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>

3 files changed, 40 insertions, 5 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);
diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
index 42b1f73ac5f6..f5fc8859a7ee 100644
--- a/drivers/of/overlay.c
+++ b/drivers/of/overlay.c
@@ -373,6 +373,7 @@ static int add_changeset_node(struct overlay_changeset *ovcs,
                         return -ENOMEM;
 
                 tchild->parent = target_node;
+                of_node_set_flag(tchild, OF_OVERLAY);
 
                 ret = of_changeset_attach_node(&ovcs->cset, tchild);
                 if (ret)
diff --git a/include/linux/of.h b/include/linux/of.h
index a5aee3c438ad..664cd5573ae2 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -138,11 +138,16 @@ extern struct device_node *of_aliases;
 extern struct device_node *of_stdout;
 extern raw_spinlock_t devtree_lock;
 
-/* flag descriptions (need to be visible even when !CONFIG_OF) */
-#define OF_DYNAMIC      1 /* node and properties were allocated via kmalloc */
-#define OF_DETACHED     2 /* node has been detached from the device tree */
-#define OF_POPULATED    3 /* device already created for the node */
-#define OF_POPULATED_BUS        4 /* of_platform_populate recursed to children of this node */
+/*
+ * struct device_node flag descriptions
+ * (need to be visible even when !CONFIG_OF)
+ */
+#define OF_DYNAMIC              1 /* (and properties) allocated via kmalloc */
+#define OF_DETACHED             2 /* detached from the device tree */
+#define OF_POPULATED            3 /* device already created */
+#define OF_POPULATED_BUS        4 /* platform bus created for children */
+#define OF_OVERLAY              5 /* allocated for an overlay */
+#define OF_OVERLAY_FREE_CSET    6 /* in overlay cset being freed */
 
 #define OF_BAD_ADDR     ((u64)-1)