netdev - Re: [PATCH net-next 2/2] Add a eBPF helper function to retrieve socket uid

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Date:   Thu, 02 Feb 2017 17:51:48 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Lorenzo Colitti <lorenzo@...gle.com>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        Chenbo Feng <chenbofeng.kernel@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Alexei Starovoitov <ast@...com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Willem de Bruijn <willemb@...gle.com>,
        Chenbo Feng <fengc@...gle.com>
Subject: Re: [PATCH net-next 2/2] Add a eBPF helper function to retrieve
 socket uid

On Fri, 2017-02-03 at 10:18 +0900, Lorenzo Colitti wrote:
> On Fri, Feb 3, 2017 at 9:31 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> >> It should be safe to call sock_net_uid on any type of socket
> >> (including NULL). sk_uid was added to struct sock in 86741ec25462
> >> ("net: core: Add a UID field to struct sock.")
> >
> > But a request socket or a timewait socket do not have this field.
> >
> > Daniel point is valid.
> 
> My bad. Yes.
> 
> It would definitely be useful to have the UID available in request
> sockets, and perhaps timewait sockets as well. That could be done by
> moving the UID to sock_common, or with something along the lines of:
> 
>  static inline kuid_t sock_net_uid(const struct net *net, const struct sock *sk)
>  {
> +       if (sk && sk->sk_state == TCP_NEW_SYN_RECV)
> +               sk = sk->__sk_common.skc_listener;
> +       else if (sk && !sk_fullsock(sk))
> +               sk = NULL;
> +
>         return sk ? sk->sk_uid : make_kuid(net->user_ns, 0);
>  }
> 
> Any thoughts on which is better?

You could use

if (sk) {
    sk = sk_to_full_sk(sk);
    if (sk_fullsock(sk))
        return sk->sk_uid;
}