[PATCH] drm/xen-front: Fix error code in xen_drm_front_gem_get_sg_table()

[Dan Carpenter]

The xen_drm_front_gem_get_sg_table() function is supposed to return
error pointer.  The current code, would trigger a NULL dereference in
drm_gem_map_dma_buf().

Fixes: c575b7eeb89f ("drm/xen-front: Add support for Xen PV display frontend")
Signed-off-by: Dan Carpenter <dan.carpenter at oracle.com>

diff --git a/drivers/gpu/drm/xen/xen_drm_front_gem.c b/drivers/gpu/drm/xen/xen_drm_front_gem.c
index c85bfe7571cb..4507bc03ed8f 100644
--- a/drivers/gpu/drm/xen/xen_drm_front_gem.c
+++ b/drivers/gpu/drm/xen/xen_drm_front_gem.c
@@ -179,7 +179,7 @@ struct sg_table *xen_drm_front_gem_get_sg_table(struct drm_gem_object *gem_obj)
 	struct xen_gem_object *xen_obj = to_xen_gem_obj(gem_obj);
 
 	if (!xen_obj->pages)
-		return NULL;
+		return ERR_PTR(-EINVAL);
 
 	return drm_prime_pages_to_sg(xen_obj->pages, xen_obj->num_pages);
 }