linux-kernel - Re: [PATCH 08/12] driver-core: Introduce DEVICE_ATTR_ADMIN

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Date:   Fri, 26 Jun 2020 07:06:11 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     linux-nvdimm@...ts.01.org,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        vishal.l.verma@...el.com, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 08/12] driver-core: Introduce DEVICE_ATTR_ADMIN_{RO,RW}

On Thu, Jun 25, 2020 at 04:51:03PM -0700, Dan Williams wrote:
> A common pattern for using plain DEVICE_ATTR() instead of
> DEVICE_ATTR_RO() and DEVICE_ATTR_RW() is for attributes that want to
> limit read to only root.  I.e. many users of DEVICE_ATTR() are
> specifying 0400 or 0600 for permissions.
> 
> Given the expectation that CAP_SYS_ADMIN is needed to access these
> sensitive attributes and an explicit helper with the _ADMIN_ identifier
> for DEVICE_ATTR_ADMIN_{RO,RW}.
> 
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> ---
>  include/linux/device.h |    4 ++++
>  include/linux/sysfs.h  |    7 +++++++
>  2 files changed, 11 insertions(+)
> 
> diff --git a/include/linux/device.h b/include/linux/device.h
> index 15460a5ac024..d7c2570368fa 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -128,8 +128,12 @@ ssize_t device_store_bool(struct device *dev, struct device_attribute *attr,
>  		__ATTR_PREALLOC(_name, _mode, _show, _store)
>  #define DEVICE_ATTR_RW(_name) \
>  	struct device_attribute dev_attr_##_name = __ATTR_RW(_name)
> +#define DEVICE_ATTR_ADMIN_RW(_name) \
> +	struct device_attribute dev_attr_##_name = __ATTR_RW_MODE(_name, 0600)
>  #define DEVICE_ATTR_RO(_name) \
>  	struct device_attribute dev_attr_##_name = __ATTR_RO(_name)
> +#define DEVICE_ATTR_ADMIN_RO(_name) \
> +	struct device_attribute dev_attr_##_name = __ATTR_RO_MODE(_name, 0400)
>  #define DEVICE_ATTR_WO(_name) \
>  	struct device_attribute dev_attr_##_name = __ATTR_WO(_name)
>  #define DEVICE_ULONG_ATTR(_name, _mode, _var) \
> diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
> index 86067dbe7745..34e84122f635 100644
> --- a/include/linux/sysfs.h
> +++ b/include/linux/sysfs.h
> @@ -123,6 +123,13 @@ struct attribute_group {
>  	.show	= _name##_show,						\
>  }
>  
> +#define __ATTR_RW_MODE(_name, _mode) {					\
> +	.attr	= { .name = __stringify(_name),				\
> +		    .mode = VERIFY_OCTAL_PERMISSIONS(_mode) },		\
> +	.show	= _name##_show,						\
> +	.store	= _name##_store,					\
> +}
> +
>  #define __ATTR_WO(_name) {						\
>  	.attr	= { .name = __stringify(_name), .mode = 0200 },		\
>  	.store	= _name##_store,					\
> 

Nice!  Want me to take this now, I know of many other places that could
be cleaned up to use this (like the raw device bug that I just fixed...)

If not:

Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>