fs/posix_acl.c

   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
  26 static struct posix_acl **acl_by_type(struct inode *inode, int type)
  27 {
  28         switch (type) {
  29         case ACL_TYPE_ACCESS:
  30                 return &inode->i_acl;
  31         case ACL_TYPE_DEFAULT:
  32                 return &inode->i_default_acl;
  33         default:
  34                 BUG();
  35         }
  36 }
  37
  38 struct posix_acl *get_cached_acl(struct inode *inode, int type)
  39 {
  40         struct posix_acl **p = acl_by_type(inode, type);
  41         struct posix_acl *acl;
  42
  43         for (;;) {
  44                 rcu_read_lock();
  45                 acl = rcu_dereference(*p);
  46                 if (!acl || is_uncached_acl(acl) ||
  47                     refcount_inc_not_zero(&acl->a_refcount))
  48                         break;
  49                 rcu_read_unlock();
  50                 cpu_relax();
  51         }
  52         rcu_read_unlock();
  53         return acl;
  54 }
  55 EXPORT_SYMBOL(get_cached_acl);
  56
  57 struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type)
  58 {
  59         return rcu_dereference(*acl_by_type(inode, type));
  60 }
  61 EXPORT_SYMBOL(get_cached_acl_rcu);
  62
  63 void set_cached_acl(struct inode *inode, int type, struct posix_acl *acl)
  64 {
  65         struct posix_acl **p = acl_by_type(inode, type);
  66         struct posix_acl *old;
  67
  68         old = xchg(p, posix_acl_dup(acl));
  69         if (!is_uncached_acl(old))
  70                 posix_acl_release(old);
  71 }
  72 EXPORT_SYMBOL(set_cached_acl);
  73
  74 static void __forget_cached_acl(struct posix_acl **p)
  75 {
  76         struct posix_acl *old;
  77
  78         old = xchg(p, ACL_NOT_CACHED);
  79         if (!is_uncached_acl(old))
  80                 posix_acl_release(old);
  81 }
  82
  83 void forget_cached_acl(struct inode *inode, int type)
  84 {
  85         __forget_cached_acl(acl_by_type(inode, type));
  86 }
  87 EXPORT_SYMBOL(forget_cached_acl);
  88
  89 void forget_all_cached_acls(struct inode *inode)
  90 {
  91         __forget_cached_acl(&inode->i_acl);
  92         __forget_cached_acl(&inode->i_default_acl);
  93 }
  94 EXPORT_SYMBOL(forget_all_cached_acls);
  95
  96 struct posix_acl *get_acl(struct inode *inode, int type)
  97 {
  98         void *sentinel;
  99         struct posix_acl **p;
 100         struct posix_acl *acl;
 101
 102         /*
 103          * The sentinel is used to detect when another operation like
 104          * set_cached_acl() or forget_cached_acl() races with get_acl().
 105          * It is guaranteed that is_uncached_acl(sentinel) is true.
 106          */
 107
 108         acl = get_cached_acl(inode, type);
 109         if (!is_uncached_acl(acl))
 110                 return acl;
 111
 112         if (!IS_POSIXACL(inode))
 113                 return NULL;
 114
 115         sentinel = uncached_acl_sentinel(current);
 116         p = acl_by_type(inode, type);
 117
 118         /*
 119          * If the ACL isn't being read yet, set our sentinel.  Otherwise, the
 120          * current value of the ACL will not be ACL_NOT_CACHED and so our own
 121          * sentinel will not be set; another task will update the cache.  We
 122          * could wait for that other task to complete its job, but it's easier
 123          * to just call ->get_acl to fetch the ACL ourself.  (This is going to
 124          * be an unlikely race.)
 125          */
 126         if (cmpxchg(p, ACL_NOT_CACHED, sentinel) != ACL_NOT_CACHED)
 127                 /* fall through */ ;
 128
 129         /*
 130          * Normally, the ACL returned by ->get_acl will be cached.
 131          * A filesystem can prevent that by calling
 132          * forget_cached_acl(inode, type) in ->get_acl.
 133          *
 134          * If the filesystem doesn't have a get_acl() function at all, we'll
 135          * just create the negative cache entry.
 136          */
 137         if (!inode->i_op->get_acl) {
 138                 set_cached_acl(inode, type, NULL);
 139                 return NULL;
 140         }
 141         acl = inode->i_op->get_acl(inode, type);
 142
 143         if (IS_ERR(acl)) {
 144                 /*
 145                  * Remove our sentinel so that we don't block future attempts
 146                  * to cache the ACL.
