[PATCH v8 02/12] landlock: Refactor landlock_find_rule/insert_rule

Konstantin Meskhidze (A) konstantin.meskhidze at huawei.com
Mon Nov 28 02:58:38 UTC 2022



11/17/2022 9:41 PM, Mickaël Salaün пишет:
> 
> On 21/10/2022 17:26, Konstantin Meskhidze wrote:
>> Adds a new landlock_key union and landlock_id structure to support
> 
> Add a new…

   Ok. Thanks.
> 
>> a socket port rule type. A struct landlock_id identifies a unique entry
>> in a ruleset: either a kernel object (e.g inode) or typed data (e.g TCP
>> port). There is one red-black tree per key type.
>> 
>> This patch also adds is_object_pointer() and get_root() helpers.
>> is_object_pointer() one checks whether key type is LANDLOCK_KEY_INODE.
> 
> is_object_pointer() returns true if the key type is LANDLOCK_KEY_INODE.
> 

  Got it.

>> get_root() helper chooses red_black tree root depending on a key type.
> 
> get_root() returns a red_black tree root pointer according to a key type.

  Ok. Thanks.

> 
>> 
>> Refactors landlock_insert_rule() and landlock_find_rule() to support coming
> 
> Refactor…

   Ok.
> 
>> network modifications. Now adding or searching a rule in a ruleset depends
> 
> … Adding or searching a rule in a ruleset can now be done

> 
>> on a landlock id argument provided in refactored functions.
> 
> thanks to a Landlock ID argument passed to these helpers.
> 

