Linux users and administrators, listen up! A new vulnerability, CVE-2024-26948, was discovered and fixed in the Linux kernel’s AMD graphics driver (DRM/AMD/Display). This exposure could lead to a kernel panic or even system compromise if exploited. In this post, we'll break down the issue, show you the patch, discuss potential exploitation, and give original references for a deep dive.

What Is CVE-2024-26948?

This CVE covers a bug in the AMD display stack (part of the open source AMDGPU kernel module) – specifically in the dc_state_release function. Here, the code did not check if a pointer (state) was NULL before trying to release/free it, which might result in a NULL pointer dereference and crash.

The Story In Short

- File: drivers/gpu/drm/amd/display/dc/core/dc.c (and related files)

Technical Details

Here’s what was happening. The dc_state_release function was called and assumed the state pointer was always valid. If it was actually NULL (not pointing to memory as expected), then accessing or freeing it made the kernel crash.

Vulnerable Code (Before Patch)

void dc_state_release(struct dc_state *state)
{
    if (state->refcount == )
        kfree(state);
}

If state is NULL, state->refcount will result in a kernel Oops.

Fixed Code (After Patch)

void dc_state_release(struct dc_state *state)
{
    if (!state)
        return;
    if (state->refcount == )
        kfree(state);
}

Now, the function returns immediately if state is NULL, avoiding the crash.

Why Does This Matter?

Any attacker (or even a buggy program) with access to the graphics stack and the ability to manipulate display states could potentially trigger a system crash or exploit this in combination with other bugs. While direct remote code execution is unlikely, local denial-of-service (crash) is definite, and privilege escalation is possible in clever scenarios.

Exploiting CVE-2024-26948 (Proof-of-Concept)

*Disclaimer: This is for educational purposes and system administrators!*

Let’s look at how an attacker might crash your system using this bug.

Exploit Path

1. Prepare environment: Get access to a system running a vulnerable kernel with AMD GPU and unpatched code.
2. Trigger the bug: Find a way (maybe via a userspace driver call or a custom app) to cause the dc_state_release function to be called with a NULL pointer.

Example Pseudo-code (What Would Happen)

struct dc_state *state = NULL;
dc_state_release(state); // Without NULL check, kernel panics

If an attacker influences the state variable (possibly using buggy userland code or specially crafted calls via /dev/dri/card*), this function could be called with NULL, leading to a system crash.

*Note: Real-world exploitation would require a bit more knowledge about the state management in the DRM stack and possible tricking of the kernel into calling release with NULL, but the code path exists and was fixed for a reason!*

Check Your Kernel

uname -r

Check For Patches

Search your distro’s security tracker for CVE-2024-26948 or visit:

- NVD – National Vulnerability Database – CVE-2024-26948
- Upstream Patch (LKML)
- AMD official security advisories

If you build your own kernel: Apply the patch.

+    if (!state)
+        return;

Final Thoughts

While to many this bug seems like a minor oversight, in the world of kernel security, NULL pointer dereferences can lead to system instability and sometimes even root access (in rare, chained scenarios). If you are running any AMD-powered Linux system, make sure your kernel is up to date!

References

- LKML Commit Resolving CVE-2024-26948
- NVD Entry for CVE-2024-26948
- Arch Linux Security Advisory *(Search for CVE-2024-26948)*
- AMD Security Updates

Summary

CVE-2024-26948 shows how small mistakes in kernel code can have big consequences. Stay safe—update your systems regularly and monitor vendor security announcements! If you’re running AMD graphics, check today.

Timeline

Published on: 05/01/2024 06:15:10 UTC
Last modified on: 05/04/2025 09:00:28 UTC