 147                  */
 148                 cmpxchg(p, sentinel, ACL_NOT_CACHED);
 149                 return acl;
 150         }
 151
 152         /*
 153          * Cache the result, but only if our sentinel is still in place.
 154          */
 155         posix_acl_dup(acl);
 156         if (unlikely(cmpxchg(p, sentinel, acl) != sentinel))
 157                 posix_acl_release(acl);
 158         return acl;
 159 }
 160 EXPORT_SYMBOL(get_acl);
 161
 162 /*
 163  * Init a fresh posix_acl
 164  */
 165 void
 166 posix_acl_init(struct posix_acl *acl, int count)
 167 {
 168         refcount_set(&acl->a_refcount, 1);
 169         acl->a_count = count;
 170 }
 171 EXPORT_SYMBOL(posix_acl_init);
 172
 173 /*
 174  * Allocate a new ACL with the specified number of entries.
 175  */
 176 struct posix_acl *
 177 posix_acl_alloc(int count, gfp_t flags)
 178 {
 179         const size_t size = sizeof(struct posix_acl) +
 180                             count * sizeof(struct posix_acl_entry);
 181         struct posix_acl *acl = kmalloc(size, flags);
 182         if (acl)
 183                 posix_acl_init(acl, count);
 184         return acl;
 185 }
 186 EXPORT_SYMBOL(posix_acl_alloc);
 187
 188 /*
 189  * Clone an ACL.
 190  */
 191 static struct posix_acl *
 192 posix_acl_clone(const struct posix_acl *acl, gfp_t flags)
 193 {
 194         struct posix_acl *clone = NULL;
 195
 196         if (acl) {
 197                 int size = sizeof(struct posix_acl) + acl->a_count *
 198                            sizeof(struct posix_acl_entry);
 199                 clone = kmemdup(acl, size, flags);
 200                 if (clone)
 201                         refcount_set(&clone->a_refcount, 1);
 202         }
 203         return clone;
 204 }
 205
 206 /*
 207  * Check if an acl is valid. Returns 0 if it is, or -E... otherwise.
 208  */
 209 int
 210 posix_acl_valid(struct user_namespace *user_ns, const struct posix_acl *acl)
 211 {
 212         const struct posix_acl_entry *pa, *pe;
 213         int state = ACL_USER_OBJ;
 214         int needs_mask = 0;
 215
 216         FOREACH_ACL_ENTRY(pa, acl, pe) {
 217                 if (pa->e_perm & ~(ACL_READ|ACL_WRITE|ACL_EXECUTE))
 218                         return -EINVAL;
 219                 switch (pa->e_tag) {
 220                         case ACL_USER_OBJ:
 221                                 if (state == ACL_USER_OBJ) {
 222                                         state = ACL_USER;
 223                                         break;
 224                                 }
 225                                 return -EINVAL;
 226
 227                         case ACL_USER:
 228                                 if (state != ACL_USER)
 229                                         return -EINVAL;
 230                                 if (!kuid_has_mapping(user_ns, pa->e_uid))
 231                                         return -EINVAL;
 232                                 needs_mask = 1;
 233                                 break;
 234
 235                         case ACL_GROUP_OBJ:
 236                                 if (state == ACL_USER) {
 237                                         state = ACL_GROUP;
 238                                         break;
 239                                 }
 240                                 return -EINVAL;
 241
 242                         case ACL_GROUP:
 243                                 if (state != ACL_GROUP)
 244                                         return -EINVAL;
 245                                 if (!kgid_has_mapping(user_ns, pa->e_gid))
 246                                         return -EINVAL;
 247                                 needs_mask = 1;
 248                                 break;
 249
 250                         case ACL_MASK:
 251                                 if (state != ACL_GROUP)
 252                                         return -EINVAL;
 253                                 state = ACL_OTHER;
 254                                 break;
 255
 256                         case ACL_OTHER:
 257                                 if (state == ACL_OTHER ||
 258                                     (state == ACL_GROUP && !needs_mask)) {
 259                                         state = 0;
 260                                         break;
 261                                 }
 262                                 return -EINVAL;
 263
 264                         default:
 265                                 return -EINVAL;
 266                 }
 267         }
 268         if (state == 0)
 269                 return 0;
 270         return -EINVAL;
 271 }
 272 EXPORT_SYMBOL(posix_acl_valid);
 273
 274 /*
 275  * Returns 0 if the acl can be exactly represented in the traditional
 276  * file mode permission bits, or else 1. Returns -E... on error.
