Re: [PATCH v6 02/17] landlock: refactors landlock_find/insert_rule

["Konstantin Meskhidze (A)" <konstantin.meskhidze@xxxxxxxxxx>]

7/7/2022 7:44 PM, Mickaël Salaün пишет:
> On 21/06/2022 10:22, Konstantin Meskhidze wrote:
> > Adds a new object union to support a socket port
> > rule type. Refactors landlock_insert_rule() and
> > landlock_find_rule() to support coming network
> > modifications. 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 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      |   7 ++-
> >   security/landlock/ruleset.c | 105 ++++++++++++++++++++++++++----------
> >   security/landlock/ruleset.h |  27 +++++-----
> >   3 files changed, 96 insertions(+), 43 deletions(-)
> >
> > diff --git a/security/landlock/fs.c b/security/landlock/fs.c
> > index e6da08ed99d1..46aedc2a05a8 100644
> > --- a/security/landlock/fs.c
> > +++ b/security/landlock/fs.c
> > @@ -173,7 +173,8 @@ 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);
> >   	mutex_unlock(&ruleset->lock);
> >   	/*
> >   	 * No need to check for an error because landlock_insert_rule()
> > @@ -204,7 +205,9 @@ 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));
> > +		domain,
> > +		(uintptr_t)rcu_dereference(landlock_inode(inode)->object),
> > +		LANDLOCK_RULE_PATH_BENEATH);
> >   	rcu_read_unlock();
> >   	return rule;
> >   }
> > diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
> > index a3fd58d01f09..5f13f8a12aee 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
> > @@ -69,7 +69,8 @@ static void build_check_rule(void)
> >   }
> >
> >   static struct landlock_rule *
> > -create_rule(struct landlock_object *const object,
> > +create_rule(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)
> >   {
> > @@ -90,8 +91,15 @@ 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 (object_ptr) {
> > +		landlock_get_object(object_ptr);
> > +		new_rule->object.ptr = object_ptr;
> > +	} else if (object_ptr && object_data) {
>
> Something is wrong with this second check: else + object_ptr?

It was your suggestion to use it like this:
" ....You can also add a WARN_ON_ONCE(object_ptr && object_data)."

Please check it here:
https://lore.kernel.org/linux-security-module/bc44f11f-0eaa-a5f6-c5dc-1d36570f1be1@xxxxxxxxxxx/

