msm: vidc: Set file private data to NULL on close

Set file private data to NULL on closing instance
to avoid invalid access after close.

Change-Id: I447791463d9dbe32e25237256589bb07be2c3a32
Signed-off-by: Surajit Podder <spodder@codeaurora.org>

drivers/media/platform/msm/vidc/msm_v4l2_vidc.c

@@ -1,4 +1,4 @@
-/* Copyright (c) 2012-2017, The Linux Foundation. All rights reserved.
+/* Copyright (c) 2012-2018, The Linux Foundation. All rights reserved.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 and
@@ -39,6 +39,8 @@ struct msm_vidc_drv *vidc_driver;
 
 static inline struct msm_vidc_inst *get_vidc_inst(struct file *filp, void *fh)
 {
+	if (!filp->private_data)
+		return NULL;
 	return container_of(filp->private_data,
 					struct msm_vidc_inst, event_handler);
 }
@@ -74,6 +76,7 @@ static int msm_v4l2_close(struct file *filp)
 	vidc_inst = get_vidc_inst(filp, NULL);
 
 	rc = msm_vidc_close(vidc_inst);
+	filp->private_data = NULL;
 	trace_msm_v4l2_vidc_close_end("msm_v4l2_close end");
 	return rc;
 }