fs/posix_acl.c

   1 /*
   2  * Copyright (C) 2002,2003 by Andreas Gruenbacher <a.gruenbacher@computer.org>
   3  *
   4  * Fixes from William Schumacher incorporated on 15 March 2001.
   5  *    (Reported by Charles Bertsch, <CBertsch@microtest.com>).
   6  */
   7
   8 /*
   9  *  This file contains generic functions for manipulating
  10  *  POSIX 1003.1e draft standard 17 ACLs.
  11  */
  12
  13 #include <linux/kernel.h>
  14 #include <linux/slab.h>
  15 #include <linux/atomic.h>
  16 #include <linux/fs.h>
  17 #include <linux/sched.h>
  18 #include <linux/posix_acl.h>
  19 #include <linux/posix_acl_xattr.h>
  20 #include <linux/xattr.h>
  21 #include <linux/export.h>
  22 #include <linux/user_namespace.h>
  23
  24 static struct posix_acl **acl_by_type(struct inode *inode, int type)
  25 {
  26         switch (type) {
  27         case ACL_TYPE_ACCESS:
  28                 return &inode->i_acl;
  29         case ACL_TYPE_DEFAULT:
  30                 return &inode->i_default_acl;
  31         default:
  32                 BUG();
  33         }
  34 }
  35
  36 struct posix_acl *get_cached_acl(struct inode *inode, int type)
  37 {
  38         struct posix_acl **p = acl_by_type(inode, type);
  39         struct posix_acl *acl;
  40
  41         for (;;) {
  42                 rcu_read_lock();
  43                 acl = rcu_dereference(*p);
  44                 if (!acl || is_uncached_acl(acl) ||
  45                     atomic_inc_not_zero(&acl->a_refcount))
  46                         break;
  47                 rcu_read_unlock();
  48                 cpu_relax();
  49         }
  50         rcu_read_unlock();
  51         return acl;
  52 }
  53 EXPORT_SYMBOL(get_cached_acl);
  54
  55 struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type)
  56 {
  57         return rcu_dereference(*acl_by_type(inode, type));
  58 }
  59 EXPORT_SYMBOL(get_cached_acl_rcu);
  60
  61 void set_cached_acl(struct inode *inode, int type, struct posix_acl *acl)
  62 {
  63         struct posix_acl **p = acl_by_type(inode, type);
  64         struct posix_acl *old;
  65
  66         old = xchg(p, posix_acl_dup(acl));
  67         if (!is_uncached_acl(old))
  68                 posix_acl_release(old);
  69 }
  70 EXPORT_SYMBOL(set_cached_acl);
  71
  72 static void __forget_cached_acl(struct posix_acl **p)
  73 {
  74         struct posix_acl *old;
  75
  76         old = xchg(p, ACL_NOT_CACHED);
  77         if (!is_uncached_acl(old))
  78                 posix_acl_release(old);
  79 }
  80
  81 void forget_cached_acl(struct inode *inode, int type)
  82 {
  83         __forget_cached_acl(acl_by_type(inode, type));
  84 }
  85 EXPORT_SYMBOL(forget_cached_acl);
  86
  87 void forget_all_cached_acls(struct inode *inode)
  88 {
  89         __forget_cached_acl(&inode->i_acl);
  90         __forget_cached_acl(&inode->i_default_acl);
  91 }
  92 EXPORT_SYMBOL(forget_all_cached_acls);
  93
  94 struct posix_acl *get_acl(struct inode *inode, int type)
  95 {
  96         void *sentinel;
  97         struct posix_acl **p;
  98         struct posix_acl *acl;
  99
 100         /*
 101          * The sentinel is used to detect when another operation like
 102          * set_cached_acl() or forget_cached_acl() races with get_acl().
 103          * It is guaranteed that is_uncached_acl(sentinel) is true.
 104          */
 105
 106         acl = get_cached_acl(inode, type);
 107         if (!is_uncached_acl(acl))
 108                 return acl;
 109
 110         if (!IS_POSIXACL(inode))
 111                 return NULL;
 112
 113         sentinel = uncached_acl_sentinel(current);
 114         p = acl_by_type(inode, type);
 115
 116         /*
 117          * If the ACL isn't being read yet, set our sentinel.  Otherwise, the
 118          * current value of the ACL will not be ACL_NOT_CACHED and so our own
 119          * sentinel will not be set; another task will update the cache.  We
 120          * could wait for that other task to complete its job, but it's easier
 121          * to just call ->get_acl to fetch the ACL ourself.  (This is going to
 122          * be an unlikely race.)