 277  */
 278 int
 279 posix_acl_equiv_mode(const struct posix_acl *acl, umode_t *mode_p)
 280 {
 281         const struct posix_acl_entry *pa, *pe;
 282         umode_t mode = 0;
 283         int not_equiv = 0;
 284
 285         /*
 286          * A null ACL can always be presented as mode bits.
 287          */
 288         if (!acl)
 289                 return 0;
 290
 291         FOREACH_ACL_ENTRY(pa, acl, pe) {
 292                 switch (pa->e_tag) {
 293                         case ACL_USER_OBJ:
 294                                 mode |= (pa->e_perm & S_IRWXO) << 6;
 295                                 break;
 296                         case ACL_GROUP_OBJ:
 297                                 mode |= (pa->e_perm & S_IRWXO) << 3;
 298                                 break;
 299                         case ACL_OTHER:
 300                                 mode |= pa->e_perm & S_IRWXO;
 301                                 break;
 302                         case ACL_MASK:
 303                                 mode = (mode & ~S_IRWXG) |
 304                                        ((pa->e_perm & S_IRWXO) << 3);
 305                                 not_equiv = 1;
 306                                 break;
 307                         case ACL_USER:
 308                         case ACL_GROUP:
 309                                 not_equiv = 1;
 310                                 break;
 311                         default:
 312                                 return -EINVAL;
 313                 }
 314         }
 315         if (mode_p)
 316                 *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
 317         return not_equiv;
 318 }
 319 EXPORT_SYMBOL(posix_acl_equiv_mode);
 320
 321 /*
 322  * Create an ACL representing the file mode permission bits of an inode.
 323  */
 324 struct posix_acl *
 325 posix_acl_from_mode(umode_t mode, gfp_t flags)
 326 {
 327         struct posix_acl *acl = posix_acl_alloc(3, flags);
 328         if (!acl)
 329                 return ERR_PTR(-ENOMEM);
 330
 331         acl->a_entries[0].e_tag  = ACL_USER_OBJ;
 332         acl->a_entries[0].e_perm = (mode & S_IRWXU) >> 6;
 333
 334         acl->a_entries[1].e_tag  = ACL_GROUP_OBJ;
 335         acl->a_entries[1].e_perm = (mode & S_IRWXG) >> 3;
 336
 337         acl->a_entries[2].e_tag  = ACL_OTHER;
 338         acl->a_entries[2].e_perm = (mode & S_IRWXO);
 339         return acl;
 340 }
 341 EXPORT_SYMBOL(posix_acl_from_mode);
 342
 343 /*
 344  * Return 0 if current is granted want access to the inode
 345  * by the acl. Returns -E... otherwise.
 346  */
 347 int
 348 posix_acl_permission(struct user_namespace *mnt_userns, struct inode *inode,
 349                      const struct posix_acl *acl, int want)
 350 {
 351         const struct posix_acl_entry *pa, *pe, *mask_obj;
 352         int found = 0;
 353         kuid_t uid;
 354         kgid_t gid;
 355
 356         want &= MAY_READ | MAY_WRITE | MAY_EXEC;
 357
 358         FOREACH_ACL_ENTRY(pa, acl, pe) {
 359                 switch(pa->e_tag) {
 360                         case ACL_USER_OBJ:
 361                                 /* (May have been checked already) */
 362                                 uid = i_uid_into_mnt(mnt_userns, inode);
 363                                 if (uid_eq(uid, current_fsuid()))
 364                                         goto check_perm;
 365                                 break;
 366                         case ACL_USER:
 367                                 uid = kuid_into_mnt(mnt_userns, pa->e_uid);
 368                                 if (uid_eq(uid, current_fsuid()))
 369                                         goto mask;
 370                                 break;
 371                         case ACL_GROUP_OBJ:
 372                                 gid = i_gid_into_mnt(mnt_userns, inode);
 373                                 if (in_group_p(gid)) {
 374                                         found = 1;
 375                                         if ((pa->e_perm & want) == want)
 376                                                 goto mask;
 377                                 }
 378                                 break;
 379                         case ACL_GROUP:
 380                                 gid = kgid_into_mnt(mnt_userns, pa->e_gid);
 381                                 if (in_group_p(gid)) {
 382                                         found = 1;
 383                                         if ((pa->e_perm & want) == want)
 384                                                 goto mask;
 385                                 }
 386                                 break;
 387                         case ACL_MASK:
 388                                 break;
 389                         case ACL_OTHER:
 390                                 if (found)
 391                                         return -EACCES;
 392                                 else
 393                                         goto check_perm;
 394                         default:
 395                                 return -EIO;
 396                 }
 397         }
 398         return -EIO;
 399
 400 mask:
 401         for (mask_obj = pa+1; mask_obj != pe; mask_obj++) {
 402                 if (mask_obj->e_tag == ACL_MASK) {
 403                         if ((pa->e_perm & mask_obj->e_perm & want) == want)
 404                                 return 0;
 405                         return -EACCES;
 406                 }
 407         }
 408
 409 check_perm:
 410         if ((pa->e_perm & want) == want)
 411                 return 0;
 412         return -EACCES;
 413 }
 414
 415 /*
 416  * Modify acl when creating a new inode. The caller must ensure the acl is
 417  * only referenced once.
