[PATCH v5 09/18] of: overlay: validate overlay properties #address-cells and #size-cells

[frowand . list]

From: Frank Rowand <frank.rowand@xxxxxxxx>

If overlay properties #address-cells or #size-cells are already in
the live devicetree for any given node, then the values in the
overlay must match the values in the live tree.

If the properties are already in the live tree then there is no
need to create a changeset entry to add them since they must
have the same value.  This reduces the memory used by the
changeset and eliminates a possible memory leak.

Signed-off-by: Frank Rowand <frank.rowand@xxxxxxxx>
---

Changes since v4:
  - create of_prop_val_eq() and change open code to use it
  - remove extra blank lines

 drivers/of/overlay.c | 32 +++++++++++++++++++++++++++++---
 include/linux/of.h   |  6 ++++++
 2 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
index 272a0d1a5e18..e20d8923f475 100644
--- a/drivers/of/overlay.c
+++ b/drivers/of/overlay.c
@@ -287,7 +287,12 @@ static struct property *dup_and_fixup_symbol_prop(
  * @target may be either in the live devicetree or in a new subtree that
  * is contained in the changeset.
  *
- * Some special properties are not updated (no error returned).
+ * Some special properties are not added or updated (no error returned):
+ * "name", "phandle", "linux,phandle".
+ *
+ * Properties "#address-cells" and "#size-cells" are not updated if they
+ * are already in the live tree, but if present in the live tree, the values
+ * in the overlay must match the values in the live tree.
  *
  * Update of property in symbols node is not allowed.
  *
@@ -300,6 +305,7 @@ static int add_changeset_property(struct overlay_changeset *ovcs,
 {
 	struct property *new_prop = NULL, *prop;
 	int ret = 0;
+	bool check_for_non_overlay_node = false;
 
 	if (!of_prop_cmp(overlay_prop->name, "name") ||
 	    !of_prop_cmp(overlay_prop->name, "phandle") ||
@@ -322,12 +328,32 @@ static int add_changeset_property(struct overlay_changeset *ovcs,
 	if (!new_prop)
 		return -ENOMEM;
 
-	if (!prop)
+	if (!prop) {
+		check_for_non_overlay_node = true;
 		ret = of_changeset_add_property(&ovcs->cset, target->np,
 						new_prop);
-	else
+	} else if (!of_prop_cmp(prop->name, "#address-cells")) {
+		if (!of_prop_val_eq(prop, new_prop)) {
+			pr_err("ERROR: changing value of #address-cells is not allowed in %pOF\n",
+			       target->np);
+			ret = -EINVAL;
+		}
+	} else if (!of_prop_cmp(prop->name, "#size-cells")) {
+		if (!of_prop_val_eq(prop, new_prop)) {
+			pr_err("ERROR: changing value of #size-cells is not allowed in %pOF\n",
+			       target->np);
+			ret = -EINVAL;
+		}
+	} else {
+		check_for_non_overlay_node = true;
 		ret = of_changeset_update_property(&ovcs->cset, target->np,
 						   new_prop);
+	}
+
+	if (check_for_non_overlay_node &&
+	    !of_node_check_flag(target->np, OF_OVERLAY))
+		pr_err("WARNING: memory leak will occur if overlay removed, property: %pOF/%s\n",
+		       target->np, new_prop->name);
 
 	if (ret) {
 		kfree(new_prop->name);
diff --git a/include/linux/of.h b/include/linux/of.h
index 72c593455019..1bb14a1f7227 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -947,6 +947,12 @@ static inline int of_cpu_node_to_id(struct device_node *np)
 #define of_node_cmp(s1, s2)		strcasecmp((s1), (s2))
 #endif
 
+static inline int of_prop_val_eq(struct property *p1, struct property *p2)
+{
+	return p1->length == p2->length &&
+	       !memcmp(p1->value, p2->value, (size_t)p1->length);
+}
+
 #if defined(CONFIG_OF) && defined(CONFIG_NUMA)
 extern int of_node_to_nid(struct device_node *np);
 #else
-- 
Frank Rowand <frank.rowand@xxxxxxxx>