diff --git a/gas/ChangeLog b/gas/ChangeLog
index a930a842424..50eea849d00 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,8 @@
+2019-01-25  Wu Heng  <wu.heng@zte.com.cn>
+
+	PR gas/23940
+	* macro.c (getstring): Check array bound before accessing.
+
 2019-01-25  Alan Modra  <amodra@gmail.com>
 
 	PR 20902
diff --git a/gas/macro.c b/gas/macro.c
index 68ae04b010b..5f41c13cb80 100644
--- a/gas/macro.c
+++ b/gas/macro.c
@@ -285,8 +285,8 @@ getstring (size_t idx, sb *in, sb *acc)
 	{
 	  int nest = 0;
 	  idx++;
-	  while ((in->ptr[idx] != '>' || nest)
-		 && idx < in->len)
+	  while (idx < in->len
+		 && (in->ptr[idx] != '>' || nest))
 	    {
 	      if (in->ptr[idx] == '!')
 		{