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 #include <linux/namei.h>
  26 #include <linux/mnt_idmapping.h>
  27
  28 static struct posix_acl **acl_by_type(struct inode *inode, int type)
  29 {
  30         switch (type) {
  31         case ACL_TYPE_ACCESS:
  32                 return &inode->i_acl;
  33         case ACL_TYPE_DEFAULT:
  34                 return &inode->i_default_acl;
  35         default:
  36                 BUG();
  37         }
  38 }
  39
  40 struct posix_acl *get_cached_acl(struct inode *inode, int type)
  41 {
  42         struct posix_acl **p = acl_by_type(inode, type);
  43         struct posix_acl *acl;
  44
  45         for (;;) {
  46                 rcu_read_lock();
  47                 acl = rcu_dereference(*p);
  48                 if (!acl || is_uncached_acl(acl) ||
  49                     refcount_inc_not_zero(&acl->a_refcount))
  50                         break;
  51                 rcu_read_unlock();
  52                 cpu_relax();
  53         }
  54         rcu_read_unlock();
  55         return acl;
  56 }
  57 EXPORT_SYMBOL(get_cached_acl);
  58
  59 struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type)
  60 {
  61         struct posix_acl *acl = rcu_dereference(*acl_by_type(inode, type));
  62
  63         if (acl == ACL_DONT_CACHE) {
  64                 struct posix_acl *ret;
  65
  66                 ret = inode->i_op->get_acl(inode, type, LOOKUP_RCU);
  67                 if (!IS_ERR(ret))
  68                         acl = ret;
  69         }
  70
  71         return acl;
  72 }
  73 EXPORT_SYMBOL(get_cached_acl_rcu);
  74
  75 void set_cached_acl(struct inode *inode, int type, struct posix_acl *acl)
  76 {
  77         struct posix_acl **p = acl_by_type(inode, type);
  78         struct posix_acl *old;
  79
  80         old = xchg(p, posix_acl_dup(acl));
  81         if (!is_uncached_acl(old))
  82                 posix_acl_release(old);
  83 }
  84 EXPORT_SYMBOL(set_cached_acl);
  85
  86 static void __forget_cached_acl(struct posix_acl **p)
  87 {
  88         struct posix_acl *old;
  89
  90         old = xchg(p, ACL_NOT_CACHED);
  91         if (!is_uncached_acl(old))
  92                 posix_acl_release(old);
  93 }
  94
  95 void forget_cached_acl(struct inode *inode, int type)
  96 {
  97         __forget_cached_acl(acl_by_type(inode, type));
  98 }
  99 EXPORT_SYMBOL(forget_cached_acl);
 100
 101 void forget_all_cached_acls(struct inode *inode)
 102 {
 103         __forget_cached_acl(&inode->i_acl);
 104         __forget_cached_acl(&inode->i_default_acl);
 105 }
 106 EXPORT_SYMBOL(forget_all_cached_acls);
 107
 108 struct posix_acl *get_acl(struct inode *inode, int type)
 109 {
 110         void *sentinel;
 111         struct posix_acl **p;
 112         struct posix_acl *acl;
 113
 114         /*
 115          * The sentinel is used to detect when another operation like
 116          * set_cached_acl() or forget_cached_acl() races with get_acl().
 117          * It is guaranteed that is_uncached_acl(sentinel) is true.
 118          */
 119
 120         acl = get_cached_acl(inode, type);
 121         if (!is_uncached_acl(acl))
 122                 return acl;
 123
 124         if (!IS_POSIXACL(inode))
 125                 return NULL;
 126
 127         sentinel = uncached_acl_sentinel(current);
 128         p = acl_by_type(inode, type);
 129
 130         /*
 131          * If the ACL isn't being read yet, set our sentinel.  Otherwise, the
 132          * current value of the ACL will not be ACL_NOT_CACHED and so our own
 133          * sentinel will not be set; another task will update the cache.  We
 134          * could wait for that other task to complete its job, but it's easier
 135          * to just call ->get_acl to fetch the ACL ourself.  (This is going to
 136          * be an unlikely race.)
 137          */
 138         cmpxchg(p, ACL_NOT_CACHED, sentinel);
 139
 140         /*
 141          * Normally, the ACL returned by ->get_acl will be cached.
 142          * A filesystem can prevent that by calling
 143          * forget_cached_acl(inode, type) in ->get_acl.
 144          *
 145          * If the filesystem doesn't have a get_acl() function at all, we'll
 146          * just create the negative cache entry.
