buffer: neuter external `nullptr` buffers

Neuter external `nullptr` buffers, otherwise their contents will be
materialized on access, and the buffer instance will be internalized.

This leads to a crash like this:

    v8::ArrayBuffer::Neuter Only externalized ArrayBuffers can be
    neutered

Fix: #3619
PR-URL: https://github.com/nodejs/node/pull/3624
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Trevor Norris <trev.norris@gmail.com>

3 files changed, 55 insertions, 0 deletions

diff --git a/test/addons/null-buffer-neuter/binding.cc b/test/addons/null-buffer-neuter/binding.cc
new file mode 100644
index 0000000000..da75919011
--- /dev/null
+++ b/test/addons/null-buffer-neuter/binding.cc
@@ -0,0 +1,40 @@
+#include <node.h>
+#include <node_buffer.h>
+#include <util.h>
+#include <v8.h>
+
+static int alive;
+
+static void FreeCallback(char* data, void* hint) {
+  CHECK_EQ(data, nullptr);
+  alive--;
+}
+
+void Run(const v8::FunctionCallbackInfo<v8::Value>& args) {
+  v8::Isolate* isolate = args.GetIsolate();
+  alive++;
+
+  {
+    v8::HandleScope scope(isolate);
+    v8::Local<v8::Object> buf = node::Buffer::New(
+          isolate,
+          nullptr,
+          0,
+          FreeCallback,
+          nullptr).ToLocalChecked();
+
+    char* data = node::Buffer::Data(buf);
+    CHECK_EQ(data, nullptr);
+  }
+
+  isolate->RequestGarbageCollectionForTesting(
+      v8::Isolate::kFullGarbageCollection);
+
+  CHECK_EQ(alive, 0);
+}
+
+void init(v8::Local<v8::Object> target) {
+  NODE_SET_METHOD(target, "run", Run);
+}
+
+NODE_MODULE(binding, init);
diff --git a/test/addons/null-buffer-neuter/binding.gyp b/test/addons/null-buffer-neuter/binding.gyp
new file mode 100644
index 0000000000..3bfb84493f
--- /dev/null
+++ b/test/addons/null-buffer-neuter/binding.gyp
@@ -0,0 +1,8 @@
+{
+  'targets': [
+    {
+      'target_name': 'binding',
+      'sources': [ 'binding.cc' ]
+    }
+  ]
+}
diff --git a/test/addons/null-buffer-neuter/test.js b/test/addons/null-buffer-neuter/test.js
new file mode 100644
index 0000000000..bca76e27af
--- /dev/null
+++ b/test/addons/null-buffer-neuter/test.js
@@ -0,0 +1,7 @@
+'use strict';
+// Flags: --expose-gc
+
+require('../../common');
+var binding = require('./build/Release/binding');
+
+binding.run();