[PATCH 4/5] i2c: opal: fix device_node refcount leak in i2c_opal_probe/remove()

[Liu Zhenlong <dragonliu2018@gmail.com>]

i2c_opal_probe() calls of_node_get() to take an extra reference on the
platform device's of_node when assigning it to the adapter device, but
neither the probe error path nor i2c_opal_remove() drops it.

device_release() does not call of_node_put() and i2c_adapter_dev_release()
only completes a struct, so the extra reference is never released, leaking
the device_node on every probe failure and every adapter removal.

Add the matching of_node_put() to both paths.

In the probe error path, i2c_add_adapter() failure does not run
i2c_del_adapter(), so of_node_put(adapter->dev.of_node) is safe.

In i2c_opal_remove(), i2c_del_adapter() clears adap->dev with memset()
at the end (commit bd4bc3dbded9 ("i2c: Clear i2c_adapter.dev on adapter
removal")), which zeroes adap->dev.of_node before of_node_put() runs.
Cache the pointer before calling i2c_del_adapter(), the same approach
used in i2c-mux (i2c_mux_del_adapters) and mtd (commit 56570bdad5e3
("mtd: core: Fix refcount error in del_mtd_device()")).

Compile-tested with gcc-powerpc-linux-gnu on powernv defconfig; no
hardware available for runtime testing.

Fixes: 470834508f87 ("i2c: Driver to expose PowerNV platform i2c busses")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-5
Signed-off-by: Liu Zhenlong <dragonliu2018@gmail.com>
---
 drivers/i2c/busses/i2c-opal.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-opal.c b/drivers/i2c/busses/i2c-opal.c
index c9b62892397a..43b3d17e933b 100644
--- a/drivers/i2c/busses/i2c-opal.c
+++ b/drivers/i2c/busses/i2c-opal.c
@@ -226,8 +226,10 @@ static int i2c_opal_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, adapter);
 	rc = i2c_add_adapter(adapter);
-	if (rc)
+	if (rc) {
 		dev_err(&pdev->dev, "Failed to register the i2c adapter\n");
+		of_node_put(adapter->dev.of_node);
+	}
 
 	return rc;
 }
@@ -235,8 +237,10 @@ static int i2c_opal_probe(struct platform_device *pdev)
 static void i2c_opal_remove(struct platform_device *pdev)
 {
 	struct i2c_adapter *adapter = platform_get_drvdata(pdev);
+	struct device_node *node = adapter->dev.of_node;
 
 	i2c_del_adapter(adapter);
+	of_node_put(node);
 }
 
 static const struct of_device_id i2c_opal_of_match[] = {
-- 
2.55.0