[PATCH v4 07/30] landlock: Move domain hierarchy management and export helpers

["Mickaël Salaün" <mic@digikod.net>]

Create a new domain.h file containing the struct landlock_hierarchy
definition and helpers.  This type will grow with audit support.  This
also prepares for a new domain type.

Export landlock_get_hierarchy() and landlock_put_hierarchy() that will
be used by audit in a following commit.

Clean up Makefile entries.

Cc: Günther Noack <gnoack@google.com>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Link: https://lore.kernel.org/r/20250108154338.1129069-8-mic@digikod.net
---

Changes since v3:
- Export landlock_get_hierarchy() and landlock_put_hierarchy().
- Clean up Makefile entries.

Changes since v1:
- New patch.
---
 MAINTAINERS                 |  1 +
 include/linux/landlock.h    | 31 +++++++++++++++++++++++++++++++
 security/landlock/Makefile  | 11 +++++++++--
 security/landlock/domain.c  | 29 +++++++++++++++++++++++++++++
 security/landlock/domain.h  | 31 +++++++++++++++++++++++++++++++
 security/landlock/ruleset.c | 22 ++++------------------
 security/landlock/ruleset.h | 17 +----------------
 security/landlock/task.c    |  1 +
 8 files changed, 107 insertions(+), 36 deletions(-)
 create mode 100644 include/linux/landlock.h
 create mode 100644 security/landlock/domain.c
 create mode 100644 security/landlock/domain.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 30cbc3d44cd5..425676b25a4f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -12961,6 +12961,7 @@ T:	git https://git.kernel.org/pub/scm/linux/kernel/git/mic/linux.git
 F:	Documentation/security/landlock.rst
 F:	Documentation/userspace-api/landlock.rst
 F:	fs/ioctl.c
+F:	include/linux/landlock.h
 F:	include/uapi/linux/landlock.h
 F:	samples/landlock/
 F:	security/landlock/
diff --git a/include/linux/landlock.h b/include/linux/landlock.h
new file mode 100644
index 000000000000..8491142658a1
--- /dev/null
+++ b/include/linux/landlock.h
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Landlock - Kernel API
+ *
+ * Copyright © 2024-2025 Microsoft Corporation
+ */
+
+#ifndef _LINUX_LANDLOCK_H
+#define _LINUX_LANDLOCK_H
+
+struct landlock_hierarchy;
+
+#ifdef CONFIG_SECURITY_LANDLOCK
+
+void landlock_get_hierarchy(struct landlock_hierarchy *hierarchy);
+
+void landlock_put_hierarchy(struct landlock_hierarchy *hierarchy);
+
+#else /* CONFIG_SECURITY_LANDLOCK */
+
+static inline void landlock_get_hierarchy(struct landlock_hierarchy *hierarchy)
+{
+}
+
+static inline void landlock_put_hierarchy(struct landlock_hierarchy *hierarchy)
+{
+}
+
+#endif /* CONFIG_SECURITY_LANDLOCK */
+
+#endif /* _LINUX_LANDLOCK_H */
diff --git a/security/landlock/Makefile b/security/landlock/Makefile
index e1777abbc413..51815908a464 100644
--- a/security/landlock/Makefile
+++ b/security/landlock/Makefile
@@ -1,7 +1,14 @@
 obj-$(CONFIG_SECURITY_LANDLOCK) := landlock.o
 
-landlock-y := setup.o syscalls.o object.o ruleset.o \
-	cred.o task.o fs.o
+landlock-y := \
+	setup.o \
+	syscalls.o \
+	object.o \
+	ruleset.o \
+	cred.o \
+	task.o \
+	fs.o \
+	domain.o
 