 123          */
 124         if (cmpxchg(p, ACL_NOT_CACHED, sentinel) != ACL_NOT_CACHED)
 125                 /* fall through */ ;
 126
 127         /*
 128          * Normally, the ACL returned by ->get_acl will be cached.
 129          * A filesystem can prevent that by calling
 130          * forget_cached_acl(inode, type) in ->get_acl.
 131          *
 132          * If the filesystem doesn't have a get_acl() function at all, we'll
 133          * just create the negative cache entry.
 134          */
 135         if (!inode->i_op->get_acl) {
 136                 set_cached_acl(inode, type, NULL);
 137                 return NULL;
 138         }
 139         acl = inode->i_op->get_acl(inode, type);
 140
 141         if (IS_ERR(acl)) {
 142                 /*
 143                  * Remove our sentinel so that we don't block future attempts
 144                  * to cache the ACL.
 145                  */
 146                 cmpxchg(p, sentinel, ACL_NOT_CACHED);
 147                 return acl;
 148         }
 149
 150         /*
 151          * Cache the result, but only if our sentinel is still in place.
 152          */
 153         posix_acl_dup(acl);
 154         if (unlikely(cmpxchg(p, sentinel, acl) != sentinel))
 155                 posix_acl_release(acl);
 156         return acl;
 157 }
 158 EXPORT_SYMBOL(get_acl);
 159
 160 /*
 161  * Init a fresh posix_acl
 162  */
 163 void
 164 posix_acl_init(struct posix_acl *acl, int count)
 165 {
 166         atomic_set(&acl->a_refcount, 1);
 167         acl->a_count = count;
 168 }
 169 EXPORT_SYMBOL(posix_acl_init);
 170
 171 /*
 172  * Allocate a new ACL with the specified number of entries.
 173  */
 174 struct posix_acl *
 175 posix_acl_alloc(int count, gfp_t flags)
 176 {
 177         const size_t size = sizeof(struct posix_acl) +
 178                             count * sizeof(struct posix_acl_entry);
 179         struct posix_acl *acl = kmalloc(size, flags);
 180         if (acl)
 181                 posix_acl_init(acl, count);
 182         return acl;
 183 }
 184 EXPORT_SYMBOL(posix_acl_alloc);
 185
 186 /*
 187  * Clone an ACL.
 188  */
 189 static struct posix_acl *
 190 posix_acl_clone(const struct posix_acl *acl, gfp_t flags)
 191 {
 192         struct posix_acl *clone = NULL;
 193
 194         if (acl) {
 195                 int size = sizeof(struct posix_acl) + acl->a_count *
 196                            sizeof(struct posix_acl_entry);
 197                 clone = kmemdup(acl, size, flags);
 198                 if (clone)
 199                         atomic_set(&clone->a_refcount, 1);
 200         }
 201         return clone;
 202 }
 203
 204 /*
 205  * Check if an acl is valid. Returns 0 if it is, or -E... otherwise.
