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/fsnotify.h> 30 #include <linux/filelock.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(!try_cmpxchg(p, &sentinel, acl))) 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 int found = 0; 381 vfsuid_t vfsuid; 382 vfsgid_t vfsgid; 383 384 want &= MAY_READ | MAY_WRITE | MAY_EXEC; 385 386 FOREACH_ACL_ENTRY(pa, acl, pe) { 387 switch(pa->e_tag) { 388 case ACL_USER_OBJ: 389 /* (May have been checked already) */ 390 vfsuid = i_uid_into_vfsuid(idmap, inode); 391 if (vfsuid_eq_kuid(vfsuid, current_fsuid())) 392 goto check_perm; 393 break; 394 case ACL_USER: 395 vfsuid = make_vfsuid(idmap, fs_userns, 396 pa->e_uid); 397 if (vfsuid_eq_kuid(vfsuid, current_fsuid())) 398 goto mask; 399 break; 400 case ACL_GROUP_OBJ: 401 vfsgid = i_gid_into_vfsgid(idmap, inode); 402 if (vfsgid_in_group_p(vfsgid)) { 403 found = 1; 404 if ((pa->e_perm & want) == want) 405 goto mask; 406 } 407 break; 408 case ACL_GROUP: 409 vfsgid = make_vfsgid(idmap, fs_userns, 410 pa->e_gid); 411 if (vfsgid_in_group_p(vfsgid)) { 412 found = 1; 413 if ((pa->e_perm & want) == want) 414 goto mask; 415 } 416 break; 417 case ACL_MASK: 418 break; 419 case ACL_OTHER: 420 if (found) 421 return -EACCES; 422 else 423 goto check_perm; 424 default: 425 return -EIO; 426 } 427 } 428 return -EIO; 429 430 mask: 431 for (mask_obj = pa+1; mask_obj != pe; mask_obj++) { 432 if (mask_obj->e_tag == ACL_MASK) { 433 if ((pa->e_perm & mask_obj->e_perm & want) == want) 434 return 0; 435 return -EACCES; 436 } 437 } 438 439 check_perm: 440 if ((pa->e_perm & want) == want) 441 return 0; 442 return -EACCES; 443 } 444 445 /* 446 * Modify acl when creating a new inode. The caller must ensure the acl is 447 * only referenced once. 448 * 449 * mode_p initially must contain the mode parameter to the open() / creat() 450 * system calls. All permissions that are not granted by the acl are removed. 451 * The permissions in the acl are changed to reflect the mode_p parameter. 452 */ 453 static int posix_acl_create_masq(struct posix_acl *acl, umode_t *mode_p) 454 { 455 struct posix_acl_entry *pa, *pe; 456 struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL; 457 umode_t mode = *mode_p; 458 int not_equiv = 0; 459 460 /* assert(atomic_read(acl->a_refcount) == 1); */ 461 462 FOREACH_ACL_ENTRY(pa, acl, pe) { 463 switch(pa->e_tag) { 464 case ACL_USER_OBJ: 465 pa->e_perm &= (mode >> 6) | ~S_IRWXO; 466 mode &= (pa->e_perm << 6) | ~S_IRWXU; 467 break; 468 469 case ACL_USER: 470 case ACL_GROUP: 471 not_equiv = 1; 472 break; 473 474 case ACL_GROUP_OBJ: 475 group_obj = pa; 476 break; 477 478 case ACL_OTHER: 479 pa->e_perm &= mode | ~S_IRWXO; 480 mode &= pa->e_perm | ~S_IRWXO; 481 break; 482 483 case ACL_MASK: 484 mask_obj = pa; 485 not_equiv = 1; 486 break; 487 488 default: 489 return -EIO; 490 } 491 } 492 493 if (mask_obj) { 494 mask_obj->e_perm &= (mode >> 3) | ~S_IRWXO; 495 mode &= (mask_obj->e_perm << 3) | ~S_IRWXG; 496 } else { 497 if (!group_obj) 498 return -EIO; 499 group_obj->e_perm &= (mode >> 3) | ~S_IRWXO; 500 mode &= (group_obj->e_perm << 3) | ~S_IRWXG; 501 } 502 503 *mode_p = (*mode_p & ~S_IRWXUGO) | mode; 504 return not_equiv; 505 } 506 507 /* 508 * Modify the ACL for the chmod syscall. 