linux-kernel - Re: [PATCH 0/2] exec: Use sane stack rlimit for setuid exec

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Date:   Fri, 7 Jul 2017 15:10:58 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Andy Lutomirski <luto@...nel.org>,
        David Howells <dhowells@...hat.com>,
        Serge Hallyn <serge@...lyn.com>,
        John Johansen <john.johansen@...onical.com>,
        Casey Schaufler <casey@...aufler-ca.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Michal Hocko <mhocko@...nel.org>,
        Ben Hutchings <ben@...adent.org.uk>,
        Hugh Dickins <hughd@...gle.com>,
        Oleg Nesterov <oleg@...hat.com>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Rik van Riel <riel@...hat.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        James Morris <james.l.morris@...cle.com>,
        Greg Ungerer <gerg@...ux-m68k.org>,
        Ingo Molnar <mingo@...nel.org>,
        Nicolas Pitre <nicolas.pitre@...aro.org>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        Paul Moore <paul@...l-moore.com>,
        Vivek Goyal <vgoyal@...hat.com>,
        Mickaël Salaün <mic@...ikod.net>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        LSM List <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH 0/2] exec: Use sane stack rlimit for setuid exec

On Fri, Jul 7, 2017 at 1:09 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> On Fri, Jul 7, 2017 at 1:04 PM, Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
>>
>> It looks like Kees went through the security modules [..]
>
> i take that back. It looks like Kees looked at smack, but not at
> SElinux, for example.

Well, I looked at the all but misthought about SELinux.

> selinux_bprm_secureexec() seems to just look at current_security(),
> not at the new stuff in bprm at all.

I was looking for cred. Yeah, I'll see what should happen here...

> Which would seem to be exactly the wrong thing to do, and is insane
> (why pass in bprm at all?) but comes from the fact that we used to
> call bprm_secureexec() in an insane place.
>
> So I think this patch series is sadly broken - I think it does the
> right thing, but the security modules definitely look like they need
> to be updated for that right thing.

Yeah, I'll rev this once SELinux is more clear...

-Kees

-- 
Kees Cook
Pixel Security