 206  */
 207 int
 208 posix_acl_valid(struct user_namespace *user_ns, const struct posix_acl *acl)
 209 {
 210         const struct posix_acl_entry *pa, *pe;
 211         int state = ACL_USER_OBJ;
 212         int needs_mask = 0;
 213
 214         FOREACH_ACL_ENTRY(pa, acl, pe) {
 215                 if (pa->e_perm & ~(ACL_READ|ACL_WRITE|ACL_EXECUTE))
 216                         return -EINVAL;
 217                 switch (pa->e_tag) {
 218                         case ACL_USER_OBJ:
 219                                 if (state == ACL_USER_OBJ) {
 220                                         state = ACL_USER;
 221                                         break;
 222                                 }
 223                                 return -EINVAL;
 224
 225                         case ACL_USER:
 226                                 if (state != ACL_USER)
 227                                         return -EINVAL;
 228                                 if (!kuid_has_mapping(user_ns, pa->e_uid))
 229                                         return -EINVAL;
 230                                 needs_mask = 1;
 231                                 break;
 232
 233                         case ACL_GROUP_OBJ:
 234                                 if (state == ACL_USER) {
 235                                         state = ACL_GROUP;
 236                                         break;
 237                                 }
 238                                 return -EINVAL;
 239
 240                         case ACL_GROUP:
 241                                 if (state != ACL_GROUP)
 242                                         return -EINVAL;
 243                                 if (!kgid_has_mapping(user_ns, pa->e_gid))
 244                                         return -EINVAL;
 245                                 needs_mask = 1;
 246                                 break;
 247
 248                         case ACL_MASK:
 249                                 if (state != ACL_GROUP)
 250                                         return -EINVAL;
 251                                 state = ACL_OTHER;
 252                                 break;
 253
 254                         case ACL_OTHER:
 255                                 if (state == ACL_OTHER ||
 256                                     (state == ACL_GROUP && !needs_mask)) {
 257                                         state = 0;
 258                                         break;
 259                                 }
 260                                 return -EINVAL;
 261
 262                         default:
 263                                 return -EINVAL;
 264                 }
 265         }
 266         if (state == 0)
 267                 return 0;
 268         return -EINVAL;
 269 }
 270 EXPORT_SYMBOL(posix_acl_valid);
 271
 272 /*
 273  * Returns 0 if the acl can be exactly represented in the traditional
 274  * file mode permission bits, or else 1. Returns -E... on error.
 275  */
 276 int
 277 posix_acl_equiv_mode(const struct posix_acl *acl, umode_t *mode_p)
 278 {
 279         const struct posix_acl_entry *pa, *pe;
 280         umode_t mode = 0;
 281         int not_equiv = 0;
 282
 283         /*
 284          * A null ACL can always be presented as mode bits.
 285          */
 286         if (!acl)
 287                 return 0;
 288
 289         FOREACH_ACL_ENTRY(pa, acl, pe) {
 290                 switch (pa->e_tag) {
 291                         case ACL_USER_OBJ:
 292                                 mode |= (pa->e_perm & S_IRWXO) << 6;
 293                                 break;
 294                         case ACL_GROUP_OBJ:
 295                                 mode |= (pa->e_perm & S_IRWXO) << 3;
 296                                 break;
 297                         case ACL_OTHER:
 298                                 mode |= pa->e_perm & S_IRWXO;
 299                                 break;
 300                         case ACL_MASK:
 301                                 mode = (mode & ~S_IRWXG) |
 302                                        ((pa->e_perm & S_IRWXO) << 3);
 303                                 not_equiv = 1;
 304                                 break;
 305                         case ACL_USER:
 306                         case ACL_GROUP:
 307                                 not_equiv = 1;
 308                                 break;
 309                         default:
 310                                 return -EINVAL;
 311                 }
 312         }
 313         if (mode_p)
 314                 *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
 315         return not_equiv;
 316 }
 317 EXPORT_SYMBOL(posix_acl_equiv_mode);
 318
 319 /*
 320  * Create an ACL representing the file mode permission bits of an inode.
 321  */
 322 struct posix_acl *
 323 posix_acl_from_mode(umode_t mode, gfp_t flags)
 324 {
 325         struct posix_acl *acl = posix_acl_alloc(3, flags);
 326         if (!acl)
 327                 return ERR_PTR(-ENOMEM);
 328
 329         acl->a_entries[0].e_tag  = ACL_USER_OBJ;
 330         acl->a_entries[0].e_perm = (mode & S_IRWXU) >> 6;
 331
 332         acl->a_entries[1].e_tag  = ACL_GROUP_OBJ;
 333         acl->a_entries[1].e_perm = (mode & S_IRWXG) >> 3;
 334
 335         acl->a_entries[2].e_tag  = ACL_OTHER;
 336         acl->a_entries[2].e_perm = (mode & S_IRWXO);
 337         return acl;
 338 }
 339 EXPORT_SYMBOL(posix_acl_from_mode);
 340
 341 /*
 342  * Return 0 if current is granted want access to the inode
 343  * by the acl. Returns -E... otherwise.
