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 S1754504AbdGJQ2A (ORCPT <rfc822;w@1wt.eu>);
        Mon, 10 Jul 2017 12:28:00 -0400
Received: from mx2.suse.de ([195.135.220.15]:37174 "EHLO mx1.suse.de"
        rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP
        id S1754159AbdGJQ17 (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Mon, 10 Jul 2017 12:27:59 -0400
Date: Mon, 10 Jul 2017 18:27:52 +0200
From: Michal Hocko <mhocko@kernel.org>
To: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        Andy Lutomirski <luto@kernel.org>, Ben Hutchings <ben@decadent.org.uk>,
        Willy Tarreau <w@1wt.eu>, Hugh Dickins <hughd@google.com>,
        Oleg Nesterov <oleg@redhat.com>,
        "Jason A. Donenfeld" <Jason@zx2c4.com>, Rik van Riel <riel@redhat.com>,
        Larry Woodman <lwoodman@redhat.com>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Tony Luck <tony.luck@intel.com>,
        "James E.J. Bottomley" <jejb@parisc-linux.org>,
        Helge Diller <deller@gmx.de>, James Hogan <james.hogan@imgtec.com>,
        Laura Abbott <labbott@redhat.com>, Greg KH <greg@kroah.com>,
        "security@kernel.org" <security@kernel.org>,
        Qualys Security Advisory <qsa@qualys.com>,
        LKML <linux-kernel@vger.kernel.org>, Ximin Luo <infinity0@debian.org>
Subject: Re: [RFC][PATCH] exec: Use init rlimits for setuid exec
Message-ID: <20170710162751.GC7071@dhcp22.suse.cz>
References: <20170706043235.GA36170@beast>
 <CA+55aFwwvJRTvpDBZ2KsXvRB_EWEcHesuXmHgSJFB3PTMBd1Bg@mail.gmail.com>
 <CAGXu5jJ8_tTZGmS9mA6d5G+FBy0uj8=XHrOTs15NYnDjgCE=iQ@mail.gmail.com>
 <CA+55aFz+ZexQFWwLXLprDaz-VcGCZmHed0vr-+=jsKrdMDAKLA@mail.gmail.com>
 <CAGXu5jK9U8Wo=u0N4cZY_xt9TJ5Hyd2O4buxHu5eAqjCUz-PoA@mail.gmail.com>
 <20170710084415.GE19185@dhcp22.suse.cz>
 <CAGXu5jK5m1pVSon=uGy=dLgVi89k33+Lm-XHZ4xiNY-QdUxtng@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAGXu5jK5m1pVSon=uGy=dLgVi89k33+Lm-XHZ4xiNY-QdUxtng@mail.gmail.com>
User-Agent: Mutt/1.5.23 (2014-03-12)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Mon 10-07-17 09:12:11, Kees Cook wrote:
> On Mon, Jul 10, 2017 at 1:44 AM, Michal Hocko <mhocko@kernel.org> wrote:
> > On Thu 06-07-17 12:12:55, Kees Cook wrote:
> >> On Thu, Jul 6, 2017 at 10:52 AM, Linus Torvalds
> >> <torvalds@linux-foundation.org> wrote:
> >> > On Thu, Jul 6, 2017 at 10:29 AM, Kees Cook <keescook@chromium.org> wrote:
> >> >>>
> >> >>>  (a) minimal: just use our existing default stack (and stack _only_)
> >> >>> limit value for suid binaries that actually get extra permissions: {
> >> >>> _STK_LIM, RLIM_INFINITY }.
> >> >>
> >> >> This would look a lot like the existing patch; it'd just not copy the
> >> >> init process rlimits.
> >> >
> >> > Can't we just do the final rlimit setting so late in execve that we
> >> > don't need that whole "saved_rlimit" thing?
> >>
> >> The stack rlimit defines the mmap layout too:
> >>
> >> do_execveat_common() ->
> >> exec_binprm() ->
> >> search_binary_handler() ->
> >> fmt->load_binary (load_elf_binary()) ->
> >> setup_new_exec() ->
> >> arch_pick_mmap_layout() ->
> >> mmap_is_legacy() ->
> >> rlimit(RLIMIT_STACK) == RLIM_INFINITY
> >
> > FWIW this is gone in tip tree. See
> > lkml.kernel.org/r/20170614082218.12450-1-mhocko@kernel.org
> 
> Sounds good to me, but won't large-memory users in 32-bit get annoyed?

Why would they? 32b do bottom up layouts by default.
-- 
Michal Hocko
SUSE Labs