Actions: migrate to the shared CFG library by owen-mc · Pull Request #22700 · github/codeql

owen-mc · 2026-09-29T15:43:43Z

Migrates the GitHub Actions control-flow graph to the shared CFG construction library already used by Java, C#, Ruby and Go.

Models workflows and composite actions as connected callable roots and removes duplicate scalar-expression parentage.
Preserves the existing Actions CFG, scope, traversal, and basic-block APIs where practical.
Attaches environment expressions to the workflow, job, or step that declares them, eliminating multiple parents, cycles, and same-type successor inconsistencies.
Adds the shared CFG consistency queries and focused regression coverage.

Meaningful CFG changes

Ignoring the synthetic before/after and entry/exit nodes introduced by the shared library, there are two intentional topology changes relative to the old CFG:

Environment expressions are evaluated at their declaration site.
- Previously, an environment expression was attached as a CFG child of every Run, UsesStep, or reusable-workflow job that could consume it. An inherited workflow- or job-level expression could therefore appear under many consumers, giving the same AST node multiple structural parents and successors.
- It is now attached exactly once to the workflow, job, or step whose env mapping declares it. Consumers no longer become structural CFG parents of inherited expressions.
- The expression remains reachable as a canonical CFG/data-flow node; only its placement and multiplicity change.
Expressions embedded in run scripts have a single structural path.
- Previously, a script expression could be both a direct child of its Run and a child of the script ScalarValue, creating duplicate paths to the same AST expression.
- ScalarValue is now a CFG leaf. Script expressions remain direct children of the Run, so no expression is lost; only the redundant parent/edge is removed.

Compatibility

The shared implementation introduces explicit before/after and entry/exit nodes, so code relying on exact raw CFG nodes, edges, textual representations, or basic-block boundaries may need updating.

The obsolete Completion, NormalCompletion, SimpleCompletion, BooleanCompletion, and ReturnCompletion classes are intentionally removed. Callers should inspect successor edge types such as DirectSuccessor, BooleanSuccessor, and ReturnSuccessor instead. Other established Actions CFG APIs are retained on top of the shared implementation.

Commit structure

The history is organized into three independently testable commits:

Migrate the core CFG and add consistency checks.
Restore public API compatibility and document the intentional breaking changes.
Correct environment-expression ownership and clear the consistency findings exposed by the migration.

Copilot

Copilot review overview

🔵 Needs a closer look

The foundational CFG and data-flow migration has broad compatibility implications that warrant final human validation.

Review effort: Balanced
Findings: None

What changed in this PR

Migrates GitHub Actions control-flow analysis to the shared CFG framework while retaining compatibility APIs.

Changes:

Rebuilds CFG scopes, nodes, basic blocks, and data-flow integration on shared infrastructure.
Corrects environment-expression ownership and adds consistency/regression checks.
Documents intentional API and raw-CFG compatibility changes.

File	Description
`actions/ql/lib/codeql/actions/controlflow/internal/Cfg.qll`	Implements the shared CFG integration.
`actions/ql/lib/codeql/actions/controlflow/BasicBlocks.qll`	Adapts existing basic-block APIs.
`actions/ql/lib/codeql/actions/Cfg.qll`	Re-exports the new implementation.
`actions/ql/lib/codeql/actions/dataflow/internal/DataFlowPrivate.qll`	Selects unique injected CFG nodes for data flow.
`actions/ql/lib/change-notes/2026-09-29-shared-cfg.md`	Documents breaking changes.
`actions/ql/consistency-queries/qlpack.yml`	Defines the Actions consistency pack.
`actions/ql/consistency-queries/CfgConsistency.ql`	Enables shared CFG checks.
`actions/ql/test/library-tests/cfg-environment/test.ql`	Tests environment CFG integrity.
`actions/ql/test/library-tests/cfg-environment/test.expected`	Records environment test results.
`actions/ql/test/library-tests/cfg-environment/.github/workflows/test.yml`	Supplies environment ownership cases.
`actions/ql/test/library-tests/basic/test.ql`	Extends CFG API regression coverage.
`actions/ql/test/library-tests/basic/test.expected`	Updates shared-CFG expectations.
`actions/ql/test/query-tests/Security/CWE-078/CONSISTENCY/CfgConsistency.expected`	Records empty consistency findings.
`actions/ql/test/query-tests/Security/CWE-088/CONSISTENCY/CfgConsistency.expected`	Records empty consistency findings.
`actions/ql/test/query-tests/Security/CWE-094/CONSISTENCY/CfgConsistency.expected`	Records empty consistency findings.
`actions/ql/test/query-tests/Security/CWE-829/CONSISTENCY/CfgConsistency.expected`	Records empty consistency findings.