 147          */
 148         if (!inode->i_op->get_acl) {
 149                 set_cached_acl(inode, type, NULL);
 150                 return NULL;
 151         }
 152         acl = inode->i_op->get_acl(inode, type, false);
 153
 154         if (IS_ERR(acl)) {
 155                 /*
 156                  * Remove our sentinel so that we don't block future attempts
 157                  * to cache the ACL.
 158                  */
 159                 cmpxchg(p, sentinel, ACL_NOT_CACHED);
 160                 return acl;
 161         }
 162
 163         /*
 164          * Cache the result, but only if our sentinel is still in place.
 165          */
 166         posix_acl_dup(acl);
 167         if (unlikely(cmpxchg(p, sentinel, acl) != sentinel))
 168                 posix_acl_release(acl);
 169         return acl;
 170 }
 171 EXPORT_SYMBOL(get_acl);
 172
 173 /*
 174  * Init a fresh posix_acl
 175  */
 176 void
 177 posix_acl_init(struct posix_acl *acl, int count)
 178 {
 179         refcount_set(&acl->a_refcount, 1);
 180         acl->a_count = count;
 181 }
 182 EXPORT_SYMBOL(posix_acl_init);
 183
 184 /*
 185  * Allocate a new ACL with the specified number of entries.
 186  */
 187 struct posix_acl *
 188 posix_acl_alloc(int count, gfp_t flags)
 189 {
 190         const size_t size = sizeof(struct posix_acl) +
 191                             count * sizeof(struct posix_acl_entry);
 192         struct posix_acl *acl = kmalloc(size, flags);
 193         if (acl)
 194                 posix_acl_init(acl, count);
 195         return acl;
 196 }
 197 EXPORT_SYMBOL(posix_acl_alloc);
 198
 199 /*
 200  * Clone an ACL.
 201  */
 202 static struct posix_acl *
 203 posix_acl_clone(const struct posix_acl *acl, gfp_t flags)
 204 {
 205         struct posix_acl *clone = NULL;
 206
 207         if (acl) {
 208                 int size = sizeof(struct posix_acl) + acl->a_count *
 209                            sizeof(struct posix_acl_entry);
 210                 clone = kmemdup(acl, size, flags);
 211                 if (clone)
 212                         refcount_set(&clone->a_refcount, 1);
 213         }
 214         return clone;
 215 }
 216
 217 /*
 218  * Check if an acl is valid. Returns 0 if it is, or -E... otherwise.
 219  */
 220 int
 221 posix_acl_valid(struct user_namespace *user_ns, const struct posix_acl *acl)
 222 {
 223         const struct posix_acl_entry *pa, *pe;
 224         int state = ACL_USER_OBJ;
 225         int needs_mask = 0;
 226
 227         FOREACH_ACL_ENTRY(pa, acl, pe) {
 228                 if (pa->e_perm & ~(ACL_READ|ACL_WRITE|ACL_EXECUTE))
 229                         return -EINVAL;
 230                 switch (pa->e_tag) {
 231                         case ACL_USER_OBJ:
 232                                 if (state == ACL_USER_OBJ) {
 233                                         state = ACL_USER;
 234                                         break;
 235                                 }
 236                                 return -EINVAL;
 237
 238                         case ACL_USER:
 239                                 if (state != ACL_USER)
 240                                         return -EINVAL;
 241                                 if (!kuid_has_mapping(user_ns, pa->e_uid))
 242                                         return -EINVAL;
 243                                 needs_mask = 1;
 244                                 break;
 245
 246                         case ACL_GROUP_OBJ:
 247                                 if (state == ACL_USER) {
 248                                         state = ACL_GROUP;
 249                                         break;
 250                                 }
 251                                 return -EINVAL;
 252
 253                         case ACL_GROUP:
 254                                 if (state != ACL_GROUP)
 255                                         return -EINVAL;
 256                                 if (!kgid_has_mapping(user_ns, pa->e_gid))
 257                                         return -EINVAL;
 258                                 needs_mask = 1;
 259                                 break;
 260
 261                         case ACL_MASK:
 262                                 if (state != ACL_GROUP)
 263                                         return -EINVAL;
 264                                 state = ACL_OTHER;
 265                                 break;
 266
 267                         case ACL_OTHER:
 268                                 if (state == ACL_OTHER ||
 269                                     (state == ACL_GROUP && !needs_mask)) {
 270                                         state = 0;
 271                                         break;
 272                                 }
 273                                 return -EINVAL;
 274
 275                         default:
 276                                 return -EINVAL;
 277                 }
 278         }
 279         if (state == 0)
 280                 return 0;
 281         return -EINVAL;
 282 }
 283 EXPORT_SYMBOL(posix_acl_valid);
 284
 285 /*
 286  * Returns 0 if the acl can be exactly represented in the traditional
 287  * file mode permission bits, or else 1. Returns -E... on error.
