linux-kernel - [PATCH v1 03/17] iio: chemical: bme680: Fix overflows in compensate() functions

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Message-Id: <20240527183805.311501-4-vassilisamir@gmail.com>
Date: Mon, 27 May 2024 20:37:51 +0200
From: Vasileios Amoiridis <vassilisamir@...il.com>
To: jic23@...nel.org,
	lars@...afoo.de
Cc: himanshujha199640@...il.com,
	linux-iio@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Vasileios Amoiridis <vassilisamir@...il.com>
Subject: [PATCH v1 03/17] iio: chemical: bme680: Fix overflows in compensate() functions

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@...il.com>
---
 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