fs/posix_acl.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2002,2003 by Andreas Gruenbacher <[email protected]>
   4  *
   5  * Fixes from William Schumacher incorporated on 15 March 2001.
   6  *    (Reported by Charles Bertsch, <[email protected]>).
   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
  27 static struct posix_acl **acl_by_type(struct inode *inode, int type)
  28 {
  29         switch (type) {
  30         case ACL_TYPE_ACCESS:
  31                 return &inode->i_acl;
  32         case ACL_TYPE_DEFAULT:
  33                 return &inode->i_default_acl;
  34         default:
  35                 BUG();
  36         }
  37 }
  38
  39 struct posix_acl *get_cached_acl(struct inode *inode, int type)
  40 {
  41         struct posix_acl **p = acl_by_type(inode, type);
  42         struct posix_acl *acl;
  43
  44         for (;;) {
  45                 rcu_read_lock();
  46                 acl = rcu_dereference(*p);
  47                 if (!acl || is_uncached_acl(acl) ||
  48                     refcount_inc_not_zero(&acl->a_refcount))
  49                         break;
  50                 rcu_read_unlock();
  51                 cpu_relax();
  52         }
  53         rcu_read_unlock();
  54         return acl;
  55 }
  56 EXPORT_SYMBOL(get_cached_acl);
  57
  58 struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type)
  59 {
  60         struct posix_acl *acl = rcu_dereference(*acl_by_type(inode, type));
  61
  62         if (acl == ACL_DONT_CACHE) {
  63                 struct posix_acl *ret;
  64
  65                 ret = inode->i_op->get_acl(inode, type, LOOKUP_RCU);
  66                 if (!IS_ERR(ret))
  67                         acl = ret;
  68         }
  69
  70         return acl;
  71 }
  72 EXPORT_SYMBOL(get_cached_acl_rcu);
  73
  74 void set_cached_acl(struct inode *inode, int type, struct posix_acl *acl)
  75 {
  76         struct posix_acl **p = acl_by_type(inode, type);
  77         struct posix_acl *old;
  78
  79         old = xchg(p, posix_acl_dup(acl));
  80         if (!is_uncached_acl(old))
  81                 posix_acl_release(old);
  82 }
  83 EXPORT_SYMBOL(set_cached_acl);
  84
  85 static void __forget_cached_acl(struct posix_acl **p)
  86 {
  87         struct posix_acl *old;
  88
  89         old = xchg(p, ACL_NOT_CACHED);
  90         if (!is_uncached_acl(old))
  91                 posix_acl_release(old);
  92 }
  93
  94 void forget_cached_acl(struct inode *inode, int type)
  95 {
  96         __forget_cached_acl(acl_by_type(inode, type));
  97 }
  98 EXPORT_SYMBOL(forget_cached_acl);
  99
 100 void forget_all_cached_acls(struct inode *inode)
 101 {
 102         __forget_cached_acl(&inode->i_acl);
 103         __forget_cached_acl(&inode->i_default_acl);
 104 }
 105 EXPORT_SYMBOL(forget_all_cached_acls);
 106
 107 struct posix_acl *get_acl(struct inode *inode, int type)
 108 {
 109         void *sentinel;
 110         struct posix_acl **p;
 111         struct posix_acl *acl;
 112
 113         /*
 114          * The sentinel is used to detect when another operation like
 115          * set_cached_acl() or forget_cached_acl() races with get_acl().
 116          * It is guaranteed that is_uncached_acl(sentinel) is true.
 117          */
 118
 119         acl = get_cached_acl(inode, type);
 120         if (!is_uncached_acl(acl))
 121                 return acl;
 122
 123         if (!IS_POSIXACL(inode))
 124                 return NULL;
 125
 126         sentinel = uncached_acl_sentinel(current);
 127         p = acl_by_type(inode, type);
 128
 129         /*
 130          * If the ACL isn't being read yet, set our sentinel.  Otherwise, the
 131          * current value of the ACL will not be ACL_NOT_CACHED and so our own
 132          * sentinel will not be set; another task will update the cache.  We
 133          * could wait for that other task to complete its job, but it's easier
 134          * to just call ->get_acl to fetch the ACL ourself.  (This is going to
 135          * be an unlikely race.)
 136          */
 137         cmpxchg(p, ACL_NOT_CACHED, sentinel);
 138
 139         /*
 140          * Normally, the ACL returned by ->get_acl will be cached.
 141          * A filesystem can prevent that by calling
 142          * forget_cached_acl(inode, type) in ->get_acl.
 143          *
 144          * If the filesystem doesn't have a get_acl() function at all, we'll
 145          * just create the negative cache entry.
 146          */
 147         if (!inode->i_op->get_acl) {
 148                 set_cached_acl(inode, type, NULL);
 149                 return NULL;
 150         }
 151         acl = inode->i_op->get_acl(inode, type, false);
 152
 153         if (IS_ERR(acl)) {
 154                 /*
 155                  * Remove our sentinel so that we don't block future attempts
 156                  * to cache the ACL.
