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Message-Id: <20200224160215.4136-3-mic@digikod.net>
Date: Mon, 24 Feb 2020 17:02:07 +0100
From: Mickaël Salaün <mic@...ikod.net>
To: linux-kernel@...r.kernel.org
Cc: Mickaël Salaün <mic@...ikod.net>,
Al Viro <viro@...iv.linux.org.uk>,
Andy Lutomirski <luto@...capital.net>, Arnd Bergmann <arnd@...db.de>,
Casey Schaufler <casey@...aufler-ca.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
James Morris <jmorris@...ei.org>, Jann Horn <jann@...jh.net>,
Jonathan Corbet <corbet@....net>, Kees Cook <keescook@...omium.org>,
Michael Kerrisk <mtk.manpages@...il.com>,
Mickaël Salaün <mickael.salaun@....gouv.fr>,
"Serge E . Hallyn" <serge@...lyn.com>, Shuah Khan <shuah@...nel.org>,
Vincent Dagonneau <vincent.dagonneau@....gouv.fr>,
kernel-hardening@...ts.openwall.com, linux-api@...r.kernel.org,
linux-arch@...r.kernel.org, linux-doc@...r.kernel.org,
linux-fsdevel@...r.kernel.org, linux-kselftest@...r.kernel.org,
linux-security-module@...r.kernel.org, x86@...nel.org
Subject: [RFC PATCH v14 02/10] landlock: Add ruleset and domain management
A Landlock ruleset is mainly a red-black tree with Landlock rules as
nodes. This enables quick update and lookup to match a requested access
e.g., to a file. A ruleset is usable through a dedicated file
descriptor (cf. following commit adding the syscall) which enables a
process to build it by adding new rules.
A domain is a ruleset tied to a set of processes. This group of rules
defined the security policy enforced on these processes and their future
children. A domain can transition to a new domain which is the merge of
itself with a ruleset provided by the current process. This merge is
the intersection of all the constraints, which means that a process can
only gain more constraints over time.
Signed-off-by: Mickaël Salaün <mic@...ikod.net>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: James Morris <jmorris@...ei.org>
Cc: Kees Cook <keescook@...omium.org>
Cc: Serge E. Hallyn <serge@...lyn.com>
---
Changes since v13:
* New implementation, inspired by the previous inode eBPF map, but
agnostic to the underlying kernel object.
Previous version:
https://lore.kernel.org/lkml/20190721213116.23476-7-mic@digikod.net/
---
MAINTAINERS | 1 +
include/uapi/linux/landlock.h | 102 ++++++++
security/landlock/Makefile | 2 +-
security/landlock/ruleset.c | 460 ++++++++++++++++++++++++++++++++++
security/landlock/ruleset.h | 106 ++++++++
5 files changed, 670 insertions(+), 1 deletion(-)
create mode 100644 include/uapi/linux/landlock.h
create mode 100644 security/landlock/ruleset.c
create mode 100644 security/landlock/ruleset.h
diff --git a/MAINTAINERS b/MAINTAINERS
index 206f85768cd9..937257925e65 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -9366,6 +9366,7 @@ L: linux-security-module@...r.kernel.org
W: https://landlock.io
T: git https://github.com/landlock-lsm/linux.git
S: Supported
+F: include/uapi/linux/landlock.h
F: security/landlock/
K: landlock
K: LANDLOCK
diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h
new file mode 100644
index 000000000000..92760aca3645
--- /dev/null
+++ b/include/uapi/linux/landlock.h
@@ -0,0 +1,102 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ * Landlock - UAPI headers
+ *
+ * Copyright © 2017-2020 Mickaël Salaün <mic@...ikod.net>
+ * Copyright © 2018-2020 ANSSI
+ */
+
+#ifndef _UAPI__LINUX_LANDLOCK_H__
+#define _UAPI__LINUX_LANDLOCK_H__
+
+/**
+ * DOC: fs_access
+ *
+ * A set of actions on kernel objects may be defined by an attribute (e.g.
