[PATCH] pmdomain: mediatek: fix use-after-free in scpsys_get_bus_protection_legacy()

[Wentao Liang]

In scpsys_get_bus_protection_legacy(), of_find_node_with_property()
returns a device node with its reference count incremented. The function
then calls of_node_put(node) before checking whether
syscon_regmap_lookup_by_phandle() returns an error. If an error occurs,
dev_err_probe() dereferences the node pointer to print diagnostic
information, but the node memory may have already been freed due to the
earlier of_node_put(), leading to a use-after-free vulnerability.

Fix this by moving the of_node_put() call after the error check, ensuring
the node is still valid when accessed in the error path.

Fixes: c29345fa5f66 ("pmdomain: mediatek: Refactor bus protection regmaps retrieval")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Wentao Liang <vulab@xxxxxxxxxxx>
---
 drivers/pmdomain/mediatek/mtk-pm-domains.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/pmdomain/mediatek/mtk-pm-domains.c b/drivers/pmdomain/mediatek/mtk-pm-domains.c
index e2800aa1bc59..d3b36f32417c 100644
--- a/drivers/pmdomain/mediatek/mtk-pm-domains.c
+++ b/drivers/pmdomain/mediatek/mtk-pm-domains.c
@@ -993,6 +993,7 @@ static int scpsys_get_bus_protection_legacy(struct device *dev, struct scpsys *s
 	struct device_node *node, *smi_np;
 	int num_regmaps = 0, i, j;
 	struct regmap *regmap[3];
+	int ret = 0;
 
 	/*
 	 * Legacy code retrieves a maximum of three bus protection handles:
@@ -1043,11 +1044,14 @@ static int scpsys_get_bus_protection_legacy(struct device *dev, struct scpsys *s
 	if (node) {
 		regmap[2] = syscon_regmap_lookup_by_phandle(node, "mediatek,infracfg-nao");
 		num_regmaps++;
-		of_node_put(node);
-		if (IS_ERR(regmap[2]))
-			return dev_err_probe(dev, PTR_ERR(regmap[2]),
+		if (IS_ERR(regmap[2])) {
+			ret = dev_err_probe(dev, PTR_ERR(regmap[2]),
 					     "%pOF: failed to get infracfg regmap\n",
 					     node);
+			of_node_put(node);
+			return ret;
+		}
+		of_node_put(node);
 	} else {
 		regmap[2] = NULL;
 	}
-- 
2.34.1