From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S934171AbcBBUo5 (ORCPT <rfc822;w@1wt.eu>);
	Tue, 2 Feb 2016 15:44:57 -0500
Received: from mail-ig0-f194.google.com ([209.85.213.194]:35554 "EHLO
	mail-ig0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S932865AbcBBUoy (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Tue, 2 Feb 2016 15:44:54 -0500
MIME-Version: 1.0
In-Reply-To: <56B11278.8000805@stressinduktion.org>
References: <201601100657.u0A6vk1B025554@mail.home.local>
	<CANq1E4T0sqTTD4RsWXTUrFvsKvEsKsUiPbskWd=wAEVu83_Srg@mail.gmail.com>
	<56B0F574.5080105@stressinduktion.org>
	<CA+55aFw2AwsWbvwp6f8H+eExt_CMfh7VA3od6hto_M0hg9z3Tg@mail.gmail.com>
	<56B11278.8000805@stressinduktion.org>
Date: Tue, 2 Feb 2016 12:44:54 -0800
X-Google-Sender-Auth: fc4kt_bwlgstBVYTSwcJATWPa-Q
Message-ID: <CA+55aFz0CXGexEBmb8JU0+w7sFf3VfE3TpRzdj3aTiDxg2zDpg@mail.gmail.com>
Subject: Re: [PATCH v2] unix: properly account for FDs passed over unix sockets
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Hannes Frederic Sowa <hannes@stressinduktion.org>
Cc: David Herrmann <dh.herrmann@gmail.com>, Willy Tarreau <w@1wt.eu>,
        "David S. Miller" <davem@davemloft.net>,
        netdev <netdev@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Eric Dumazet <edumazet@google.com>,
        =?UTF-8?B?0JzQsNGA0Log0JrQvtGA0LXQvdCx0LXRgNCz?= 
	<socketpair@gmail.com>,
        Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
        Simon McVittie <simon.mcvittie@collabora.co.uk>
Content-Type: text/plain; charset=UTF-8
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Tue, Feb 2, 2016 at 12:32 PM, Hannes Frederic Sowa
<hannes@stressinduktion.org> wrote:
>
> Unfortunately we never transfer a scm_cookie via the skbs but merely use it
> to initialize unix_skb_parms structure in skb->cb and destroy it afterwards.

Ok, I obviously didn't check very closely.

> But "struct pid *" in unix_skb_parms should be enough to get us to
> corresponding "struct cred *" so we can decrement the correct counter during
> skb destruction.

Umm. I think the "struct cred" may change in between, can't it?

So I don't think you can later look up the cred based on the pid.

Could we add the cred pointer (or just the user pointer) to the unix_skb_parms?

Or maybe just add it to the "struct scm_fp_list"?

               Linus