@@ -1,3 +1,3 @@
obj-$(CONFIG_SECURITY_LANDLOCK) := landlock.o
-landlock-y := object.o
+landlock-y := object.o ruleset.o
new file mode 100644
@@ -0,0 +1,361 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Landlock LSM - Ruleset management
+ *
+ * Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net>
+ * Copyright © 2018-2020 ANSSI
+ */
+
+#include <linux/bits.h>
+#include <linux/bug.h>
+#include <linux/compiler_types.h>
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/limits.h>
+#include <linux/lockdep.h>
+#include <linux/rbtree.h>
+#include <linux/refcount.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/workqueue.h>
+
+#include "object.h"
+#include "ruleset.h"
+
+static struct landlock_ruleset *create_ruleset(void)
+{
+ struct landlock_ruleset *new_ruleset;
+
+ new_ruleset = kzalloc(sizeof(*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->root = RB_ROOT;
+ /*
+ * hierarchy = NULL
+ * nb_rules = 0
+ * nb_layers = 0
+ * fs_access_mask = 0
+ */
+ return new_ruleset;
+}
+
+struct landlock_ruleset *landlock_create_ruleset(const u32 fs_access_mask)
+{
+ struct landlock_ruleset *new_ruleset;
+
+ /* Informs about useless ruleset. */
+ if (!fs_access_mask)
+ return ERR_PTR(-ENOMSG);
+ new_ruleset = create_ruleset();
+ if (!IS_ERR(new_ruleset))
+ new_ruleset->fs_access_mask = fs_access_mask;
+ return new_ruleset;
+}
+
+static struct landlock_rule *duplicate_rule(struct landlock_rule *const src)
+{
+ struct landlock_rule *new_rule;
+
+ new_rule = kzalloc(sizeof(*new_rule), GFP_KERNEL_ACCOUNT);
+ if (!new_rule)
+ return ERR_PTR(-ENOMEM);
+ RB_CLEAR_NODE(&new_rule->node);
+ landlock_get_object(src->object);
+ new_rule->object = src->object;
+ new_rule->access = src->access;
+ new_rule->layers = src->layers;
+ return new_rule;
+}
+
+static void put_rule(struct landlock_rule *const rule)
+{
+ might_sleep();
+ if (!rule)
+ return;
+ landlock_put_object(rule->object);
+ kfree(rule);
+}
+
+/**
+ * insert_rule - Insert a rule in a ruleset
+ *
+ * Intersects access rights of the rule with those of the ruleset.
+ *
+ * @ruleset: The ruleset to be updated.
+ * @rule: Read-only payload to be inserted (not owned by this function).
+ * @is_merge: If true, handle the rule layers.
+ *
+ * Assumptions:
+ *
+ * - An inserted rule cannot be removed.
+ * - The underlying kernel object must be held by the caller.
+ */
+static int insert_rule(struct landlock_ruleset *const ruleset,
+ struct landlock_rule *const rule, const bool is_merge)
+{
+ struct rb_node **walker_node;
+ struct rb_node *parent_node = NULL;
+ struct landlock_rule *new_rule;
+
+ might_sleep();
+ lockdep_assert_held(&ruleset->lock);
+ if (WARN_ON_ONCE(!rule->object))
+ return -ENOENT;
+ if (!is_merge && WARN_ON_ONCE(ruleset->nb_layers != 0))
+ return -EINVAL;
+ walker_node = &(ruleset->root.rb_node);
+ while (*walker_node) {
+ struct landlock_rule *const this = rb_entry(*walker_node,
+ struct landlock_rule, node);
+
+ if (this->object != rule->object) {
+ parent_node = *walker_node;
+ if (this->object < rule->object)
+ walker_node = &((*walker_node)->rb_right);
+ else
+ walker_node = &((*walker_node)->rb_left);
+ continue;
+ }
+
+ /* If there is a matching rule, updates it. */
