Index: sbin/ping/ping.c
===================================================================
--- sbin/ping/ping.c	(revision 351229)
+++ sbin/ping/ping.c	(working copy)
@@ -941,9 +941,13 @@
 				break;
 		}
 		if (n == 0 || options & F_FLOOD) {
+			u_char *outpackhdr_end = &outpackhdr[IP_MAXPACKET];
 			if (sweepmax && sntransmitted == snpackets) {
 				for (i = 0; i < sweepincr ; ++i)
-					*datap++ = i;
+					if (datap < outpackhdr_end)
+						*datap++ = i;
+					else
+						break;
 				datalen += sweepincr;
 				if (datalen > sweepmax)
 					break;