Check CallSite arguments more rigorously

src/wasm/wasm-module.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/base/atomic-utils.h"
 #include "src/macro-assembler.h"
 #include "src/objects.h"
 #include "src/property-descriptor.h"
 #include "src/v8.h"
 
@@ skipping 960 matching lines @@
   }
   if (result->IsHeapNumber()) {
     return static_cast<int32_t>(HeapNumber::cast(*result)->value());
   }
   thrower.Error("WASM.compileRun() failed: Return value should be number");
   return -1;
 }
 
 MaybeHandle<String> GetWasmFunctionName(Handle<JSObject> wasm,
                                         uint32_t func_index) {
+  DCHECK(IsWasmObject(wasm));
   Object* func_names_arr_obj = wasm->GetInternalField(kWasmFunctionNamesArray);
   if (func_names_arr_obj->IsUndefined()) return Handle<String>::null();
   return GetWasmFunctionNameFromTable(
       handle(ByteArray::cast(func_names_arr_obj)), func_index);
 }
 
+bool IsWasmObject(Handle<JSObject> object) {
+  // TODO(clemensh): Check wasm byte header once we store a copy of the bytes.
+  return object->GetInternalFieldCount() == kWasmModuleInternalFieldCount &&
+         object->GetInternalField(kWasmModuleCodeTable)->IsFixedArray() &&
+         object->GetInternalField(kWasmMemArrayBuffer)->IsJSArrayBuffer() &&
+         (object->GetInternalField(kWasmFunctionNamesArray)->IsByteArray() ||
+          object->GetInternalField(kWasmFunctionNamesArray)->IsUndefined());
+}
+
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8