509 */ 510 static int __posix_acl_chmod_masq(struct posix_acl *acl, umode_t mode) 511 { 512 struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL; 513 struct posix_acl_entry *pa, *pe; 514 515 /* assert(atomic_read(acl->a_refcount) == 1); */ 516 517 FOREACH_ACL_ENTRY(pa, acl, pe) { 518 switch(pa->e_tag) { 519 case ACL_USER_OBJ: 520 pa->e_perm = (mode & S_IRWXU) >> 6; 521 break; 522 523 case ACL_USER: 524 case ACL_GROUP: 525 break; 526 527 case ACL_GROUP_OBJ: 528 group_obj = pa; 529 break; 530 531 case ACL_MASK: 532 mask_obj = pa; 533 break; 534 535 case ACL_OTHER: 536 pa->e_perm = (mode & S_IRWXO); 537 break; 538 539 default: 540 return -EIO; 541 } 542 } 543 544 if (mask_obj) { 545 mask_obj->e_perm = (mode & S_IRWXG) >> 3; 546 } else { 547 if (!group_obj) 548 return -EIO; 549 group_obj->e_perm = (mode & S_IRWXG) >> 3; 550 } 551 552 return 0; 553 } 554 555 int 556 __posix_acl_create(struct posix_acl **acl, gfp_t gfp, umode_t *mode_p) 557 { 558 struct posix_acl *clone = posix_acl_clone(*acl, gfp); 559 int err = -ENOMEM; 560 if (clone) { 561 err = posix_acl_create_masq(clone, mode_p); 562 if (err < 0) { 563 posix_acl_release(clone); 564 clone = NULL; 565 } 566 } 567 posix_acl_release(*acl); 568 *acl = clone; 569 return err; 570 } 571 EXPORT_SYMBOL(__posix_acl_create); 572 573 int 574 __posix_acl_chmod(struct posix_acl **acl, gfp_t gfp, umode_t mode) 575 { 576 struct posix_acl *clone = posix_acl_clone(*acl, gfp); 577 int err = -ENOMEM; 578 if (clone) { 579 err = __posix_acl_chmod_masq(clone, mode); 580 if (err) { 581 posix_acl_release(clone); 582 clone = NULL; 583 } 584 } 585 posix_acl_release(*acl); 586 *acl = clone; 587 return err; 588 } 589 EXPORT_SYMBOL(__posix_acl_chmod); 590 591 /** 592 * posix_acl_chmod - chmod a posix acl 593 * 594 * @idmap: idmap of the mount @inode was found from 595 * @dentry: dentry to check permissions on 596 * @mode: the new mode of @inode 597 * 598 * If the dentry has been found through an idmapped mount the idmap of 599 * the vfsmount must be passed through @idmap. This function will then 600 * take care to map the inode according to @idmap before checking 601 * permissions. On non-idmapped mounts or if permission checking is to be 602 * performed on the raw inode simply pass @nop_mnt_idmap. 603 */ 604 int 605 posix_acl_chmod(struct mnt_idmap *idmap, struct dentry *dentry, 606 umode_t mode) 607 { 608 struct inode *inode = d_inode(dentry); 609 struct posix_acl *acl; 610 int ret = 0; 611 612 if (!IS_POSIXACL(inode)) 613 return 0; 614 if (!inode->i_op->set_acl) 615 return -EOPNOTSUPP; 616 617 acl = get_inode_acl(inode, ACL_TYPE_ACCESS); 618 if (IS_ERR_OR_NULL(acl)) { 619 if (acl == ERR_PTR(-EOPNOTSUPP)) 620 return 0; 621 return PTR_ERR(acl); 622 } 623 624 ret = __posix_acl_chmod(&acl, GFP_KERNEL, mode); 625 if (ret) 626 return ret; 627 ret = inode->i_op->set_acl(idmap, dentry, acl, ACL_TYPE_ACCESS); 628 posix_acl_release(acl); 629 return ret; 630 } 631 EXPORT_SYMBOL(posix_acl_chmod); 632 633 int 634 posix_acl_create(struct inode *dir, umode_t *mode, 635 struct posix_acl **default_acl, struct posix_acl **acl) 