1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (C) 2002,2003 by Andreas Gruenbacher <a.gruenbacher@computer.org> 4 * 5 * Fixes from William Schumacher incorporated on 15 March 2001. 6 * (Reported by Charles Bertsch, <CBertsch@microtest.com>). 7 */ 8 9 /* 10 * This file contains generic functions for manipulating 11 * POSIX 1003.1e draft standard 17 ACLs. 12 */ 13 14 #include <linux/kernel.h> 15 #include <linux/slab.h> 16 #include <linux/atomic.h> 17 #include <linux/fs.h> 18 #include <linux/sched.h> 19 #include <linux/cred.h> 20 #include <linux/posix_acl.h> 21 #include <linux/posix_acl_xattr.h> 22 #include <linux/xattr.h> 23 #include <linux/export.h> 24 #include <linux/user_namespace.h> 25 #include <linux/namei.h> 26 #include <linux/mnt_idmapping.h> 27 #include <linux/iversion.h> 28 #include <linux/security.h> 29 #include <linux/evm.h> 30 #include <linux/fsnotify.h> 31 32 #include "internal.h" 33 34 static struct posix_acl **acl_by_type(struct inode *inode, int type) 35 { 36 switch (type) { 37 case ACL_TYPE_ACCESS: 38 return &inode->i_acl; 39 case ACL_TYPE_DEFAULT: 40 return &inode->i_default_acl; 41 default: 42 BUG(); 43 } 44 } 45 46 struct posix_acl *get_cached_acl(struct inode *inode, int type) 47 { 48 struct posix_acl **p = acl_by_type(inode, type); 49 struct posix_acl *acl; 50 51 for (;;) { 52 rcu_read_lock(); 53 acl = rcu_dereference(*p); 54 if (!acl || is_uncached_acl(acl) || 55 refcount_inc_not_zero(&acl->a_refcount)) 56 break; 57 rcu_read_unlock(); 58 cpu_relax(); 59 } 60 rcu_read_unlock(); 61 return acl; 62 } 63 EXPORT_SYMBOL(get_cached_acl); 64 65 struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type) 66 { 67 struct posix_acl *acl = rcu_dereference(*acl_by_type(inode, type)); 68 69 if (acl == ACL_DONT_CACHE) { 70 struct posix_acl *ret; 71 72 ret = inode->i_op->get_inode_acl(inode, type, LOOKUP_RCU); 73 if (!IS_ERR(ret)) 74 acl = ret; 75 } 76 77 return acl; 78 } 79 EXPORT_SYMBOL(get_cached_acl_rcu); 80 81 void set_cached_acl(struct inode *inode, int type, struct posix_acl *acl) 82 { 83 struct posix_acl **p = acl_by_type(inode, type); 84 struct posix_acl *old; 85 86 old = xchg(p, posix_acl_dup(acl)); 87 if (!is_uncached_acl(old)) 88 posix_acl_release(old); 89 } 90 EXPORT_SYMBOL(set_cached_acl); 91 92 static void __forget_cached_acl(struct posix_acl **p) 93 { 94 struct posix_acl *old; 95 96 old = xchg(p, ACL_NOT_CACHED); 97 if (!is_uncached_acl(old)) 98 posix_acl_release(old); 99 } 100 101 void forget_cached_acl(struct inode *inode, int type) 102 { 103 __forget_cached_acl(acl_by_type(inode, type)); 104 } 105 EXPORT_SYMBOL(forget_cached_acl); 106 107 void forget_all_cached_acls(struct inode *inode) 108 { 109 __forget_cached_acl(&inode->i_acl); 110 __forget_cached_acl(&inode->i_default_acl); 111 } 112 EXPORT_SYMBOL(forget_all_cached_acls); 113 114 static struct posix_acl *__get_acl(struct mnt_idmap *idmap, 115 struct dentry *dentry, struct inode *inode, 116 int type) 117 { 118 struct posix_acl *sentinel; 119 struct posix_acl **p; 120 struct posix_acl *acl; 121 122 /* 123 * The sentinel is used to detect when another operation like 124 * set_cached_acl() or forget_cached_acl() races with get_inode_acl(). 125 * It is guaranteed that is_uncached_acl(sentinel) is true. 126 */ 127 128 acl = get_cached_acl(inode, type); 129 if (!is_uncached_acl(acl)) 130 return acl; 131 132 if (!IS_POSIXACL(inode)) 133 return NULL; 134 135 sentinel = uncached_acl_sentinel(current); 136 p = acl_by_type(inode, type); 137 138 /* 139 * If the ACL isn't being read yet, set our sentinel. Otherwise, the 140 * current value of the ACL will not be ACL_NOT_CACHED and so our own 141 * sentinel will not be set; another task will update the cache. We 142 * could wait for that other task to complete its job, but it's easier 143 * to just call ->get_inode_acl to fetch the ACL ourself. (This is 144 * going to be an unlikely race.) 145 */ 146 cmpxchg(p, ACL_NOT_CACHED, sentinel); 147 148 /* 149 * Normally, the ACL returned by ->get{_inode}_acl will be cached. 150 * A filesystem can prevent that by calling 151 * forget_cached_acl(inode, type) in ->get{_inode}_acl. 152 * 153 * If the filesystem doesn't have a get{_inode}_ acl() function at all, 154 * we'll just create the negative cache entry. 