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Date: Mon, 10 Jul 2017 10:44:15 +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>,
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Subject: Re: [RFC][PATCH] exec: Use init rlimits for setuid exec
Message-ID: <20170710084415.GE19185@dhcp22.suse.cz>
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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

-- 
Michal Hocko
SUSE Labs