Re: [RFC PATCH v4 03/15] landlock: landlock_find/insert_rule refactoring

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On 09/03/2022 14:44, Konstantin Meskhidze wrote:
A new object union added to support a socket port
rule type. To support it landlock_insert_rule() and
landlock_find_rule() were refactored. Now adding
or searching a rule in a ruleset depends on a
rule_type argument provided in refactored
functions mentioned above.

Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@xxxxxxxxxx>
---

Changes since v3:
* Split commit.
* Refactoring landlock_insert_rule and landlock_find_rule functions.
* Rename new_ruleset->root_inode.

---
  security/landlock/fs.c      |   5 +-
  security/landlock/ruleset.c | 108 +++++++++++++++++++++++++-----------
  security/landlock/ruleset.h |  26 +++++----
  3 files changed, 94 insertions(+), 45 deletions(-)

diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index 97f5c455f5a7..1497948d754f 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -168,7 +168,7 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
  	if (IS_ERR(object))
  		return PTR_ERR(object);
  	mutex_lock(&ruleset->lock);
-	err = landlock_insert_rule(ruleset, object, access_rights);
+	err = landlock_insert_rule(ruleset, object, 0, access_rights, LANDLOCK_RULE_PATH_BENEATH);

For consistency, please use 80 columns everywhere.

  	mutex_unlock(&ruleset->lock);
  	/*
  	 * No need to check for an error because landlock_insert_rule()
@@ -195,7 +195,8 @@ static inline u64 unmask_layers(
  	inode = d_backing_inode(path->dentry);
  	rcu_read_lock();
  	rule = landlock_find_rule(domain,
-			rcu_dereference(landlock_inode(inode)->object));
+			(uintptr_t)rcu_dereference(landlock_inode(inode)->object),
+			LANDLOCK_RULE_PATH_BENEATH);
  	rcu_read_unlock();
  	if (!rule)
  		return layer_mask;
diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
index a6212b752549..971685c48641 100644
--- a/security/landlock/ruleset.c
+++ b/security/landlock/ruleset.c
@@ -34,7 +34,7 @@ static struct landlock_ruleset *create_ruleset(const u32 num_layers)
  		return ERR_PTR(-ENOMEM);
  	refcount_set(&new_ruleset->usage, 1);
  	mutex_init(&new_ruleset->lock);
-	new_ruleset->root = RB_ROOT;
+	new_ruleset->root_inode = RB_ROOT;
  	new_ruleset->num_layers = num_layers;
  	/*
  	 * hierarchy = NULL
@@ -81,10 +81,12 @@ static void build_check_rule(void)
  }

  static struct landlock_rule *create_rule(
-		struct landlock_object *const object,
+		struct landlock_object *const object_ptr,
+		const uintptr_t object_data,
  		const struct landlock_layer (*const layers)[],
  		const u32 num_layers,
-		const struct landlock_layer *const new_layer)
+		const struct landlock_layer *const new_layer,
+		const u16 rule_type)
  {
  	struct landlock_rule *new_rule;
  	u32 new_num_layers;
@@ -103,8 +105,16 @@ static struct landlock_rule *create_rule(
  	if (!new_rule)
  		return ERR_PTR(-ENOMEM);
  	RB_CLEAR_NODE(&new_rule->node);
-	landlock_get_object(object);
-	new_rule->object = object;
+
+	switch (rule_type) {
+	case LANDLOCK_RULE_PATH_BENEATH:
+		landlock_get_object(object_ptr);
+		new_rule->object.ptr = object_ptr;
+		break;
+	default:
+		return ERR_PTR(-EINVAL);

This would lead to memory leak. You should at least add a WARN_ON_ONCE(1) here, but a proper solution would be to remove the use of rule_type and only rely on object_ptr and object_data values. You can also add a WARN_ON_ONCE(object_ptr && object_data).


+	}
+
  	new_rule->num_layers = new_num_layers;
  	/* Copies the original layer stack. */
  	memcpy(new_rule->layers, layers,
@@ -120,7 +130,7 @@ static void free_rule(struct landlock_rule *const rule)
  	might_sleep();
  	if (!rule)
  		return;
-	landlock_put_object(rule->object);
+	landlock_put_object(rule->object.ptr);
  	kfree(rule);
  }

@@ -156,26 +166,38 @@ static void build_check_ruleset(void)
   * access rights.
   */
  static int insert_rule(struct landlock_ruleset *const ruleset,
-		struct landlock_object *const object,
+		struct landlock_object *const object_ptr,
+		const uintptr_t object_data,
  		const struct landlock_layer (*const layers)[],
-		size_t num_layers)
+		size_t num_layers, u16 rule_type)
  {
  	struct rb_node **walker_node;
  	struct rb_node *parent_node = NULL;
  	struct landlock_rule *new_rule;
+	uintptr_t object;
+	struct rb_root *root;

  	might_sleep();
  	lockdep_assert_held(&ruleset->lock);
-	if (WARN_ON_ONCE(!object || !layers))
-		return -ENOENT;

You can leave this code here.

