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![Günther Noack](/assets/img/avatar_default.png)
This call is now going through a function pointer,
and it is not as obvious any more that it will be inlined.
Signed-off-by: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20231208155121.1943775-4-gnoack@google.com
Fixes: 7a11275c37
("landlock: Refactor layer helpers")
Signed-off-by: Mickaël Salaün <mic@digikod.net>
740 lines
19 KiB
C
740 lines
19 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Landlock LSM - Ruleset management
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*
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* Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net>
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* Copyright © 2018-2020 ANSSI
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*/
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#include <linux/bits.h>
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#include <linux/bug.h>
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#include <linux/compiler_types.h>
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#include <linux/err.h>
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#include <linux/errno.h>
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#include <linux/kernel.h>
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#include <linux/lockdep.h>
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#include <linux/overflow.h>
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#include <linux/rbtree.h>
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#include <linux/refcount.h>
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#include <linux/slab.h>
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#include <linux/spinlock.h>
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#include <linux/workqueue.h>
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#include "limits.h"
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#include "object.h"
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#include "ruleset.h"
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static struct landlock_ruleset *create_ruleset(const u32 num_layers)
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{
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struct landlock_ruleset *new_ruleset;
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new_ruleset =
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kzalloc(struct_size(new_ruleset, access_masks, num_layers),
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GFP_KERNEL_ACCOUNT);
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if (!new_ruleset)
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return ERR_PTR(-ENOMEM);
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refcount_set(&new_ruleset->usage, 1);
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mutex_init(&new_ruleset->lock);
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new_ruleset->root_inode = RB_ROOT;
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#if IS_ENABLED(CONFIG_INET)
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new_ruleset->root_net_port = RB_ROOT;
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#endif /* IS_ENABLED(CONFIG_INET) */
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new_ruleset->num_layers = num_layers;
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/*
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* hierarchy = NULL
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* num_rules = 0
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* access_masks[] = 0
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*/
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return new_ruleset;
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}
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struct landlock_ruleset *
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landlock_create_ruleset(const access_mask_t fs_access_mask,
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const access_mask_t net_access_mask)
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{
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struct landlock_ruleset *new_ruleset;
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/* Informs about useless ruleset. */
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if (!fs_access_mask && !net_access_mask)
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return ERR_PTR(-ENOMSG);
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new_ruleset = create_ruleset(1);
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if (IS_ERR(new_ruleset))
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return new_ruleset;
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if (fs_access_mask)
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landlock_add_fs_access_mask(new_ruleset, fs_access_mask, 0);
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if (net_access_mask)
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landlock_add_net_access_mask(new_ruleset, net_access_mask, 0);
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return new_ruleset;
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}
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static void build_check_rule(void)
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{
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const struct landlock_rule rule = {
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.num_layers = ~0,
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};
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BUILD_BUG_ON(rule.num_layers < LANDLOCK_MAX_NUM_LAYERS);
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}
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static bool is_object_pointer(const enum landlock_key_type key_type)
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{
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switch (key_type) {
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case LANDLOCK_KEY_INODE:
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return true;
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#if IS_ENABLED(CONFIG_INET)
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case LANDLOCK_KEY_NET_PORT:
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return false;
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#endif /* IS_ENABLED(CONFIG_INET) */
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default:
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WARN_ON_ONCE(1);
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return false;
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}
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}
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static struct landlock_rule *
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create_rule(const struct landlock_id id,
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const struct landlock_layer (*const layers)[], const u32 num_layers,
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const struct landlock_layer *const new_layer)
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{
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struct landlock_rule *new_rule;
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u32 new_num_layers;
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build_check_rule();
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if (new_layer) {
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/* Should already be checked by landlock_merge_ruleset(). */
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if (WARN_ON_ONCE(num_layers >= LANDLOCK_MAX_NUM_LAYERS))
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return ERR_PTR(-E2BIG);
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new_num_layers = num_layers + 1;
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} else {
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new_num_layers = num_layers;
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}
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new_rule = kzalloc(struct_size(new_rule, layers, new_num_layers),
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GFP_KERNEL_ACCOUNT);
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if (!new_rule)
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return ERR_PTR(-ENOMEM);
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RB_CLEAR_NODE(&new_rule->node);
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if (is_object_pointer(id.type)) {
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/* This should be catched by insert_rule(). */
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WARN_ON_ONCE(!id.key.object);
