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 S1754026AbdJaXQ1 (ORCPT <rfc822;w@1wt.eu>);
        Tue, 31 Oct 2017 19:16:27 -0400
Received: from out4-smtp.messagingengine.com ([66.111.4.28]:52711 "EHLO
        out4-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK)
        by vger.kernel.org with ESMTP id S1752319AbdJaXQZ (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Tue, 31 Oct 2017 19:16:25 -0400
X-ME-Sender: <xms:RgT5WevboXaGSgNOzty_68eD-VDpRlUUJPyghhpKm9ZqbtNhpEiy7Q>
Date: Wed, 1 Nov 2017 10:16:19 +1100
From: "Tobin C. Harding" <me@tobin.cc>
To: Joe Perches <joe@perches.com>
Cc: Kees Cook <keescook@chromium.org>, kernel-hardening@lists.openwall.com,
        "Jason A. Donenfeld" <Jason@zx2c4.com>,
        "Theodore Ts'o" <tytso@mit.edu>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Paolo Bonzini <pbonzini@redhat.com>, Tycho Andersen <tycho@docker.com>,
        "Roberts, William C" <william.c.roberts@intel.com>,
        Tejun Heo <tj@kernel.org>,
        Jordan Glover <Golden_Miller83@protonmail.ch>,
        Greg KH <gregkh@linuxfoundation.org>, Petr Mladek <pmladek@suse.com>,
        Ian Campbell <ijc@hellion.org.uk>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <wilal.deacon@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>, Chris Fries <cfries@google.com>,
        Dave Weinstein <olorin@google.com>,
        Daniel Micay <danielmicay@gmail.com>,
        Djalal Harouni <tixxdz@gmail.com>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH V8 0/2] printk: hash addresses printed with %p
Message-ID: <20171031231619.GB3585@eros>
References: <1508986436-31966-1-git-send-email-me@tobin.cc>
 <CAGXu5jJvBKd2i-P4LVW_mHY9e3j4JEpaR4=a7dt3CcOvimcuTQ@mail.gmail.com>
 <20171030223346.GX12341@eros>
 <1509415728.26592.40.camel@perches.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1509415728.26592.40.camel@perches.com>
X-Mailer: Mutt 1.5.24 (2015-08-30)
User-Agent: Mutt/1.5.24 (2015-08-30)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Mon, Oct 30, 2017 at 07:08:48PM -0700, Joe Perches wrote:
> On Tue, 2017-10-31 at 09:33 +1100, Tobin C. Harding wrote:
> > On Mon, Oct 30, 2017 at 03:03:21PM -0700, Kees Cook wrote:
> > > On Wed, Oct 25, 2017 at 7:53 PM, Tobin C. Harding <me@tobin.cc> wrote:
> > > > Here is the behaviour that this set implements.
> > > > 
> > > > For kpt_restrict==0
> > > > 
> > > > Randomness not ready:
> > > >   printed with %p:              (pointer)          # NOTE: with padding
> > > > Valid pointer:
> > > >   printed with %pK:             deadbeefdeadbeef
> > > >   printed with %p:              0xdeadbeef
> > > >   malformed specifier (eg %i):  0xdeadbeef
> > > 
> > > I really think we can't include SPECIAL unless _every_ callsite of %p
> > > is actually doing "0x%p", and then we're replacing all of those. We're
> > > not doing that, though...
> > > 
> > > $ git grep '%p\b' | wc -l
> > > 12766
> > > $ git grep '0x%p\b' | wc -l
> > > 18370x
> > > 
> > > If we need some kind of special marking that this is a hashed
> > > variable, that should be something other than "0x". If we're using the
> > > existing "(null)" and new "(pointer)" text, maybe "(hash:xxxxxx)"
> > > should be used instead? Then the (rare) callers with 0x become
> > > "0x(hash:xxxx)" and naked callers produce "(hash:xxxx)".
> > > 
> > > I think the first step for this is to just leave SPECIAL out.
> > 
> > Thanks Kees. V9 leaves SPECIAL out. Also V9 prints the whole 64 bit
> > address with the first 32 bits masked to zero. The intent being to _not_
> > change the output format from what it currently is. So it will look like
> > this; 
> > 
> > 	00000000c09e81d0
> > 
> > What do you think?
> > 
> > Amusingly I think this whole conversation is going to come up again
> > when we do %pa, in inverse, since %pa currently does us SPECIAL.
> 
> I once sent a patch set to remove SPECIAL from %pa
> and add 0x where necessary.
> 
> https://patchwork.kernel.org/patch/3875471/
> 
> After that didn't happen, I removed the duplicated
> 0x%pa with a sed.
> 
> https://patchwork.kernel.org/patch/8509421/
> 
> Sending a treewide sed patch would be fine with me.

Cool, thanks Joe I'll keep this in mind for when we get to %pa.

thanks,
Tobin.