netdev - Re: [PATCH net-next v3 2/8] gtp: switch from struct socket to struct sock for the GTP sockets

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Message-Id: <20170215.110726.1948359807046911436.davem@davemloft.net>
Date:   Wed, 15 Feb 2017 11:07:26 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     aschultz@...p.net
Cc:     pablo@...filter.org, netdev@...r.kernel.org, laforge@...monks.org,
        Lionel.Gauthier@...ecom.fr, osmocom-net-gprs@...ts.osmocom.org,
        jonas@...thpole.se
Subject: Re: [PATCH net-next v3 2/8] gtp: switch from struct socket to
 struct sock for the GTP sockets

From: Andreas Schultz <aschultz@...p.net>
Date: Wed, 15 Feb 2017 08:04:56 +0100 (CET)

> ----- On Feb 14, 2017, at 6:48 PM, David S. Miller davem@...emloft.net wrote:
> 
>> From: Andreas Schultz <aschultz@...p.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.
> 
> I don't understand how this should happen. If I where to use rcu_assign_pointer,
> then yes, but rcu_assign_sk_user_data does assign to the sk_user_data member
> of struct sock and not to the argument itself.

You are right, I misread the assignment.