[PATCH 4.19 71/73] of: overlay: validate overlay properties #address-cells and #size-cells

[Greg Kroah-Hartman]

From: Frank Rowand <frank.rowand@xxxxxxxx>

commit 6f75118800acf77f8ad6afec61ca1b2349ade371 upstream.

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.

Tested-by: Alan Tull <atull@xxxxxxxxxx>
Signed-off-by: Frank Rowand <frank.rowand@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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

--- a/drivers/of/overlay.c
+++ b/drivers/of/overlay.c
@@ -287,7 +287,12 @@ err_free_target_path:
  * @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
 {
 	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
 	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);
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -968,6 +968,12 @@ static inline int of_cpu_node_to_id(stru
 #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