1 files changed, 354 insertions, 0 deletions
diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
new file mode 100644
index 000000000..0d0770752
--- /dev/null
+++ b/security/landlock/ruleset.c
@@ -0,0 +1,354 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Landlock LSM - Ruleset management
+ *
+ * Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net>
+ * Copyright © 2018-2020 ANSSI
+ * Copyright © 2026 Cloudflare, Inc.
+ */
+
+#include <linux/bits.h>
+#include <linux/bug.h>
+#include <linux/cleanup.h>
+#include <linux/compiler_types.h>
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/lockdep.h>
+#include <linux/mutex.h>
+#include <linux/overflow.h>
+#include <linux/rbtree.h>
+#include <linux/refcount.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <uapi/linux/landlock.h>
+
+#include "access.h"
+#include "id.h"
+#include "limits.h"
+#include "object.h"
+#include "ruleset.h"
+
+#include <trace/events/landlock.h>
+
+struct landlock_ruleset *
+landlock_create_ruleset(const access_mask_t fs_access_mask,
+			const access_mask_t net_access_mask,
+			const access_mask_t scope_mask)
+{
+	struct landlock_ruleset *new_ruleset;
+
+	/* Informs about useless ruleset. */
+	if (!fs_access_mask && !net_access_mask && !scope_mask)
+		return ERR_PTR(-ENOMSG);
+
+	new_ruleset = kzalloc_obj(*new_ruleset, GFP_KERNEL_ACCOUNT);
+	if (!new_ruleset)
+		return ERR_PTR(-ENOMEM);
+
+	refcount_set(&new_ruleset->usage, 1);
+	mutex_init(&new_ruleset->lock);
+	new_ruleset->rules.root_inode = RB_ROOT;
+
+#if IS_ENABLED(CONFIG_INET)
+	new_ruleset->rules.root_net_port = RB_ROOT;
+#endif /* IS_ENABLED(CONFIG_INET) */
+
+#ifdef CONFIG_TRACEPOINTS
+	new_ruleset->id = landlock_get_id_range(1);
+#endif /* CONFIG_TRACEPOINTS */
+
+	/* Should already be checked in landlock_create_ruleset(). */
+	if (fs_access_mask) {
+		const access_mask_t mask = fs_access_mask &
+					   LANDLOCK_MASK_ACCESS_FS;
+
+		WARN_ON_ONCE(fs_access_mask != mask);
+		new_ruleset->handled_masks.fs |= mask;
+	}
+	if (net_access_mask) {
+		const access_mask_t mask = net_access_mask &
+					   LANDLOCK_MASK_ACCESS_NET;
+
+		WARN_ON_ONCE(net_access_mask != mask);
+		new_ruleset->handled_masks.net |= mask;
+	}
+	if (scope_mask) {
+		const access_mask_t mask = scope_mask & LANDLOCK_MASK_SCOPE;
+
+		WARN_ON_ONCE(scope_mask != mask);
+		new_ruleset->handled_masks.scope |= mask;
+	}
+	return new_ruleset;
+}
+
+static void build_check_rule(void)
+{
+	const struct landlock_rule rule = {
+		.num_layers = ~0,
+	};
+
+	/*
+	 * Checks that .num_layers is large enough for at least
+	 * LANDLOCK_MAX_NUM_LAYERS layers.