 344  */
 345 int
 346 posix_acl_permission(struct inode *inode, const struct posix_acl *acl, int want)
 347 {
 348         const struct posix_acl_entry *pa, *pe, *mask_obj;
 349         int found = 0;
 350
 351         want &= MAY_READ | MAY_WRITE | MAY_EXEC | MAY_NOT_BLOCK;
 352
 353         FOREACH_ACL_ENTRY(pa, acl, pe) {
 354                 switch(pa->e_tag) {
 355                         case ACL_USER_OBJ:
 356                                 /* (May have been checked already) */
 357                                 if (uid_eq(inode->i_uid, current_fsuid()))
 358                                         goto check_perm;
 359                                 break;
 360                         case ACL_USER:
 361                                 if (uid_eq(pa->e_uid, current_fsuid()))
 362                                         goto mask;
 363                                 break;
 364                         case ACL_GROUP_OBJ:
 365                                 if (in_group_p(inode->i_gid)) {
 366                                         found = 1;
 367                                         if ((pa->e_perm & want) == want)
 368                                                 goto mask;
 369                                 }
 370                                 break;
 371                         case ACL_GROUP:
 372                                 if (in_group_p(pa->e_gid)) {
 373                                         found = 1;
 374                                         if ((pa->e_perm & want) == want)
 375                                                 goto mask;
 376                                 }
 377                                 break;
 378                         case ACL_MASK:
 379                                 break;
 380                         case ACL_OTHER:
 381                                 if (found)
 382                                         return -EACCES;
 383                                 else
 384                                         goto check_perm;
 385                         default:
 386                                 return -EIO;
 387                 }
 388         }
 389         return -EIO;
 390
 391 mask:
 392         for (mask_obj = pa+1; mask_obj != pe; mask_obj++) {
 393                 if (mask_obj->e_tag == ACL_MASK) {
 394                         if ((pa->e_perm & mask_obj->e_perm & want) == want)
 395                                 return 0;
 396                         return -EACCES;
 397                 }
 398         }
 399
 400 check_perm:
 401         if ((pa->e_perm & want) == want)
 402                 return 0;
 403         return -EACCES;
 404 }
 405
 406 /*
 407  * Modify acl when creating a new inode. The caller must ensure the acl is
 408  * only referenced once.
 409  *
 410  * mode_p initially must contain the mode parameter to the open() / creat()
 411  * system calls. All permissions that are not granted by the acl are removed.
 412  * The permissions in the acl are changed to reflect the mode_p parameter.
 413  */
 414 static int posix_acl_create_masq(struct posix_acl *acl, umode_t *mode_p)
 415 {
 416         struct posix_acl_entry *pa, *pe;
 417         struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
 418         umode_t mode = *mode_p;
 419         int not_equiv = 0;
 420
 421         /* assert(atomic_read(acl->a_refcount) == 1); */
 422
 423         FOREACH_ACL_ENTRY(pa, acl, pe) {
 424                 switch(pa->e_tag) {
 425                         case ACL_USER_OBJ:
 426                                 pa->e_perm &= (mode >> 6) | ~S_IRWXO;
 427                                 mode &= (pa->e_perm << 6) | ~S_IRWXU;
 428                                 break;
 429
 430                         case ACL_USER:
 431                         case ACL_GROUP:
 432                                 not_equiv = 1;
 433                                 break;
 434
 435                         case ACL_GROUP_OBJ:
 436                                 group_obj = pa;
 437                                 break;
 438
 439                         case ACL_OTHER:
 440                                 pa->e_perm &= mode | ~S_IRWXO;
 441                                 mode &= pa->e_perm | ~S_IRWXO;
 442                                 break;
 443
 444                         case ACL_MASK:
 445                                 mask_obj = pa;
 446                                 not_equiv = 1;
 447                                 break;
 448
 449                         default:
 450                                 return -EIO;
 451                 }
 452         }
 453
 454         if (mask_obj) {
 455                 mask_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
 456                 mode &= (mask_obj->e_perm << 3) | ~S_IRWXG;
 457         } else {
 458                 if (!group_obj)
 459                         return -EIO;
 460                 group_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
 461                 mode &= (group_obj->e_perm << 3) | ~S_IRWXG;
 462         }
 463
 464         *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
 465         return not_equiv;
 466 }
 467
 468 /*
 469  * Modify the ACL for the chmod syscall.
