fix(detector): detect nonlocal value replay

kernelguard.py

@@ -2462,6 +2462,105 @@ def _has_ver(expr: ast.AST | None) -> bool:
     return []
 
 
+def detect_nonlocal_value_replay(code: str | SubmissionFacts) -> list[dict]:
+    """Pattern: factory-built entrypoint replays a nonlocal saved output."""
+    facts = ensure_submission_facts(code)
+    tree = facts.ast_tree
+    if tree is None:
+        return []
+    entrypoint_name = entrypoint_label(facts.entrypoint_name)
+
+    top_functions = {
+        stmt.name: stmt
+        for stmt in tree.body
+        if isinstance(stmt, ast.FunctionDef)
+    }
+    builders = {
+        stmt.value.func.id
+        for stmt in tree.body
+        if isinstance(stmt, ast.Assign)
+        and any(isinstance(target, ast.Name) and is_entrypoint_name(target.id) for target in stmt.targets)
+        and isinstance(stmt.value, ast.Call)
+        and isinstance(stmt.value.func, ast.Name)
+        and stmt.value.func.id in top_functions
+    }
+
+    def _param_names(node: ast.FunctionDef | ast.AsyncFunctionDef) -> set[str]:
+        params = {arg.arg for arg in node.args.args}
+        params.update(arg.arg for arg in node.args.posonlyargs)
+        params.update(arg.arg for arg in node.args.kwonlyargs)
+        return params
+
+    for builder_name in builders:
+        builder = top_functions[builder_name]
+        initialized = {
+            target.id
+            for stmt in builder.body
+            if isinstance(stmt, ast.Assign)
+            and isinstance(stmt.value, ast.Constant)
+            and stmt.value.value is None
+            for target in stmt.targets
+            if isinstance(target, ast.Name)
+        }
+        returned_inner = {
+            stmt.value.id
+            for stmt in builder.body
+            if isinstance(stmt, ast.Return)
+            and isinstance(stmt.value, ast.Name)
+        }
+
+        for inner in builder.body:
+            if not isinstance(inner, ast.FunctionDef) or inner.name not in returned_inner:
+                continue
+            params = _param_names(inner)
+            nonlocals = {
+                name
+                for stmt in inner.body
+                if isinstance(stmt, ast.Nonlocal)
+                for name in stmt.names
+            } & initialized
+            if not nonlocals:
+                continue
+
+            input_derived_assigns = {
+                target.id
+                for stmt in ast.walk(inner)
+                if isinstance(stmt, ast.Assign)
+                and bool(_expr_names(stmt.value) & params)
+                for target in stmt.targets
+                if isinstance(target, ast.Name) and target.id in nonlocals
+            }
+            if not input_derived_assigns:
+                continue
+
+            for child in ast.walk(inner):
+                if not isinstance(child, ast.If):
+                    continue
+                if _expr_names(child.test) & params:
+                    continue
+                if not (_expr_names(child.test) & input_derived_assigns):
+                    continue
+                if _body_has_calls(child.body):
+                    continue
+                returned = {
+                    stmt.value.id
+                    for stmt in child.body
+                    if isinstance(stmt, ast.Return)
+                    and isinstance(stmt.value, ast.Name)
+                }
+                if returned & input_derived_assigns:
+                    return [{
+                        "pattern": "NONLOCAL_VALUE_REPLAY",
+                        "severity": "critical",
+                        "evidence": (
+                            f"{entrypoint_name} returns a nonlocal output "
+                            "captured by its factory"
+                        ),
+                    }]
+
+    return []
+
+
 RE_OBJECT_ID_DATA = re.compile(r"\bdata_id\s*=\s*id\s*\(\s*data\s*\)")
 RE_RESULT_BANK_SET = re.compile(r"_superbatch_results\s*\[\s*(?:did|data_id)\s*\]\s*=")
 RE_RESULT_BANK_RETURN = re.compile(r"return\s+_superbatch_results\s*\[\s*data_id\s*\]")
@@ -3479,6 +3578,10 @@ class RulePolicy:
         "LAST_CALL_REPLAY", "result_reuse", "hard", AUTO_FILTER, (),
         AMD_MANUAL_LAST_CALL_REPLAY_FIXTURES, "keep",
     ),
+    "NONLOCAL_VALUE_REPLAY": RulePolicy(
+        "NONLOCAL_VALUE_REPLAY", "result_reuse", "hard", AUTO_FILTER, (),
+        (), "keep",
+    ),
     "SHAPE_OUTPUT_REPLAY": RulePolicy(
         "SHAPE_OUTPUT_REPLAY", "result_reuse", "hard", AUTO_FILTER, (),
         AMD_PACKAGE_SHAPE_REPLAY_FIXTURES, "keep",
@@ -3762,6 +3865,7 @@ def support_only_patterns(matched_patterns: list[dict]) -> bool:
     detect_decode_mm_ref,
     detect_result_caching,
     detect_last_call_replay,
+    detect_nonlocal_value_replay,
     detect_shape_output_replay,
     detect_timed_input_replay,
     detect_cuda_graph_replay,
@@ -3800,6 +3904,7 @@ def support_only_patterns(matched_patterns: list[dict]) -> bool:
     ("decode_mm_ref", detect_decode_mm_ref),
     ("result_caching", detect_result_caching),
     ("last_call_replay", detect_last_call_replay),
+    ("nonlocal_value_replay", detect_nonlocal_value_replay),
     ("shape_output_replay", detect_shape_output_replay),
     ("timed_input_replay", detect_timed_input_replay),
     ("cuda_graph_replay", detect_cuda_graph_replay),
@@ -4696,7 +4801,7 @@ def _worker_parquet(args: tuple) -> dict:
     "EVALUATOR_EXPLOIT", "HARNESS_RUNTIME_PATCHING", "MODULE_MUTATION", "GLOBALS_MUTATION", "CODE_REPLACEMENT",
     "FRAME_WALK_ACCESS", "FRAME_WALK_MUTATION", "SYS_MODULES_ACCESS", "GLOBALS_ACCESS", "CODE_ACCESS",
     "TRUSTED_MODULE_IMPORT",
-    "OUTPUT_REPLAY_CACHE", "LAST_CALL_REPLAY", "SHAPE_OUTPUT_REPLAY", "TIMED_INPUT_REPLAY", "CONFIG_CACHE_EXPLOIT", "POINTER_REPLAY", "RESULT_BANK_REPLAY", "PREPROCESS_CACHE", "WORKSPACE_CACHE",
+    "OUTPUT_REPLAY_CACHE", "LAST_CALL_REPLAY", "NONLOCAL_VALUE_REPLAY", "SHAPE_OUTPUT_REPLAY", "TIMED_INPUT_REPLAY", "CONFIG_CACHE_EXPLOIT", "POINTER_REPLAY", "RESULT_BANK_REPLAY", "PREPROCESS_CACHE", "WORKSPACE_CACHE",
     "RUNNER_PLAN_CACHE", "CUDA_GRAPH_PYTHON", "CUDA_GRAPH_REPLAY",
     "TIMER_MONKEYPATCH", "FAKE_BENCHMARK_EMIT", "STDIO_REDIRECT", "UNSYNC_MULTISTREAM", "CUDA_EVENT_DISABLE_TIMING",
     "SCALED_MM_REF", "DECODE_MM_REF", "SILENT_FALLBACK", "REFERENCE_PRECOMPUTE_REPLAY", "TORCH_COMPILE_CACHE",