linux-kernel - [PATCH v2] iio: vadc: Fix potential dereference of NULL pointer

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Message-Id: <1652939455-123139-1-git-send-email-lyz_cs@pku.edu.cn>
Date:   Wed, 18 May 2022 22:50:55 -0700
From:   Yongzhi Liu <lyz_cs@....edu.cn>
To:     agross@...nel.org, bjorn.andersson@...aro.org, jic23@...nel.org,
        lars@...afoo.de
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 v2] 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.

Fixes: 0917de94c ("iio: vadc: Qualcomm SPMI PMIC voltage ADC driver")

Signed-off-by: Yongzhi Liu <lyz_cs@....edu.cn>
---
 drivers/iio/adc/qcom-spmi-vadc.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/adc/qcom-spmi-vadc.c b/drivers/iio/adc/qcom-spmi-vadc.c
index 34202ba..9fa61fb 100644
--- a/drivers/iio/adc/qcom-spmi-vadc.c
+++ b/drivers/iio/adc/qcom-spmi-vadc.c
@@ -358,14 +358,25 @@ 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;
+		goto err;
+	}
 	ret = vadc_do_conversion(vadc, prop, &read_1);
 	if (ret)
 		goto err;
 
 	/* 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;
+			goto err;
+		}
+	}
 
 	ret = vadc_do_conversion(vadc, prop, &read_2);
 	if (ret)
@@ -381,11 +392,21 @@ 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;
+		goto err;
+	}
 	ret = vadc_do_conversion(vadc, prop, &read_1);
 	if (ret)
 		goto err;
 
 	prop = vadc_get_channel(vadc, VADC_GND_REF);
+	if (!prop) {
+		dev_err(vadc->dev, "Please define GND channel\n");
+		ret = -ENODEV;
+		goto err;
+	}
 	ret = vadc_do_conversion(vadc, prop, &read_2);
 	if (ret)
 		goto err;
-- 
2.7.4