of: overlay: add tests to validate kfrees from overlay removal

Add checks:
  - attempted kfree due to refcount reaching zero before overlay
    is removed
  - properties linked to an overlay node when the node is removed
  - node refcount > one during node removal in a changeset destroy,
    if the node was created by the changeset

After applying this patch, several validation warnings will be
reported from the devicetree unittest during boot due to
pre-existing devicetree bugs. The warnings will be similar to:

  OF: ERROR: of_node_release(), unexpected properties in /testcase-data/overlay-node/test-bus/test-unittest11
  OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /testcase-data-2/substation@100/
  hvac-medium-2

Tested-by: Alan Tull <atull@kernel.org>
Signed-off-by: Frank Rowand <frank.rowand@sony.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c
index f4f8ed9b5454..12c3f9a15e94 100644
--- a/drivers/of/dynamic.c
+++ b/drivers/of/dynamic.c
@@ -330,6 +330,25 @@ void of_node_release(struct kobject *kobj)
 	if (!of_node_check_flag(node, OF_DYNAMIC))
 		return;
 
+	if (of_node_check_flag(node, OF_OVERLAY)) {
+
+		if (!of_node_check_flag(node, OF_OVERLAY_FREE_CSET)) {
+			/* premature refcount of zero, do not free memory */
+			pr_err("ERROR: memory leak before free overlay changeset,  %pOF\n",
+			       node);
+			return;
+		}
+
+		/*
+		 * If node->properties non-empty then properties were added
+		 * to this node either by different overlay that has not
+		 * yet been removed, or by a non-overlay mechanism.
+		 */
+		if (node->properties)
+			pr_err("ERROR: %s(), unexpected properties in %pOF\n",
+			       __func__, node);
+	}
+
 	property_list_free(node->properties);
 	property_list_free(node->deadprops);
 
@@ -434,6 +453,16 @@ struct device_node *__of_node_dup(const struct device_node *np,
 
 static void __of_changeset_entry_destroy(struct of_changeset_entry *ce)
 {
+	if (ce->action == OF_RECONFIG_ATTACH_NODE &&
+	    of_node_check_flag(ce->np, OF_OVERLAY)) {
+		if (kref_read(&ce->np->kobj.kref) > 1) {
+			pr_err("ERROR: memory leak, expected refcount 1 instead of %d, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node %pOF\n",
+			       kref_read(&ce->np->kobj.kref), ce->np);
+		} else {
+			of_node_set_flag(ce->np, OF_OVERLAY_FREE_CSET);
+		}
+	}
+
 	of_node_put(ce->np);
 	list_del(&ce->node);
 	kfree(ce);