Segv when PDF-side JS object property getter invoked from XFA.

The PDF-side native objects require that the current v8 context
has been set-up to point at the state (via CJS_Runtime) for the
getters, setters, and methods to operate against. XFA doesn't
supply a context with that state, so at the first opportunity for
a PDF-side object to be leaked to XFA, set up the context to mimic
the PDF side.

Changed FXJS_GetRuntimeFromIsolate() to FXJS_GetRuntimeFromV8Context()
for consistency with the newly added method.

BUG=pdfium:266
R=jochen@chromium.org

Review URL: https://codereview.chromium.org/1412103010 .

1 files changed, 10 insertions, 2 deletions

diff --git a/fpdfsdk/src/javascript/JS_Runtime.cpp b/fpdfsdk/src/javascript/JS_Runtime.cpp
index 8b0475b851..ecb53d2d72 100644
--- a/fpdfsdk/src/javascript/JS_Runtime.cpp
+++ b/fpdfsdk/src/javascript/JS_Runtime.cpp
@@ -245,12 +245,20 @@ FX_BOOL CJS_Runtime::GetHValueByName(const CFX_ByteStringC& utf8Name,
   v8::Locker lock(GetIsolate());
   v8::Isolate::Scope isolate_scope(GetIsolate());
   v8::HandleScope handle_scope(GetIsolate());
+  v8::Local<v8::Context> old_context = GetIsolate()->GetCurrentContext();
   v8::Local<v8::Context> context =
       v8::Local<v8::Context>::New(GetIsolate(), m_context);
   v8::Context::Scope context_scope(context);
 
-  // v8::Local<v8::Context> tmpCotext =
-  // v8::Local<v8::Context>::New(GetIsolate(), m_context);
+  // Caution: We're about to hand to XFA an object that in order to invoke
+  // methods will require that the current v8::Context always has a pointer
+  // to a CJS_Runtime in its embedder data slot. Unfortunately, XFA creates
+  // its own v8::Context which has not initialized the embedder data slot.
+  // Do so now.
+  // TODO(tsepez): redesign PDF-side objects to not rely on v8::Context's
+  // embedder data slots, and/or to always use the right context.
+  FXJS_SetRuntimeForV8Context(old_context, this);
+
   v8::Local<v8::Value> propvalue =
       context->Global()->Get(v8::String::NewFromUtf8(
           GetIsolate(), name, v8::String::kNormalString, utf8Name.GetLength()));