+ if (is_merge)
+ /* Updates the rule layers with the next one. */
+ this->layers |= BIT_ULL(ruleset->nb_layers);
+ /* Intersects access rights. */
+ this->access &= rule->access;
+ return 0;
+ }
+
+ /* There is no match for @rule->object. */
+ if (ruleset->nb_rules == U32_MAX)
+ return -E2BIG;
+ new_rule = duplicate_rule(rule);
+ if (IS_ERR(new_rule))
+ return PTR_ERR(new_rule);
+ if (is_merge)
+ /* Sets the rule layer to the next one. */
+ new_rule->layers = BIT_ULL(ruleset->nb_layers);
+ rb_link_node(&new_rule->node, parent_node, walker_node);
+ rb_insert_color(&new_rule->node, &ruleset->root);
+ ruleset->nb_rules++;
+ return 0;
+}
+
+int landlock_insert_rule(struct landlock_ruleset *const ruleset,
+ struct landlock_rule *const rule)
+{
+ return insert_rule(ruleset, rule, false);
+}
+
+static inline 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_ruleset(struct landlock_ruleset *const dst,
+ struct landlock_ruleset *const src)
+{
+ struct landlock_rule *walker_rule, *next_rule;
+ int err = 0;
+
+ might_sleep();
+ if (!src)
+ return 0;
+ /* Only merge into a domain. */
+ if (WARN_ON_ONCE(!dst || !dst->hierarchy))
+ return -EFAULT;
+
+ /*
+ * The ruleset being modified (@dst) is locked first, then the ruleset
+ * being copied (@src).
+ */
+ mutex_lock(&dst->lock);
+ mutex_lock_nested(&src->lock, SINGLE_DEPTH_NESTING);
+ /*
+ * Makes a new layer, but only increments the number of layers after
+ * the rules are inserted.
+ */
+ if (dst->nb_layers == (sizeof(walker_rule->layers) * BITS_PER_BYTE)) {
+ err = -E2BIG;
+ goto out_unlock;
+ }
+ dst->fs_access_mask |= src->fs_access_mask;
+
+ /* Merges the @src tree. */
+ rbtree_postorder_for_each_entry_safe(walker_rule, next_rule,
+ &src->root, node) {
+ err = insert_rule(dst, walker_rule, true);
+ if (err)
+ goto out_unlock;
+ }
+ dst->nb_layers++;
+
+out_unlock:
+ mutex_unlock(&src->lock);
+ mutex_unlock(&dst->lock);
+ return err;
+}
+
+static struct landlock_ruleset *inherit_ruleset(
+ struct landlock_ruleset *const parent)
+{
+ struct landlock_rule *walker_rule, *next_rule;
+ struct landlock_ruleset *new_ruleset;
+ int err = 0;
+
+ might_sleep();
+ new_ruleset = create_ruleset();
+ if (IS_ERR(new_ruleset))
+ return new_ruleset;
+
+ new_ruleset->hierarchy = kzalloc(sizeof(*new_ruleset->hierarchy),
+ GFP_KERNEL_ACCOUNT);
+ if (!new_ruleset->hierarchy) {
+ err = -ENOMEM;
+ goto out_put_ruleset;
+ }
+ refcount_set(&new_ruleset->hierarchy->usage, 1);
+ if (!parent)
+ return new_ruleset;
+
+ mutex_lock(&new_ruleset->lock);
+ mutex_lock_nested(&parent->lock, SINGLE_DEPTH_NESTING);
+
+ /* Copies the @parent tree. */
+ rbtree_postorder_for_each_entry_safe(walker_rule, next_rule,
+ &parent->root, node) {
+ err = landlock_insert_rule(new_ruleset, walker_rule);
+ if (err)
+ goto out_unlock;
+ }
+ new_ruleset->nb_layers = parent->nb_layers;
+ new_ruleset->fs_access_mask = parent->fs_access_mask;
+ WARN_ON_ONCE(!parent->hierarchy);
+ get_hierarchy(parent->hierarchy);
+ new_ruleset->hierarchy->parent = parent->hierarchy;
+
+ mutex_unlock(&parent->lock);
+ mutex_unlock(&new_ruleset->lock);
+ return new_ruleset;
+
+out_unlock:
+ mutex_unlock(&parent->lock);