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landlock_get_object(id.key.object);
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}
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new_rule->key = id.key;
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new_rule->num_layers = new_num_layers;
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/* Copies the original layer stack. */
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memcpy(new_rule->layers, layers,
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flex_array_size(new_rule, layers, num_layers));
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if (new_layer)
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/* Adds a copy of @new_layer on the layer stack. */
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new_rule->layers[new_rule->num_layers - 1] = *new_layer;
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return new_rule;
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}
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static struct rb_root *get_root(struct landlock_ruleset *const ruleset,
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const enum landlock_key_type key_type)
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{
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switch (key_type) {
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case LANDLOCK_KEY_INODE:
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return &ruleset->root_inode;
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#if IS_ENABLED(CONFIG_INET)
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case LANDLOCK_KEY_NET_PORT:
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return &ruleset->root_net_port;
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#endif /* IS_ENABLED(CONFIG_INET) */
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default:
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WARN_ON_ONCE(1);
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return ERR_PTR(-EINVAL);
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}
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}
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static void free_rule(struct landlock_rule *const rule,
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const enum landlock_key_type key_type)
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{
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might_sleep();
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if (!rule)
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return;
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if (is_object_pointer(key_type))
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landlock_put_object(rule->key.object);
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kfree(rule);
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}
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static void build_check_ruleset(void)
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{
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const struct landlock_ruleset ruleset = {
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.num_rules = ~0,
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.num_layers = ~0,
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};
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typeof(ruleset.access_masks[0]) access_masks = ~0;
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BUILD_BUG_ON(ruleset.num_rules < LANDLOCK_MAX_NUM_RULES);
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BUILD_BUG_ON(ruleset.num_layers < LANDLOCK_MAX_NUM_LAYERS);
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BUILD_BUG_ON(access_masks <
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((LANDLOCK_MASK_ACCESS_FS << LANDLOCK_SHIFT_ACCESS_FS) |
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(LANDLOCK_MASK_ACCESS_NET << LANDLOCK_SHIFT_ACCESS_NET)));
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}
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/**
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* insert_rule - Create and insert a rule in a ruleset
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*
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* @ruleset: The ruleset to be updated.
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* @id: The ID to build the new rule with. The underlying kernel object, if
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* any, must be held by the caller.
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* @layers: One or multiple layers to be copied into the new rule.
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* @num_layers: The number of @layers entries.
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*
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* When user space requests to add a new rule to a ruleset, @layers only
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* contains one entry and this entry is not assigned to any level. In this
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* case, the new rule will extend @ruleset, similarly to a boolean OR between
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* access rights.
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*
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* When merging a ruleset in a domain, or copying a domain, @layers will be
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* added to @ruleset as new constraints, similarly to a boolean AND between
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* access rights.
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*/
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static int insert_rule(struct landlock_ruleset *const ruleset,
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const struct landlock_id id,
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const struct landlock_layer (*const layers)[],
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const size_t num_layers)
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{
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struct rb_node **walker_node;
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struct rb_node *parent_node = NULL;
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struct landlock_rule *new_rule;
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struct rb_root *root;
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might_sleep();
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lockdep_assert_held(&ruleset->lock);
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if (WARN_ON_ONCE(!layers))
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return -ENOENT;
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if (is_object_pointer(id.type) && WARN_ON_ONCE(!id.key.object))
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return -ENOENT;
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root = get_root(ruleset, id.type);
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if (IS_ERR(root))
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return PTR_ERR(root);
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walker_node = &root->rb_node;
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while (*walker_node) {
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struct landlock_rule *const this =
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rb_entry(*walker_node, struct landlock_rule, node);
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if (this->key.data != id.key.data) {
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parent_node = *walker_node;
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if (this->key.data < id.key.data)
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walker_node = &((*walker_node)->rb_right);
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else
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walker_node = &((*walker_node)->rb_left);
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continue;
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}
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/* Only a single-level layer should match an existing rule. */
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if (WARN_ON_ONCE(num_layers != 1))
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return -EINVAL;
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/* If there is a matching rule, updates it. */
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if ((*layers)[0].level == 0) {
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/*
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* Extends access rights when the request comes from
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* landlock_add_rule(2), i.e. @ruleset is not a domain.
