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From: ebiederm@xmission.com (Eric W. Biederman)
To: <linux-kernel@vger.kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Oleg Nesterov <oleg@redhat.com>, Jann Horn <jannh@google.com>,
	Kees Cook <keescook@chromium.org>,
	Greg Ungerer <gerg@linux-m68k.org>, Rob Landley <rob@landley.net>,
	Bernd Edlinger <bernd.edlinger@hotmail.de>,
	<linux-fsdevel@vger.kernel.org>,
	Al Viro <viro@ZenIV.linux.org.uk>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Casey Schaufler <casey@schaufler-ca.com>,
	linux-security-module@vger.kernel.org,
	James Morris <jmorris@namei.org>,
	"Serge E. Hallyn" <serge@hallyn.com>,
	Andy Lutomirski <luto@amacapital.net>
Subject: [PATCH  0/11] exec: cred calculation simplifications
Date: Thu, 28 May 2020 10:38:28 -0500
Message-ID: <87k10wysqz.fsf_-_@x220.int.ebiederm.org> (raw)
In-Reply-To: <877dx822er.fsf_-_@x220.int.ebiederm.org> (Eric W. Biederman's message of "Mon, 18 May 2020 19:29:00 -0500")


Recomputing the uids, gids, capabilities, and related flags each time a
new bprm->file is set is error prone, and as it turns out unnecessary.

Further our decisions on when to clear personality bits and when to tell
userspace privileges have been gained so please be extra careful, is
imperfect and our current code overshoots in inconsistent ways making
it hard to understand what is happening, and why.

Building upon my previous exec clean up work this set of changes moves
the bprm->cred calculations a little later so they only need to be done
once, moves all of the uid and gid handling into bprm_fill_uid, and
then cleans up setting secureexec and per_clear so they happen when they
make sense from a semantic perspective.

One of the largest challenges is dealing with how we revert the
credential change if it is discovered the process calling exec is
ptraced and the tracer does not have enough credentials.  It looks
like that code was tacked on as an after thought to a bug fix that
went into 2.4.0-prerelease.

I don't know if we have ever gotten all of the details just right when
the credentials are rolled back.  So this set of changes causes the
credentials not to be changed when ptraced, instead of attempting to
rollback the credential change.

Folks please give this code a review and let me know if you see
anything.

Eric W. Biederman (11):
      exec: Reduce bprm->per_clear to a single bit
      exec: Introduce active_per_clear the per file version of per_clear
      exec: Compute file based creds only once
      exec: Move uid/gid handling from creds_from_file into bprm_fill_uid
      exec: In bprm_fill_uid use CAP_SETGID to see if a gid change is safe
      exec: Don't set secureexec when the uid or gid changes are abandoned
      exec: Set saved, fs, and effective ids together in bprm_fill_uid
      exec: In bprm_fill_uid remove unnecessary no new privs check
      exec: In bprm_fill_uid only set per_clear when honoring suid or sgid
      exec: In bprm_fill_uid set secureexec at same time as per_clear
      exec: Remove the label after_setid from bprm_fill_uid

 fs/binfmt_misc.c              |  2 +-
 fs/exec.c                     | 95 +++++++++++++++++++++++++------------------
 include/linux/binfmts.h       | 13 +++---
 include/linux/lsm_hook_defs.h |  2 +-
 include/linux/lsm_hooks.h     | 21 ++++++----
 include/linux/security.h      |  8 ++--
 security/apparmor/domain.c    |  2 +-
 security/commoncap.c          | 37 ++++++-----------
 security/security.c           |  4 +-
 security/selinux/hooks.c      |  2 +-
 security/smack/smack_lsm.c    |  2 +-
 11 files changed, 98 insertions(+), 90 deletions(-)

---

This builds upon my previous exec cleanup work at:
git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace.git exec-next

