linux-kernel - Re: [PATCH v2 0/8] exec: Control flow simplifications

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Date:   Wed, 20 May 2020 08:02:51 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Kees Cook <keescook@...omium.org>
Cc:     linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>, Jann Horn <jannh@...gle.com>,
        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>,
        Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH v2 0/8] exec: Control flow simplifications

Kees Cook <keescook@...omium.org> writes:

> On Mon, May 18, 2020 at 07:29:00PM -0500, Eric W. Biederman wrote:
>>  arch/alpha/kernel/binfmt_loader.c  | 11 +----
>>  fs/binfmt_elf.c                    |  4 +-
>>  fs/binfmt_elf_fdpic.c              |  4 +-
>>  fs/binfmt_em86.c                   | 13 +----
>>  fs/binfmt_misc.c                   | 69 ++++-----------------------
>>  fs/binfmt_script.c                 | 82 ++++++++++++++------------------
>>  fs/exec.c                          | 97 ++++++++++++++++++++++++++------------
>>  include/linux/binfmts.h            | 36 ++++++--------
>>  include/linux/lsm_hook_defs.h      |  3 +-
>>  include/linux/lsm_hooks.h          | 52 +++++++++++---------
>>  include/linux/security.h           | 14 ++++--
>>  kernel/cred.c                      |  3 ++
>>  security/apparmor/domain.c         |  7 +--
>>  security/apparmor/include/domain.h |  2 +-
>>  security/apparmor/lsm.c            |  2 +-
>>  security/commoncap.c               |  9 ++--
>>  security/security.c                |  9 +++-
>>  security/selinux/hooks.c           |  8 ++--
>>  security/smack/smack_lsm.c         |  9 ++--
>>  security/tomoyo/tomoyo.c           | 12 ++---
>>  20 files changed, 202 insertions(+), 244 deletions(-)
>
> Oh, BTW, heads up on this (trivially but annoyingly) conflicting with
> the copy_strings_kernel/copy_string/kernel change:
>
> https://ozlabs.org/~akpm/mmotm/broken-out/exec-simplify-the-copy_strings_kernel-calling-convention.patch
>
> Is it worth pulling that and these into your tree?
>
> https://ozlabs.org/~akpm/mmotm/broken-out/exec-open-code-copy_string_kernel.patch
>
> https://ozlabs.org/~akpm/mmotm/broken-out/umh-fix-refcount-underflow-in-fork_usermode_blob.patch

Good question.  It is part of the greater set_fs removal work, and I
don't want to mess that up.

I would love to give copy_string_kernel a length parameter so
binfmt_script did not have to modify it's buffer or copy the string,
before calling copy_string_kernel.

Hmm.  I already have to call strdup on i_name in brpm_change_interp.
So I probably just want to bite the bullet and figure out a way to do
strdup earlier.

So unless it makes things easier for Andrew I think it is probably
easier to live with the conflict for now, and use this conversation
as inspiration for my next round of cleanups of binfmt_misc.

Eric