 418  *
 419  * mode_p initially must contain the mode parameter to the open() / creat()
 420  * system calls. All permissions that are not granted by the acl are removed.
 421  * The permissions in the acl are changed to reflect the mode_p parameter.
 422  */
 423 static int posix_acl_create_masq(struct posix_acl *acl, umode_t *mode_p)
 424 {
 425         struct posix_acl_entry *pa, *pe;
 426         struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
 427         umode_t mode = *mode_p;
 428         int not_equiv = 0;
 429
 430         /* assert(atomic_read(acl->a_refcount) == 1); */
 431
 432         FOREACH_ACL_ENTRY(pa, acl, pe) {
 433                 switch(pa->e_tag) {
 434                         case ACL_USER_OBJ:
 435                                 pa->e_perm &= (mode >> 6) | ~S_IRWXO;
 436                                 mode &= (pa->e_perm << 6) | ~S_IRWXU;
 437                                 break;
 438
 439                         case ACL_USER:
 440                         case ACL_GROUP:
 441                                 not_equiv = 1;
 442                                 break;
 443
 444                         case ACL_GROUP_OBJ:
 445                                 group_obj = pa;
 446                                 break;
 447
 448                         case ACL_OTHER:
 449                                 pa->e_perm &= mode | ~S_IRWXO;
 450                                 mode &= pa->e_perm | ~S_IRWXO;
 451                                 break;
 452
 453                         case ACL_MASK:
 454                                 mask_obj = pa;
 455                                 not_equiv = 1;
 456                                 break;
 457
 458                         default:
 459                                 return -EIO;
 460                 }
 461         }
 462
 463         if (mask_obj) {
 464                 mask_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
 465                 mode &= (mask_obj->e_perm << 3) | ~S_IRWXG;
 466         } else {
 467                 if (!group_obj)
 468                         return -EIO;
 469                 group_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
 470                 mode &= (group_obj->e_perm << 3) | ~S_IRWXG;
 471         }
 472
 473         *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
 474         return not_equiv;
 475 }
 476
 477 /*
 478  * Modify the ACL for the chmod syscall.
 479  */
 480 static int __posix_acl_chmod_masq(struct posix_acl *acl, umode_t mode)
 481 {
 482         struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
 483         struct posix_acl_entry *pa, *pe;
 484
 485         /* assert(atomic_read(acl->a_refcount) == 1); */
 486
 487         FOREACH_ACL_ENTRY(pa, acl, pe) {
 488                 switch(pa->e_tag) {
 489                         case ACL_USER_OBJ:
 490                                 pa->e_perm = (mode & S_IRWXU) >> 6;
 491                                 break;
 492
 493                         case ACL_USER:
 494                         case ACL_GROUP:
 495                                 break;
 496
 497                         case ACL_GROUP_OBJ:
 498                                 group_obj = pa;
 499                                 break;
 500
 501                         case ACL_MASK:
 502                                 mask_obj = pa;
 503                                 break;
 504
 505                         case ACL_OTHER:
 506                                 pa->e_perm = (mode & S_IRWXO);
 507                                 break;
 508
 509                         default:
 510                                 return -EIO;
 511                 }
 512         }
 513
 514         if (mask_obj) {
 515                 mask_obj->e_perm = (mode & S_IRWXG) >> 3;
 516         } else {
 517                 if (!group_obj)
 518                         return -EIO;
 519                 group_obj->e_perm = (mode & S_IRWXG) >> 3;
 520         }
 521
 522         return 0;
 523 }
 524
 525 int
 526 __posix_acl_create(struct posix_acl **acl, gfp_t gfp, umode_t *mode_p)
 527 {
 528         struct posix_acl *clone = posix_acl_clone(*acl, gfp);
 529         int err = -ENOMEM;
 530         if (clone) {
 531                 err = posix_acl_create_masq(clone, mode_p);
 532                 if (err < 0) {
