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1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 * Landlock - Access types and helpers
4 *
5 * Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net>
6 * Copyright © 2018-2020 ANSSI
7 * Copyright © 2024-2025 Microsoft Corporation
8 */
9
10#ifndef _SECURITY_LANDLOCK_ACCESS_H
11#define _SECURITY_LANDLOCK_ACCESS_H
12
13#include <linux/bitops.h>
14#include <linux/build_bug.h>
15#include <linux/kernel.h>
16#include <uapi/linux/landlock.h>
17
18#include "limits.h"
19
20/*
21 * All access rights that are denied by default whether they are handled or not
22 * by a ruleset/layer. This must be ORed with all ruleset->access_masks[]
23 * entries when we need to get the absolute handled access masks, see
24 * landlock_upgrade_handled_access_masks().
25 */
26/* clang-format off */
27#define _LANDLOCK_ACCESS_FS_INITIALLY_DENIED ( \
28 LANDLOCK_ACCESS_FS_REFER)
29/* clang-format on */
30
31/* clang-format off */
32#define _LANDLOCK_ACCESS_FS_OPTIONAL ( \
33 LANDLOCK_ACCESS_FS_TRUNCATE | \
34 LANDLOCK_ACCESS_FS_IOCTL_DEV)
35/* clang-format on */
36
37typedef u16 access_mask_t;
38
39/* Makes sure all filesystem access rights can be stored. */
40static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_FS);
41/* Makes sure all network access rights can be stored. */
42static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_NET);
43/* Makes sure all scoped rights can be stored. */
44static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_SCOPE);
45/* Makes sure for_each_set_bit() and for_each_clear_bit() calls are OK. */
46static_assert(sizeof(unsigned long) >= sizeof(access_mask_t));
47
48/* Ruleset access masks. */
49struct access_masks {
50 access_mask_t fs : LANDLOCK_NUM_ACCESS_FS;
51 access_mask_t net : LANDLOCK_NUM_ACCESS_NET;
52 access_mask_t scope : LANDLOCK_NUM_SCOPE;
53};
54
55union access_masks_all {
56 struct access_masks masks;
57 u32 all;
58};
59
60/* Makes sure all fields are covered. */
61static_assert(sizeof(typeof_member(union access_masks_all, masks)) ==
62 sizeof(typeof_member(union access_masks_all, all)));
63
64typedef u16 layer_mask_t;
65
66/* Makes sure all layers can be checked. */
67static_assert(BITS_PER_TYPE(layer_mask_t) >= LANDLOCK_MAX_NUM_LAYERS);
68
69/*
70 * Tracks domains responsible of a denied access. This is required to avoid
71 * storing in each object the full layer_masks[] required by update_request().
72 */
73typedef u8 deny_masks_t;
74
75/*
76 * Makes sure all optional access rights can be tied to a layer index (cf.
77 * get_deny_mask).
78 */
79static_assert(BITS_PER_TYPE(deny_masks_t) >=
80 (HWEIGHT(LANDLOCK_MAX_NUM_LAYERS - 1) *
81 HWEIGHT(_LANDLOCK_ACCESS_FS_OPTIONAL)));
82
83/* LANDLOCK_MAX_NUM_LAYERS must be a power of two (cf. deny_masks_t assert). */
84static_assert(HWEIGHT(LANDLOCK_MAX_NUM_LAYERS) == 1);
85
86/* Upgrades with all initially denied by default access rights. */
87static inline struct access_masks
88landlock_upgrade_handled_access_masks(struct access_masks access_masks)
89{
90 /*
91 * All access rights that are denied by default whether they are
92 * explicitly handled or not.
93 */
94 if (access_masks.fs)
95 access_masks.fs |= _LANDLOCK_ACCESS_FS_INITIALLY_DENIED;
96
97 return access_masks;
98}
99
100#endif /* _SECURITY_LANDLOCK_ACCESS_H */