CVE-2024-42282 in Linux
Summary
by MITRE • 08/17/2024
In the Linux kernel, the following vulnerability has been resolved:
net: mediatek: Fix potential NULL pointer dereference in dummy net_device handling
Move the freeing of the dummy net_device from mtk_free_dev() to mtk_remove().
Previously, if alloc_netdev_dummy() failed in mtk_probe(), eth->dummy_dev would be NULL. The error path would then call mtk_free_dev(), which in turn called free_netdev() assuming dummy_dev was allocated (but it was not), potentially causing a NULL pointer dereference.
By moving free_netdev() to mtk_remove(), we ensure it's only called when mtk_probe() has succeeded and dummy_dev is fully allocated. This addresses a potential NULL pointer dereference detected by Smatch[1].
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Analysis
by VulDB Data Team • 02/01/2026
This vulnerability resides within the Linux kernel's network subsystem, specifically affecting the MediaTek ethernet driver implementation. The issue manifests as a potential NULL pointer dereference during device removal operations, representing a critical stability concern that could lead to system crashes or denial of service conditions. The vulnerability stems from improper handling of network device allocation and deallocation sequences within the driver's initialization and cleanup pathways.
The technical flaw occurs in the MediaTek ethernet driver's error handling logic where the dummy network device structure is not properly managed during failure conditions. During driver probe operations, if the alloc_netdev_dummy() function fails to allocate the dummy network device, the eth->dummy_dev pointer remains NULL. However, when the error path executes mtk_free_dev(), it attempts to call free_netdev() on what it assumes is a valid allocated structure, despite the fact that dummy_dev was never actually allocated. This fundamental mismatch between expected and actual memory allocation states creates the NULL pointer dereference condition that can crash the kernel.
The operational impact of this vulnerability extends beyond simple system instability, as it affects the reliability of network operations on devices utilizing MediaTek ethernet controllers. Attackers could potentially exploit this condition to cause system crashes, leading to denial of service scenarios that would disrupt network connectivity and potentially impact other system services dependent on stable network operations. The vulnerability is particularly concerning in embedded systems and network infrastructure devices where continuous operation is critical. According to CWE classification, this represents a CWE-476: NULL Pointer Dereference, which is a well-known software weakness pattern that has been documented in numerous security assessments and vulnerability reports.
The mitigation strategy involves restructuring the driver's cleanup logic to ensure proper conditional execution of deallocation functions. By moving the free_netdev() call from mtk_free_dev() to mtk_remove(), the driver ensures that deallocation only occurs when the dummy device has been successfully allocated and initialized. This approach follows the principle of defensive programming by validating resource states before attempting operations on them. The fix also aligns with established best practices for kernel module development, particularly regarding proper error handling and resource management. The solution addresses the specific conditions identified by the Smatch static analysis tool, which is commonly used for detecting potential kernel vulnerabilities and memory management issues. This remediation approach prevents the scenario where deallocation functions are called on uninitialized or failed allocation states, thereby maintaining system stability and preventing potential exploitation.
This vulnerability demonstrates the importance of careful resource management in kernel space programming and highlights how seemingly minor error handling flaws can lead to significant stability issues. The fix represents a straightforward but crucial correction that ensures proper lifecycle management of kernel network devices, particularly in scenarios involving partial initialization failures. The remediation approach also serves as a model for other kernel drivers facing similar resource management challenges, emphasizing the need for robust error handling and state validation in critical system components.