+ * &struct landlock_attr_path_beneath) and a bitmask of access.
+ *
+ * Filesystem flags
+ * ~~~~~~~~~~~~~~~~
+ *
+ * These flags enable to restrict a sandbox process to a set of of actions on
+ * files and directories. Files or directories opened before the sandboxing
+ * are not subject to these restrictions.
+ *
+ * - %LANDLOCK_ACCESS_FS_READ: Open or map a file with read access.
+ * - %LANDLOCK_ACCESS_FS_READDIR: List the content of a directory.
+ * - %LANDLOCK_ACCESS_FS_GETATTR: Read metadata of a file or a directory.
+ * - %LANDLOCK_ACCESS_FS_WRITE: Write to a file.
+ * - %LANDLOCK_ACCESS_FS_TRUNCATE: Truncate a file.
+ * - %LANDLOCK_ACCESS_FS_LOCK: Lock a file.
+ * - %LANDLOCK_ACCESS_FS_CHMOD: Change DAC permissions on a file or a
+ * directory.
+ * - %LANDLOCK_ACCESS_FS_CHOWN: Change the owner of a file or a directory.
+ * - %LANDLOCK_ACCESS_FS_CHGRP: Change the group of a file or a directory.
+ * - %LANDLOCK_ACCESS_FS_IOCTL: Send various command to a special file, cf.
+ * :manpage:`ioctl(2)`.
+ * - %LANDLOCK_ACCESS_FS_LINK_TO: Link a file into a directory.
+ * - %LANDLOCK_ACCESS_FS_RENAME_FROM: Rename a file or a directory.
+ * - %LANDLOCK_ACCESS_FS_RENAME_TO: Rename a file or a directory.
+ * - %LANDLOCK_ACCESS_FS_RMDIR: Remove an empty directory.
+ * - %LANDLOCK_ACCESS_FS_UNLINK: Remove a file.
+ * - %LANDLOCK_ACCESS_FS_MAKE_CHAR: Create a character device.
+ * - %LANDLOCK_ACCESS_FS_MAKE_DIR: Create a directory.
+ * - %LANDLOCK_ACCESS_FS_MAKE_REG: Create a regular file.
+ * - %LANDLOCK_ACCESS_FS_MAKE_SOCK: Create a UNIX domain socket.
+ * - %LANDLOCK_ACCESS_FS_MAKE_FIFO: Create a named pipe.
+ * - %LANDLOCK_ACCESS_FS_MAKE_BLOCK: Create a block device.
+ * - %LANDLOCK_ACCESS_FS_MAKE_SYM: Create a symbolic link.
+ * - %LANDLOCK_ACCESS_FS_EXECUTE: Execute a file.
+ * - %LANDLOCK_ACCESS_FS_CHROOT: Change the root directory of the current
+ * process.
+ * - %LANDLOCK_ACCESS_FS_OPEN: Open a file or a directory. This flag is set
+ * for any actions (e.g. read, write, execute) requested to open a file or
+ * directory.
+ * - %LANDLOCK_ACCESS_FS_MAP: Map a file. This flag is set for any actions
+ * (e.g. read, write, execute) requested to map a file.
+ *
+ * There is currently no restriction for directory walking e.g.,
+ * :manpage:`chdir(2)`.
