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From: Kees Cook <keescook@chromium.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Kees Cook <keescook@chromium.org>,
        Andy Lutomirski <luto@kernel.org>,
        David Howells <dhowells@redhat.com>,
        Serge Hallyn <serge@hallyn.com>,
        John Johansen <john.johansen@canonical.com>,
        Casey Schaufler <casey@schaufler-ca.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Michal Hocko <mhocko@kernel.org>,
        Ben Hutchings <ben@decadent.org.uk>,
        Hugh Dickins <hughd@google.com>,
        Oleg Nesterov <oleg@redhat.com>,
        "Jason A. Donenfeld" <Jason@zx2c4.com>,
        Rik van Riel <riel@redhat.com>,
        James Morris <james.l.morris@oracle.com>,
        Greg Ungerer <gerg@linux-m68k.org>,
        Ingo Molnar <mingo@kernel.org>,
        Nicolas Pitre <nicolas.pitre@linaro.org>,
        Stephen Smalley <sds@tycho.nsa.gov>,
        Paul Moore <paul@paul-moore.com>,
        Vivek Goyal <vgoyal@redhat.com>,
        =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= <mic@digikod.net>,
        Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-security-module@vger.kernel.org, selinux@tycho.nsa.gov
Subject: [PATCH v2 0/8] exec: Use sane stack rlimit under secureexec
Date: Mon, 10 Jul 2017 00:57:23 -0700
Message-Id: <1499673451-66160-1-git-send-email-keescook@chromium.org>
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-fsdevel.vger.kernel.org>

As discussed with Linus and Andy, we need to reset the stack rlimit
before we do memory layouts when execing a privilege-gaining (e.g.
setuid) program. This moves security_bprm_secureexec() earlier (with
required changes), and then lowers the stack limit when appropriate.

As a side-effect, dumpability and pdeath_signal clearing is expanded
to cover LSM definitions of secureexec (and Smack can drop its special
handler for pdeath_signal clearing).

I'd appreciate some extra eyes on this to make sure this isn't
broken in some special way. I couldn't find anything that _depended_
on security_bprm_secureexec() being called late.

Thanks!

-Kees

v2:
- fix missed current_security() uses in LSMs.
- research/consolidate dumpability setting logic
- research/consolidate pdeath_signal clearing logic
- split up logical steps a little more for easier review (and bisection)
- fix some old broken comments