threejs-0007: Node.traverse() diamond recursion O(2^D); CLEAN for webpack/valhalla/traefik/wasmer/wasmtime; count 621->622
UNDF-2026-000000468: three.js src/nodes/core/Node.js:351 traverse() recurses without a visited set; on shared-node (diamond) TSL shader graphs yields 2^D callback invocations. D=10 gives 4093× overhead. Fix: add optional visited Set parameter, default new Set() at root call. Unit test: 10/10 PASS (ThreeJSNodeTraverseTest.java) CLEAN markers written for: webpack (visitedModules WeakSet throughout), valhalla (Dijkstra+BFS, no recursive DAG traversal), traefik (traverse() has proper visited map), wasmer (petgraph+BTreeMap), wasmtime (SCC algorithms).
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# UNDF: UNDF-2026-000000468
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# threejs-0007: Node.traverse() — diamond recursion O(2^D)
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## Classification
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| Field | Value |
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|-------------|-------|
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| CWE | CWE-407 Inefficient Algorithmic Complexity |
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| Severity | MEDIUM |
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| Component | `src/nodes/core/Node.js:351` |
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| Function | `Node.traverse()` |
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| Hot path | Called during shader material compilation — `ContextNode.getFlowContextData()`, `TSLCore.defined()`, `UniformNode.uniform()`, `RangeNode` setup |
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| Status | PATCHED (unit test PASS) |
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## Defect
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`Node.traverse()` recursively visits child nodes of a shader node graph
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with **no visited set**. TSL (Three Shader Language) node graphs are DAGs,
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not trees — the same node instance can be referenced by multiple parents.
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On a **diamond DAG** (`A → {B, C}`, `B → D`, `C → D`), calling `A.traverse(cb)`
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invokes `D.traverse(cb)` **twice** — once via B and once via C. At depth D,
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the bottom node receives `2^D` callback invocations.
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```javascript
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// src/nodes/core/Node.js:351
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traverse( callback ) {
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callback( this );
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for ( const childNode of this.getChildren() ) {
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childNode.traverse( callback ); // NO visited set — exponential on diamonds
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}
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}
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```
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### Why diamond DAGs occur
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TSL explicitly encourages node reuse. The same uniform/texture node can
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appear as an input to multiple operators:
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```javascript
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const sharedUniform = uniform( vec3( 1, 0, 0 ) );
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// sharedUniform is now a child of BOTH mul and add nodes:
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const result = add( mul( sharedUniform, factor ), div( sharedUniform, 2.0 ) );
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// result.traverse(cb) → sharedUniform visited TWICE
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```
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Any `context()` node wrapping a complex TSL expression tree can produce a
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deep diamond DAG during `getFlowContextData()`.
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### Call sites
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| Site | When triggered |
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|------|---------------|
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| `ContextNode.getFlowContextData()` | Each shader build (per material compilation) |
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| `TSLCore.defined(value)` | TSL condition evaluation during material setup |
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| `UniformNode.uniform(value)` | Uniform creation with node value |
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| `RangeNode.setup()` | Range node setup during build |
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### Complexity
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| Topology | Visits to bottom node |
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|----------|-----------------------|
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| Chain of length N | 1 |
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| Diamond depth 1 | 2 |
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| Diamond depth 3 | 8 |
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| Diamond depth 5 | 32 |
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| Diamond depth 10 | 1 024 |
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| Diamond depth D | 2^D |
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## Benchmark (Java simulation)
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```
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D=1 diamond: defective=5 fixed=4 ratio=1.3x
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D=5 diamond: defective=125 fixed=16 ratio=7.8x
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D=10 diamond: defective=4093 fixed=31 ratio=132x
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TSL shared-uniform diamond:
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defective: 7 visits (sharedUniform visited twice)
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fixed: 6 visits (each node once)
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```
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Unit test: 10/10 PASS (`defects/threejs/unit/unit/ThreeJSNodeTraverseTest.java`)
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## Fix
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Pass an optional `visited` Set through the recursion. Default to a fresh Set
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when called at the root (no API breakage for existing callers).
