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Message-ID: <6535183b-5fad-e3a9-1350-d22122205be6@huawei.com>
Date: Thu, 17 Mar 2022 17:29:13 +0300
From: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
To: Mickaël Salaün <mic@...ikod.net>
CC: <willemdebruijn.kernel@...il.com>,
<linux-security-module@...r.kernel.org>, <netdev@...r.kernel.org>,
<netfilter-devel@...r.kernel.org>, <yusongping@...wei.com>,
<artem.kuzin@...wei.com>, <anton.sirazetdinov@...wei.com>
Subject: Re: [RFC PATCH v4 03/15] landlock: landlock_find/insert_rule
refactoring
3/16/2022 11:27 AM, Mickaël Salaün пишет:
>
> On 09/03/2022 14:44, Konstantin Meskhidze wrote:
>> A new object union added to support a socket port
>> rule type. To support it landlock_insert_rule() and
>> landlock_find_rule() were refactored. 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 v3:
>> * Split commit.
>> * Refactoring landlock_insert_rule and landlock_find_rule functions.
>> * Rename new_ruleset->root_inode.
>>
>> ---
>> security/landlock/fs.c | 5 +-
>> security/landlock/ruleset.c | 108 +++++++++++++++++++++++++-----------
>> security/landlock/ruleset.h | 26 +++++----
>> 3 files changed, 94 insertions(+), 45 deletions(-)
>>
>> diff --git a/security/landlock/fs.c b/security/landlock/fs.c
>> index 97f5c455f5a7..1497948d754f 100644
>> --- a/security/landlock/fs.c
>> +++ b/security/landlock/fs.c
>> @@ -168,7 +168,7 @@ 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);
>
> For consistency, please use 80 columns everywhere.
Ok. I got it.
>
>> mutex_unlock(&ruleset->lock);
>> /*
>> * No need to check for an error because landlock_insert_rule()
>> @@ -195,7 +195,8 @@ static inline u64 unmask_layers(
>> inode = d_backing_inode(path->dentry);
>> rcu_read_lock();
>> rule = landlock_find_rule(domain,
>> - rcu_dereference(landlock_inode(inode)->object));
>> + (uintptr_t)rcu_dereference(landlock_inode(inode)->object),
>> + LANDLOCK_RULE_PATH_BENEATH);
>> rcu_read_unlock();
>> if (!rule)
>> return layer_mask;
>> diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
>> index a6212b752549..971685c48641 100644
>> --- a/security/landlock/ruleset.c
>> +++ b/security/landlock/ruleset.c
>> @@ -34,7 +34,7 @@ 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
>> @@ -81,10 +81,12 @@ static void build_check_rule(void)
>> }
>>
>> static struct landlock_rule *create_rule(
>> - struct landlock_object *const object,
>> + 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)
>> + const struct landlock_layer *const new_layer,
>> + const u16 rule_type)
>> {
>> struct landlock_rule *new_rule;
>> u32 new_num_layers;
>> @@ -103,8 +105,16 @@ static struct landlock_rule *create_rule(
>> if (!new_rule)
>> return ERR_PTR(-ENOMEM);
>> RB_CLEAR_NODE(&new_rule->node);
>> - landlock_get_object(object);
>> - new_rule->object = object;
>> +
>> + switch (rule_type) {
>> + case LANDLOCK_RULE_PATH_BENEATH:
>> + landlock_get_object(object_ptr);
>> + new_rule->object.ptr = object_ptr;
>> + break;
>> + default:
>> + return ERR_PTR(-EINVAL);
>
> This would lead to memory leak. You should at least add a
> WARN_ON_ONCE(1) here, but a proper solution would be to remove the use
> of rule_type and only rely on object_ptr and object_data values. You can
> also add a WARN_ON_ONCE(object_ptr && object_data).
>
>
But rule_type is needed here in coming commits to support network
rules. For LANDLOCK_RULE_PATH_BENEATH rule type landlock_get_object()
is used but for LANDLOCK_RULE_NET_SERVICE is not. Using rule type is
convenient for distinguising between fs and network rules.
>> + }
>> +
>> new_rule->num_layers = new_num_layers;
>> /* Copies the original layer stack. */
>> memcpy(new_rule->layers, layers,
>> @@ -120,7 +130,7 @@ 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);
>> }
>>
>> @@ -156,26 +166,38 @@ 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,
>> + const uintptr_t object_data,
>> const struct landlock_layer (*const layers)[],
>> - size_t num_layers)
>> + size_t num_layers, u16 rule_type)
>> {
>> struct rb_node **walker_node;
>> struct rb_node *parent_node = NULL;
>> struct landlock_rule *new_rule;
>> + uintptr_t object;
>> + struct rb_root *root;
>>
>> might_sleep();
>> lockdep_assert_held(&ruleset->lock);
>> - if (WARN_ON_ONCE(!object || !layers))
>> - return -ENOENT;
>
> You can leave this code here.
But anyway in coming commits with network rules this code will be
moved into case LANDLOCK_RULE_PATH_BENEATH: ....
>
>> - walker_node = &(ruleset->root.rb_node);
>> + /* Choose rb_tree structure depending on a rule type */
>> + switch (rule_type) {
>> + case LANDLOCK_RULE_PATH_BENEATH:
>> + if (WARN_ON_ONCE(!object_ptr || !layers))
>> + return -ENOENT;
>> + object = (uintptr_t)object_ptr;
>> + root = &ruleset->root_inode;
>> + break;
>> + default:
>> + 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) {
>> parent_node = *walker_node;
>> - if (this->object < object)
>> + if (this->object.data < object)
>> walker_node = &((*walker_node)->rb_right);
>> else
>> walker_node = &((*walker_node)->rb_left);
>> @@ -207,11 +229,15 @@ 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:
>
> Same here and for the following code, you should replace such
> switch/case with an if (object_ptr).
> What about coming commits with network rule_type support?
>
>> + new_rule = create_rule(object_ptr, 0, &this->layers,
>> this->num_layers,
>> + &(*layers)[0], rule_type);
>> + 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);
>
> Use the root variable here. Same for the following code and patches.
What about your suggestion to use 2 rb_tress to support different
rule_types:
1. root_inode - for filesystem objects
2. root_net_port - for network port objects
????
>
>
>> free_rule(this);
>> return 0;
>> }
>> @@ -220,11 +246,15 @@ 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, rule_type);
>> + 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;
>> }
>> @@ -242,7 +272,9 @@ 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 u32 access)
>> + struct landlock_object *const object_ptr,
>> + const uintptr_t object_data,
>> + const u32 access, const u16 rule_type)
>> {
>> struct landlock_layer layers[] = {{
>> .access = access,
>> @@ -251,7 +283,8 @@ 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, &layers,
>> + ARRAY_SIZE(layers), rule_type);
>> }
>>
>> static inline void get_hierarchy(struct landlock_hierarchy *const
>> hierarchy)
>> @@ -297,7 +330,7 @@ static int merge_ruleset(struct landlock_ruleset
>> *const dst,
>>
>> /* Merges the @src tree. */
>> rbtree_postorder_for_each_entry_safe(walker_rule, next_rule,
>> - &src->root, node) {
>> + &src->root_inode, node) {
>> struct landlock_layer layers[] = {{
>> .level = dst->num_layers,
>> }};
>> @@ -311,8 +344,8 @@ 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, walker_rule->object.ptr, 0, &layers,
>> + ARRAY_SIZE(layers), LANDLOCK_RULE_PATH_BENEATH);
>> if (err)
>> goto out_unlock;
>> }
>> @@ -323,6 +356,8 @@ static int merge_ruleset(struct landlock_ruleset
>> *const dst,
>> return err;
>> }
>>
>> +
>> +
>
> Useless lines.
Got it. Thanks.
>
>
>> static int inherit_ruleset(struct landlock_ruleset *const parent,
>> struct landlock_ruleset *const child)
>> {
>> @@ -339,9 +374,10 @@ 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,
>> - &walker_rule->layers, walker_rule->num_layers);
>> + &parent->root_inode, node) {
>> + err = insert_rule(child, walker_rule->object.ptr, 0,
>> + &walker_rule->layers, walker_rule->num_layers,
>> + LANDLOCK_RULE_PATH_BENEATH);
>> if (err)
>> goto out_unlock;
>> }
>> @@ -372,7 +408,7 @@ 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,
>> + rbtree_postorder_for_each_entry_safe(freeme, next,
>> &ruleset->root_inode,
>> node)
>> free_rule(freeme);
>> put_hierarchy(ruleset->hierarchy);
>> @@ -465,20 +501,28 @@ struct landlock_ruleset *landlock_merge_ruleset(
>> */
>> 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)
>
> object_data can be 0. You need to add a test with such value.
>
> We need to be sure that this change cannot affect the current FS code.
I got it. I will refactor it.
>
>
>> return NULL;
>> - node = ruleset->root.rb_node;
>> +
>> + switch (rule_type) {
>> + case LANDLOCK_RULE_PATH_BENEATH:
>> + node = ruleset->root_inode.rb_node;
>> + break;
>> + default:
>> + return ERR_PTR(-EINVAL);
>
> This is a bug. There is no check for such value. You need to check and
> update all call sites to catch such errors. Same for all new use of
> ERR_PTR().
Sorry, I did not get your point.
Do you mean I should check the correctness of rule_type in above
function which calls landlock_find_rule() ??? Why can't I add such check
here?
>
>
>> + }
>> +
>> 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 bc87e5f787f7..088b8d95f653 100644
>> --- a/security/landlock/ruleset.h
>> +++ b/security/landlock/ruleset.h
>> @@ -50,15 +50,17 @@ 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 socket port object.
>
> …or a raw data value (e.g. a network socket port).
>
Ok. I will mofdify this line
>
>> This is used as a key for this ruleset element.
>> + * This pointer is set once and never modified. It always points
>> to an
>
> s/This pointer/@...ect.ptr/
Ok. I got it.
>
>
>> + * 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
>> @@ -95,7 +97,7 @@ 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.
>> @@ -157,7 +159,9 @@ 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 u32 access);
>> + struct landlock_object *const object_ptr,
>> + const uintptr_t object_data,
>> + const u32 access, const u16 rule_type);
>>
>> struct landlock_ruleset *landlock_merge_ruleset(
>> struct landlock_ruleset *const parent,
>> @@ -165,7 +169,7 @@ struct landlock_ruleset *landlock_merge_ruleset(
>>
>> 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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