linux-kernel - Re: [PATCH v1 02/11] landlock: Reduce the maximum number of layers to 16

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Message-ID: <CAHC9VhSAc37rX1jFNpvRczkvbfdALYkP2xm3jPbAm8Eqnp9erw@mail.gmail.com>
Date:   Wed, 16 Mar 2022 21:26:16 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     Mickaël Salaün <mic@...ikod.net>
Cc:     James Morris <jmorris@...ei.org>,
        "Serge E . Hallyn" <serge@...lyn.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Jann Horn <jannh@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Konstantin Meskhidze <konstantin.meskhidze@...wei.com>,
        Shuah Khan <shuah@...nel.org>, linux-doc@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        Mickaël Salaün <mic@...ux.microsoft.com>
Subject: Re: [PATCH v1 02/11] landlock: Reduce the maximum number of layers to 16

On Mon, Feb 21, 2022 at 4:15 PM Mickaël Salaün <mic@...ikod.net> wrote:
>
> From: Mickaël Salaün <mic@...ux.microsoft.com>
>
> The maximum number of nested Landlock domains is currently 64.  Because
> of the following fix and to help reduce the stack size, let's reduce it
> to 16.  This seems large enough for a lot of use cases (e.g. sandboxed
> init service, spawning a sandboxed SSH service, in nested sandboxed
> containers).  Reducing the number of nested domains may also help to
> discover misuse of Landlock (e.g. creating a domain per rule).
>
> Add and use a dedicated layer_mask_t typedef to fit with the number of
> layers.  This might be useful when changing it and to keep it consistent
> with the maximum number of layers.
>
> Signed-off-by: Mickaël Salaün <mic@...ux.microsoft.com>
> Link: https://lore.kernel.org/r/20220221212522.320243-3-mic@digikod.net
> ---
>  security/landlock/fs.c                     | 13 +++++--------
>  security/landlock/limits.h                 |  2 +-
>  security/landlock/ruleset.h                |  4 ++++
>  tools/testing/selftests/landlock/fs_test.c |  2 +-
>  4 files changed, 11 insertions(+), 10 deletions(-)

I'm assuming that the drop in Landlock nesting down to 16 isn't going
to cause any userspace breakage :)

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


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