155 */ 156 if (dentry && inode->i_op->get_acl) { 157 acl = inode->i_op->get_acl(idmap, dentry, type); 158 } else if (inode->i_op->get_inode_acl) { 159 acl = inode->i_op->get_inode_acl(inode, type, false); 160 } else { 161 set_cached_acl(inode, type, NULL); 162 return NULL; 163 } 164 if (IS_ERR(acl)) { 165 /* 166 * Remove our sentinel so that we don't block future attempts 167 * to cache the ACL. 168 */ 169 cmpxchg(p, sentinel, ACL_NOT_CACHED); 170 return acl; 171 } 172 173 /* 174 * Cache the result, but only if our sentinel is still in place. 175 */ 176 posix_acl_dup(acl); 177 if (unlikely(cmpxchg(p, sentinel, acl) != sentinel)) 178 posix_acl_release(acl); 179 return acl; 180 } 181 182 struct posix_acl *get_inode_acl(struct inode *inode, int type) 183 { 184 return __get_acl(&nop_mnt_idmap, NULL, inode, type); 185 } 186 EXPORT_SYMBOL(get_inode_acl); 187 188 /* 189 * Init a fresh posix_acl 190 */ 191 void 192 posix_acl_init(struct posix_acl *acl, int count) 193 { 194 refcount_set(&acl->a_refcount, 1); 195 acl->a_count = count; 196 } 197 EXPORT_SYMBOL(posix_acl_init); 198 199 /* 200 * Allocate a new ACL with the specified number of entries. 201 */ 202 struct posix_acl * 203 posix_acl_alloc(int count, gfp_t flags) 204 { 205 const size_t size = sizeof(struct posix_acl) + 206 count * sizeof(struct posix_acl_entry); 207 struct posix_acl *acl = kmalloc(size, flags); 208 if (acl) 209 posix_acl_init(acl, count); 210 return acl; 211 } 212 EXPORT_SYMBOL(posix_acl_alloc); 213 214 /* 215 * Clone an ACL. 216 */ 217 struct posix_acl * 218 posix_acl_clone(const struct posix_acl *acl, gfp_t flags) 219 { 220 struct posix_acl *clone = NULL; 221 222 if (acl) { 223 int size = sizeof(struct posix_acl) + acl->a_count * 224 sizeof(struct posix_acl_entry); 225 clone = kmemdup(acl, size, flags); 226 if (clone) 227 refcount_set(&clone->a_refcount, 1); 228 } 229 return clone; 230 } 231 EXPORT_SYMBOL_GPL(posix_acl_clone); 232 233 /* 234 * Check if an acl is valid. Returns 0 if it is, or -E... otherwise. 235 */ 236 int 237 posix_acl_valid(struct user_namespace *user_ns, const struct posix_acl *acl) 238 { 239 const struct posix_acl_entry *pa, *pe; 240 int state = ACL_USER_OBJ; 241 int needs_mask = 0; 242 243 FOREACH_ACL_ENTRY(pa, acl, pe) { 244 if (pa->e_perm & ~(ACL_READ|ACL_WRITE|ACL_EXECUTE)) 245 return -EINVAL; 246 switch (pa->e_tag) { 247 case ACL_USER_OBJ: 248 if (state == ACL_USER_OBJ) { 249 state = ACL_USER; 250 break; 251 } 252 return -EINVAL; 253 254 case ACL_USER: 255 if (state != ACL_USER) 256 return -EINVAL; 257 if (!kuid_has_mapping(user_ns, pa->e_uid)) 258 return -EINVAL; 259 needs_mask = 1; 260 break; 261 262 case ACL_GROUP_OBJ: 263 if (state == ACL_USER) { 264 state = ACL_GROUP; 265 break; 266 } 267 return -EINVAL; 268 269 case ACL_GROUP: 270 if (state != ACL_GROUP) 271 return -EINVAL; 272 if (!kgid_has_mapping(user_ns, pa->e_gid)) 273 return -EINVAL; 274 needs_mask = 1; 275 break; 276 277 case ACL_MASK: 278 if (state != ACL_GROUP) 279 return -EINVAL; 280 state = ACL_OTHER; 281 break; 282 283 case ACL_OTHER: 284 if (state == ACL_OTHER || 285 (state == ACL_GROUP && !needs_mask)) { 286 state = 0; 287 break; 288 } 289 return -EINVAL; 290 291 default: 292 return -EINVAL; 293 } 294 } 295 if (state == 0) 296 return 0; 297 return -EINVAL; 298 } 299 EXPORT_SYMBOL(posix_acl_valid); 300 301 /* 302 * Returns 0 if the acl can be exactly represented in the traditional 303 * file mode permission bits, or else 1. Returns -E... on error. 304 */ 305 int 306 posix_acl_equiv_mode(const struct posix_acl *acl, umode_t *mode_p) 307 { 308 const struct posix_acl_entry *pa, *pe; 309 umode_t mode = 0; 310 int not_equiv = 0; 311 312 /* 313 * A null ACL can always be presented as mode bits. 314 */ 315 if (!acl) 316 return 0; 317 318 FOREACH_ACL_ENTRY(pa, acl, pe) { 319 switch (pa->e_tag) { 320 case ACL_USER_OBJ: 321 mode |= (pa->e_perm & S_IRWXO) << 6; 322 break; 323 case ACL_GROUP_OBJ: 324 mode |= (pa->e_perm & S_IRWXO) << 3; 325 break; 326 case ACL_OTHER: 327 mode |= pa->e_perm & S_IRWXO; 328 break; 329 case ACL_MASK: 330 mode = (mode & ~S_IRWXG) | 331 ((pa->e_perm & S_IRWXO) << 3); 332 not_equiv = 1; 333 break; 334 case ACL_USER: 335 case ACL_GROUP: 336 not_equiv = 1; 337 break; 338 default: 339 return -EINVAL; 340 } 341 } 342 if (mode_p) 343 *mode_p = (*mode_p & ~S_IRWXUGO) | mode; 344 return not_equiv; 345 } 346 EXPORT_SYMBOL(posix_acl_equiv_mode); 347 348 /* 349 * Create an ACL representing the file mode permission bits of an inode. 