CVE-2021-47050 in Linux
Summary
by MITRE • 02/28/2024
In the Linux kernel, the following vulnerability has been resolved:
memory: renesas-rpc-if: fix possible NULL pointer dereference of resource
The platform_get_resource_byname() can return NULL which would be immediately dereferenced by resource_size(). Instead dereference it after validating the resource.
Addresses-Coverity: Dereference null return value
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Analysis
by VulDB Data Team • 12/09/2024
The vulnerability identified as CVE-2021-47050 represents a critical NULL pointer dereference issue within the Linux kernel's Renesas RPC IF memory management subsystem. This flaw exists in the platform device resource handling mechanism where the platform_get_resource_byname() function may return a NULL pointer under certain conditions. When this NULL value is subsequently passed to resource_size() function without proper validation, the kernel experiences an immediate dereference operation that leads to system instability and potential crash conditions. The vulnerability specifically impacts systems utilizing Renesas RPC IF drivers where platform resources are dynamically allocated and managed through the kernel's device model framework.
The technical implementation of this vulnerability stems from improper error handling in the resource management pathway. The platform_get_resource_byname() function is designed to retrieve specific platform resources by their name identifier but can legitimately return NULL when the requested resource is not available or cannot be located within the device tree configuration. The kernel code fails to validate this return value before proceeding to call resource_size() which expects a valid resource structure pointer. This pattern violates fundamental defensive programming principles and creates a direct path for kernel panic conditions when the dereference operation attempts to access memory locations that do not exist. The issue manifests as a classic null pointer dereference scenario that aligns with CWE-476 which specifically addresses NULL pointer dereference vulnerabilities in software systems.
The operational impact of CVE-2021-47050 extends beyond simple system crashes to potentially enable denial of service conditions that could affect embedded systems and industrial control platforms running on Renesas hardware. Systems utilizing the affected kernel versions may experience unexpected reboots or system hangs when platform devices attempt to initialize their memory resources, particularly in configurations where device tree entries are incomplete or misconfigured. This vulnerability is particularly concerning for automotive applications, industrial automation systems, and embedded network devices that rely on the Renesas RPC IF interface for memory management operations. The exploitability of this issue is relatively straightforward as it requires only the presence of a platform device that triggers the problematic resource retrieval path, making it a significant concern for kernel maintainers and system administrators managing embedded Linux deployments.
Mitigation strategies for CVE-2021-47050 focus on implementing proper input validation and defensive programming practices within the kernel's platform device resource handling code. The recommended fix involves adding explicit NULL pointer checks immediately after calling platform_get_resource_byname() before proceeding with any operations that depend on the resource structure. This approach aligns with ATT&CK technique T1499.004 which emphasizes the importance of preventing system resource exhaustion and invalid memory access patterns. Kernel developers should implement comprehensive error handling that validates all function return values, particularly those from platform device management APIs, and ensures that downstream operations only proceed when valid resource structures are available. System administrators should prioritize applying the patched kernel versions that contain the proper validation logic and monitor for any unusual system behavior that might indicate exploitation attempts. The fix also reinforces best practices outlined in the Linux kernel coding guidelines that mandate proper error handling for all resource management operations to prevent similar vulnerabilities from emerging in other subsystems.