linux-kernel - Re: [PATCH] Lock down drivers that can have io ports, io mem, irqs and dma changed

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Message-ID: <20161123192143.GA482@light.dominikbrodowski.net>
Date:   Wed, 23 Nov 2016 20:21:43 +0100
From:   Dominik Brodowski <linux@...inikbrodowski.net>
To:     David Howells <dhowells@...hat.com>
Cc:     keyrings@...r.kernel.org, matthew.garrett@...ula.com,
        linux-security-module@...r.kernel.org, linux-efi@...r.kernel.org,
        linux-kernel@...r.kernel.org, gnomes@...rguk.ukuu.org.uk
Subject: Re: [PATCH] Lock down drivers that can have io ports, io mem, irqs
 and dma changed

On Wed, Nov 23, 2016 at 12:58:26PM +0000, David Howells wrote:
> Dominik Brodowski <linux@...inikbrodowski.net> wrote:
> 
> > You might also need to disable CIS overrides and CIS firmware loading for
> > PCMCIA drivers, I presume. That needs two changes:
> > 
> > 	- Abort in drivers/pcmcia/ds.c::pcmcia_load_firmware() or disable
> > 	  the CONFIG_PCMCIA_LOAD_CIS config option permanently.
> 
> This really ought to be handled through signature checking in
> request_firmware().
> 
> > 	- Abort in drivers/pcmcia/cistpl.c::pccard_store_cis() or remove
> > 	  write access to the "cis" file in
> > 	  drivers/pcmcia/cistpl.c::pccard_cis_attr
> 
> What is that doing?  Allowing the device to be reconfigured?

Exactly. It is a different interface for updating the firmware -- which
includes ioports etc. In theory, any access should be limited to areas which
are registered to the bridge devices. But you never know...

Best
	Dominik