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

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Message-ID: <20161124201939.GA3782@isilmar-4.linta.de>
Date:   Thu, 24 Nov 2016 21:19:39 +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 Thu, Nov 24, 2016 at 05:34:45PM +0000, David Howells wrote:
> Dominik Brodowski <linux@...inikbrodowski.net> wrote:
> 
> > > > 	- 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...
> 
> Ah, I see.  Should this be using request_firmware()?

For most cases, request_firmware() is being used -- for some rare cases,
however, this alternative interface is provided for. It should be pretty
safe nowadays to make pccard_cis_attr read-only (and who uses PCMCIA
nowadays anyway?).

Best,
	Dominik