linux-kernel - [PATCH 4/7] iio: as73211: copy/release available integration times to fix race

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Message-Id: <20241003-iio-read-avail-release-v1-4-c70cc7d9c2e0@gmail.com>
Date: Thu, 03 Oct 2024 19:34:09 +0200
From: Matteo Martelli <matteomartelli3@...il.com>
To: Jonathan Cameron <jic23@...nel.org>, 
 Lars-Peter Clausen <lars@...afoo.de>, 
 Michael Hennerich <Michael.Hennerich@...log.com>, 
 Alisa-Dariana Roman <alisa.roman@...log.com>, 
 Christian Eggers <ceggers@...i.de>, Peter Rosin <peda@...ntia.se>, 
 Paul Cercueil <paul@...pouillou.net>, Sebastian Reichel <sre@...nel.org>
Cc: linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-mips@...r.kernel.org, linux-pm@...r.kernel.org, 
 Matteo Martelli <matteomartelli3@...il.com>
Subject: [PATCH 4/7] iio: as73211: copy/release available integration times
 to fix race

While available integration times are being printed to sysfs by iio core
(iio_read_channel_info_avail), the sampling frequency might be changed.
This could cause the buffer shared with iio core to be corrupted. To
prevent it, make a copy of the integration times buffer and free it in
the read_avail_release_resource callback.

Signed-off-by: Matteo Martelli <matteomartelli3@...il.com>
---
 drivers/iio/light/as73211.c | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/light/as73211.c b/drivers/iio/light/as73211.c
index be0068081ebbbb37fdfb252b67a77b302ff725f6..520c898e0ff9c530b4fdd45589559f9014d7992c 100644
--- a/drivers/iio/light/as73211.c
+++ b/drivers/iio/light/as73211.c
@@ -493,17 +493,33 @@ static int as73211_read_avail(struct iio_dev *indio_dev, struct iio_chan_spec co
 		*type = IIO_VAL_INT;
 		return IIO_AVAIL_LIST;
 
-	case IIO_CHAN_INFO_INT_TIME:
+	case IIO_CHAN_INFO_INT_TIME: {
 		*length = ARRAY_SIZE(data->int_time_avail);
-		*vals = data->int_time_avail;
 		*type = IIO_VAL_INT_PLUS_MICRO;
-		return IIO_AVAIL_LIST;
 
+		guard(mutex)(&data->mutex);
+
+		*vals = kmemdup_array(data->int_time_avail, *length,
+				      sizeof(int), GFP_KERNEL);
+		if (!*vals)
+			return -ENOMEM;
+
+		return IIO_AVAIL_LIST;
+	}
 	default:
 		return -EINVAL;
 	}
 }
 
+static void as73211_read_avail_release_res(struct iio_dev *indio_dev,
+					   struct iio_chan_spec const *chan,
+					   const int *vals, long mask)
+{
+	if (mask == IIO_CHAN_INFO_INT_TIME)
+		kfree(vals);
+}
+
+
 static int _as73211_write_raw(struct iio_dev *indio_dev,
 			       struct iio_chan_spec const *chan __always_unused,
 			       int val, int val2, long mask)
@@ -699,6 +715,7 @@ static irqreturn_t as73211_trigger_handler(int irq __always_unused, void *p)
 static const struct iio_info as73211_info = {
 	.read_raw = as73211_read_raw,
 	.read_avail = as73211_read_avail,
+	.read_avail_release_resource = as73211_read_avail_release_res,
 	.write_raw = as73211_write_raw,
 };
 

-- 
2.46.2