   I will rewrite it. Thanks.
>> 
>> Co-developed-by: Mickaël Salaün <mic at digikod.net>
> 
> Signed-off-by: Mickaël Salaün <mic at digikod.net>
> 
> 
>> Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze at huawei.com>
>> ---
>> 
>> Changes since v7:
>> * Completes all the new field descriptions landlock_key,
>>    landlock_key_type, landlock_id.
>> * Refactors commit message, adds a co-developer.
>> 
>> Changes since v6:
>> * Adds union landlock_key, enum landlock_key_type, and struct
>>    landlock_id.
>> * Refactors ruleset functions and improves switch/cases: create_rule(),
>>    insert_rule(), get_root(), is_object_pointer(), free_rule(),
>>    landlock_find_rule().
>> * Refactors landlock_append_fs_rule() functions to support new
>>    landlock_id type.
>> 
>> Changes since v5:
>> * Formats code with clang-format-14.
>> 
>> Changes since v4:
>> * Refactors insert_rule() and create_rule() functions by deleting
>> rule_type from their arguments list, it helps to reduce useless code.
>> 
>> Changes since v3:
>> * Splits commit.
>> * Refactors landlock_insert_rule and landlock_find_rule functions.
>> * Rename new_ruleset->root_inode.
>> 
>> ---
>>   security/landlock/fs.c      |  21 ++++--
>>   security/landlock/ruleset.c | 146 +++++++++++++++++++++++++-----------
>>   security/landlock/ruleset.h |  64 +++++++++++++---
>>   3 files changed, 169 insertions(+), 62 deletions(-)
>> 
>> diff --git a/security/landlock/fs.c b/security/landlock/fs.c
>> index 0d57c6479d29..710cfa1306de 100644
>> --- a/security/landlock/fs.c
>> +++ b/security/landlock/fs.c
>> @@ -168,7 +168,9 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
>>   			    access_mask_t access_rights)
>>   {
>>   	int err;
>> -	struct landlock_object *object;
>> +	struct landlock_id id = {
>> +		.type = LANDLOCK_KEY_INODE,
>> +	};
>> 
>>   	/* Files only get access rights that make sense. */
>>   	if (!d_is_dir(path->dentry) &&
>> @@ -181,17 +183,17 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
>>   	access_rights |= LANDLOCK_MASK_ACCESS_FS &
>>   			 ~(landlock_get_fs_access_mask(ruleset, 0) |
>>   			   ACCESS_INITIALLY_DENIED);
>> -	object = get_inode_object(d_backing_inode(path->dentry));
>> -	if (IS_ERR(object))
>> -		return PTR_ERR(object);
>> +	id.key.object = get_inode_object(d_backing_inode(path->dentry));
>> +	if (IS_ERR(id.key.object))
>> +		return PTR_ERR(id.key.object);
>>   	mutex_lock(&ruleset->lock);
>> -	err = landlock_insert_rule(ruleset, object, access_rights);
>> +	err = landlock_insert_rule(ruleset, id, access_rights);
>>   	mutex_unlock(&ruleset->lock);
>>   	/*
>>   	 * No need to check for an error because landlock_insert_rule()
>>   	 * increments the refcount for the new object if needed.
>>   	 */
>> -	landlock_put_object(object);
>> +	landlock_put_object(id.key.object);
>>   	return err;
>>   }
>> 
>> @@ -208,6 +210,9 @@ find_rule(const struct landlock_ruleset *const domain,
>>   {
>>   	const struct landlock_rule *rule;
>>   	const struct inode *inode;
>> +	struct landlock_id id = {
>> +		.type = LANDLOCK_KEY_INODE,
>> +	};
>> 
>>   	/* Ignores nonexistent leafs. */
>>   	if (d_is_negative(dentry))
>> @@ -215,8 +220,8 @@ find_rule(const struct landlock_ruleset *const domain,
>> 
>>   	inode = d_backing_inode(dentry);
>>   	rcu_read_lock();
>> -	rule = landlock_find_rule(
>> -		domain, rcu_dereference(landlock_inode(inode)->object));
>> +	id.key.object = rcu_dereference(landlock_inode(inode)->object);
>> +	rule = landlock_find_rule(domain, id);
>>   	rcu_read_unlock();
>>   	return rule;
>>   }
>> diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
>> index 1f3188b4e313..41de17d1869e 100644
>> --- a/security/landlock/ruleset.c
>> +++ b/security/landlock/ruleset.c
>> @@ -35,7 +35,7 @@ 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
>> @@ -68,8 +68,18 @@ static void build_check_rule(void)
>>   	BUILD_BUG_ON(rule.num_layers < LANDLOCK_MAX_NUM_LAYERS);
>>   }
>> 
>> +static inline bool is_object_pointer(const enum landlock_key_type key_type)
> 
> Let's remove all "inline" keywords in all .c files. This should be
> simple for the compiler to inline them automatically, and it makes the
> code cleaner.

   Got it.
> 
> 
>> +{
>> +	switch (key_type) {
>> +	case LANDLOCK_KEY_INODE:
>> +		return true;
>> +	}
>> +	WARN_ON_ONCE(1);
>> +	return false;
>> +}
>> +
>>   static struct landlock_rule *
>> -create_rule(struct landlock_object *const object,
>> +create_rule(const struct landlock_id id,
>>   	    const struct landlock_layer (*const layers)[], const u32 num_layers,
>>   	    const struct landlock_layer *const new_layer)
>>   {
>> @@ -90,8 +100,13 @@ create_rule(struct landlock_object *const object,
>>   	if (!new_rule)
>>   		return ERR_PTR(-ENOMEM);
>>   	RB_CLEAR_NODE(&new_rule->node);
>> -	landlock_get_object(object);
>> -	new_rule->object = object;
>> +	if (is_object_pointer(id.type)) {
>> +		/* This should be catched by insert_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,
>> @@ -102,12 +117,29 @@ create_rule(struct landlock_object *const object,
>>   	return new_rule;
>>   }
>> 
>> -static void free_rule(struct landlock_rule *const rule)
>> +static inline struct rb_root *get_root(struct landlock_ruleset *const ruleset,
> 
> Please remove "inline".

