drm: fix error routines in drm_open_helper

There are missing parts to handle error in drm_open_helper().
The priv->minor, assigned by idr_find() which can return NULL,
should be checked whether it is NULL or not before referencing it.
put_pid(), drm_gem_release(), and drm_prime_destory_file_private()
should be called when error happens after their pair functions are
called. If an error occurs after executing dev->driver->open()
which allocates driver specific per-file private data, then the
private data should be released.

Signed-off-by: YoungJun Cho <[e-mail]>
Signed-off-by: Seung-Woo Kim <[e-mail]>
Signed-off-by: Kyungmin Park <[e-mail]>
Reviewed-by: Chris Wilson <chris-wilson.co.uk>
Signed-off-by: Dave Airlie <[e-mail]>

drivers/gpu/drm/drm_fops.c

···
 	priv->uid = current_euid();
 	priv->pid = get_pid(task_pid(current));
 	priv->minor = idr_find(&drm_minors_idr, minor_id);
+	if (!priv->minor) {
+		ret = -ENODEV;
+		goto out_put_pid;
+	}
+
 	priv->ioctl_count = 0;
 	/* for compatibility root is always authenticated */
 	priv->authenticated = capable(CAP_SYS_ADMIN);
···
 	if (dev->driver->open) {
 		ret = dev->driver->open(dev, priv);
 		if (ret < 0)
-			goto out_free;
+			goto out_prime_destroy;
 	}
 
 
···
 		if (!priv->minor->master) {
 			mutex_unlock(&dev->struct_mutex);
 			ret = -ENOMEM;
-			goto out_free;
+			goto out_close;
 		}
 
 		priv->is_master = 1;
···
 				drm_master_put(&priv->minor->master);
 				drm_master_put(&priv->master);
 				mutex_unlock(&dev->struct_mutex);
-				goto out_free;
+				goto out_close;
 			}
 		}
 		mutex_lock(&dev->struct_mutex);
···
 				drm_master_put(&priv->minor->master);
 				drm_master_put(&priv->master);
 				mutex_unlock(&dev->struct_mutex);
-				goto out_free;
+				goto out_close;
 			}
 		}
 		mutex_unlock(&dev->struct_mutex);
···
 #endif
 
 	return 0;
-      out_free:
+
+out_close:
+	if (dev->driver->postclose)
+		dev->driver->postclose(dev, priv);
+out_prime_destroy:
+	if (drm_core_check_feature(dev, DRIVER_PRIME))
+		drm_prime_destroy_file_private(&priv->prime);
+	if (dev->driver->driver_features & DRIVER_GEM)
+		drm_gem_release(dev, priv);
+out_put_pid:
+	put_pid(priv->pid);
 	kfree(priv);
 	filp->private_data = NULL;
 	return ret;