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

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Message-ID: <13615.1491830208@warthog.procyon.org.uk>
Date:   Mon, 10 Apr 2017 14:16:48 +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:

> >> 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.
> 
> I mean to do at least similar like you have done for module
> parameters. So, instead of putting above code to each attribute in
> question make a special (marked) attribute instead and debugfs
> framework will know how to deal with that.

Hmmm...  It's tricky in that debugfs doesn't have any of its own structures,
but is entirely built on standard VFS ones, so finding somewhere to store the
information is going to be awkward.  One obvious solution is to entirely lock
down debugfs in secure boot more, but that might be a bit drastic.

Note that it's still going to be a driver burden to some extent anyway.  The
driver has to tell the core what needs to be restricted.

Further, I guess configfs needs attention also.

David