linux-kernel - Re: [PATCH 25/39] Annotate hardware config module parameters in drivers/pci/hotplug/

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Date:   Wed, 7 Dec 2016 12:34:55 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     David Howells <dhowells@...hat.com>
Cc:     linux-kernel@...r.kernel.org, Scott Murray <scott@...teful.org>,
        minyard@....org, gnomes@...rguk.ukuu.org.uk,
        linux-pci@...r.kernel.org, linux-security-module@...r.kernel.org,
        keyrings@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH 25/39] Annotate hardware config module parameters in
 drivers/pci/hotplug/

On Thu, Dec 01, 2016 at 12:32:58PM +0000, David Howells wrote:
> When the kernel is running in secure boot mode, we lock down the kernel to
> prevent userspace from modifying the running kernel image.  Whilst this
> includes prohibiting access to things like /dev/mem, it must also prevent
> access by means of configuring driver modules in such a way as to cause a
> device to access or modify the kernel image.
> 
> To this end, annotate module_param* statements that refer to hardware
> configuration and indicate for future reference what type of parameter they
> specify.  The parameter parser in the core sees this information and can
> skip such parameters with an error message if the kernel is locked down.
> The module initialisation then runs as normal, but just sees whatever the
> default values for those parameters is.
> 
> Note that we do still need to do the module initialisation because some
> drivers have viable defaults set in case parameters aren't specified and
> some drivers support automatic configuration (e.g. PNP or PCI) in addition
> to manually coded parameters.
> 
> This patch annotates drivers in drivers/pci/hotplug/.
> 
> Suggested-by: One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
> Signed-off-by: David Howells <dhowells@...hat.com>
> cc: Scott Murray <scott@...teful.org>
> cc: Bjorn Helgaas <bhelgaas@...gle.com>
> cc: linux-pci@...r.kernel.org

Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>

I assume you'll merge this via some non-PCI tree.  Let me know if you
need anything else from me.

> ---
> 
>  drivers/pci/hotplug/cpcihp_generic.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/hotplug/cpcihp_generic.c b/drivers/pci/hotplug/cpcihp_generic.c
> index 88a44a707b96..bbf9cf8aeaad 100644
> --- a/drivers/pci/hotplug/cpcihp_generic.c
> +++ b/drivers/pci/hotplug/cpcihp_generic.c
> @@ -220,7 +220,7 @@ module_param(first_slot, byte, 0);
>  MODULE_PARM_DESC(first_slot, "Hotswap bus first slot number");
>  module_param(last_slot, byte, 0);
>  MODULE_PARM_DESC(last_slot, "Hotswap bus last slot number");
> -module_param(port, ushort, 0);
> +module_param_hw(port, ushort, ioport, 0);
>  MODULE_PARM_DESC(port, "#ENUM signal I/O port");
>  module_param(enum_bit, uint, 0);
>  MODULE_PARM_DESC(enum_bit, "#ENUM signal bit (0-7)");
> 
> --
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