Inaccurate error_cnt Calculation Due to Flawed Test Style Resulting in UAF Vulnerability

[Oss-Auditor]

Hello, I have been using these libraries recently and noticed that the test file testdir/minc2-volprops-test.c exhibits a flawed error-handling style that leads to a Use-After-Free (UAF) vulnerability. Specifically, when memory initialization via minew_volume_props(&props) fails, the pointer props is not properly cleared (or set to NULL). Consequently, subsequent API calls continue to operate on an uninitialized or already freed memory region, resulting in a UAF condition. This issue directly impacts the accuracy of the error_cnt variable, as errors in the execution path are not correctly captured when the program proceeds after a fatal error.

Below is an annotated code snippet demonstrating the problem and providing suggestions for a safer error-handling approach:

// Initialize props; failure is detected but not properly handled
r = minew_volume_props(&props);
if (r < 0) {
    TESTRPT("minew_volume_props failed", r);
    // Missing: Set props to NULL or exit immediately to avoid later UAF.
}

// ... later in the code ...

mifree_volume_props(props);
// Note: props is not set to NULL after free, leading to potential dangling pointer use.

r = miget_volume_props(vol, &props);
if (r < 0) {
    TESTRPT("miget_volume_props failed", r);
    // Without proper checks, props may still refer to freed memory, causing UAF.
}

Root Cause Analysis:

• Flawed Error Handling:
  The root cause is the flawed testing style that does not immediately handle errors in memory initialization. When minew_volume_props fails, the pointer props remains non-NULL, which leads to subsequent API calls processing invalid memory. Additionally, even after freeing props with mifree_volume_props, the pointer is not cleared, resulting in a dangling pointer.

• Impact on error_cnt:
  Because the execution continues after these critical failures, the error counter (error_cnt) fails to capture the full extent of the problem. The error reporting mechanism becomes inaccurate as it does not reflect the cascade of subsequent errors stemming from the initial oversight.

• Consequences:
  This behavior not only creates a security risk by potentially allowing UAF vulnerabilities but also hampers effective debugging and error tracking. The root cause is not an inherent API flaw but rather the improper error handling in the test code, which should abort further processing on a fatal error.

Recommendation:

• Immediately set props to NULL or abort further processing upon encountering a critical error in memory initialization.
• Clear the pointer (props = NULL) after freeing memory to prevent accidental reuse.
• Enhance the error-handling logic so that once a fatal error is detected, no further API calls that rely on the pointer are executed.
• If necessary, I will submit a pull request.