Add a new landlock_key union and landlock_id structure to support 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() returns true if key type is LANDLOCK_KEY_INODE. get_root() helper returns a red_black tree root pointer according to a key type. Refactor landlock_insert_rule() and landlock_find_rule() to support coming network modifications. Adding or searching a rule in ruleset can now be done thanks to a Landlock ID argument passed to these helpers. Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@xxxxxxxxxx> Link: https://lore.kernel.org/r/20230920092641.832134-4-konstantin.meskhidze@xxxxxxxxxx Co-developed-by: Mickaël Salaün <mic@xxxxxxxxxxx> Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxx> --- Changes since v12: * None. Changes since v11: * Adds "default" case in is_object_pointer() and get_root(). * Removes the "root" variable from get_root(). * Minor fixes. Changes since v10: * None. Changes since v9: * Splits commit. * Refactors commit message. * Minor fixes. Changes since v8: * Refactors commit message. * Removes inlining. * Minor fixes. 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 | 132 ++++++++++++++++++++++++++---------- security/landlock/ruleset.h | 65 +++++++++++++++--- 3 files changed, 164 insertions(+), 54 deletions(-) diff --git a/security/landlock/fs.c b/security/landlock/fs.c index e8d680c2c80a..9edb64ac8251 100644 --- a/security/landlock/fs.c +++ b/security/landlock/fs.c @@ -158,7 +158,9 @@ 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) && @@ -170,17 +172,17 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset, /* Transforms relative access rights to absolute ones. */ access_rights |= LANDLOCK_MASK_ACCESS_FS & ~landlock_get_fs_access_mask(ruleset, 0); - 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; } @@ -197,6 +199,9 @@ 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)) @@ -204,8 +209,8 @@ 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..d5993e6254e4 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 +68,20 @@ static void build_check_rule(void) BUILD_BUG_ON(rule.num_layers < LANDLOCK_MAX_NUM_LAYERS); } +static bool is_object_pointer(const enum landlock_key_type key_type) +{ + switch (key_type) { + case LANDLOCK_KEY_INODE: + return true; + + default: + 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 +102,13 @@ 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 +119,26 @@ create_rule(struct landlock_object *const object, return new_rule; } -static void free_rule(struct landlock_rule *const rule) +static struct rb_root *get_root(struct landlock_ruleset *const ruleset, + const enum landlock_key_type key_type) +{ + switch (key_type) { + case LANDLOCK_KEY_INODE: + return &ruleset->root_inode; + + default: + return ERR_PTR(-EINVAL); + } +} + +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 +160,8 @@ 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 +175,35 @@ 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; + + if (is_object_pointer(id.type) && WARN_ON_ONCE(!id.key.object)) return -ENOENT; - walker_node = &(ruleset->root.rb_node); + + 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 +235,24 @@ 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 +270,7 @@ 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 +280,7 @@ 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 +303,7 @@ 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 +314,10 @@ 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); @@ -285,11 +330,15 @@ 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; @@ -300,8 +349,8 @@ 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, id, &layers, ARRAY_SIZE(layers)); if (err) goto out_unlock; } @@ -316,21 +365,30 @@ 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 +420,9 @@ 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 +513,23 @@ 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 6e2ad1546ab3..9e04c666b23c 100644 --- a/security/landlock/ruleset.h +++ b/security/landlock/ruleset.h @@ -60,6 +60,47 @@ 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: Raw data to identify an arbitrary 32-bit value + * (e.g. a TCP port). + */ + 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: Identifies either a kernel object (e.g. an inode) or + * a raw value (e.g. a TCP port). + */ + union landlock_key key; + /** + * @type: Type of a landlock_ruleset's root tree. + */ + const enum landlock_key_type type; +}; + /** * struct landlock_rule - Access rights tied to an object */ @@ -69,12 +110,13 @@ 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. */ @@ -110,11 +152,12 @@ 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. @@ -176,7 +219,7 @@ 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 * @@ -185,7 +228,7 @@ 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
