1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _LINUX_MNT_IDMAPPING_H 3 #define _LINUX_MNT_IDMAPPING_H 4 5 #include <linux/types.h> 6 #include <linux/uidgid.h> 7 8 struct mnt_idmap; 9 struct user_namespace; 10 11 extern struct mnt_idmap nop_mnt_idmap; 12 extern struct user_namespace init_user_ns; 13 14 typedef struct { 15 uid_t val; 16 } vfsuid_t; 17 18 typedef struct { 19 gid_t val; 20 } vfsgid_t; 21 22 static_assert(sizeof(vfsuid_t) == sizeof(kuid_t)); 23 static_assert(sizeof(vfsgid_t) == sizeof(kgid_t)); 24 static_assert(offsetof(vfsuid_t, val) == offsetof(kuid_t, val)); 25 static_assert(offsetof(vfsgid_t, val) == offsetof(kgid_t, val)); 26 27 #ifdef CONFIG_MULTIUSER 28 static inline uid_t __vfsuid_val(vfsuid_t uid) 29 { 30 return uid.val; 31 } 32 33 static inline gid_t __vfsgid_val(vfsgid_t gid) 34 { 35 return gid.val; 36 } 37 #else 38 static inline uid_t __vfsuid_val(vfsuid_t uid) 39 { 40 return 0; 41 } 42 43 static inline gid_t __vfsgid_val(vfsgid_t gid) 44 { 45 return 0; 46 } 47 #endif 48 49 static inline bool vfsuid_valid(vfsuid_t uid) 50 { 51 return __vfsuid_val(uid) != (uid_t)-1; 52 } 53 54 static inline bool vfsgid_valid(vfsgid_t gid) 55 { 56 return __vfsgid_val(gid) != (gid_t)-1; 57 } 58 59 static inline bool vfsuid_eq(vfsuid_t left, vfsuid_t right) 60 { 61 return vfsuid_valid(left) && __vfsuid_val(left) == __vfsuid_val(right); 62 } 63 64 static inline bool vfsgid_eq(vfsgid_t left, vfsgid_t right) 65 { 66 return vfsgid_valid(left) && __vfsgid_val(left) == __vfsgid_val(right); 67 } 68 69 /** 70 * vfsuid_eq_kuid - check whether kuid and vfsuid have the same value 71 * @vfsuid: the vfsuid to compare 72 * @kuid: the kuid to compare 73 * 74 * Check whether @vfsuid and @kuid have the same values. 75 * 76 * Return: true if @vfsuid and @kuid have the same value, false if not. 77 * Comparison between two invalid uids returns false. 78 */ 79 static inline bool vfsuid_eq_kuid(vfsuid_t vfsuid, kuid_t kuid) 80 { 81 return vfsuid_valid(vfsuid) && __vfsuid_val(vfsuid) == __kuid_val(kuid); 82 } 83 84 /** 85 * vfsgid_eq_kgid - check whether kgid and vfsgid have the same value 86 * @vfsgid: the vfsgid to compare 87 * @kgid: the kgid to compare 88 * 89 * Check whether @vfsgid and @kgid have the same values. 90 * 91 * Return: true if @vfsgid and @kgid have the same value, false if not. 92 * Comparison between two invalid gids returns false. 93 */ 94 static inline bool vfsgid_eq_kgid(vfsgid_t vfsgid, kgid_t kgid) 95 { 96 return vfsgid_valid(vfsgid) && __vfsgid_val(vfsgid) == __kgid_val(kgid); 97 } 98 99 /* 100 * vfs{g,u}ids are created from k{g,u}ids. 101 * We don't allow them to be created from regular {u,g}id. 102 */ 103 #define VFSUIDT_INIT(val) (vfsuid_t){ __kuid_val(val) } 104 #define VFSGIDT_INIT(val) (vfsgid_t){ __kgid_val(val) } 105 106 #define INVALID_VFSUID VFSUIDT_INIT(INVALID_UID) 107 #define INVALID_VFSGID VFSGIDT_INIT(INVALID_GID) 108 109 /* 110 * Allow a vfs{g,u}id to be used as a k{g,u}id where we want to compare 111 * whether the mapped value is identical to value of a k{g,u}id. 112 */ 113 #define AS_KUIDT(val) (kuid_t){ __vfsuid_val(val) } 114 #define AS_KGIDT(val) (kgid_t){ __vfsgid_val(val) } 115 116 #ifdef CONFIG_MULTIUSER 117 /** 118 * vfsgid_in_group_p() - check whether a vfsuid matches the caller's groups 119 * @vfsgid: the mnt gid to match 120 * 121 * This function can be used to determine whether @vfsuid matches any of the 122 * caller's groups. 