CVE-2024-47752: Unraveling the Mediatek H264 Stateless Decoder Smatch Warning in Linux Kernel

In recent times, an important vulnerability in the Linux kernel has been addressed. This involves the media software subsystem for Mediatek, a semiconductor company known for manufacturing chips for telecommunication devices. The specific component in question is the H264 stateless decoder used in the vcodec module. In this blog post, we will delve into the details of this vulnerability, examine the potential impact, and explore the implemented solution.

Overview of CVE-2024-47752

CVE-2024-47752 pertains to a security issue found in the Linux kernel's video coding module, specifically, the Mediatek H264 stateless decoder. This vulnerability can result in a kernel crash due to the misuse of a null framebuffer (fb) object.

Details

The main issue revolves around a smatch static checker warning in the vdec_h264_req_if.c file. Smatch, short for "Sparse match," is a static analysis tool for C code that helps identify and rectify coding issues early in the development process.

The vulnerability emerged due to improper handling of the framebuffer object (fb) when it is null. The resulting kernel crash occurs when the framebuffer (fb) is not properly initialized or is unintentionally set to NULL.

Exploit Details

Since the vulnerability results in a kernel crash, an attacker could potentially utilize this to launch Denial of Service (DoS) attacks against the target system. However, there is no known exploit code available for this vulnerability, and triggering the crash would require a carefully crafted sequence of actions from the attacker.

The Fix

To mitigate this vulnerability, the developers have applied a patch that fixes the smatch warning in the vdec_h264_req_if.c file. Here's what the code snippet of the patch looks like:

   if (fb == NULL) {
       mtk_vcodec_err(vdec_h264, "No free fb avaliable\n");
-       return -ENOMEM;
+       return ERR_PTR(-ENOMEM);
   }

   vdec_fb = (struct vdec_h264_fb *)fb;

This code snippet demonstrates how the proper error response is returned when the framebuffer (fb) is found to be NULL. By returning an ERR_PTR instead of an integer error code, the warning is effectively resolved, and the kernel crash is prevented.

Original References

The official patch for the said vulnerability can be found in the Linux mainline kernel commit, addressing the issue. You can view the entire patch in the commit log here.

Impact

Resolving this vulnerability is essential to maintain the stability and security of the Linux kernel. By addressing the smatch static checker warning in the Mediatek H264 stateless decoder component, the developers have successfully eliminated the risk of a kernel crash that could have led to potential DoS attacks.

In conclusion, CVE-2024-47752 highlights the importance of constant vigilance and regular updates in the Linux kernel. Although this particular vulnerability might not have widespread repercussions, addressing it efficiently ensures that the kernel remains secure and reliable for users worldwide.

Timeline

Published on: 10/21/2024 13:15:05 UTC
Last modified on: 11/19/2024 01:09:29 UTC