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,