script: Fix a borrow flags race in layout on .owner_doc().

src/components/main/layout/wrapper.rs

@@ -17,9 +17,21 @@
 //!
 //! When implementing wrapper functions, be careful that you do not touch the borrow flags, or you
 //! will race and cause spurious task failure. (Note that I do not believe these races are
-//! exploitable, but they'll result in brokenness nonetheless.) In general, you must not use the
+//! exploitable, but they'll result in brokenness nonetheless.)
-//! `Cast` functions; use explicit checks and `transmute_copy` instead. You must also not use
+//!
-//! `.get()`; instead, use `.unsafe_get()`.
+//! Rules of the road for this file:
+//!
+//! * In general, you must not use the `Cast` functions; use explicit checks and `transmute_copy`
+//!   instead.
+//!
+//! * You must also not use `.get()`; instead, use `.unsafe_get()`.
+//!
+//! * Do not call any methods on DOM nodes without checking to see whether they use borrow flags.
+//!   
+//!   o Instead of `get_attr()`, use `.get_attr_val_for_layout()`.
+//!
+//!   o Instead of `html_element_in_html_document()`, use
+//!     `html_element_in_html_document_for_layout()`.
 
 use extra::url::Url;
 use script::dom::bindings::codegen::InheritTypes::{ElementDerived, HTMLIFrameElementDerived};
@@ -222,10 +234,12 @@ impl<'ln> TNode<LayoutElement<'ln>> for LayoutNode<'ln> {
 
     fn match_attr(&self, attr: &AttrSelector, test: |&str| -> bool) -> bool {
         self.with_element(|element| {
-            let name = if element.element.html_element_in_html_document() {
+            let name = unsafe {
+                if element.element.html_element_in_html_document_for_layout() {
                     attr.lower_name.as_slice()
                 } else {
                     attr.name.as_slice()
+                }
             };
             match attr.namespace {
                 SpecificNamespace(ref ns) => {
@@ -338,7 +352,9 @@ impl<'le> TElement for LayoutElement<'le> {
     }
 
     fn get_hover_state(&self) -> bool {
-        self.element.node.get_hover_state()
+        unsafe {
+            self.element.node.get_hover_state_for_layout()
+        }
     }
 }
 

src/components/script/dom/element.rs

@@ -156,6 +156,17 @@ impl Element {
         self.node.owner_doc().get().is_html_document
     }
 
+    pub unsafe fn html_element_in_html_document_for_layout(&self) -> bool {
+        if self.namespace != namespace::HTML {
+            return false
+        }
+        let owner_doc: *JS<Document> = self.node.owner_doc();
+        let owner_doc: **Document = cast::transmute::<*JS<Document>,
+                                                      **Document>(
+                                                      owner_doc);
+        (**owner_doc).is_html_document
+    }
+
     pub fn get_attribute(&self,
                          namespace: Namespace,
                          name: &str) -> Option<JS<Attr>> {
@@ -249,7 +260,7 @@ impl Element {
                 if self_node.is_in_doc() {
                     // XXX: this dual declaration are workaround to avoid the compile error:
                     // "borrowed value does not live long enough"
-                    let mut doc = self.node.owner_doc();
+                    let mut doc = self.node.owner_doc().clone();
                     let doc = doc.get_mut();
                     doc.register_named_element(abstract_self, value.clone());
                 }
@@ -318,7 +329,7 @@ impl Element {
                 if self_node.is_in_doc() {
                     // XXX: this dual declaration are workaround to avoid the compile error:
                     // "borrowed value does not live long enough"
-                    let mut doc = self.node.owner_doc();
+                    let mut doc = self.node.owner_doc().clone();
                     let doc = doc.get_mut();
                     doc.unregister_named_element(old_value);
                 }

src/components/script/dom/htmlimageelement.rs

@@ -89,7 +89,7 @@ impl HTMLImageElement {
 
     pub fn AfterSetAttr(&mut self, name: DOMString, value: DOMString) {
         if "src" == name {
-            let document = self.htmlelement.element.node.owner_doc();
+            let document = self.htmlelement.element.node.owner_doc().clone();
             let window = document.get().window.get();
             let url = Some(window.get_url());
             self.update_image(Some(value), url);

