vhost-vdpa: return -EFAULT on copy_to_user() failure

The copy_to_user() function returns the number of bytes remaining to be
copied.  However, we need to return a negative error code, -EFAULT, to
the user.

Fixes: 87f4c217413a ("vhost-vdpa: introduce uAPI to get the number of virtqueue groups")
Fixes: e96ef636f154 ("vhost-vdpa: introduce uAPI to get the number of address spaces")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Message-Id: <YotG1vXKXXSayr63@kili>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>

drivers/vhost/vdpa.c

@@ -609,11 +609,13 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
 		r = vhost_vdpa_get_vring_num(v, argp);
 		break;
 	case VHOST_VDPA_GET_GROUP_NUM:
-		r = copy_to_user(argp, &v->vdpa->ngroups,
-				 sizeof(v->vdpa->ngroups));
+		if (copy_to_user(argp, &v->vdpa->ngroups,
+				 sizeof(v->vdpa->ngroups)))
+			r = -EFAULT;
 		break;
 	case VHOST_VDPA_GET_AS_NUM:
-		r = copy_to_user(argp, &v->vdpa->nas, sizeof(v->vdpa->nas));
+		if (copy_to_user(argp, &v->vdpa->nas, sizeof(v->vdpa->nas)))
+			r = -EFAULT;
 		break;
 	case VHOST_SET_LOG_BASE:
 	case VHOST_SET_LOG_FD: