CVE-2023-52461 - Linux Kernel DRM/SCHED Vulnerability Patched: Preventing Exploits from Malformed Entities

Introduction: A new vulnerability has been discovered in the Linux kernel, specifically in the drm/sched module. To ensure system security and stability, it is crucial to understand and mitigate this vulnerability.

Vulnerability Overview: CVE-2023-52461

The vulnerability in question exists in the Direct Rendering Manager (DRM) subsystem's scheduling component (drm/sched). It involves an issue when processing a malformed entity during the initialization of a DRM scheduler entity (drm_sched_entity_init). When given an out-of-bounds priority value, the affected function fails to adequately limit the value, potentially leading to further issues.

As a brief overview, the DRM subsystem in the Linux kernel is responsible for managing access to graphics hardware. The scheduler component (drm/sched) is vital for the efficient management of tasks in this subsystem, so any vulnerability could have widespread implications.

Exploit Details

To exploit this vulnerability, an attacker would need to pass a malformed entity with an out-of-bounds priority value to the drm_sched_entity_init function. Although this should not happen during normal operation, it is important to validate and handle any unexpected input.

Once the malformed entity is passed to the function, the improper bounds limiting could lead to a variety of unintended or malicious side effects. Some potential risks include denial of service attacks, unauthorized system access, or arbitrary code execution.

Code Snippet

Below is a code snippet that highlights the issue in question. Note the faulty expression in the original code (highlighted with a comment):

void drm_sched_entity_init(struct drm_sched_entity *entity,
...
{
        ...
        if (prio < DRM_SCHED_PRIORITY_MIN || prio > DRM_SCHED_PRIORITY_MAX)
                prio = DRM_SCHED_PRIORITY_NORMAL;
        ...
}

The fix is as simple as altering the condition that checks the bounds of the priority value. The corrected code snippet is as follows:

void drm_sched_entity_init(struct drm_sched_entity *entity,
...
{
        ...
        if (prio < DRM_SCHED_PRIORITY_MIN)
                prio = DRM_SCHED_PRIORITY_MIN;
        else if (prio > DRM_SCHED_PRIORITY_MAX)
                prio = DRM_SCHED_PRIORITY_MAX;
        ...
}

With this change, the priority value of a malformed entity will be properly limited to an allowed value, preventing exploitation of the vulnerability.

Original References

To learn more about this vulnerability, consult the official Linux kernel mailing list message by Kieran Bingham which details the issue and its resolution: Patch: drm/sched: Fix bounds limiting when given a malformed entity

For additional information on the Linux DRM subsystem and the scheduling component, consult the following resources:

- Linux DRM documentation
- drm/sched - Linux kernel source code

Conclusion

Stay vigilant for potential threats by keeping your Linux kernel up-to-date and understanding new vulnerabilities and their implications, such as CVE-2023-52461. By applying the proper patches and understanding how these vulnerabilities work, you can substantially reduce the risk of your systems being compromised.

Timeline

Published on: 02/23/2024 15:15:08 UTC
Last modified on: 02/23/2024 16:14:43 UTC