CVE-2022-30774: Exploring DMA Attacks on PnpSmm Driver's Parameter Buffer and Understanding the TOCTOU Vulnerability

In this in-depth analysis, we examine the vulnerability CVE-2022-30774, which exists in the parameter buffer used by the PnpSmm driver. This vulnerability revolves around a Time of Check to Time of Use (TOCTOU) attack scenario, in which an attacker can exploit Direct Memory Access (DMA) to change the contents of the parameter buffer after their values have been checked but before they are used.

This critical vulnerability was discovered by engineers at Insyde during a security review. Fortunately, it was promptly fixed in subsequent versions of the Kernel: 5.2: 05.27.29, 5.3: 05.36.25, 5.4: 05.44.25, 5.5: 05.52.25. Moreover, it has been documented as a Common Weakness Enumeration (CWE-367). This post delves into the details of the vulnerability, illuminates the code snippet and the attack vectors, and provides references to the original sources.

Code Snippet

// Vulnerable PnpSmm driver code
void PnpSmmProcessRequest(SMM_RESOURCE_REQUEST *Request) {
    // Check the parameters
    if (ParameterBufferIsValid(Request->ParameterBuffer)) {
        // DMA attack can be exploited here, potentially changing the contents
        // of the parameter buffer before it's used
        ExecuteRequest(Request->ParameterBuffer);
    }
}

Exploit Details

The vulnerability exists in a crucial part of the PnpSmm driver, where it processes resource allocation requests. The code contains a significant flaw in which an attacker can manipulate the contents of the parameter buffer using a DMA attack. This type of attack, known as a TOCTOU attack, can occur between the time the parameters are checked for validity and when they are actually being used by the system.

Attackers leveraging this vulnerability can potentially perform unauthorized actions, which could lead to unintended consequences like system crashes, data corruption, or even unauthorized access to sensitive information. In short, this vulnerability could serve as a potential access point for attackers to compromise a targeted system.

References

For more details about this vulnerability, its potential impact, and the fixes provided by Insyde, we recommend visiting the following links:
1. Insyde Security Pledge - This link offers an explanation of the vulnerability, its potential risks, and the measures taken by Insyde to mitigate the issue.
2. CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition - This link provides an in-depth look at the CWE-367 classification, which corresponds to the vulnerability detailed in this post.

Conclusion

CVE-2022-30774 represents a major vulnerability in the PnpSmm driver's parameter buffer due to the potential for TOCTOU attacks. This vulnerability posed serious risks, but Insyde promptly released the necessary fixes in subsequent kernel versions. As an end-user or system administrator, it is essential to ensure your systems are updated to the latest kernel version to protect against such vulnerabilities. Additionally, regularly reviewing security updates and keeping abreast of the latest vulnerability discoveries is crucial to maintaining a strong security posture.

Timeline

Published on: 11/15/2022 00:15:00 UTC
Last modified on: 02/14/2023 12:15:00 UTC