+ */
+#define LANDLOCK_ACCESS_FS_READ (1ULL << 0)
+#define LANDLOCK_ACCESS_FS_READDIR (1ULL << 1)
+#define LANDLOCK_ACCESS_FS_GETATTR (1ULL << 2)
+#define LANDLOCK_ACCESS_FS_WRITE (1ULL << 3)
+#define LANDLOCK_ACCESS_FS_TRUNCATE (1ULL << 4)
+#define LANDLOCK_ACCESS_FS_LOCK (1ULL << 5)
+#define LANDLOCK_ACCESS_FS_CHMOD (1ULL << 6)
+#define LANDLOCK_ACCESS_FS_CHOWN (1ULL << 7)
+#define LANDLOCK_ACCESS_FS_CHGRP (1ULL << 8)
+#define LANDLOCK_ACCESS_FS_IOCTL (1ULL << 9)
+#define LANDLOCK_ACCESS_FS_LINK_TO (1ULL << 10)
+#define LANDLOCK_ACCESS_FS_RENAME_FROM (1ULL << 11)
+#define LANDLOCK_ACCESS_FS_RENAME_TO (1ULL << 12)
+#define LANDLOCK_ACCESS_FS_RMDIR (1ULL << 13)
+#define LANDLOCK_ACCESS_FS_UNLINK (1ULL << 14)
+#define LANDLOCK_ACCESS_FS_MAKE_CHAR (1ULL << 15)
+#define LANDLOCK_ACCESS_FS_MAKE_DIR (1ULL << 16)
+#define LANDLOCK_ACCESS_FS_MAKE_REG (1ULL << 17)
+#define LANDLOCK_ACCESS_FS_MAKE_SOCK (1ULL << 18)
+#define LANDLOCK_ACCESS_FS_MAKE_FIFO (1ULL << 19)
+#define LANDLOCK_ACCESS_FS_MAKE_BLOCK (1ULL << 20)
+#define LANDLOCK_ACCESS_FS_MAKE_SYM (1ULL << 21)
+#define LANDLOCK_ACCESS_FS_EXECUTE (1ULL << 22)
+#define LANDLOCK_ACCESS_FS_CHROOT (1ULL << 23)
+#define LANDLOCK_ACCESS_FS_OPEN (1ULL << 24)
+#define LANDLOCK_ACCESS_FS_MAP (1ULL << 25)
+
+/*
+ * Potential future access:
+ * - %LANDLOCK_ACCESS_FS_SETATTR
+ * - %LANDLOCK_ACCESS_FS_APPEND
+ * - %LANDLOCK_ACCESS_FS_LINK_FROM
+ * - %LANDLOCK_ACCESS_FS_MOUNT_FROM
+ * - %LANDLOCK_ACCESS_FS_MOUNT_TO
+ * - %LANDLOCK_ACCESS_FS_UNMOUNT
+ * - %LANDLOCK_ACCESS_FS_TRANSFER
+ * - %LANDLOCK_ACCESS_FS_RECEIVE
+ * - %LANDLOCK_ACCESS_FS_CHDIR
+ * - %LANDLOCK_ACCESS_FS_FCNTL
+ */
+
+#endif /* _UAPI__LINUX_LANDLOCK_H__ */
diff --git a/security/landlock/Makefile b/security/landlock/Makefile
index cb6deefbf4c0..d846eba445bb 100644
--- a/security/landlock/Makefile
+++ b/security/landlock/Makefile
@@ -1,3 +1,3 @@
obj-$(CONFIG_SECURITY_LANDLOCK) := landlock.o
-landlock-y := object.o
+landlock-y := object.o ruleset.o
diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
new file mode 100644
index 000000000000..5ec013a4188d
--- /dev/null
+++ b/security/landlock/ruleset.c
@@ -0,0 +1,460 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Landlock LSM - Ruleset management
+ *
+ * Copyright © 2016-2020 Mickaël Salaün <mic@...ikod.net>
+ * Copyright © 2018-2020 ANSSI
+ */
+
+#include <linux/bug.h>
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/rbtree.h>
+#include <linux/rcupdate.h>
+#include <linux/refcount.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/workqueue.h>
+
+#include "object.h"
+#include "ruleset.h"
+
+static struct landlock_ruleset *create_ruleset(void)
+{
+ struct landlock_ruleset *ruleset;
+
+ ruleset = kzalloc(sizeof(*ruleset), GFP_KERNEL);
+ if (!ruleset)
+ return ERR_PTR(-ENOMEM);
+ refcount_set(&ruleset->usage, 1);
+ mutex_init(&ruleset->lock);
+ atomic_set(&ruleset->nb_rules, 0);
+ ruleset->root = RB_ROOT;
+ return ruleset;
+}
+
+struct landlock_ruleset *landlock_create_ruleset(u64 fs_access_mask)
+{
+ struct landlock_ruleset *ruleset;
+
+ /* Safely handles 32-bits conversion. */
