[PATCH v2] iio: adc: ad7923: Fix buffer overflow for tx_buf and ring_xfer

[Zicheng Qu]

The AD7923 was updated to support devices with 8 channels, but the size
of tx_buf and ring_xfer was not increased accordingly, leading to a
potential buffer overflow in ad7923_update_scan_mode().

Fixes: 851644a60d20 ("iio: adc: ad7923: Add support for the ad7908/ad7918/ad7928")
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Nuno Sá <noname.nuno@xxxxxxxxx>
Signed-off-by: Zicheng Qu <quzicheng@xxxxxxxxxx>
---
v2:
- Fixed: Addressed buffer overflow in ad7923_update_scan_mode() due to 
insufficient tx_buf and ring_xfer size for 8-channel devices.
- Issue: Original patch attempted to fix the overflow by limiting the 
length, but did not address the root cause of buffer size mismatch.
- Solution: Increased tx_buf and ring_xfer sizes recommended by Nuno to 
support all 8 channels, ensuring adequate buffer capacity.
- Previous patch link: 
https://lore.kernel.org/linux-iio/20241028142357.1032380-1-quzicheng@xxxxxxxxxx/T/#u
 drivers/iio/adc/ad7923.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/adc/ad7923.c b/drivers/iio/adc/ad7923.c
index 09680015a7ab..acc44cb34f82 100644
--- a/drivers/iio/adc/ad7923.c
+++ b/drivers/iio/adc/ad7923.c
@@ -48,7 +48,7 @@
 
 struct ad7923_state {
 	struct spi_device		*spi;
-	struct spi_transfer		ring_xfer[5];
+	struct spi_transfer		ring_xfer[9];
 	struct spi_transfer		scan_single_xfer[2];
 	struct spi_message		ring_msg;
 	struct spi_message		scan_single_msg;
@@ -64,7 +64,7 @@ struct ad7923_state {
 	 * Length = 8 channels + 4 extra for 8 byte timestamp
 	 */
 	__be16				rx_buf[12] __aligned(IIO_DMA_MINALIGN);
-	__be16				tx_buf[4];
+	__be16				tx_buf[8];
 };
 
 struct ad7923_chip_info {
-- 
2.34.1