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90945448 MS |
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 | ||
06a1c40a MS |
20 | struct landlock_object * |
21 | landlock_create_object(const struct landlock_object_underops *const underops, | |
22 | void *const underobj) | |
90945448 MS |
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 | */ | |
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(&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 | } |