350 */ 351 struct posix_acl * 352 posix_acl_from_mode(umode_t mode, gfp_t flags) 353 { 354 struct posix_acl *acl = posix_acl_alloc(3, flags); 355 if (!acl) 356 return ERR_PTR(-ENOMEM); 357 358 acl->a_entries[0].e_tag = ACL_USER_OBJ; 359 acl->a_entries[0].e_perm = (mode & S_IRWXU) >> 6; 360 361 acl->a_entries[1].e_tag = ACL_GROUP_OBJ; 362 acl->a_entries[1].e_perm = (mode & S_IRWXG) >> 3; 363 364 acl->a_entries[2].e_tag = ACL_OTHER; 365 acl->a_entries[2].e_perm = (mode & S_IRWXO); 366 return acl; 367 } 368 EXPORT_SYMBOL(posix_acl_from_mode); 369 370 /* 371 * Return 0 if current is granted want access to the inode 372 * by the acl. Returns -E... otherwise. 373 */ 374 int 375 posix_acl_permission(struct mnt_idmap *idmap, struct inode *inode, 376 const struct posix_acl *acl, int want) 377 { 378 const struct posix_acl_entry *pa, *pe, *mask_obj; 379 struct user_namespace *fs_userns = i_user_ns(inode); 380 struct user_namespace *mnt_userns = mnt_idmap_owner(idmap); 381 int found = 0; 382 vfsuid_t vfsuid; 383 vfsgid_t vfsgid; 384 385 want &= MAY_READ | MAY_WRITE | MAY_EXEC; 386 387 FOREACH_ACL_ENTRY(pa, acl, pe) { 388 switch(pa->e_tag) { 389 case ACL_USER_OBJ: 390 /* (May have been checked already) */ 391 vfsuid = i_uid_into_vfsuid(mnt_userns, inode); 392 if (vfsuid_eq_kuid(vfsuid, current_fsuid())) 393 goto check_perm; 394 break; 395 case ACL_USER: 396 vfsuid = make_vfsuid(mnt_userns, fs_userns, 397 pa->e_uid); 398 if (vfsuid_eq_kuid(vfsuid, current_fsuid())) 399 goto mask; 400 break; 401 case ACL_GROUP_OBJ: 402 vfsgid = i_gid_into_vfsgid(mnt_userns, inode); 403 if (vfsgid_in_group_p(vfsgid)) { 404 found = 1; 405 if ((pa->e_perm & want) == want) 406 goto mask; 407 } 408 break; 409 case ACL_GROUP: 410 vfsgid = make_vfsgid(mnt_userns, fs_userns, 411 pa->e_gid); 412 if (vfsgid_in_group_p(vfsgid)) { 413 found = 1; 414 if ((pa->e_perm & want) == want) 415 goto mask; 416 } 417 break; 418 case ACL_MASK: 419 break; 420 case ACL_OTHER: 421 if (found) 422 return -EACCES; 423 else 424 goto check_perm; 425 default: 426 return -EIO; 427 } 428 } 429 return -EIO; 430 431 mask: 432 for (mask_obj = pa+1; mask_obj != pe; mask_obj++) { 433 if (mask_obj->e_tag == ACL_MASK) { 434 if ((pa->e_perm & mask_obj->e_perm & want) == want) 435 return 0; 436 return -EACCES; 437 } 438 } 439 440 check_perm: 441 if ((pa->e_perm & want) == want) 442 return 0; 443 return -EACCES; 444 } 445 446 /* 447 * Modify acl when creating a new inode. The caller must ensure the acl is 448 * only referenced once. 449 * 450 * mode_p initially must contain the mode parameter to the open() / creat() 451 * system calls. All permissions that are not granted by the acl are removed. 452 * The permissions in the acl are changed to reflect the mode_p parameter. 453 */ 454 static int posix_acl_create_masq(struct posix_acl *acl, umode_t *mode_p) 455 { 456 struct posix_acl_entry *pa, *pe; 457 struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL; 458 umode_t mode = *mode_p; 459 int not_equiv = 0; 460 461 /* assert(atomic_read(acl->a_refcount) == 1); */ 462 463 FOREACH_ACL_ENTRY(pa, acl, pe) { 464 switch(pa->e_tag) { 465 case ACL_USER_OBJ: 466 pa->e_perm &= (mode >> 6) | ~S_IRWXO; 467 mode &= (pa->e_perm << 6) | ~S_IRWXU; 468 break; 469 470 case ACL_USER: 471 case ACL_GROUP: 472 not_equiv = 1; 473 break; 474 475 case ACL_GROUP_OBJ: 476 group_obj = pa; 477 break; 478 479 case ACL_OTHER: 480 pa->e_perm &= mode | ~S_IRWXO; 481 mode &= pa->e_perm | ~S_IRWXO; 482 break; 483 484 case ACL_MASK: 485 mask_obj = pa; 486 not_equiv = 1; 487 break; 488 489 default: 490 return -EIO; 491 } 492 } 493 494 if (mask_obj) { 495 mask_obj->e_perm &= (mode >> 3) | ~S_IRWXO; 496 mode &= (mask_obj->e_perm << 3) | ~S_IRWXG; 497 } else { 498 if (!group_obj) 499 return -EIO; 500 group_obj->e_perm &= (mode >> 3) | ~S_IRWXO; 501 mode &= (group_obj->e_perm << 3) | ~S_IRWXG; 502 } 503 504 *mode_p = (*mode_p & ~S_IRWXUGO) | mode; 505 return not_equiv; 506 } 507 508 /* 509 * Modify the ACL for the chmod syscall. 