[PATCH v4 02/10] media: microchip-isc: take a reference on the parsed endpoints

for_each_endpoint_of_node() drops the reference on the current node as
it advances. xisc_parse_dt() and isc_parse_dt() store the node in
subdev_entity->epn and release it later with of_node_put(), but never
took their own reference, so the stored pointer refers to an
already-released node. This underflows the refcount and can
use-after-free, reachable through the camera device tree overlay.

Take a reference with of_node_get() when storing the node, and drop it
in microchip_isc_subdev_cleanup() so the entities the bind loop never
reaches on an early exit do not leak it.

Fixes: c9aa973884a1 ("media: atmel: atmel-isc: add microchip-xisc driver")
Fixes: d6701f13bd07 ("media: atmel: Use v4l2_async_notifier_add_fwnode_remote_subdev")
Cc: [email protected]
Signed-off-by: Balakrishnan Sambath <[email protected]>
---
 drivers/media/platform/microchip/microchip-isc-base.c  |  6 ++++++
 .../media/platform/microchip/microchip-sama5d2-isc.c   | 18 ++++++++++++------
 .../media/platform/microchip/microchip-sama7g5-isc.c   | 18 ++++++++++++------
 3 files changed, 30 insertions(+), 12 deletions(-)

diff --git a/drivers/media/platform/microchip/microchip-isc-base.c b/drivers/media/platform/microchip/microchip-isc-base.c
index eebbcb28a7ee..ca4f3b5f58aa 100644
--- a/drivers/media/platform/microchip/microchip-isc-base.c
+++ b/drivers/media/platform/microchip/microchip-isc-base.c
@@ -1853,6 +1853,12 @@ void microchip_isc_subdev_cleanup(struct isc_device *isc)
 	list_for_each_entry(subdev_entity, &isc->subdev_entities, list) {
 		v4l2_async_nf_unregister(&subdev_entity->notifier);
 		v4l2_async_nf_cleanup(&subdev_entity->notifier);
+		/*
+		 * Release the endpoint reference taken while parsing. It is
+		 * NULL for entities the bind loop already consumed, so this
+		 * only drops the ones left over on an early exit.
+		 */
+		of_node_put(subdev_entity->epn);
 	}
 
 	INIT_LIST_HEAD(&isc->subdev_entities);
diff --git a/drivers/media/platform/microchip/microchip-sama5d2-isc.c b/drivers/media/platform/microchip/microchip-sama5d2-isc.c
index 25d241b4c66a..532f2b50e2ea 100644
--- a/drivers/media/platform/microchip/microchip-sama5d2-isc.c
+++ b/drivers/media/platform/microchip/microchip-sama5d2-isc.c
@@ -357,28 +357,28 @@ static int isc_parse_dt(struct device *dev, struct isc_device *isc)
 	struct device_node *epn;
 	struct isc_subdev_entity *subdev_entity;
 	unsigned int flags;
+	int ret;
 
 	INIT_LIST_HEAD(&isc->subdev_entities);
 
 	for_each_endpoint_of_node(np, epn) {
 		struct v4l2_fwnode_endpoint v4l2_epn = { .bus_type = 0 };
-		int ret;
 
 		ret = v4l2_fwnode_endpoint_parse(of_fwnode_handle(epn),
 						 &v4l2_epn);
 		if (ret) {
-			of_node_put(epn);
 			dev_err(dev, "Could not parse the endpoint\n");
-			return -EINVAL;
+			ret = -EINVAL;
+			goto err_put;
 		}
 
 		subdev_entity = devm_kzalloc(dev, sizeof(*subdev_entity),
 					     GFP_KERNEL);
 		if (!subdev_entity) {
-			of_node_put(epn);
-			return -ENOMEM;
+			ret = -ENOMEM;
+			goto err_put;
 		}
-		subdev_entity->epn = epn;
+		subdev_entity->epn = of_node_get(epn);
 
 		flags = v4l2_epn.bus.parallel.flags;
 
@@ -399,6 +399,12 @@ static int isc_parse_dt(struct device *dev, struct isc_device *isc)
 	}
 
 	return 0;
+
+err_put:
+	of_node_put(epn);
+	list_for_each_entry(subdev_entity, &isc->subdev_entities, list)
+		of_node_put(subdev_entity->epn);
+	return ret;
 }
 
 static int microchip_isc_probe(struct platform_device *pdev)
diff --git a/drivers/media/platform/microchip/microchip-sama7g5-isc.c b/drivers/media/platform/microchip/microchip-sama7g5-isc.c
index 998146adabd8..0b72a61b51ee 100644
--- a/drivers/media/platform/microchip/microchip-sama7g5-isc.c
+++ b/drivers/media/platform/microchip/microchip-sama7g5-isc.c
@@ -341,6 +341,7 @@ static int xisc_parse_dt(struct device *dev, struct isc_device *isc)
 	struct isc_subdev_entity *subdev_entity;
 	unsigned int flags;
 	bool mipi_mode;
+	int ret;
 
 	INIT_LIST_HEAD(&isc->subdev_entities);
 
@@ -348,23 +349,22 @@ static int xisc_parse_dt(struct device *dev, struct isc_device *isc)
 
 	for_each_endpoint_of_node(np, epn) {
 		struct v4l2_fwnode_endpoint v4l2_epn = { .bus_type = 0 };
-		int ret;
 
 		ret = v4l2_fwnode_endpoint_parse(of_fwnode_handle(epn),
 						 &v4l2_epn);
 		if (ret) {
-			of_node_put(epn);
 			dev_err(dev, "Could not parse the endpoint\n");
-			return -EINVAL;
+			ret = -EINVAL;
+			goto err_put;
 		}
 
 		subdev_entity = devm_kzalloc(dev, sizeof(*subdev_entity),
 					     GFP_KERNEL);
 		if (!subdev_entity) {
-			of_node_put(epn);
-			return -ENOMEM;
+			ret = -ENOMEM;
+			goto err_put;
 		}
-		subdev_entity->epn = epn;
+		subdev_entity->epn = of_node_get(epn);
 
 		flags = v4l2_epn.bus.parallel.flags;
 
@@ -388,6 +388,12 @@ static int xisc_parse_dt(struct device *dev, struct isc_device *isc)
 	}
 
 	return 0;
+
+err_put:
+	of_node_put(epn);
+	list_for_each_entry(subdev_entity, &isc->subdev_entities, list)
+		of_node_put(subdev_entity->epn);
+	return ret;
 }
 
 static int microchip_xisc_probe(struct platform_device *pdev)

-- 
2.34.1