disp: msm: sde: protect file private structure with mutex lock

Access file private data structures inside the
mutex lock only to avoid use-after-free issues.

Change-Id: If70731f517bcb47d4515f131fecafe702064cb45
Signed-off-by: Krishna Manikandan <[email protected]>

msm/msm_drv.c

@@ -1443,7 +1443,7 @@ void msm_mode_object_event_notify(struct drm_mode_object *obj,
 
 static int msm_release(struct inode *inode, struct file *filp)
 {
-	struct drm_file *file_priv = filp->private_data;
+	struct drm_file *file_priv;
 	struct drm_minor *minor;
 	struct drm_device *dev;
 	struct msm_drm_private *priv;
@@ -1455,6 +1455,7 @@ static int msm_release(struct inode *inode, struct file *filp)
 
 	mutex_lock(&msm_release_lock);
 
+	file_priv = filp->private_data;
 	if (!file_priv) {
 		ret = -EINVAL;
 		goto end;