tcp: force a dst refcount when prequeue packet

[ Upstream commit 093162553c33e9479283e107b4431378271c735d ]

Before escaping RCU protected section and adding packet into
prequeue, make sure the dst is refcounted.

Reported-by: Mike Galbraith <bitbucket@online.de>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 0768715..fe46019 100644 (file)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -931,6 +931,7 @@ static inline int tcp_prequeue(struct sock *sk, struct sk_buff *skb)
        if (sysctl_tcp_low_latency || !tp->ucopy.task)
                return 0;
 
        if (sysctl_tcp_low_latency || !tp->ucopy.task)
                return 0;
 

+       skb_dst_force(skb);

        __skb_queue_tail(&tp->ucopy.prequeue, skb);
        tp->ucopy.memory += skb->truesize;
        if (tp->ucopy.memory > sk->sk_rcvbuf) {
        __skb_queue_tail(&tp->ucopy.prequeue, skb);
        tp->ucopy.memory += skb->truesize;
        if (tp->ucopy.memory > sk->sk_rcvbuf) {