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 37 typedef u16 access_mask_t; 38 39 /* Makes sure all filesystem access rights can be stored. */ 40 static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_FS); 41 /* Makes sure all network access rights can be stored. */ 42 static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_NET); 43 /* Makes sure all scoped rights can be stored. */ 44 static_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. */ 46 static_assert(sizeof(unsigned long) >= sizeof(access_mask_t)); 47 48 /* Ruleset access masks. */ 49 struct 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 55 union access_masks_all { 56 struct access_masks masks; 57 u32 all; 58 }; 59 60 /* Makes sure all fields are covered. */ 61 static_assert(sizeof(typeof_member(union access_masks_all, masks)) == 62 sizeof(typeof_member(union access_masks_all, all))); 63 64 /** 65 * struct layer_access_masks - A boolean matrix of layers and access rights 66 * 67 * This has a bit for each combination of layer numbers and access rights. 68 * During access checks, it is used to represent the access rights for each 69 * layer which still need to be fulfilled. When all bits are 0, the access 70 * request is considered to be fulfilled. 71 */ 72 struct layer_access_masks { 73 /** 74 * @access: The unfulfilled access rights for each layer. 75 */ 76 access_mask_t access[LANDLOCK_MAX_NUM_LAYERS]; 77 }; 78 79 /* 80 * Tracks domains responsible of a denied access. This avoids storing in each 81 * object the full matrix of per-layer unfulfilled access rights, which is 82 * required by update_request(). 83 * 84 * Each nibble represents the layer index of the newest layer which denied a 85 * certain access right. For file system access rights, the upper four bits are 86 * the index of the layer which denies LANDLOCK_ACCESS_FS_IOCTL_DEV and the 87 * lower nibble represents LANDLOCK_ACCESS_FS_TRUNCATE. 88 */ 89 typedef u8 deny_masks_t; 90 91 /* 92 * Makes sure all optional access rights can be tied to a layer index (cf. 93 * get_deny_mask). 94 */ 95 static_assert(BITS_PER_TYPE(deny_masks_t) >= 96 (HWEIGHT(LANDLOCK_MAX_NUM_LAYERS - 1) * 97 HWEIGHT(_LANDLOCK_ACCESS_FS_OPTIONAL))); 98 99 /* LANDLOCK_MAX_NUM_LAYERS must be a power of two (cf. deny_masks_t assert). */ 100 static_assert(HWEIGHT(LANDLOCK_MAX_NUM_LAYERS) == 1); 101 102 /* Upgrades with all initially denied by default access rights. */ 103 static inline struct access_masks 104 landlock_upgrade_handled_access_masks(struct access_masks access_masks) 105 { 106 /* 107 * All access rights that are denied by default whether they are 108 * explicitly handled or not. 109 */ 110 if (access_masks.fs) 111 access_masks.fs |= _LANDLOCK_ACCESS_FS_INITIALLY_DENIED; 112 113 return access_masks; 114 } 115 116 /* Checks the subset relation between access masks. */ 117 static inline bool access_mask_subset(access_mask_t subset, 118 access_mask_t superset) 119 { 120 return (subset | superset) == superset; 121 } 122 123 #endif /* _SECURITY_LANDLOCK_ACCESS_H */ 124