Thank you,
Eric

  parent reply index

Thread overview: 108+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <87h7wujhmz.fsf@x220.int.ebiederm.org>
     [not found] ` <87sgga6ze4.fsf@x220.int.ebiederm.org>
2020-05-09 19:40   ` [PATCH 0/5] exec: Control flow simplifications Eric W. Biederman
2020-05-09 19:40     ` [PATCH 1/5] exec: Call cap_bprm_set_creds directly from prepare_binprm Eric W. Biederman
2020-05-09 20:04       ` Linus Torvalds
2020-05-09 19:41     ` [PATCH 2/5] exec: Directly call security_bprm_set_creds from __do_execve_file Eric W. Biederman
2020-05-09 20:07       ` Linus Torvalds
2020-05-09 20:12         ` Eric W. Biederman
2020-05-09 20:19           ` Linus Torvalds
2020-05-11  3:15       ` Kees Cook
2020-05-11 16:52         ` Eric W. Biederman
2020-05-11 21:18           ` Kees Cook
2020-05-09 19:41     ` [PATCH 3/5] exec: Remove recursion from search_binary_handler Eric W. Biederman
2020-05-09 20:16       ` Linus Torvalds
2020-05-10  4:22       ` Tetsuo Handa
2020-05-10 19:38         ` Linus Torvalds
2020-05-11 14:33           ` Eric W. Biederman
2020-05-11 19:10             ` Rob Landley
2020-05-13 21:59               ` Eric W. Biederman
2020-05-14 18:46                 ` Rob Landley
2020-05-11 21:55             ` Kees Cook
2020-05-12 18:42               ` Eric W. Biederman
2020-05-12 19:25                 ` Kees Cook
2020-05-12 20:31                   ` Eric W. Biederman
2020-05-12 23:08                     ` Kees Cook
2020-05-12 23:47                       ` Kees Cook
2020-05-12 23:51                         ` Kees Cook
2020-05-14 14:56                           ` Eric W. Biederman
2020-05-14 16:56                             ` Casey Schaufler
2020-05-14 17:02                               ` Eric W. Biederman
2020-05-13  0:20                 ` Linus Torvalds
2020-05-13  2:39                   ` Rob Landley
2020-05-13 19:51                     ` Linus Torvalds
2020-05-14 16:49                   ` Eric W. Biederman
2020-05-09 19:42     ` [PATCH 4/5] exec: Allow load_misc_binary to call prepare_binfmt unconditionally Eric W. Biederman
2020-05-11 22:09       ` Kees Cook
2020-05-09 19:42     ` [PATCH 5/5] exec: Move the call of prepare_binprm into search_binary_handler Eric W. Biederman
2020-05-11 22:24       ` Kees Cook
2020-05-19  0:29     ` [PATCH v2 0/8] exec: Control flow simplifications Eric W. Biederman
2020-05-19  0:29       ` [PATCH v2 1/8] exec: Teach prepare_exec_creds how exec treats uids & gids Eric W. Biederman
2020-05-19 18:03         ` Kees Cook
2020-05-19 18:28           ` Linus Torvalds
2020-05-19 18:57             ` Eric W. Biederman
2020-05-19  0:30       ` [PATCH v2 2/8] exec: Factor security_bprm_creds_for_exec out of security_bprm_set_creds Eric W. Biederman
2020-05-19 15:34         ` Casey Schaufler
2020-05-19 18:10         ` Kees Cook
2020-05-19 21:28           ` James Morris
2020-05-19  0:31       ` [PATCH v2 3/8] exec: Convert security_bprm_set_creds into security_bprm_repopulate_creds Eric W. Biederman
2020-05-19 18:21         ` Kees Cook
2020-05-19 19:03           ` Eric W. Biederman
2020-05-19 19:14             ` Kees Cook
2020-05-20 20:22               ` Eric W. Biederman
2020-05-20 20:53                 ` Kees Cook
2020-05-19 21:52         ` James Morris
2020-05-20 12:40           ` Eric W. Biederman
2020-05-19  0:31       ` [PATCH v2 4/8] exec: Allow load_misc_binary to call prepare_binfmt unconditionally Eric W. Biederman
2020-05-19 18:27         ` Kees Cook
2020-05-19 19:08           ` Eric W. Biederman
2020-05-19 19:17             ` Kees Cook
