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Date: Thu, 7 Jul 2022 18:44:53 +0200
From: Mickaël Salaün <mic@...ikod.net>
To: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
Cc: willemdebruijn.kernel@...il.com,
linux-security-module@...r.kernel.org, netdev@...r.kernel.org,
netfilter-devel@...r.kernel.org, yusongping@...wei.com,
anton.sirazetdinov@...wei.com
Subject: Re: [PATCH v6 02/17] landlock: refactors landlock_find/insert_rule
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@...wei.com>
> ---
>
> 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?
> + 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@digikod.net
> 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/@...ect.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
>
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