636 { 637 struct posix_acl *p; 638 struct posix_acl *clone; 639 int ret; 640 641 *acl = NULL; 642 *default_acl = NULL; 643 644 if (S_ISLNK(*mode) || !IS_POSIXACL(dir)) 645 return 0; 646 647 p = get_inode_acl(dir, ACL_TYPE_DEFAULT); 648 if (!p || p == ERR_PTR(-EOPNOTSUPP)) { 649 *mode &= ~current_umask(); 650 return 0; 651 } 652 if (IS_ERR(p)) 653 return PTR_ERR(p); 654 655 ret = -ENOMEM; 656 clone = posix_acl_clone(p, GFP_NOFS); 657 if (!clone) 658 goto err_release; 659 660 ret = posix_acl_create_masq(clone, mode); 661 if (ret < 0) 662 goto err_release_clone; 663 664 if (ret == 0) 665 posix_acl_release(clone); 666 else 667 *acl = clone; 668 669 if (!S_ISDIR(*mode)) 670 posix_acl_release(p); 671 else 672 *default_acl = p; 673 674 return 0; 675 676 err_release_clone: 677 posix_acl_release(clone); 678 err_release: 679 posix_acl_release(p); 680 return ret; 681 } 682 EXPORT_SYMBOL_GPL(posix_acl_create); 683 684 /** 685 * posix_acl_update_mode - update mode in set_acl 686 * @idmap: idmap of the mount @inode was found from 687 * @inode: target inode 688 * @mode_p: mode (pointer) for update 689 * @acl: acl pointer 690 * 691 * Update the file mode when setting an ACL: compute the new file permission 692 * bits based on the ACL. In addition, if the ACL is equivalent to the new 693 * file mode, set *@acl to NULL to indicate that no ACL should be set. 694 * 695 * As with chmod, clear the setgid bit if the caller is not in the owning group 696 * or capable of CAP_FSETID (see inode_change_ok). 697 * 698 * If the inode has been found through an idmapped mount the idmap of 699 * the vfsmount must be passed through @idmap. This function will then 700 * take care to map the inode according to @idmap before checking 701 * permissions. On non-idmapped mounts or if permission checking is to be 702 * performed on the raw inode simply pass @nop_mnt_idmap. 703 * 704 * Called from set_acl inode operations. 705 */ 706 int posix_acl_update_mode(struct mnt_idmap *idmap, 707 struct inode *inode, umode_t *mode_p, 708 struct posix_acl **acl) 709 { 710 umode_t mode = inode->i_mode; 711 int error; 712 713 error = posix_acl_equiv_mode(*acl, &mode); 714 if (error < 0) 715 return error; 716 if (error == 0) 717 *acl = NULL; 718 if (!vfsgid_in_group_p(i_gid_into_vfsgid(idmap, inode)) && 719 !capable_wrt_inode_uidgid(idmap, inode, CAP_FSETID)) 720 mode &= ~S_ISGID; 721 *mode_p = mode; 722 return 0; 723 } 724 EXPORT_SYMBOL(posix_acl_update_mode); 725 726 /* 727 * Fix up the uids and gids in posix acl extended attributes in place. 728 */ 729 static int posix_acl_fix_xattr_common(const void *value, size_t size) 730 { 731 const struct posix_acl_xattr_header *header = value; 732 int count; 733 734 if (!header) 735 return -EINVAL; 736 if (size < sizeof(struct posix_acl_xattr_header)) 737 return -EINVAL; 738 if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION)) 739 return -EOPNOTSUPP; 740 741 count = posix_acl_xattr_count(size); 742 if (count < 0) 743 return -EINVAL; 744 if (count == 0) 745 return 0; 746 747 return count; 748 } 749 750 /** 751 * posix_acl_from_xattr - convert POSIX ACLs from backing store to VFS format 752 * @userns: the filesystem's idmapping 753 * @value: the uapi representation of POSIX ACLs 754 * @size: the size of @void 755 * 756 * Filesystems that store POSIX ACLs in the unaltered uapi format should use 757 * posix_acl_from_xattr() when reading them from the backing store and 758 * converting them into the struct posix_acl VFS format. The helper is 759 * specifically intended to be called from the acl inode operation. 