LibWasm: Properly check active data segment offset in instantiation

Before, it was possible to crash the VM during instantiation when an
active data segment requested to put data in memory at an invalid
offset.

Userland/Libraries/LibWasm/AbstractMachine/AbstractMachine.cpp

@@ -346,20 +346,15 @@ InstantiationResult AbstractMachine::instantiate(Module const& module, Vector<Ex
  if (data.init.is_empty())
  return;
  auto address = main_module_instance.memories()[data.index.value()];
- if (auto instance = m_store.get(address)) {
- if (auto max = instance->type().limits().max(); max.has_value()) {
- if (*max * Constants::page_size < data.init.size() + offset) {
- instantiation_result = InstantiationError {
- ByteString::formatted("Data segment attempted to write to out-of-bounds memory ({}) of max {} bytes",
- data.init.size() + offset, instance->type().limits().max().value())
- };
- return;
- }
- }
- if (instance->size() < data.init.size() + offset)
- instance->grow(data.init.size() + offset - instance->size());
- instance->data().overwrite(offset, data.init.data(), data.init.size());
+ auto instance = m_store.get(address);
+ if (data.init.size() + offset > instance->size()) {
+ instantiation_result = InstantiationError {
+ ByteString::formatted("Data segment attempted to write to out-of-bounds memory ({}) in memory of size {}",
+ offset, instance->size())
+ };
+ return;
  }
+ instance->data().overwrite(offset, data.init.data(), data.init.size());
  },
  [&](DataSection::Data::Passive const& passive) {
  auto maybe_data_address = m_store.allocate_data(passive.init);