A fresh Linux kernel vulnerability identified as CVE-2024-26985 has been making waves in the open-source community. This long-read explores how the bug appeared in the drm/xe subsystem, what code was affected, what could be exploited, and how it was ultimately patched. As always, staying up to date with such kernel vulnerabilities is crucial — especially for those maintaining graphical hardware using Intel drivers.

What’s the Vulnerability?

CVE-2024-26985 is about a resource leak in the new Intel Xe DRM driver (drm/xe). Specifically, when initializing a framebuffer object, an error path could accidentally leak a reference to a buffer object (BO). Over time, that means the kernel would waste memory — a classic “memory leak” — that could become an attack vector or a system stability problem.

Here’s the key: improper reference counting led to the leak when framebuffer creation failed.

Original fix:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a2f3d731be3893e730417ae319076fcaffdf549

Let’s look at a *simplified* version of the buggy function, before it was fixed

int intel_fb_bo_framebuffer_init(struct drm_device *dev, ...) {
    struct xe_bo *bo = alloc_buffer_object(...);
    if (!bo)
        return -ENOMEM;
    ...
    if (error_condition) {
        // Ooops! No put_bo(bo), so BO leaked!
        return -EINVAL;
    }
    ...
    return ;
}

When error_condition is true, it returns early — but doesn’t *unreference* (free) bo. So that memory sticks around in the kernel forever. If you trigger this many times, you eventually run your system out of graphics memory — a denial of service risk.

Local Denial of Service

Given the leak, a local user with access to the graphics stack could *repeatedly* trigger the error path (for example, by abusing framebuffer creation with specially crafted parameters). Over time, these repeated allocations would never be cleaned up by the kernel, eating away at graphics or even general system memory — causing slowdown and instability, possibly a full system crash.

Example Exploit Concept

If you had privileges to use /dev/dri/cardX (typical for GUI users or sandboxed programs), you can write a script or program that creates many bogus framebuffers with invalid parameters:

// Pseudocode - do NOT use in production
for (int i = ; i < 10000; i++) {
    create_bad_framebuffer();
    // each call leaks memory in the driver
}

Eventually even the root user can’t allocate resources, and your X11/Wayland session could lock up. While this is *not* a remote exploit, it can be used by an unprivileged local user, making it a real concern for shared systems or multi-user servers with graphics enabled.

The Patch: How It Was Fixed

The maintainer fixed the bug with a simple but crucial change: properly unreferencing the bo in the error path and making the return status clearer.

Let’s look at a real excerpt from the patch commit:

Old code (buggy)

if (error) {
    return -EINVAL;
}

Fixed code

if (error) {
    xe_bo_put(bo);
    return -EINVAL;
}

That xe_bo_put(bo); call properly frees up the buffer and stops the leak.

Bonus:
The return value on success was made unambiguous (return ;), which helps with code clarity.

References

- CVE Detail page for CVE-2024-26985
- Linux kernel fix commit a2f3d731be3893e730417ae319076fcaffdf549
- X.Org security advisory

Should You Be Worried?

If you use an Intel GPU with the Xe driver in a multi-user desktop environment, you should absolutely patch.
Even single user systems could, in theory, be at risk if a malicious program is allowed to run graphical operations.

To stay safe:

Conclusion

CVE-2024-26985 is a reminder that even with careful code review, kernel memory management is perilous. A single missing put() can lead to serious security and stability consequences. Thanks to timely patching and open-source transparency, users can protect themselves by updating — but vigilance is always needed in graphics and kernel code.

Timeline

Published on: 05/01/2024 06:15:16 UTC
Last modified on: 11/04/2025 18:16:02 UTC