 470  */
 471 static int __posix_acl_chmod_masq(struct posix_acl *acl, umode_t mode)
 472 {
 473         struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
 474         struct posix_acl_entry *pa, *pe;
 475
 476         /* assert(atomic_read(acl->a_refcount) == 1); */
 477
 478         FOREACH_ACL_ENTRY(pa, acl, pe) {
 479                 switch(pa->e_tag) {
 480                         case ACL_USER_OBJ:
 481                                 pa->e_perm = (mode & S_IRWXU) >> 6;
 482                                 break;
 483
 484                         case ACL_USER:
 485                         case ACL_GROUP:
 486                                 break;
 487
 488                         case ACL_GROUP_OBJ:
 489                                 group_obj = pa;
 490                                 break;
 491
 492                         case ACL_MASK:
 493                                 mask_obj = pa;
 494                                 break;
 495
 496                         case ACL_OTHER:
 497                                 pa->e_perm = (mode & S_IRWXO);
 498                                 break;
 499
 500                         default:
 501                                 return -EIO;
 502                 }
 503         }
 504
 505         if (mask_obj) {
 506                 mask_obj->e_perm = (mode & S_IRWXG) >> 3;
 507         } else {
 508                 if (!group_obj)
 509                         return -EIO;
 510                 group_obj->e_perm = (mode & S_IRWXG) >> 3;
 511         }
 512
 513         return 0;
 514 }
 515
 516 int
 517 __posix_acl_create(struct posix_acl **acl, gfp_t gfp, umode_t *mode_p)
 518 {
 519         struct posix_acl *clone = posix_acl_clone(*acl, gfp);
 520         int err = -ENOMEM;
 521         if (clone) {
 522                 err = posix_acl_create_masq(clone, mode_p);
 523                 if (err < 0) {
 524                         posix_acl_release(clone);
 525                         clone = NULL;
 526                 }
 527         }
 528         posix_acl_release(*acl);
 529         *acl = clone;
 530         return err;
 531 }
 532 EXPORT_SYMBOL(__posix_acl_create);
 533
 534 int
 535 __posix_acl_chmod(struct posix_acl **acl, gfp_t gfp, umode_t mode)
 536 {
 537         struct posix_acl *clone = posix_acl_clone(*acl, gfp);
 538         int err = -ENOMEM;
 539         if (clone) {
 540                 err = __posix_acl_chmod_masq(clone, mode);
 541                 if (err) {
 542                         posix_acl_release(clone);
 543                         clone = NULL;
 544                 }
 545         }
 546         posix_acl_release(*acl);
 547         *acl = clone;
 548         return err;
 549 }
 550 EXPORT_SYMBOL(__posix_acl_chmod);
 551
 552 int
 553 posix_acl_chmod(struct inode *inode, umode_t mode)
 554 {
 555         struct posix_acl *acl;
 556         int ret = 0;
 557
 558         if (!IS_POSIXACL(inode))
 559                 return 0;
 560         if (!inode->i_op->set_acl)
 561                 return -EOPNOTSUPP;
 562
 563         acl = get_acl(inode, ACL_TYPE_ACCESS);
 564         if (IS_ERR_OR_NULL(acl)) {
 565                 if (acl == ERR_PTR(-EOPNOTSUPP))
 566                         return 0;
 567                 return PTR_ERR(acl);
 568         }
 569
 570         ret = __posix_acl_chmod(&acl, GFP_KERNEL, mode);
 571         if (ret)
 572                 return ret;
 573         ret = inode->i_op->set_acl(inode, acl, ACL_TYPE_ACCESS);
 574         posix_acl_release(acl);
 575         return ret;
 576 }
 577 EXPORT_SYMBOL(posix_acl_chmod);
 578
 579 int
 580 posix_acl_create(struct inode *dir, umode_t *mode,
 581                 struct posix_acl **default_acl, struct posix_acl **acl)
 582 {
 583         struct posix_acl *p;
 584         struct posix_acl *clone;
 585         int ret;
 586
 587         *acl = NULL;
 588         *default_acl = NULL;
 589
 590         if (S_ISLNK(*mode) || !IS_POSIXACL(dir))
 591                 return 0;
 592
 593         p = get_acl(dir, ACL_TYPE_DEFAULT);
 594         if (!p || p == ERR_PTR(-EOPNOTSUPP)) {
 595                 *mode &= ~current_umask();
 596                 return 0;
 597         }
 598         if (IS_ERR(p))
 599                 return PTR_ERR(p);
 600
 601         ret = -ENOMEM;
 602         clone = posix_acl_clone(p, GFP_NOFS);
 603         if (!clone)
 604                 goto err_release;
 605
 606         ret = posix_acl_create_masq(clone, mode);
 607         if (ret < 0)
 608                 goto err_release_clone;
 609
 610         if (ret == 0)
 611                 posix_acl_release(clone);
 612         else
 613                 *acl = clone;
 614
 615         if (!S_ISDIR(*mode))
 616                 posix_acl_release(p);
 617         else
 618                 *default_acl = p;
 619
 620         return 0;
 621
 622 err_release_clone:
 623         posix_acl_release(clone);
 624 err_release:
 625         posix_acl_release(p);
 626         return ret;
 627 }
 628 EXPORT_SYMBOL_GPL(posix_acl_create);
 629
 630 /**
 631  * posix_acl_update_mode  -  update mode in set_acl
 632  *
 633  * Update the file mode when setting an ACL: compute the new file permission
 634  * bits based on the ACL.  In addition, if the ACL is equivalent to the new
 635  * file mode, set *acl to NULL to indicate that no ACL should be set.
