linux-kernel - [PATCH 4.11 66/78] staging: iio: ad7152: Fix deadlock in ad7152_write_raw_samp

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Message-Id: <20170619151031.896576301@linuxfoundation.org>
Date:   Mon, 19 Jun 2017 23:16:06 +0800
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Alexey Khoroshilov <khoroshilov@...ras.ru>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Jonathan Cameron <jic23@...nel.org>
Subject: [PATCH 4.11 66/78] staging: iio: ad7152: Fix deadlock in ad7152_write_raw_samp_freq()

4.11-stable review patch.  If anyone has any objections, please let me know.

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

From: Alexey Khoroshilov <khoroshilov@...ras.ru>

commit 95264c8c6a9040e84edda883dbbe9d193c41f46c upstream.

ad7152_write_raw_samp_freq() is called by ad7152_write_raw() with
chip->state_lock held. So, there is unavoidable deadlock when
ad7152_write_raw_samp_freq() locks the mutex itself.

The patch removes unneeded locking.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@...ras.ru>
Fixes: 6572389bcc11 ("staging: iio: cdc: ad7152: Implement IIO_CHAN_INFO_SAMP_FREQ attribute")
Acked-by: Lars-Peter Clausen <lars@...afoo.de>
Signed-off-by: Jonathan Cameron <jic23@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/staging/iio/cdc/ad7152.c |    6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

--- a/drivers/staging/iio/cdc/ad7152.c
+++ b/drivers/staging/iio/cdc/ad7152.c
@@ -231,16 +231,12 @@ static int ad7152_write_raw_samp_freq(st
 	if (i >= ARRAY_SIZE(ad7152_filter_rate_table))
 		i = ARRAY_SIZE(ad7152_filter_rate_table) - 1;
 
-	mutex_lock(&chip->state_lock);
 	ret = i2c_smbus_write_byte_data(chip->client,
 					AD7152_REG_CFG2, AD7152_CFG2_OSR(i));
-	if (ret < 0) {
-		mutex_unlock(&chip->state_lock);
+	if (ret < 0)
 		return ret;
-	}
 
 	chip->filter_rate_setup = i;
-	mutex_unlock(&chip->state_lock);
 
 	return ret;
 }