[PATCH] drm/meson: fix potential NULL pointer exception in meson_drv_unbind()

[Jiajun Cao]

Fix a potential NULL pointer exception when meson_drv_unbind()
attempts to operate on the driver_data priv which may be NULL.
Add a null pointer check on the priv struct to avoid the NULL
pointer dereference after calling dev_get_drvdata(), just like
the null pointer checks done on the struct priv in the function
meson_drv_shutdown(), meson_drv_pm_suspend() and meson_drv_pm_resume().

Signed-off-by: Jiajun Cao <jjcao20 at fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf at gmail.com>
---
 drivers/gpu/drm/meson/meson_drv.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/meson/meson_drv.c b/drivers/gpu/drm/meson/meson_drv.c
index 07fcd12dca16..adea6a2b28f5 100644
--- a/drivers/gpu/drm/meson/meson_drv.c
+++ b/drivers/gpu/drm/meson/meson_drv.c
@@ -380,6 +380,8 @@ static int meson_drv_bind(struct device *dev)
 static void meson_drv_unbind(struct device *dev)
 {
 	struct meson_drm *priv = dev_get_drvdata(dev);
+	if (!priv)
+		return;
 	struct drm_device *drm = priv->drm;
 
 	if (priv->canvas) {
-- 
2.17.1