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*/
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if (WARN_ON_ONCE(this->num_layers != 1))
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return -EINVAL;
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if (WARN_ON_ONCE(this->layers[0].level != 0))
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return -EINVAL;
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this->layers[0].access |= (*layers)[0].access;
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return 0;
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}
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if (WARN_ON_ONCE(this->layers[0].level == 0))
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return -EINVAL;
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/*
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* Intersects access rights when it is a merge between a
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* ruleset and a domain.
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*/
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new_rule = create_rule(id, &this->layers, this->num_layers,
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&(*layers)[0]);
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if (IS_ERR(new_rule))
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return PTR_ERR(new_rule);
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rb_replace_node(&this->node, &new_rule->node, root);
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free_rule(this, id.type);
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return 0;
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}
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/* There is no match for @id. */
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build_check_ruleset();
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if (ruleset->num_rules >= LANDLOCK_MAX_NUM_RULES)
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return -E2BIG;
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new_rule = create_rule(id, layers, num_layers, NULL);
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if (IS_ERR(new_rule))
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return PTR_ERR(new_rule);
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rb_link_node(&new_rule->node, parent_node, walker_node);
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rb_insert_color(&new_rule->node, root);
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ruleset->num_rules++;
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return 0;
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}
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static void build_check_layer(void)
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{
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const struct landlock_layer layer = {
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.level = ~0,
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.access = ~0,
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};
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BUILD_BUG_ON(layer.level < LANDLOCK_MAX_NUM_LAYERS);
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BUILD_BUG_ON(layer.access < LANDLOCK_MASK_ACCESS_FS);
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}
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/* @ruleset must be locked by the caller. */
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int landlock_insert_rule(struct landlock_ruleset *const ruleset,
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const struct landlock_id id,
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const access_mask_t access)
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{
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struct landlock_layer layers[] = { {
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.access = access,
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/* When @level is zero, insert_rule() extends @ruleset. */
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.level = 0,
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} };
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build_check_layer();
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return insert_rule(ruleset, id, &layers, ARRAY_SIZE(layers));
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}
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static void get_hierarchy(struct landlock_hierarchy *const hierarchy)
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{
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if (hierarchy)
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refcount_inc(&hierarchy->usage);
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}
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static void put_hierarchy(struct landlock_hierarchy *hierarchy)
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{
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while (hierarchy && refcount_dec_and_test(&hierarchy->usage)) {
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const struct landlock_hierarchy *const freeme = hierarchy;
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hierarchy = hierarchy->parent;
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kfree(freeme);
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}
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}
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static int merge_tree(struct landlock_ruleset *const dst,
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struct landlock_ruleset *const src,
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const enum landlock_key_type key_type)
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{
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struct landlock_rule *walker_rule, *next_rule;
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struct rb_root *src_root;
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int err = 0;
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might_sleep();
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lockdep_assert_held(&dst->lock);
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lockdep_assert_held(&src->lock);
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src_root = get_root(src, key_type);
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if (IS_ERR(src_root))
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return PTR_ERR(src_root);
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/* Merges the @src tree. */
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rbtree_postorder_for_each_entry_safe(walker_rule, next_rule, src_root,
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node) {
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struct landlock_layer layers[] = { {
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.level = dst->num_layers,
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} };
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const struct landlock_id id = {
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.key = walker_rule->key,
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.type = key_type,
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};
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if (WARN_ON_ONCE(walker_rule->num_layers != 1))
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return -EINVAL;
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if (WARN_ON_ONCE(walker_rule->layers[0].level != 0))
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return -EINVAL;
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layers[0].access = walker_rule->layers[0].access;
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err = insert_rule(dst, id, &layers, ARRAY_SIZE(layers));
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if (err)
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return err;
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}
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return err;
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}
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static int merge_ruleset(struct landlock_ruleset *const dst,
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struct landlock_ruleset *const src)
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{
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int err = 0;
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might_sleep();
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/* Should already be checked by landlock_merge_ruleset() */
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if (WARN_ON_ONCE(!src))
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return 0;
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/* Only merge into a domain. */
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if (WARN_ON_ONCE(!dst || !dst->hierarchy))
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return -EINVAL;
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/* Locks @dst first because we are its only owner. */