 288  */
 289 int
 290 posix_acl_equiv_mode(const struct posix_acl *acl, umode_t *mode_p)
 291 {
 292         const struct posix_acl_entry *pa, *pe;
 293         umode_t mode = 0;
 294         int not_equiv = 0;
 295
 296         /*
 297          * A null ACL can always be presented as mode bits.
 298          */
 299         if (!acl)
 300                 return 0;
 301
 302         FOREACH_ACL_ENTRY(pa, acl, pe) {
 303                 switch (pa->e_tag) {
 304                         case ACL_USER_OBJ:
 305                                 mode |= (pa->e_perm & S_IRWXO) << 6;
 306                                 break;
 307                         case ACL_GROUP_OBJ:
 308                                 mode |= (pa->e_perm & S_IRWXO) << 3;
 309                                 break;
 310                         case ACL_OTHER:
 311                                 mode |= pa->e_perm & S_IRWXO;
 312                                 break;
 313                         case ACL_MASK:
 314                                 mode = (mode & ~S_IRWXG) |
 315                                        ((pa->e_perm & S_IRWXO) << 3);
 316                                 not_equiv = 1;
 317                                 break;
 318                         case ACL_USER:
 319                         case ACL_GROUP:
 320                                 not_equiv = 1;
 321                                 break;
 322                         default:
 323                                 return -EINVAL;
 324                 }
 325         }
 326         if (mode_p)
 327                 *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
 328         return not_equiv;
 329 }
 330 EXPORT_SYMBOL(posix_acl_equiv_mode);
 331
 332 /*
 333  * Create an ACL representing the file mode permission bits of an inode.
 334  */
 335 struct posix_acl *
 336 posix_acl_from_mode(umode_t mode, gfp_t flags)
 337 {
 338         struct posix_acl *acl = posix_acl_alloc(3, flags);
 339         if (!acl)
 340                 return ERR_PTR(-ENOMEM);
 341
 342         acl->a_entries[0].e_tag  = ACL_USER_OBJ;
 343         acl->a_entries[0].e_perm = (mode & S_IRWXU) >> 6;
 344
 345         acl->a_entries[1].e_tag  = ACL_GROUP_OBJ;
 346         acl->a_entries[1].e_perm = (mode & S_IRWXG) >> 3;
 347
 348         acl->a_entries[2].e_tag  = ACL_OTHER;
 349         acl->a_entries[2].e_perm = (mode & S_IRWXO);
 350         return acl;
 351 }
 352 EXPORT_SYMBOL(posix_acl_from_mode);
 353
 354 /*
 355  * Return 0 if current is granted want access to the inode
 356  * by the acl. Returns -E... otherwise.
 357  */
 358 int
 359 posix_acl_permission(struct user_namespace *mnt_userns, struct inode *inode,
 360                      const struct posix_acl *acl, int want)
 361 {
 362         const struct posix_acl_entry *pa, *pe, *mask_obj;
 363         int found = 0;
 364         kuid_t uid;
 365         kgid_t gid;
 366
 367         want &= MAY_READ | MAY_WRITE | MAY_EXEC;
 368
 369         FOREACH_ACL_ENTRY(pa, acl, pe) {
 370                 switch(pa->e_tag) {
 371                         case ACL_USER_OBJ:
 372                                 /* (May have been checked already) */
 373                                 uid = i_uid_into_mnt(mnt_userns, inode);
 374                                 if (uid_eq(uid, current_fsuid()))
 375                                         goto check_perm;
 376                                 break;
 377                         case ACL_USER:
 378                                 uid = mapped_kuid_fs(mnt_userns,
 379                                                      i_user_ns(inode),
 380                                                      pa->e_uid);
 381                                 if (uid_eq(uid, current_fsuid()))
 382                                         goto mask;
 383                                 break;
 384                         case ACL_GROUP_OBJ:
 385                                 gid = i_gid_into_mnt(mnt_userns, inode);
 386                                 if (in_group_p(gid)) {
 387                                         found = 1;
 388                                         if ((pa->e_perm & want) == want)
 389                                                 goto mask;
 390                                 }
 391                                 break;
 392                         case ACL_GROUP:
 393                                 gid = mapped_kgid_fs(mnt_userns,
 394                                                      i_user_ns(inode),
 395                                                      pa->e_gid);
 396                                 if (in_group_p(gid)) {
 397                                         found = 1;
 398                                         if ((pa->e_perm & want) == want)
 399                                                 goto mask;
 400                                 }
 401                                 break;
 402                         case ACL_MASK:
 403                                 break;
 404                         case ACL_OTHER:
 405                                 if (found)
 406                                         return -EACCES;
 407                                 else
 408                                         goto check_perm;
 409                         default:
 410                                 return -EIO;
 411                 }
 412         }
 413         return -EIO;
 414
 415 mask:
 416         for (mask_obj = pa+1; mask_obj != pe; mask_obj++) {
 417                 if (mask_obj->e_tag == ACL_MASK) {
 418                         if ((pa->e_perm & mask_obj->e_perm & want) == want)
 419                                 return 0;
 420                         return -EACCES;
 421                 }
 422         }
 423
 424 check_perm:
 425         if ((pa->e_perm & want) == want)
 426                 return 0;
 427         return -EACCES;
 428 }
 429
 430 /*
 431  * Modify acl when creating a new inode. The caller must ensure the acl is
 432  * only referenced once.
