From 9bf2742736a066910d866ba7a92d9e6cfc84a90b Mon Sep 17 00:00:00 2001
From: Jonathan Kew <jkew@mozilla.com>
Date: Thu, 29 Oct 2020 12:27:49 +0000
Subject: [PATCH] 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 | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/intl/hyphenation/glue/nsHyphenator.cpp b/intl/hyphenation/glue/nsHyphenator.cpp
index 363fe6b29566..6efb59ba76ea 100644
--- a/intl/hyphenation/glue/nsHyphenator.cpp
+++ b/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;
   }