4 files changed, 170 insertions, 3 deletions

diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c
index cd3821a6444f..becb80f762c8 100644
--- a/drivers/of/dynamic.c
+++ b/drivers/of/dynamic.c
@@ -332,7 +332,19 @@ void of_node_release(struct kobject *kobj)
 	/* We should never be releasing nodes that haven't been detached. */
 	if (!of_node_check_flag(node, OF_DETACHED)) {
 		pr_err("ERROR: Bad of_node_put() on %pOF\n", node);
-		dump_stack();
+
+		/*
+		 * of unittests will test this path.  Do not print the stack
+		 * trace when the error is caused by unittest so that we do
+		 * not display what a normal developer might reasonably
+		 * consider a real bug.
+		 */
+		if (!IS_ENABLED(CONFIG_OF_UNITTEST) ||
+		    strcmp(node->parent->full_name, "testcase-data")) {
+			dump_stack();
+			pr_err("ERROR: next of_node_put() on this node will result in a kboject warning 'refcount_t: underflow; use-after-free.'\n");
+		}
+
 		return;
 	}
 	if (!of_node_check_flag(node, OF_DYNAMIC))
diff --git a/drivers/of/unittest-data/testcases_common.dtsi b/drivers/of/unittest-data/testcases_common.dtsi
index 19292bbb4cbb..e7887f2301c1 100644
--- a/drivers/of/unittest-data/testcases_common.dtsi
+++ b/drivers/of/unittest-data/testcases_common.dtsi
@@ -17,3 +17,4 @@
 #include "tests-address.dtsi"
 #include "tests-platform.dtsi"
 #include "tests-overlay.dtsi"
+#include "tests-lifecycle.dtsi"
diff --git a/drivers/of/unittest-data/tests-lifecycle.dtsi b/drivers/of/unittest-data/tests-lifecycle.dtsi
new file mode 100644
index 000000000000..28509a8783a7
--- /dev/null
+++ b/drivers/of/unittest-data/tests-lifecycle.dtsi
@@ -0,0 +1,8 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/ {
+	testcase-data {
+		refcount-node {
+		};
+	};
+};
diff --git a/drivers/of/unittest.c b/drivers/of/unittest.c
index bc0f1e50a4be..b5a7a31d8bd2 100644
--- a/drivers/of/unittest.c
+++ b/drivers/of/unittest.c
@@ -54,8 +54,9 @@ static struct unittest_results {
  * Print the expected message only if the current loglevel will allow
  * the actual message to print.
  *
- * Do not use EXPECT_BEGIN() or EXPECT_END() for messages generated by
- * pr_debug().
+ * Do not use EXPECT_BEGIN(), EXPECT_END(), EXPECT_NOT_BEGIN(), or
+ * EXPECT_NOT_END() to report messages expected to be reported or not
+ * reported by pr_debug().
  */
 #define EXPECT_BEGIN(level, fmt, ...) \
 	printk(level pr_fmt("EXPECT \\ : ") fmt, ##__VA_ARGS__)
@@ -63,6 +64,12 @@ static struct unittest_results {
 #define EXPECT_END(level, fmt, ...) \
 	printk(level pr_fmt("EXPECT / : ") fmt, ##__VA_ARGS__)
 
+#define EXPECT_NOT_BEGIN(level, fmt, ...) \
+	printk(level pr_fmt("EXPECT_NOT \\ : ") fmt, ##__VA_ARGS__)
+
+#define EXPECT_NOT_END(level, fmt, ...) \
+	printk(level pr_fmt("EXPECT_NOT / : ") fmt, ##__VA_ARGS__)
+
 static void __init of_unittest_find_node_by_name(void)
 {
 	struct device_node *np;
@@ -1488,6 +1495,7 @@ static int __init unittest_data_add(void)
 		struct device_node *next = np->sibling;
 
 		np->parent = of_root;
+		/* this will clear OF_DETACHED in np and children */
 		attach_node_and_children(np);
 		np = next;
 	}
@@ -2998,6 +3006,143 @@ out:
 static inline void __init of_unittest_overlay(void) { }
 #endif
 