510 */ 511 static int __posix_acl_chmod_masq(struct posix_acl *acl, umode_t mode) 512 { 513 struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL; 514 struct posix_acl_entry *pa, *pe; 515 516 /* assert(atomic_read(acl->a_refcount) == 1); */ 517 518 FOREACH_ACL_ENTRY(pa, acl, pe) { 519 switch(pa->e_tag) { 520 case ACL_USER_OBJ: 521 pa->e_perm = (mode & S_IRWXU) >> 6; 522 break; 523 524 case ACL_USER: 525 case ACL_GROUP: 526 break; 527 528 case ACL_GROUP_OBJ: 529 group_obj = pa; 530 break; 531 532 case ACL_MASK: 533 mask_obj = pa; 534 break; 535 536 case ACL_OTHER: 537 pa->e_perm = (mode & S_IRWXO); 538 break; 539 540 default: 541 return -EIO; 542 } 543 } 544 545 if (mask_obj) { 546 mask_obj->e_perm = (mode & S_IRWXG) >> 3; 547 } else { 548 if (!group_obj) 549 return -EIO; 550 group_obj->e_perm = (mode & S_IRWXG) >> 3; 551 } 552 553 return 0; 554 } 555 556 int 557 __posix_acl_create(struct posix_acl **acl, gfp_t gfp, umode_t *mode_p) 558 { 559 struct posix_acl *clone = posix_acl_clone(*acl, gfp); 560 int err = -ENOMEM; 561 if (clone) { 562 err = posix_acl_create_masq(clone, mode_p); 563 if (err < 0) { 564 posix_acl_release(clone); 565 clone = NULL; 566 } 567 } 568 posix_acl_release(*acl); 569 *acl = clone; 570 return err; 571 } 572 EXPORT_SYMBOL(__posix_acl_create); 573 574 int 575 __posix_acl_chmod(struct posix_acl **acl, gfp_t gfp, umode_t mode) 576 { 577 struct posix_acl *clone = posix_acl_clone(*acl, gfp); 578 int err = -ENOMEM; 579 if (clone) { 580 err = __posix_acl_chmod_masq(clone, mode); 581 if (err) { 582 posix_acl_release(clone); 583 clone = NULL; 584 } 585 } 586 posix_acl_release(*acl); 587 *acl = clone; 588 return err; 589 } 590 EXPORT_SYMBOL(__posix_acl_chmod); 591 592 /** 593 * posix_acl_chmod - chmod a posix acl 594 * 595 * @idmap: idmap of the mount @inode was found from 596 * @dentry: dentry to check permissions on 597 * @mode: the new mode of @inode 598 * 599 * If the dentry has been found through an idmapped mount the idmap of 600 * the vfsmount must be passed through @idmap. This function will then 601 * take care to map the inode according to @idmap before checking 602 * permissions. On non-idmapped mounts or if permission checking is to be 603 * performed on the raw inode simply passs @nop_mnt_idmap. 604 */ 605 int 606 posix_acl_chmod(struct mnt_idmap *idmap, struct dentry *dentry, 607 umode_t mode) 608 { 609 struct inode *inode = d_inode(dentry); 610 struct posix_acl *acl; 611 int ret = 0; 612 613 if (!IS_POSIXACL(inode)) 614 return 0; 615 if (!inode->i_op->set_acl) 616 return -EOPNOTSUPP; 617 618 acl = get_inode_acl(inode, ACL_TYPE_ACCESS); 619 if (IS_ERR_OR_NULL(acl)) { 620 if (acl == ERR_PTR(-EOPNOTSUPP)) 621 return 0; 622 return PTR_ERR(acl); 623 } 624 625 ret = __posix_acl_chmod(&acl, GFP_KERNEL, mode); 626 if (ret) 627 return ret; 628 ret = inode->i_op->set_acl(idmap, dentry, acl, ACL_TYPE_ACCESS); 629 posix_acl_release(acl); 630 return ret; 631 } 632 EXPORT_SYMBOL(posix_acl_chmod); 633 634 int 635 posix_acl_create(struct inode *dir, umode_t *mode, 636 struct posix_acl **default_acl, struct posix_acl **acl) 637 { 638 struct posix_acl *p; 639 struct posix_acl *clone; 640 int ret; 641 642 *acl = NULL; 643 *default_acl = NULL; 644 645 if (S_ISLNK(*mode) || !IS_POSIXACL(dir)) 646 return 0; 647 648 p = get_inode_acl(dir, ACL_TYPE_DEFAULT); 649 if (!p || p == ERR_PTR(-EOPNOTSUPP)) { 650 *mode &= ~current_umask(); 651 return 0; 652 } 653 if (IS_ERR(p)) 654 return PTR_ERR(p); 655 656 ret = -ENOMEM; 657 clone = posix_acl_clone(p, GFP_NOFS); 658 if (!clone) 659 goto err_release; 660 661 ret = posix_acl_create_masq(clone, mode); 662 if (ret < 0) 663 goto err_release_clone; 664 665 if (ret == 0) 666 posix_acl_release(clone); 667 else 668 *acl = clone; 669 670 if (!S_ISDIR(*mode)) 671 posix_acl_release(p); 672 else 673 *default_acl = p; 674 675 return 0; 676 677 err_release_clone: 678 posix_acl_release(clone); 679 err_release: 680 posix_acl_release(p); 681 return ret; 682 } 683 EXPORT_SYMBOL_GPL(posix_acl_create); 684 685 /** 686 * posix_acl_update_mode - update mode in set_acl 687 * @idmap: idmap of the mount @inode was found from 688 * @inode: target inode 689 * @mode_p: mode (pointer) for update 690 * @acl: acl pointer 691 * 692 * Update the file mode when setting an ACL: compute the new file permission 693 * bits based on the ACL. In addition, if the ACL is equivalent to the new 694 * file mode, set *@acl to NULL to indicate that no ACL should be set. 695 * 696 * As with chmod, clear the setgid bit if the caller is not in the owning group 697 * or capable of CAP_FSETID (see inode_change_ok). 