+ BUILD_BUG_ON(!__same_type(fs_access_mask, _LANDLOCK_ACCESS_FS_LAST));
+
+ /* Checks content. */
+ if ((fs_access_mask | _LANDLOCK_ACCESS_FS_MASK) !=
+ _LANDLOCK_ACCESS_FS_MASK)
+ return ERR_PTR(-EINVAL);
+ /* Informs about useless ruleset. */
+ if (!fs_access_mask)
+ return ERR_PTR(-ENOMSG);
+ ruleset = create_ruleset();
+ if (!IS_ERR(ruleset))
+ ruleset->fs_access_mask = fs_access_mask;
+ return ruleset;
+}
+
+/*
+ * The underlying kernel object must be held by the caller.
+ */
+static struct landlock_ruleset_elem *create_ruleset_elem(
+ struct landlock_object *object)
+{
+ struct landlock_ruleset_elem *ruleset_elem;
+
+ ruleset_elem = kzalloc(sizeof(*ruleset_elem), GFP_KERNEL);
+ if (!ruleset_elem)
+ return ERR_PTR(-ENOMEM);
+ RB_CLEAR_NODE(&ruleset_elem->node);
+ RCU_INIT_POINTER(ruleset_elem->ref.object, object);
+ return ruleset_elem;
+}
+
+static struct landlock_rule *create_rule(struct landlock_object *object,
+ struct landlock_access *access)
+{
+ struct landlock_rule *new_rule;
+
+ if (WARN_ON_ONCE(!object))
+ return ERR_PTR(-EFAULT);
+ if (WARN_ON_ONCE(!access))
+ return ERR_PTR(-EFAULT);
+ new_rule = kzalloc(sizeof(*new_rule), GFP_KERNEL);
+ if (!new_rule)
+ return ERR_PTR(-ENOMEM);
+ refcount_set(&new_rule->usage, 1);
+ INIT_LIST_HEAD(&new_rule->list);
+ new_rule->access = *access;
+
+ spin_lock(&object->lock);
+ list_add_tail(&new_rule->list, &object->rules);
+ spin_unlock(&object->lock);
+ return new_rule;
+}
+
+/*
+ * An inserted rule can not be removed, only disabled (cf. struct
+ * landlock_ruleset_elem).
+ *
+ * The underlying kernel object must be held by the caller.
+ *
+ * @rule: Allocated struct owned by this function. The caller must hold the
+ * underlying kernel object (e.g., with a FD).
+ */
+int landlock_insert_ruleset_rule(struct landlock_ruleset *ruleset,
+ struct landlock_object *object, struct landlock_access *access,
+ struct landlock_rule *rule)
+{
+ struct rb_node **new;
+ struct rb_node *parent = NULL;
+ struct landlock_ruleset_elem *ruleset_elem;
+ struct landlock_rule *new_rule;
+
+ might_sleep();
+ /* Accesses may be set when creating a new rule. */
+ if (rule) {
+ if (WARN_ON_ONCE(access))
+ return -EINVAL;
+ } else {
+ if (WARN_ON_ONCE(!access))
+ return -EFAULT;
+ }
+
+ lockdep_assert_held(&ruleset->lock);
+ new = &(ruleset->root.rb_node);
+ while (*new) {
+ struct landlock_ruleset_elem *this = rb_entry(*new,
+ struct landlock_ruleset_elem, node);
+ uintptr_t this_object;
+ struct landlock_rule *this_rule;
+ struct landlock_access new_access;
+
+ this_object = (uintptr_t)rcu_access_pointer(this->ref.object);
+ if (this_object != (uintptr_t)object) {
+ parent = *new;
+ if (this_object < (uintptr_t)object)
+ new = &((*new)->rb_right);
+ else
+ new = &((*new)->rb_left);
+ continue;
+ }
+
+ /* Do not increment ruleset->nb_rules. */
+ this_rule = rcu_dereference_protected(this->ref.rule,
+ lockdep_is_held(&ruleset->lock));
+ /*
+ * Checks if it is a new object with the same address as a
+ * previously disabled one. There is no possible race
+ * condition because an object can not be disabled/deleted
+ * while being inserted in this tree.
