From: "Gustavo A. R. Silva" <garsilva@embeddedor.com>
Date: Tue, 5 Dec 2017 11:46:28 -0600
Subject: drm/fb-helper: Fix potential NULL pointer dereference
Git-commit: 89f3f35620c7f244880485de11079cb4d98ed604
Patch-mainline: v4.16-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

fb_helper is being dereferenced before it is null checked,
hence there is a potential null pointer dereference.

Fix this by moving the pointer dereference after fb_helper
has been null checked.

This issue was detected with the help of Coccinelle.

Fixes: c777990fb45b ("drm/fb-helper: Handle function NULL argument")
Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20171205174628.GA31189@embeddedor.com

Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/drm_fb_helper.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -178,7 +178,7 @@ EXPORT_SYMBOL(drm_fb_helper_add_one_conn
  */
 int drm_fb_helper_single_add_all_connectors(struct drm_fb_helper *fb_helper)
 {
-	struct drm_device *dev = fb_helper->dev;
+	struct drm_device *dev;
 	struct drm_connector *connector;
 	struct drm_connector_list_iter conn_iter;
 	int i, ret = 0;
@@ -186,6 +186,8 @@ int drm_fb_helper_single_add_all_connect
 	if (!drm_fbdev_emulation || !fb_helper)
 		return 0;
 
+	dev = fb_helper->dev;
+
 	mutex_lock(&fb_helper->lock);
 	drm_connector_list_iter_begin(dev, &conn_iter);
 	drm_for_each_connector_iter(connector, &conn_iter) {