698 * 699 * If the inode has been found through an idmapped mount the idmap of 700 * the vfsmount must be passed through @idmap. This function will then 701 * take care to map the inode according to @idmap before checking 702 * permissions. On non-idmapped mounts or if permission checking is to be 703 * performed on the raw inode simply passs @nop_mnt_idmap. 704 * 705 * Called from set_acl inode operations. 706 */ 707 int posix_acl_update_mode(struct mnt_idmap *idmap, 708 struct inode *inode, umode_t *mode_p, 709 struct posix_acl **acl) 710 { 711 struct user_namespace *mnt_userns = mnt_idmap_owner(idmap); 712 umode_t mode = inode->i_mode; 713 int error; 714 715 error = posix_acl_equiv_mode(*acl, &mode); 716 if (error < 0) 717 return error; 718 if (error == 0) 719 *acl = NULL; 720 if (!vfsgid_in_group_p(i_gid_into_vfsgid(mnt_userns, inode)) && 721 !capable_wrt_inode_uidgid(mnt_userns, inode, CAP_FSETID)) 722 mode &= ~S_ISGID; 723 *mode_p = mode; 724 return 0; 725 } 726 EXPORT_SYMBOL(posix_acl_update_mode); 727 728 /* 729 * Fix up the uids and gids in posix acl extended attributes in place. 730 */ 731 static int posix_acl_fix_xattr_common(const void *value, size_t size) 732 { 733 const struct posix_acl_xattr_header *header = value; 734 int count; 735 736 if (!header) 737 return -EINVAL; 738 if (size < sizeof(struct posix_acl_xattr_header)) 739 return -EINVAL; 740 if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION)) 741 return -EOPNOTSUPP; 742 743 count = posix_acl_xattr_count(size); 744 if (count < 0) 745 return -EINVAL; 746 if (count == 0) 747 return 0; 748 749 return count; 750 } 751 752 /** 753 * posix_acl_from_xattr - convert POSIX ACLs from backing store to VFS format 754 * @userns: the filesystem's idmapping 755 * @value: the uapi representation of POSIX ACLs 756 * @size: the size of @void 757 * 758 * Filesystems that store POSIX ACLs in the unaltered uapi format should use 759 * posix_acl_from_xattr() when reading them from the backing store and 760 * converting them into the struct posix_acl VFS format. The helper is 761 * specifically intended to be called from the acl inode operation. 762 * 763 * The posix_acl_from_xattr() function will map the raw {g,u}id values stored 764 * in ACL_{GROUP,USER} entries into idmapping in @userns. 765 * 766 * Note that posix_acl_from_xattr() does not take idmapped mounts into account. 767 * If it did it calling it from the get acl inode operation would return POSIX 768 * ACLs mapped according to an idmapped mount which would mean that the value 769 * couldn't be cached for the filesystem. Idmapped mounts are taken into 770 * account on the fly during permission checking or right at the VFS - 771 * userspace boundary before reporting them to the user. 772 * 773 * Return: Allocated struct posix_acl on success, NULL for a valid header but 774 * without actual POSIX ACL entries, or ERR_PTR() encoded error code. 775 */ 776 struct posix_acl *posix_acl_from_xattr(struct user_namespace *userns, 777 const void *value, size_t size) 778 { 779 const struct posix_acl_xattr_header *header = value; 780 const struct posix_acl_xattr_entry *entry = (const void *)(header + 1), *end; 781 int count; 782 struct posix_acl *acl; 783 struct posix_acl_entry *acl_e; 784 785 count = posix_acl_fix_xattr_common(value, size); 786 if (count < 0) 787 return ERR_PTR(count); 788 if (count == 0) 789 return NULL; 790 791 acl = posix_acl_alloc(count, GFP_NOFS); 792 if (!acl) 793 return ERR_PTR(-ENOMEM); 794 acl_e = acl->a_entries; 795 796 for (end = entry + count; entry != end; acl_e++, entry++) { 797 acl_e->e_tag = le16_to_cpu(entry->e_tag); 798 acl_e->e_perm = le16_to_cpu(entry->e_perm); 799 800 switch(acl_e->e_tag) { 801 case ACL_USER_OBJ: 802 case ACL_GROUP_OBJ: 803 case ACL_MASK: 804 case ACL_OTHER: 805 break; 806 807 case ACL_USER: 808 acl_e->e_uid = make_kuid(userns, 809 le32_to_cpu(entry->e_id)); 810 if (!uid_valid(acl_e->e_uid)) 811 goto fail; 812 break; 813 case ACL_GROUP: 814 acl_e->e_gid = make_kgid(userns, 815 le32_to_cpu(entry->e_id)); 816 if (!gid_valid(acl_e->e_gid)) 817 goto fail; 818 break; 819 820 default: 821 goto fail; 822 } 823 } 824 return acl; 825 826 fail: 827 posix_acl_release(acl); 828 return ERR_PTR(-EINVAL); 829 } 830 EXPORT_SYMBOL (posix_acl_from_xattr); 831 832 /* 833 * Convert from in-memory to extended attribute representation. 