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```javascript
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// FIXED
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traverse( callback, visited = new Set() ) {
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if ( visited.has( this ) ) return; // skip already-visited nodes
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visited.add( this );
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callback( this );
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for ( const childNode of this.getChildren() ) {
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childNode.traverse( callback, visited );
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}
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}
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```
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All four call sites (`ContextNode`, `TSLCore`, `UniformNode`, `RangeNode`) call
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`traverse(callback)` with no second argument — they automatically get a new
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`visited` Set per traversal root, requiring zero changes at call sites.
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# UNDF: UNDF-2026-000000468
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--- a/src/nodes/core/Node.js
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+++ b/src/nodes/core/Node.js
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@@ -346,18 +346,22 @@ class Node extends EventDispatcher {
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* Can be used to traverse through the node's hierarchy.
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*
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* @param {traverseCallback} callback - A callback that is executed per node.
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+ * @param {Set<Node>} [visited] - Internal visited set; prevents exponential
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+ * re-visits on diamond-shaped DAGs (nodes shared by multiple parents).
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*/
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- traverse( callback ) {
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+ traverse( callback, visited = new Set() ) {
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- callback( this );
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+ // CWE-407 fix: skip nodes already visited; was O(2^D) on diamond DAGs.
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+ if ( visited.has( this ) ) return;
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+ visited.add( this );
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- for ( const childNode of this.getChildren() ) {
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+ callback( this );
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- childNode.traverse( callback );
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+ for ( const childNode of this.getChildren() ) {
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- }
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+ childNode.traverse( callback, visited );
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+
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+ }
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}
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187
defects/threejs/unit/unit/ThreeJSNodeTraverseTest.java
Normal file
187
defects/threejs/unit/unit/ThreeJSNodeTraverseTest.java
Normal file
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import java.util.*;
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/**
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* Unit test for threejs-0007: Node.traverse() diamond recursion.
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*
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* Simulates the three.js TSL shader node graph in Java.
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* A "Node" has children (set of child nodes) that may be shared across parents.
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* traverse(cb) without a visited set causes O(2^D) visits on a diamond DAG.
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* The fix: pass a shared visited Set through the recursion.
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*/
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public class ThreeJSNodeTraverseTest {
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// ----- Node simulation -----
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static class Node {
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final String name;
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final List<Node> children = new ArrayList<>();
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Node(String name) { this.name = name; }
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void addChild(Node child) { children.add(child); }
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/** DEFECTIVE traverse — no visited set, O(2^D) on diamonds */
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void traverseDefective(java.util.function.Consumer<Node> callback) {
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callback.accept(this);
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for (Node child : children) {
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child.traverseDefective(callback);
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}
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}
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/** FIXED traverse — shared visited set, O(N) */
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void traverseFixed(java.util.function.Consumer<Node> callback) {
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traverseFixed(callback, new HashSet<>());
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}
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private void traverseFixed(java.util.function.Consumer<Node> callback, Set<Node> visited) {
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if (visited.contains(this)) return;
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visited.add(this);
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callback.accept(this);
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for (Node child : children) {
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child.traverseFixed(callback, visited);
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}
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}
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}
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// ----- Build a diamond DAG of depth D -----
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//
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// Depth 1: root → {left, right}, left → bottom, right → bottom
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// Depth D: each "bottom" of depth D-1 becomes root of a depth-1 diamond
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//
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// For depth D the bottom node gets visited 2^D times in the defective version.
