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// SPDX-License-Identifier: GPL-2.0-only
/*
* Landlock LSM - Object management
*
* Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net>
* Copyright © 2018-2020 ANSSI
*/
#include <linux/bug.h>
#include <linux/compiler_types.h>
#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/rcupdate.h>
#include <linux/refcount.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include "object.h"
struct landlock_object *landlock_create_object(
const struct landlock_object_underops *const underops,
void *const underobj)
{
struct landlock_object *new_object;
if (WARN_ON_ONCE(!underops || !underobj))
return ERR_PTR(-ENOENT);
new_object = kzalloc(sizeof(*new_object), GFP_KERNEL_ACCOUNT);
if (!new_object)
return ERR_PTR(-ENOMEM);
refcount_set(&new_object->usage, 1);
spin_lock_init(&new_object->lock);
new_object->underops = underops;
new_object->underobj = underobj;
return new_object;
}
/*
* The caller must own the object (i.e. thanks to object->usage) to safely put
* it.
*/
void landlock_put_object(struct landlock_object *const object)
{
/*
* The call to @object->underops->release(object) might sleep, e.g.
* because of iput().
*/
might_sleep();
if (!object)
return;
/*
* If the @object's refcount cannot drop to zero, we can just decrement
* the refcount without holding a lock. Otherwise, the decrement must
* happen under @object->lock for synchronization with things like
* get_inode_object().
*/
if (refcount_dec_and_lock(&object->usage, &object->lock)) {
__acquire(&object->lock);
/*
* With @object->lock initially held, remove the reference from
* @object->underobj to @object (if it still exists).
*/
object->underops->release(object);
kfree_rcu(object, rcu_free);
}
}
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