 landlock-$(CONFIG_INET) += net.o
 
diff --git a/security/landlock/domain.c b/security/landlock/domain.c
new file mode 100644
index 000000000000..df58638ffc50
--- /dev/null
+++ b/security/landlock/domain.c
@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Landlock LSM - Domain management
+ *
+ * Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net>
+ * Copyright © 2018-2020 ANSSI
+ * Copyright © 2024-2025 Microsoft Corporation
+ */
+
+#include <linux/landlock.h>
+#include <linux/mm.h>
+
+#include "domain.h"
+
+void landlock_get_hierarchy(struct landlock_hierarchy *const hierarchy)
+{
+	if (hierarchy)
+		refcount_inc(&hierarchy->usage);
+}
+
+void landlock_put_hierarchy(struct landlock_hierarchy *hierarchy)
+{
+	while (hierarchy && refcount_dec_and_test(&hierarchy->usage)) {
+		const struct landlock_hierarchy *const freeme = hierarchy;
+
+		hierarchy = hierarchy->parent;
+		kfree(freeme);
+	}
+}
diff --git a/security/landlock/domain.h b/security/landlock/domain.h
new file mode 100644
index 000000000000..2e612ef754e3
--- /dev/null
+++ b/security/landlock/domain.h
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Landlock LSM - Domain management
+ *
+ * Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net>
+ * Copyright © 2018-2020 ANSSI
+ */
+
+#ifndef _SECURITY_LANDLOCK_DOMAIN_H
+#define _SECURITY_LANDLOCK_DOMAIN_H
+
+#include <linux/landlock.h>
+#include <linux/refcount.h>
+
+/**
+ * struct landlock_hierarchy - Node in a domain hierarchy
+ */
+struct landlock_hierarchy {
+	/**
+	 * @parent: Pointer to the parent node, or NULL if it is a root
+	 * Landlock domain.
+	 */
+	struct landlock_hierarchy *parent;
+	/**
+	 * @usage: Number of potential children domains plus their parent
+	 * domain.
+	 */
+	refcount_t usage;
+};
+
+#endif /* _SECURITY_LANDLOCK_DOMAIN_H */
diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
index dbc528f5f3b7..8b47af69af3e 100644
--- a/security/landlock/ruleset.c
+++ b/security/landlock/ruleset.c
@@ -12,6 +12,7 @@
 #include <linux/err.h>
 #include <linux/errno.h>
 #include <linux/kernel.h>
+#include <linux/landlock.h>
 #include <linux/lockdep.h>
 #include <linux/overflow.h>
 #include <linux/rbtree.h>
@@ -21,6 +22,7 @@
 #include <linux/workqueue.h>
 
 #include "access.h"
+#include "domain.h"
 #include "limits.h"
 #include "object.h"
 #include "ruleset.h"
@@ -305,22 +307,6 @@ int landlock_insert_rule(struct landlock_ruleset *const ruleset,
 	return insert_rule(ruleset, id, &layers, ARRAY_SIZE(layers));
 }
 
-static void get_hierarchy(struct landlock_hierarchy *const hierarchy)
-{
-	if (hierarchy)
-		refcount_inc(&hierarchy->usage);
-}
-
-static void put_hierarchy(struct landlock_hierarchy *hierarchy)
-{
-	while (hierarchy && refcount_dec_and_test(&hierarchy->usage)) {
-		const struct landlock_hierarchy *const freeme = hierarchy;
-
-		hierarchy = hierarchy->parent;
-		kfree(freeme);
-	}
-}
-
 static int merge_tree(struct landlock_ruleset *const dst,
 		      struct landlock_ruleset *const src,
 		      const enum landlock_key_type key_type)
@@ -475,7 +461,7 @@ static int inherit_ruleset(struct landlock_ruleset *const parent,
 		err = -EINVAL;
 		goto out_unlock;
 	}
-	get_hierarchy(parent->hierarchy);
+	landlock_get_hierarchy(parent->hierarchy);
 	child->hierarchy->parent = parent->hierarchy;
 
 out_unlock:
@@ -499,7 +485,7 @@ static void free_ruleset(struct landlock_ruleset *const ruleset)
 		free_rule(freeme, LANDLOCK_KEY_NET_PORT);
 #endif /* IS_ENABLED(CONFIG_INET) */
 
-	put_hierarchy(ruleset->hierarchy);
+	landlock_put_hierarchy(ruleset->hierarchy);
 	kfree(ruleset);
 }
 
diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
index 2f29b9f40392..39169b6860e3 100644
--- a/security/landlock/ruleset.h
+++ b/security/landlock/ruleset.h
@@ -15,6 +15,7 @@
 #include <linux/workqueue.h>
 
 #include "access.h"
+#include "domain.h"
 #include "limits.h"
 #include "object.h"
 
@@ -106,22 +107,6 @@ struct landlock_rule {
 	struct landlock_layer layers[] __counted_by(num_layers);
 };
 
-/**
- * struct landlock_hierarchy - Node in a ruleset hierarchy
- */
-struct landlock_hierarchy {
-	/**
-	 * @parent: Pointer to the parent node, or NULL if it is a root
-	 * Landlock domain.
-	 */
-	struct landlock_hierarchy *parent;
-	/**
-	 * @usage: Number of potential children domains plus their parent
-	 * domain.
-	 */
-	refcount_t usage;
-};
-
 /**
  * struct landlock_ruleset - Landlock ruleset
  *
diff --git a/security/landlock/task.c b/security/landlock/task.c
index dc7dab78392e..98894ad1abc7 100644
--- a/security/landlock/task.c
+++ b/security/landlock/task.c
@@ -18,6 +18,7 @@
 
 #include "common.h"
 #include "cred.h"
+#include "domain.h"
 #include "fs.h"
 #include "ruleset.h"
 #include "setup.h"
-- 
2.47.1