linux-kernel - Re: [PATCH 07/39] Annotate hardware config module parameters in drivers/cpufreq/

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Date:   Thu, 1 Dec 2016 15:02:15 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     David Howells <dhowells@...hat.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        gnomes@...rguk.ukuu.org.uk, minyard@....org,
        Linux PM <linux-pm@...r.kernel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        linux-security-module@...r.kernel.org, keyrings@...r.kernel.org
Subject: Re: [PATCH 07/39] Annotate hardware config module parameters in drivers/cpufreq/

On Thu, Dec 1, 2016 at 1:30 PM, David Howells <dhowells@...hat.com> 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/cpufreq/.
>
> Suggested-by: One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
> Signed-off-by: David Howells <dhowells@...hat.com>
> cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
> cc: Viresh Kumar <viresh.kumar@...aro.org>
> cc: linux-pm@...r.kernel.org
> ---
>
>  drivers/cpufreq/speedstep-smi.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/cpufreq/speedstep-smi.c b/drivers/cpufreq/speedstep-smi.c
> index 770a9ae1999a..37b30071c220 100644
> --- a/drivers/cpufreq/speedstep-smi.c
> +++ b/drivers/cpufreq/speedstep-smi.c
> @@ -378,7 +378,7 @@ static void __exit speedstep_exit(void)
>         cpufreq_unregister_driver(&speedstep_driver);
>  }
>
> -module_param(smi_port, int, 0444);
> +module_param_hw(smi_port, int, ioport, 0444);
>  module_param(smi_cmd,  int, 0444);
>  module_param(smi_sig, uint, 0444);

Looks OK to me.

Whom do you expect to apply this?

Thanks,
Rafael