CVE-2024-44931 in Linux
Summary
by MITRE • 08/26/2024
In the Linux kernel, the following vulnerability has been resolved:
gpio: prevent potential speculation leaks in gpio_device_get_desc()
Userspace may trigger a speculative read of an address outside the gpio descriptor array. Users can do that by calling gpio_ioctl() with an offset out of range. Offset is copied from user and then used as an array index to get the gpio descriptor without sanitization in gpio_device_get_desc().
This change ensures that the offset is sanitized by using array_index_nospec() to mitigate any possibility of speculative information leaks.
This bug was discovered and resolved using Coverity Static Analysis Security Testing (SAST) by Synopsys, Inc.
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Analysis
by VulDB Data Team • 10/04/2024
The vulnerability CVE-2024-44931 represents a critical speculative execution flaw within the Linux kernel's GPIO subsystem that could potentially expose sensitive information through side-channel attacks. This issue specifically affects the gpio_device_get_desc() function which handles GPIO descriptor lookups for user-space applications. The vulnerability arises from inadequate input validation when processing GPIO ioctl commands, creating a pathway for malicious users to trigger speculative reads beyond the bounds of allocated memory arrays. The flaw exists in the kernel's handling of user-provided offsets that are directly used as array indices without proper sanitization, making it susceptible to speculative execution attacks that could leak information from adjacent memory locations.
The technical implementation of this vulnerability stems from the absence of proper bounds checking in the gpio_device_get_desc() function where user-supplied offsets are copied from user-space and immediately used as array indices to access GPIO descriptor structures. This pattern creates a speculative execution path where the CPU's out-of-order execution engine may speculatively read memory locations beyond the intended array bounds before the actual bounds check occurs. The vulnerability is particularly dangerous because it leverages the kernel's speculative execution capabilities to potentially expose sensitive data that might be stored in memory adjacent to the GPIO descriptor array, including cryptographic keys, passwords, or other confidential information that could be accessed through cache timing attacks or similar side-channel techniques.
The operational impact of CVE-2024-44931 extends beyond simple information disclosure, as it represents a fundamental security weakness in the kernel's memory access controls that could be exploited by malicious actors with local privileges or through carefully crafted ioctl calls. Attackers could potentially use this vulnerability to extract sensitive data from kernel memory, undermining the security guarantees provided by the kernel's memory protection mechanisms. The vulnerability affects all systems running Linux kernels that implement the GPIO subsystem and have user-space applications that make GPIO ioctl calls with out-of-bounds offsets. This creates a significant risk for embedded systems, servers, and devices where GPIO interfaces are exposed to untrusted users or applications, as these systems may be vulnerable to information leakage attacks that could compromise the confidentiality of sensitive kernel data.
The resolution for CVE-2024-44931 implements a defensive programming technique using the array_index_nospec() function to sanitize user-provided offsets before they are used as array indices. This approach prevents speculative execution from accessing memory locations beyond the intended array bounds by ensuring that the offset values are properly validated and sanitized before being used in memory access operations. The fix demonstrates the importance of applying security best practices such as those recommended by the CWE (Common Weakness Enumeration) standard 129, which addresses improper validation of array indices, and aligns with ATT&CK techniques related to privilege escalation through kernel vulnerabilities. The vulnerability was identified through static analysis using Coverity SAST tools, highlighting the critical role of automated security testing in identifying speculative execution vulnerabilities that may not be apparent through traditional dynamic testing methods. This resolution reinforces the need for kernel developers to implement robust input validation and memory access controls to prevent speculative execution attacks that could compromise system security.