CVE-2022-48907 in Linux
Summary
by MITRE • 08/22/2024
In the Linux kernel, the following vulnerability has been resolved:
auxdisplay: lcd2s: Fix memory leak in ->remove()
Once allocated the struct lcd2s_data is never freed. Fix the memory leak by switching to devm_kzalloc().
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Analysis
by VulDB Data Team • 09/13/2024
The vulnerability identified as CVE-2022-48907 represents a memory leak within the Linux kernel's auxiliary display subsystem, specifically affecting the lcd2s driver component. This flaw resides in the device removal function where allocated memory structures fail to be properly deallocated, creating a persistent memory consumption issue that can degrade system performance over time. The lcd2s driver is responsible for controlling liquid crystal displays through auxiliary display interfaces, making this vulnerability particularly concerning for embedded systems and devices with limited memory resources where such leaks can quickly lead to system instability or resource exhaustion.
The technical implementation flaw stems from improper memory management within the driver's ->remove() function which handles device cleanup operations. When the lcd2s device is removed from the system, the allocated struct lcd2s_data structure remains in memory without being freed, resulting in a memory leak that accumulates with each device removal and re-addition cycle. This pattern violates fundamental memory management principles and represents a classic example of resource leak vulnerabilities that can be categorized under CWE-404, which specifically addresses improper resource release or unmanaged resource consumption. The vulnerability demonstrates a failure in implementing proper device driver lifecycle management where allocated resources are not properly cleaned up during device removal operations.
The operational impact of this memory leak extends beyond simple resource wastage, potentially leading to system instability, performance degradation, and in severe cases, system crashes or lockups. When multiple lcd2s devices are present or when the driver is frequently loaded and unloaded, the accumulated memory consumption can significantly impact system performance and may eventually exhaust available memory resources. This vulnerability affects embedded systems and devices that rely heavily on auxiliary display functionality, particularly those in industrial control systems, automotive applications, and IoT devices where memory constraints are critical. The cumulative nature of the leak means that prolonged system operation can lead to progressive degradation of system responsiveness and reliability.
The mitigation strategy for CVE-2022-48907 involves implementing proper device-managed memory allocation through the use of devm_kzalloc() instead of the traditional kzalloc() function. This change ensures that memory allocated for the lcd2s_data structure is automatically freed when the device is removed, leveraging the kernel's device management framework to handle resource cleanup automatically. The fix aligns with the principle of using kernel-provided memory management helpers that integrate with the device model, following the ATT&CK technique of system binary modification where proper memory management practices are enforced. This approach not only resolves the immediate memory leak but also enhances the overall robustness of the driver by ensuring proper resource lifecycle management and preventing potential exploitation through resource exhaustion attacks that could be leveraged by malicious actors in compromised systems.