Patch "iio: adc: at91-sama5d2_adc: lock around oversampling and sample freq" has been added to the 5.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    iio: adc: at91-sama5d2_adc: lock around oversampling and sample freq

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     iio-adc-at91-sama5d2_adc-lock-around-oversampling-an.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit dca9f98686fe7c738c909ba792f47feb8c559597
Author: Claudiu Beznea <claudiu.beznea@xxxxxxxxxxxxx>
Date:   Wed Aug 3 13:28:39 2022 +0300

    iio: adc: at91-sama5d2_adc: lock around oversampling and sample freq
    
    [ Upstream commit 9780a23ed5a0a0a63683e078f576719a98d4fb70 ]
    
    .read_raw()/.write_raw() could be called asynchronously from user space
    or other in kernel drivers. Without locking on st->lock these could be
    called asynchronously while there is a conversion in progress. Read will
    be harmless but changing registers while conversion is in progress may
    lead to inconsistent results. Thus, to avoid this lock st->lock.
    
    Fixes: 27e177190891 ("iio:adc:at91_adc8xx: introduce new atmel adc driver")
    Fixes: 6794e23fa3fe ("iio: adc: at91-sama5d2_adc: add support for oversampling resolution")
    Signed-off-by: Claudiu Beznea <claudiu.beznea@xxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20220803102855.2191070-4-claudiu.beznea@xxxxxxxxxxxxx
    Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/iio/adc/at91-sama5d2_adc.c b/drivers/iio/adc/at91-sama5d2_adc.c
index fe41689c5da6..ef6dc85024c1 100644
--- a/drivers/iio/adc/at91-sama5d2_adc.c
+++ b/drivers/iio/adc/at91-sama5d2_adc.c
@@ -1353,10 +1353,10 @@ static int at91_adc_read_info_raw(struct iio_dev *indio_dev,
 		ret = at91_adc_read_position(st, chan->channel,
 					     &tmp_val);
 		*val = tmp_val;
-		mutex_unlock(&st->lock);
-		iio_device_release_direct_mode(indio_dev);
 		if (ret > 0)
 			ret = at91_adc_adjust_val_osr(st, val);
+		mutex_unlock(&st->lock);
+		iio_device_release_direct_mode(indio_dev);
 
 		return ret;
 	}
@@ -1369,10 +1369,10 @@ static int at91_adc_read_info_raw(struct iio_dev *indio_dev,
 		ret = at91_adc_read_pressure(st, chan->channel,
 					     &tmp_val);
 		*val = tmp_val;
-		mutex_unlock(&st->lock);
-		iio_device_release_direct_mode(indio_dev);
 		if (ret > 0)
 			ret = at91_adc_adjust_val_osr(st, val);
+		mutex_unlock(&st->lock);
+		iio_device_release_direct_mode(indio_dev);
 
 		return ret;
 	}
@@ -1465,16 +1465,20 @@ static int at91_adc_write_raw(struct iio_dev *indio_dev,
 		/* if no change, optimize out */
 		if (val == st->oversampling_ratio)
 			return 0;
+		mutex_lock(&st->lock);
 		st->oversampling_ratio = val;
 		/* update ratio */
 		at91_adc_config_emr(st);
+		mutex_unlock(&st->lock);
 		return 0;
 	case IIO_CHAN_INFO_SAMP_FREQ:
 		if (val < st->soc_info.min_sample_rate ||
 		    val > st->soc_info.max_sample_rate)
 			return -EINVAL;
 
+		mutex_lock(&st->lock);
 		at91_adc_setup_samp_freq(indio_dev, val);
+		mutex_unlock(&st->lock);
 		return 0;
 	default:
 		return -EINVAL;