linux-kernel - [PATCH v3] iio: vadc: Fix potential dereference of NULL pointer

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Date:   Fri, 20 May 2022 20:35:35 -0700
From:   Yongzhi Liu <lyz_cs@....edu.cn>
To:     agross@...nel.org, bjorn.andersson@...aro.org, jic23@...nel.org,
        lars@...afoo.de, svarbanov@...sol.com, iivanov@...sol.com,
        jonathan.cameron@...wei.com
Cc:     linux-arm-msm@...r.kernel.org, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org, fuyq@....pku.edu.cn,
        Yongzhi Liu <lyz_cs@....edu.cn>
Subject: [PATCH v3] iio: vadc: Fix potential dereference of NULL pointer

The return value of vadc_get_channel() needs to be checked to
avoid use of NULL pointer. Fix this by adding the null pointer
check on prop and dropping general error prints.

Fixes: 0917de94c02f ("iio: vadc: Qualcomm SPMI PMIC voltage ADC driver")
Signed-off-by: Yongzhi Liu <lyz_cs@....edu.cn>
---
 drivers/iio/adc/qcom-spmi-vadc.c | 38 ++++++++++++++++++++++++++++----------
 1 file changed, 28 insertions(+), 10 deletions(-)

diff --git a/drivers/iio/adc/qcom-spmi-vadc.c b/drivers/iio/adc/qcom-spmi-vadc.c
index 34202ba..43a52b1 100644
--- a/drivers/iio/adc/qcom-spmi-vadc.c
+++ b/drivers/iio/adc/qcom-spmi-vadc.c
@@ -358,22 +358,33 @@ static int vadc_measure_ref_points(struct vadc_priv *vadc)
 	vadc->graph[VADC_CALIB_ABSOLUTE].dx = VADC_ABSOLUTE_RANGE_UV;
 
 	prop = vadc_get_channel(vadc, VADC_REF_1250MV);
+	if (!prop) {
+		dev_err(vadc->dev, "Please define 1.25V channel\n");
+		ret = -ENODEV;
+		return ret;
+	}
 	ret = vadc_do_conversion(vadc, prop, &read_1);
 	if (ret)
-		goto err;
+		return ret;
 
 	/* Try with buffered 625mV channel first */
 	prop = vadc_get_channel(vadc, VADC_SPARE1);
-	if (!prop)
+	if (!prop) {
 		prop = vadc_get_channel(vadc, VADC_REF_625MV);
+		if (!prop) {
+			dev_err(vadc->dev, "Please define 0.625V channel\n");
+			ret = -ENODEV;
+			return ret;
+		}
+	}
 
 	ret = vadc_do_conversion(vadc, prop, &read_2);
 	if (ret)
-		goto err;
+		return ret;
 
 	if (read_1 == read_2) {
 		ret = -EINVAL;
-		goto err;
+		return ret;
 	}
 
 	vadc->graph[VADC_CALIB_ABSOLUTE].dy = read_1 - read_2;
@@ -381,25 +392,32 @@ static int vadc_measure_ref_points(struct vadc_priv *vadc)
 
 	/* Ratiometric calibration */
 	prop = vadc_get_channel(vadc, VADC_VDD_VADC);
+	if (!prop) {
+		dev_err(vadc->dev, "Please define VDD channel\n");
+		ret = -ENODEV;
+		return ret;
+	}
 	ret = vadc_do_conversion(vadc, prop, &read_1);
 	if (ret)
-		goto err;
+		return ret;
 
 	prop = vadc_get_channel(vadc, VADC_GND_REF);
+	if (!prop) {
+		dev_err(vadc->dev, "Please define GND channel\n");
+		ret = -ENODEV;
+		return ret;
+	}
 	ret = vadc_do_conversion(vadc, prop, &read_2);
 	if (ret)
-		goto err;
+		return ret;
 
 	if (read_1 == read_2) {
 		ret = -EINVAL;
-		goto err;
+		return ret;
 	}
 
 	vadc->graph[VADC_CALIB_RATIOMETRIC].dy = read_1 - read_2;
 	vadc->graph[VADC_CALIB_RATIOMETRIC].gnd = read_2;
-err:
-	if (ret)
-		dev_err(vadc->dev, "measure reference points failed\n");
 
 	return ret;
 }
-- 
2.7.4