Prevent loading saved models where constant nodes have no tensor value.

Also reorder fuzz generated test cases following f760f88b42

PiperOrigin-RevId: 308339007
Change-Id: I11d825203964cf3397846c57fd4a6f458e8536f3

tensorflow/cc/saved_model/loader.cc

@@ -70,6 +70,7 @@ uint64 GetLatencyMicroseconds(const uint64 start_microseconds) {
 }
 
 // Ensure that constant tensors loaded from the saved model have valid shape.
+// Also ensure that constant nodes have a value assigned to them.
 // TODO(b/154763635): this is temporary and will be replaced with a better audit
 static Status ValidateSavedTensors(const GraphDef& graph_def) {
   for (const auto& node : graph_def.node()) {
@@ -85,6 +86,10 @@ static Status ValidateSavedTensors(const GraphDef& graph_def) {
               node_shape.num_elements(), " elements");
         }
       }
+    } else if (node.op() == "Const") {
+      return errors::FailedPrecondition(
+          "Saved model contains node \"", node.name(),
+          "\" which is a constant tensor but no value has been provided");
     }
   }
   return Status::OK();

tensorflow/cc/saved_model/saved_model_bundle_test.cc

@@ -40,8 +40,10 @@ constexpr char kTestDataInitOpV2[] =
     "cc/saved_model/testdata/half_plus_two_v2/00000123";
 constexpr char kTestDataV2DebugInfo[] =
     "cc/saved_model/testdata/x_plus_y_v2_debuginfo";
-constexpr char kTestNegativeShapeFuzzGenerated[] =
-    "cc/saved_model/testdata/negative_shape/fuzz_generated";
+constexpr char kTestFuzzGeneratedNegativeShape[] =
+    "cc/saved_model/testdata/fuzz_generated/negative_shape";
+constexpr char kTestFuzzGeneratedConstWithNoValue[] =
+    "cc/saved_model/testdata/fuzz_generated/const_with_no_value";
 
 class LoaderTest : public ::testing::Test {
  protected:
@@ -264,7 +266,19 @@ TEST_F(LoaderTest, NegativeShapeDimension) {
   SessionOptions session_options;
 
   const string export_dir = io::JoinPath(testing::TensorFlowSrcRoot(),
-                                         kTestNegativeShapeFuzzGenerated);
+                                         kTestFuzzGeneratedNegativeShape);
+  Status st = LoadSavedModel(session_options, run_options, export_dir,
+                             {kSavedModelTagServe}, &bundle);
+  EXPECT_FALSE(st.ok());
+}
+
+TEST_F(LoaderTest, ConstNoValue) {
+  SavedModelBundle bundle;
+  RunOptions run_options;
+  SessionOptions session_options;
+
+  const string export_dir = io::JoinPath(testing::TensorFlowSrcRoot(),
+                                         kTestFuzzGeneratedConstWithNoValue);
   Status st = LoadSavedModel(session_options, run_options, export_dir,
                              {kSavedModelTagServe}, &bundle);
   EXPECT_FALSE(st.ok());