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

[Andy Lutomirski]

On Tue, Mar 26, 2019 at 11:28 AM Matthew Garrett
<matthewgarrett at google.com> wrote:
>
> From: Matthew Garrett <mjg59 at google.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?