linux-kernel - Re: [PATCH 15/24] asus-wmi: Restrict debugfs interface when the kernel is locked down

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Message-ID: <31421.1491569449@warthog.procyon.org.uk>
Date:   Fri, 07 Apr 2017 13:50:49 +0100
From:   David Howells <dhowells@...hat.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     dhowells@...hat.com,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        matthew.garrett@...ula.com, linux-efi@...r.kernel.org,
        One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        acpi4asus-user <acpi4asus-user@...ts.sourceforge.net>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        linux-security-module <linux-security-module@...r.kernel.org>,
        keyrings@...r.kernel.org
Subject: Re: [PATCH 15/24] asus-wmi: Restrict debugfs interface when the kernel is locked down

Andy Shevchenko <andy.shevchenko@...il.com> wrote:

> > From: Matthew Garrett <matthew.garrett@...ula.com>
> >
> > We have no way of validating what all of the Asus WMI methods do on a given
> > machine - and there's a risk that some will allow hardware state to be
> > manipulated in such a way that arbitrary code can be executed in the
> > kernel, circumventing module loading restrictions.  Prevent that if the
> > kernel is locked down.
> 
> > +       if (kernel_is_locked_down())
> > +               return -EPERM;
> 
> It looks a bit fragile when responsility of whatever reasons kernel
> can't serve become a driver burden.
> Can we fix this in debugfs framework instead?

Fix it with debugfs how?  We can't offload the decision to userspace.

David