linux-kernel - Re: [PATCH v1] driver: base: Add driver filter support

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Date:   Thu, 5 Aug 2021 09:50:29 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc:     Andi Kleen <ak@...ux.intel.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Dan Williams <dan.j.williams@...el.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH v1] driver: base: Add driver filter support

On Wed, Aug 04, 2021 at 01:09:07PM -0700, Kuppuswamy, Sathyanarayanan wrote:
> 
> 
> On 8/4/21 12:50 PM, Andi Kleen wrote:
> > 
> > > And what's wrong with the current method of removing drivers from
> > > devices that you do not want them to be bound to?  We offer that support
> > > for all busses now that want to do it, what driver types are you needing
> > > to "control" here that does not take advantage of the existing
> > > infrastructure that we currently have for this type of thing?
> > 
> > I'm not sure what mechanism you're referring to here, but in general
> > don't want the drivers to initialize at all because they might get
> > exploited in any code that they execute.The intention is to disable all
> > drivers except for a small allow list, because it's not practical to
> > harden all 25M lines of Linux code.
> 
> Yes, we are not trying to remove the drivers via sysfs. If driver
> filter is enabled, "allowed" sysfs file is used to view the driver
> filter status (allowed/denied). And a write to that file changes
> the allowed/denied status of the driver. It has nothing to do
> with bind/unbind operations.

Again, we have this already today, with full sysfs control in userspace.
Why add yet-another-way to do this?  What is lacking in the existing
functionality that needs to be expanded on?

greg k-h