1 | // SPDX-License-Identifier: GPL-2.0-only |
---|---|
2 | /* |
3 | * Landlock LSM - Object management |
4 | * |
5 | * Copyright © 2016-2020 Mickaël Salaün <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 | |
20 | struct landlock_object * |
21 | landlock_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(error: -ENOENT); |
28 | new_object = kzalloc(size: sizeof(*new_object), GFP_KERNEL_ACCOUNT); |
29 | if (!new_object) |
30 | return ERR_PTR(error: -ENOMEM); |
31 | refcount_set(r: &new_object->usage, n: 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 | */ |
42 | void 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(r: &object->usage, lock: &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 |