[PATCH 3/5] i2c: ibm_iic: fix device_node refcount leak in iic_probe()/iic_remove()

[Liu Zhenlong <dragonliu2018@gmail.com>]

iic_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 iic_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 the probe error cleanup (error_cleanup,
which covers the i2c_add_adapter() failure path; the earlier error paths
jump to the same label before of_node_get() runs, but dev is kzalloc'ed
so dev->adap.dev.of_node is NULL and of_node_put() is a no-op there) and
to iic_remove().

In iic_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 ppc44x defconfig; no
hardware available for runtime testing.

Fixes: 9fd049927ccb ("of/i2c: Generalize OF support")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-5
Signed-off-by: Liu Zhenlong <dragonliu2018@gmail.com>
---
 drivers/i2c/busses/i2c-ibm_iic.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/i2c/busses/i2c-ibm_iic.c b/drivers/i2c/busses/i2c-ibm_iic.c
index 7c70e8bda24e..5c3b973c40d9 100644
--- a/drivers/i2c/busses/i2c-ibm_iic.c
+++ b/drivers/i2c/busses/i2c-ibm_iic.c
@@ -751,6 +751,8 @@ static int iic_probe(struct platform_device *ofdev)
 		free_irq(dev->irq, dev);
 	}
 
+	of_node_put(dev->adap.dev.of_node);
+
 	if (dev->vaddr)
 		iounmap(dev->vaddr);
 
@@ -764,8 +766,10 @@ static int iic_probe(struct platform_device *ofdev)
 static void iic_remove(struct platform_device *ofdev)
 {
 	struct ibm_iic_private *dev = platform_get_drvdata(ofdev);
+	struct device_node *node = dev->adap.dev.of_node;
 
 	i2c_del_adapter(&dev->adap);
+	of_node_put(node);
 
 	if (dev->irq) {
 		iic_interrupt_mode(dev, 0);
-- 
2.55.0