[NETLINK]: Fix infinite loops in synchronous netlink changes.

The qlen should continue to decrement, even if we
pop partially processed SKBs back onto the receive queue.
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/rtnetlink.c

@@ -626,14 +626,13 @@ static void rtnetlink_rcv(struct sock *sk, int len)
 		if (qlen > skb_queue_len(&sk->sk_receive_queue))
 			qlen = skb_queue_len(&sk->sk_receive_queue);
 
-		while (qlen--) {
+		for (; qlen; qlen--) {
 			skb = skb_dequeue(&sk->sk_receive_queue);
 			if (rtnetlink_rcv_skb(skb)) {
-				if (skb->len) {
+				if (skb->len)
 					skb_queue_head(&sk->sk_receive_queue,
 						       skb);
-					qlen++;
-				} else
+				else
 					kfree_skb(skb);
 				break;
 			}

net/decnet/netfilter/dn_rtmsg.c

@@ -121,7 +121,7 @@ static void dnrmg_receive_user_sk(struct sock *sk, int len)
 	struct sk_buff *skb;
 	unsigned int qlen = skb_queue_len(&sk->sk_receive_queue);
 
-	while (qlen-- && (skb = skb_dequeue(&sk->sk_receive_queue))) {
+	for (; qlen && (skb = skb_dequeue(&sk->sk_receive_queue)); qlen--) {
 		dnrmg_receive_user_skb(skb);
 		kfree_skb(skb);
 	}

net/xfrm/xfrm_user.c

@@ -1018,14 +1018,13 @@ static void xfrm_netlink_rcv(struct sock *sk, int len)
 		if (qlen > skb_queue_len(&sk->sk_receive_queue))
 			qlen = skb_queue_len(&sk->sk_receive_queue);
 
-		while (qlen--) {
+		for (; qlen; qlen--) {
 			skb = skb_dequeue(&sk->sk_receive_queue);
 			if (xfrm_user_rcv_skb(skb)) {
-				if (skb->len) {
+				if (skb->len)
 					skb_queue_head(&sk->sk_receive_queue,
 						       skb);
-					qlen++;
-				} else
+				else
 					kfree_skb(skb);
 				break;
 			}