CVE-2021-47513 in Linux
Summary
by MITRE • 05/24/2024
In the Linux kernel, the following vulnerability has been resolved:
net: dsa: felix: Fix memory leak in felix_setup_mmio_filtering
Avoid a memory leak if there is not a CPU port defined.
Addresses-Coverity-ID: 1492897 ("Resource leak") Addresses-Coverity-ID: 1492899 ("Resource leak")
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Analysis
by VulDB Data Team • 05/24/2024
The vulnerability CVE-2021-47513 represents a memory leak issue within the Linux kernel's Distributed Switch Architecture DSA subsystem, specifically affecting the Felix switch driver implementation. This flaw exists in the felix_setup_mmio_filtering function which handles memory management for hardware-based packet filtering operations. The vulnerability manifests when the system attempts to configure memory-mapped I/O filtering capabilities but fails to properly clean up allocated resources when no CPU port is defined in the switch configuration. This represents a classic resource management failure that can lead to progressive memory consumption over time, potentially degrading system performance or causing unexpected system behavior.
The technical root cause of this vulnerability stems from improper error handling within the DSA Felix driver's memory allocation and cleanup routines. When the felix_setup_mmio_filtering function processes switch configuration parameters, it fails to execute proper resource deallocation sequences if the CPU port definition is absent. This memory leak occurs because allocated memory structures used for MMIO filtering operations are not freed when the conditional logic determines that no CPU port exists to utilize these resources. The vulnerability was identified through static analysis tools that detected resource leaks in the codebase, specifically flagged by Coverity ID 1492897 and 1492899, which are categorized under resource leak patterns typical of CWE-404 (Improper Resource Release or Cleanup) and CWE-772 (Missing Release of Resource after Effective Lifetime). The flaw demonstrates a failure in the kernel's memory management subsystem to properly handle edge cases in hardware configuration scenarios.
The operational impact of this memory leak vulnerability extends beyond simple resource consumption issues to potentially affect network switch functionality and overall system stability. In environments where DSA-based switches are heavily utilized, particularly in enterprise networking or data center deployments, the progressive memory consumption could lead to system slowdowns, memory exhaustion, or even system crashes under sustained load conditions. The vulnerability is particularly concerning in embedded systems or network appliances where memory resources are constrained and continuous operation is critical. From an attacker perspective, while this represents a denial-of-service vector rather than a direct exploitation path, it could be leveraged to create persistent resource exhaustion conditions that degrade network performance or availability. The vulnerability affects systems running Linux kernel versions prior to the patch release that addressed this specific memory management issue.
Mitigation strategies for CVE-2021-47513 primarily involve applying the appropriate kernel security patches released by the Linux kernel development team. System administrators should prioritize updating their kernel versions to include the fix that properly implements resource cleanup routines in the felix_setup_mmio_filtering function. Organizations should conduct thorough testing of kernel updates in non-production environments to ensure compatibility with existing network switch configurations and hardware. Monitoring systems should be implemented to track memory usage patterns and identify potential resource leak conditions before they escalate to system performance issues. Additionally, administrators should review their DSA switch configurations to ensure proper CPU port definitions are established, as this prevents the code path that triggers the memory leak condition. The fix aligns with ATT&CK technique T1499.004 (Endpoint Denial of Service) and addresses the underlying resource management failure that could be exploited to create persistent system degradation conditions. Regular security audits of kernel components and proactive patch management practices are essential for maintaining system integrity and preventing exploitation of similar memory leak vulnerabilities in network subsystems.