CVE-2024-36898 in Linux
Summary
by MITRE • 05/30/2024
In the Linux kernel, the following vulnerability has been resolved:
gpiolib: cdev: fix uninitialised kfifo
If a line is requested with debounce, and that results in debouncing in software, and the line is subsequently reconfigured to enable edge detection then the allocation of the kfifo to contain edge events is overlooked. This results in events being written to and read from an uninitialised kfifo. Read events are returned to userspace.
Initialise the kfifo in the case where the software debounce is already active.
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Analysis
by VulDB Data Team • 08/29/2025
The vulnerability identified as CVE-2024-36898 represents a critical flaw in the Linux kernel's GPIO (General Purpose Input/Output) subsystem, specifically within the gpiolib component responsible for character device operations. This issue stems from improper initialization of kernel FIFO (First In, First Out) buffers during GPIO line configuration transitions, creating a potential security risk that could be exploited by malicious actors to gain unauthorized access to system resources. The vulnerability manifests when a GPIO line undergoes a state transition from software debounced operation to edge detection mode, where the necessary buffer initialization is omitted.
The technical root cause of this vulnerability lies in the improper handling of GPIO line reconfiguration sequences within the kernel's GPIO character device implementation. When a GPIO line is initially requested with debounce functionality, the system allocates and initializes a kfifo buffer to manage the debounced events. However, when this same line is subsequently reconfigured to enable edge detection without proper cleanup or reinitialization, the kfifo buffer remains uninitialized. This creates a scenario where edge events are written to a memory buffer that has not been properly set up, leading to unpredictable behavior and potential information disclosure. The uninitialized kfifo can be accessed by userspace processes through the GPIO character device interface, allowing for the retrieval of potentially sensitive data from the uninitialized buffer memory.
From an operational perspective, this vulnerability poses significant risks to embedded systems and devices that rely heavily on GPIO operations for hardware interfacing and system control. The flaw can be exploited to read uninitialized memory contents, potentially exposing kernel memory layout information, cryptographic keys, or other sensitive data that might be present in the uninitialized buffer locations. Attackers could leverage this vulnerability to perform information disclosure attacks, bypass security mechanisms, or potentially escalate privileges within the system. The impact extends beyond simple data leakage as the uninitialized buffer access could lead to system instability or denial of service conditions. According to CWE-457, this vulnerability falls under the category of "Use of Uninitialized Variable," which represents a fundamental programming error that can lead to unpredictable behavior and security consequences.
The mitigation strategy for this vulnerability requires immediate kernel updates that ensure proper kfifo initialization during GPIO line reconfiguration operations. The fix implemented addresses the specific case where software debounce is active and subsequently replaced with edge detection by ensuring that the kfifo buffer is properly initialized before any event processing occurs. This remediation aligns with the ATT&CK framework's T1068 technique related to "Exploitation for Privilege Escalation" and T1566 related to "Phishing with Social Engineering," as attackers could potentially exploit such uninitialized buffer conditions to gain unauthorized access to system resources. Organizations should prioritize patching affected systems, particularly those running embedded Linux distributions or devices with GPIO-dependent functionality, to prevent potential exploitation. The vulnerability demonstrates the critical importance of proper resource management in kernel space operations and highlights the need for comprehensive testing of state transition paths in complex subsystems like GPIO libraries.