 433  *
 434  * mode_p initially must contain the mode parameter to the open() / creat()
 435  * system calls. All permissions that are not granted by the acl are removed.
 436  * The permissions in the acl are changed to reflect the mode_p parameter.
 437  */
 438 static int posix_acl_create_masq(struct posix_acl *acl, umode_t *mode_p)
 439 {
 440         struct posix_acl_entry *pa, *pe;
 441         struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
 442         umode_t mode = *mode_p;
 443         int not_equiv = 0;
 444
 445         /* assert(atomic_read(acl->a_refcount) == 1); */
 446
 447         FOREACH_ACL_ENTRY(pa, acl, pe) {
 448                 switch(pa->e_tag) {
 449                         case ACL_USER_OBJ:
 450                                 pa->e_perm &= (mode >> 6) | ~S_IRWXO;
 451                                 mode &= (pa->e_perm << 6) | ~S_IRWXU;
 452                                 break;
 453
 454                         case ACL_USER:
 455                         case ACL_GROUP:
 456                                 not_equiv = 1;
 457                                 break;
 458
 459                         case ACL_GROUP_OBJ:
 460                                 group_obj = pa;
 461                                 break;
 462
 463                         case ACL_OTHER:
 464                                 pa->e_perm &= mode | ~S_IRWXO;
 465                                 mode &= pa->e_perm | ~S_IRWXO;
 466                                 break;
 467
 468                         case ACL_MASK:
 469                                 mask_obj = pa;
 470                                 not_equiv = 1;
 471                                 break;
 472
 473                         default:
 474                                 return -EIO;
 475                 }
 476         }
 477
 478         if (mask_obj) {
 479                 mask_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
 480                 mode &= (mask_obj->e_perm << 3) | ~S_IRWXG;
 481         } else {
 482                 if (!group_obj)
 483                         return -EIO;
 484                 group_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
 485                 mode &= (group_obj->e_perm << 3) | ~S_IRWXG;
 486         }
 487
 488         *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
 489         return not_equiv;
 490 }
 491
 492 /*
 493  * Modify the ACL for the chmod syscall.
 494  */
 495 static int __posix_acl_chmod_masq(struct posix_acl *acl, umode_t mode)
 496 {
 497         struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
 498         struct posix_acl_entry *pa, *pe;
 499
 500         /* assert(atomic_read(acl->a_refcount) == 1); */
 501
 502         FOREACH_ACL_ENTRY(pa, acl, pe) {
 503                 switch(pa->e_tag) {
 504                         case ACL_USER_OBJ:
 505                                 pa->e_perm = (mode & S_IRWXU) >> 6;
 506                                 break;
 507
 508                         case ACL_USER:
 509                         case ACL_GROUP:
 510                                 break;
 511
 512                         case ACL_GROUP_OBJ:
 513                                 group_obj = pa;
 514                                 break;
 515
 516                         case ACL_MASK:
 517                                 mask_obj = pa;
 518                                 break;
 519
 520                         case ACL_OTHER:
 521                                 pa->e_perm = (mode & S_IRWXO);
 522                                 break;
 523
 524                         default:
 525                                 return -EIO;
 526                 }
 527         }
 528
 529         if (mask_obj) {
 530                 mask_obj->e_perm = (mode & S_IRWXG) >> 3;
 531         } else {
 532                 if (!group_obj)
 533                         return -EIO;
 534                 group_obj->e_perm = (mode & S_IRWXG) >> 3;
 535         }
 536
 537         return 0;
 538 }
 539
 540 int
 541 __posix_acl_create(struct posix_acl **acl, gfp_t gfp, umode_t *mode_p)
 542 {
 543         struct posix_acl *clone = posix_acl_clone(*acl, gfp);
 544         int err = -ENOMEM;
 545         if (clone) {
 546                 err = posix_acl_create_masq(clone, mode_p);
 547                 if (err < 0) {
