linux-kernel - [PATCH 0/2] exec: Remove the computation of bprm->cred

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Date:   Fri, 29 May 2020 11:45:19 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     <linux-kernel@...r.kernel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>, Jann Horn <jannh@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Greg Ungerer <gerg@...ux-m68k.org>,
        Rob Landley <rob@...dley.net>,
        Bernd Edlinger <bernd.edlinger@...mail.de>,
        <linux-fsdevel@...r.kernel.org>, Al Viro <viro@...IV.linux.org.uk>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Casey Schaufler <casey@...aufler-ca.com>,
        linux-security-module@...r.kernel.org,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Andy Lutomirski <luto@...capital.net>
Subject: [PATCH 0/2] exec: Remove the computation of bprm->cred

My last chunk of cleanups was clearly too a bit too big, with too many
issues going on so let's try this again with just the most important
cleanup.

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.

Building upon my previous exec clean up work this set of changes splits
per_clear temporarily into two separate flags which is the last step in
causing the code to recompute everything each time a new bprm->file is
considered. Then the code is refactored to run the credential from file
calculation later so that recomputation is not necessary.

Doing this in two steps should allow anyone who has problems later to
bisect and tell if it was the semantic change or the refactoring that
caused them problems.

Eric W. Biederman (2):
      exec: Add a per bprm->file version of per_clear
      exec: Compute file based creds only once

 fs/binfmt_misc.c              |  2 +-
 fs/exec.c                     | 57 ++++++++++++++++++-------------------------
 include/linux/binfmts.h       |  9 ++-----
 include/linux/lsm_hook_defs.h |  2 +-
 include/linux/lsm_hooks.h     | 22 +++++++++--------
 include/linux/security.h      |  9 ++++---
 security/commoncap.c          | 22 +++++++++--------
 security/security.c           |  4 +--
 8 files changed, 59 insertions(+), 68 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