[PATCH] iio: adc: ad7768-1: Fix ERR_PTR dereference in ad7768_fill_scale_tbl

[Ethan Tidmore]

The function iio_get_current_scan_type() can return ERR_PTR, the return
value scan_type is not checked for this and immediately dereferenced
which can cause a kernel panic.

Add check for IS_ERR() and return early to avoid crash.

Fixes: ff085189cb17 ("iio: adc: ad7768-1: add support for ADAQ776x-1 ADC Family")
Signed-off-by: Ethan Tidmore <ethantidmore06@xxxxxxxxx>
---
 drivers/iio/adc/ad7768-1.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/iio/adc/ad7768-1.c b/drivers/iio/adc/ad7768-1.c
index fcd8aea7152e..f45a09e39367 100644
--- a/drivers/iio/adc/ad7768-1.c
+++ b/drivers/iio/adc/ad7768-1.c
@@ -541,6 +541,11 @@ static void ad7768_fill_scale_tbl(struct iio_dev *dev)
 	u64 tmp2;
 
 	scan_type = iio_get_current_scan_type(dev, &dev->channels[0]);
+	if (IS_ERR(scan_type)) {
+		dev_err(&st->spi->dev, "Failed to get scan type.\n");
+		return;
+	}
+
 	if (scan_type->sign == 's')
 		val2 = scan_type->realbits - 1;
 	else
-- 
2.53.0