worker: use engine-provided deleter for `SharedArrayBuffer`s

Store the full information we have on a given `SharedArrayBuffer`,
and use the deleter provided by the JS engine to free the memory
when that is needed.

This fixes memory lifetime management for WASM buffers that are
passed through a `MessageChannel` (e.g. between threads).

PR-URL: https://github.com/nodejs/node/pull/25307
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>

2 files changed, 12 insertions, 9 deletions

diff --git a/src/sharedarraybuffer_metadata.cc b/src/sharedarraybuffer_metadata.cc
index 3e760bc50b..671ad6d682 100644
--- a/src/sharedarraybuffer_metadata.cc
+++ b/src/sharedarraybuffer_metadata.cc
@@ -89,8 +89,7 @@ SharedArrayBufferMetadata::ForSharedArrayBuffer(
   }
 
   SharedArrayBuffer::Contents contents = source->Externalize();
-  SharedArrayBufferMetadataReference r(new SharedArrayBufferMetadata(
-      contents.Data(), contents.ByteLength()));
+  SharedArrayBufferMetadataReference r(new SharedArrayBufferMetadata(contents));
   if (r->AssignToSharedArrayBuffer(env, context, source).IsNothing())
     return nullptr;
   return r;
@@ -111,17 +110,22 @@ Maybe<bool> SharedArrayBufferMetadata::AssignToSharedArrayBuffer(
                             obj);
 }
 
-SharedArrayBufferMetadata::SharedArrayBufferMetadata(void* data, size_t size)
-  : data(data), size(size) { }
+SharedArrayBufferMetadata::SharedArrayBufferMetadata(
+    const SharedArrayBuffer::Contents& contents)
+  : contents_(contents) { }
 
 SharedArrayBufferMetadata::~SharedArrayBufferMetadata() {
-  free(data);
+  contents_.Deleter()(contents_.Data(),
+                      contents_.ByteLength(),
+                      contents_.DeleterData());
 }
 
 MaybeLocal<SharedArrayBuffer> SharedArrayBufferMetadata::GetSharedArrayBuffer(
     Environment* env, Local<Context> context) {
   Local<SharedArrayBuffer> obj =
-      SharedArrayBuffer::New(env->isolate(), data, size);
+      SharedArrayBuffer::New(env->isolate(),
+                             contents_.Data(),
+                             contents_.ByteLength());
 
   if (AssignToSharedArrayBuffer(env, context, obj).IsNothing())
     return MaybeLocal<SharedArrayBuffer>();
diff --git a/src/sharedarraybuffer_metadata.h b/src/sharedarraybuffer_metadata.h
index 84bfd224fa..8c753a89c1 100644
--- a/src/sharedarraybuffer_metadata.h
+++ b/src/sharedarraybuffer_metadata.h
@@ -46,7 +46,7 @@ class SharedArrayBufferMetadata
   SharedArrayBufferMetadata(const SharedArrayBufferMetadata&) = delete;
 
  private:
-  explicit SharedArrayBufferMetadata(void* data, size_t size);
+  explicit SharedArrayBufferMetadata(const v8::SharedArrayBuffer::Contents&);
 
   // Attach a lifetime tracker object with a reference count to `target`.
   v8::Maybe<bool> AssignToSharedArrayBuffer(
@@ -54,8 +54,7 @@ class SharedArrayBufferMetadata
       v8::Local<v8::Context> context,
       v8::Local<v8::SharedArrayBuffer> target);
 
-  void* data = nullptr;
-  size_t size = 0;
+  v8::SharedArrayBuffer::Contents contents_;
 };
 
 }  // namespace worker