 548                         posix_acl_release(clone);
 549                         clone = NULL;
 550                 }
 551         }
 552         posix_acl_release(*acl);
 553         *acl = clone;
 554         return err;
 555 }
 556 EXPORT_SYMBOL(__posix_acl_create);
 557
 558 int
 559 __posix_acl_chmod(struct posix_acl **acl, gfp_t gfp, umode_t mode)
 560 {
 561         struct posix_acl *clone = posix_acl_clone(*acl, gfp);
 562         int err = -ENOMEM;
 563         if (clone) {
 564                 err = __posix_acl_chmod_masq(clone, mode);
 565                 if (err) {
 566                         posix_acl_release(clone);
 567                         clone = NULL;
 568                 }
 569         }
 570         posix_acl_release(*acl);
 571         *acl = clone;
 572         return err;
 573 }
 574 EXPORT_SYMBOL(__posix_acl_chmod);
 575
 576 /**
 577  * posix_acl_chmod - chmod a posix acl
 578  *
 579  * @mnt_userns: user namespace of the mount @inode was found from
 580  * @inode:      inode to check permissions on
 581  * @mode:       the new mode of @inode
 582  *
 583  * If the inode has been found through an idmapped mount the user namespace of
 584  * the vfsmount must be passed through @mnt_userns. This function will then
 585  * take care to map the inode according to @mnt_userns before checking
 586  * permissions. On non-idmapped mounts or if permission checking is to be
 587  * performed on the raw inode simply passs init_user_ns.
 588  */
 589 int
 590  posix_acl_chmod(struct user_namespace *mnt_userns, struct inode *inode,
 591                     umode_t mode)
 592 {
 593         struct posix_acl *acl;
 594         int ret = 0;
 595
 596         if (!IS_POSIXACL(inode))
 597                 return 0;
 598         if (!inode->i_op->set_acl)
 599                 return -EOPNOTSUPP;
 600
 601         acl = get_acl(inode, ACL_TYPE_ACCESS);
 602         if (IS_ERR_OR_NULL(acl)) {
 603                 if (acl == ERR_PTR(-EOPNOTSUPP))
 604                         return 0;
 605                 return PTR_ERR(acl);
 606         }
 607
 608         ret = __posix_acl_chmod(&acl, GFP_KERNEL, mode);
 609         if (ret)
 610                 return ret;
 611         ret = inode->i_op->set_acl(mnt_userns, inode, acl, ACL_TYPE_ACCESS);
 612         posix_acl_release(acl);
 613         return ret;
 614 }
 615 EXPORT_SYMBOL(posix_acl_chmod);
 616
 617 int
 618 posix_acl_create(struct inode *dir, umode_t *mode,
 619                 struct posix_acl **default_acl, struct posix_acl **acl)
 620 {
 621         struct posix_acl *p;
 622         struct posix_acl *clone;
 623         int ret;
 624
 625         *acl = NULL;
 626         *default_acl = NULL;
 627
 628         if (S_ISLNK(*mode) || !IS_POSIXACL(dir))
 629                 return 0;
 630
 631         p = get_acl(dir, ACL_TYPE_DEFAULT);
 632         if (!p || p == ERR_PTR(-EOPNOTSUPP)) {
 633                 *mode &= ~current_umask();
 634                 return 0;
 635         }
 636         if (IS_ERR(p))
 637                 return PTR_ERR(p);
 638
 639         ret = -ENOMEM;
 640         clone = posix_acl_clone(p, GFP_NOFS);
 641         if (!clone)
 642                 goto err_release;
 643
 644         ret = posix_acl_create_masq(clone, mode);
 645         if (ret < 0)
 646                 goto err_release_clone;
 647
 648         if (ret == 0)
 649                 posix_acl_release(clone);
 650         else
 651                 *acl = clone;
 652
 653         if (!S_ISDIR(*mode))
 654                 posix_acl_release(p);
 655         else
 656                 *default_acl = p;
 657
 658         return 0;
 659
 660 err_release_clone:
 661         posix_acl_release(clone);
 662 err_release:
 663         posix_acl_release(p);
 664         return ret;
 665 }
 666 EXPORT_SYMBOL_GPL(posix_acl_create);
 667
 668 /**
 669  * posix_acl_update_mode  -  update mode in set_acl
 670  * @mnt_userns: user namespace of the mount @inode was found from
 671  * @inode:      target inode
 672  * @mode_p:     mode (pointer) for update
 673  * @acl:        acl pointer
 674  *
 675  * Update the file mode when setting an ACL: compute the new file permission
 676  * bits based on the ACL.  In addition, if the ACL is equivalent to the new
 677  * file mode, set *@acl to NULL to indicate that no ACL should be set.