760 * 761 * The posix_acl_from_xattr() function will map the raw {g,u}id values stored 762 * in ACL_{GROUP,USER} entries into idmapping in @userns. 763 * 764 * Note that posix_acl_from_xattr() does not take idmapped mounts into account. 765 * If it did it calling it from the get acl inode operation would return POSIX 766 * ACLs mapped according to an idmapped mount which would mean that the value 767 * couldn't be cached for the filesystem. Idmapped mounts are taken into 768 * account on the fly during permission checking or right at the VFS - 769 * userspace boundary before reporting them to the user. 770 * 771 * Return: Allocated struct posix_acl on success, NULL for a valid header but 772 * without actual POSIX ACL entries, or ERR_PTR() encoded error code. 773 */ 774 struct posix_acl *posix_acl_from_xattr(struct user_namespace *userns, 775 const void *value, size_t size) 776 { 777 const struct posix_acl_xattr_header *header = value; 778 const struct posix_acl_xattr_entry *entry = (const void *)(header + 1), *end; 779 int count; 780 struct posix_acl *acl; 781 struct posix_acl_entry *acl_e; 782 783 count = posix_acl_fix_xattr_common(value, size); 784 if (count < 0) 785 return ERR_PTR(count); 786 if (count == 0) 787 return NULL; 788 789 acl = posix_acl_alloc(count, GFP_NOFS); 790 if (!acl) 791 return ERR_PTR(-ENOMEM); 792 acl_e = acl->a_entries; 793 794 for (end = entry + count; entry != end; acl_e++, entry++) { 795 acl_e->e_tag = le16_to_cpu(entry->e_tag); 796 acl_e->e_perm = le16_to_cpu(entry->e_perm); 797 798 switch(acl_e->e_tag) { 799 case ACL_USER_OBJ: 800 case ACL_GROUP_OBJ: 801 case ACL_MASK: 802 case ACL_OTHER: 803 break; 804 805 case ACL_USER: 806 acl_e->e_uid = make_kuid(userns, 807 le32_to_cpu(entry->e_id)); 808 if (!uid_valid(acl_e->e_uid)) 809 goto fail; 810 break; 811 case ACL_GROUP: 812 acl_e->e_gid = make_kgid(userns, 813 le32_to_cpu(entry->e_id)); 814 if (!gid_valid(acl_e->e_gid)) 815 goto fail; 816 break; 817 818 default: 819 goto fail; 820 } 821 } 822 return acl; 823 824 fail: 825 posix_acl_release(acl); 826 return ERR_PTR(-EINVAL); 827 } 828 EXPORT_SYMBOL (posix_acl_from_xattr); 829 830 /* 831 * Convert from in-memory to extended attribute representation. 832 */ 833 int 834 posix_acl_to_xattr(struct user_namespace *user_ns, const struct posix_acl *acl, 835 void *buffer, size_t size) 836 { 837 struct posix_acl_xattr_header *ext_acl = buffer; 838 struct posix_acl_xattr_entry *ext_entry; 839 int real_size, n; 840 841 real_size = posix_acl_xattr_size(acl->a_count); 842 if (!buffer) 843 return real_size; 844 if (real_size > size) 845 return -ERANGE; 846 847 ext_entry = (void *)(ext_acl + 1); 848 ext_acl->a_version = cpu_to_le32(POSIX_ACL_XATTR_VERSION); 849 850 for (n=0; n < acl->a_count; n++, ext_entry++) { 851 const struct posix_acl_entry *acl_e = &acl->a_entries[n]; 852 ext_entry->e_tag = cpu_to_le16(acl_e->e_tag); 853 ext_entry->e_perm = cpu_to_le16(acl_e->e_perm); 854 switch(acl_e->e_tag) { 855 case ACL_USER: 856 ext_entry->e_id = 857 cpu_to_le32(from_kuid(user_ns, acl_e->e_uid)); 858 break; 859 case ACL_GROUP: 860 ext_entry->e_id = 861 cpu_to_le32(from_kgid(user_ns, acl_e->e_gid)); 862 break; 863 default: 864 ext_entry->e_id = cpu_to_le32(ACL_UNDEFINED_ID); 865 break; 866 } 867 } 868 return real_size; 869 } 870 EXPORT_SYMBOL (posix_acl_to_xattr); 871 872 /** 873 * vfs_posix_acl_to_xattr - convert from kernel to userspace representation 874 * @idmap: idmap of the mount 875 * @inode: inode the posix acls are set on 876 * @acl: the posix acls as represented by the vfs 877 * @buffer: the buffer into which to convert @acl 878 * @size: size of @buffer 879 * 880 * This converts @acl from the VFS representation in the filesystem idmapping 881 * to the uapi form reportable to userspace. And mount and caller idmappings 882 * are handled appropriately. 883 * 884 * Return: On success, the size of the stored uapi posix acls, on error a 885 * negative errno. 886 */ 887 static ssize_t vfs_posix_acl_to_xattr(struct mnt_idmap *idmap, 888 struct inode *inode, 889 const struct posix_acl *acl, void *buffer, 890 size_t size) 891 892 { 893 struct posix_acl_xattr_header *ext_acl = buffer; 894 struct posix_acl_xattr_entry *ext_entry; 895 struct user_namespace *fs_userns, *caller_userns; 896 ssize_t real_size, n; 897 vfsuid_t vfsuid; 898 vfsgid_t vfsgid; 899 900 real_size = posix_acl_xattr_size(acl->a_count); 901 if (!buffer) 902 return real_size; 903 if (real_size > size) 904 return -ERANGE; 905 906 ext_entry = (void *)(ext_acl + 1); 907 ext_acl->a_version = cpu_to_le32(POSIX_ACL_XATTR_VERSION); 908 909 fs_userns = i_user_ns(inode); 910 caller_userns = current_user_ns(); 911 for (n=0; n < acl->a_count; n++, ext_entry++) { 912 const struct posix_acl_entry *acl_e = &acl->a_entries[n]; 913 ext_entry->e_tag = cpu_to_le16(acl_e->e_tag); 914 ext_entry->e_perm = cpu_to_le16(acl_e->e_perm); 915 switch(acl_e->e_tag) { 916 case ACL_USER: 917 vfsuid = make_vfsuid(idmap, fs_userns, acl_e->e_uid); 918 ext_entry->e_id = cpu_to_le32(from_kuid( 919 caller_userns, vfsuid_into_kuid(vfsuid))); 920 break; 921 case ACL_GROUP: 922 vfsgid = make_vfsgid(idmap, fs_userns, acl_e->e_gid); 923 ext_entry->e_id = cpu_to_le32(from_kgid( 924 caller_userns, vfsgid_into_kgid(vfsgid))); 925 break; 926 default: 927 ext_entry->e_id = cpu_to_le32(ACL_UNDEFINED_ID); 928 break; 929 } 930 } 931 return real_size; 932 } 933 934 int 935 set_posix_acl(struct mnt_idmap *idmap, struct dentry *dentry, 936 int type, struct posix_acl *acl) 937 { 938 struct inode *inode = d_inode(dentry); 939 940 if (!IS_POSIXACL(inode)) 941 return -EOPNOTSUPP; 942 if (!inode->i_op->set_acl) 943 return -EOPNOTSUPP; 944 945 if (type == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) 946 return acl ? -EACCES : 0; 947 if (!inode_owner_or_capable(idmap, inode)) 948 return -EPERM; 949 950 if (acl) { 951 int ret = posix_acl_valid(inode->i_sb->s_user_ns, acl); 952 if (ret) 