Index: dist/Xi/chgfctl.c
===================================================================
RCS file: /cvsroot/xsrc/external/mit/xorg-server.old/dist/Xi/chgfctl.c,v
retrieving revision 1.1.1.1
diff -p -u -r1.1.1.1 chgfctl.c
--- dist/Xi/chgfctl.c	9 Jun 2016 09:07:56 -0000	1.1.1.1
+++ dist/Xi/chgfctl.c	27 Apr 2021 18:44:31 -0000
@@ -468,8 +468,11 @@ ProcXChangeFeedbackControl(ClientPtr cli
     case StringFeedbackClass:
     {
 	char n;
-	xStringFeedbackCtl *f = ((xStringFeedbackCtl *) & stuff[1]);
+        xStringFeedbackCtl *f;
 
+        REQUEST_AT_LEAST_EXTRA_SIZE(xChangeFeedbackControlReq,
+                                    sizeof(xStringFeedbackCtl));
+        f = ((xStringFeedbackCtl *) &stuff[1]);
 	if (client->swapped) {
             if (len < bytes_to_int32(sizeof(xStringFeedbackCtl)))
                 return BadLength;