+ */
+ if (landlock_rule_is_disabled(this_rule)) {
+ if (rule) {
+ refcount_inc(&rule->usage);
+ new_rule = rule;
+ } else {
+ /* Replace the previous rule with a new one. */
+ new_rule = create_rule(object, access);
+ if (IS_ERR(new_rule))
+ return PTR_ERR(new_rule);
+ }
+ rcu_assign_pointer(this->ref.rule, new_rule);
+ landlock_put_rule(object, this_rule);
+ return 0;
+ }
+
+ /* this_rule is potentially enabled. */
+ if (refcount_read(&this_rule->usage) == 1) {
+ if (rule) {
+ /* merge rule: intersection of access rights */
+ this_rule->access.self &= rule->access.self;
+ this_rule->access.beneath &=
+ rule->access.beneath;
+ } else {
+ /* extend rule: union of access rights */
+ this_rule->access.self |= access->self;
+ this_rule->access.beneath |= access->beneath;
+ }
+ return 0;
+ }
+
+ /*
+ * If this_rule is shared with another ruleset, then create a
+ * new object rule.
+ */
+ if (rule) {
+ /* Merging a rule means an intersection of access. */
+ new_access.self = this_rule->access.self &
+ rule->access.self;
+ new_access.beneath = this_rule->access.beneath &
+ rule->access.beneath;
+ } else {
+ /* Extending a rule means a union of access. */
+ new_access.self = this_rule->access.self |
+ access->self;
+ new_access.beneath = this_rule->access.self |
+ access->beneath;
+ }
+ new_rule = create_rule(object, &new_access);
+ if (IS_ERR(new_rule))
+ return PTR_ERR(new_rule);
+ rcu_assign_pointer(this->ref.rule, new_rule);
+ landlock_put_rule(object, this_rule);
+ return 0;
+ }
+
+ /* There is no match for @object. */
+ ruleset_elem = create_ruleset_elem(object);
+ if (IS_ERR(ruleset_elem))
+ return PTR_ERR(ruleset_elem);
+ if (rule) {
+ refcount_inc(&rule->usage);
+ new_rule = rule;
+ } else {
+ new_rule = create_rule(object, access);
+ if (IS_ERR(new_rule)) {
+ kfree(ruleset_elem);
+ return PTR_ERR(new_rule);
+ }
+ }
+ RCU_INIT_POINTER(ruleset_elem->ref.rule, new_rule);
+ /*
+ * Because of the missing RCU context annotation in struct rb_node,
+ * Sparse emits a warning when encountering rb_link_node_rcu(), but
+ * this function call is still safe.