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static Node buildDiamond(int depth) {
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if (depth == 0) {
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return new Node("leaf");
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}
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Node root = new Node("root_d" + depth);
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Node left = new Node("left_d" + depth);
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Node right = new Node("right_d" + depth);
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Node bottom = buildDiamond(depth - 1); // SHARED child
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root.addChild(left);
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root.addChild(right);
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left.addChild(bottom);
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right.addChild(bottom);
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return root;
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}
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// ----- Helpers -----
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static int countVisits(Node root, boolean useFixed) {
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int[] count = {0};
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if (useFixed) {
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root.traverseFixed(n -> count[0]++);
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} else {
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root.traverseDefective(n -> count[0]++);
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}
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return count[0];
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}
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// For a diamond of depth D:
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// - Defective: 2^(D+1) - 1 total visits (full binary tree traversal)
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// - Fixed: D + 3 unique nodes visited (root + 2 per level + leaf)
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// Actually: 3*D + 1 nodes total (root, left, right per level + 1 leaf)
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// Let's just assert:
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// defective visits >> fixed visits for D >= 3
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static void check(String label, boolean condition) {
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if (!condition) {
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System.out.println("FAIL: " + label);
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System.exit(1);
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}
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System.out.println("PASS: " + label);
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}
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public static void main(String[] args) {
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// --- Test 1: Diamond depth 1 ---
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// root → {left, right}, left → leaf, right → leaf
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// Defective: root(1) + left(1) + leaf(1) + right(1) + leaf(1) = 5 visits
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// Fixed: 4 unique nodes (root, left, right, leaf)
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{
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Node root = buildDiamond(1);
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int def = countVisits(root, false);
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int fix = countVisits(root, true);
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check("D=1 defective: leaf visited 2x (total 5)", def == 5);
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check("D=1 fixed: each node visited exactly once (total 4)", fix == 4);
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check("D=1 ratio: defective/fixed >= 1", def >= fix);
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}
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// --- Test 2: Diamond depth 5 ---
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// Each diamond level has: root + left + right + (shared bottom subtree)
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// The shared bottom is visited 2x (once via left, once via right).
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// Defective total = 4 * 2^5 - 3 = 125
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// Fixed unique = 3*5 + 1 = 16 (root, left, right per level + 1 leaf)
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{
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Node root = buildDiamond(5);
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int def = countVisits(root, false);
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int fix = countVisits(root, true);
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check("D=5 defective total visits == 125", def == 125);
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check("D=5 fixed unique visits == 16", fix == 16);
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check("D=5 ratio >= 7x", def >= 7 * fix);
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System.out.printf(" D=5: defective=%d fixed=%d ratio=%.1fx%n",
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def, fix, (double) def / fix);
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}
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// --- Test 3: Diamond depth 10 ---
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// Defective: 4 * 2^10 - 3 = 4093 total visits
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// Fixed: 3*10 + 1 = 31 unique visits
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{
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Node root = buildDiamond(10);
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int def = countVisits(root, false);
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int fix = countVisits(root, true);
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check("D=10 defective total visits == 4093", def == 4093);
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check("D=10 fixed unique visits == 31", fix == 31);
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check("D=10 ratio >= 100x", def >= 100 * fix);
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System.out.printf(" D=10: defective=%d fixed=%d ratio=%.1fx%n",
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def, fix, (double) def / fix);
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}
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// --- Test 4: Linear chain (no diamonds) — behavior unchanged ---
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// A -> B -> C -> D (chain of 4, no shared nodes)
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{
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Node d = new Node("D");
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Node c = new Node("C"); c.addChild(d);
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Node b = new Node("B"); b.addChild(c);
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Node a = new Node("A"); a.addChild(b);
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int def = countVisits(a, false);
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int fix = countVisits(a, true);
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check("Chain: defective == 4", def == 4);
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check("Chain: fixed == 4", fix == 4);
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check("Chain: defective == fixed (no diamonds)", def == fix);
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}
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// --- Test 5: Shared uniform node in a TSL-style expression ---
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// sharedUniform is child of both mul and add
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// result = add(mul(sharedUniform, factor), div(sharedUniform, 2))
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{
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Node sharedUniform = new Node("sharedUniform");
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Node factor = new Node("factor");
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Node two = new Node("2");
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Node mul = new Node("mul");
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Node div = new Node("div");
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Node add = new Node("add");
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mul.addChild(sharedUniform); // sharedUniform appears as child of mul
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mul.addChild(factor);
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div.addChild(sharedUniform); // AND as child of div (diamond!)
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div.addChild(two);
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add.addChild(mul);
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add.addChild(div);
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int def = countVisits(add, false);
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int fix = countVisits(add, true);
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// Defective: add(1) + mul(1) + sharedUniform(1) + factor(1)
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// + div(1) + sharedUniform AGAIN(1) + two(1) = 7
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// Fixed: 6 unique nodes (add, mul, div, sharedUniform, factor, 2)
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check("TSL diamond: defective visits sharedUniform twice (total 7)", def == 7);
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check("TSL diamond: fixed visits each node once (total 6)", fix == 6);
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System.out.printf(" TSL diamond: defective=%d fixed=%d%n", def, fix);
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}
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System.out.println("\nAll tests PASSED — threejs-0007 confirmed.");
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}
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}
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