linux-kernel - [PATCH 4.9 090/159] iio: inkern: only release the device node when done with it

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Message-Id: <20221024112952.701629645@linuxfoundation.org>
Date:   Mon, 24 Oct 2022 13:30:44 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Nuno Sá <nuno.sa@...log.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.9 090/159] iio: inkern: only release the device node when done with it

From: Nuno Sá <nuno.sa@...log.com>

[ Upstream commit 79c3e84874c7d14f04ad58313b64955a0d2e9437 ]

'of_node_put()' can potentially release the memory pointed to by
'iiospec.np' which would leave us with an invalid pointer (and we would
still pass it in 'of_xlate()'). Note that it is not guaranteed for the
of_node lifespan to be attached to the device (to which is attached)
lifespan so that there is (even though very unlikely) the possibility
for the node to be freed while the device is still around. Thus, as there
are indeed some of_xlate users which do access the node, a race is indeed
possible.

As such, we can only release the node after we are done with it.

Fixes: 17d82b47a215d ("iio: Add OF support")
Signed-off-by: Nuno Sá <nuno.sa@...log.com>
Link: https://lore.kernel.org/r/20220715122903.332535-2-nuno.sa@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/iio/inkern.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
index 218cf4567ab5..13be4c8d7fd3 100644
--- a/drivers/iio/inkern.c
+++ b/drivers/iio/inkern.c
@@ -139,9 +139,10 @@ static int __of_iio_channel_get(struct iio_channel *channel,
 
 	idev = bus_find_device(&iio_bus_type, NULL, iiospec.np,
 			       iio_dev_node_match);
-	of_node_put(iiospec.np);
-	if (idev == NULL)
+	if (idev == NULL) {
+		of_node_put(iiospec.np);
 		return -EPROBE_DEFER;
+	}
 
 	indio_dev = dev_to_iio_dev(idev);
 	channel->indio_dev = indio_dev;
@@ -149,6 +150,7 @@ static int __of_iio_channel_get(struct iio_channel *channel,
 		index = indio_dev->info->of_xlate(indio_dev, &iiospec);
 	else
 		index = __of_iio_simple_xlate(indio_dev, &iiospec);
+	of_node_put(iiospec.np);
 	if (index < 0)
 		goto err_put;
 	channel->channel = &indio_dev->channels[index];
-- 
2.35.1