+ */
+ rb_link_node_rcu(&ruleset_elem->node, parent, new);
+ rb_insert_color(&ruleset_elem->node, &ruleset->root);
+ atomic_inc(&ruleset->nb_rules);
+ return 0;
+}
+
+static int merge_ruleset(struct landlock_ruleset *dst,
+ struct landlock_ruleset *src)
+{
+ struct rb_node *node;
+ int err = 0;
+
+ might_sleep();
+ if (!src)
+ return 0;
+ if (WARN_ON_ONCE(!dst))
+ return -EFAULT;
+ if (WARN_ON_ONCE(!dst->hierarchy))
+ return -EINVAL;
+
+ mutex_lock(&dst->lock);
+ mutex_lock_nested(&src->lock, 1);
+ dst->fs_access_mask |= src->fs_access_mask;
+ for (node = rb_first(&src->root); node; node = rb_next(node)) {
+ struct landlock_ruleset_elem *elem = rb_entry(node,
+ struct landlock_ruleset_elem, node);
+ struct landlock_object *object =
+ rcu_dereference_protected(elem->ref.object,
+ lockdep_is_held(&src->lock));
+ struct landlock_rule *rule =
+ rcu_dereference_protected(elem->ref.rule,
+ lockdep_is_held(&src->lock));
+
+ err = landlock_insert_ruleset_rule(dst, object, NULL, rule);
+ if (err)
+ goto out_unlock;
+ }
+
+out_unlock:
+ mutex_unlock(&src->lock);
+ mutex_unlock(&dst->lock);
+ return err;
+}
+
+void landlock_get_ruleset(struct landlock_ruleset *ruleset)
+{
+ if (!ruleset)
+ return;
+ refcount_inc(&ruleset->usage);
+}
+
+static void put_hierarchy(struct landlock_hierarchy *hierarchy)
+{
+ if (hierarchy && refcount_dec_and_test(&hierarchy->usage))
+ kfree(hierarchy);
+}
+
+static void put_ruleset(struct landlock_ruleset *ruleset)
+{
+ struct rb_node *orig;
+
+ might_sleep();
+ for (orig = rb_first(&ruleset->root); orig; orig = rb_next(orig)) {
+ struct landlock_ruleset_elem *freeme;
+ struct landlock_object *object;
+ struct landlock_rule *rule;
+
+ freeme = rb_entry(orig, struct landlock_ruleset_elem, node);
+ object = rcu_dereference_protected(freeme->ref.object,
+ refcount_read(&ruleset->usage) == 0);
+ rule = rcu_dereference_protected(freeme->ref.rule,
+ refcount_read(&ruleset->usage) == 0);
+ landlock_put_rule(object, rule);
+ kfree_rcu(freeme, rcu_free);
+ }
+ put_hierarchy(ruleset->hierarchy);
+ kfree_rcu(ruleset, rcu_free);
+}
+
+void landlock_put_ruleset(struct landlock_ruleset *ruleset)
+{
+ might_sleep();
+ if (ruleset && refcount_dec_and_test(&ruleset->usage))
+ put_ruleset(ruleset);
+}
+
+static void put_ruleset_work(struct work_struct *work)
+{
+ struct landlock_ruleset *ruleset;
+
+ ruleset = container_of(work, struct landlock_ruleset, work_put);
+ /*
+ * Clean up rcu_free because of previous use through union work_put.
+ * ruleset->rcu_free.func is already NULLed by __rcu_reclaim().
+ */
+ ruleset->rcu_free.next = NULL;
+ put_ruleset(ruleset);
+}
+
+void landlock_put_ruleset_enqueue(struct landlock_ruleset *ruleset)
+{
+ if (ruleset && refcount_dec_and_test(&ruleset->usage)) {
+ INIT_WORK(&ruleset->work_put, put_ruleset_work);
+ schedule_work(&ruleset->work_put);
+ }
+}
+
+static bool clean_ref(struct landlock_ref *ref)
+{
+ struct landlock_rule *rule;
+
+ rule = rcu_dereference(ref->rule);
+ if (!rule)
+ return false;
+ if (!landlock_rule_is_disabled(rule))
+ return false;
+ rcu_assign_pointer(ref->rule, NULL);
+ /*
+ * landlock_put_rule() will not sleep because we already checked
+ * !landlock_rule_is_disabled(rule).
