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Commit 7251b291 authored by William Breathitt Gray's avatar William Breathitt Gray Committed by Greg Kroah-Hartman
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iio: addac: stx104: Fix race condition for stx104_write_raw() 



[ Upstream commit 9740827468cea80c42db29e7171a50e99acf7328 ]

The priv->chan_out_states array and actual DAC value can become
mismatched if stx104_write_raw() is called concurrently. Prevent such a
race condition by utilizing a mutex.

Fixes: 97a445da ("iio: Add IIO support for the DAC on the Apex Embedded Systems STX104")
Signed-off-by: default avatarWilliam Breathitt Gray <william.gray@linaro.org>
Link: https://lore.kernel.org/r/c95c9a77fcef36b2a052282146950f23bbc1ebdc.1680790580.git.william.gray@linaro.org


Cc: <Stable@vger.kernel.org>
Signed-off-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
Stable-dep-of: 4f9b80aefb9e ("iio: addac: stx104: Fix race condition when converting analog-to-digital")
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 70d135e7

drivers/iio/addac/stx104.c

+8 −0
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ 
#include <linux/kernel.h>

#include <linux/module.h>

#include <linux/moduleparam.h>

#include <linux/mutex.h>

#include <linux/spinlock.h>

#include <linux/types.h>
@@ -69,10 +70,12 @@ struct stx104_reg { 


/**

 * struct stx104_iio - IIO device private data structure

 * @lock: synchronization lock to prevent I/O race conditions

 * @chan_out_states:	channels' output states

 * @reg:		I/O address offset for the device registers

 */

struct stx104_iio {

	struct mutex lock;

	unsigned int chan_out_states[STX104_NUM_OUT_CHAN];

	struct stx104_reg __iomem *reg;

};
@@ -178,9 +181,12 @@ static int stx104_write_raw(struct iio_dev *indio_dev, 
			if ((unsigned int)val > 65535)

				return -EINVAL;



			mutex_lock(&priv->lock);



			priv->chan_out_states[chan->channel] = val;

			iowrite16(val, &priv->reg->dac[chan->channel]);



			mutex_unlock(&priv->lock);

			return 0;

		}

		return -EINVAL;
@@ -352,6 +358,8 @@ static int stx104_probe(struct device *dev, unsigned int id) 
	indio_dev->name = dev_name(dev);

	indio_dev->dev.parent = dev;



	mutex_init(&priv->lock);



	/* configure device for software trigger operation */

	iowrite8(0, &priv->reg->acr);