[PATCH V31 25/25] debugfs: Disable open() when kernel is locked down
luto at kernel.org
Wed Mar 27 04:29:14 UTC 2019
On Tue, Mar 26, 2019 at 5:31 PM Greg KH <gregkh at linuxfoundation.org> wrote:
> On Tue, Mar 26, 2019 at 12:20:24PM -0700, Andy Lutomirski wrote:
> > 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?
> Useful for what? Debugging, sure, but for "normal operation", no kernel
> functionality should ever require debugfs. If it does, that's a bug and
> should be fixed.
I semi-regularly read files in debugfs to diagnose things, and I think
it would be good for this to work on distro kernels.
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