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 domain->handled_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 u32 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 } __packed __aligned(sizeof(u32)); 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 #define _LANDLOCK_LAYER_MASK_PADDING \ 65 (BITS_PER_TYPE(access_mask_t) - LANDLOCK_NUM_ACCESS_MAX - \ 66 IS_ENABLED(CONFIG_SECURITY_LANDLOCK_LOG)) 67 68 /** 69 * struct layer_mask - The access rights and rule flags for a layer. 70 * 71 * This has a bit for each access rights and rule flags. During access checks, 72 * it is used to represent the access rights for each layer which still need to 73 * be fulfilled. When all bits are 0, the access request is considered to be 74 * fulfilled. 75 */ 76 struct layer_mask { 77 /** 78 * @access: The unfulfilled access rights for this layer. 79 */ 80 access_mask_t access : LANDLOCK_NUM_ACCESS_MAX; 81 #ifdef CONFIG_SECURITY_LANDLOCK_LOG 82 /** 83 * @quiet: Whether we have encountered a rule with the quiet flag for 84 * this layer. Used to control logging. 85 */ 86 access_mask_t quiet : 1; 87 #endif /* CONFIG_SECURITY_LANDLOCK_LOG */ 88 /** 89 * @__pad: Padding for the compiler's bitfield initialization. 90 */ 91 access_mask_t __pad : _LANDLOCK_LAYER_MASK_PADDING; 92 } __packed __aligned(sizeof(access_mask_t)); 93 94 /* 95 * Make sure that we don't increase the size of struct layer_mask when storing 96 * rule flags. 97 */ 98 static_assert(sizeof(struct layer_mask) == sizeof(access_mask_t)); 99 100 /** 101 * struct layer_masks - An array of struct layer_mask, one per layer. 102 */ 103 struct layer_masks { 104 /** 105 * @layers: The unfulfilled access rights for each layer. 106 */ 107 struct layer_mask layers[LANDLOCK_MAX_NUM_LAYERS]; 108 }; 109 110 /* 111 * Tracks domains responsible of a denied access. This avoids storing in each 112 * object the full matrix of per-layer unfulfilled access rights, which is 113 * required by update_request(). 114 * 115 * Each nibble represents the layer index of the newest layer which denied a 116 * certain access right. For file system access rights, the upper four bits are 117 * the index of the layer which denies LANDLOCK_ACCESS_FS_IOCTL_DEV and the 118 * lower nibble represents LANDLOCK_ACCESS_FS_TRUNCATE. 119 */ 120 typedef u8 deny_masks_t; 121 122 /* 123 * Makes sure all optional access rights can be tied to a layer index (cf. 124 * get_deny_mask). 125 */ 126 static_assert(BITS_PER_TYPE(deny_masks_t) >= 127 (HWEIGHT(LANDLOCK_MAX_NUM_LAYERS - 1) * 128 HWEIGHT(_LANDLOCK_ACCESS_FS_OPTIONAL))); 129 130 /* LANDLOCK_MAX_NUM_LAYERS must be a power of two (cf. deny_masks_t assert). */ 131 static_assert(HWEIGHT(LANDLOCK_MAX_NUM_LAYERS) == 1); 132 133 /* Upgrades with all initially denied by default access rights. */ 134 static inline struct access_masks 135 landlock_upgrade_handled_access_masks(struct access_masks access_masks) 136 { 137 /* 138 * All access rights that are denied by default whether they are 139 * explicitly handled or not. 140 */ 141 if (access_masks.fs) 142 access_masks.fs |= _LANDLOCK_ACCESS_FS_INITIALLY_DENIED; 143 144 return access_masks; 145 } 146 147 /* Checks the subset relation between access masks. */ 148 static inline bool access_mask_subset(access_mask_t subset, 149 access_mask_t superset) 150 { 151 return (subset | superset) == superset; 152 } 153 154 /* A bitmask that is large enough to hold set of optional accesses. */ 155 typedef u8 optional_access_t; 156 static_assert(BITS_PER_TYPE(optional_access_t) >= 157 HWEIGHT(_LANDLOCK_ACCESS_FS_OPTIONAL)); 158 159 #endif /* _SECURITY_LANDLOCK_ACCESS_H */ 160