Re: [RFC PATCH v3 2/3] vfio: platform: access device property as a list of strings

[Eric Auger <eric.auger@linaro.org>]

On 12/19/2014 10:20 PM, Antonios Motakis wrote:
> Certain device properties (e.g. the device node name, the compatible
> string), are available as a list of strings (separated by the null
> terminating character). Let the VFIO user query this type of properties.
> 
> Signed-off-by: Antonios Motakis <a.motakis@virtualopensystems.com>
> ---
>  drivers/vfio/platform/properties.c | 43 +++++++++++++++++++++++++++++++++++++-
>  1 file changed, 42 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/vfio/platform/properties.c b/drivers/vfio/platform/properties.c
> index 8b90465..39c6342 100644
> --- a/drivers/vfio/platform/properties.c
> +++ b/drivers/vfio/platform/properties.c
> @@ -7,7 +7,48 @@ static int dev_property_get_strings(struct device *dev,
>  				    char *name, unsigned *lenp,
>  				    void __user *datap, unsigned long datasz)
>  {
> -	return -EINVAL;
> +	const char **val;
> +	int n, i, ret;
> +
> +	*lenp = 0;
> +
> +	n = device_property_read_string_array(dev, name, NULL, 0);
> +	if (n < 0)
don't know if n==0 can happen? property found but not value?
> +		return n;
> +
> +	val = kcalloc(n, sizeof(char*), GFP_KERNEL);
char *, checkpatch error.
> +	if (!val)
> +		return -ENOMEM;
> +
> +	ret = device_property_read_string_array(dev, name, val, n);
> +	if (ret < 0)
> +		goto out;
> +
> +	ret = 0;
why not initializing ret at declaration time?
> +
> +	for (i = 0; i < n; i++) {
> +		size_t len = strlen(val[i]) + 1;
> +
> +		if (datasz < len) {
> +			ret = -EOVERFLOW;
> +			while (i < n)
> +				*lenp += strlen(val[i++]) + 1;
why do you set *lenp to the length of all strings even if they can't be
copied?
> +			goto out;
> +		}
> +
> +		if (copy_to_user(datap, val[i], len)) {
> +			ret = -EFAULT;
so in that case *lenp is not incremented?
> +			goto out;
> +		}
Can't you have a similar implementation as for uxx, see next patch
comments. Can't you copy to user in one shot. Can't that code be simplified.
> +
> +		*lenp += len;
> +		datap += len;
> +		datasz -= len;
> +	}
> +
> +out:
> +	kfree(val);
> +	return ret;
>  }
>  
>  static int dev_property_get_uint(struct device *dev, char *name,
>