[PATCH v4 5/5] landlock: Implement KUnit test for LANDLOCK_ADD_RULE_NO_INHERIT

[Justin Suess <utilityemal77@gmail.com>]

Add a unit test for rule_flag collection, ensuring that access masks
are properly propagated with the flags.

No changes in v4.

changes v2..v3:

   * Removing erroneously misplaced code and placed in the proper
     patch.

Signed-off-by: Justin Suess <utilityemal77@gmail.com>
---
 security/landlock/ruleset.c | 89 +++++++++++++++++++++++++++++++++++++
 1 file changed, 89 insertions(+)

diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
index 9152a939d79a..8064139fde8f 100644
--- a/security/landlock/ruleset.c
+++ b/security/landlock/ruleset.c
@@ -22,6 +22,7 @@
 #include <linux/spinlock.h>
 #include <linux/workqueue.h>
 #include <uapi/linux/landlock.h>
+#include <kunit/test.h>
 
 #include "access.h"
 #include "audit.h"
@@ -770,3 +771,91 @@ landlock_init_layer_masks(const struct landlock_ruleset *const domain,
 	}
 	return handled_accesses;
 }
+
+#ifdef CONFIG_SECURITY_LANDLOCK_KUNIT_TEST
+
+/**
+ * test_unmask_layers_no_inherit - Test landlock_unmask_layers() with no_inherit
+ * @test: The KUnit test context.
+ */
+static void test_unmask_layers_no_inherit(struct kunit *const test)
+{
+	struct landlock_rule *rule;
+	layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS];
+	struct collected_rule_flags rule_flags;
+	const access_mask_t access_request = BIT_ULL(0) | BIT_ULL(1);
+	const layer_mask_t layers_initialized = BIT_ULL(0) | BIT_ULL(1);
+	size_t i;
+
+	rule = kzalloc(struct_size(rule, layers, 2), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_NULL(test, rule);
+
+	rule->num_layers = 2;
+
+	/* Layer 1: allows access 0, no_inherit */
+	rule->layers[0].level = 1;
+	rule->layers[0].access = BIT_ULL(0);
+	rule->layers[0].flags.no_inherit = 1;
+
+	/* Layer 2: allows access 1 */
+	rule->layers[1].level = 2;
+	rule->layers[1].access = BIT_ULL(1);
+
+	/* Case 1: No rule_flags provided (should behave normally) */
+	for (i = 0; i < ARRAY_SIZE(layer_masks); i++)
+		layer_masks[i] = layers_initialized;
+
+	landlock_unmask_layers(rule, access_request, &layer_masks,
+			       ARRAY_SIZE(layer_masks), NULL);
+
+	/* Access 0 should be unmasked by layer 1 */
+	KUNIT_EXPECT_EQ(test, layer_masks[0], layers_initialized & ~BIT_ULL(0));
+	/* Access 1 should be unmasked by layer 2 */
+	KUNIT_EXPECT_EQ(test, layer_masks[1], layers_initialized & ~BIT_ULL(1));
+
+	/* Case 2: rule_flags provided, no existing no_inherit_masks */
+	for (i = 0; i < ARRAY_SIZE(layer_masks); i++)
+		layer_masks[i] = layers_initialized;
+	memset(&rule_flags, 0, sizeof(rule_flags));
+
+	landlock_unmask_layers(rule, access_request, &layer_masks,
+			       ARRAY_SIZE(layer_masks), &rule_flags);
+
+	/* Access 0 should be unmasked by layer 1 */
+	KUNIT_EXPECT_EQ(test, layer_masks[0], layers_initialized & ~BIT_ULL(0));
+	/* Access 1 should be unmasked by layer 2 */
+	KUNIT_EXPECT_EQ(test, layer_masks[1], layers_initialized & ~BIT_ULL(1));
+
+	/* rule_flags should collect no_inherit from layer 1 */
+	KUNIT_EXPECT_EQ(test, rule_flags.no_inherit_masks, (layer_mask_t)BIT_ULL(0));
+
+	/* Case 3: rule_flags provided, layer 1 is masked by no_inherit_masks */
+	for (i = 0; i < ARRAY_SIZE(layer_masks); i++)
+		layer_masks[i] = layers_initialized;
+	memset(&rule_flags, 0, sizeof(rule_flags));
+	rule_flags.no_inherit_masks = BIT_ULL(0); /* Mask layer 1 */
+
+	landlock_unmask_layers(rule, access_request, &layer_masks,
+			       ARRAY_SIZE(layer_masks), &rule_flags);
+
+	/* Access 0 should NOT be unmasked by layer 1 because it is skipped */
+	KUNIT_EXPECT_EQ(test, layer_masks[0], layers_initialized);
+	/* Access 1 should be unmasked by layer 2 */
+	KUNIT_EXPECT_EQ(test, layer_masks[1], layers_initialized & ~BIT_ULL(1));
+
+	kfree(rule);
+}
+
+static struct kunit_case ruleset_test_cases[] = {
+	KUNIT_CASE(test_unmask_layers_no_inherit),
+	{}
+};
+
+static struct kunit_suite ruleset_test_suite = {
+	.name = "landlock_ruleset",
+	.test_cases = ruleset_test_cases,
+};
+
+kunit_test_suite(ruleset_test_suite);
+
+#endif /* CONFIG_SECURITY_LANDLOCK_KUNIT_TEST */
-- 
2.51.0