 636  *
 637  * As with chmod, clear the setgit bit if the caller is not in the owning group
 638  * or capable of CAP_FSETID (see inode_change_ok).
 639  *
 640  * Called from set_acl inode operations.
 641  */
 642 int posix_acl_update_mode(struct inode *inode, umode_t *mode_p,
 643                           struct posix_acl **acl)
 644 {
 645         umode_t mode = inode->i_mode;
 646         int error;
 647
 648         error = posix_acl_equiv_mode(*acl, &mode);
 649         if (error < 0)
 650                 return error;
 651         if (error == 0)
 652                 *acl = NULL;
 653         if (!in_group_p(inode->i_gid) &&
 654             !capable_wrt_inode_uidgid(inode, CAP_FSETID))
 655                 mode &= ~S_ISGID;
 656         *mode_p = mode;
 657         return 0;
 658 }
 659 EXPORT_SYMBOL(posix_acl_update_mode);
 660
 661 /*
 662  * Fix up the uids and gids in posix acl extended attributes in place.
 663  */
 664 static void posix_acl_fix_xattr_userns(
 665         struct user_namespace *to, struct user_namespace *from,
 666         void *value, size_t size)
 667 {
 668         struct posix_acl_xattr_header *header = value;
 669         struct posix_acl_xattr_entry *entry = (void *)(header + 1), *end;
 670         int count;
 671         kuid_t uid;
 672         kgid_t gid;
 673
 674         if (!value)
 675                 return;
 676         if (size < sizeof(struct posix_acl_xattr_header))
 677                 return;
 678         if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
 679                 return;
 680
 681         count = posix_acl_xattr_count(size);
 682         if (count < 0)
 683                 return;
 684         if (count == 0)
 685                 return;
 686
 687         for (end = entry + count; entry != end; entry++) {
 688                 switch(le16_to_cpu(entry->e_tag)) {
 689                 case ACL_USER:
 690                         uid = make_kuid(from, le32_to_cpu(entry->e_id));
 691                         entry->e_id = cpu_to_le32(from_kuid(to, uid));
 692                         break;
 693                 case ACL_GROUP:
 694                         gid = make_kgid(from, le32_to_cpu(entry->e_id));
 695                         entry->e_id = cpu_to_le32(from_kgid(to, gid));
 696                         break;
 697                 default:
 698                         break;
 699                 }
 700         }
 701 }
 702
 703 void posix_acl_fix_xattr_from_user(void *value, size_t size)
 704 {
 705         struct user_namespace *user_ns = current_user_ns();
 706         if (user_ns == &init_user_ns)
 707                 return;
 708         posix_acl_fix_xattr_userns(&init_user_ns, user_ns, value, size);
 709 }
 710
 711 void posix_acl_fix_xattr_to_user(void *value, size_t size)
 712 {
 713         struct user_namespace *user_ns = current_user_ns();
 714         if (user_ns == &init_user_ns)
 715                 return;
 716         posix_acl_fix_xattr_userns(user_ns, &init_user_ns, value, size);
 717 }
 718
 719 /*
 720  * Convert from extended attribute to in-memory representation.