 533                         posix_acl_release(clone);
 534                         clone = NULL;
 535                 }
 536         }
 537         posix_acl_release(*acl);
 538         *acl = clone;
 539         return err;
 540 }
 541 EXPORT_SYMBOL(__posix_acl_create);
 542
 543 int
 544 __posix_acl_chmod(struct posix_acl **acl, gfp_t gfp, umode_t mode)
 545 {
 546         struct posix_acl *clone = posix_acl_clone(*acl, gfp);
 547         int err = -ENOMEM;
 548         if (clone) {
 549                 err = __posix_acl_chmod_masq(clone, mode);
 550                 if (err) {
 551                         posix_acl_release(clone);
 552                         clone = NULL;
 553                 }
 554         }
 555         posix_acl_release(*acl);
 556         *acl = clone;
 557         return err;
 558 }
 559 EXPORT_SYMBOL(__posix_acl_chmod);
 560
 561 /**
 562  * posix_acl_chmod - chmod a posix acl
 563  *
 564  * @mnt_userns: user namespace of the mount @inode was found from
 565  * @inode:      inode to check permissions on
 566  * @mode:       the new mode of @inode
 567  *
 568  * If the inode has been found through an idmapped mount the user namespace of
 569  * the vfsmount must be passed through @mnt_userns. This function will then
 570  * take care to map the inode according to @mnt_userns before checking
 571  * permissions. On non-idmapped mounts or if permission checking is to be
 572  * performed on the raw inode simply passs init_user_ns.
 573  */
 574 int
 575  posix_acl_chmod(struct user_namespace *mnt_userns, struct inode *inode,
 576                     umode_t mode)
 577 {
 578         struct posix_acl *acl;
 579         int ret = 0;
 580
 581         if (!IS_POSIXACL(inode))
 582                 return 0;
 583         if (!inode->i_op->set_acl)
 584                 return -EOPNOTSUPP;
 585
 586         acl = get_acl(inode, ACL_TYPE_ACCESS);
 587         if (IS_ERR_OR_NULL(acl)) {
 588                 if (acl == ERR_PTR(-EOPNOTSUPP))
 589                         return 0;
 590                 return PTR_ERR(acl);
 591         }
 592
 593         ret = __posix_acl_chmod(&acl, GFP_KERNEL, mode);
 594         if (ret)
 595                 return ret;
 596         ret = inode->i_op->set_acl(inode, acl, ACL_TYPE_ACCESS);
 597         posix_acl_release(acl);
 598         return ret;
 599 }
 600 EXPORT_SYMBOL(posix_acl_chmod);
 601
 602 int
 603 posix_acl_create(struct inode *dir, umode_t *mode,
 604                 struct posix_acl **default_acl, struct posix_acl **acl)
 605 {
 606         struct posix_acl *p;
 607         struct posix_acl *clone;
 608         int ret;
 609
 610         *acl = NULL;
 611         *default_acl = NULL;
 612
 613         if (S_ISLNK(*mode) || !IS_POSIXACL(dir))
 614                 return 0;
 615
 616         p = get_acl(dir, ACL_TYPE_DEFAULT);
 617         if (!p || p == ERR_PTR(-EOPNOTSUPP)) {
 618                 *mode &= ~current_umask();
 619                 return 0;
 620         }
 621         if (IS_ERR(p))
 622                 return PTR_ERR(p);
 623
 624         ret = -ENOMEM;
 625         clone = posix_acl_clone(p, GFP_NOFS);
 626         if (!clone)
 627                 goto err_release;
 628
 629         ret = posix_acl_create_masq(clone, mode);
 630         if (ret < 0)
 631                 goto err_release_clone;
 632
 633         if (ret == 0)
 634                 posix_acl_release(clone);
 635         else
 636                 *acl = clone;
 637
 638         if (!S_ISDIR(*mode))
 639                 posix_acl_release(p);
 640         else
 641                 *default_acl = p;
 642
 643         return 0;
 644
 645 err_release_clone:
 646         posix_acl_release(clone);
 647 err_release:
 648         posix_acl_release(p);
 649         return ret;
 650 }
 651 EXPORT_SYMBOL_GPL(posix_acl_create);
 652
 653 /**
 654  * posix_acl_update_mode  -  update mode in set_acl
 655  * @mnt_userns: user namespace of the mount @inode was found from
 656  * @inode:      target inode
 657  * @mode_p:     mode (pointer) for update
 658  * @acl:        acl pointer
 659  *
 660  * Update the file mode when setting an ACL: compute the new file permission
 661  * bits based on the ACL.  In addition, if the ACL is equivalent to the new
 662  * file mode, set *@acl to NULL to indicate that no ACL should be set.
