[PATCH 2/3] iio: adc: ad7124: Fix potential overflow due to non sequential channel numbers

[Jonathan Cameron <jic23@kernel.org>]

From: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Channel numbering must start at 0 and then not have any holes, or
it is possible to overflow the available storage.  Note this bug was
introduced as part of a fix to ensure we didn't rely on the ordering
of child nodes.  So we need to support arbitrary ordering but they all
need to be there somewhere.

Note I hit this when using qemu to test the rest of this series.
Arguably this isn't the best fix, but it is probably the most minimal
option for backporting etc.

Fixes: d7857e4ee1ba6 ("iio: adc: ad7124: Fix DT channel configuration")
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
 drivers/iio/adc/ad7124.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/iio/adc/ad7124.c b/drivers/iio/adc/ad7124.c
index c0d0870a29ff..9c2401c5848e 100644
--- a/drivers/iio/adc/ad7124.c
+++ b/drivers/iio/adc/ad7124.c
@@ -616,6 +616,13 @@ static int ad7124_of_parse_channel_config(struct iio_dev *indio_dev,
 		if (ret)
 			goto err;
 
+		if (channel >= indio_dev->num_channels) {
+			dev_err(indio_dev->dev.parent,
+				"Channel index >= number of channels\n");
+			ret = -EINVAL;
+			goto err;
+		}
+
 		ret = of_property_read_u32_array(child, "diff-channels",
 						 ain, 2);
 		if (ret)
-- 
2.31.1