834 */ 835 int 836 posix_acl_to_xattr(struct user_namespace *user_ns, const struct posix_acl *acl, 837 void *buffer, size_t size) 838 { 839 struct posix_acl_xattr_header *ext_acl = buffer; 840 struct posix_acl_xattr_entry *ext_entry; 841 int real_size, n; 842 843 real_size = posix_acl_xattr_size(acl->a_count); 844 if (!buffer) 845 return real_size; 846 if (real_size > size) 847 return -ERANGE; 848 849 ext_entry = (void *)(ext_acl + 1); 850 ext_acl->a_version = cpu_to_le32(POSIX_ACL_XATTR_VERSION); 851 852 for (n=0; n < acl->a_count; n++, ext_entry++) { 853 const struct posix_acl_entry *acl_e = &acl->a_entries[n]; 854 ext_entry->e_tag = cpu_to_le16(acl_e->e_tag); 855 ext_entry->e_perm = cpu_to_le16(acl_e->e_perm); 856 switch(acl_e->e_tag) { 857 case ACL_USER: 858 ext_entry->e_id = 859 cpu_to_le32(from_kuid(user_ns, acl_e->e_uid)); 860 break; 861 case ACL_GROUP: 862 ext_entry->e_id = 863 cpu_to_le32(from_kgid(user_ns, acl_e->e_gid)); 864 break; 865 default: 866 ext_entry->e_id = cpu_to_le32(ACL_UNDEFINED_ID); 867 break; 868 } 869 } 870 return real_size; 871 } 872 EXPORT_SYMBOL (posix_acl_to_xattr); 873 874 /** 875 * vfs_posix_acl_to_xattr - convert from kernel to userspace representation 876 * @idmap: idmap of the mount 877 * @inode: inode the posix acls are set on 878 * @acl: the posix acls as represented by the vfs 879 * @buffer: the buffer into which to convert @acl 880 * @size: size of @buffer 881 * 882 * This converts @acl from the VFS representation in the filesystem idmapping 883 * to the uapi form reportable to userspace. And mount and caller idmappings 884 * are handled appropriately. 885 * 886 * Return: On success, the size of the stored uapi posix acls, on error a 887 * negative errno. 888 */ 889 static ssize_t vfs_posix_acl_to_xattr(struct mnt_idmap *idmap, 890 struct inode *inode, 891 const struct posix_acl *acl, void *buffer, 892 size_t size) 893 894 { 895 struct posix_acl_xattr_header *ext_acl = buffer; 896 struct posix_acl_xattr_entry *ext_entry; 897 struct user_namespace *fs_userns, *caller_userns; 898 struct user_namespace *mnt_userns; 899 ssize_t real_size, n; 900 vfsuid_t vfsuid; 901 vfsgid_t vfsgid; 902 903 real_size = posix_acl_xattr_size(acl->a_count); 904 if (!buffer) 905 return real_size; 906 if (real_size > size) 907 return -ERANGE; 908 909 ext_entry = (void *)(ext_acl + 1); 910 ext_acl->a_version = cpu_to_le32(POSIX_ACL_XATTR_VERSION); 911 912 fs_userns = i_user_ns(inode); 913 caller_userns = current_user_ns(); 914 mnt_userns = mnt_idmap_owner(idmap); 915 for (n=0; n < acl->a_count; n++, ext_entry++) { 916 const struct posix_acl_entry *acl_e = &acl->a_entries[n]; 917 ext_entry->e_tag = cpu_to_le16(acl_e->e_tag); 918 ext_entry->e_perm = cpu_to_le16(acl_e->e_perm); 919 switch(acl_e->e_tag) { 920 case ACL_USER: 921 vfsuid = make_vfsuid(mnt_userns, fs_userns, acl_e->e_uid); 922 ext_entry->e_id = cpu_to_le32(from_kuid( 923 caller_userns, vfsuid_into_kuid(vfsuid))); 924 break; 925 case ACL_GROUP: 926 vfsgid = make_vfsgid(mnt_userns, fs_userns, acl_e->e_gid); 927 ext_entry->e_id = cpu_to_le32(from_kgid( 928 caller_userns, vfsgid_into_kgid(vfsgid))); 929 break; 930 default: 931 ext_entry->e_id = cpu_to_le32(ACL_UNDEFINED_ID); 932 break; 933 } 934 } 935 return real_size; 936 } 937 938 int 939 set_posix_acl(struct mnt_idmap *idmap, struct dentry *dentry, 940 int type, struct posix_acl *acl) 941 { 942 struct inode *inode = d_inode(dentry); 943 944 if (!IS_POSIXACL(inode)) 945 return -EOPNOTSUPP; 946 if (!inode->i_op->set_acl) 947 return -EOPNOTSUPP; 948 949 if (type == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) 950 return acl ? -EACCES : 0; 951 if (!inode_owner_or_capable(idmap, inode)) 952 return -EPERM; 953 954 if (acl) { 955 int ret = posix_acl_valid(inode->i_sb->s_user_ns, acl); 956 if (ret) 957 return ret; 958 } 959 return inode->i_op->set_acl(idmap, dentry, acl, type); 960 } 961 EXPORT_SYMBOL(set_posix_acl); 962 963 static bool 964 posix_acl_xattr_list(struct dentry *dentry) 965 { 966 return IS_POSIXACL(d_backing_inode(dentry)); 967 } 968 969 const struct xattr_handler posix_acl_access_xattr_handler = { 970 .name = XATTR_NAME_POSIX_ACL_ACCESS, 971 .flags = ACL_TYPE_ACCESS, 972 .list = posix_acl_xattr_list, 973 }; 974 EXPORT_SYMBOL_GPL(posix_acl_access_xattr_handler); 975 976 const struct xattr_handler posix_acl_default_xattr_handler = { 977 .name = XATTR_NAME_POSIX_ACL_DEFAULT, 978 .flags = ACL_TYPE_DEFAULT, 979 .list = posix_acl_xattr_list, 980 }; 981 EXPORT_SYMBOL_GPL(posix_acl_default_xattr_handler); 982 983 int simple_set_acl(struct mnt_idmap *idmap, struct dentry *dentry, 984 struct posix_acl *acl, int type) 985 { 986 int error; 987 struct inode *inode = d_inode(dentry); 988 989 if (type == ACL_TYPE_ACCESS) { 990 error = posix_acl_update_mode(idmap, inode, 991 &inode->i_mode, &acl); 992 if (error) 993 return error; 994 } 995 996 inode->i_ctime = current_time(inode); 997 if (IS_I_VERSION(inode)) 998 inode_inc_iversion(inode); 999 set_cached_acl(inode, type, acl); 1000 return 0; 1001 } 1002 1003 int simple_acl_create(struct inode *dir, struct inode *inode) 1004 { 1005 struct posix_acl *default_acl, *acl; 1006 int error; 1007 1008 error = posix_acl_create(dir, &inode->i_mode, &default_acl, &acl); 1009 if (error) 1010 return error; 1011 1012 set_cached_acl(inode, ACL_TYPE_DEFAULT, default_acl); 1013 set_cached_acl(inode, ACL_TYPE_ACCESS, acl); 1014 1015 if (default_acl) 1016 posix_acl_release(default_acl); 1017 if (acl) 1018 posix_acl_release(acl); 1019 return 0; 1020 } 1021 1022 static int vfs_set_acl_idmapped_mnt(struct mnt_idmap *idmap, 1023 struct user_namespace *fs_userns, 1024 struct posix_acl *acl) 1025 { 1026 struct user_namespace *mnt_userns = mnt_idmap_owner(idmap); 1027 1028 for (int n = 0; n < acl->a_count; n++) { 1029 struct posix_acl_entry *acl_e = &acl->a_entries[n]; 1030 1031 switch (acl_e->e_tag) { 1032 case ACL_USER: 1033 acl_e->e_uid = from_vfsuid(mnt_userns, fs_userns, 1034 VFSUIDT_INIT(acl_e->e_uid)); 1035 break; 1036 case ACL_GROUP: 1037 acl_e->e_gid = from_vfsgid(mnt_userns, fs_userns, 1038 VFSGIDT_INIT(acl_e->e_gid)); 1039 break; 1040 } 1041 } 1042 1043 return 0; 1044 } 1045 1046 /** 1047 * vfs_set_acl - set posix acls 1048 * @idmap: idmap of the mount 1049 * @dentry: the dentry based on which to set the posix acls 1050 * @acl_name: the name of the posix acl 1051 * @kacl: the posix acls in the appropriate VFS format 1052 * 1053 * This function sets @kacl. The caller must all posix_acl_release() on @kacl 1054 * afterwards. 1055 * 1056 * Return: On success 0, on error negative errno. 1057 */ 1058 int vfs_set_acl(struct mnt_idmap *idmap, struct dentry *dentry, 1059 const char *acl_name, struct posix_acl *kacl) 1060 { 1061 int acl_type; 1062 int error; 1063 struct inode *inode = d_inode(dentry); 1064 struct inode *delegated_inode = NULL; 1065 1066 acl_type = posix_acl_type(acl_name); 1067 if (acl_type < 0) 1068 return -EINVAL; 1069 1070 if (kacl) { 1071 /* 1072 * If we're on an idmapped mount translate from mount specific 1073 * vfs{g,u}id_t into global filesystem k{g,u}id_t. 1074 * Afterwards we can cache the POSIX ACLs filesystem wide and - 1075 * if this is a filesystem with a backing store - ultimately 1076 * translate them to backing store values. 1077 */ 1078 error = vfs_set_acl_idmapped_mnt(idmap, i_user_ns(inode), kacl); 1079 if (error) 1080 return error; 1081 } 1082 1083 retry_deleg: 1084 inode_lock(inode); 1085 1086 /* 1087 * We only care about restrictions the inode struct itself places upon 1088 * us otherwise POSIX ACLs aren't subject to any VFS restrictions. 1089 */ 1090 error = may_write_xattr(idmap, inode); 1091 if (error) 1092 goto out_inode_unlock; 1093 1094 error = security_inode_set_acl(idmap, dentry, acl_name, kacl); 1095 if (error) 1096 goto out_inode_unlock; 1097 1098 error = try_break_deleg(inode, &delegated_inode); 1099 if (error) 1100 goto out_inode_unlock; 1101 1102 if (inode->i_opflags & IOP_XATTR) 1103 error = set_posix_acl(idmap, dentry, acl_type, kacl); 1104 else if (unlikely(is_bad_inode(inode))) 1105 error = -EIO; 1106 else 1107 error = -EOPNOTSUPP; 1108 if (!error) { 1109 fsnotify_xattr(dentry); 1110 evm_inode_post_set_acl(dentry, acl_name, kacl); 1111 } 1112 1113 out_inode_unlock: 1114 inode_unlock(inode); 1115 1116 if (delegated_inode) { 1117 error = break_deleg_wait(&delegated_inode); 1118 if (!error) 1119 goto retry_deleg; 1120 } 1121 1122 return error; 1123 } 1124 EXPORT_SYMBOL_GPL(vfs_set_acl); 1125 1126 /** 1127 * vfs_get_acl - get posix acls 1128 * @idmap: idmap of the mount 1129 * @dentry: the dentry based on which to retrieve the posix acls 1130 * @acl_name: the name of the posix acl 1131 * 1132 * This function retrieves @kacl from the filesystem. The caller must all 1133 * posix_acl_release() on @kacl. 1134 * 1135 * Return: On success POSIX ACLs in VFS format, on error negative errno. 