> > +		WARN_ON_ONCE(1);
> > +		return ERR_PTR(-EINVAL);
> > +	}
> > +
> >   	new_rule->num_layers = new_num_layers;
> >   	/* Copies the original layer stack. */
> >   	memcpy(new_rule->layers, layers,
> > @@ -107,7 +115,7 @@ 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);
> >   }
> >
> > @@ -143,26 +151,42 @@ 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,
> > +		       uintptr_t object_data, u16 rule_type,
>
> Use landlock_rule_type instead of u16, everywhere. It was part of my
> review/patch two versions ago (with other things), please take them into
> account:
> https://lore.kernel.org/r/92d498f0-c598-7413-6b7c-d19c5aec6cab@xxxxxxxxxxx
 Ok. Thanks for the reminder.
> >   		       const struct landlock_layer (*const layers)[],
> >   		       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 (WARN_ON_ONCE(object_ptr && object_data))
> > +		return -EINVAL;
> > +	/* Chooses rb_tree structure depending on a rule type. */
> > +	switch (rule_type) {
> > +	case LANDLOCK_RULE_PATH_BENEATH:
> > +		if (WARN_ON_ONCE(!object_ptr))
> > +			return -ENOENT;
> > +		object_data = (uintptr_t)object_ptr;
> > +		root = &ruleset->root_inode;
> > +		break;
> > +	default:
> > +		WARN_ON_ONCE(1);
> > +		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_data) {
> >   			parent_node = *walker_node;
> > -			if (this->object < object)
> > +			if (this->object.data < object_data)
> >   				walker_node = &((*walker_node)->rb_right);
> >   			else
> >   				walker_node = &((*walker_node)->rb_left);
> > @@ -194,11 +218,16 @@ 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:
> > +			new_rule = create_rule(object_ptr, 0, &this->layers,
> > +					       this->num_layers, &(*layers)[0]);
> > +			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);
> >   		free_rule(this);
> >   		return 0;
> >   	}
> > @@ -207,11 +236,15 @@ 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);
> > +		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;
> >   }
> > @@ -229,8 +262,9 @@ 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 access_mask_t access)
> > +			 struct landlock_object *const object_ptr,
> > +			 const uintptr_t object_data,
> > +			 const access_mask_t access, const u16 rule_type)
> >   {
> >   	struct landlock_layer layers[] = { {
> >   		.access = access,
> > @@ -239,7 +273,8 @@ 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, rule_type, &layers,
> > +			   ARRAY_SIZE(layers));
> >   }
> >
> >   static inline void get_hierarchy(struct landlock_hierarchy *const hierarchy)
> > @@ -284,8 +319,8 @@ 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,
> > -					     node) {
> > +	rbtree_postorder_for_each_entry_safe(walker_rule, next_rule,
> > +					     &src->root_inode, node) {
> >   		struct landlock_layer layers[] = { {
> >   			.level = dst->num_layers,
> >   		} };
> > @@ -299,7 +334,8 @@ 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,
> > +		err = insert_rule(dst, walker_rule->object.ptr, 0,
> > +				  LANDLOCK_RULE_PATH_BENEATH, &layers,
> >   				  ARRAY_SIZE(layers));
> >   		if (err)
> >   			goto out_unlock;
> > @@ -327,8 +363,9 @@ 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,
> > +					     &parent->root_inode, node) {
> > +		err = insert_rule(child, walker_rule->object.ptr, 0,
> > +				  LANDLOCK_RULE_PATH_BENEATH,
> >   				  &walker_rule->layers,
> >   				  walker_rule->num_layers);
> >   		if (err)
> > @@ -361,7 +398,8 @@ 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)
> > +	rbtree_postorder_for_each_entry_safe(freeme, next, &ruleset->root_inode,
> > +					     node)
> >   		free_rule(freeme);
> >   	put_hierarchy(ruleset->hierarchy);
> >   	kfree(ruleset);
> > @@ -453,20 +491,29 @@ 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 uintptr_t object_data, const u16 rule_type)
> >   {
> >   	const struct rb_node *node;
> >
> > -	if (!object)
> > +	if (!object_data)
> >   		return NULL;
> > -	node = ruleset->root.rb_node;
> > +
> > +	switch (rule_type) {
> > +	case LANDLOCK_RULE_PATH_BENEATH:
> > +		node = ruleset->root_inode.rb_node;
> > +		break;
> > +	default:
> > +		WARN_ON_ONCE(1);
> > +		return NULL;
> > +	}
> > +
> >   	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 bd7ab39859bf..a22d132c32a7 100644
> > --- a/security/landlock/ruleset.h
> > +++ b/security/landlock/ruleset.h
> > @@ -53,15 +53,17 @@ 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 raw data value (e.g. a network socket port). This is used as a key
> > +	 * for this ruleset element. This pointer/@object.ptr/ is set once and
> > +	 * never modified. It always points to an 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
> > @@ -98,7 +100,7 @@ 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.
> > @@ -160,8 +162,9 @@ 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 access_mask_t access);
> > +			 struct landlock_object *const object_ptr,
> > +			 const uintptr_t object_data,
> > +			 const access_mask_t access, const u16 rule_type);
> >
> >   struct landlock_ruleset *
> >   landlock_merge_ruleset(struct landlock_ruleset *const parent,
> > @@ -169,7 +172,7 @@ 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 uintptr_t object_data, const u16 rule_type);
> >
> >   static inline void landlock_get_ruleset(struct landlock_ruleset *const ruleset)
> >   {
> > --
> > 2.25.1
> .