// 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_obj(*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);
        }
}