[PATCH v2 03/19] iio: chemical: bme680: Fix overflows in compensate() functions

[Vasileios Amoiridis]

There are cases in the compensate functions of the driver that
there could be overflows of variables due to bit shifting ops.
These implications were initially discussed here [1] and they
were mentioned in log message of Commit 1b3bd8592780 ("iio:
chemical: Add support for Bosch BME680 sensor").

[1]: https://lore.kernel.org/linux-iio/20180728114028.3c1bbe81@archlinux/
Fixes: 1b3bd8592780 ("iio: chemical: Add support for Bosch BME680 sensor")
Signed-off-by: Vasileios Amoiridis <vassilisamir@xxxxxxxxx>
---
 drivers/iio/chemical/bme680_core.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/iio/chemical/bme680_core.c b/drivers/iio/chemical/bme680_core.c
index 812829841733..5db48f6d646c 100644
--- a/drivers/iio/chemical/bme680_core.c
+++ b/drivers/iio/chemical/bme680_core.c
@@ -342,10 +342,10 @@ static s16 bme680_compensate_temp(struct bme680_data *data,
 	if (!calib->par_t2)
 		bme680_read_calib(data, calib);
 
-	var1 = (adc_temp >> 3) - (calib->par_t1 << 1);
+	var1 = (adc_temp >> 3) - ((s32)calib->par_t1 << 1);
 	var2 = (var1 * calib->par_t2) >> 11;
 	var3 = ((var1 >> 1) * (var1 >> 1)) >> 12;
-	var3 = (var3 * (calib->par_t3 << 4)) >> 14;
+	var3 = (var3 * ((s32)calib->par_t3 << 4)) >> 14;
 	data->t_fine = var2 + var3;
 	calc_temp = (data->t_fine * 5 + 128) >> 8;
 
@@ -368,9 +368,9 @@ static u32 bme680_compensate_press(struct bme680_data *data,
 	var1 = (data->t_fine >> 1) - 64000;
 	var2 = ((((var1 >> 2) * (var1 >> 2)) >> 11) * calib->par_p6) >> 2;
 	var2 = var2 + (var1 * calib->par_p5 << 1);
-	var2 = (var2 >> 2) + (calib->par_p4 << 16);
+	var2 = (var2 >> 2) + ((s32)calib->par_p4 << 16);
 	var1 = (((((var1 >> 2) * (var1 >> 2)) >> 13) *
-			(calib->par_p3 << 5)) >> 3) +
+			((s32)calib->par_p3 << 5)) >> 3) +
 			((calib->par_p2 * var1) >> 1);
 	var1 = var1 >> 18;
 	var1 = ((32768 + var1) * calib->par_p1) >> 15;
@@ -388,7 +388,7 @@ static u32 bme680_compensate_press(struct bme680_data *data,
 	var3 = ((press_comp >> 8) * (press_comp >> 8) *
 			(press_comp >> 8) * calib->par_p10) >> 17;
 
-	press_comp += (var1 + var2 + var3 + (calib->par_p7 << 7)) >> 4;
+	press_comp += (var1 + var2 + var3 + ((s32)calib->par_p7 << 7)) >> 4;
 
 	return press_comp;
 }
@@ -414,7 +414,7 @@ static u32 bme680_compensate_humid(struct bme680_data *data,
 		 (((temp_scaled * ((temp_scaled * calib->par_h5) / 100))
 		   >> 6) / 100) + (1 << 14))) >> 10;
 	var3 = var1 * var2;
-	var4 = calib->par_h6 << 7;
+	var4 = (s32)calib->par_h6 << 7;
 	var4 = (var4 + ((temp_scaled * calib->par_h7) / 100)) >> 4;
 	var5 = ((var3 >> 14) * (var3 >> 14)) >> 10;
 	var6 = (var4 * var5) >> 1;
-- 
2.25.1