+ mutex_unlock(&new_ruleset->lock);
+
+out_put_ruleset:
+ landlock_put_ruleset(new_ruleset);
+ return ERR_PTR(err);
+}
+
+static void free_ruleset(struct landlock_ruleset *const ruleset)
+{
+ struct landlock_rule *freeme, *next;
+
+ might_sleep();
+ rbtree_postorder_for_each_entry_safe(freeme, next, &ruleset->root,
+ node)
+ put_rule(freeme);
+ put_hierarchy(ruleset->hierarchy);
+ kfree(ruleset);
+}
+
+void landlock_put_ruleset(struct landlock_ruleset *const ruleset)
+{
+ might_sleep();
+ if (ruleset && refcount_dec_and_test(&ruleset->usage))
+ free_ruleset(ruleset);
+}
+
+static void free_ruleset_work(struct work_struct *const work)
+{
+ struct landlock_ruleset *ruleset;
+
+ ruleset = container_of(work, struct landlock_ruleset, work_free);
+ free_ruleset(ruleset);
+}
+
+void landlock_put_ruleset_deferred(struct landlock_ruleset *const ruleset)
+{
+ if (ruleset && refcount_dec_and_test(&ruleset->usage)) {
+ INIT_WORK(&ruleset->work_free, free_ruleset_work);
+ schedule_work(&ruleset->work_free);
+ }
+}
+
+/**
+ * landlock_merge_ruleset - Merge a ruleset with a domain
+ *
+ * @parent: Parent domain.
+ * @ruleset: New ruleset to be merged.
+ *
+ * Returns the intersection of @parent and @ruleset, or returns @parent if
+ * @ruleset is empty, or returns a duplicate of @ruleset if @parent is empty.
+ */
+struct landlock_ruleset *landlock_merge_ruleset(
+ struct landlock_ruleset *const parent,
+ struct landlock_ruleset *const ruleset)
+{
+ struct landlock_ruleset *new_dom;
+ int err;
+
+ might_sleep();
+ /*
+ * Merging duplicates a ruleset, so a new ruleset cannot be
+ * the same as the parent, but they can have similar content.
+ */
+ if (WARN_ON_ONCE(!ruleset || parent == ruleset)) {
+ landlock_get_ruleset(parent);
+ return parent;
+ }
+
+ new_dom = inherit_ruleset(parent);
+ if (IS_ERR(new_dom))
+ return new_dom;
+
+ err = merge_ruleset(new_dom, ruleset);
+ if (err) {
+ landlock_put_ruleset(new_dom);
+ return ERR_PTR(err);
+ }
+ return new_dom;
+}
+
+/*
+ * The returned access has the same lifetime as @ruleset.
+ */
+const struct landlock_rule *landlock_find_rule(
+ const struct landlock_ruleset *const ruleset,
+ const struct landlock_object *const object)
+{
+ const struct rb_node *node;
+
+ if (!object)
+ return NULL;
+ node = ruleset->root.rb_node;
+ while (node) {
+ struct landlock_rule *this = rb_entry(node,
+ struct landlock_rule, node);
+
+ if (this->object == object)
+ return this;
+ if (this->object < object)
+ node = node->rb_right;
+ else
+ node = node->rb_left;
+ }
+ return NULL;
+}
new file mode 100644
@@ -0,0 +1,158 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Landlock LSM - Ruleset management
+ *
+ * Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net>
+ * Copyright © 2018-2020 ANSSI
+ */
+
+#ifndef _SECURITY_LANDLOCK_RULESET_H
+#define _SECURITY_LANDLOCK_RULESET_H
+
+#include <linux/mutex.h>
+#include <linux/rbtree.h>
+#include <linux/refcount.h>
+#include <linux/workqueue.h>
+
+#include "object.h"
+
+/**
+ * struct landlock_rule - Access rights tied to an object
+ *
+ * When enforcing a ruleset (i.e. merging a ruleset into the current domain),
+ * the layer level of a new rule is the incremented top layer level (cf.
