[PATCH 5.10.y] iio: light: isl29028: fix runtime PM reference leak on error paths

[Sasha Levin <sashal@kernel.org>]

From: Fabio Cesari <fabio.cesari@gmail.com>

[ Upstream commit 0e30d15b15647df786e60022650613e16dd70645 ]

isl29028_read_raw() and isl29028_write_raw() take a runtime PM reference
with pm_runtime_resume_and_get() but return directly on their error
paths without dropping it. The usage count never balances again and the
device stops entering autosuspend for good. In isl29028_read_raw() this
needs a regmap access to fail; in isl29028_write_raw() one rejected
sysfs write is enough, for example

  echo 200 > in_proximity_sampling_frequency

which is outside the [1:100] range and returns -EINVAL with the
reference still held.

Take the reference with PM_RUNTIME_ACQUIRE_AUTOSUSPEND() instead, so it
is released on every return path.

This also stops the return value of pm_runtime_put_autosuspend() from
reaching userspace. That value only says whether the device could be
suspended right away, so -EAGAIN or -EPERM turns a successful access
into a failure, and with CONFIG_PM=n the stub returns -ENOSYS on every
access.

Fixes: 2db5054ac28d ("staging: iio: isl29028: add runtime power management support")
Suggested-by: Joshua Crofts <joshua.crofts1@gmail.com>
Cc: stable@vger.kernel.org
Assisted-by: LLM coccinelle
Signed-off-by: Fabio Cesari <fabio.cesari@gmail.com>
Reviewed-by: Joshua Crofts <joshua.crofts1@gmail.com>
Signed-off-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
[ sashal: used explicit isl29028_set_pm_runtime_busy() calls instead of scoped runtime PM guards ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/iio/light/isl29028.c | 23 ++++-------------------
 1 file changed, 4 insertions(+), 19 deletions(-)

diff --git a/drivers/iio/light/isl29028.c b/drivers/iio/light/isl29028.c
index 15cf67b5e8549..8aa84e06eb51e 100644
--- a/drivers/iio/light/isl29028.c
+++ b/drivers/iio/light/isl29028.c
@@ -409,14 +409,9 @@ static int isl29028_write_raw(struct iio_dev *indio_dev,
 
 	mutex_unlock(&chip->lock);
 
-	if (ret < 0)
-		return ret;
+	isl29028_set_pm_runtime_busy(chip, false);
 
-	ret = isl29028_set_pm_runtime_busy(chip, false);
-	if (ret < 0)
-		return ret;
-
-	return 0;
+	return ret;
 }
 
 static int isl29028_read_raw(struct iio_dev *indio_dev,
@@ -425,7 +420,7 @@ static int isl29028_read_raw(struct iio_dev *indio_dev,
 {
 	struct isl29028_chip *chip = iio_priv(indio_dev);
 	struct device *dev = regmap_get_device(chip->regmap);
-	int ret, pm_ret;
+	int ret;
 
 	ret = isl29028_set_pm_runtime_busy(chip, true);
 	if (ret < 0)
@@ -478,17 +473,7 @@ static int isl29028_read_raw(struct iio_dev *indio_dev,
 
 	mutex_unlock(&chip->lock);
 
-	if (ret < 0)
-		return ret;
-
-	/**
-	 * Preserve the ret variable if the call to
-	 * isl29028_set_pm_runtime_busy() is successful so the reading
-	 * (if applicable) is returned to user space.
-	 */
-	pm_ret = isl29028_set_pm_runtime_busy(chip, false);
-	if (pm_ret < 0)
-		return pm_ret;
+	isl29028_set_pm_runtime_busy(chip, false);
 
 	return ret;
 }
-- 
2.53.0