netdev - Re: [PATCH net] datagram: When peeking datagrams with offset

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Date:   Wed, 16 Aug 2017 19:40:04 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Paolo Abeni <pabeni@...hat.com>
Cc:     Matthew Dawson <matthew@...systems.ca>,
        Network Development <netdev@...r.kernel.org>,
        "Macieira, Thiago" <thiago.macieira@...el.com>
Subject: Re: [PATCH net] datagram: When peeking datagrams with offset < 0
 don't skip empty skbs

>  static inline int sk_peek_offset(struct sock *sk, int flags)
>  {
> -       if (unlikely(flags & MSG_PEEK)) {
> -               s32 off = READ_ONCE(sk->sk_peek_off);
> -               if (off >= 0)
> -                       return off;
> -       }
> +       if (unlikely(flags & MSG_PEEK))
> +               return READ_ONCE(sk->sk_peek_off);
>
>         return 0;
>  }

I noticed too late that this function is used in one case where the
result is not blindly passed to __skb_try_recv_from_queue.

The AF_UNIX stream case will need a floor on its offset.

-               skip = sk_peek_offset(sk, flags);
+               skip = max(sk_peek_offset(sk, flags), 0);