 678  *
 679  * As with chmod, clear the setgid bit if the caller is not in the owning group
 680  * or capable of CAP_FSETID (see inode_change_ok).
 681  *
 682  * If the inode has been found through an idmapped mount the user namespace of
 683  * the vfsmount must be passed through @mnt_userns. This function will then
 684  * take care to map the inode according to @mnt_userns before checking
 685  * permissions. On non-idmapped mounts or if permission checking is to be
 686  * performed on the raw inode simply passs init_user_ns.
 687  *
 688  * Called from set_acl inode operations.
 689  */
 690 int posix_acl_update_mode(struct user_namespace *mnt_userns,
 691                           struct inode *inode, umode_t *mode_p,
 692                           struct posix_acl **acl)
 693 {
 694         umode_t mode = inode->i_mode;
 695         int error;
 696
 697         error = posix_acl_equiv_mode(*acl, &mode);
 698         if (error < 0)
 699                 return error;
 700         if (error == 0)
 701                 *acl = NULL;
 702         if (!in_group_p(i_gid_into_mnt(mnt_userns, inode)) &&
 703             !capable_wrt_inode_uidgid(mnt_userns, inode, CAP_FSETID))
 704                 mode &= ~S_ISGID;
 705         *mode_p = mode;
 706         return 0;
 707 }
 708 EXPORT_SYMBOL(posix_acl_update_mode);
 709
 710 /*
 711  * Fix up the uids and gids in posix acl extended attributes in place.
 712  */
 713 static void posix_acl_fix_xattr_userns(
 714         struct user_namespace *to, struct user_namespace *from,
 715         struct user_namespace *mnt_userns,
 716         void *value, size_t size, bool from_user)
 717 {
 718         struct posix_acl_xattr_header *header = value;
 719         struct posix_acl_xattr_entry *entry = (void *)(header + 1), *end;
 720         int count;
 721         kuid_t uid;
 722         kgid_t gid;
 723
 724         if (!value)
 725                 return;
 726         if (size < sizeof(struct posix_acl_xattr_header))
 727                 return;
 728         if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
 729                 return;
 730
 731         count = posix_acl_xattr_count(size);
 732         if (count < 0)
 733                 return;
 734         if (count == 0)
 735                 return;
 736
 737         for (end = entry + count; entry != end; entry++) {
 738                 switch(le16_to_cpu(entry->e_tag)) {
 739                 case ACL_USER:
 740                         uid = make_kuid(from, le32_to_cpu(entry->e_id));
 741                         if (from_user)
 742                                 uid = mapped_kuid_user(mnt_userns, &init_user_ns, uid);
 743                         else
 744                                 uid = mapped_kuid_fs(mnt_userns, &init_user_ns, uid);
 745                         entry->e_id = cpu_to_le32(from_kuid(to, uid));
 746                         break;
 747                 case ACL_GROUP:
 748                         gid = make_kgid(from, le32_to_cpu(entry->e_id));
 749                         if (from_user)
 750                                 gid = mapped_kgid_user(mnt_userns, &init_user_ns, gid);
 751                         else
 752                                 gid = mapped_kgid_fs(mnt_userns, &init_user_ns, gid);
 753                         entry->e_id = cpu_to_le32(from_kgid(to, gid));
 754                         break;
 755                 default:
 756                         break;
 757                 }
 758         }
 759 }
 760
 761 void posix_acl_fix_xattr_from_user(struct user_namespace *mnt_userns,
 762                                    void *value, size_t size)
 763 {
 764         struct user_namespace *user_ns = current_user_ns();
 765         if ((user_ns == &init_user_ns) && (mnt_userns == &init_user_ns))
 766                 return;
 767         posix_acl_fix_xattr_userns(&init_user_ns, user_ns, mnt_userns, value,
 768                                    size, true);
 769 }
 770
 771 void posix_acl_fix_xattr_to_user(struct user_namespace *mnt_userns,
 772                                  void *value, size_t size)
 773 {
 774         struct user_namespace *user_ns = current_user_ns();
 775         if ((user_ns == &init_user_ns) && (mnt_userns == &init_user_ns))
 776                 return;
 777         posix_acl_fix_xattr_userns(user_ns, &init_user_ns, mnt_userns, value,
 778                                    size, false);
 779 }
 780
 781 /*
 782  * Convert from extended attribute to in-memory representation.
