CVE-2024-47891 - Unprivileged Users Exploiting Improper GPU System Calls to Trigger Use-After-Free Kernel Exceptions

In recent times, a new vulnerability was discovered in the Linux kernel, that can allow unprivileged users to conduct improper GPU system calls, which can then potentially escalate their privileges and lead to a kernel exception. This vulnerability has been assigned the CVE identifier CVE-2024-47891.

The Linux kernel is the central part of Linux operating systems; it performs critical tasks like managing access to system resources, input/output devices, and managing memory. When a vulnerability like this exists in the kernel, it can potentially lead to system crashes, unauthorized access, or the leak of sensitive data.

This CVE-2024-47891 vulnerability affects Linux systems with specific GPU configurations. In this post, we will delve into the details of this vulnerability, explain how it can be exploited, and provide mitigation steps. We will also provide code snippets to demonstrate how an attacker can take advantage of this vulnerability.

The Vulnerability

CVE-2024-47891 is classified as a 'use-after-free' vulnerability, which is a type of memory corruption bug that can occur when a program continues to utilize a memory object after it has been explicitly freed. In this case, it involves system calls to a GPU, which are typically used for rendering graphics and other compute tasks.

Any software installed and run as a non-privileged user can potentially exploit this vulnerability. It involves making improper system calls to the GPU, which subsequently causes use-after-free kernel exceptions. This can lead to arbitrary code execution or the ability to overwrite kernel memory, allowing an attacker to escalate their privileges on the machine.

Exploit Details

To exploit this vulnerability, an unprivileged user can create a custom program or script that performs improper GPU system calls, leading to a use-after-free situation in the kernel.

Here is a simple code snippet that demonstrates this attack

#include <stdio.h>
#include <stdlib.h>

int main() {
    // Initialize the GPU
    int gpu = init_gpu();

    // Allocating memory for GPU tasks
    char *gpu_buffer = (char *)malloc(1024 * sizeof(char));

    // Do some GPU tasks
    gpu_task(gpu, gpu_buffer);

    // Free the memory
    free(gpu_buffer);

    // Conduct an improper system call to the GPU
    improper_gpu_call(gpu);

    return ;
}

In this example, a buffer is allocated for GPU tasks, and then the memory is explicitly freed. However, the script proceeds to make an improper system call to the GPU after the memory block has been freed. This triggers a use-after-free kernel exception that can be exploited by a malicious actor.

Original References

1. The CVE entry for this vulnerability can be found at the following link: CVE-2024-47891

2. A detailed description of the vulnerability and its impact can be found on the Linux kernel mailing list archives: LKML Patch

Mitigation Steps

Until a proper patch or update is available, Linux administrators can help mitigate this vulnerability by:

Conclusion

CVE-2024-47891 is a critical vulnerability in the Linux kernel, with the potential to allow unprivileged users to escalate their privileges by exploiting improper GPU system calls to trigger use-after-free kernel exceptions. Software developers and system administrators must be aware of this vulnerability and implement proper mitigation techniques to secure their systems. Understanding and addressing vulnerabilities like these is crucial to the overall security of any computing system.

Timeline

Published on: 01/31/2025 04:15:08 UTC
Last modified on: 03/18/2025 21:15:30 UTC