+ * &struct landlock_ruleset). If there is no rule (from this domain) tied to
+ * the same object, then the depth of the new rule is 1. However, if there is
+ * already a rule tied to the same object and if this rule's layer level is the
+ * previous top layer level, then the depth and the layer level are both
+ * incremented and the rule is updated with the new access rights (boolean
+ * AND).
+ */
+struct landlock_rule {
+ /**
+ * @node: Node in the ruleset's red-black tree.
+ */
+ struct rb_node node;
+ /**
+ * @object: Pointer to identify a kernel object (e.g. an inode). This
+ * is used as a key for this ruleset element. This pointer is set once
+ * and never modified. It always points to an allocated object because
+ * each rule increments the refcount of its object.
+ */
+ struct landlock_object *object;
+ /**
+ * @layers: Bitfield to identify the layers which resulted to @access
+ * from different consecutive intersections.
+ */
+ u64 layers;
+ /**
+ * @access: Bitfield of allowed actions on the kernel object. They are
+ * relative to the object type (e.g. %LANDLOCK_ACTION_FS_READ). This
+ * may be the result of the merged access rights (boolean AND) from
+ * multiple layers referring to the same object.
+ */
+ u32 access;
+};
+
+/**
+ * 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
+ *
+ * This data structure must contain unique entries, be updatable, and quick to
+ * match an object.
+ */
+struct landlock_ruleset {
+ /**
+ * @root: Root of a red-black tree containing &struct landlock_rule
+ * nodes. Once a ruleset is tied to a process (i.e. as a domain), this
+ * tree is immutable until @usage reaches zero.
+ */
+ struct rb_root root;
+ /**
+ * @hierarchy: Enables hierarchy identification even when a parent
+ * domain vanishes. This is needed for the ptrace protection.
+ */
+ struct landlock_hierarchy *hierarchy;
+ union {
+ /**
+ * @work_free: Enables to free a ruleset within a lockless
+ * section. This is only used by
+ * landlock_put_ruleset_deferred() when @usage reaches zero.
+ * The fields @lock, @usage, @nb_layers, @nb_rules and
+ * @fs_access_mask are then unused.
+ */
+ struct work_struct work_free;
+ struct {
+ /**
+ * @lock: Guards against concurrent modifications of
+ * @root, if @usage is greater than zero.
+ */
+ struct mutex lock;
+ /**
+ * @usage: Number of processes (i.e. domains) or file
+ * descriptors referencing this ruleset.
+ */
+ refcount_t usage;
+ /**
+ * @nb_rules: Number of non-overlapping (i.e. not for
+ * the same object) rules in this ruleset.
+ */
+ u32 nb_rules;
+ /**
+ * @nb_layers: Number of layers which are used in this
+ * ruleset. This enables to check that all the layers
+ * allow an access request. A value of 0 identifies a
+ * non-merged ruleset (i.e. not a domain).
+ */
+ u32 nb_layers;
+ /**
+ * @fs_access_mask: Contains the subset of filesystem
+ * actions which are restricted by a ruleset. This is
+ * used when merging rulesets and for user space
+ * backward compatibility (i.e. future-proof). Set
+ * once and never changed for the lifetime of the
+ * ruleset.
+ */
+ u32 fs_access_mask;
+ };
+ };
+};
+
+struct landlock_ruleset *landlock_create_ruleset(const u32 fs_access_mask);
+
+void landlock_put_ruleset(struct landlock_ruleset *const ruleset);
+void landlock_put_ruleset_deferred(struct landlock_ruleset *const ruleset);
+
+int landlock_insert_rule(struct landlock_ruleset *const ruleset,
+ struct landlock_rule *const rule);
+
+struct landlock_ruleset *landlock_merge_ruleset(
+ struct landlock_ruleset *const parent,
+ struct landlock_ruleset *const ruleset);
+
+const struct landlock_rule *landlock_find_rule(
+ const struct landlock_ruleset *const ruleset,
+ const struct landlock_object *const object);
+
+static inline void landlock_get_ruleset(struct landlock_ruleset *const ruleset)
+{
+ if (ruleset)
+ refcount_inc(&ruleset->usage);
+}
+
+#endif /* _SECURITY_LANDLOCK_RULESET_H */