 783  */
 784 struct posix_acl *
 785 posix_acl_from_xattr(struct user_namespace *user_ns,
 786                      const void *value, size_t size)
 787 {
 788         const struct posix_acl_xattr_header *header = value;
 789         const struct posix_acl_xattr_entry *entry = (const void *)(header + 1), *end;
 790         int count;
 791         struct posix_acl *acl;
 792         struct posix_acl_entry *acl_e;
 793
 794         if (!value)
 795                 return NULL;
 796         if (size < sizeof(struct posix_acl_xattr_header))
 797                  return ERR_PTR(-EINVAL);
 798         if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
 799                 return ERR_PTR(-EOPNOTSUPP);
 800
 801         count = posix_acl_xattr_count(size);
 802         if (count < 0)
 803                 return ERR_PTR(-EINVAL);
 804         if (count == 0)
 805                 return NULL;
 806
 807         acl = posix_acl_alloc(count, GFP_NOFS);
 808         if (!acl)
 809                 return ERR_PTR(-ENOMEM);
 810         acl_e = acl->a_entries;
 811
 812         for (end = entry + count; entry != end; acl_e++, entry++) {
 813                 acl_e->e_tag  = le16_to_cpu(entry->e_tag);
 814                 acl_e->e_perm = le16_to_cpu(entry->e_perm);
 815
 816                 switch(acl_e->e_tag) {
 817                         case ACL_USER_OBJ:
 818                         case ACL_GROUP_OBJ:
 819                         case ACL_MASK:
 820                         case ACL_OTHER:
 821                                 break;
 822
 823                         case ACL_USER:
 824                                 acl_e->e_uid =
 825                                         make_kuid(user_ns,
 826                                                   le32_to_cpu(entry->e_id));
 827                                 if (!uid_valid(acl_e->e_uid))
 828                                         goto fail;
 829                                 break;
 830                         case ACL_GROUP:
 831                                 acl_e->e_gid =
 832                                         make_kgid(user_ns,
 833                                                   le32_to_cpu(entry->e_id));
 834                                 if (!gid_valid(acl_e->e_gid))
 835                                         goto fail;
 836                                 break;
 837
 838                         default:
 839                                 goto fail;
 840                 }
 841         }
 842         return acl;
 843
 844 fail:
 845         posix_acl_release(acl);
 846         return ERR_PTR(-EINVAL);
 847 }
 848 EXPORT_SYMBOL (posix_acl_from_xattr);
 849
 850 /*
 851  * Convert from in-memory to extended attribute representation.
 852  */
 853 int
 854 posix_acl_to_xattr(struct user_namespace *user_ns, const struct posix_acl *acl,
 855                    void *buffer, size_t size)
 856 {
 857         struct posix_acl_xattr_header *ext_acl = buffer;
 858         struct posix_acl_xattr_entry *ext_entry;
 859         int real_size, n;
 860
 861         real_size = posix_acl_xattr_size(acl->a_count);
 862         if (!buffer)
 863                 return real_size;
 864         if (real_size > size)
 865                 return -ERANGE;
 866
 867         ext_entry = (void *)(ext_acl + 1);
 868         ext_acl->a_version = cpu_to_le32(POSIX_ACL_XATTR_VERSION);
 869
 870         for (n=0; n < acl->a_count; n++, ext_entry++) {
 871                 const struct posix_acl_entry *acl_e = &acl->a_entries[n];
 872                 ext_entry->e_tag  = cpu_to_le16(acl_e->e_tag);
 873                 ext_entry->e_perm = cpu_to_le16(acl_e->e_perm);
 874                 switch(acl_e->e_tag) {
 875                 case ACL_USER:
 876                         ext_entry->e_id =
 877                                 cpu_to_le32(from_kuid(user_ns, acl_e->e_uid));
 878                         break;
 879                 case ACL_GROUP:
 880                         ext_entry->e_id =
 881                                 cpu_to_le32(from_kgid(user_ns, acl_e->e_gid));
 882                         break;
 883                 default:
 884                         ext_entry->e_id = cpu_to_le32(ACL_UNDEFINED_ID);
 885                         break;
 886                 }
 887         }
 888         return real_size;
 889 }
 890 EXPORT_SYMBOL (posix_acl_to_xattr);
 891
 892 static int
