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References: <20220329125117.1393824-1-mic@digikod.net> <20220329125117.1393824-7-mic@digikod.net>
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From:   Paul Moore <paul@paul-moore.com>
Date:   Thu, 7 Apr 2022 21:19:51 -0400
Message-ID: <CAHC9VhQg0R5ddC_aLSAFyyf9OPs6wSyj3tqh1hwoN=RPpoDFuQ@mail.gmail.com>
Subject: Re: [PATCH v2 06/12] LSM: Remove double path_rename hook calls for RENAME_EXCHANGE
To:     =?UTF-8?B?TWlja2HDq2wgU2FsYcO8bg==?= <mic@digikod.net>
Cc:     James Morris <jmorris@namei.org>,
        "Serge E . Hallyn" <serge@hallyn.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Jann Horn <jannh@google.com>,
        John Johansen <john.johansen@canonical.com>,
        Kees Cook <keescook@chromium.org>,
        Konstantin Meskhidze <konstantin.meskhidze@huawei.com>,
        Shuah Khan <shuah@kernel.org>,
        Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
        linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        linux-security-module@vger.kernel.org,
        Kentaro Takeda <takedakn@nttdata.co.jp>,
        =?UTF-8?B?TWlja2HDq2wgU2FsYcO8bg==?= <mic@linux.microsoft.com>
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On Tue, Mar 29, 2022 at 8:51 AM Micka=C3=ABl Sala=C3=BCn <mic@digikod.net> =
wrote:
>
> From: Micka=C3=ABl Sala=C3=BCn <mic@linux.microsoft.com>
>
> In order to be able to identify a file exchange with renameat2(2) and
> RENAME_EXCHANGE, which will be useful for Landlock [1], propagate the
> rename flags to LSMs.  This may also improve performance because of the
> switch from two set of LSM hook calls to only one, and because LSMs
> using this hook may optimize the double check (e.g. only one lock,
> reduce the number of path walks).
>
> AppArmor, Landlock and Tomoyo are updated to leverage this change.  This
> should not change the current behavior (same check order), except
> (different level of) speed boosts.
>
> [1] https://lore.kernel.org/r/20220221212522.320243-1-mic@digikod.net
>
> Cc: James Morris <jmorris@namei.org>
> Cc: Kentaro Takeda <takedakn@nttdata.co.jp>
> Cc: Paul Moore <paul@paul-moore.com>
> Cc: Serge E. Hallyn <serge@hallyn.com>
> Acked-by: John Johansen <john.johansen@canonical.com>
> Acked-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> Signed-off-by: Micka=C3=ABl Sala=C3=BCn <mic@linux.microsoft.com>
> Link: https://lore.kernel.org/r/20220329125117.1393824-7-mic@digikod.net
> ---
>
> Changes since v1:
> * Import patch from
>   https://lore.kernel.org/r/20220222175332.384545-1-mic@digikod.net
> * Add Acked-by: Tetsuo Handa.
> * Add Acked-by: John Johansen.
> ---
>  include/linux/lsm_hook_defs.h |  2 +-
>  include/linux/lsm_hooks.h     |  1 +
>  security/apparmor/lsm.c       | 30 +++++++++++++++++++++++++-----
>  security/landlock/fs.c        | 12 ++++++++++--
>  security/security.c           |  9 +--------
>  security/tomoyo/tomoyo.c      | 11 ++++++++++-
>  6 files changed, 48 insertions(+), 17 deletions(-)

Seems like a nice improvement to me, and while I'm not an AppArmor,
Tomoyo, or Landlock expert the changes looked pretty straightforward.

Reviewed-by: Paul Moore <paul@paul-moore.com>

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