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landlock: Refactor landlock_find_rule/insert_rule helpers

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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.

Add 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@huawei.com>
Link: https://lore.kernel.org/r/20231026014751.414649-4-konstantin.meskhidze@huawei.com
[mic: Fix commit message typo]
Co-developed-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
This commit is contained in:
Konstantin Meskhidze 2023-10-26 09:47:42 +08:00 committed by Mickaël Salaün
parent d722036403
commit a4ac404b30
No known key found for this signature in database
GPG Key ID: E5E3D0E88C82F6D2
3 changed files with 165 additions and 54 deletions
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21
security/landlock/fs.c
View File

@ -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;
}

133
security/landlock/ruleset.c
View File

@ -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 +119,27 @@ 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:
WARN_ON_ONCE(1);
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 +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 +176,35 @@ 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;
walker_node = &(ruleset->root.rb_node);
if (is_object_pointer(id.type) && 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 +236,24 @@ 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 +271,7 @@ 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 +281,7 @@ 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 +304,7 @@ 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 +315,10 @@ 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 +331,15 @@ 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 +350,8 @@ 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 +366,30 @@ 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 +421,9 @@ 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 +514,23 @@ out_put_dom:
*/
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;

65
security/landlock/ruleset.h
View File

@ -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)
{