1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Landlock LSM - Object management
4 *
5 * Copyright �� 2016-2020 Micka��l Sala��n <mic@digikod.net>
6 * Copyright �� 2018-2020 ANSSI
7 */
8
9#include <linux/bug.h>
10#include <linux/compiler_types.h>
11#include <linux/err.h>
12#include <linux/kernel.h>
13#include <linux/rcupdate.h>
14#include <linux/refcount.h>
15#include <linux/slab.h>
16#include <linux/spinlock.h>
17
18#include "object.h"
19
20struct landlock_object *
21landlock_create_object(const struct landlock_object_underops *const underops,
22		       void *const underobj)
23{
24	struct landlock_object *new_object;
25
26	if (WARN_ON_ONCE(!underops || !underobj))
27		return ERR_PTR(-ENOENT);
28	new_object = kzalloc(sizeof(*new_object), GFP_KERNEL_ACCOUNT);
29	if (!new_object)
30		return ERR_PTR(-ENOMEM);
31	refcount_set(&new_object->usage, 1);
32	spin_lock_init(&new_object->lock);
33	new_object->underops = underops;
34	new_object->underobj = underobj;
35	return new_object;
36}
37
38/*
39 * The caller must own the object (i.e. thanks to object->usage) to safely put
40 * it.
41 */
42void landlock_put_object(struct landlock_object *const object)
43{
44	/*
45	 * The call to @object->underops->release(object) might sleep, e.g.
46	 * because of iput().
47	 */
48	might_sleep();
49	if (!object)
50		return;
51
52	/*
53	 * If the @object's refcount cannot drop to zero, we can just decrement
54	 * the refcount without holding a lock. Otherwise, the decrement must
55	 * happen under @object->lock for synchronization with things like
56	 * get_inode_object().
57	 */
58	if (refcount_dec_and_lock(&object->usage, &object->lock)) {
59		__acquire(&object->lock);
60		/*
61		 * With @object->lock initially held, remove the reference from
62		 * @object->underobj to @object (if it still exists).
63		 */
64		object->underops->release(object);
65		kfree_rcu(object, rcu_free);
66	}
67}
68