linux-kernel - Re: [PATCH security-next v4 23/32] selinux: Remove boot parameter

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Message-ID: <809f1cfd-077b-ee58-51ba-b22daf46d12b@tycho.nsa.gov>
Date:   Tue, 2 Oct 2018 10:58:15 -0400
From:   Stephen Smalley <sds@...ho.nsa.gov>
To:     Kees Cook <keescook@...omium.org>
Cc:     Paul Moore <paul@...l-moore.com>, James Morris <jmorris@...ei.org>,
        Casey Schaufler <casey@...aufler-ca.com>,
        John Johansen <john.johansen@...onical.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        "Schaufler, Casey" <casey.schaufler@...el.com>,
        linux-security-module <linux-security-module@...r.kernel.org>,
        Jonathan Corbet <corbet@....net>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH security-next v4 23/32] selinux: Remove boot parameter

On 10/02/2018 10:44 AM, Kees Cook wrote:
> On Tue, Oct 2, 2018 at 6:42 AM, Stephen Smalley <sds@...ho.nsa.gov> wrote:
>> On 10/02/2018 08:12 AM, Paul Moore wrote:
>>>
>>> On Mon, Oct 1, 2018 at 9:04 PM Kees Cook <keescook@...omium.org> wrote:
>>>>
>>>> Since LSM enabling is now centralized with CONFIG_LSM_ENABLE and
>>>> "lsm.enable=...", this removes the LSM-specific enabling logic from
>>>> SELinux.
>>>>
>>>> Signed-off-by: Kees Cook <keescook@...omium.org>
>>>> ---
>>>>    .../admin-guide/kernel-parameters.txt         |  9 ------
>>>>    security/selinux/Kconfig                      | 29 -------------------
>>>>    security/selinux/hooks.c                      | 15 +---------
>>>>    3 files changed, 1 insertion(+), 52 deletions(-)
>>>>
>>>> diff --git a/Documentation/admin-guide/kernel-parameters.txt
>>>> b/Documentation/admin-guide/kernel-parameters.txt
>>>> index cf963febebb0..0d10ab3d020e 100644
>>>> --- a/Documentation/admin-guide/kernel-parameters.txt
>>>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>>>> @@ -4045,15 +4045,6 @@
>>>>                           loaded. An invalid security module name will be
>>>> treated
>>>>                           as if no module has been chosen.
>>>>
>>>> -       selinux=        [SELINUX] Disable or enable SELinux at boot time.
>>>> -                       Format: { "0" | "1" }
>>>> -                       See security/selinux/Kconfig help text.
>>>> -                       0 -- disable.
>>>> -                       1 -- enable.
>>>> -                       Default value is set via kernel config option.
>>>> -                       If enabled at boot time, /selinux/disable can be
>>>> used
>>>> -                       later to disable prior to initial policy load.
>>>
>>>
>>> No comments yet on the rest of the patchset, but the subject line of
>>> this patch caught my eye and I wanted to comment quickly on this one
>>> ...
>>>
>>> Not a fan unfortunately.
>>>
>>> Much like the SELinux bits under /proc/self/attr, this is a user
>>> visible thing which has made its way into a lot of docs, scripts, and
>>> minds; I believe removing it would be a big mistake.
>>
>>
>> Yes, we can't suddenly break existing systems that had selinux=0 in their
>> grub config.  We have to retain the support.
> 
> Is it okay to only support selinux=0 (instead of also selinux=1)?

For Fedora/RHEL kernels, selinux=1 would be redundant since it is the 
default.  However, in other distros where SELinux is not the default, I 
think they have documented selinux=1 as the way to enable SELinux.  So 
users may be relying on that as well. I don't think we can safely drop 
support for either one.  Sorry.