953 return ret; 954 } 955 return inode->i_op->set_acl(idmap, dentry, acl, type); 956 } 957 EXPORT_SYMBOL(set_posix_acl); 958 959 int posix_acl_listxattr(struct inode *inode, char **buffer, 960 ssize_t *remaining_size) 961 { 962 int err; 963 964 if (!IS_POSIXACL(inode)) 965 return 0; 966 967 if (inode->i_acl) { 968 err = xattr_list_one(buffer, remaining_size, 969 XATTR_NAME_POSIX_ACL_ACCESS); 970 if (err) 971 return err; 972 } 973 974 if (inode->i_default_acl) { 975 err = xattr_list_one(buffer, remaining_size, 976 XATTR_NAME_POSIX_ACL_DEFAULT); 977 if (err) 978 return err; 979 } 980 981 return 0; 982 } 983 984 static bool 985 posix_acl_xattr_list(struct dentry *dentry) 986 { 987 return IS_POSIXACL(d_backing_inode(dentry)); 988 } 989 990 /* 991 * nop_posix_acl_access - legacy xattr handler for access POSIX ACLs 992 * 993 * This is the legacy POSIX ACL access xattr handler. It is used by some 994 * filesystems to implement their ->listxattr() inode operation. New code 995 * should never use them. 996 */ 997 const struct xattr_handler nop_posix_acl_access = { 998 .name = XATTR_NAME_POSIX_ACL_ACCESS, 999 .list = posix_acl_xattr_list, 1000 }; 1001 EXPORT_SYMBOL_GPL(nop_posix_acl_access); 1002 1003 /* 1004 * nop_posix_acl_default - legacy xattr handler for default POSIX ACLs 1005 * 1006 * This is the legacy POSIX ACL default xattr handler. It is used by some 1007 * filesystems to implement their ->listxattr() inode operation. New code 1008 * should never use them. 1009 */ 1010 const struct xattr_handler nop_posix_acl_default = { 1011 .name = XATTR_NAME_POSIX_ACL_DEFAULT, 1012 .list = posix_acl_xattr_list, 1013 }; 1014 EXPORT_SYMBOL_GPL(nop_posix_acl_default); 1015 1016 int simple_set_acl(struct mnt_idmap *idmap, struct dentry *dentry, 1017 struct posix_acl *acl, int type) 1018 { 1019 int error; 1020 struct inode *inode = d_inode(dentry); 1021 1022 if (type == ACL_TYPE_ACCESS) { 1023 error = posix_acl_update_mode(idmap, inode, 1024 &inode->i_mode, &acl); 1025 if (error) 1026 return error; 1027 } 1028 1029 inode_set_ctime_current(inode); 1030 if (IS_I_VERSION(inode)) 1031 inode_inc_iversion(inode); 1032 set_cached_acl(inode, type, acl); 1033 return 0; 1034 } 1035 1036 int simple_acl_create(struct inode *dir, struct inode *inode) 1037 { 1038 struct posix_acl *default_acl, *acl; 1039 int error; 1040 1041 error = posix_acl_create(dir, &inode->i_mode, &default_acl, &acl); 1042 if (error) 1043 return error; 1044 1045 set_cached_acl(inode, ACL_TYPE_DEFAULT, default_acl); 1046 set_cached_acl(inode, ACL_TYPE_ACCESS, acl); 1047 1048 if (default_acl) 1049 posix_acl_release(default_acl); 1050 if (acl) 1051 posix_acl_release(acl); 1052 return 0; 1053 } 1054 1055 static int vfs_set_acl_idmapped_mnt(struct mnt_idmap *idmap, 1056 struct user_namespace *fs_userns, 1057 struct posix_acl *acl) 1058 { 1059 for (int n = 0; n < acl->a_count; n++) { 1060 struct posix_acl_entry *acl_e = &acl->a_entries[n]; 1061 1062 switch (acl_e->e_tag) { 1063 case ACL_USER: 1064 acl_e->e_uid = from_vfsuid(idmap, fs_userns, 1065 VFSUIDT_INIT(acl_e->e_uid)); 1066 break; 1067 case ACL_GROUP: 1068 acl_e->e_gid = from_vfsgid(idmap, fs_userns, 1069 VFSGIDT_INIT(acl_e->e_gid)); 1070 break; 1071 } 1072 } 1073 1074 return 0; 1075 } 1076 1077 /** 1078 * vfs_set_acl - set posix acls 1079 * @idmap: idmap of the mount 1080 * @dentry: the dentry based on which to set the posix acls 1081 * @acl_name: the name of the posix acl 1082 * @kacl: the posix acls in the appropriate VFS format 1083 * 1084 * This function sets @kacl. The caller must all posix_acl_release() on @kacl 1085 * afterwards. 