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aschackmull · 2026-10-02T11:13:28Z

+    Callable getEnclosingCallable(AstNode node) {
+      result = node.(Callable)
+      or
+      result = getEnclosingCallable(node.getParentNode())


I don't know about actions, but in most languages this is wrong. If a callable is nested inside another callable then the innermost nodes get 2 enclosing callables.

I see what you mean. However, for actions, Callable is either a Workflow or a CompositeAction and these are both the root node of the file, so there isn't the kind of nesting you can have in other programming languages. I've added not node instanceof Callable and to make it clearer, as it makes no difference and is easier to understand for those not familiar with actions (which is most of us). I've also updated the QLDoc for getEnclosingCallable to document that it although getParentNode can have multiple results, all paths with give the same root callable.

Actually, it is technically possible to make a file that is both, though no one would do this in practice. I have updated the definition of Callable to always choose CompositeAction in that case. I've added a test for this.

Replace the legacy Actions CFG implementation with the shared CFG pipeline, keep data-flow nodes canonical, and ensure callable roots are connected without scalar-expression cycles. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Attach environment expressions once to their declaring workflow, job, or step so shared CFG nodes do not acquire multiple parents or form cycles. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Prefer the composite-action interpretation when a YAML document is recognized as both a workflow and a composite action, ensuring each CFG node has a unique enclosing callable. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

aschackmull · 2026-10-06T11:41:39Z

+query predicate cfgDeadEnds(Cfg::Node n) {
+  not n instanceof Cfg::ExitNode and
+  not exists(n.getASuccessor())
+}


Why is this here? Dead ends are detected as part of the consistency queries.

aschackmull · 2026-10-06T11:42:47Z

+  )
+}
+
+query predicate cfgConsistency(string query, int results) {


What's the point of this?

aschackmull · 2026-10-06T11:43:53Z

+query predicate legacyCfgSplits(Cfg::AstCfgNode node) {
+  exists(node.getSplitsString()) or
+  exists(node.getASplit())
+}


Anything referencing splits should be trivially empty and should be deleted.

aschackmull · 2026-10-06T11:44:35Z

+
+query predicate normalExitNodes(Cfg::AnnotatedExitNode exit) { exit.isNormal() }
+
+query predicate legacyNodeProperties(


Legacy node properties? What's the point here?

aschackmull · 2026-10-06T11:46:00Z

+
+query predicate cfgDeadEnds(Cfg::Node node) {
+  not node instanceof Cfg::ExitNode and
+  not exists(node.getASuccessor())
+}
+
+query predicate cfgConsistency(string query, int results) {
+  Cfg::Consistency::consistencyOverview(query, results) and
+  results != 0
+}


aschackmull · 2026-10-06T11:49:05Z

@@ -1,419 +1,85 @@
 /** Provides classes representing basic blocks. */


Can we delete this file? If not, please explain why not.

aschackmull · 2026-10-06T12:07:46Z

+  private AstNode getLastCfgAstNode(AstNode node) {
+    not exists(getCfgChild(node, _)) and result = node
+    or
+    exists(AstNode child, int index |
+      child = getCfgChild(node, index) and
+      not exists(int later | later > index and exists(getCfgChild(node, later))) and
+      result = getLastCfgAstNode(child)
+    )


I think this is dead code, right?

