CVE-2022-49439 in Linux
Summary
by MITRE • 02/26/2025
In the Linux kernel, the following vulnerability has been resolved:
powerpc/fsl_rio: Fix refcount leak in fsl_rio_setup
of_parse_phandle() returns a node pointer with refcount incremented, we should use of_node_put() on it when not need anymore. Add missing of_node_put() to avoid refcount leak.
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Analysis
by VulDB Data Team • 03/18/2025
The vulnerability CVE-2022-49439 represents a memory management issue within the Linux kernel's powerpc/fsl_rio subsystem, specifically affecting the fsl_rio_setup function. This flaw manifests as a reference count leak that occurs when processing device tree nodes during the setup of Freescale RapidIO (Rio) infrastructure. The root cause lies in improper handling of device tree node references obtained through the of_parse_phandle() function, which increments the reference count of the returned node pointer. When this reference is not properly released using of_node_put(), the kernel maintains unnecessary references to device tree nodes, leading to gradual memory consumption and potential resource exhaustion over time. This vulnerability affects systems utilizing Freescale RapidIO infrastructure on powerpc architectures, particularly those implementing device tree-based configuration management for hardware components.
The technical implementation of this vulnerability stems from a fundamental failure in reference counting management within the device tree parsing subsystem. The of_parse_phandle() function is designed to retrieve device tree nodes and automatically increment their reference counts to ensure proper lifecycle management. However, in the fsl_rio_setup function, the code properly acquires the node reference but fails to decrement the reference count when the node is no longer needed. This pattern violates standard kernel memory management practices and creates a resource leak that accumulates over time as the system continues to process device tree configurations. The vulnerability is classified under CWE-404, which specifically addresses improper resource management and object lifetime issues in software systems. The reference counting mechanism in the Linux kernel's device tree subsystem relies on explicit increment and decrement operations to track node usage, and the missing of_node_put() call breaks this critical balance.
The operational impact of CVE-2022-49439 extends beyond simple memory consumption, potentially affecting system stability and performance in embedded powerpc environments. While the immediate effect may appear as gradual memory bloat, sustained exploitation could lead to resource exhaustion that impacts system responsiveness and potentially causes kernel panics or system crashes. The vulnerability is particularly concerning in long-running embedded systems or industrial control environments where Freescale RapidIO infrastructure is utilized for high-speed interconnectivity between system components. Attackers could potentially leverage this vulnerability to perform resource exhaustion attacks, making systems more susceptible to denial of service conditions. The flaw operates at the kernel level, meaning that any process or driver interacting with the fsl_rio subsystem could trigger the leak, making it a persistent threat to system integrity. According to ATT&CK framework, this vulnerability could be categorized under T1499.004 for resource exhaustion and potentially T1566.001 for initial access through kernel-level exploitation techniques.
Mitigation strategies for CVE-2022-49439 focus on implementing proper reference counting practices within the kernel source code. The fix requires adding the missing of_node_put() call to properly release device tree node references after they are no longer needed, thereby restoring the balance in the reference counting mechanism. System administrators should prioritize applying the relevant kernel patches that address this specific vulnerability, particularly in production environments where powerpc systems with Freescale RapidIO infrastructure are deployed. Organizations should conduct thorough testing of kernel updates to ensure compatibility with existing hardware configurations and system integrations. Additionally, monitoring systems for unusual memory consumption patterns can help detect potential exploitation of this vulnerability. The fix aligns with kernel development best practices established in the Linux kernel documentation and represents a standard procedure for managing device tree node references in kernel space. Regular kernel security updates and vulnerability assessments should include verification of proper reference counting implementation across all device tree parsing functions to prevent similar issues from emerging in other subsystems.