1086 * 1087 * Return: On success 0, on error negative errno. 1088 */ 1089 int vfs_set_acl(struct mnt_idmap *idmap, struct dentry *dentry, 1090 const char *acl_name, struct posix_acl *kacl) 1091 { 1092 int acl_type; 1093 int error; 1094 struct inode *inode = d_inode(dentry); 1095 struct inode *delegated_inode = NULL; 1096 1097 acl_type = posix_acl_type(acl_name); 1098 if (acl_type < 0) 1099 return -EINVAL; 1100 1101 if (kacl) { 1102 /* 1103 * If we're on an idmapped mount translate from mount specific 1104 * vfs{g,u}id_t into global filesystem k{g,u}id_t. 1105 * Afterwards we can cache the POSIX ACLs filesystem wide and - 1106 * if this is a filesystem with a backing store - ultimately 1107 * translate them to backing store values. 1108 */ 1109 error = vfs_set_acl_idmapped_mnt(idmap, i_user_ns(inode), kacl); 1110 if (error) 1111 return error; 1112 } 1113 1114 retry_deleg: 1115 inode_lock(inode); 1116 1117 /* 1118 * We only care about restrictions the inode struct itself places upon 1119 * us otherwise POSIX ACLs aren't subject to any VFS restrictions. 1120 */ 1121 error = may_write_xattr(idmap, inode); 1122 if (error) 1123 goto out_inode_unlock; 1124 1125 error = security_inode_set_acl(idmap, dentry, acl_name, kacl); 1126 if (error) 1127 goto out_inode_unlock; 1128 1129 error = try_break_deleg(inode, &delegated_inode); 1130 if (error) 1131 goto out_inode_unlock; 1132 1133 if (likely(!is_bad_inode(inode))) 1134 error = set_posix_acl(idmap, dentry, acl_type, kacl); 1135 else 1136 error = -EIO; 1137 if (!error) { 1138 fsnotify_xattr(dentry); 1139 security_inode_post_set_acl(dentry, acl_name, kacl); 1140 } 1141 1142 out_inode_unlock: 1143 inode_unlock(inode); 1144 1145 if (delegated_inode) { 1146 error = break_deleg_wait(&delegated_inode); 1147 if (!error) 1148 goto retry_deleg; 1149 } 1150 1151 return error; 1152 } 1153 EXPORT_SYMBOL_GPL(vfs_set_acl); 1154 1155 /** 1156 * vfs_get_acl - get posix acls 1157 * @idmap: idmap of the mount 1158 * @dentry: the dentry based on which to retrieve the posix acls 1159 * @acl_name: the name of the posix acl 1160 * 1161 * This function retrieves @kacl from the filesystem. The caller must all 1162 * posix_acl_release() on @kacl. 1163 * 1164 * Return: On success POSIX ACLs in VFS format, on error negative errno. 