Re: [Patch 04/12] GRU - collect per-context user statistics

[Andrew Morton <akpm@linux-foundation.org>]

On Mon, 08 Jun 2009 12:16:52 -0500
steiner@sgi.com wrote:

>  /*
> + * Fetch GSEG statisticss
> + */
> +long gru_get_gseg_statistics(unsigned long arg)
> +{
> +	struct gru_thread_state *gts;
> +	struct gru_get_gseg_statistics_req req;
> +
> +	if (copy_from_user(&req, (void __user *)arg, sizeof(req)))
> +		return -EFAULT;
> +
> +	gts = gru_find_lock_gts(req.gseg);
> +	if (gts) {
> +		memcpy(&req.stats, &gts->ustats, sizeof(gts->ustats));
> +		gru_unlock_gts(gts);
> +	} else {
> +		memset(&req.stats, 0, sizeof(gts->ustats));
> +	}
> +
> +	if (copy_to_user((void __user *)arg, &req, sizeof(req)))
> +		return -EFAULT;
> +
> +	return 0;
> +}

So..  what's happening in the super-secret undocumented gts==NULL path?

It _looks_ like userspace passed into this ioctl a handle for something
which the kernel doesn't know about.  If so, shouldn't we return
-EINVAL or something?