iio: adc: ad7124: Fix potential overflow due to non sequential channel numbers

stable inclusion
from stable-5.10.42
commit f70122825076117787b91e7f219e21c09f11a5b9
bugzilla: 55093
CVE: NA

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

commit f2a772c5 upstream.

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.

Alexandru's sign-off is here because he carried this patch in a larger
set that Jonathan then applied.

Fixes: d7857e4e ("iio: adc: ad7124: Fix DT channel configuration")
Reviewed-by: NAlexandru Ardelean <ardeleanalex@gmail.com>
Signed-off-by: NJonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: NAlexandru Ardelean <aardelean@deviqon.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

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)