CVE-2024-27029: Getting to Know the Fixed Linux Kernel Vulnerability - drm/amdgpu: fix mmhub client id out-of-bounds access

A new security vulnerability, CVE-2024-27029, has been identified within the Linux kernel's DRM (Direct Rendering Manager) subsystem, specifically in the AMD Graphics (amdgpu) driver. This vulnerability caused the possibility of out-of-bounds access in MMHUB (Memory Management Hub) client id, which could have led to potential security breaches. Thankfully, this issue has now been resolved with a patch that properly handles client id x140.

In this post, we'll explore the details of this vulnerability, review the code changes that were made to fix it, and provide links to the original references for further understanding. Let's dive right in!

Background

The Linux kernel's Direct Rendering Manager (DRM) subsystem is responsible for managing graphics hardware. The AMD GPU driver, known as amdgpu, is a part of the DRM subsystem. Within the amdgpu driver, the MMHUB (Memory Management Hub) client id is utilized to manage graphics memory resources.

The Vulnerability

An out-of-bounds access vulnerability (CVE-2024-27029) was identified within the Linux kernel'samdgpu driver. This vulnerability could lead to potential security breaches due to improper handling of the MMHUB client id, specifically client id x140. An attacker with local access could exploit this vulnerability to potentially access unauthorized memory locations or execute arbitrary code.

Here's an excerpt of the original, problematic code

#define AMDGPU_MMHUB_CID(id) (x100 | ((id) & x3f))
...

static inline bool amdgpu_is_valid_mmhub_cid(struct amdgpu_device *adev, u16 id) {
	return ((id >= x100 && id < x140));
}

The Fix

The developers at the Linux project acted promptly to fix this vulnerability by properly handling the MMHUB client id x140. The code was updated to ensure that the out-of-bounds access was no longer possible, preventing potential security breaches or unauthorized memory access.

Here's the code snippet that showcases the fix

#define AMDGPU_MMHUB_CID(id) (x100 | ((id) & x3f))
...

static inline bool amdgpu_is_valid_mmhub_cid(struct amdgpu_device *adev, u16 id) {
	return ((id >= x100 && id <= x140));
}

As you can see, the fix merely involves changing the comparison operator from < to <=, ensuring client id x140 is also properly handled.

Original References

For more information on this vulnerability and the patch details, you can refer to the following official sources:

- Linux Kernel Mailing List (LKML) discussion
- Linux Kernel Git commit for the patch

Conclusion

CVE-2024-27029 highlights the importance of the open-source community's vigiliance and quick response when it comes to identifying and fixing vulnerabilities within complex software systems like the Linux kernel. The prompt resolution of this MMHUB client id out-of-bounds access issue within the amdgpu driver helps maintain the security and integrity of the Linux operating system for millions of users worldwide.

Timeline

Published on: 05/01/2024 13:15:49 UTC
Last modified on: 12/23/2024 19:33:28 UTC