-	walker_node = &(ruleset->root.rb_node);
+	/* Choose rb_tree structure depending on a rule type */
+	switch (rule_type) {
+	case LANDLOCK_RULE_PATH_BENEATH:
+		if (WARN_ON_ONCE(!object_ptr || !layers))
+			return -ENOENT;
+		object = (uintptr_t)object_ptr;
+		root = &ruleset->root_inode;
+		break;
+	default:
+		return -EINVAL;
+	}
+	walker_node = &root->rb_node;
  	while (*walker_node) {
  		struct landlock_rule *const this = rb_entry(*walker_node,
  				struct landlock_rule, node);

-		if (this->object != object) {
+		if (this->object.data != object) {
  			parent_node = *walker_node;
-			if (this->object < object)
+			if (this->object.data < object)
  				walker_node = &((*walker_node)->rb_right);
  			else
  				walker_node = &((*walker_node)->rb_left);
@@ -207,11 +229,15 @@ static int insert_rule(struct landlock_ruleset *const ruleset,
  		 * Intersects access rights when it is a merge between a
  		 * ruleset and a domain.
  		 */
-		new_rule = create_rule(object, &this->layers, this->num_layers,
-				&(*layers)[0]);
+		switch (rule_type) {
+		case LANDLOCK_RULE_PATH_BENEATH:

Same here and for the following code, you should replace such switch/case with an if (object_ptr).


+			new_rule = create_rule(object_ptr, 0, &this->layers, this->num_layers,
+					       &(*layers)[0], rule_type);
+			break;
+		}
  		if (IS_ERR(new_rule))
  			return PTR_ERR(new_rule);
-		rb_replace_node(&this->node, &new_rule->node, &ruleset->root);
+		rb_replace_node(&this->node, &new_rule->node, &ruleset->root_inode);

Use the root variable here. Same for the following code and patches.


  		free_rule(this);
  		return 0;
  	}
@@ -220,11 +246,15 @@ static int insert_rule(struct landlock_ruleset *const ruleset,
  	build_check_ruleset();
  	if (ruleset->num_rules >= LANDLOCK_MAX_NUM_RULES)
  		return -E2BIG;
-	new_rule = create_rule(object, layers, num_layers, NULL);
+	switch (rule_type) {
+	case LANDLOCK_RULE_PATH_BENEATH:
+		new_rule = create_rule(object_ptr, 0, layers, num_layers, NULL, rule_type);
+		break;
+	}
  	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, &ruleset->root);
+	rb_insert_color(&new_rule->node, &ruleset->root_inode);
  	ruleset->num_rules++;
  	return 0;
  }
@@ -242,7 +272,9 @@ static void build_check_layer(void)

  /* @ruleset must be locked by the caller. */
  int landlock_insert_rule(struct landlock_ruleset *const ruleset,
-		struct landlock_object *const object, const u32 access)
+		struct landlock_object *const object_ptr,
+		const uintptr_t object_data,
+		const u32 access, const u16 rule_type)
  {
  	struct landlock_layer layers[] = {{
  		.access = access,
@@ -251,7 +283,8 @@ int landlock_insert_rule(struct landlock_ruleset *const ruleset,
  	}};

  	build_check_layer();
-	return insert_rule(ruleset, object, &layers, ARRAY_SIZE(layers));
+	return insert_rule(ruleset, object_ptr, object_data, &layers,
+			   ARRAY_SIZE(layers), rule_type);
  }

  static inline void get_hierarchy(struct landlock_hierarchy *const hierarchy)
@@ -297,7 +330,7 @@ static int merge_ruleset(struct landlock_ruleset *const dst,

  	/* Merges the @src tree. */
  	rbtree_postorder_for_each_entry_safe(walker_rule, next_rule,
-			&src->root, node) {
+			&src->root_inode, node) {
  		struct landlock_layer layers[] = {{
  			.level = dst->num_layers,
  		}};
@@ -311,8 +344,8 @@ static int merge_ruleset(struct landlock_ruleset *const dst,
  			goto out_unlock;
  		}
  		layers[0].access = walker_rule->layers[0].access;
-		err = insert_rule(dst, walker_rule->object, &layers,
-				ARRAY_SIZE(layers));
+		err = insert_rule(dst, walker_rule->object.ptr, 0, &layers,
+				ARRAY_SIZE(layers), LANDLOCK_RULE_PATH_BENEATH);
  		if (err)
  			goto out_unlock;
  	}
@@ -323,6 +356,8 @@ static int merge_ruleset(struct landlock_ruleset *const dst,
  	return err;
  }

