[wasm] Fix memory bug

src/api.cc

 // Copyright 2012 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/api.h"
 
 #include <string.h>  // For memcpy, strlen.
 #ifdef V8_USE_ADDRESS_SANITIZER
 #include <sanitizer/asan_interface.h>
 #endif  // V8_USE_ADDRESS_SANITIZER
@@ skipping 7228 matching lines @@
   if (!ret.IsEmpty()) return ret;
   return Compile(isolate, uncompiled_bytes);
 }
 
 MaybeLocal<WasmCompiledModule> WasmCompiledModule::Compile(
     Isolate* isolate, Local<String> bytes) {
   i::Handle<i::String> module_bytes = Utils::OpenHandle(*bytes);
   i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
   i::wasm::ErrorThrower thrower(i_isolate, "WasmCompiledModule::Deserialize()");
   i::SeqOneByteString* data = i::SeqOneByteString::cast(*module_bytes);
+  i::ScopedVector<unsigned char> bytes_copy(data->length());

[titzer, 2016/10/07 09:29:58]

Can you leave a TODO here, since we eventually make another copy of the bytes,
AFAICT.

[Clemens Hammacher, 2016/10/07 09:43:27]

Done.

+  memcpy(bytes_copy.start(), data->GetChars(), data->length());
   i::MaybeHandle<i::JSObject> maybe_compiled =
       i::wasm::CreateModuleObjectFromBytes(
-          i_isolate, data->GetChars(), data->GetChars() + data->length(),
-          &thrower, i::wasm::ModuleOrigin::kWasmOrigin);
+          i_isolate, bytes_copy.start(),
+          bytes_copy.start() + bytes_copy.length(), &thrower,
+          i::wasm::ModuleOrigin::kWasmOrigin);
   if (maybe_compiled.is_null()) return MaybeLocal<WasmCompiledModule>();
   return Local<WasmCompiledModule>::Cast(
       Utils::ToLocal(maybe_compiled.ToHandleChecked()));
 }
 
 // static
 v8::ArrayBuffer::Allocator* v8::ArrayBuffer::Allocator::NewDefaultAllocator() {
   return new ArrayBufferAllocator();
 }
 
@@ skipping 2154 matching lines @@
   Address callback_address =
       reinterpret_cast<Address>(reinterpret_cast<intptr_t>(callback));
   VMState<EXTERNAL> state(isolate);
   ExternalCallbackScope call_scope(isolate, callback_address);
   callback(info);
 }
 
 
 }  // namespace internal
 }  // namespace v8