[PATCH] i2c: qcom-cci: fix device_node refcount leak in cci_probe()/cci_remove()

[PATCH] i2c: qcom-cci: fix device_node refcount leak in cci_probe()/cci_remove()

[Liu Zhenlong]

cci_probe() calls of_node_get() to take an extra reference on the
child device_node when assigning it to the adapter device.  The
matching of_node_put() calls exist in both the error cleanup path
and cci_remove(), but they are placed after i2c_del_adapter().

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, turning it into a
no-op.  The reference taken by of_node_get() is never released, leaking
the device_node on every cleanup of already-registered adapters and
every adapter removal.

The commit that added of_node_get() and the matching of_node_put()
calls placed the puts after i2c_del_adapter(), so the bug has been
present since the fix was introduced.

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()")).

The of_node_put() in the i2c_add_adapter() failure path (before any
i2c_del_adapter() runs) is correct and left unchanged.

Fixes: 02a4a69667a2 ("i2c: qcom-cci: don't put a device tree node before i2c_add_adapter()")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-5
Signed-off-by: Liu Zhenlong <dragonliu2018@gmail.com>
---
 drivers/i2c/busses/i2c-qcom-cci.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-qcom-cci.c b/drivers/i2c/busses/i2c-qcom-cci.c
index bdeda3979c48..61c535b8196f 100644
--- a/drivers/i2c/busses/i2c-qcom-cci.c
+++ b/drivers/i2c/busses/i2c-qcom-cci.c
@@ -618,8 +618,10 @@ static int cci_probe(struct platform_device *pdev)
 
 	for (--i ; i >= 0; i--) {
 		if (cci->master[i].cci) {
+			struct device_node *node = cci->master[i].adap.dev.of_node;
+
 			i2c_del_adapter(&cci->master[i].adap);
-			of_node_put(cci->master[i].adap.dev.of_node);
+			of_node_put(node);
 		}
 	}
 disable_clocks:
@@ -635,8 +637,10 @@ static void cci_remove(struct platform_device *pdev)
 
 	for (i = 0; i < cci->data->num_masters; i++) {
 		if (cci->master[i].cci) {
+			struct device_node *node = cci->master[i].adap.dev.of_node;
+
 			i2c_del_adapter(&cci->master[i].adap);
-			of_node_put(cci->master[i].adap.dev.of_node);
+			of_node_put(node);
 			cci_halt(cci, i);
 		}
 	}
-- 
2.55.0