linux-kernel - Re: [PATCH] acpi/ec: Deny write access unless requested by module param

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Date:	Wed, 17 Feb 2016 15:27:31 +0100
From:	Thomas Renninger <trenn@...e.de>
To:	green@...uxhacker.ru
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <lenb@...nel.org>, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] acpi/ec: Deny write access unless requested by module param

On Saturday, February 06, 2016 02:08:08 AM green@...uxhacker.ru wrote:
> From: Oleg Drokin <green@...uxhacker.ru>
> 
> In debugfs it's not enough to just set file mode to read-only to
> deny write access to a file, instead just don't provide
> the write method unless write access is really requested.
> 
> Signed-off-by: Oleg Drokin <green@...uxhacker.ru>
Signed-off-by: Thomas Renninger <trenn@...e.com>

Thanks!

> ---
> I assume allowing run-time changes via /sys/module is preferrable,
> opposed to forced module unload and reload to change this option,
> but I can submit another patch to only depend on the module parameter
> too, please let me know.
> 
>  drivers/acpi/ec_sys.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/acpi/ec_sys.c b/drivers/acpi/ec_sys.c
> index bea8e42..6c7dd7a 100644
> --- a/drivers/acpi/ec_sys.c
> +++ b/drivers/acpi/ec_sys.c
> @@ -73,6 +73,9 @@ static ssize_t acpi_ec_write_io(struct file *f, const char
> __user *buf, loff_t init_off = *off;
>  	int err = 0;
> 
> +	if (!write_support)
> +		return -EINVAL;
> +
>  	if (*off >= EC_SPACE_SIZE)
>  		return 0;
>  	if (*off + count >= EC_SPACE_SIZE) {