From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH net-next v3 2/8] gtp: switch from struct socket to
 struct sock for the GTP sockets
Date: Tue, 14 Feb 2017 12:48:15 -0500 (EST)
Message-ID: <20170214.124815.217549517821684819.davem@davemloft.net>
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From: Andreas Schultz <aschultz@tpip.net>
Date: Mon, 13 Feb 2017 16:36:18 +0100

> +	if (gtp->sk0) {
> +		udp_sk(gtp->sk0)->encap_type = 0;
> +		rcu_assign_sk_user_data(gtp->sk0, NULL);
> +		sock_put(gtp->sk0);
>  	}

This does "sock_put(NULL);" because you are assigning gtp->sk0 to
NULL before the sock_put() call.  So you are leaking the socket,
at best.

You need to load the socket pointer into a local variable in order
to do this correctly.