly maintain associations with multiple regions rather than limiting tracking to a single region. This enhancement ensures that when a device removal event occurs, all associated regions are properly disabled and cleaned up, eliminating both the cxl_pmem_region and cxl_memdev reference leaks. The solution aligns with standard kernel memory management practices and follows established patterns for resource cleanup in device drivers. From a cybersecurity perspective, this vulnerability demonstrates the importance of proper resource tracking and cleanup in kernel modules, as inadequate memory management can create persistent security risks. The fix reduces the attack surface by preventing potential memory exhaustion attacks that could exploit these resource leaks, while also improving system reliability and maintainability. This remediation addresses the underlying CWE-404 issue of improper resource cleanup and helps prevent potential exploitation through resource exhaustion attacks that could be leveraged in containerized environments or virtualized systems where persistent memory is utilized.