linux-kernel - Re: [PATCH V31 25/25] debugfs: Disable open() when kernel is locked down

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Date:   Tue, 26 Mar 2019 12:20:24 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Matthew Garrett <matthewgarrett@...gle.com>
Cc:     James Morris <jmorris@...ei.org>,
        LSM List <linux-security-module@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        David Howells <dhowells@...hat.com>,
        Linux API <linux-api@...r.kernel.org>,
        Andrew Lutomirski <luto@...nel.org>,
        Matthew Garrett <mjg59@...gle.com>,
        Greg KH <gregkh@...uxfoundation.org>
Subject: Re: [PATCH V31 25/25] debugfs: Disable open() when kernel is locked down

On Tue, Mar 26, 2019 at 11:28 AM Matthew Garrett
<matthewgarrett@...gle.com> wrote:
>
> From: Matthew Garrett <mjg59@...gle.com>
>
> debugfs has not been meaningfully audited in terms of ensuring that
> userland cannot trample over the kernel. At Greg's request, disable
> access to it entirely when the kernel is locked down. This is done at
> open() time rather than init time as the kernel lockdown status may be
> made stricter at runtime.

Ugh.  Some of those files are very useful.  Could this perhaps still
allow O_RDONLY if we're in INTEGRITY mode?