123 * 124 * Return: 1 if vfsuid matches caller's groups, 0 if not. 125 */ 126 static inline int vfsgid_in_group_p(vfsgid_t vfsgid) 127 { 128 return in_group_p(AS_KGIDT(vfsgid)); 129 } 130 #else 131 static inline int vfsgid_in_group_p(vfsgid_t vfsgid) 132 { 133 return 1; 134 } 135 #endif 136 137 /** 138 * initial_idmapping - check whether this is the initial mapping 139 * @ns: idmapping to check 140 * 141 * Check whether this is the initial mapping, mapping 0 to 0, 1 to 1, 142 * [...], 1000 to 1000 [...]. 143 * 144 * Return: true if this is the initial mapping, false if not. 145 */ 146 static inline bool initial_idmapping(const struct user_namespace *ns) 147 { 148 return ns == &init_user_ns; 149 } 150 151 /** 152 * no_idmapping - check whether we can skip remapping a kuid/gid 153 * @mnt_userns: the mount's idmapping 154 * @fs_userns: the filesystem's idmapping 155 * 156 * This function can be used to check whether a remapping between two 157 * idmappings is required. 158 * An idmapped mount is a mount that has an idmapping attached to it that 159 * is different from the filsystem's idmapping and the initial idmapping. 160 * If the initial mapping is used or the idmapping of the mount and the 161 * filesystem are identical no remapping is required. 162 * 163 * Return: true if remapping can be skipped, false if not. 164 */ 165 static inline bool no_idmapping(const struct user_namespace *mnt_userns, 166 const struct user_namespace *fs_userns) 167 { 168 return initial_idmapping(mnt_userns) || mnt_userns == fs_userns; 169 } 170 171 /** 172 * make_vfsuid - map a filesystem kuid into a mnt_userns 173 * @mnt_userns: the mount's idmapping 174 * @fs_userns: the filesystem's idmapping 175 * @kuid : kuid to be mapped 176 * 177 * Take a @kuid and remap it from @fs_userns into @mnt_userns. Use this 178 * function when preparing a @kuid to be reported to userspace. 179 * 180 * If no_idmapping() determines that this is not an idmapped mount we can 181 * simply return @kuid unchanged. 182 * If initial_idmapping() tells us that the filesystem is not mounted with an 183 * idmapping we know the value of @kuid won't change when calling 184 * from_kuid() so we can simply retrieve the value via __kuid_val() 185 * directly. 186 * 187 * Return: @kuid mapped according to @mnt_userns. 188 * If @kuid has no mapping in either @mnt_userns or @fs_userns INVALID_UID is 189 * returned. 190 */ 191 192 static inline vfsuid_t make_vfsuid(struct user_namespace *mnt_userns, 193 struct user_namespace *fs_userns, 194 kuid_t kuid) 195 { 196 uid_t uid; 197 198 if (no_idmapping(mnt_userns, fs_userns)) 199 return VFSUIDT_INIT(kuid); 200 if (initial_idmapping(fs_userns)) 201 uid = __kuid_val(kuid); 202 else 203 uid = from_kuid(fs_userns, kuid); 204 if (uid == (uid_t)-1) 205 return INVALID_VFSUID; 206 return VFSUIDT_INIT(make_kuid(mnt_userns, uid)); 207 } 208 209 /** 210 * make_vfsgid - map a filesystem kgid into a mnt_userns 211 * @mnt_userns: the mount's idmapping 212 * @fs_userns: the filesystem's idmapping 213 * @kgid : kgid to be mapped 214 * 215 * Take a @kgid and remap it from @fs_userns into @mnt_userns. Use this 216 * function when preparing a @kgid to be reported to userspace. 