 721  */
 722 struct posix_acl *
 723 posix_acl_from_xattr(struct user_namespace *user_ns,
 724                      const void *value, size_t size)
 725 {
 726         const struct posix_acl_xattr_header *header = value;
 727         const struct posix_acl_xattr_entry *entry = (const void *)(header + 1), *end;
 728         int count;
 729         struct posix_acl *acl;
 730         struct posix_acl_entry *acl_e;
 731
 732         if (!value)
 733                 return NULL;
 734         if (size < sizeof(struct posix_acl_xattr_header))
 735                  return ERR_PTR(-EINVAL);
 736         if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
 737                 return ERR_PTR(-EOPNOTSUPP);
 738
 739         count = posix_acl_xattr_count(size);
 740         if (count < 0)
 741                 return ERR_PTR(-EINVAL);
 742         if (count == 0)
 743                 return NULL;
 744
 745         acl = posix_acl_alloc(count, GFP_NOFS);
 746         if (!acl)
 747                 return ERR_PTR(-ENOMEM);
 748         acl_e = acl->a_entries;
 749
 750         for (end = entry + count; entry != end; acl_e++, entry++) {
 751                 acl_e->e_tag  = le16_to_cpu(entry->e_tag);
 752                 acl_e->e_perm = le16_to_cpu(entry->e_perm);
 753
 754                 switch(acl_e->e_tag) {
 755                         case ACL_USER_OBJ:
 756                         case ACL_GROUP_OBJ:
 757                         case ACL_MASK:
 758                         case ACL_OTHER:
 759                                 break;
 760
 761                         case ACL_USER:
 762                                 acl_e->e_uid =
 763                                         make_kuid(user_ns,
 764                                                   le32_to_cpu(entry->e_id));
 765                                 if (!uid_valid(acl_e->e_uid))
 766                                         goto fail;
 767                                 break;
 768                         case ACL_GROUP:
 769                                 acl_e->e_gid =
 770                                         make_kgid(user_ns,
 771                                                   le32_to_cpu(entry->e_id));
 772                                 if (!gid_valid(acl_e->e_gid))
 773                                         goto fail;
 774                                 break;
 775
 776                         default:
 777                                 goto fail;
 778                 }
 779         }
 780         return acl;
 781
 782 fail:
 783         posix_acl_release(acl);
 784         return ERR_PTR(-EINVAL);
 785 }
 786 EXPORT_SYMBOL (posix_acl_from_xattr);
 787
 788 /*
 789  * Convert from in-memory to extended attribute representation.
 790  */
 791 int
 792 posix_acl_to_xattr(struct user_namespace *user_ns, const struct posix_acl *acl,
 793                    void *buffer, size_t size)
 794 {
 795         struct posix_acl_xattr_header *ext_acl = buffer;
 796         struct posix_acl_xattr_entry *ext_entry;
 797         int real_size, n;
 798
 799         real_size = posix_acl_xattr_size(acl->a_count);
 800         if (!buffer)
 801                 return real_size;
 802         if (real_size > size)
 803                 return -ERANGE;
 804
 805         ext_entry = (void *)(ext_acl + 1);
 806         ext_acl->a_version = cpu_to_le32(POSIX_ACL_XATTR_VERSION);
 807
 808         for (n=0; n < acl->a_count; n++, ext_entry++) {
 809                 const struct posix_acl_entry *acl_e = &acl->a_entries[n];
 810                 ext_entry->e_tag  = cpu_to_le16(acl_e->e_tag);
 811                 ext_entry->e_perm = cpu_to_le16(acl_e->e_perm);
 812                 switch(acl_e->e_tag) {
 813                 case ACL_USER:
 814                         ext_entry->e_id =
 815                                 cpu_to_le32(from_kuid(user_ns, acl_e->e_uid));
 816                         break;
 817                 case ACL_GROUP:
 818                         ext_entry->e_id =
 819                                 cpu_to_le32(from_kgid(user_ns, acl_e->e_gid));
 820                         break;
 821                 default:
 822                         ext_entry->e_id = cpu_to_le32(ACL_UNDEFINED_ID);
 823                         break;
 824                 }
 825         }
