net: diag: Fix refcnt leak in error path destroying socket

inet_diag_find_one_icsk takes a reference to a socket that is not
released if sock_diag_destroy returns an error. Fix by changing
tcp_diag_destroy to manage the refcnt for all cases and remove
the sock_put calls from tcp_abort.

Fixes: c1e64e298b8ca ("net: diag: Support destroying TCP sockets")
Reported-by: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/tcp.c

@@ -3193,7 +3193,6 @@ int tcp_abort(struct sock *sk, int err)
 			local_bh_enable();
 			return 0;
 		}
-		sock_gen_put(sk);
 		return -EOPNOTSUPP;
 	}
 
@@ -3222,7 +3221,6 @@ int tcp_abort(struct sock *sk, int err)
 	bh_unlock_sock(sk);
 	local_bh_enable();
 	release_sock(sk);
-	sock_put(sk);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(tcp_abort);

net/ipv4/tcp_diag.c

@@ -54,11 +54,16 @@ static int tcp_diag_destroy(struct sk_buff *in_skb,
 {
 	struct net *net = sock_net(in_skb->sk);
 	struct sock *sk = inet_diag_find_one_icsk(net, &tcp_hashinfo, req);
+	int err;
 
 	if (IS_ERR(sk))
 		return PTR_ERR(sk);
 
-	return sock_diag_destroy(sk, ECONNABORTED);
+	err = sock_diag_destroy(sk, ECONNABORTED);
+
+	sock_gen_put(sk);
+
+	return err;
 }
 #endif