sctp: check the rto_min and rto_max in setsockopt

When we set 0 to rto_min or rto_max, just not change the value. Also
we should check the rto_min > rto_max.
Suggested-by: NVlad Yasevich <vyasevich@gmail.com>
Signed-off-by: NWang Weidong <wangweidong1@huawei.com>
Acked-by: NVlad Yasevich <vyasevich@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/sctp/socket.c

@@ -2815,6 +2815,8 @@ static int sctp_setsockopt_rtoinfo(struct sock *sk, char __user *optval, unsigne
 {
 	struct sctp_rtoinfo rtoinfo;
 	struct sctp_association *asoc;
+	unsigned long rto_min, rto_max;
+	struct sctp_sock *sp = sctp_sk(sk);
 
 	if (optlen != sizeof (struct sctp_rtoinfo))
 		return -EINVAL;
@@ -2828,26 +2830,36 @@ static int sctp_setsockopt_rtoinfo(struct sock *sk, char __user *optval, unsigne
 	if (!asoc && rtoinfo.srto_assoc_id && sctp_style(sk, UDP))
 		return -EINVAL;
 
+	rto_max = rtoinfo.srto_max;
+	rto_min = rtoinfo.srto_min;
+
+	if (rto_max)
+		rto_max = asoc ? msecs_to_jiffies(rto_max) : rto_max;
+	else
+		rto_max = asoc ? asoc->rto_max : sp->rtoinfo.srto_max;
+
+	if (rto_min)
+		rto_min = asoc ? msecs_to_jiffies(rto_min) : rto_min;
+	else
+		rto_min = asoc ? asoc->rto_min : sp->rtoinfo.srto_min;
+
+	if (rto_min > rto_max)
+		return -EINVAL;
+
 	if (asoc) {
 		if (rtoinfo.srto_initial != 0)
 			asoc->rto_initial =
 				msecs_to_jiffies(rtoinfo.srto_initial);
-		if (rtoinfo.srto_max != 0)
-			asoc->rto_max = msecs_to_jiffies(rtoinfo.srto_max);
-		if (rtoinfo.srto_min != 0)
-			asoc->rto_min = msecs_to_jiffies(rtoinfo.srto_min);
+		asoc->rto_max = rto_max;
+		asoc->rto_min = rto_min;
 	} else {
 		/* If there is no association or the association-id = 0
 		 * set the values to the endpoint.
 		 */
-		struct sctp_sock *sp = sctp_sk(sk);
-
 		if (rtoinfo.srto_initial != 0)
 			sp->rtoinfo.srto_initial = rtoinfo.srto_initial;
-		if (rtoinfo.srto_max != 0)
-			sp->rtoinfo.srto_max = rtoinfo.srto_max;
-		if (rtoinfo.srto_min != 0)
-			sp->rtoinfo.srto_min = rtoinfo.srto_min;
+		sp->rtoinfo.srto_max = rto_max;
+		sp->rtoinfo.srto_min = rto_min;
 	}
 
 	return 0;