linux-kernel - Re: [PATCH 23/27] bpf: Restrict kernel image access functions when the kernel is locked down

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Message-ID: <CACdnJuskoACijaifrNQhqRtr07uPN7LT8m=FNgcxgJRiwDLVkw@mail.gmail.com>
Date:   Tue, 26 Mar 2019 13:19:10 -0700
From:   Matthew Garrett <mjg59@...gle.com>
To:     James Morris <jmorris@...ei.org>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Linux API <linux-api@...r.kernel.org>,
        LSM List <linux-security-module@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        David Howells <dhowells@...hat.com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Network Development <netdev@...r.kernel.org>,
        Chun-Yi Lee <jlee@...e.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kees Cook <keescook@...omium.org>,
        Will Drewry <wad@...omium.org>
Subject: Re: [PATCH 23/27] bpf: Restrict kernel image access functions when
 the kernel is locked down

On Tue, Mar 26, 2019 at 11:57 AM James Morris <jmorris@...ei.org> wrote:
> - Assign an ID to each lockdown point
> - Implement a policy mechanism where each ID is mapped to 0 or 1
> - Allow this policy to be specified statically or dynamically

One of the problems with this approach is what the default behaviour
should be when a new feature is added. If an admin fails to notice
that there's now a new policy element, they run the risk of kernel
integrity being compromised via the new feature even if the rest of
the kernel is locked down.