217 * 218 * If no_idmapping() determines that this is not an idmapped mount we can 219 * simply return @kgid unchanged. 220 * If initial_idmapping() tells us that the filesystem is not mounted with an 221 * idmapping we know the value of @kgid won't change when calling 222 * from_kgid() so we can simply retrieve the value via __kgid_val() 223 * directly. 224 * 225 * Return: @kgid mapped according to @mnt_userns. 226 * If @kgid has no mapping in either @mnt_userns or @fs_userns INVALID_GID is 227 * returned. 228 */ 229 230 static inline vfsgid_t make_vfsgid(struct user_namespace *mnt_userns, 231 struct user_namespace *fs_userns, 232 kgid_t kgid) 233 { 234 gid_t gid; 235 236 if (no_idmapping(mnt_userns, fs_userns)) 237 return VFSGIDT_INIT(kgid); 238 if (initial_idmapping(fs_userns)) 239 gid = __kgid_val(kgid); 240 else 241 gid = from_kgid(fs_userns, kgid); 242 if (gid == (gid_t)-1) 243 return INVALID_VFSGID; 244 return VFSGIDT_INIT(make_kgid(mnt_userns, gid)); 245 } 246 247 /** 248 * from_vfsuid - map a vfsuid into the filesystem idmapping 249 * @mnt_userns: the mount's idmapping 250 * @fs_userns: the filesystem's idmapping 251 * @vfsuid : vfsuid to be mapped 252 * 253 * Map @vfsuid into the filesystem idmapping. This function has to be used in 254 * order to e.g. write @vfsuid to inode->i_uid. 255 * 256 * Return: @vfsuid mapped into the filesystem idmapping 257 */ 258 static inline kuid_t from_vfsuid(struct user_namespace *mnt_userns, 259 struct user_namespace *fs_userns, 260 vfsuid_t vfsuid) 261 { 262 uid_t uid; 263 264 if (no_idmapping(mnt_userns, fs_userns)) 265 return AS_KUIDT(vfsuid); 266 uid = from_kuid(mnt_userns, AS_KUIDT(vfsuid)); 267 if (uid == (uid_t)-1) 268 return INVALID_UID; 269 if (initial_idmapping(fs_userns)) 270 return KUIDT_INIT(uid); 271 return make_kuid(fs_userns, uid); 272 } 273 274 /** 275 * vfsuid_has_fsmapping - check whether a vfsuid maps into the filesystem 276 * @mnt_userns: the mount's idmapping 277 * @fs_userns: the filesystem's idmapping 278 * @vfsuid: vfsuid to be mapped 279 * 280 * Check whether @vfsuid has a mapping in the filesystem idmapping. Use this 281 * function to check whether the filesystem idmapping has a mapping for 282 * @vfsuid. 283 * 284 * Return: true if @vfsuid has a mapping in the filesystem, false if not. 285 */ 286 static inline bool vfsuid_has_fsmapping(struct user_namespace *mnt_userns, 287 struct user_namespace *fs_userns, 288 vfsuid_t vfsuid) 289 { 290 return uid_valid(from_vfsuid(mnt_userns, fs_userns, vfsuid)); 291 } 292 293 static inline bool vfsuid_has_mapping(struct user_namespace *userns, 294 vfsuid_t vfsuid) 295 { 296 return from_kuid(userns, AS_KUIDT(vfsuid)) != (uid_t)-1; 297 } 298 299 /** 300 * vfsuid_into_kuid - convert vfsuid into kuid 301 * @vfsuid: the vfsuid to convert 302 * 303 * This can be used when a vfsuid is committed as a kuid. 304 * 305 * Return: a kuid with the value of @vfsuid 306 */ 307 static inline kuid_t vfsuid_into_kuid(vfsuid_t vfsuid) 308 { 309 return AS_KUIDT(vfsuid); 310 } 311 312 /** 313 * from_vfsgid - map a vfsgid into the filesystem idmapping 314 * @mnt_userns: the mount's idmapping 315 * @fs_userns: the filesystem's idmapping 316 * @vfsgid : vfsgid to be mapped 317 * 318 * Map @vfsgid into the filesystem idmapping. This function has to be used in 319 * order to e.g. write @vfsgid to inode->i_gid. 320 * 321 * Return: @vfsgid mapped into the filesystem idmapping 322 */ 323 static inline kgid_t from_vfsgid(struct user_namespace *mnt_userns, 324 struct user_namespace *fs_userns, 325 vfsgid_t vfsgid) 326 { 327 gid_t gid; 328 329 if (no_idmapping(mnt_userns, fs_userns)) 330 return AS_KGIDT(vfsgid); 331 gid = from_kgid(mnt_userns, AS_KGIDT(vfsgid)); 332 if (gid == (gid_t)-1) 333 return INVALID_GID; 334 if (initial_idmapping(fs_userns)) 335 return KGIDT_INIT(gid); 336 return make_kgid(fs_userns, gid); 337 } 338 339 /** 340 * vfsgid_has_fsmapping - check whether a vfsgid maps into the filesystem 341 * @mnt_userns: the mount's idmapping 342 * @fs_userns: the filesystem's idmapping 343 * @vfsgid: vfsgid to be mapped 344 * 345 * Check whether @vfsgid has a mapping in the filesystem idmapping. Use this 346 * function to check whether the filesystem idmapping has a mapping for 347 * @vfsgid. 348 * 349 * Return: true if @vfsgid has a mapping in the filesystem, false if not. 350 */ 351 static inline bool vfsgid_has_fsmapping(struct user_namespace *mnt_userns, 352 struct user_namespace *fs_userns, 353 vfsgid_t vfsgid) 354 { 355 return gid_valid(from_vfsgid(mnt_userns, fs_userns, vfsgid)); 356 } 357 358 static inline bool vfsgid_has_mapping(struct user_namespace *userns, 359 vfsgid_t vfsgid) 360 { 361 return from_kgid(userns, AS_KGIDT(vfsgid)) != (gid_t)-1; 362 } 363 364 /** 365 * vfsgid_into_kgid - convert vfsgid into kgid 366 * @vfsgid: the vfsgid to convert 367 * 368 * This can be used when a vfsgid is committed as a kgid. 369 * 370 * Return: a kgid with the value of @vfsgid 371 */ 372 static inline kgid_t vfsgid_into_kgid(vfsgid_t vfsgid) 373 { 374 return AS_KGIDT(vfsgid); 375 } 376 377 /** 378 * mapped_fsuid - return caller's fsuid mapped up into a mnt_userns 379 * @mnt_userns: the mount's idmapping 380 * @fs_userns: the filesystem's idmapping 381 * 382 * Use this helper to initialize a new vfs or filesystem object based on 383 * the caller's fsuid. A common example is initializing the i_uid field of 384 * a newly allocated inode triggered by a creation event such as mkdir or 385 * O_CREAT. Other examples include the allocation of quotas for a specific 386 * user. 387 * 388 * Return: the caller's current fsuid mapped up according to @mnt_userns. 389 */ 390 static inline kuid_t mapped_fsuid(struct user_namespace *mnt_userns, 391 struct user_namespace *fs_userns) 392 { 393 return from_vfsuid(mnt_userns, fs_userns, 394 VFSUIDT_INIT(current_fsuid())); 395 } 396 397 /** 398 * mapped_fsgid - return caller's fsgid mapped up into a mnt_userns 399 * @mnt_userns: the mount's idmapping 400 * @fs_userns: the filesystem's idmapping 401 * 402 * Use this helper to initialize a new vfs or filesystem object based on 403 * the caller's fsgid. A common example is initializing the i_gid field of 404 * a newly allocated inode triggered by a creation event such as mkdir or 405 * O_CREAT. Other examples include the allocation of quotas for a specific 406 * user. 407 * 408 * Return: the caller's current fsgid mapped up according to @mnt_userns. 409 */ 410 static inline kgid_t mapped_fsgid(struct user_namespace *mnt_userns, 411 struct user_namespace *fs_userns) 412 { 413 return from_vfsgid(mnt_userns, fs_userns, 414 VFSGIDT_INIT(current_fsgid())); 415 } 416 417 #endif /* _LINUX_MNT_IDMAPPING_H */ 418