staging:iio:dummy: Fix potential NULL pointer dereferenceiio-for-v3.7e

If the config contains CONFIG_IIO_BUFFER=y and CONFIG_IIO_SIMPLE_DUMMY_BUFFER=n
iio_simple_dummy_configure_buffer() is stubbed out and iio_buffer_register() is
not. As a result we try to register a buffer which has not been configured.
This will causes a NULL pointer deref in iio_buffer_register. To solve this
issue move the iio_buffer_register() call to iio_simple_dummy_configure_buffer(),
so it will only be called if iio_simple_dummy_configure_buffer() has been called.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

1 files changed, 7 insertions, 13 deletions

diff --git a/drivers/staging/iio/iio_simple_dummy.c b/drivers/staging/iio/iio_simple_dummy.c
index 029bcc67f164..dc6c728ea47a 100644
--- a/drivers/staging/iio/iio_simple_dummy.c
+++ b/drivers/staging/iio/iio_simple_dummy.c
@@ -445,26 +445,20 @@ static int __devinit iio_dummy_probe(int index)
 	if (ret < 0)
 		goto error_free_device;
 
-	/* Configure buffered capture support. */
-	ret = iio_simple_dummy_configure_buffer(indio_dev);
-	if (ret < 0)
-		goto error_unregister_events;
-
 	/*
-	 * Register the channels with the buffer, but avoid the output
-	 * channel being registered by reducing the number of channels by 1.
+	 * Configure buffered capture support and register the channels with the
+	 * buffer, but avoid the output channel being registered by reducing the
+	 * number of channels by 1.
 	 */
-	ret = iio_buffer_register(indio_dev, iio_dummy_channels, 5);
+	ret = iio_simple_dummy_configure_buffer(indio_dev, iio_dummy_channels, 5);
 	if (ret < 0)
-		goto error_unconfigure_buffer;
+		goto error_unregister_events;
 
 	ret = iio_device_register(indio_dev);
 	if (ret < 0)
-		goto error_unregister_buffer;
+		goto error_unconfigure_buffer;
 
 	return 0;
-error_unregister_buffer:
-	iio_buffer_unregister(indio_dev);
 error_unconfigure_buffer:
 	iio_simple_dummy_unconfigure_buffer(indio_dev);
 error_unregister_events:
@@ -499,7 +493,6 @@ static int iio_dummy_remove(int index)
 	/* Device specific code to power down etc */
 
 	/* Buffered capture related cleanup */
-	iio_buffer_unregister(indio_dev);
 	iio_simple_dummy_unconfigure_buffer(indio_dev);
 
 	ret = iio_simple_dummy_events_unregister(indio_dev);
@@ -530,6 +523,7 @@ static __init int iio_dummy_init(void)
 		instances = 1;
 		return -EINVAL;
 	}
+
 	/* Fake a bus */
 	iio_dummy_devs = kcalloc(instances, sizeof(*iio_dummy_devs),
 				 GFP_KERNEL);