   Got it. Thanks.
> 
>> +				       const enum landlock_key_type key_type)
>> +{
>> +	struct rb_root *root = NULL;
>> +
>> +	switch (key_type) {
>> +	case LANDLOCK_KEY_INODE:
>> +		root = &ruleset->root_inode;
>> +		break;
>> +	}
>> +	if (WARN_ON_ONCE(!root))
>> +		return ERR_PTR(-EINVAL);
>> +	return root;
>> +}
>> +
>> +static void free_rule(struct landlock_rule *const rule,
>> +		      const enum landlock_key_type key_type)
>>   {
>>   	might_sleep();
>>   	if (!rule)
>>   		return;
>> -	landlock_put_object(rule->object);
>> +	if (is_object_pointer(key_type))
>> +		landlock_put_object(rule->key.object);
>>   	kfree(rule);
>>   }
>> 
>> @@ -129,8 +161,8 @@ static void build_check_ruleset(void)
>>    * insert_rule - Create and insert a rule in a ruleset
>>    *
>>    * @ruleset: The ruleset to be updated.
>> - * @object: The object to build the new rule with.  The underlying kernel
>> - *          object must be held by the caller.
>> + * @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.
>>    *
>> @@ -144,26 +176,37 @@ static void build_check_ruleset(void)
>>    * access rights.
>>    */
>>   static int insert_rule(struct landlock_ruleset *const ruleset,
>> -		       struct landlock_object *const object,
>> +		       const struct landlock_id id,
>>   		       const struct landlock_layer (*const layers)[],
>> -		       size_t num_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();
>>   	lockdep_assert_held(&ruleset->lock);
>> -	if (WARN_ON_ONCE(!object || !layers))
>> +	if (WARN_ON_ONCE(!layers))
>>   		return -ENOENT;
>> -	walker_node = &(ruleset->root.rb_node);
>> +
>> +	if (is_object_pointer(id.type)) {
>> +		if (WARN_ON_ONCE(!id.key.object))
>> +			return -ENOENT;
>> +	}
>> +
>> +	root = get_root(ruleset, 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->object != object) {
>> +		if (this->key.data != id.key.data) {
>>   			parent_node = *walker_node;
>> -			if (this->object < object)
>> +			if (this->key.data < id.key.data)
>>   				walker_node = &((*walker_node)->rb_right);
>>   			else
>>   				walker_node = &((*walker_node)->rb_left);
>> @@ -195,24 +238,24 @@ 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,
>> +		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, &ruleset->root);
>> -		free_rule(this);
>> +		rb_replace_node(&this->node, &new_rule->node, root);
>> +		free_rule(this, id.type);
>>   		return 0;
>>   	}
>> 
>> -	/* There is no match for @object. */
>> +	/* There is no match for @id. */
>>   	build_check_ruleset();
>>   	if (ruleset->num_rules >= LANDLOCK_MAX_NUM_RULES)
>>   		return -E2BIG;
>> -	new_rule = create_rule(object, layers, num_layers, NULL);
>> +	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, &ruleset->root);
>> +	rb_insert_color(&new_rule->node, root);
>>   	ruleset->num_rules++;
>>   	return 0;
>>   }
>> @@ -230,7 +273,7 @@ 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 struct landlock_id id,
>>   			 const access_mask_t access)
>>   {
>>   	struct landlock_layer layers[] = { {
>> @@ -240,7 +283,7 @@ 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, id, &layers, ARRAY_SIZE(layers));
>>   }
>> 
>>   static inline void get_hierarchy(struct landlock_hierarchy *const hierarchy)
>> @@ -263,6 +306,7 @@ static int merge_ruleset(struct landlock_ruleset *const dst,
>>   			 struct landlock_ruleset *const src)
>>   {
>>   	struct landlock_rule *walker_rule, *next_rule;
>> +	struct rb_root *src_root;
>>   	int err = 0;
>> 
>>   	might_sleep();
>> @@ -273,6 +317,10 @@ static int merge_ruleset(struct landlock_ruleset *const dst,
>>   	if (WARN_ON_ONCE(!dst || !dst->hierarchy))
>>   		return -EINVAL;
>> 
>> +	src_root = get_root(src, LANDLOCK_KEY_INODE);
>> +	if (IS_ERR(src_root))
>> +		return PTR_ERR(src_root);
>> +
>>   	/* Locks @dst first because we are its only owner. */
>>   	mutex_lock(&dst->lock);
>>   	mutex_lock_nested(&src->lock, SINGLE_DEPTH_NESTING);
>> @@ -285,23 +333,23 @@ static int merge_ruleset(struct landlock_ruleset *const dst,
>>   	dst->access_masks[dst->num_layers - 1] = src->access_masks[0];
>> 
>>   	/* Merges the @src tree. */
>> -	rbtree_postorder_for_each_entry_safe(walker_rule, next_rule, &src->root,
>> +	rbtree_postorder_for_each_entry_safe(walker_rule, next_rule, src_root,
>>   					     node) {