 663  *
 664  * As with chmod, clear the setgid bit if the caller is not in the owning group
 665  * or capable of CAP_FSETID (see inode_change_ok).
 666  *
 667  * If the inode has been found through an idmapped mount the user namespace of
 668  * the vfsmount must be passed through @mnt_userns. This function will then
 669  * take care to map the inode according to @mnt_userns before checking
 670  * permissions. On non-idmapped mounts or if permission checking is to be
 671  * performed on the raw inode simply passs init_user_ns.
 672  *
 673  * Called from set_acl inode operations.
 674  */
 675 int posix_acl_update_mode(struct user_namespace *mnt_userns,
 676                           struct inode *inode, umode_t *mode_p,
 677                           struct posix_acl **acl)
 678 {
 679         umode_t mode = inode->i_mode;
 680         int error;
 681
 682         error = posix_acl_equiv_mode(*acl, &mode);
 683         if (error < 0)
 684                 return error;
 685         if (error == 0)
 686                 *acl = NULL;
 687         if (!in_group_p(i_gid_into_mnt(mnt_userns, inode)) &&
 688             !capable_wrt_inode_uidgid(mnt_userns, inode, CAP_FSETID))
 689                 mode &= ~S_ISGID;
 690         *mode_p = mode;
 691         return 0;
 692 }
 693 EXPORT_SYMBOL(posix_acl_update_mode);
 694
 695 /*
 696  * Fix up the uids and gids in posix acl extended attributes in place.
 697  */
 698 static void posix_acl_fix_xattr_userns(
 699         struct user_namespace *to, struct user_namespace *from,
 700         struct user_namespace *mnt_userns,
 701         void *value, size_t size, bool from_user)
 702 {
 703         struct posix_acl_xattr_header *header = value;
 704         struct posix_acl_xattr_entry *entry = (void *)(header + 1), *end;
 705         int count;
 706         kuid_t uid;
 707         kgid_t gid;
 708
 709         if (!value)
 710                 return;
 711         if (size < sizeof(struct posix_acl_xattr_header))
 712                 return;
 713         if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
 714                 return;
 715
 716         count = posix_acl_xattr_count(size);
 717         if (count < 0)
 718                 return;
 719         if (count == 0)
 720                 return;
 721
 722         for (end = entry + count; entry != end; entry++) {
 723                 switch(le16_to_cpu(entry->e_tag)) {
 724                 case ACL_USER:
 725                         uid = make_kuid(from, le32_to_cpu(entry->e_id));
 726                         if (from_user)
 727                                 uid = kuid_from_mnt(mnt_userns, uid);
 728                         else
 729                                 uid = kuid_into_mnt(mnt_userns, uid);
 730                         entry->e_id = cpu_to_le32(from_kuid(to, uid));
 731                         break;
 732                 case ACL_GROUP:
 733                         gid = make_kgid(from, le32_to_cpu(entry->e_id));
 734                         if (from_user)
 735                                 gid = kgid_from_mnt(mnt_userns, gid);
 736                         else
 737                                 gid = kgid_into_mnt(mnt_userns, gid);
 738                         entry->e_id = cpu_to_le32(from_kgid(to, gid));
 739                         break;
 740                 default:
 741                         break;
 742                 }
 743         }
 744 }
 745
 746 void posix_acl_fix_xattr_from_user(struct user_namespace *mnt_userns,
 747                                    void *value, size_t size)
 748 {
 749         struct user_namespace *user_ns = current_user_ns();
 750         if ((user_ns == &init_user_ns) && (mnt_userns == &init_user_ns))
 751                 return;
 752         posix_acl_fix_xattr_userns(&init_user_ns, user_ns, mnt_userns, value,
 753                                    size, true);
 754 }
 755
 756 void posix_acl_fix_xattr_to_user(struct user_namespace *mnt_userns,
 757                                  void *value, size_t size)
 758 {
 759         struct user_namespace *user_ns = current_user_ns();
 760         if ((user_ns == &init_user_ns) && (mnt_userns == &init_user_ns))
 761                 return;
 762         posix_acl_fix_xattr_userns(user_ns, &init_user_ns, mnt_userns, value,
 763                                    size, false);
 764 }
 765
 766 /*
 767  * Convert from extended attribute to in-memory representation.