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mutex_lock(&dst->lock);
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mutex_lock_nested(&src->lock, SINGLE_DEPTH_NESTING);
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/* Stacks the new layer. */
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if (WARN_ON_ONCE(src->num_layers != 1 || dst->num_layers < 1)) {
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err = -EINVAL;
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goto out_unlock;
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}
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dst->access_masks[dst->num_layers - 1] = src->access_masks[0];
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/* Merges the @src inode tree. */
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err = merge_tree(dst, src, LANDLOCK_KEY_INODE);
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if (err)
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goto out_unlock;
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#if IS_ENABLED(CONFIG_INET)
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/* Merges the @src network port tree. */
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err = merge_tree(dst, src, LANDLOCK_KEY_NET_PORT);
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if (err)
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goto out_unlock;
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#endif /* IS_ENABLED(CONFIG_INET) */
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out_unlock:
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mutex_unlock(&src->lock);
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mutex_unlock(&dst->lock);
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return err;
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}
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static int inherit_tree(struct landlock_ruleset *const parent,
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struct landlock_ruleset *const child,
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const enum landlock_key_type key_type)
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{
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struct landlock_rule *walker_rule, *next_rule;
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struct rb_root *parent_root;
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int err = 0;
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might_sleep();
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lockdep_assert_held(&parent->lock);
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lockdep_assert_held(&child->lock);
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parent_root = get_root(parent, key_type);
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if (IS_ERR(parent_root))
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return PTR_ERR(parent_root);
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/* Copies the @parent inode or network tree. */
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rbtree_postorder_for_each_entry_safe(walker_rule, next_rule,
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parent_root, node) {
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const struct landlock_id id = {
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.key = walker_rule->key,
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.type = key_type,
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};
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err = insert_rule(child, id, &walker_rule->layers,
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walker_rule->num_layers);
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if (err)
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return err;
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}
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return err;
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}
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static int inherit_ruleset(struct landlock_ruleset *const parent,
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struct landlock_ruleset *const child)
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{
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int err = 0;
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might_sleep();
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if (!parent)
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return 0;
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/* Locks @child first because we are its only owner. */
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mutex_lock(&child->lock);
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mutex_lock_nested(&parent->lock, SINGLE_DEPTH_NESTING);
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/* Copies the @parent inode tree. */
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err = inherit_tree(parent, child, LANDLOCK_KEY_INODE);
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if (err)
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goto out_unlock;
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#if IS_ENABLED(CONFIG_INET)
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/* Copies the @parent network port tree. */
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err = inherit_tree(parent, child, LANDLOCK_KEY_NET_PORT);
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if (err)
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goto out_unlock;
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#endif /* IS_ENABLED(CONFIG_INET) */
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if (WARN_ON_ONCE(child->num_layers <= parent->num_layers)) {
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err = -EINVAL;
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goto out_unlock;
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}
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/* Copies the parent layer stack and leaves a space for the new layer. */
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memcpy(child->access_masks, parent->access_masks,
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flex_array_size(parent, access_masks, parent->num_layers));
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if (WARN_ON_ONCE(!parent->hierarchy)) {
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err = -EINVAL;
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goto out_unlock;
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}
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get_hierarchy(parent->hierarchy);
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child->hierarchy->parent = parent->hierarchy;
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out_unlock:
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mutex_unlock(&parent->lock);
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mutex_unlock(&child->lock);
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return err;
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}
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static void free_ruleset(struct landlock_ruleset *const ruleset)
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{
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struct landlock_rule *freeme, *next;
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might_sleep();
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rbtree_postorder_for_each_entry_safe(freeme, next, &ruleset->root_inode,
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node)
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free_rule(freeme, LANDLOCK_KEY_INODE);
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#if IS_ENABLED(CONFIG_INET)
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rbtree_postorder_for_each_entry_safe(freeme, next,
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&ruleset->root_net_port, node)
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free_rule(freeme, LANDLOCK_KEY_NET_PORT);
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#endif /* IS_ENABLED(CONFIG_INET) */
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put_hierarchy(ruleset->hierarchy);
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kfree(ruleset);
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}
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void landlock_put_ruleset(struct landlock_ruleset *const ruleset)
|
|
{
|
|
might_sleep();
|
|
if (ruleset && refcount_dec_and_test(&ruleset->usage))
|
|
free_ruleset(ruleset);
|
|
}
|
|
|
|
static void free_ruleset_work(struct work_struct *const work)
|
|
{
|
|
struct landlock_ruleset *ruleset;
|
|
|
|
ruleset = container_of(work, struct landlock_ruleset, work_free);
|
|
free_ruleset(ruleset);
|
|
}
|
|
|
|
void landlock_put_ruleset_deferred(struct landlock_ruleset *const ruleset)
|
|
{
|
|
if (ruleset && refcount_dec_and_test(&ruleset->usage)) {
|
|
INIT_WORK(&ruleset->work_free, free_ruleset_work);
|
|
schedule_work(&ruleset->work_free);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* landlock_merge_ruleset - Merge a ruleset with a domain
|
|
*
|
|
* @parent: Parent domain.
