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Subject[PATCH v4 01/18] of: overlay: add tests to validate kfrees from overlay removal
Date
From: Frank Rowand <frank.rowand@sony.com>

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() overlay node /testcase-data/overlay-node/test-bus/test-unittest11/test-unittest111 contains unexpected properties
OF: ERROR: memory leak - destroy cset entry: attach overlay node /testcase-data-2/substation@100/hvac-medium-2 expected refcount 1 instead of 2. of_node_get() / of_node_put() are unbalanced for this node.

Signed-off-by: Frank Rowand <frank.rowand@sony.com>
---
Changes since v3:
- Add expected value of refcount for destroy cset entry error. Also
explain the cause of the error.

drivers/of/dynamic.c | 29 +++++++++++++++++++++++++++++
drivers/of/overlay.c | 1 +
include/linux/of.h | 15 ++++++++++-----
3 files changed, 40 insertions(+), 5 deletions(-)

diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c
index f4f8ed9b5454..24c97b7a050f 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 %s() overlay node %pOF before free overlay changeset\n",
+ __func__, 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() overlay node %pOF contains unexpected properties\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 - destroy cset entry: attach overlay node %pOF expected refcount 1 instead of %d. of_node_get() / of_node_put() are unbalanced for this node.\n",
+ ce->np, kref_read(&ce->np->kobj.kref));
+ } 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 eda57ef12fd0..1176cb4b6e4e 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 4d25e4f952d9..aa1dafaec6ae 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -138,11 +138,16 @@ static inline void of_node_put(struct device_node *node) { }
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)

--
Frank Rowand <frank.rowand@sony.com>
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