+	 */
+	BUILD_BUG_ON(rule.num_layers < LANDLOCK_MAX_NUM_LAYERS);
+}
+
+static bool is_object_pointer(const enum landlock_key_type key_type)
+{
+	switch (key_type) {
+	case LANDLOCK_KEY_INODE:
+		return true;
+
+#if IS_ENABLED(CONFIG_INET)
+	case LANDLOCK_KEY_NET_PORT:
+		return false;
+#endif /* IS_ENABLED(CONFIG_INET) */
+
+	default:
+		WARN_ON_ONCE(1);
+		return false;
+	}
+}
+
+static struct landlock_rule *
+create_rule(const struct landlock_id id,
+	    const struct landlock_layer (*layers)[], const u32 num_layers,
+	    const struct landlock_layer *const new_layer)
+{
+	struct landlock_rule *new_rule;
+	u32 new_num_layers;
+
+	build_check_rule();
+	if (new_layer) {
+		/* Should already be checked by landlock_merge_ruleset(). */
+		if (WARN_ON_ONCE(num_layers >= LANDLOCK_MAX_NUM_LAYERS))
+			return ERR_PTR(-E2BIG);
+		new_num_layers = num_layers + 1;
+	} else {
+		new_num_layers = num_layers;
+	}
+	new_rule = kzalloc_flex(*new_rule, layers, new_num_layers,
+				GFP_KERNEL_ACCOUNT);
+	if (!new_rule)
+		return ERR_PTR(-ENOMEM);
+	RB_CLEAR_NODE(&new_rule->node);
+	if (is_object_pointer(id.type)) {
+		/* This should have been caught by landlock_store_rule(). */
+		WARN_ON_ONCE(!id.key.object);
+		landlock_get_object(id.key.object);
+	}
+
+	new_rule->key = id.key;
+	new_rule->num_layers = new_num_layers;
+	/* Copies the original layer stack. */
+	memcpy(new_rule->layers, layers,
+	       flex_array_size(new_rule, layers, num_layers));
+	if (new_layer)
+		/* Adds a copy of @new_layer on the layer stack. */
+		new_rule->layers[new_rule->num_layers - 1] = *new_layer;
+	return new_rule;
+}
+
+static void free_rule(struct landlock_rule *const rule,
+		      const enum landlock_key_type key_type)
+{
+	might_sleep();
+	if (!rule)
+		return;
+	if (is_object_pointer(key_type))
+		landlock_put_object(rule->key.object);
+	kfree(rule);
+}
+
+static void build_check_ruleset(void)
+{
+	const struct landlock_rules rules = {
+		.num_rules = ~0,
+	};
+
+	BUILD_BUG_ON(rules.num_rules < LANDLOCK_MAX_NUM_RULES);
+}
+
+/**
+ * landlock_store_rule - Create and insert a rule into the rule storage
+ *
+ * @rules: The rule storage to be updated.  The caller is responsible for
+ *         any required locking.  For rulesets, this means holding
+ *         &landlock_ruleset.lock.  For domains under construction, no lock is
+ *         needed because the domain is not yet visible to other tasks.
+ * @id: The ID to build the new rule with.  The underlying kernel object, if
+ *      any, must be held by the caller.
+ * @layers: One or multiple layers to be copied into the new rule.
+ * @num_layers: The number of @layers entries.
+ *
+ * When user space requests to add a new rule to a ruleset, @layers only
+ * contains one entry and this entry is not assigned to any level.  In this
+ * case, the new rule will extend @rules, similarly to a boolean OR between
+ * access rights.
+ *
+ * When merging a ruleset in a domain, or copying a domain, @layers will be
+ * added to @rules as new constraints, similarly to a boolean AND between access
+ * rights.
+ *
+ * Return: 0 on success, -errno on failure.
+ */
+int landlock_store_rule(struct landlock_rules *const rules,
+			const struct landlock_id id,
+			const struct landlock_layer (*layers)[],
+			const size_t num_layers)
+{
+	struct rb_node **walker_node;
+	struct rb_node *parent_node = NULL;
+	struct landlock_rule *new_rule;
+	struct rb_root *root;
+
+	might_sleep();
+	if (WARN_ON_ONCE(!layers))
+		return -ENOENT;
+
+	if (is_object_pointer(id.type) && WARN_ON_ONCE(!id.key.object))
+		return -ENOENT;
+
+	root = landlock_get_rule_root(rules, id.type);
+	if (IS_ERR(root))
+		return PTR_ERR(root);
+
+	walker_node = &root->rb_node;
+	while (*walker_node) {
+		struct landlock_rule *const this =
+			rb_entry(*walker_node, struct landlock_rule, node);
+
+		if (this->key.data != id.key.data) {
+			parent_node = *walker_node;
+			if (this->key.data < id.key.data)
+				walker_node = &((*walker_node)->rb_right);
+			else
+				walker_node = &((*walker_node)->rb_left);
+			continue;
+		}
+
+		/* Only a single-level layer should match an existing rule. */
+		if (WARN_ON_ONCE(num_layers != 1))
+			return -EINVAL;
+
+		/* If there is a matching rule, updates it. */
+		if ((*layers)[0].level == 0) {
+			/*
+			 * Extends access rights when the request comes from
+			 * landlock_add_rule(2), i.e. @rules is not a domain.
