linux-kernel - Re: [PATCH V8 0/2] printk: hash addresses printed with %p

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1509415728.26592.40.camel@perches.com>
Date:   Mon, 30 Oct 2017 19:08:48 -0700
From:   Joe Perches <joe@...ches.com>
To:     "Tobin C. Harding" <me@...in.cc>, Kees Cook <keescook@...omium.org>
Cc:     kernel-hardening@...ts.openwall.com,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Theodore Ts'o <tytso@....edu>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Tycho Andersen <tycho@...ker.com>,
        "Roberts, William C" <william.c.roberts@...el.com>,
        Tejun Heo <tj@...nel.org>,
        Jordan Glover <Golden_Miller83@...tonmail.ch>,
        Greg KH <gregkh@...uxfoundation.org>,
        Petr Mladek <pmladek@...e.com>,
        Ian Campbell <ijc@...lion.org.uk>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <wilal.deacon@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Chris Fries <cfries@...gle.com>,
        Dave Weinstein <olorin@...gle.com>,
        Daniel Micay <danielmicay@...il.com>,
        Djalal Harouni <tixxdz@...il.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V8 0/2] printk: hash addresses printed with %p

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@...in.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.