The patch below does not apply to the 4.17-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From ca4c8fc97e669d7464a95e006d0ca4eadfa4e4bc Mon Sep 17 00:00:00 2001

From: Jean-Baptiste Maneyrol jmaneyrol@invensense.com Date: Mon, 30 Apr 2018 12:14:09 +0200 Subject: [PATCH] iio: imu: inv_mpu6050: fix possible deadlock between mutex and iio

Detected by kernel circular locking dependency checker.

We are locking iio mutex (iio_device_claim_direct_mode) after locking our internal mutex. But when the buffer starts, iio first locks its mutex and then we lock our internal one.

To avoid possible deadlock, we need to use the same order everwhere. So we change the ordering by locking first iio mutex, then our internal mutex.

Fixes: 68cd6e5b206b ("iio: imu: inv_mpu6050: fix lock issues by using our own mutex") Cc: stable@vger.kernel.org Signed-off-by: Jean-Baptiste Maneyrol jmaneyrol@invensense.com Signed-off-by: Jonathan Cameron Jonathan.Cameron@huawei.com

diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c index aafa77766b08..7358935fb391 100644 --- a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c +++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c @@ -340,12 +340,9 @@ static int inv_mpu6050_read_channel_data(struct iio_dev *indio_dev, int result; int ret;

- result = iio_device_claim_direct_mode(indio_dev); - if (result) - return result; result = inv_mpu6050_set_power_itg(st, true); if (result) - goto error_release; + return result;

switch (chan->type) { case IIO_ANGL_VEL: @@ -386,14 +383,11 @@ static int inv_mpu6050_read_channel_data(struct iio_dev *indio_dev, result = inv_mpu6050_set_power_itg(st, false); if (result) goto error_power_off; - iio_device_release_direct_mode(indio_dev);

return ret;

error_power_off: inv_mpu6050_set_power_itg(st, false); -error_release: - iio_device_release_direct_mode(indio_dev); return result; }

@@ -407,9 +401,13 @@ inv_mpu6050_read_raw(struct iio_dev *indio_dev,

switch (mask) { case IIO_CHAN_INFO_RAW: + ret = iio_device_claim_direct_mode(indio_dev); + if (ret) + return ret; mutex_lock(&st->lock); ret = inv_mpu6050_read_channel_data(indio_dev, chan, val); mutex_unlock(&st->lock); + iio_device_release_direct_mode(indio_dev); return ret; case IIO_CHAN_INFO_SCALE: switch (chan->type) { @@ -532,17 +530,18 @@ static int inv_mpu6050_write_raw(struct iio_dev *indio_dev, struct inv_mpu6050_state *st = iio_priv(indio_dev); int result;

- mutex_lock(&st->lock); /* * we should only update scale when the chip is disabled, i.e. * not running */ result = iio_device_claim_direct_mode(indio_dev); if (result) - goto error_write_raw_unlock; + return result; + + mutex_lock(&st->lock); result = inv_mpu6050_set_power_itg(st, true); if (result) - goto error_write_raw_release; + goto error_write_raw_unlock;

switch (mask) { case IIO_CHAN_INFO_SCALE: @@ -581,10 +580,9 @@ static int inv_mpu6050_write_raw(struct iio_dev *indio_dev, }

result |= inv_mpu6050_set_power_itg(st, false); -error_write_raw_release: - iio_device_release_direct_mode(indio_dev); error_write_raw_unlock: mutex_unlock(&st->lock); + iio_device_release_direct_mode(indio_dev);

return result; } @@ -643,17 +641,18 @@ inv_mpu6050_fifo_rate_store(struct device *dev, struct device_attribute *attr, fifo_rate > INV_MPU6050_MAX_FIFO_RATE) return -EINVAL;

+ result = iio_device_claim_direct_mode(indio_dev); + if (result) + return result; + mutex_lock(&st->lock); if (fifo_rate == st->chip_config.fifo_rate) { result = 0; goto fifo_rate_fail_unlock; } - result = iio_device_claim_direct_mode(indio_dev); - if (result) - goto fifo_rate_fail_unlock; result = inv_mpu6050_set_power_itg(st, true); if (result) - goto fifo_rate_fail_release; + goto fifo_rate_fail_unlock;

d = INV_MPU6050_ONE_K_HZ / fifo_rate - 1; result = regmap_write(st->map, st->reg->sample_rate_div, d); @@ -667,10 +666,9 @@ inv_mpu6050_fifo_rate_store(struct device *dev, struct device_attribute *attr,

fifo_rate_fail_power_off: result |= inv_mpu6050_set_power_itg(st, false); -fifo_rate_fail_release: - iio_device_release_direct_mode(indio_dev); fifo_rate_fail_unlock: mutex_unlock(&st->lock); + iio_device_release_direct_mode(indio_dev); if (result) return result;