[PATCH] drm/fb-helper: Fix potential NULL pointer dereference

From: "Gustavo A. R. Silva" <garsilva@embeddedor.com>
To: Daniel Vetter <daniel.vetter@intel.com>,
	Jani Nikula <jani.nikula@linux.intel.com>,
	Gustavo Padovan <gustavo@padovan.org>,
	Sean Paul <seanpaul@chromium.org>,
	David Airlie <airlied@linux.ie>
Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
	"Gustavo A. R. Silva" <garsilva@embeddedor.com>
Subject: [PATCH] drm/fb-helper: Fix potential NULL pointer dereference
Date: Tue, 5 Dec 2017 11:46:28 -0600	[thread overview]
Message-ID: <20171205174628.GA31189@embeddedor.com> (raw)

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>
---
 drivers/gpu/drm/drm_fb_helper.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 6654f2f..04a3a5c 100644
--- 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_connector);
  */
 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_connectors(struct drm_fb_helper *fb_helper)
 	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) {
-- 
2.7.4
