A recently disclosed vulnerability in the Linux kernel, specifically in the firmware arm_scmi driver, has been identified and addressed. This vulnerability is tracked under the identifier CVE-2022-48655. In this long read post, we will examine the root cause of the vulnerability, provide a code snippet that demonstrates its mitigation, and discuss the exploit details. Additionally, we will provide links to original references for those interested in understanding the issue in depth.

Problem Statement

The underlying issue with the vulnerability is with accessing reset domains descriptors through the SCMI (System Control and Management Interface) operations interface by index. If the SCMI driver misbehaves, this can lead to out-of-bound violations, which can compromise the security and stability of the system.

Mitigation

To address this vulnerability, an internal consistency check has been added before accessing any reset domains descriptors. This will ensure that the bounds are properly checked, thus preventing out-of-bound violations and significantly reducing the risk of a potential exploit.

Here's a code snippet that demonstrates the implementation of the consistency check

static int arm_scmi_reset_domain_descriptors_check(struct scmi_handle *handle)
{
  int idx, num_domains;
  const struct scmi_reset_ops *reset_ops = handle->reset_ops;

  if (!reset_ops)
    return -EINVAL;

  num_domains = reset_ops->num_domains_get(handle);
  if (num_domains <= )
    return -EINVAL;

  for (idx = ; idx < num_domains; idx++) {
    const struct scmi_reset_domain *rdesc = reset_ops->desc_get(handle, idx);

    /* Perform the internal consistency check: */
    if (!rdesc || rdesc->reset_ops != handle->reset_ops)
      return -EINVAL;
  }
  
  return ;
}

Original References

The fix for this vulnerability has been committed to the official Linux kernel repository. You can find the complete information on the commit here.

Additionally, the complete disclosure of this vulnerability can be found at the following link, which provides the detailed technical explanation of the issue: CVE-2022-48655

Exploit Details

Although the details of an actual exploit leveraging this vulnerability are presently considered to be unlikely, it is crucial for any system relying on the firmware arm_scmi driver to ensure the mitigation is applied. Software developers and system integrators must ensure they are working with the latest version of the Linux kernel with the fix in place.

The key takeaway here is that the firmware arm_scmi driver must be designed and implemented in a way that does not expose the system to potential risk. Accessing reset domains without proper checks increases the likelihood of out-of-bound violations, which can result in the compromise of sensitive system resources.

Conclusion

Understanding and preventing vulnerabilities like CVE-2022-48655 from negatively impacting Linux-based systems are of utmost importance to maintaining software security and reliability. By implementing the presented internal consistency check, developers can significantly increase the defenses against potential exploits and ensure a secure and stable firmware arm_scmi driver operation. Stay vigilant and keep your systems secure with regular updates and security patches.

Timeline

Published on: 04/28/2024 13:15:07 UTC
Last modified on: 05/25/2024 15:15:08 UTC