>>   		struct landlock_layer layers[] = { {
>>   			.level = dst->num_layers,
>>   		} };
>> +		const struct landlock_id id = {
>> +			.key = walker_rule->key,
>> +			.type = LANDLOCK_KEY_INODE,
>> +		};
>> 
>> -		if (WARN_ON_ONCE(walker_rule->num_layers != 1)) {
>> -			err = -EINVAL;
>> -			goto out_unlock;
>> -		}
>> -		if (WARN_ON_ONCE(walker_rule->layers[0].level != 0)) {
>> -			err = -EINVAL;
>> -			goto out_unlock;
>> -		}
>> +		if (WARN_ON_ONCE(walker_rule->num_layers != 1))
>> +			return -EINVAL;
>> +		if (WARN_ON_ONCE(walker_rule->layers[0].level != 0))
>> +			return -EINVAL;
>>   		layers[0].access = walker_rule->layers[0].access;
>> -		err = insert_rule(dst, walker_rule->object, &layers,
>> -				  ARRAY_SIZE(layers));
>> +
>> +		err = insert_rule(dst, id, &layers, ARRAY_SIZE(layers));
>>   		if (err)
>>   			goto out_unlock;
>>   	}
>> @@ -316,21 +364,29 @@ static int inherit_ruleset(struct landlock_ruleset *const parent,
>>   			   struct landlock_ruleset *const child)
>>   {
>>   	struct landlock_rule *walker_rule, *next_rule;
>> +	struct rb_root *parent_root;
>>   	int err = 0;
>> 
>>   	might_sleep();
>>   	if (!parent)
>>   		return 0;
>> 
>> +	parent_root = get_root(parent, LANDLOCK_KEY_INODE);
>> +	if (IS_ERR(parent_root))
>> +		return PTR_ERR(parent_root);
>> +
>>   	/* Locks @child first because we are its only owner. */
>>   	mutex_lock(&child->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 = insert_rule(child, walker_rule->object,
>> -				  &walker_rule->layers,
>> +					     parent_root, node) {
>> +		const struct landlock_id id = {
>> +			.key = walker_rule->key,
>> +			.type = LANDLOCK_KEY_INODE,
>> +		};
>> +		err = insert_rule(child, id, &walker_rule->layers,
>>   				  walker_rule->num_layers);
>>   		if (err)
>>   			goto out_unlock;
>> @@ -362,8 +418,9 @@ 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)
>> -		free_rule(freeme);
>> +	rbtree_postorder_for_each_entry_safe(freeme, next, &ruleset->root_inode,
>> +					     node)
>> +		free_rule(freeme, LANDLOCK_KEY_INODE);
>>   	put_hierarchy(ruleset->hierarchy);
>>   	kfree(ruleset);
>>   }
>> @@ -454,20 +511,23 @@ landlock_merge_ruleset(struct landlock_ruleset *const parent,
>>    */
>>   const struct landlock_rule *
>>   landlock_find_rule(const struct landlock_ruleset *const ruleset,
>> -		   const struct landlock_object *const object)
>> +		   const struct landlock_id id)
>>   {
>> +	const struct rb_root *root;
>>   	const struct rb_node *node;
>> 
>> -	if (!object)
>> +	root = get_root((struct landlock_ruleset *)ruleset, id.type);
>> +	if (IS_ERR(root))
>>   		return NULL;
>> -	node = ruleset->root.rb_node;
>> +	node = root->rb_node;
>> +
>>   	while (node) {
>>   		struct landlock_rule *this =
>>   			rb_entry(node, struct landlock_rule, node);
>> 
>> -		if (this->object == object)
>> +		if (this->key.data == id.key.data)
>>   			return this;
>> -		if (this->object < object)
>> +		if (this->key.data < id.key.data)
>>   			node = node->rb_right;
>>   		else
>>   			node = node->rb_left;
>> diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
>> index f2ad932d396c..608ab356bc3e 100644
>> --- a/security/landlock/ruleset.h
>> +++ b/security/landlock/ruleset.h
>> @@ -49,6 +49,46 @@ struct landlock_layer {
>>   	access_mask_t access;
>>   };
>> 
>> +/**
>> + * union landlock_key - Key of a ruleset's red-black tree
>> + */
>> +union landlock_key {
>> +	/**
>> +	 * @object: Pointer to identify a kernel object (e.g. an inode).
>> +	 */
>> +	struct landlock_object *object;
>> +	/**
>> +	 * @data: A raw data value to identify a network socket port.
> 
> "Raw data to identify an arbitrary 32-bit value (e.g. a TCP port)."
> 
   Ok.
> 
>> +	 */
>> +	uintptr_t data;
>> +};
>> +
>> +/**
>> + * enum landlock_key_type - Type of &union landlock_key
>> + */
>> +enum landlock_key_type {
>> +	/**
>> +	 * @LANDLOCK_KEY_INODE: Type of &landlock_ruleset.root_inode's node
>> +	 * keys.
>> +	 */
>> +	LANDLOCK_KEY_INODE = 1,
>> +};
>> +
>> +/**
>> + * struct landlock_id - Unique rule identifier for a ruleset
>> + */
>> +struct landlock_id {
>> +	/**
>> +	 * @key: A union to identify either a kernel object (e.g. an inode) or
>> +	 * a raw data value (e.g. a network socket port).
> 
> "a 32-bit value (e.g. a TCP port)."

