[script] Avoid trying to read final character of a zero-length string

Detected using Valgrind.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

diff --git a/src/image/script.c b/src/image/script.c
index 8ef058545e8b49ccf74266ed289afe2e2db94d73..ceccd90183b7532dfaa1f779c8a742199a022780 100644 (file)
--- a/src/image/script.c
+++ b/src/image/script.c
@@ -92,11 +92,11 @@ static int process_script ( struct image *image,
                script_offset += ( frag_len + 1 );
 
                /* Strip trailing CR, if present */
-               if ( line[ len - 1 ] == '\r' )
+               if ( len && ( line[ len - 1 ] == '\r' ) )
                        len--;
 
                /* Handle backslash continuations */
-               if ( line[ len - 1 ] == '\\' ) {
+               if ( len && ( line[ len - 1 ] == '\\' ) ) {
                        len--;
                        rc = -EINVAL;
                        continue;