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@xxxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx> Cc: James Morris <jmorris@xxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Serge E. Hallyn <serge@xxxxxxxxxx> --- 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@xxxxxxxxxxx/ --- 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@xxxxxxxxxxxxxxx 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@xxxxxxxxxxx> + * 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@xxxxxxxxxxx> + * 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@xxxxxxxxxxx> + * 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