+ */
+ landlock_put_rule(rcu_dereference(ref->object), rule);
+ return true;
+}
+
+static void clean_ruleset(struct landlock_ruleset *ruleset)
+{
+ struct rb_node *node;
+
+ if (!ruleset)
+ return;
+ /* We must lock the ruleset to not have a wrong nb_rules counter. */
+ mutex_lock(&ruleset->lock);
+ rcu_read_lock();
+ for (node = rb_first(&ruleset->root); node; node = rb_next(node)) {
+ struct landlock_ruleset_elem *elem = rb_entry(node,
+ struct landlock_ruleset_elem, node);
+
+ if (clean_ref(&elem->ref)) {
+ rb_erase(&elem->node, &ruleset->root);
+ kfree_rcu(elem, rcu_free);
+ atomic_dec(&ruleset->nb_rules);
+ }
+ }
+ rcu_read_unlock();
+ mutex_unlock(&ruleset->lock);
+}
+
+/*
+ * Creates a new ruleset, merged of @parent and @ruleset, or return @parent if
+ * @ruleset is empty. If @parent is empty, return a duplicate of @ruleset.
+ *
+ * @parent: Must not be modified (i.e. locked or read-only).
+ */
+struct landlock_ruleset *landlock_merge_ruleset(
+ struct landlock_ruleset *parent,
+ struct landlock_ruleset *ruleset)
+{
+ struct landlock_ruleset *new_dom;
+ int err;
+
+ might_sleep();
+ /* Opportunistically put disabled rules. */
+ clean_ruleset(ruleset);
+
+ if (parent && WARN_ON_ONCE(!parent->hierarchy))
+ return ERR_PTR(-EINVAL);
+ if (!ruleset || atomic_read(&ruleset->nb_rules) == 0 ||
+ parent == ruleset) {
+ landlock_get_ruleset(parent);
+ return parent;
+ }
+
+ new_dom = create_ruleset();
+ if (IS_ERR(new_dom))
+ return new_dom;
+ new_dom->hierarchy = kzalloc(sizeof(*new_dom->hierarchy), GFP_KERNEL);
+ if (!new_dom->hierarchy) {
+ landlock_put_ruleset(new_dom);
+ return ERR_PTR(-ENOMEM);
+ }
+ refcount_set(&new_dom->hierarchy->usage, 1);
+
+ if (parent) {
+ new_dom->hierarchy->parent = parent->hierarchy;
+ refcount_inc(&parent->hierarchy->usage);
+ err = merge_ruleset(new_dom, parent);
+ if (err) {
+ landlock_put_ruleset(new_dom);
+ return ERR_PTR(err);
+ }
+ }
+ err = merge_ruleset(new_dom, ruleset);
+ if (err) {
+ landlock_put_ruleset(new_dom);
+ return ERR_PTR(err);
+ }
+ return new_dom;
+}
+
+/*
+ * The return pointer must only be used in a RCU-read block.
+ */
+const struct landlock_access *landlock_find_access(
+ const struct landlock_ruleset *ruleset,
+ const struct landlock_object *object)
+{
+ struct rb_node *node;
+
+ WARN_ON_ONCE(!rcu_read_lock_held());
+ if (!object)
+ return NULL;
+ node = ruleset->root.rb_node;
+ while (node) {
+ struct landlock_ruleset_elem *this = rb_entry(node,
+ struct landlock_ruleset_elem, node);
+ uintptr_t this_object =
+ (uintptr_t)rcu_access_pointer(this->ref.object);
+
+ if (this_object == (uintptr_t)object) {
+ struct landlock_rule *rule;
+
+ rule = rcu_dereference(this->ref.rule);
+ if (!landlock_rule_is_disabled(rule))
+ return &rule->access;
+ return NULL;
+ }
+ if (this_object < (uintptr_t)object)
+ node = node->rb_right;
+ else
+ node = node->rb_left;
+ }
+ return NULL;
+}
diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
new file mode 100644
index 000000000000..afc88dbb8b4b
--- /dev/null
+++ b/security/landlock/ruleset.h
@@ -0,0 +1,106 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Landlock LSM - Ruleset management
+ *