|
|
* @ruleset: New ruleset to be merged.
|
|
*
|
|
* Returns the intersection of @parent and @ruleset, or returns @parent if
|
|
* @ruleset is empty, or returns a duplicate of @ruleset if @parent is empty.
|
|
*/
|
|
struct landlock_ruleset *
|
|
landlock_merge_ruleset(struct landlock_ruleset *const parent,
|
|
struct landlock_ruleset *const ruleset)
|
|
{
|
|
struct landlock_ruleset *new_dom;
|
|
u32 num_layers;
|
|
int err;
|
|
|
|
might_sleep();
|
|
if (WARN_ON_ONCE(!ruleset || parent == ruleset))
|
|
return ERR_PTR(-EINVAL);
|
|
|
|
if (parent) {
|
|
if (parent->num_layers >= LANDLOCK_MAX_NUM_LAYERS)
|
|
return ERR_PTR(-E2BIG);
|
|
num_layers = parent->num_layers + 1;
|
|
} else {
|
|
num_layers = 1;
|
|
}
|
|
|
|
/* Creates a new domain... */
|
|
new_dom = create_ruleset(num_layers);
|
|
if (IS_ERR(new_dom))
|
|
return new_dom;
|
|
new_dom->hierarchy =
|
|
kzalloc(sizeof(*new_dom->hierarchy), GFP_KERNEL_ACCOUNT);
|
|
if (!new_dom->hierarchy) {
|
|
err = -ENOMEM;
|
|
goto out_put_dom;
|
|
}
|
|
refcount_set(&new_dom->hierarchy->usage, 1);
|
|
|
|
/* ...as a child of @parent... */
|
|
err = inherit_ruleset(parent, new_dom);
|
|
if (err)
|
|
goto out_put_dom;
|
|
|
|
/* ...and including @ruleset. */
|
|
err = merge_ruleset(new_dom, ruleset);
|
|
if (err)
|
|
goto out_put_dom;
|
|
|
|
return new_dom;
|
|
|
|
out_put_dom:
|
|
landlock_put_ruleset(new_dom);
|
|
return ERR_PTR(err);
|
|
}
|
|
|
|
/*
|
|
* The returned access has the same lifetime as @ruleset.
|
|
*/
|
|
const struct landlock_rule *
|
|
landlock_find_rule(const struct landlock_ruleset *const ruleset,
|
|
const struct landlock_id id)
|
|
{
|
|
const struct rb_root *root;
|
|
const struct rb_node *node;
|
|
|
|
root = get_root((struct landlock_ruleset *)ruleset, id.type);
|
|
if (IS_ERR(root))
|
|
return NULL;
|
|
node = root->rb_node;
|
|
|
|
while (node) {
|
|
struct landlock_rule *this =
|
|
rb_entry(node, struct landlock_rule, node);
|
|
|
|
if (this->key.data == id.key.data)
|
|
return this;
|
|
if (this->key.data < id.key.data)
|
|
node = node->rb_right;
|
|
else
|
|
node = node->rb_left;
|
|
}
|
|
return NULL;
|
|
}
|
|
|
|
/*
|
|
* @layer_masks is read and may be updated according to the access request and
|
|
* the matching rule.
|
|
* @masks_array_size must be equal to ARRAY_SIZE(*layer_masks).
|
|
*
|
|
* Returns true if the request is allowed (i.e. relevant layer masks for the
|
|
* request are empty).
|
|
*/
|
|
bool landlock_unmask_layers(const struct landlock_rule *const rule,
|
|
const access_mask_t access_request,
|
|
layer_mask_t (*const layer_masks)[],
|
|
const size_t masks_array_size)
|
|
{
|
|
size_t layer_level;
|
|
|
|
if (!access_request || !layer_masks)
|
|
return true;
|
|
if (!rule)
|
|
return false;
|
|
|
|
/*
|
|
* An access is granted if, for each policy layer, at least one rule
|
|
* encountered on the pathwalk grants the requested access,
|
|
* regardless of its position in the layer stack. We must then check
|
|
* the remaining layers for each inode, from the first added layer to
|
|
* the last one. When there is multiple requested accesses, for each
|
|
* policy layer, the full set of requested accesses may not be granted
|
|
* by only one rule, but by the union (binary OR) of multiple rules.
