Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751763AbdGaXvt (ORCPT ); Mon, 31 Jul 2017 19:51:49 -0400 Received: from mail-pf0-f169.google.com ([209.85.192.169]:36677 "EHLO mail-pf0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751352AbdGaXvq (ORCPT ); Mon, 31 Jul 2017 19:51:46 -0400 From: Kees Cook To: Andrew Morton Cc: Kees Cook , David Howells , "Eric W. Biederman" , John Johansen , "Serge E. Hallyn" , Paul Moore , Stephen Smalley , Casey Schaufler , Tetsuo Handa , James Morris , Andy Lutomirski , Linus Torvalds , linux-fsdevel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v4 00/15] exec: Use sane stack rlimit under secureexec Date: Mon, 31 Jul 2017 16:51:18 -0700 Message-Id: <1501545093-56634-1-git-send-email-keescook@chromium.org> X-Mailer: git-send-email 2.7.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4334 Lines: 94 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. To do this, we need to know the results of the bprm_secureexec hook before memory layouts. As it turns out, this can be made _mostly_ trivial by collapsing bprm_secureexec into bprm_set_creds. The LSMs using bprm_secureexec nearly always save state between bprm_set_creds and bprm_secureexec. In the face of multiple calls to bprm_set_creds (via prepare_binprm() calls from binfmt_script, etc), all LSMs except commoncap only pay attention to the first call, so that aligns well with collapsing bprm_secureexec into bprm_set_creds. The commoncaps, though, needs to check the _last_ bprm_set_creds, so this series just swaps one bprm flag for another (cap_effective is no longer needed to save state between bprm_set_creds and bprm_secureexec, but we do need to keep a separate state, so we add the cap_elevated flag). Once secureexec is available to setup_new_exec() before the memory layout, we can add an rlimit sanity-check for setuid execs. (With no need to clean up since we're past the point of no return.) Along the way, this fixes comments, renames a variable, and consolidates dumpability and pdeath_signal clearing, which includes some commit log archeology to examine the subtle differences between what we had and what we need. Several folks have looked at this already (thank you!) but I'd appreciate any other eyes on this to make sure it isn't broken in some special way. Looking at the diffstat, even after all my long comments, this is a net reduction in lines. :) Given this crosses a bunch of areas, I think this is likely best to go via the -mm tree, which is where nearly all of my prior exec work has lived too. It's also after rc2 at this point, so I'd be slightly nervous to see this land directly in Linus's tree, but I leave that decision up to Linus. :) Regardless, very little has changed between v3 and v4, so I think this is ready to go. Thanks! -Kees ---------------------------------------------------------------- Kees Cook (15): exec: Rename bprm->cred_prepared to called_set_creds exec: Correct comments about "point of no return" binfmt: Introduce secureexec flag apparmor: Refactor to remove bprm_secureexec hook selinux: Refactor to remove bprm_secureexec hook smack: Refactor to remove bprm_secureexec hook commoncap: Refactor to remove bprm_secureexec hook commoncap: Move cap_elevated calculation into bprm_set_creds LSM: drop bprm_secureexec hook exec: Use secureexec for setting dumpability exec: Use secureexec for clearing pdeath_signal smack: Remove redundant pdeath_signal clearing exec: Consolidate dumpability logic exec: Use sane stack rlimit under secureexec exec: Consolidate pdeath_signal clearing fs/binfmt_elf.c | 2 +- fs/binfmt_elf_fdpic.c | 2 +- fs/binfmt_flat.c | 2 +- fs/exec.c | 56 ++++++++++++++++++++++++++++---------- include/linux/binfmts.h | 24 ++++++++++++---- include/linux/lsm_hooks.h | 14 ++++------ include/linux/security.h | 7 ----- security/apparmor/domain.c | 24 ++-------------- security/apparmor/include/domain.h | 1 - security/apparmor/include/file.h | 3 -- security/apparmor/lsm.c | 1 - security/commoncap.c | 50 ++++++++-------------------------- security/security.c | 5 ---- security/selinux/hooks.c | 26 ++++-------------- security/smack/smack_lsm.c | 34 ++--------------------- security/tomoyo/tomoyo.c | 2 +- 16 files changed, 91 insertions(+), 162 deletions(-) v4: - add {Ack,Review,Test}ed-bys - reorder patches to move trivial refactoring to the front - move secureexec flag set earlier in the series to setup_new_exec(); amluto v3: - collapse brpm_secureexec into bprm_set_creds; ebiederm. - continue to improve various comments 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