CVE-2024-49941 in Linux
Summary
by MITRE • 10/21/2024
In the Linux kernel, the following vulnerability has been resolved:
gpiolib: Fix potential NULL pointer dereference in gpiod_get_label()
In `gpiod_get_label()`, it is possible that `srcu_dereference_check()` may return a NULL pointer, leading to a scenario where `label->str` is accessed without verifying if `label` itself is NULL.
This patch adds a proper NULL check for `label` before accessing `label->str`. The check for `label->str != NULL` is removed because `label->str` can never be NULL if `label` is not NULL.
This fixes the issue where the label name was being printed as `(efault)` when dumping the sysfs GPIO file when `label == NULL`.
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Analysis
by VulDB Data Team • 03/18/2026
The vulnerability identified as CVE-2024-49941 resides within the Linux kernel's GPIO (General Purpose Input/Output) subsystem, specifically in the gpiolib component that manages GPIO descriptor operations. This issue represents a classic null pointer dereference flaw that could potentially lead to system instability or information disclosure. The vulnerability manifests in the gpiod_get_label() function which is responsible for retrieving and returning GPIO label information through the sysfs interface. When examining the code flow, the problem occurs during the execution of srcu_dereference_check() which may return a NULL pointer under certain conditions, creating a dangerous scenario where subsequent code attempts to access members of a null structure without proper validation.
The technical flaw stems from inadequate null pointer validation within the GPIO label retrieval mechanism. The srcu_dereference_check() function, which is designed to safely dereference pointers in a SRCU (Sleepable Read-Copy Update) context, can legitimately return NULL values when GPIO labels are not properly initialized or when the underlying GPIO descriptor structure has been freed. The vulnerability occurs because the code does not properly validate that the returned label structure from srcu_dereference_check() is not NULL before proceeding to access label->str. This oversight creates a path where the kernel attempts to read from memory locations that may not contain valid data, potentially causing a kernel oops or system crash. According to CWE-476, this represents a NULL Pointer Dereference vulnerability where the program attempts to access a member of a NULL pointer, which is a fundamental security flaw that can be exploited to cause system instability or potentially gain unauthorized access to kernel memory.
The operational impact of this vulnerability extends beyond simple system crashes, as it can affect the reliability of GPIO-based device drivers and system diagnostics. When the sysfs GPIO interface is accessed to dump GPIO information, the kernel's handling of NULL labels results in misleading output where label names appear as "(efault)" instead of proper null representation. This behavior can confuse system administrators and automated monitoring tools that rely on accurate GPIO label information for device management and debugging purposes. The vulnerability is particularly concerning in embedded systems or server environments where GPIO interfaces are heavily used for hardware control and monitoring. From an ATT&CK framework perspective, this vulnerability could be leveraged in a privilege escalation scenario if an attacker can manipulate GPIO descriptors to trigger the null pointer dereference, potentially leading to kernel memory corruption and system compromise.
The fix implemented for CVE-2024-49941 addresses the root cause by introducing a proper NULL check for the label pointer before any member access occurs. This defensive programming approach ensures that the code explicitly verifies label = NULL since this check becomes meaningless when the parent label structure itself is already validated as non-null. The solution aligns with standard kernel security practices and follows the principle of defensive programming where all pointer dereferences are validated before use. This type of fix is particularly important in kernel space where memory safety violations can lead to complete system compromise, and where the kernel's SRCU mechanism requires careful handling of pointer validity to maintain system integrity. The patch demonstrates proper error handling and memory safety practices that are essential for maintaining the stability and security of kernel subsystems that interact with hardware interfaces.