|
|
* E.g. /a/b <execute> + /a <read> => /a/b <execute + read>
|
|
*/
|
|
for (layer_level = 0; layer_level < rule->num_layers; layer_level++) {
|
|
const struct landlock_layer *const layer =
|
|
&rule->layers[layer_level];
|
|
const layer_mask_t layer_bit = BIT_ULL(layer->level - 1);
|
|
const unsigned long access_req = access_request;
|
|
unsigned long access_bit;
|
|
bool is_empty;
|
|
|
|
/*
|
|
* Records in @layer_masks which layer grants access to each
|
|
* requested access.
|
|
*/
|
|
is_empty = true;
|
|
for_each_set_bit(access_bit, &access_req, masks_array_size) {
|
|
if (layer->access & BIT_ULL(access_bit))
|
|
(*layer_masks)[access_bit] &= ~layer_bit;
|
|
is_empty = is_empty && !(*layer_masks)[access_bit];
|
|
}
|
|
if (is_empty)
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
typedef access_mask_t
|
|
get_access_mask_t(const struct landlock_ruleset *const ruleset,
|
|
const u16 layer_level);
|
|
|
|
/**
|
|
* landlock_init_layer_masks - Initialize layer masks from an access request
|
|
*
|
|
* Populates @layer_masks such that for each access right in @access_request,
|
|
* the bits for all the layers are set where this access right is handled.
|
|
*
|
|
* @domain: The domain that defines the current restrictions.
|
|
* @access_request: The requested access rights to check.
|
|
* @layer_masks: It must contain %LANDLOCK_NUM_ACCESS_FS or
|
|
* %LANDLOCK_NUM_ACCESS_NET elements according to @key_type.
|
|
* @key_type: The key type to switch between access masks of different types.
|
|
*
|
|
* Returns: An access mask where each access right bit is set which is handled
|
|
* in any of the active layers in @domain.
|
|
*/
|
|
access_mask_t
|
|
landlock_init_layer_masks(const struct landlock_ruleset *const domain,
|
|
const access_mask_t access_request,
|
|
layer_mask_t (*const layer_masks)[],
|
|
const enum landlock_key_type key_type)
|
|
{
|
|
access_mask_t handled_accesses = 0;
|
|
size_t layer_level, num_access;
|
|
get_access_mask_t *get_access_mask;
|
|
|
|
switch (key_type) {
|
|
case LANDLOCK_KEY_INODE:
|
|
get_access_mask = landlock_get_fs_access_mask;
|
|
num_access = LANDLOCK_NUM_ACCESS_FS;
|
|
break;
|
|
|
|
#if IS_ENABLED(CONFIG_INET)
|
|
case LANDLOCK_KEY_NET_PORT:
|
|
get_access_mask = landlock_get_net_access_mask;
|
|
num_access = LANDLOCK_NUM_ACCESS_NET;
|
|
break;
|
|
#endif /* IS_ENABLED(CONFIG_INET) */
|
|
|
|
default:
|
|
WARN_ON_ONCE(1);
|
|
return 0;
|
|
}
|
|
|
|
memset(layer_masks, 0,
|
|
array_size(sizeof((*layer_masks)[0]), num_access));
|
|
|
|
/* An empty access request can happen because of O_WRONLY | O_RDWR. */
|
|
if (!access_request)
|
|
return 0;
|
|
|
|
/* Saves all handled accesses per layer. */
|
|
for (layer_level = 0; layer_level < domain->num_layers; layer_level++) {
|
|
const unsigned long access_req = access_request;
|
|
const access_mask_t access_mask =
|
|
get_access_mask(domain, layer_level);
|
|
unsigned long access_bit;
|
|
|
|
for_each_set_bit(access_bit, &access_req, num_access) {
|
|
if (BIT_ULL(access_bit) & access_mask) {
|
|
(*layer_masks)[access_bit] |=
|
|
BIT_ULL(layer_level);
|
|
handled_accesses |= BIT_ULL(access_bit);
|
|
}
|
|
}
|
|
}
|
|
return handled_accesses;
|
|
}
|