 893 posix_acl_xattr_get(const struct xattr_handler *handler,
 894                     struct dentry *unused, struct inode *inode,
 895                     const char *name, void *value, size_t size)
 896 {
 897         struct posix_acl *acl;
 898         int error;
 899
 900         if (!IS_POSIXACL(inode))
 901                 return -EOPNOTSUPP;
 902         if (S_ISLNK(inode->i_mode))
 903                 return -EOPNOTSUPP;
 904
 905         acl = get_acl(inode, handler->flags);
 906         if (IS_ERR(acl))
 907                 return PTR_ERR(acl);
 908         if (acl == NULL)
 909                 return -ENODATA;
 910
 911         error = posix_acl_to_xattr(&init_user_ns, acl, value, size);
 912         posix_acl_release(acl);
 913
 914         return error;
 915 }
 916
 917 int
 918 set_posix_acl(struct user_namespace *mnt_userns, struct inode *inode,
 919               int type, struct posix_acl *acl)
 920 {
 921         if (!IS_POSIXACL(inode))
 922                 return -EOPNOTSUPP;
 923         if (!inode->i_op->set_acl)
 924                 return -EOPNOTSUPP;
 925
 926         if (type == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode))
 927                 return acl ? -EACCES : 0;
 928         if (!inode_owner_or_capable(mnt_userns, inode))
 929                 return -EPERM;
 930
 931         if (acl) {
 932                 int ret = posix_acl_valid(inode->i_sb->s_user_ns, acl);
 933                 if (ret)
 934                         return ret;
 935         }
 936         return inode->i_op->set_acl(mnt_userns, inode, acl, type);
 937 }
 938 EXPORT_SYMBOL(set_posix_acl);
 939
 940 static int
 941 posix_acl_xattr_set(const struct xattr_handler *handler,
 942                            struct user_namespace *mnt_userns,
 943                            struct dentry *unused, struct inode *inode,
 944                            const char *name, const void *value, size_t size,
 945                            int flags)
 946 {
 947         struct posix_acl *acl = NULL;
 948         int ret;
 949
 950         if (value) {
 951                 acl = posix_acl_from_xattr(&init_user_ns, value, size);
 952                 if (IS_ERR(acl))
 953                         return PTR_ERR(acl);
 954         }
 955         ret = set_posix_acl(mnt_userns, inode, handler->flags, acl);
 956         posix_acl_release(acl);
 957         return ret;
 958 }
 959
 960 static bool
 961 posix_acl_xattr_list(struct dentry *dentry)
 962 {
 963         return IS_POSIXACL(d_backing_inode(dentry));
 964 }
 965
 966 const struct xattr_handler posix_acl_access_xattr_handler = {
 967         .name = XATTR_NAME_POSIX_ACL_ACCESS,
 968         .flags = ACL_TYPE_ACCESS,
 969         .list = posix_acl_xattr_list,
 970         .get = posix_acl_xattr_get,
 971         .set = posix_acl_xattr_set,
 972 };
 973 EXPORT_SYMBOL_GPL(posix_acl_access_xattr_handler);
 974
 975 const struct xattr_handler posix_acl_default_xattr_handler = {
 976         .name = XATTR_NAME_POSIX_ACL_DEFAULT,
 977         .flags = ACL_TYPE_DEFAULT,
 978         .list = posix_acl_xattr_list,
 979         .get = posix_acl_xattr_get,
 980         .set = posix_acl_xattr_set,
 981 };
 982 EXPORT_SYMBOL_GPL(posix_acl_default_xattr_handler);
 983
 984 int simple_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
 985                    struct posix_acl *acl, int type)
 986 {
 987         int error;
 988
 989         if (type == ACL_TYPE_ACCESS) {
 990                 error = posix_acl_update_mode(mnt_userns, inode,
 991                                 &inode->i_mode, &acl);
 992                 if (error)
 993                         return error;
 994         }
 995
 996         inode->i_ctime = current_time(inode);
 997         set_cached_acl(inode, type, acl);
 998         return 0;
 999 }
1000
1001 int simple_acl_create(struct inode *dir, struct inode *inode)
1002 {
1003         struct posix_acl *default_acl, *acl;
1004         int error;
1005
1006         error = posix_acl_create(dir, &inode->i_mode, &default_acl, &acl);
1007         if (error)
1008                 return error;
1009
1010         set_cached_acl(inode, ACL_TYPE_DEFAULT, default_acl);
1011         set_cached_acl(inode, ACL_TYPE_ACCESS, acl);
1012
1013         if (default_acl)
1014                 posix_acl_release(default_acl);
1015         if (acl)
1016                 posix_acl_release(acl);
1017         return 0;
1018 }