From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [PATCH net] net/packet: fix a race in packet_bind() and
 packet_notifier()
Date: Tue, 28 Nov 2017 07:14:55 -0800
Message-ID: <1511882095.16595.14.camel@gmail.com>
References: <1511841652.16595.11.camel@gmail.com>
         <20171128.094855.1432729042351719024.davem@davemloft.net>
Mime-Version: 1.0
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 8bit
Cc: netdev@vger.kernel.org, fruggeri@aristanetworks.com,
        willemb@google.com
To: David Miller <davem@davemloft.net>
Return-path: <netdev-owner@vger.kernel.org>
Received: from mail-pg0-f44.google.com ([74.125.83.44]:37331 "EHLO
        mail-pg0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1752050AbdK1PO6 (ORCPT
        <rfc822;netdev@vger.kernel.org>); Tue, 28 Nov 2017 10:14:58 -0500
Received: by mail-pg0-f44.google.com with SMTP id y6so56173pgp.4
        for <netdev@vger.kernel.org>; Tue, 28 Nov 2017 07:14:58 -0800 (PST)
In-Reply-To: <20171128.094855.1432729042351719024.davem@davemloft.net>
Sender: netdev-owner@vger.kernel.org
List-ID: <netdev.vger.kernel.org>

On Tue, 2017-11-28 at 09:48 -0500, David Miller wrote:
> From: Eric Dumazet <eric.dumazet@gmail.com>
> Date: Mon, 27 Nov 2017 20:00:52 -0800
> 
> > @@ -368,9 +368,11 @@ static void __unregister_prot_hook(struct sock
> *sk, bool sync)
> >       __sock_put(sk);
> >  
> >       if (sync) {
> > +             po->frozen = 1;
> >               spin_unlock(&po->bind_lock);
> >               synchronize_net();
> >               spin_lock(&po->bind_lock);
> > +             po->frozen = 0;
> >       }
> >  }
> >  
> 
> Ugh.
> 
> Maybe you can just set po->num to zero in the bind code path which
> causes
> this problem.  That will prevent this situation entirely.

Yes, I can submit a V2 with this idea implemented, thanks.