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

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Date:   Wed, 30 Nov 2016 16:25:38 +0000
From:   David Howells <dhowells@...hat.com>
To:     One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
Cc:     dhowells@...hat.com, minyard@....org, jforbes@...hat.com,
        keyrings@...r.kernel.org, matthew.garrett@...ula.com,
        linux-security-module@...r.kernel.org, linux-efi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Lock down drivers that can have io ports, io mem, irqs and dma changed

One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk> wrote:

> > I thought that if I'm changing the module_param annotations anyway then it's
> > probably worth bunging in an extra parameter that notes what the parameter
> > modifies (ioport, iomem, etc.) for future reference, even if we don't store
> > it.
> 
> With a security hat on the security best practice and long standing
> accepted rule is that you whitelist rather than blacklist, so there ought
> to be a 
> 
> module_param_safe_array()
> etc
> 
> to mark parameters that are safe, not the reverse.

Whilst that may be true, it's a lot more work.  Mind you, that said, you can
take the annotations I've made and script the inverse.

> That debate aside I think the patch is exactly what is needed for this,
> and is probably useful for more general hardening as well.

Okay, I've done a preliminary patchset, labelling all the parameters that
appear to be associated with hardware details and pushed them here:

	http://git.kernel.org/cgit/linux/kernel/git/dhowells/linux-fs.git/log/?h=efi-lock-down

The patch that modifies the module parameter header is labelled:

	Lock down module params that specify hardware parameters (eg. ioport)

and all the driver dir lockdown patches follow that.

I still need to do a bit of commenting in that patch and add various
maintainer cc's in the other patches.

David