Re: [RFC PATCH v4 2/3] vfio: platform: access device property as a list of strings

[Baptiste Reynal <b.reynal@xxxxxxxxxxxxxxxxxxxxxx>]

On Wed, Sep 9, 2015 at 10:48 PM, Alex Williamson <alex.williamson@xxxxxxxxxx> wrote:

On Wed, 2015-09-09 at 11:17 +0200, Baptiste Reynal wrote:
> From: Antonios Motakis <a.motakis@xxxxxxxxxxxxxxxxxxxxxx>
>
> 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@xxxxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Baptiste Reynal <b.reynal@xxxxxxxxxxxxxxxxxxxxxx>
>
> ---
> v3 -> v4:
>  - The list length is computed before strings copy. If the entire list
>    doesn't fit, no strings are copied to the user.
> ---
>  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 98754c2..8bf9c8f 100644
> --- a/drivers/vfio/platform/properties.c
> +++ b/drivers/vfio/platform/properties.c
> @@ -22,7 +22,48 @@ static int dev_property_get_strings(struct device *dev, uint32_t *flags,
>                                   char *name, unsigned *lenp,
>                                   void __user *datap, unsigned long datasz)
>  {
> -     return -EINVAL;
> +     const char **val;
> +     int n, i, ret;
> +
> +     if (lenp == NULL)
> +             return -EFAULT;

Paranoia?

Kind of, automatic reflex.

 

> +
> +     *lenp = 0;
> +
> +     n = device_property_read_string_array(dev, name, NULL, 0);
> +     if (n < 0)
> +             return n;
> +
> +     val = kcalloc(n, sizeof(char *), GFP_KERNEL);
> +     if (!val)
> +             return -ENOMEM;
> +
> +     ret = device_property_read_string_array(dev, name, val, n);
> +     if (ret < 0)
> +             goto out;
> +
> +     for (i = 0; i < n; i++)
> +             *lenp += strlen(val[i]) + 1;
> +
> +     if (datasz < *lenp) {
> +             ret = -E2BIG;
> +             goto out;
> +     }
> +
> +     for (i = 0; i < n; i++) {
> +             size_t len = strlen(val[i]) + 1;
> +
> +             if (copy_to_user(datap, val[i], strlen(val[i]) + 1)) {

No need to call strlen() again here

Thanks, will be fixed.

 

> +                     ret = -EFAULT;
> +                     goto out;
> +             }
> +
> +             datap += len;
> +     }
> +
> +out:
> +     kfree(val);
> +     return ret;
>  }
>
>  static int dev_property_get_uint(struct device *dev, uint32_t *flags,

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