1 files changed, 28 insertions, 19 deletions

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 44f6a20fa29d..62c19fdd102d 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -560,15 +560,11 @@ static inline struct sock *__udp4_lib_lookup_skb(struct sk_buff *skb,
 						 __be16 sport, __be16 dport,
 						 struct udp_table *udptable)
 {
-	struct sock *sk;
 	const struct iphdr *iph = ip_hdr(skb);
 
-	if (unlikely(sk = skb_steal_sock(skb)))
-		return sk;
-	else
-		return __udp4_lib_lookup(dev_net(skb_dst(skb)->dev), iph->saddr, sport,
-					 iph->daddr, dport, inet_iif(skb),
-					 udptable);
+	return __udp4_lib_lookup(dev_net(skb_dst(skb)->dev), iph->saddr, sport,
+				 iph->daddr, dport, inet_iif(skb),
+				 udptable);
 }
 
 struct sock *udp4_lib_lookup(struct net *net, __be32 saddr, __be16 sport,
@@ -1603,12 +1599,21 @@ static void flush_stack(struct sock **stack, unsigned int count,
 		kfree_skb(skb1);
 }
 
-static void udp_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb)
+/* For TCP sockets, sk_rx_dst is protected by socket lock
+ * For UDP, we use sk_dst_lock to guard against concurrent changes.
+ */
+static void udp_sk_rx_dst_set(struct sock *sk, struct dst_entry *dst)
 {
-	struct dst_entry *dst = skb_dst(skb);
+	struct dst_entry *old;
 
-	dst_hold(dst);
-	sk->sk_rx_dst = dst;
+	spin_lock(&sk->sk_dst_lock);
+	old = sk->sk_rx_dst;
+	if (likely(old != dst)) {
+		dst_hold(dst);
+		sk->sk_rx_dst = dst;
+		dst_release(old);
+	}
+	spin_unlock(&sk->sk_dst_lock);
 }
 
 /*
@@ -1739,15 +1744,16 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
 	if (udp4_csum_init(skb, uh, proto))
 		goto csum_error;
 
-	if (skb->sk) {
+	sk = skb_steal_sock(skb);
+	if (sk) {
+		struct dst_entry *dst = skb_dst(skb);
 		int ret;
-		sk = skb->sk;
 
-		if (unlikely(sk->sk_rx_dst == NULL))
-			udp_sk_rx_dst_set(sk, skb);
+		if (unlikely(sk->sk_rx_dst != dst))
+			udp_sk_rx_dst_set(sk, dst);
 
 		ret = udp_queue_rcv_skb(sk, skb);
-
+		sock_put(sk);
 		/* a return value > 0 means to resubmit the input, but
 		 * it wants the return to be -protocol, or 0
 		 */
@@ -1913,17 +1919,20 @@ static struct sock *__udp4_lib_demux_lookup(struct net *net,
 
 void udp_v4_early_demux(struct sk_buff *skb)
 {
-	const struct iphdr *iph = ip_hdr(skb);
-	const struct udphdr *uh = udp_hdr(skb);
+	struct net *net = dev_net(skb->dev);
+	const struct iphdr *iph;
+	const struct udphdr *uh;
 	struct sock *sk;
 	struct dst_entry *dst;
-	struct net *net = dev_net(skb->dev);
 	int dif = skb->dev->ifindex;
 
 	/* validate the packet */
 	if (!pskb_may_pull(skb, skb_transport_offset(skb) + sizeof(struct udphdr)))
 		return;
 
+	iph = ip_hdr(skb);
+	uh = udp_hdr(skb);
+
 	if (skb->pkt_type == PACKET_BROADCAST ||
 	    skb->pkt_type == PACKET_MULTICAST)
 		sk = __udp4_lib_mcast_demux_lookup(net, uh->dest, iph->daddr,