 768  */
 769 struct posix_acl *
 770 posix_acl_from_xattr(struct user_namespace *user_ns,
 771                      const void *value, size_t size)
 772 {
 773         const struct posix_acl_xattr_header *header = value;
 774         const struct posix_acl_xattr_entry *entry = (const void *)(header + 1), *end;
 775         int count;
 776         struct posix_acl *acl;
 777         struct posix_acl_entry *acl_e;
 778
 779         if (!value)
 780                 return NULL;
 781         if (size < sizeof(struct posix_acl_xattr_header))
 782                  return ERR_PTR(-EINVAL);
 783         if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
 784                 return ERR_PTR(-EOPNOTSUPP);
 785
 786         count = posix_acl_xattr_count(size);
 787         if (count < 0)
 788                 return ERR_PTR(-EINVAL);
 789         if (count == 0)
 790                 return NULL;
 791
 792         acl = posix_acl_alloc(count, GFP_NOFS);
 793         if (!acl)
 794                 return ERR_PTR(-ENOMEM);
 795         acl_e = acl->a_entries;
 796
 797         for (end = entry + count; entry != end; acl_e++, entry++) {
 798                 acl_e->e_tag  = le16_to_cpu(entry->e_tag);
 799                 acl_e->e_perm = le16_to_cpu(entry->e_perm);
 800
 801                 switch(acl_e->e_tag) {
 802                         case ACL_USER_OBJ:
 803                         case ACL_GROUP_OBJ:
 804                         case ACL_MASK:
 805                         case ACL_OTHER:
 806                                 break;
 807
 808                         case ACL_USER:
 809                                 acl_e->e_uid =
 810                                         make_kuid(user_ns,
 811                                                   le32_to_cpu(entry->e_id));
 812                                 if (!uid_valid(acl_e->e_uid))
 813                                         goto fail;
 814                                 break;
 815                         case ACL_GROUP:
 816                                 acl_e->e_gid =
 817                                         make_kgid(user_ns,
 818                                                   le32_to_cpu(entry->e_id));
 819                                 if (!gid_valid(acl_e->e_gid))
 820                                         goto fail;
 821                                 break;
 822
 823                         default:
 824                                 goto fail;
 825                 }
 826         }
 827         return acl;
 828
 829 fail:
 830         posix_acl_release(acl);
 831         return ERR_PTR(-EINVAL);
 832 }
 833 EXPORT_SYMBOL (posix_acl_from_xattr);
 834
 835 /*
 836  * Convert from in-memory to extended attribute representation.
 837  */
 838 int
 839 posix_acl_to_xattr(struct user_namespace *user_ns, const struct posix_acl *acl,
 840                    void *buffer, size_t size)
 841 {
 842         struct posix_acl_xattr_header *ext_acl = buffer;
 843         struct posix_acl_xattr_entry *ext_entry;
 844         int real_size, n;
 845
 846         real_size = posix_acl_xattr_size(acl->a_count);
 847         if (!buffer)
 848                 return real_size;
 849         if (real_size > size)
 850                 return -ERANGE;
 851
 852         ext_entry = (void *)(ext_acl + 1);
 853         ext_acl->a_version = cpu_to_le32(POSIX_ACL_XATTR_VERSION);
 854
 855         for (n=0; n < acl->a_count; n++, ext_entry++) {
 856                 const struct posix_acl_entry *acl_e = &acl->a_entries[n];
 857                 ext_entry->e_tag  = cpu_to_le16(acl_e->e_tag);
 858                 ext_entry->e_perm = cpu_to_le16(acl_e->e_perm);
 859                 switch(acl_e->e_tag) {
 860                 case ACL_USER:
 861                         ext_entry->e_id =
 862                                 cpu_to_le32(from_kuid(user_ns, acl_e->e_uid));
 863                         break;
 864                 case ACL_GROUP:
 865                         ext_entry->e_id =
 866                                 cpu_to_le32(from_kgid(user_ns, acl_e->e_gid));
 867                         break;
 868                 default:
 869                         ext_entry->e_id = cpu_to_le32(ACL_UNDEFINED_ID);
 870                         break;
 871                 }
 872         }
 873         return real_size;
 874 }
 875 EXPORT_SYMBOL (posix_acl_to_xattr);
 876