+static void __init of_unittest_lifecycle(void)
+{
+#ifdef CONFIG_OF_DYNAMIC
+	unsigned int refcount;
+	int found_refcount_one = 0;
+	int put_count = 0;
+	struct device_node *np;
+	struct device_node *prev_sibling, *next_sibling;
+	const char *refcount_path = "/testcase-data/refcount-node";
+	const char *refcount_parent_path = "/testcase-data";
+
+	/*
+	 * Node lifecycle tests, non-dynamic node:
+	 *
+	 * - Decrementing refcount to zero via of_node_put() should cause the
+	 *   attempt to free the node memory by of_node_release() to fail
+	 *   because the node is not a dynamic node.
+	 *
+	 * - Decrementing refcount past zero should result in additional
+	 *   errors reported.
+	 */
+
+	np = of_find_node_by_path(refcount_path);
+	unittest(np, "find refcount_path \"%s\"\n", refcount_path);
+	if (np == NULL)
+		goto out_skip_tests;
+
+	while (!found_refcount_one) {
+
+		if (put_count++ > 10) {
+			unittest(0, "guardrail to avoid infinite loop\n");
+			goto out_skip_tests;
+		}
+
+		refcount = kref_read(&np->kobj.kref);
+		if (refcount == 1)
+			found_refcount_one = 1;
+		else
+			of_node_put(np);
+	}
+
+	EXPECT_BEGIN(KERN_INFO, "OF: ERROR: of_node_release() detected bad of_node_put() on /testcase-data/refcount-node");
+
+	/*
+	 * refcount is now one, decrementing to zero will result in a call to
+	 * of_node_release() to free the node's memory, which should result
+	 * in an error
+	 */
+	unittest(1, "/testcase-data/refcount-node is one");
+	of_node_put(np);
+
+	EXPECT_END(KERN_INFO, "OF: ERROR: of_node_release() detected bad of_node_put() on /testcase-data/refcount-node");
+
+
+	/*
+	 * expect stack trace for subsequent of_node_put():
+	 *   __refcount_sub_and_test() calls:
+	 *   refcount_warn_saturate(r, REFCOUNT_SUB_UAF)
+	 *
+	 * Not capturing entire WARN_ONCE() trace with EXPECT_*(), just
+	 * the first three lines, and the last line.
+	 */
+	EXPECT_BEGIN(KERN_INFO, "------------[ cut here ]------------");
+	EXPECT_BEGIN(KERN_INFO, "WARNING: <<all>>");
+	EXPECT_BEGIN(KERN_INFO, "refcount_t: underflow; use-after-free.");
+	EXPECT_BEGIN(KERN_INFO, "---[ end trace <<int>> ]---");
+
+	/* refcount is now zero, this should fail */
+	unittest(1, "/testcase-data/refcount-node is zero");
+	of_node_put(np);
+
+	EXPECT_END(KERN_INFO, "---[ end trace <<int>> ]---");
+	EXPECT_END(KERN_INFO, "refcount_t: underflow; use-after-free.");
+	EXPECT_END(KERN_INFO, "WARNING: <<all>>");
+	EXPECT_END(KERN_INFO, "------------[ cut here ]------------");
+
+	/*
+	 * Q. do we expect to get yet another warning?
+	 * A. no, the WARNING is from WARN_ONCE()
+	 */
+	EXPECT_NOT_BEGIN(KERN_INFO, "------------[ cut here ]------------");
+	EXPECT_NOT_BEGIN(KERN_INFO, "WARNING: <<all>>");
+	EXPECT_NOT_BEGIN(KERN_INFO, "refcount_t: underflow; use-after-free.");
+	EXPECT_NOT_BEGIN(KERN_INFO, "---[ end trace <<int>> ]---");
+
+	unittest(1, "/testcase-data/refcount-node is zero, second time");
+	of_node_put(np);
+
+	EXPECT_NOT_END(KERN_INFO, "---[ end trace <<int>> ]---");
+	EXPECT_NOT_END(KERN_INFO, "refcount_t: underflow; use-after-free.");
+	EXPECT_NOT_END(KERN_INFO, "WARNING: <<all>>");
+	EXPECT_NOT_END(KERN_INFO, "------------[ cut here ]------------");
+
+	/*
+	 * refcount of zero will trigger stack traces from any further
+	 * attempt to of_node_get() node "refcount-node". One example of
+	 * this is where of_unittest_check_node_linkage() will recursively
+	 * scan the tree, with 'for_each_child_of_node()' doing an
+	 * of_node_get() of the children of a node.
+	 *
+	 * Prevent the stack trace by removing node "refcount-node" from
+	 * its parent's child list.
+	 *
+	 * WARNING:  EVIL, EVIL, EVIL:
+	 *
+	 *   Directly manipulate the child list of node /testcase-data to
+	 *   remove child refcount-node.  This is ignoring all proper methods
+	 *   of removing a child and will leak a small amount of memory.
+	 */
+
+	np = of_find_node_by_path(refcount_parent_path);
+	unittest(np, "find refcount_parent_path \"%s\"\n", refcount_parent_path);
+	unittest(np, "ERROR: devicetree live tree left in a 'bad state' if test fail\n");
+	if (np == NULL)
+		return;
+
+	prev_sibling = np->child;
+	next_sibling = prev_sibling->sibling;
+	if (!strcmp(prev_sibling->full_name, "refcount-node")) {
+		np->child = next_sibling;
+		next_sibling = next_sibling->sibling;
+	}
+	while (next_sibling) {
+		if (!strcmp(next_sibling->full_name, "refcount-node"))
+			prev_sibling->sibling = next_sibling->sibling;
+		prev_sibling = next_sibling;
+		next_sibling = next_sibling->sibling;
+	}
+	of_node_put(np);
+
+	return;
+
+out_skip_tests:
+#endif
+	unittest(0, "One or more lifecycle tests skipped\n");
+}
+
 #ifdef CONFIG_OF_OVERLAY
 
 /*
@@ -3502,6 +3647,7 @@ static int __init of_unittest(void)
 	of_unittest_match_node();
 	of_unittest_platform_populate();
 	of_unittest_overlay();
+	of_unittest_lifecycle();
 
 	/* Double check linkage after removing testcase data */
 	of_unittest_check_tree_linkage();