inet: add READ_ONCE(sk->sk_bound_dev_if) in inet_csk_bind_conflict()

inet_csk_bind_conflict() can access sk->sk_bound_dev_if for
unlocked sockets.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/inet_connection_sock.c

@@ -155,10 +155,14 @@ static int inet_csk_bind_conflict(const struct sock *sk,
 	 */
 
 	sk_for_each_bound(sk2, &tb->owners) {
-		if (sk != sk2 &&
-		    (!sk->sk_bound_dev_if ||
-		     !sk2->sk_bound_dev_if ||
-		     sk->sk_bound_dev_if == sk2->sk_bound_dev_if)) {
+		int bound_dev_if2;
+
+		if (sk == sk2)
+			continue;
+		bound_dev_if2 = READ_ONCE(sk2->sk_bound_dev_if);
+		if ((!sk->sk_bound_dev_if ||
+		     !bound_dev_if2 ||
+		     sk->sk_bound_dev_if == bound_dev_if2)) {
 			if (reuse && sk2->sk_reuse &&
 			    sk2->sk_state != TCP_LISTEN) {
 				if ((!relax ||