 877 static int
 878 posix_acl_xattr_get(const struct xattr_handler *handler,
 879                     struct dentry *unused, struct inode *inode,
 880                     const char *name, void *value, size_t size)
 881 {
 882         struct posix_acl *acl;
 883         int error;
 884
 885         if (!IS_POSIXACL(inode))
 886                 return -EOPNOTSUPP;
 887         if (S_ISLNK(inode->i_mode))
 888                 return -EOPNOTSUPP;
 889
 890         acl = get_acl(inode, handler->flags);
 891         if (IS_ERR(acl))
 892                 return PTR_ERR(acl);
 893         if (acl == NULL)
 894                 return -ENODATA;
 895
 896         error = posix_acl_to_xattr(&init_user_ns, acl, value, size);
 897         posix_acl_release(acl);
 898
 899         return error;
 900 }
 901
 902 int
 903 set_posix_acl(struct user_namespace *mnt_userns, struct inode *inode,
 904               int type, struct posix_acl *acl)
 905 {
 906         if (!IS_POSIXACL(inode))
 907                 return -EOPNOTSUPP;
 908         if (!inode->i_op->set_acl)
 909                 return -EOPNOTSUPP;
 910
 911         if (type == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode))
 912                 return acl ? -EACCES : 0;
 913         if (!inode_owner_or_capable(mnt_userns, inode))
 914                 return -EPERM;
 915
 916         if (acl) {
 917                 int ret = posix_acl_valid(inode->i_sb->s_user_ns, acl);
 918                 if (ret)
 919                         return ret;
 920         }
 921         return inode->i_op->set_acl(inode, acl, type);
 922 }
 923 EXPORT_SYMBOL(set_posix_acl);
 924
 925 static int
 926 posix_acl_xattr_set(const struct xattr_handler *handler,
 927                            struct user_namespace *mnt_userns,
 928                            struct dentry *unused, struct inode *inode,
 929                            const char *name, const void *value, size_t size,
 930                            int flags)
 931 {
 932         struct posix_acl *acl = NULL;
 933         int ret;
 934
 935         if (value) {
 936                 acl = posix_acl_from_xattr(&init_user_ns, value, size);
 937                 if (IS_ERR(acl))
 938                         return PTR_ERR(acl);
 939         }
 940         ret = set_posix_acl(mnt_userns, inode, handler->flags, acl);
 941         posix_acl_release(acl);
 942         return ret;
 943 }
 944
 945 static bool
 946 posix_acl_xattr_list(struct dentry *dentry)
 947 {
 948         return IS_POSIXACL(d_backing_inode(dentry));
 949 }
 950
 951 const struct xattr_handler posix_acl_access_xattr_handler = {
 952         .name = XATTR_NAME_POSIX_ACL_ACCESS,
 953         .flags = ACL_TYPE_ACCESS,
 954         .list = posix_acl_xattr_list,
 955         .get = posix_acl_xattr_get,
 956         .set = posix_acl_xattr_set,
 957 };
 958 EXPORT_SYMBOL_GPL(posix_acl_access_xattr_handler);
 959
 960 const struct xattr_handler posix_acl_default_xattr_handler = {
 961         .name = XATTR_NAME_POSIX_ACL_DEFAULT,
 962         .flags = ACL_TYPE_DEFAULT,
 963         .list = posix_acl_xattr_list,
 964         .get = posix_acl_xattr_get,
 965         .set = posix_acl_xattr_set,
 966 };
 967 EXPORT_SYMBOL_GPL(posix_acl_default_xattr_handler);
 968
 969 int simple_set_acl(struct inode *inode, struct posix_acl *acl, int type)
 970 {
 971         int error;
 972
 973         if (type == ACL_TYPE_ACCESS) {
 974                 error = posix_acl_update_mode(&init_user_ns, inode,
 975                                 &inode->i_mode, &acl);
 976                 if (error)
 977                         return error;
 978         }
 979
 980         inode->i_ctime = current_time(inode);
 981         set_cached_acl(inode, type, acl);
 982         return 0;
 983 }
 984
 985 int simple_acl_create(struct inode *dir, struct inode *inode)
 986 {
 987         struct posix_acl *default_acl, *acl;
 988         int error;
 989
 990         error = posix_acl_create(dir, &inode->i_mode, &default_acl, &acl);
 991         if (error)
 992                 return error;
 993
 994         set_cached_acl(inode, ACL_TYPE_DEFAULT, default_acl);
 995         set_cached_acl(inode, ACL_TYPE_ACCESS, acl);
 996
 997         if (default_acl)
 998                 posix_acl_release(default_acl);
 999         if (acl)
1000                 posix_acl_release(acl);
1001         return 0;
1002 }