Bug 1349276 - Paths received by FileSystemRequestParent need to be sanitized before passed to IsDescendantPath, r=haik

dom/filesystem/FileSystemSecurity.cpp

@@ -89,6 +89,10 @@ FileSystemSecurity::ContentProcessHasAccessTo(ContentParentId aId,
   MOZ_ASSERT(NS_IsMainThread());
   AssertIsInMainProcess();
 
+  if (FindInReadable(NS_LITERAL_STRING(".."), aPath)) {
+    return false;
+  }
+
   nsTArray<nsString>* paths;
   if (!mPaths.Get(aId, &paths)) {
     return false;