linux-kernel - Re: [PATCH V33 01/30] security: Support early LSMs

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Message-ID: <CACdnJusxhsYenacOEJkDXqVC13qoEd5eNXDgxWT_x8tz4bV5cQ@mail.gmail.com>
Date:   Fri, 21 Jun 2019 12:27:46 -0700
From:   Matthew Garrett <mjg59@...gle.com>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     James Morris <jmorris@...ei.org>, linux-security@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>
Subject: Re: [PATCH V33 01/30] security: Support early LSMs

On Thu, Jun 20, 2019 at 10:23 PM Andy Lutomirski <luto@...nel.org> wrote:
>
> On Thu, Jun 20, 2019 at 6:22 PM Matthew Garrett
> <matthewgarrett@...gle.com> wrote:
> >
> > The lockdown module is intended to allow for kernels to be locked down
> > early in boot - sufficiently early that we don't have the ability to
> > kmalloc() yet. Add support for early initialisation of some LSMs, and
> > then add them to the list of names when we do full initialisation later.
>
> I'm confused.  What does it even mean to lock down the kernel before
> we're ready to run userspace code?  We can't possibly be attacked by
> user code before there is any to attack us.

Certain kernel parameters can be disabled by lockdown, so we want to
have policy available before that parsing happens.