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From:   Yizhuo <yzhai003@ucr.edu>
Cc:     csong@cs.ucr.edu, zhiyunq@cs.ucr.edu, Yizhuo <yzhai003@ucr.edu>,
        Jonathan Cameron <jic23@kernel.org>,
        Hartmut Knaack <knaack.h@gmx.de>,
        Lars-Peter Clausen <lars@metafoo.de>,
        Peter Meerwald-Stadler <pmeerw@pmeerw.net>,
        Kevin Hilman <khilman@baylibre.com>,
        Martin Blumenstingl <martin.blumenstingl@googlemail.com>,
        Neil Armstrong <narmstrong@baylibre.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Nicholas Mc Guire <hofrat@osadl.org>,
        linux-iio@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-amlogic@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: [PATCH] iio: adc: meson-saradc: Variables could be uninitalized if regmap_read() fails
Date:   Sun, 29 Sep 2019 09:48:43 -0700
Message-Id: <20190929164848.13930-1-yzhai003@ucr.edu>
To:     unlisted-recipients:; (no To-header on input)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Several functions in this file are trying to use regmap_read() to
initialize the specific variable, however, if regmap_read() fails,
the variable could be uninitialized but used directly, which is
potentially unsafe. The return value of regmap_read() should be
checked and handled.

Signed-off-by: Yizhuo <yzhai003@ucr.edu>
---
 drivers/iio/adc/meson_saradc.c | 30 ++++++++++++++++++++++++------
 1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/drivers/iio/adc/meson_saradc.c b/drivers/iio/adc/meson_saradc.c
index 7b28d045d271..4b6c2983ef39 100644
--- a/drivers/iio/adc/meson_saradc.c
+++ b/drivers/iio/adc/meson_saradc.c
@@ -323,6 +323,7 @@ static int meson_sar_adc_wait_busy_clear(struct iio_dev *indio_dev)
 {
 	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
 	int regval, timeout = 10000;
+	int ret;
 
 	/*
 	 * NOTE: we need a small delay before reading the status, otherwise
@@ -331,7 +332,9 @@ static int meson_sar_adc_wait_busy_clear(struct iio_dev *indio_dev)
 	 */
 	do {
 		udelay(1);
-		regmap_read(priv->regmap, MESON_SAR_ADC_REG0, &regval);
+		ret = regmap_read(priv->regmap, MESON_SAR_ADC_REG0, &regval);
+		if (ret)
+			return ret;
 	} while (FIELD_GET(MESON_SAR_ADC_REG0_BUSY_MASK, regval) && timeout--);
 
 	if (timeout < 0)
@@ -346,6 +349,7 @@ static int meson_sar_adc_read_raw_sample(struct iio_dev *indio_dev,
 {
 	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
 	int regval, fifo_chan, fifo_val, count;
+	int ret;
 
 	if(!wait_for_completion_timeout(&priv->done,
 				msecs_to_jiffies(MESON_SAR_ADC_TIMEOUT)))
@@ -358,7 +362,10 @@ static int meson_sar_adc_read_raw_sample(struct iio_dev *indio_dev,
 		return -EINVAL;
 	}
 
-	regmap_read(priv->regmap, MESON_SAR_ADC_FIFO_RD, &regval);
+	ret = regmap_read(priv->regmap, MESON_SAR_ADC_FIFO_RD, &regval);
+	if (ret)
+		return ret;
+
 	fifo_chan = FIELD_GET(MESON_SAR_ADC_FIFO_RD_CHAN_ID_MASK, regval);
 	if (fifo_chan != chan->address) {
 		dev_err(&indio_dev->dev,
@@ -491,6 +498,7 @@ static int meson_sar_adc_lock(struct iio_dev *indio_dev)
 {
 	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
 	int val, timeout = 10000;
+	int ret;
 
 	mutex_lock(&indio_dev->mlock);
 
@@ -506,7 +514,10 @@ static int meson_sar_adc_lock(struct iio_dev *indio_dev)
 		 */
 		do {
 			udelay(1);
-			regmap_read(priv->regmap, MESON_SAR_ADC_DELAY, &val);
+			ret = regmap_read(priv->regmap,
+						MESON_SAR_ADC_DELAY, &val);
+			if (ret)
+				return ret;
 		} while (val & MESON_SAR_ADC_DELAY_BL30_BUSY && timeout--);
 
 		if (timeout < 0) {
@@ -771,7 +782,7 @@ static int meson_sar_adc_init(struct iio_dev *indio_dev)
 {
 	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
 	int regval, i, ret;
-
+	int ret;
 	/*
 	 * make sure we start at CH7 input since the other muxes are only used
 	 * for internal calibration.
@@ -784,7 +795,10 @@ static int meson_sar_adc_init(struct iio_dev *indio_dev)
 		 * BL30 to make sure BL30 gets the values it expects when
 		 * reading the temperature sensor.
 		 */
-		regmap_read(priv->regmap, MESON_SAR_ADC_REG3, &regval);
+		ret = regmap_read(priv->regmap, MESON_SAR_ADC_REG3, &regval);
+		if (ret)
+			return ret;
+
 		if (regval & MESON_SAR_ADC_REG3_BL30_INITIALIZED)
 			return 0;
 	}
@@ -1013,8 +1027,12 @@ static irqreturn_t meson_sar_adc_irq(int irq, void *data)
 	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
 	unsigned int cnt, threshold;
 	u32 regval;
+	int ret;
+
+	ret = regmap_read(priv->regmap, MESON_SAR_ADC_REG0, &regval);
+	if (ret)
+		return ret;
 
-	regmap_read(priv->regmap, MESON_SAR_ADC_REG0, &regval);
 	cnt = FIELD_GET(MESON_SAR_ADC_REG0_FIFO_COUNT_MASK, regval);
 	threshold = FIELD_GET(MESON_SAR_ADC_REG0_FIFO_CNT_IRQ_MASK, regval);
 
-- 
2.17.1