1136 */ 1137 struct posix_acl *vfs_get_acl(struct mnt_idmap *idmap, 1138 struct dentry *dentry, const char *acl_name) 1139 { 1140 struct inode *inode = d_inode(dentry); 1141 struct posix_acl *acl; 1142 int acl_type, error; 1143 1144 acl_type = posix_acl_type(acl_name); 1145 if (acl_type < 0) 1146 return ERR_PTR(-EINVAL); 1147 1148 /* 1149 * The VFS has no restrictions on reading POSIX ACLs so calling 1150 * something like xattr_permission() isn't needed. Only LSMs get a say. 1151 */ 1152 error = security_inode_get_acl(idmap, dentry, acl_name); 1153 if (error) 1154 return ERR_PTR(error); 1155 1156 if (!IS_POSIXACL(inode)) 1157 return ERR_PTR(-EOPNOTSUPP); 1158 if (S_ISLNK(inode->i_mode)) 1159 return ERR_PTR(-EOPNOTSUPP); 1160 1161 acl = __get_acl(idmap, dentry, inode, acl_type); 1162 if (IS_ERR(acl)) 1163 return acl; 1164 if (!acl) 1165 return ERR_PTR(-ENODATA); 1166 1167 return acl; 1168 } 1169 EXPORT_SYMBOL_GPL(vfs_get_acl); 1170 1171 /** 1172 * vfs_remove_acl - remove posix acls 1173 * @idmap: idmap of the mount 1174 * @dentry: the dentry based on which to retrieve the posix acls 1175 * @acl_name: the name of the posix acl 1176 * 1177 * This function removes posix acls. 1178 * 1179 * Return: On success 0, on error negative errno. 1180 */ 1181 int vfs_remove_acl(struct mnt_idmap *idmap, struct dentry *dentry, 1182 const char *acl_name) 1183 { 1184 int acl_type; 1185 int error; 1186 struct inode *inode = d_inode(dentry); 1187 struct inode *delegated_inode = NULL; 1188 1189 acl_type = posix_acl_type(acl_name); 1190 if (acl_type < 0) 1191 return -EINVAL; 1192 1193 retry_deleg: 1194 inode_lock(inode); 1195 1196 /* 1197 * We only care about restrictions the inode struct itself places upon 1198 * us otherwise POSIX ACLs aren't subject to any VFS restrictions. 1199 */ 1200 error = may_write_xattr(idmap, inode); 1201 if (error) 1202 goto out_inode_unlock; 1203 1204 error = security_inode_remove_acl(idmap, dentry, acl_name); 1205 if (error) 1206 goto out_inode_unlock; 1207 1208 error = try_break_deleg(inode, &delegated_inode); 1209 if (error) 1210 goto out_inode_unlock; 1211 1212 if (inode->i_opflags & IOP_XATTR) 1213 error = set_posix_acl(idmap, dentry, acl_type, NULL); 1214 else if (unlikely(is_bad_inode(inode))) 1215 error = -EIO; 1216 else 1217 error = -EOPNOTSUPP; 1218 if (!error) { 1219 fsnotify_xattr(dentry); 1220 evm_inode_post_remove_acl(idmap, dentry, acl_name); 1221 } 1222 1223 out_inode_unlock: 1224 inode_unlock(inode); 1225 1226 if (delegated_inode) { 1227 error = break_deleg_wait(&delegated_inode); 1228 if (!error) 1229 goto retry_deleg; 1230 } 1231 1232 return error; 1233 } 1234 EXPORT_SYMBOL_GPL(vfs_remove_acl); 1235 1236 int do_set_acl(struct mnt_idmap *idmap, struct dentry *dentry, 1237 const char *acl_name, const void *kvalue, size_t size) 1238 { 1239 int error; 1240 struct posix_acl *acl = NULL; 1241 1242 if (size) { 1243 /* 1244 * Note that posix_acl_from_xattr() uses GFP_NOFS when it 1245 * probably doesn't need to here. 1246 */ 1247 acl = posix_acl_from_xattr(current_user_ns(), kvalue, size); 1248 if (IS_ERR(acl)) 1249 return PTR_ERR(acl); 1250 } 1251 1252 error = vfs_set_acl(idmap, dentry, acl_name, acl); 1253 posix_acl_release(acl); 1254 return error; 1255 } 1256 1257 ssize_t do_get_acl(struct mnt_idmap *idmap, struct dentry *dentry, 1258 const char *acl_name, void *kvalue, size_t size) 1259 { 1260 ssize_t error; 1261 struct posix_acl *acl; 1262 1263 acl = vfs_get_acl(idmap, dentry, acl_name); 1264 if (IS_ERR(acl)) 1265 return PTR_ERR(acl); 1266 1267 error = vfs_posix_acl_to_xattr(idmap, d_inode(dentry), 1268 acl, kvalue, size); 1269 posix_acl_release(acl); 1270 return error; 1271 } 1272