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@xxxxxxxxxxx>
Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxx>
Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@xxxxxxxxxx>
---
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 b5fa6f56665f..6f9c463b291e 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 1f432a809ad5..d3859d5e7306 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))
+ 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 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);
@@ -285,11 +333,15 @@ 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 +352,8 @@ 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 +368,29 @@ 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 +422,9 @@ 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 +515,23 @@ 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 baef84071f37..5e1b1b25def0 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
