92 lines
2.8 KiB
C
92 lines
2.8 KiB
C
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/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Landlock LSM - Object 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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#ifndef _SECURITY_LANDLOCK_OBJECT_H
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#define _SECURITY_LANDLOCK_OBJECT_H
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#include <linux/compiler_types.h>
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#include <linux/refcount.h>
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#include <linux/spinlock.h>
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struct landlock_object;
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/**
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* struct landlock_object_underops - Operations on an underlying object
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*/
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struct landlock_object_underops {
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/**
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* @release: Releases the underlying object (e.g. iput() for an inode).
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*/
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void (*release)(struct landlock_object *const object)
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__releases(object->lock);
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};
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/**
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* struct landlock_object - Security blob tied to a kernel object
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*
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* The goal of this structure is to enable to tie a set of ephemeral access
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* rights (pertaining to different domains) to a kernel object (e.g an inode)
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* in a safe way. This implies to handle concurrent use and modification.
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*
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* The lifetime of a &struct landlock_object depends on the rules referring to
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* it.
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*/
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struct landlock_object {
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/**
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* @usage: This counter is used to tie an object to the rules matching
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* it or to keep it alive while adding a new rule. If this counter
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* reaches zero, this struct must not be modified, but this counter can
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* still be read from within an RCU read-side critical section. When
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* adding a new rule to an object with a usage counter of zero, we must
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* wait until the pointer to this object is set to NULL (or recycled).
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*/
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refcount_t usage;
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/**
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* @lock: Protects against concurrent modifications. This lock must be
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* held from the time @usage drops to zero until any weak references
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* from @underobj to this object have been cleaned up.
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*
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* Lock ordering: inode->i_lock nests inside this.
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*/
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spinlock_t lock;
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/**
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* @underobj: Used when cleaning up an object and to mark an object as
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* tied to its underlying kernel structure. This pointer is protected
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* by @lock. Cf. landlock_release_inodes() and release_inode().
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*/
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void *underobj;
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union {
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/**
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* @rcu_free: Enables lockless use of @usage, @lock and
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* @underobj from within an RCU read-side critical section.
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* @rcu_free and @underops are only used by
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* landlock_put_object().
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*/
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struct rcu_head rcu_free;
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/**
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* @underops: Enables landlock_put_object() to release the
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* underlying object (e.g. inode).
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*/
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const struct landlock_object_underops *underops;
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};
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};
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struct landlock_object *
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landlock_create_object(const struct landlock_object_underops *const underops,
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void *const underobj);
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void landlock_put_object(struct landlock_object *const object);
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static inline void landlock_get_object(struct landlock_object *const object)
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{
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if (object)
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refcount_inc(&object->usage);
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}
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#endif /* _SECURITY_LANDLOCK_OBJECT_H */
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