sctp: read sk->sk_bound_dev_if once in sctp_rcv()

sctp_rcv() reads sk->sk_bound_dev_if twice while the socket
is not locked. Another cpu could change this field under us.

Fixes: 0fd9a65a76e8 ("[SCTP] Support SO_BINDTODEVICE socket option on incoming packets.")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: Vlad Yasevich <vyasevich@gmail.com>
Cc: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sctp/input.c b/net/sctp/input.c
index 90e12ba..4f43afa 100644 (file)
--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -92,6 +92,7 @@ int sctp_rcv(struct sk_buff *skb)
        struct sctp_chunk *chunk;
        union sctp_addr src;
        union sctp_addr dest;
+       int bound_dev_if;
        int family;
        struct sctp_af *af;
        struct net *net = dev_net(skb->dev);
@@ -169,7 +170,8 @@ int sctp_rcv(struct sk_buff *skb)
         * If a frame arrives on an interface and the receiving socket is
         * bound to another interface, via SO_BINDTODEVICE, treat it as OOTB
         */
-       if (sk->sk_bound_dev_if && (sk->sk_bound_dev_if != af->skb_iif(skb))) {
+       bound_dev_if = READ_ONCE(sk->sk_bound_dev_if);
+       if (bound_dev_if && (bound_dev_if != af->skb_iif(skb))) {
                if (transport) {
                        sctp_transport_put(transport);
                        asoc = NULL;