bus: fsl-mc: Fix potential double device reference in fsl_mc_get_endpoint()

The fsl_mc_get_endpoint() function may call fsl_mc_device_lookup()
twice, which would increment the device's reference count twice if
both lookups find a device. This could lead to a reference count leak.

Found by code review.

Cc: [email protected]
Fixes: 1ac210d ("bus: fsl-mc: add the fsl_mc_get_endpoint function")
Signed-off-by: Ma Ke <[email protected]>
Tested-by: Ioana Ciornei <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Fixes: 8567494 ("bus: fsl-mc: rescan devices if endpoint not found")
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: Ma Ke

drivers/bus/fsl-mc/fsl-mc-bus.c

@@ -943,6 +943,7 @@ struct fsl_mc_device *fsl_mc_get_endpoint(struct fsl_mc_device *mc_dev,
 	struct fsl_mc_obj_desc endpoint_desc = {{ 0 }};
 	struct dprc_endpoint endpoint1 = {{ 0 }};
 	struct dprc_endpoint endpoint2 = {{ 0 }};
+	struct fsl_mc_bus *mc_bus;
 	int state, err;
 
 	mc_bus_dev = to_fsl_mc_device(mc_dev->dev.parent);
@@ -966,24 +967,22 @@ struct fsl_mc_device *fsl_mc_get_endpoint(struct fsl_mc_device *mc_dev,
 	strcpy(endpoint_desc.type, endpoint2.type);
 	endpoint_desc.id = endpoint2.id;
 	endpoint = fsl_mc_device_lookup(&endpoint_desc, mc_bus_dev);
+	if (endpoint)
+		return endpoint;
 
 	/*
 	 * We know that the device has an endpoint because we verified by
 	 * interrogating the firmware. This is the case when the device was not
 	 * yet discovered by the fsl-mc bus, thus the lookup returned NULL.
 	 * Force a rescan of the devices in this container and retry the lookup.
 	 */
-	if (!endpoint) {
-		struct fsl_mc_bus *mc_bus = to_fsl_mc_bus(mc_bus_dev);
-
-		if (mutex_trylock(&mc_bus->scan_mutex)) {
-			err = dprc_scan_objects(mc_bus_dev, true);
-			mutex_unlock(&mc_bus->scan_mutex);
-		}
-
-		if (err < 0)
-			return ERR_PTR(err);
+	mc_bus = to_fsl_mc_bus(mc_bus_dev);
+	if (mutex_trylock(&mc_bus->scan_mutex)) {
+		err = dprc_scan_objects(mc_bus_dev, true);
+		mutex_unlock(&mc_bus->scan_mutex);
 	}
+	if (err < 0)
+		return ERR_PTR(err);
 
 	endpoint = fsl_mc_device_lookup(&endpoint_desc, mc_bus_dev);
 	/*