Bug 1672388 - Validate hyphenation data before freezing the shared memory, which will unmap it. r=emilio

Differential Revision: https://phabricator.services.mozilla.com/D94320

intl/hyphenation/glue/nsHyphenator.cpp

@@ -161,15 +161,16 @@ static UniquePtr<base::SharedMemory> LoadFromURI(nsIURI* aURI,
         bytesRead != available) {
       return nullptr;
     }
-    if (!shm->Freeze()) {
-      return nullptr;
-    }
 
     if (!mapped_hyph_is_valid_hyphenator(
             reinterpret_cast<const uint8_t*>(buffer), bytesRead)) {
       return nullptr;
     }
 
+    if (!shm->Freeze()) {
+      return nullptr;
+    }
+
     *aLength = bytesRead;
     return shm;
   }