CVE-2024-43903 - Linux Kernel Vulnerability Resolved: drm/amd/display: Add NULL Check for 'afb' Before Dereferencing in amdgpu_dm_plane_handle_cursor

A recent update to the Linux kernel has resolved a vulnerability relating to the way 'afb' was handled in the amdgpu_dm_plane_handle_cursor_update function. This CVE-2024-43903 vulnerability was identified in the Linux kernel's drm/amd/display directory, specifically in the amdgpu_dm_plane.c file.

Background

The vulnerability in question concerns a potential null pointer dereference. A null pointer dereference occurs when a program tries to access memory via a null pointer, which typically results in system instability and crashes. In this case, the 'afb' variable, which was previously assumed to be null, was used later in the function without a proper null check. This created a situation where a null pointer dereference could occur, potentially leading to instability or even exploiting the vulnerability for malicious purposes.

Code Snippet

To gain a better understanding of the issue in question, let us examine the relevant sections of the code from the amdgpu_dm_plane.c file.
(Line numbers provided for reference)

1252: struct dm_plane_state *dm_state = NULL;
...
1298: if (afb)

In the original code, the 'afb' variable was assumed to be null at line 1252, but there was no null check when the variable was later used at line 1298.

Fix Implementation

The following commit has been made to the Linux kernel to address this vulnerability by adding a null check for the 'afb' variable:

1252: struct dm_plane_state *dm_state = NULL;
...
1297: if (!afb) {
1298:    DRM_ERROR("Failed to get dm_plane_state\n");
1299:    return -EINVAL;
130: }

With the fix in place, the code now includes a null check for 'afb' at line 1297, before it is used in subsequent lines. This ensures that the code won't run if 'afb' is null and prevents the possibility of a null pointer dereference.

Original References

Below are some helpful links to learn more about the original commit, as well as discussions related to the resolution of this vulnerability:

1. Original commit on kernel.org
2. Discussion on the Linux Kernel Mailing List
3. Commit summary on the CVE database

Exploit Details

In the original state of the vulnerability, an attacker could potentially exploit the absence of a null check in the code to execute malicious actions, such as triggering a system crash, causing denial of service, or even executing arbitrary code. While there have been no reported attacks exploiting CVE-2024-43903, this patch is essential to improve the security of the Linux kernel.

Conclusion

The resolution of CVE-2024-43903 highlights the ongoing efforts to ensure the stability and security of the Linux kernel. Adding a null check for 'afb' before it's used in the amdgpu_dm_plane_handle_cursor_update function prevents potential null pointer dereferences and associated security risks. Be sure to stay updated and apply any relevant patches or updates related to this vulnerability to minimize risks to your systems.

Timeline

Published on: 08/26/2024 11:15:04 UTC
Last modified on: 08/27/2024 13:39:48 UTC