Bug 1818576 - Double check whether the streams are locked before transfer r=evilpie

Status checks are done in batch before any transfer, but transferring streams can change the status of parent/child of TransformStream and cause an assertion failure.

Differential Revision: https://phabricator.services.mozilla.com/D170897

dom/streams/Transferable.cpp

@@ -809,7 +809,13 @@ MOZ_CAN_RUN_SCRIPT static void SetUpCrossRealmTransformReadable(
 bool ReadableStream::Transfer(JSContext* aCx, UniqueMessagePortId& aPortId) {
   // Step 1: If ! IsReadableStreamLocked(value) is true, throw a
   // "DataCloneError" DOMException.
-  // (Implemented in StructuredCloneHolder::CustomCanTransferHandler)
+  // (Implemented in StructuredCloneHolder::CustomCanTransferHandler, but double
+  // check here as the state might have changed in case this ReadableStream is
+  // created by a TransferStream and being transferred together with the
+  // parent.)
+  if (IsReadableStreamLocked(this)) {
+    return false;
+  }
 
   // Step 2: Let port1 be a new MessagePort in the current Realm.
   // Step 3: Let port2 be a new MessagePort in the current Realm.
@@ -895,7 +901,13 @@ bool ReadableStream::ReceiveTransfer(
 bool WritableStream::Transfer(JSContext* aCx, UniqueMessagePortId& aPortId) {
   // Step 1: If ! IsWritableStreamLocked(value) is true, throw a
   // "DataCloneError" DOMException.
-  // (Implemented in StructuredCloneHolder::CustomCanTransferHandler)
+  // (Implemented in StructuredCloneHolder::CustomCanTransferHandler, but double
+  // check here as the state might have changed in case this WritableStream is
+  // created by a TransferStream and being transferred together with the
+  // parent.)
+  if (IsWritableStreamLocked(this)) {
+    return false;
+  }
 
   // Step 2: Let port1 be a new MessagePort in the current Realm.
   // Step 3: Let port2 be a new MessagePort in the current Realm.
@@ -986,7 +998,13 @@ bool TransformStream::Transfer(JSContext* aCx, UniqueMessagePortId& aPortId1,
   // "DataCloneError" DOMException.
   // Step 4: If ! IsWritableStreamLocked(writable) is true, throw a
   // "DataCloneError" DOMException.
-  // (Implemented in StructuredCloneHolder::CustomCanTransferHandler)
+  // (Implemented in StructuredCloneHolder::CustomCanTransferHandler, but double
+  // check here as the state might have changed by
+  // Readable/WritableStream::Transfer in case the stream members of this
+  // TransformStream are being transferred together.)
+  if (IsReadableStreamLocked(mReadable) || IsWritableStreamLocked(mWritable)) {
+    return false;
+  }
 
   // Step 5: Set dataHolder.[[readable]] to !
   // StructuredSerializeWithTransfer(readable, « readable »).

testing/web-platform/tests/streams/transferable/transform-stream-members.any.js

@@ -0,0 +1,16 @@
+const combinations = [
+  (t => [t, t.readable])(new TransformStream()),
+  (t => [t.readable, t])(new TransformStream()),
+  (t => [t, t.writable])(new TransformStream()),
+  (t => [t.writable, t])(new TransformStream()),
+];
+
+for (const combination of combinations) {
+  test(() => {
+    assert_throws_dom(
+      "DataCloneError",
+      () => structuredClone(combination, { transfer: combination }),
+      "structuredClone should throw"
+    );
+  }, `Transferring ${combination} should fail`);
+}