+			 */
+			if (WARN_ON_ONCE(this->num_layers != 1))
+				return -EINVAL;
+			if (WARN_ON_ONCE(this->layers[0].level != 0))
+				return -EINVAL;
+			this->layers[0].access |= (*layers)[0].access;
+			this->layers[0].flags.quiet |= (*layers)[0].flags.quiet;
+			return 0;
+		}
+
+		if (WARN_ON_ONCE(this->layers[0].level == 0))
+			return -EINVAL;
+
+		/*
+		 * Intersects access rights when it is a merge between a
+		 * ruleset and a domain.
+		 */
+		new_rule = create_rule(id, &this->layers, this->num_layers,
+				       &(*layers)[0]);
+		if (IS_ERR(new_rule))
+			return PTR_ERR(new_rule);
+		rb_replace_node(&this->node, &new_rule->node, root);
+		free_rule(this, id.type);
+		return 0;
+	}
+
+	/* There is no match for @id. */
+	build_check_ruleset();
+	if (rules->num_rules >= LANDLOCK_MAX_NUM_RULES)
+		return -E2BIG;
+	new_rule = create_rule(id, layers, num_layers, NULL);
+	if (IS_ERR(new_rule))
+		return PTR_ERR(new_rule);
+	rb_link_node(&new_rule->node, parent_node, walker_node);
+	rb_insert_color(&new_rule->node, root);
+	rules->num_rules++;
+	return 0;
+}
+
+static void build_check_layer(void)
+{
+	const struct landlock_layer layer = {
+		.level = ~0,
+		.access = ~0,
+	};
+
+	/*
+	 * Checks that .level and .access are large enough to contain their expected
+	 * maximum values.
+	 */
+	BUILD_BUG_ON(layer.level < LANDLOCK_MAX_NUM_LAYERS);
+	BUILD_BUG_ON(layer.access < LANDLOCK_MASK_ACCESS_FS);
+}
+
+/* @ruleset must be locked by the caller. */
+int landlock_insert_rule(struct landlock_ruleset *const ruleset,
+			 const struct landlock_id id,
+			 const access_mask_t access, const u32 flags)
+{
+	struct landlock_layer layers[] = { {
+		.access = access,
+		/*
+		 * When @level is zero, landlock_store_rule() extends @ruleset.
+		 */
+		.level = 0,
+		.flags = {
+			.quiet = !!(flags & LANDLOCK_ADD_RULE_QUIET),
+		},
+	} };
+	int err;
+
+	build_check_layer();
+	lockdep_assert_held(&ruleset->lock);
+	err = landlock_store_rule(&ruleset->rules, id, &layers,
+				  ARRAY_SIZE(layers));
+
+#ifdef CONFIG_TRACEPOINTS
+	if (!err)
+		ruleset->version++;
+#endif /* CONFIG_TRACEPOINTS */
+
+	return err;
+}
+
+void landlock_free_rules(struct landlock_rules *const rules)
+{
+	struct landlock_rule *freeme, *next;
+
+	might_sleep();
+	rbtree_postorder_for_each_entry_safe(freeme, next, &rules->root_inode,
+					     node)
+		free_rule(freeme, LANDLOCK_KEY_INODE);
+
+#if IS_ENABLED(CONFIG_INET)
+	rbtree_postorder_for_each_entry_safe(freeme, next,
+					     &rules->root_net_port, node)
+		free_rule(freeme, LANDLOCK_KEY_NET_PORT);
+#endif /* IS_ENABLED(CONFIG_INET) */
+}
+
+static void free_ruleset(struct landlock_ruleset *const ruleset)
+{
+	might_sleep();
+	trace_landlock_free_ruleset(ruleset);
+	landlock_free_rules(&ruleset->rules);
+	kfree(ruleset);
+}
+
+void landlock_put_ruleset(struct landlock_ruleset *const ruleset)
+{
+	might_sleep();
+	if (ruleset && refcount_dec_and_test(&ruleset->usage))
+		free_ruleset(ruleset);
+}