linux-kernel - [PATCH 3.2 055/126] staging: iio: ad5933: avoid uninitialized variable in error case

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Message-ID: <lsq.1487198494.212211327@decadent.org.uk>
Date:   Wed, 15 Feb 2017 22:41:34 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Jonathan Cameron" <jic23@...nel.org>,
        "Lars-Peter Clausen" <lars@...afoo.de>,
        "Arnd Bergmann" <arnd@...db.de>
Subject: [PATCH 3.2 055/126] staging: iio: ad5933: avoid uninitialized
 variable in error case

3.2.85-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Arnd Bergmann <arnd@...db.de>

commit 34eee70a7b82b09dbda4cb453e0e21d460dae226 upstream.

The ad5933_i2c_read function returns an error code to indicate
whether it could read data or not. However ad5933_work() ignores
this return code and just accesses the data unconditionally,
which gets detected by gcc as a possible bug:

drivers/staging/iio/impedance-analyzer/ad5933.c: In function 'ad5933_work':
drivers/staging/iio/impedance-analyzer/ad5933.c:649:16: warning: 'status' may be used uninitialized in this function [-Wmaybe-uninitialized]

This adds minimal error handling so we only evaluate the
data if it was correctly read.

Link: https://patchwork.kernel.org/patch/8110281/
Signed-off-by: Arnd Bergmann <arnd@...db.de>
Acked-by: Lars-Peter Clausen <lars@...afoo.de>
Signed-off-by: Jonathan Cameron <jic23@...nel.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/staging/iio/impedance-analyzer/ad5933.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

--- a/drivers/staging/iio/impedance-analyzer/ad5933.c
+++ b/drivers/staging/iio/impedance-analyzer/ad5933.c
@@ -626,6 +626,7 @@ static void ad5933_work(struct work_stru
 	struct iio_buffer *ring = indio_dev->buffer;
 	signed short buf[2];
 	unsigned char status;
+	int ret;
 
 	mutex_lock(&indio_dev->mlock);
 	if (st->state == AD5933_CTRL_INIT_START_FREQ) {
@@ -633,17 +634,20 @@ static void ad5933_work(struct work_stru
 		ad5933_cmd(st, AD5933_CTRL_START_SWEEP);
 		st->state = AD5933_CTRL_START_SWEEP;
 		schedule_delayed_work(&st->work, st->poll_time_jiffies);
-		mutex_unlock(&indio_dev->mlock);
-		return;
+		goto out;
 	}
 
-	ad5933_i2c_read(st->client, AD5933_REG_STATUS, 1, &status);
+	ret = ad5933_i2c_read(st->client, AD5933_REG_STATUS, 1, &status);
+	if (ret)
+		goto out;
 
 	if (status & AD5933_STAT_DATA_VALID) {
-		ad5933_i2c_read(st->client,
+		ret = ad5933_i2c_read(st->client,
 				test_bit(1, ring->scan_mask) ?
 				AD5933_REG_REAL_DATA : AD5933_REG_IMAG_DATA,
 				ring->scan_count * 2, (u8 *)buf);
+		if (ret)
+			goto out;
 
 		if (ring->scan_count == 2) {
 			buf[0] = be16_to_cpu(buf[0]);
@@ -656,8 +660,7 @@ static void ad5933_work(struct work_stru
 	} else {
 		/* no data available - try again later */
 		schedule_delayed_work(&st->work, st->poll_time_jiffies);
-		mutex_unlock(&indio_dev->mlock);
-		return;
+		goto out;
 	}
 
 	if (status & AD5933_STAT_SWEEP_DONE) {
@@ -669,7 +672,7 @@ static void ad5933_work(struct work_stru
 		ad5933_cmd(st, AD5933_CTRL_INC_FREQ);
 		schedule_delayed_work(&st->work, st->poll_time_jiffies);
 	}
-
+out:
 	mutex_unlock(&indio_dev->mlock);
 }