[PATCH v11 03/12] landlock: Refactor landlock_find_rule/insert_rule
Mickaël Salaün
mic at digikod.net
Mon Jun 26 18:58:59 UTC 2023
Complementary review:
On 15/05/2023 18:13, Konstantin Meskhidze wrote:
> 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.
>
> 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 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 | 134 ++++++++++++++++++++++++++----------
> security/landlock/ruleset.h | 65 ++++++++++++++---
> 3 files changed, 166 insertions(+), 54 deletions(-)
>
> diff --git a/security/landlock/fs.c b/security/landlock/fs.c
> index a0c9c927fdf9..9a8e70f65a88 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..deab37838f5b 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 bool is_object_pointer(const enum landlock_key_type key_type)
> +{
> + 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 struct rb_root *get_root(struct landlock_ruleset *const ruleset,
> + 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))
This would be simpler:
if (is_object_pointer(id.type) && WARN_ON_ONCE(!id.key.object))
return -ENOENT;
> + return -ENOENT;
> + }
> +
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