Validate that strings in table are null terminated

Signed-off-by: Alan Jowett <alanjo@microsoft.com>

elfio/elfio_strings.hpp

@@ -46,7 +46,11 @@ template <class S> class string_section_accessor_template
             if ( index < string_section->get_size() ) {
                 const char* data = string_section->get_data();
                 if ( nullptr != data ) {
-                    return data + index;
+                    size_t string_length = strnlen(
+                        data + index, string_section->get_size() - index );
+                    if ( string_length <
+                         ( string_section->get_size() - index ) )
+                        return data + index;
                 }
             }
         }