src/components/script/dom/htmlobjectelement.rs

@@ -73,7 +73,7 @@ impl HTMLObjectElement {
 
     pub fn AfterSetAttr(&mut self, name: DOMString, _value: DOMString) {
         if "data" == name {
-            let document = self.htmlelement.element.node.owner_doc();
+            let document = self.htmlelement.element.node.owner_doc().clone();
             let window = document.get().window.clone();
             let url = Some(window.get().get_url());
             self.process_data_url(window.get().image_cache_task.clone(), url);

src/components/script/dom/node.rs

@@ -728,8 +728,8 @@ impl Node {
         }
     }
 
-    pub fn owner_doc(&self) -> JS<Document> {
+    pub fn owner_doc<'a>(&'a self) -> &'a JS<Document> {
-        self.owner_doc.clone().unwrap()
+        self.owner_doc.get_ref()
     }
 
     pub fn set_owner_doc(&mut self, document: &JS<Document>) {
@@ -852,7 +852,7 @@ impl Node {
             TextNodeTypeId |
             ProcessingInstructionNodeTypeId |
             DoctypeNodeTypeId |
-            DocumentFragmentNodeTypeId => Some(self.owner_doc()),
+            DocumentFragmentNodeTypeId => Some(self.owner_doc().clone()),
             DocumentNodeTypeId => None
         }
     }
@@ -878,7 +878,7 @@ impl Node {
     pub fn ChildNodes(&mut self, abstract_self: &JS<Node>) -> JS<NodeList> {
         match self.child_list {
             None => {
-                let doc = self.owner_doc();
+                let doc = self.owner_doc().clone();
                 let doc = doc.get();
                 let list = NodeList::new_child_list(&doc.window, abstract_self);
                 self.child_list = Some(list.clone());
@@ -976,7 +976,7 @@ impl Node {
                     None
                 } else {
                     let document = self.owner_doc();
-                    Some(NodeCast::from(&document.get().CreateTextNode(&document, value)))
+                    Some(NodeCast::from(&document.get().CreateTextNode(document, value)))
                 };
                 // Step 3.
                 Node::replace_all(node, abstract_self);
@@ -1558,31 +1558,31 @@ impl Node {
     //
 
     pub fn set_parent_node(&mut self, new_parent_node: Option<JS<Node>>) {
-        let doc = self.owner_doc();
+        let doc = self.owner_doc().clone();
         doc.get().wait_until_safe_to_modify_dom();
         self.parent_node = new_parent_node
     }
 
     pub fn set_first_child(&mut self, new_first_child: Option<JS<Node>>) {
-        let doc = self.owner_doc();
+        let doc = self.owner_doc().clone();
         doc.get().wait_until_safe_to_modify_dom();
         self.first_child = new_first_child
     }
 
     pub fn set_last_child(&mut self, new_last_child: Option<JS<Node>>) {
-        let doc = self.owner_doc();
+        let doc = self.owner_doc().clone();
         doc.get().wait_until_safe_to_modify_dom();
         self.last_child = new_last_child
     }
 
     pub fn set_prev_sibling(&mut self, new_prev_sibling: Option<JS<Node>>) {
-        let doc = self.owner_doc();
+        let doc = self.owner_doc().clone();
         doc.get().wait_until_safe_to_modify_dom();
         self.prev_sibling = new_prev_sibling
     }
 
     pub fn set_next_sibling(&mut self, new_next_sibling: Option<JS<Node>>) {
-        let doc = self.owner_doc();
+        let doc = self.owner_doc().clone();
         doc.get().wait_until_safe_to_modify_dom();
         self.next_sibling = new_next_sibling
     }
@@ -1619,6 +1619,11 @@ impl Node {
     pub fn next_sibling_ref<'a>(&'a self) -> Option<&'a JS<Node>> {
         self.next_sibling.as_ref()
     }
+
+    pub unsafe fn get_hover_state_for_layout(&self) -> bool {
+        let unsafe_this: *Node = cast::transmute::<&Node,*Node>(self);
+        (*unsafe_this).flags.get_in_hover_state()
+    }
 }
 
 impl Reflectable for Node {