linux-kernel - Re: [PATCH 3/5] Add the ability to lock down access to the running kernel image

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Message-ID: <fa6647c3-baff-d9e9-8ffe-89042b2a553d@schaufler-ca.com>
Date:   Thu, 25 May 2017 11:18:22 -0700
From:   Casey Schaufler <casey@...aufler-ca.com>
To:     David Howells <dhowells@...hat.com>
Cc:     ard.biesheuvel@...aro.org, matthew.garrett@...ula.com,
        linux-security-module@...r.kernel.org, linux-efi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] Add the ability to lock down access to the running
 kernel image

On 5/24/2017 11:53 PM, David Howells wrote:
> Casey Schaufler <casey@...aufler-ca.com> wrote:
>
>>> +#ifdef CONFIG_LOCK_DOWN_KERNEL
>>> +extern bool kernel_is_locked_down(void);
>>> +#else
>>> +static inline bool kernel_is_locked_down(void)
>> Should this be a bool or an int? I can imagine that someone is going to want
>> various different degrees of lock down for kernels. As an int you could
>> return a bitmap indicating which features were locked. This would allow
>> additional things to be locked down without changing the interface.
> At the moment it makes no difference, since the return value is only ever
> passed directly to an if-statement.
>
> Also, do you have an idea as to how is should be divided up?

You called out five distinct features in 0/5, so how about
a bit for each of those?

Actually, I don't care which way you go. The current code works
for me. I am just concerned that the granularity fiends might come
around later.


>
> There aren't so many cases, at least not yet, that they can't be fixed up,
> perhaps with a coccinelle script.
>
> David
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