2020-05-19  0:32       ` [PATCH v2 5/8] exec: Move the call of prepare_binprm into search_binary_handler Eric W. Biederman
2020-05-19 18:27         ` Kees Cook
2020-05-19 21:30         ` James Morris
2020-05-19  0:33       ` [PATCH v2 6/8] exec/binfmt_script: Don't modify bprm->buf and then return -ENOEXEC Eric W. Biederman
2020-05-19 19:08         ` Kees Cook
2020-05-19 19:19           ` Eric W. Biederman
2020-05-19  0:33       ` [PATCH v2 7/8] exec: Generic execfd support Eric W. Biederman
2020-05-19 19:46         ` Kees Cook
2020-05-19 19:54           ` Linus Torvalds
2020-05-19 20:20             ` Eric W. Biederman
2020-05-19 21:59         ` Rob Landley
2020-05-20 16:05           ` Eric W. Biederman
2020-05-21 22:50             ` Rob Landley
2020-05-22  3:28               ` Eric W. Biederman
2020-05-22  4:51                 ` Rob Landley
2020-05-22 13:35                   ` Eric W. Biederman
2020-05-19  0:34       ` [PATCH v2 8/8] exec: Remove recursion from search_binary_handler Eric W. Biederman
2020-05-19 20:37         ` Kees Cook
2020-05-19  1:25       ` [PATCH v2 0/8] exec: Control flow simplifications Linus Torvalds
2020-05-19 21:55       ` Kees Cook
2020-05-20 13:02         ` Eric W. Biederman
2020-05-20 22:12       ` Eric W. Biederman
2020-05-20 23:43         ` Kees Cook
2020-05-21 11:53           ` Eric W. Biederman
2020-05-28 15:38       ` Eric W. Biederman [this message]
2020-05-28 15:41         ` [PATCH 01/11] exec: Reduce bprm->per_clear to a single bit Eric W. Biederman
2020-05-28 19:04           ` Linus Torvalds
2020-05-28 19:17             ` Eric W. Biederman
2020-05-28 15:42         ` [PATCH 02/11] exec: Introduce active_per_clear the per file version of per_clear Eric W. Biederman
2020-05-28 19:05           ` Linus Torvalds
2020-05-28 15:42         ` [PATCH 03/11] exec: Compute file based creds only once Eric W. Biederman
2020-05-28 15:43         ` [PATCH 04/11] exec: Move uid/gid handling from creds_from_file into bprm_fill_uid Eric W. Biederman
2020-05-28 15:44         ` Eric W. Biederman
2020-05-28 15:44         ` [PATCH 05/11] exec: In bprm_fill_uid use CAP_SETGID to see if a gid change is safe Eric W. Biederman
2020-05-28 15:48         ` [PATCH 06/11] exec: Don't set secureexec when the uid or gid changes are abandoned Eric W. Biederman
2020-05-28 15:48         ` [PATCH 07/11] exec: Set saved, fs, and effective ids together in bprm_fill_uid Eric W. Biederman
2020-05-28 15:49         ` [PATCH 08/11] exec: In bprm_fill_uid remove unnecessary no new privs check Eric W. Biederman
2020-05-28 15:49         ` [PATCH 09/11] exec: In bprm_fill_uid only set per_clear when honoring suid or sgid Eric W. Biederman
2020-05-28 19:08           ` Linus Torvalds
2020-05-28 19:21             ` Eric W. Biederman
2020-05-28 15:50         ` [PATCH 10/11] exec: In bprm_fill_uid set secureexec at same time as per_clear Eric W. Biederman
2020-05-28 15:50         ` [PATCH 11/11] exec: Remove the label after_setid from bprm_fill_uid Eric W. Biederman
2020-05-29 16:45         ` [PATCH 0/2] exec: Remove the computation of bprm->cred Eric W. Biederman
2020-05-29 16:46           ` [PATCH 1/2] exec: Add a per bprm->file version of per_clear Eric W. Biederman
2020-05-29 21:06             ` Kees Cook
2020-05-30  3:23               ` Eric W. Biederman
2020-05-30  5:14                 ` Kees Cook
2020-05-29 16:47           ` [PATCH 2/2] exec: Compute file based creds only once Eric W. Biederman
2020-05-29 21:24             ` Kees Cook
2020-05-30  3:28               ` Eric W. Biederman
2020-05-30  5:18                 ` Kees Cook

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