fix infinite loops when rebuild the cross reference table

core/fpdfapi/fpdf_parser/cpdf_parser.cpp

Index: core/fpdfapi/fpdf_parser/cpdf_parser.cpp
diff --git a/core/fpdfapi/fpdf_parser/cpdf_parser.cpp b/core/fpdfapi/fpdf_parser/cpdf_parser.cpp
index 4ba43678b80c3ca2198ad22257fa07b39ea9a040..a3e579ad6938e3c2597ae5ce060ebf3a7d10da33 100644
--- a/core/fpdfapi/fpdf_parser/cpdf_parser.cpp
+++ b/core/fpdfapi/fpdf_parser/cpdf_parser.cpp
@@ -931,9 +931,9 @@ FX_BOOL CPDF_Parser::RebuildCrossRef() {
     }
     pos += size;
 
-    // If the position has not changed at all in a loop iteration, then break
-    // out to prevent infinite looping.
-    if (pos == saved_pos)
+    // If the position has not changed at all or went backwards in a loop
+    // iteration, then break out to prevent infinite looping.
+    if (pos <= saved_pos)
       break;
   }