aschackmull · 2026-10-06T12:10:00Z

+  cached
+  AstNode getAControlFlowEntryNode(AstNode node) {
+    result = node and
+    exists(Node cfgNode | cfgNode.injects(node))
+  }


This is dead, right? Delete.

aschackmull · 2026-10-06T12:10:13Z

+  /** Gets a potential last AST node executed within `node`. */
+  cached
+  AstNode getAControlFlowExitNode(AstNode node) {
+    exists(Node cfgNode | cfgNode.injects(node)) and
+    result = getLastCfgAstNode(node)
+  }


This is dead, right? Delete.

aschackmull · 2026-10-06T12:12:11Z

+   * If needed, call this predicate to force a stage dependency on the cached CFG stage.
+   */
+  cached
+  predicate forceCachingInSameStage() { CfgCachedStage::ref() }


This does absolutely nothing when it isn't in a cached module. Also, the reference to CfgCachedStage::ref() here is plain bogus.

Delete.

aschackmull · 2026-10-06T12:15:56Z

+  cached
+  CfgScope getNodeCfgScope(Node node) { result = node.getScope() }


This is completely useless - it's caching a copy of the member predicate, which is then itself not cached. Do we have any indications that caching getEnclosingCallable is needed? If not, delete. If we do, perhaps just cache the input to the shared lib - that's way simpler (and actually works as opposed to this).

aschackmull · 2026-10-06T12:16:10Z

+    /** Gets a comma-separated list of splits in this node, if any. */
+    string getSplitsString() { none() }
+
+    /** Gets a split for this control flow node, if any. */
+    Split getASplit() { none() }


aschackmull · 2026-10-06T12:16:18Z


-private class ScalarValueLeaf extends LeafTree instanceof ScalarValue { }
+  /** The empty split type retained for compatibility with the legacy Actions CFG. */
+  class Split = Void;


aschackmull · 2026-10-06T12:17:28Z

+   *
+   * Only nodes that can be reached from an entry point are included in the CFG.
+   */
+  class Node extends ControlFlowNode {


Do we need this subclassing? It would be preferable if we cold just use the ControlFlowNode class that we got from the shared lib.

owen-mc requested a review from a team as a code owner September 29, 2026 15:43

Copilot AI balanced review requested due to automatic review settings September 29, 2026 15:43

Copilot started reviewing on behalf of owen-mc September 29, 2026 15:46 View session

github-actions Bot added documentation Actions Analysis of GitHub Actions labels Sep 29, 2026

Copilot AI reviewed Sep 29, 2026

View reviewed changes

owen-mc force-pushed the actions/migrate-shared-cfg branch from 2e616bb to c5f521d Compare September 29, 2026 16:20

github-advanced-security Bot found potential problems Sep 29, 2026

View reviewed changes

Comment thread actions/ql/lib/codeql/actions/controlflow/internal/Cfg.qll Fixed

aschackmull reviewed Oct 2, 2026

View reviewed changes

owen-mc force-pushed the actions/migrate-shared-cfg branch from c5f521d to a913e57 Compare October 5, 2026 10:28

owen-mc and others added 3 commits October 5, 2026 16:27

Actions: model environment expressions at declarations

95efef3

Attach environment expressions once to their declaring workflow, job, or step so shared CFG nodes do not acquire multiple parents or form cycles. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

owen-mc force-pushed the actions/migrate-shared-cfg branch from a913e57 to 755e78b Compare October 5, 2026 15:29

aschackmull reviewed Oct 6, 2026

View reviewed changes


		query predicate normalExitNodes(Cfg::AnnotatedExitNode exit) { exit.isNormal() }

		query predicate legacyNodeProperties(

		@@ -1,419 +1,85 @@
		/** Provides classes representing basic blocks. */

		cached
		CfgScope getNodeCfgScope(Node node) { result = node.getScope() }

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owen-mc commented Sep 29, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Meaningful CFG changes

Compatibility

Commit structure

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owen-mc commented Sep 29, 2026 •

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