[PATCH 4.14 23/54] iio: buffer: check if a buffer has been set up when poll is called

[Greg Kroah-Hartman]

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Stefan Windfeldt-Prytz <stefan.windfe...@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: sta...@vger.kernel.org
Signed-off-by: Stefan Windfeldt-Prytz <stefan.windfe...@axis.com>
Signed-off-by: Jonathan Cameron <jonathan.came...@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gre...@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
@@ -175,7 +175,7 @@ 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);