1165 */ 1166 struct posix_acl *vfs_get_acl(struct mnt_idmap *idmap, 1167 struct dentry *dentry, const char *acl_name) 1168 { 1169 struct inode *inode = d_inode(dentry); 1170 struct posix_acl *acl; 1171 int acl_type, error; 1172 1173 acl_type = posix_acl_type(acl_name); 1174 if (acl_type < 0) 1175 return ERR_PTR(-EINVAL); 1176 1177 /* 1178 * The VFS has no restrictions on reading POSIX ACLs so calling 1179 * something like xattr_permission() isn't needed. Only LSMs get a say. 1180 */ 1181 error = security_inode_get_acl(idmap, dentry, acl_name); 1182 if (error) 1183 return ERR_PTR(error); 1184 1185 if (!IS_POSIXACL(inode)) 1186 return ERR_PTR(-EOPNOTSUPP); 1187 if (S_ISLNK(inode->i_mode)) 1188 return ERR_PTR(-EOPNOTSUPP); 1189 1190 acl = __get_acl(idmap, dentry, inode, acl_type); 1191 if (IS_ERR(acl)) 1192 return acl; 1193 if (!acl) 1194 return ERR_PTR(-ENODATA); 1195 1196 return acl; 1197 } 1198 EXPORT_SYMBOL_GPL(vfs_get_acl); 1199 1200 /** 1201 * vfs_remove_acl - remove posix acls 1202 * @idmap: idmap of the mount 1203 * @dentry: the dentry based on which to retrieve the posix acls 1204 * @acl_name: the name of the posix acl 1205 * 1206 * This function removes posix acls. 1207 * 1208 * Return: On success 0, on error negative errno. 1209 */ 1210 int vfs_remove_acl(struct mnt_idmap *idmap, struct dentry *dentry, 1211 const char *acl_name) 1212 { 1213 int acl_type; 1214 int error; 1215 struct inode *inode = d_inode(dentry); 1216 struct inode *delegated_inode = NULL; 1217 1218 acl_type = posix_acl_type(acl_name); 1219 if (acl_type < 0) 1220 return -EINVAL; 1221 1222 retry_deleg: 1223 inode_lock(inode); 1224 1225 /* 1226 * We only care about restrictions the inode struct itself places upon 1227 * us otherwise POSIX ACLs aren't subject to any VFS restrictions. 1228 */ 1229 error = may_write_xattr(idmap, inode); 1230 if (error) 1231 goto out_inode_unlock; 1232 1233 error = security_inode_remove_acl(idmap, dentry, acl_name); 1234 if (error) 1235 goto out_inode_unlock; 1236 1237 error = try_break_deleg(inode, &delegated_inode); 1238 if (error) 1239 goto out_inode_unlock; 1240 1241 if (likely(!is_bad_inode(inode))) 1242 error = set_posix_acl(idmap, dentry, acl_type, NULL); 1243 else 1244 error = -EIO; 1245 if (!error) { 1246 fsnotify_xattr(dentry); 1247 security_inode_post_remove_acl(idmap, dentry, acl_name); 1248 } 1249 1250 out_inode_unlock: 1251 inode_unlock(inode); 1252 1253 if (delegated_inode) { 1254 error = break_deleg_wait(&delegated_inode); 1255 if (!error) 1256 goto retry_deleg; 1257 } 1258 1259 return error; 1260 } 1261 EXPORT_SYMBOL_GPL(vfs_remove_acl); 1262 1263 int do_set_acl(struct mnt_idmap *idmap, struct dentry *dentry, 1264 const char *acl_name, const void *kvalue, size_t size) 1265 { 1266 int error; 1267 struct posix_acl *acl = NULL; 1268 1269 if (size) { 1270 /* 1271 * Note that posix_acl_from_xattr() uses GFP_NOFS when it 1272 * probably doesn't need to here. 1273 */ 1274 acl = posix_acl_from_xattr(current_user_ns(), kvalue, size); 1275 if (IS_ERR(acl)) 1276 return PTR_ERR(acl); 1277 } 1278 1279 error = vfs_set_acl(idmap, dentry, acl_name, acl); 1280 posix_acl_release(acl); 1281 return error; 1282 } 1283 1284 ssize_t do_get_acl(struct mnt_idmap *idmap, struct dentry *dentry, 1285 const char *acl_name, void *kvalue, size_t size) 1286 { 1287 ssize_t error; 1288 struct posix_acl *acl; 1289 1290 acl = vfs_get_acl(idmap, dentry, acl_name); 1291 if (IS_ERR(acl)) 1292 return PTR_ERR(acl); 1293 1294 error = vfs_posix_acl_to_xattr(idmap, d_inode(dentry), 1295 acl, kvalue, size); 1296 posix_acl_release(acl); 1297 return error; 1298 } 1299