releases/4.9.85/iio-buffer-check-if-a-buffer-has-been-set-up-when-poll-is-called.patch

From 4cd140bda6494543f1c1b0ccceceaa44b676eef6 Mon Sep 17 00:00:00 2001
From: Stefan Windfeldt-Prytz <stefan.windfeldt@axis.com>
Date: Thu, 15 Feb 2018 15:02:53 +0100
Subject: iio: buffer: check if a buffer has been set up when poll is called

From: Stefan Windfeldt-Prytz <stefan.windfeldt@axis.com>

commit 4cd140bda6494543f1c1b0ccceceaa44b676eef6 upstream.

If no iio buffer has been set up and poll is called return 0.
Without this check there will be a null pointer dereference when
calling poll on a iio driver without an iio buffer.

Cc: stable@vger.kernel.org
Signed-off-by: Stefan Windfeldt-Prytz <stefan.windfeldt@axis.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/iio/industrialio-buffer.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/iio/industrialio-buffer.c
+++ b/drivers/iio/industrialio-buffer.c
@@ -174,7 +174,7 @@ unsigned int iio_buffer_poll(struct file
 	struct iio_dev *indio_dev = filp->private_data;
 	struct iio_buffer *rb = indio_dev->buffer;
 
-	if (!indio_dev->info)
+	if (!indio_dev->info || rb == NULL)
 		return 0;
 
 	poll_wait(filp, &rb->pollq, wait);