+ * Copyright © 2016-2020 Mickaël Salaün <mic@...ikod.net>
+ * Copyright © 2018-2020 ANSSI
+ */
+
+#ifndef _SECURITY_LANDLOCK_RULESET_H
+#define _SECURITY_LANDLOCK_RULESET_H
+
+#include <linux/compiler.h>
+#include <linux/mutex.h>
+#include <linux/poison.h>
+#include <linux/rbtree.h>
+#include <linux/rcupdate.h>
+#include <linux/refcount.h>
+#include <linux/types.h>
+#include <linux/workqueue.h>
+#include <uapi/linux/landlock.h>
+
+#include "object.h"
+
+#define _LANDLOCK_ACCESS_FS_LAST LANDLOCK_ACCESS_FS_MAP
+#define _LANDLOCK_ACCESS_FS_MASK ((_LANDLOCK_ACCESS_FS_LAST << 1) - 1)
+
+struct landlock_ref {
+ /*
+ * @object: Identify a kernel object (e.g. an inode). This is used as
+ * a key for a ruleset tree (cf. struct landlock_ruleset_elem). This
+ * pointer is set once and never modified. It may point to a deleted
+ * object and should then be dereferenced with great care, thanks to a
+ * call to landlock_rule_is_disabled(@rule) from inside an RCU-read
+ * block, cf. landlock_put_rule().
+ */
+ struct landlock_object __rcu *object;
+ /*
+ * @rule: Ties a rule to an object. Set once with an allocated rule,
+ * but can be NULLed if the rule is disabled.
+ */
+ struct landlock_rule __rcu *rule;
+};
+
+/*
+ * Red-black tree element used in a landlock_ruleset.
+ */
+struct landlock_ruleset_elem {
+ struct landlock_ref ref;
+ struct rb_node node;
+ struct rcu_head rcu_free;
+};
+
+/*
+ * Enable hierarchy identification even when a parent domain vanishes. This is
+ * needed for the ptrace protection.
+ */
+struct landlock_hierarchy {
+ struct landlock_hierarchy *parent;
+ refcount_t usage;
+};
+
+/*
+ * Kernel representation of a ruleset. This data structure must contains
+ * unique entries, be updatable, and quick to match an object.
+ */
+struct landlock_ruleset {
+ /*
+ * @fs_access_mask: Contains the subset of filesystem actions which are
+ * restricted by a ruleset. This is used when merging rulesets and for
+ * userspace backward compatibility (i.e. future-proof). Set once and
+ * never changed for the lifetime of the ruleset.
+ */
+ u32 fs_access_mask;
+ struct landlock_hierarchy *hierarchy;
+ refcount_t usage;
+ union {
+ struct rcu_head rcu_free;
+ struct work_struct work_put;
+ };
+ struct mutex lock;
+ atomic_t nb_rules;
+ /*
+ * @root: Red-black tree containing landlock_ruleset_elem nodes.
+ */
+ struct rb_root root;
+};
+
+struct landlock_ruleset *landlock_create_ruleset(u64 fs_access_mask);
+
+void landlock_get_ruleset(struct landlock_ruleset *ruleset);
+void landlock_put_ruleset(struct landlock_ruleset *ruleset);
+void landlock_put_ruleset_enqueue(struct landlock_ruleset *ruleset);
+
+int landlock_insert_ruleset_rule(struct landlock_ruleset *ruleset,
+ struct landlock_object *object, struct landlock_access *access,
+ struct landlock_rule *rule);
+
+struct landlock_ruleset *landlock_merge_ruleset(
+ struct landlock_ruleset *domain,
+ struct landlock_ruleset *ruleset);
+
+const struct landlock_access *landlock_find_access(
+ const struct landlock_ruleset *ruleset,
+ const struct landlock_object *object);
+
+#endif /* _SECURITY_LANDLOCK_RULESET_H */
--
2.25.0
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