[PATCH 5/9] iio: adc: mcp3911: reject devices without match data

[Jiale Yao]

SPI driver_override allows a device to bind to this driver without
matching either the OF or SPI device ID table. In that case,
spi_get_device_match_data() returns NULL.

mcp3911_probe() stores the result and later calls through chip->config
and accesses other chip-specific fields, causing a NULL pointer
dereference.

Commit 572a00852635 ("iio: dac: ad5686: missing NULL check on match
data") fixed the same driver_override issue in another SPI driver.
Reject devices without match data before continuing the probe.

Fixes: 732ad34260d3 ("iio: adc: mcp3911: add support for the whole MCP39xx family")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Jiale Yao <yaojiale02@xxxxxxx>
---
 drivers/iio/adc/mcp3911.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/iio/adc/mcp3911.c b/drivers/iio/adc/mcp3911.c
index 797424f59f74..90167930f913 100644
--- a/drivers/iio/adc/mcp3911.c
+++ b/drivers/iio/adc/mcp3911.c
@@ -721,6 +721,8 @@ static int mcp3911_probe(struct spi_device *spi)
 	adc = iio_priv(indio_dev);
 	adc->spi = spi;
 	adc->chip = spi_get_device_match_data(spi);
+	if (!adc->chip)
+		return -ENODATA;
 
 	ret = devm_regulator_get_enable_read_voltage(dev, "vref");
 	if (ret < 0 && ret != -ENODEV)
-- 
2.34.1