   Ok. Got it.
> 
> 
>> +	 */
>> +	union landlock_key key;
>> +	/**
>> +	 * @type: A enumerator to identify the type of landlock_ruleset's root tree.
>> +	 */
>> +	const enum landlock_key_type type;
>> +};
>> +
>>   /**
>>    * struct landlock_rule - Access rights tied to an object
>>    */
>> @@ -58,12 +98,13 @@ 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.
>> +	 * @key: A union to identify either a kernel object (e.g. an inode) or
>> +	 * a raw data value (e.g. a network socket port). This is used as a key
>> +	 * for this ruleset element.  The 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;
>> +	union landlock_key key;
>>   	/**
>>   	 * @num_layers: Number of entries in @layers.
>>   	 */
>> @@ -99,11 +140,12 @@ struct landlock_hierarchy {
>>    */
>>   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.
>> +	 * @root_inode: Root of a red-black tree containing &struct
>> +	 * landlock_rule nodes with inode object.  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.
>> @@ -165,7 +207,7 @@ 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 struct landlock_id id,
>>   			 const access_mask_t access);
>> 
>>   struct landlock_ruleset *
>> @@ -174,7 +216,7 @@ landlock_merge_ruleset(struct landlock_ruleset *const parent,
>> 
>>   const struct landlock_rule *
>>   landlock_find_rule(const struct landlock_ruleset *const ruleset,
>> -		   const struct landlock_object *const object);
>> +		   const struct landlock_id id);
>> 
>>   static inline void landlock_get_ruleset(struct landlock_ruleset *const ruleset)
>>   {
>> --
>> 2.25.1
>> 
> .



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