C++: Fix queries after #20126

[MathiasVP]

Description

github/codeql#20126 fixes a long standing missing flow issue for global variables (see that PR's description for details). It looks like the c/cert/clean-up-thread-specific-storage query was not written with this global variable flow in mind, and the improvements to global variable flow is causing false negatives on stuff like:

static tss_t k;

void m1() {
  tss_create(&k, NULL); // non compliant
}

void m2() {
  thrd_t id;
  tss_create(&k, free);
  ...
  tss_delete(k);
}

Before github/codeql#20126 we'd not flow from tss_create's outgoing argument (&k) to the global variable declaration, and then to &k in m2 (read the description in github/codeql#20126 to see why!). However, after github/codeql#20126 we now get this flow. This results in a false negative.

To fix this, I've blocked flow into the sources. This means that, once again, the flow starting at m1 doesn't go to any sink.

I'll keep this in draft until github/codeql#20126 is ready to go in (which will likely be waiting until Jeroen is back).

Change request type

• Release or process automation (GitHub workflows, internal scripts)
• Internal documentation
• External documentation
• Query files (.ql, .qll, .qls or unit tests)
• External scripts (analysis report or other code shipped as part of a release)

Rules with added or modified queries

• No rules added
• Queries have been added for the following rules:
  • rule number here
• Queries have been modified for the following rules:
  • rule number here

Release change checklist

A change note (development_handbook.md#change-notes) is required for any pull request which modifies:

• The structure or layout of the release artifacts.
• The evaluation performance (memory, execution time) of an existing query.
• The results of an existing query in any circumstance.

If you are only adding new rule queries, a change note is not required.

Author: Is a change note required?

• Yes
• No

🚨🚨🚨
Reviewer: Confirm that format of shared queries (not the .qll file, the
.ql file that imports it) is valid by running them within VS Code.

• Confirmed

Reviewer: Confirm that either a change note is not required or the change note is required and has been added.

• Confirmed

Query development review checklist

For PRs that add new queries or modify existing queries, the following checklist should be completed by both the author and reviewer:

Author

• Have all the relevant rule package description files been checked in?
• Have you verified that the metadata properties of each new query is set appropriately?
• Do all the unit tests contain both "COMPLIANT" and "NON_COMPLIANT" cases?
• Are the alert messages properly formatted and consistent with the style guide?
• Have you run the queries on OpenPilot and verified that the performance and results are acceptable?
  As a rule of thumb, predicates specific to the query should take no more than 1 minute, and for simple queries be under 10 seconds. If this is not the case, this should be highlighted and agreed in the code review process.
• Does the query have an appropriate level of in-query comments/documentation?
• Have you considered/identified possible edge cases?
• Does the query not reinvent features in the standard library?
• Can the query be simplified further (not golfed!)

Reviewer

• Have all the relevant rule package description files been checked in?
• Have you verified that the metadata properties of each new query is set appropriately?
• Do all the unit tests contain both "COMPLIANT" and "NON_COMPLIANT" cases?
• Are the alert messages properly formatted and consistent with the style guide?
• Have you run the queries on OpenPilot and verified that the performance and results are acceptable?
  As a rule of thumb, predicates specific to the query should take no more than 1 minute, and for simple queries be under 10 seconds. If this is not the case, this should be highlighted and agreed in the code review process.
• Does the query have an appropriate level of in-query comments/documentation?
• Have you considered/identified possible edge cases?
• Does the query not reinvent features in the standard library?
• Can the query be simplified further (not golfed!)

[Copilot]

Pull Request Overview

This PR fixes a false positive issue in the c/cert/clean-up-thread-specific-storage query that was introduced by improved global variable flow tracking in PR #20126. The fix prevents data flow from entering the sources to maintain correct query behavior.

• Adds a new Direction type and updates the isSource predicate to handle both outgoing and incoming flow directions
• Implements a isBarrierIn predicate to block incoming flow into sources
• Maintains the original query logic while accommodating the improved global variable flow

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
c/cert/src/rules/CON30-C/CleanUpThreadSpecificStorage.ql	Adds flow direction handling and barrier logic to fix false positives
c/misra/test/rules/RULE-21-26/TimedlockOnInappropriateMutexType.expected	Updates test expectations to reflect improved global variable flow tracking