 826         return real_size;
 827 }
 828 EXPORT_SYMBOL (posix_acl_to_xattr);
 829
 830 static int
 831 posix_acl_xattr_get(const struct xattr_handler *handler,
 832                     struct dentry *unused, struct inode *inode,
 833                     const char *name, void *value, size_t size)
 834 {
 835         struct posix_acl *acl;
 836         int error;
 837
 838         if (!IS_POSIXACL(inode))
 839                 return -EOPNOTSUPP;
 840         if (S_ISLNK(inode->i_mode))
 841                 return -EOPNOTSUPP;
 842
 843         acl = get_acl(inode, handler->flags);
 844         if (IS_ERR(acl))
 845                 return PTR_ERR(acl);
 846         if (acl == NULL)
 847                 return -ENODATA;
 848
 849         error = posix_acl_to_xattr(&init_user_ns, acl, value, size);
 850         posix_acl_release(acl);
 851
 852         return error;
 853 }
 854
 855 int
 856 set_posix_acl(struct inode *inode, int type, struct posix_acl *acl)
 857 {
 858         if (!IS_POSIXACL(inode))
 859                 return -EOPNOTSUPP;
 860         if (!inode->i_op->set_acl)
 861                 return -EOPNOTSUPP;
 862
 863         if (type == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode))
 864                 return acl ? -EACCES : 0;
 865         if (!inode_owner_or_capable(inode))
 866                 return -EPERM;
 867
 868         if (acl) {
 869                 int ret = posix_acl_valid(inode->i_sb->s_user_ns, acl);
 870                 if (ret)
 871                         return ret;
 872         }
 873         return inode->i_op->set_acl(inode, acl, type);
 874 }
 875 EXPORT_SYMBOL(set_posix_acl);
 876
 877 static int
 878 posix_acl_xattr_set(const struct xattr_handler *handler,
 879                     struct dentry *unused, struct inode *inode,
 880                     const char *name, const void *value,
 881                     size_t size, int flags)
 882 {
 883         struct posix_acl *acl = NULL;
 884         int ret;
 885
 886         if (value) {
 887                 acl = posix_acl_from_xattr(&init_user_ns, value, size);
 888                 if (IS_ERR(acl))
 889                         return PTR_ERR(acl);
 890         }
 891         ret = set_posix_acl(inode, handler->flags, acl);
 892         posix_acl_release(acl);
 893         return ret;
 894 }
 895
 896 static bool
 897 posix_acl_xattr_list(struct dentry *dentry)
 898 {
 899         return IS_POSIXACL(d_backing_inode(dentry));
 900 }
 901
 902 const struct xattr_handler posix_acl_access_xattr_handler = {
 903         .name = XATTR_NAME_POSIX_ACL_ACCESS,
 904         .flags = ACL_TYPE_ACCESS,
 905         .list = posix_acl_xattr_list,
 906         .get = posix_acl_xattr_get,
 907         .set = posix_acl_xattr_set,
 908 };
 909 EXPORT_SYMBOL_GPL(posix_acl_access_xattr_handler);
 910
 911 const struct xattr_handler posix_acl_default_xattr_handler = {
 912         .name = XATTR_NAME_POSIX_ACL_DEFAULT,
 913         .flags = ACL_TYPE_DEFAULT,
 914         .list = posix_acl_xattr_list,
 915         .get = posix_acl_xattr_get,
 916         .set = posix_acl_xattr_set,
 917 };
 918 EXPORT_SYMBOL_GPL(posix_acl_default_xattr_handler);
 919
 920 int simple_set_acl(struct inode *inode, struct posix_acl *acl, int type)
 921 {
 922         int error;
 923
 924         if (type == ACL_TYPE_ACCESS) {
 925                 error = posix_acl_equiv_mode(acl, &inode->i_mode);
 926                 if (error < 0)
 927                         return 0;
 928                 if (error == 0)
 929                         acl = NULL;
 930         }
 931
 932         inode->i_ctime = current_time(inode);
 933         set_cached_acl(inode, type, acl);
 934         return 0;
 935 }
 936
 937 int simple_acl_create(struct inode *dir, struct inode *inode)
 938 {
 939         struct posix_acl *default_acl, *acl;
 940         int error;
 941
 942         error = posix_acl_create(dir, &inode->i_mode, &default_acl, &acl);
 943         if (error)
 944                 return error;
 945
 946         set_cached_acl(inode, ACL_TYPE_DEFAULT, default_acl);
 947         set_cached_acl(inode, ACL_TYPE_ACCESS, acl);
 948
 949         if (default_acl)
 950                 posix_acl_release(default_acl);
 951         if (acl)
 952                 posix_acl_release(acl);
 953         return 0;
 954 }