[PATCH 5.4 121/255] iio: inkern: only release the device node when done with it

[Greg Kroah-Hartman]

From: Nuno Sá <nuno.sa@xxxxxxxxxx>

[ 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@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20220715122903.332535-2-nuno.sa@xxxxxxxxxx
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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 ca0fe902a7db..d00f3045557c 100644
--- a/drivers/iio/inkern.c
+++ b/drivers/iio/inkern.c
@@ -136,9 +136,10 @@ 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;
@@ -146,6 +147,7 @@ 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