+
+

Useless lines.


  static int inherit_ruleset(struct landlock_ruleset *const parent,
  		struct landlock_ruleset *const child)
  {
@@ -339,9 +374,10 @@ static int inherit_ruleset(struct landlock_ruleset *const parent,

  	/* Copies the @parent tree. */
  	rbtree_postorder_for_each_entry_safe(walker_rule, next_rule,
-			&parent->root, node) {
-		err = insert_rule(child, walker_rule->object,
-				&walker_rule->layers, walker_rule->num_layers);
+			&parent->root_inode, node) {
+		err = insert_rule(child, walker_rule->object.ptr, 0,
+				&walker_rule->layers, walker_rule->num_layers,
+				LANDLOCK_RULE_PATH_BENEATH);
  		if (err)
  			goto out_unlock;
  	}
@@ -372,7 +408,7 @@ 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,
+	rbtree_postorder_for_each_entry_safe(freeme, next, &ruleset->root_inode,
  			node)
  		free_rule(freeme);
  	put_hierarchy(ruleset->hierarchy);
@@ -465,20 +501,28 @@ struct landlock_ruleset *landlock_merge_ruleset(
   */
  const struct landlock_rule *landlock_find_rule(
  		const struct landlock_ruleset *const ruleset,
-		const struct landlock_object *const object)
+		const uintptr_t object_data, const u16 rule_type)
  {
  	const struct rb_node *node;

-	if (!object)
+	if (!object_data)

object_data can be 0. You need to add a test with such value.

We need to be sure that this change cannot affect the current FS code.


  		return NULL;
-	node = ruleset->root.rb_node;
+
+	switch (rule_type) {
+	case LANDLOCK_RULE_PATH_BENEATH:
+		node = ruleset->root_inode.rb_node;
+		break;
+	default:
+		return ERR_PTR(-EINVAL);

This is a bug. There is no check for such value. You need to check and update all call sites to catch such errors. Same for all new use of ERR_PTR().


+	}
+
  	while (node) {
  		struct landlock_rule *this = rb_entry(node,
  				struct landlock_rule, node);

-		if (this->object == object)
+		if (this->object.data == object_data)
  			return this;
-		if (this->object < object)
+		if (this->object.data < object_data)
  			node = node->rb_right;
  		else
  			node = node->rb_left;
diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
index bc87e5f787f7..088b8d95f653 100644
--- a/security/landlock/ruleset.h
+++ b/security/landlock/ruleset.h
@@ -50,15 +50,17 @@ struct landlock_rule {
  	 */
  	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;
-	/**
-	 * @num_layers: Number of entries in @layers.
+	 * @object: A union to identify either a kernel object (e.g. an inode) or
+	 * a socket port object.

…or a raw data value (e.g. a network socket port).


This is used as a key for this ruleset element.
+	 * This pointer is set once and never modified. It always points to an

s/This pointer/@object.ptr/


+	 * allocated object because each rule increments the refcount of its
+	 * object (for inodes);
  	 */
+	 union {
+		struct landlock_object *ptr;
+		uintptr_t data;
+	 } object;
+
  	u32 num_layers;
  	/**
  	 * @layers: Stack of layers, from the latest to the newest, implemented
@@ -95,7 +97,7 @@ struct landlock_ruleset {
  	 * 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;
+	struct rb_root root_inode;
  	/**
  	 * @hierarchy: Enables hierarchy identification even when a parent
  	 * domain vanishes.  This is needed for the ptrace protection.
@@ -157,7 +159,9 @@ 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_object *const object, const u32 access);
+			 struct landlock_object *const object_ptr,
+			 const uintptr_t object_data,
+			 const u32 access, const u16 rule_type);

  struct landlock_ruleset *landlock_merge_ruleset(
  		struct landlock_ruleset *const parent,
@@ -165,7 +169,7 @@ struct landlock_ruleset *landlock_merge_ruleset(

  const struct landlock_rule *landlock_find_rule(
  		const struct landlock_ruleset *const ruleset,
-		const struct landlock_object *const object);
+		const uintptr_t object_data, const u16 rule_type);

  static inline void landlock_get_ruleset(struct landlock_ruleset *const ruleset)
  {
--
2.25.1




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