 157                  */
 158                 cmpxchg(p, sentinel, ACL_NOT_CACHED);
 159                 return acl;
 160         }
 161
 162         /*
 163          * Cache the result, but only if our sentinel is still in place.
 164          */
 165         posix_acl_dup(acl);
 166         if (unlikely(cmpxchg(p, sentinel, acl) != sentinel))
 167                 posix_acl_release(acl);
 168         return acl;
 169 }
 170 EXPORT_SYMBOL(get_acl);
 171
 172 /*
 173  * Init a fresh posix_acl
 174  */
 175 void
 176 posix_acl_init(struct posix_acl *acl, int count)
 177 {
 178         refcount_set(&acl->a_refcount, 1);
 179         acl->a_count = count;
 180 }
 181 EXPORT_SYMBOL(posix_acl_init);
 182
 183 /*
 184  * Allocate a new ACL with the specified number of entries.
 185  */
 186 struct posix_acl *
 187 posix_acl_alloc(int count, gfp_t flags)
 188 {
 189         const size_t size = sizeof(struct posix_acl) +
 190                             count * sizeof(struct posix_acl_entry);
 191         struct posix_acl *acl = kmalloc(size, flags);
 192         if (acl)
 193                 posix_acl_init(acl, count);
 194         return acl;
 195 }
 196 EXPORT_SYMBOL(posix_acl_alloc);
 197
 198 /*
 199  * Clone an ACL.
 200  */
 201 static struct posix_acl *
 202 posix_acl_clone(const struct posix_acl *acl, gfp_t flags)
 203 {
 204         struct posix_acl *clone = NULL;
 205
 206         if (acl) {
 207                 int size = sizeof(struct posix_acl) + acl->a_count *
 208                            sizeof(struct posix_acl_entry);
 209                 clone = kmemdup(acl, size, flags);
 210                 if (clone)
 211                         refcount_set(&clone->a_refcount, 1);
 212         }
 213         return clone;
 214 }
 215
 216 /*
 217  * Check if an acl is valid. Returns 0 if it is, or -E... otherwise.
 218  */
 219 int
 220 posix_acl_valid(struct user_namespace *user_ns, const struct posix_acl *acl)
 221 {
 222         const struct posix_acl_entry *pa, *pe;
 223         int state = ACL_USER_OBJ;
 224         int needs_mask = 0;
 225
 226         FOREACH_ACL_ENTRY(pa, acl, pe) {
 227                 if (pa->e_perm & ~(ACL_READ|ACL_WRITE|ACL_EXECUTE))
 228                         return -EINVAL;
 229                 switch (pa->e_tag) {
 230                         case ACL_USER_OBJ:
 231                                 if (state == ACL_USER_OBJ) {
 232                                         state = ACL_USER;
 233                                         break;
 234                                 }
 235                                 return -EINVAL;
 236
 237                         case ACL_USER:
 238                                 if (state != ACL_USER)
 239                                         return -EINVAL;
 240                                 if (!kuid_has_mapping(user_ns, pa->e_uid))
 241                                         return -EINVAL;
 242                                 needs_mask = 1;
 243                                 break;
 244
 245                         case ACL_GROUP_OBJ:
 246                                 if (state == ACL_USER) {
 247                                         state = ACL_GROUP;
 248                                         break;
 249                                 }
 250                                 return -EINVAL;
 251
 252                         case ACL_GROUP:
 253                                 if (state != ACL_GROUP)
 254                                         return -EINVAL;
 255                                 if (!kgid_has_mapping(user_ns, pa->e_gid))
 256                                         return -EINVAL;
 257                                 needs_mask = 1;
 258                                 break;
 259
 260                         case ACL_MASK:
 261                                 if (state != ACL_GROUP)
 262                                         return -EINVAL;
 263                                 state = ACL_OTHER;
 264                                 break;
 265
 266                         case ACL_OTHER:
 267                                 if (state == ACL_OTHER ||
 268                                     (state == ACL_GROUP && !needs_mask)) {
 269                                         state = 0;
 270                                         break;
 271                                 }
 272                                 return -EINVAL;
 273
 274                         default:
 275                                 return -EINVAL;
 276                 }
 277         }
 278         if (state == 0)
 279                 return 0;
 280         return -EINVAL;
 281 }
 282 EXPORT_SYMBOL(posix_acl_valid);
 283
 284 /*
 285  * Returns 0 if the acl can be exactly represented in the traditional
 286  * file mode permission bits, or else 1. Returns -E... on error.
 287  */
 288 int
 289 posix_acl_equiv_mode(const struct posix_acl *acl, umode_t *mode_p)
 290 {
 291         const struct posix_acl_entry *pa, *pe;
 292         umode_t mode = 0;
 293         int not_equiv = 0;
 294
 295         /*
 296          * A null ACL can always be presented as mode bits.
 297          */
 298         if (!acl)
 299                 return 0;
 300
 301         FOREACH_ACL_ENTRY(pa, acl, pe) {
 302                 switch (pa->e_tag) {
 303                         case ACL_USER_OBJ:
 304                                 mode |= (pa->e_perm & S_IRWXO) << 6;
 305                                 break;
 306                         case ACL_GROUP_OBJ:
 307                                 mode |= (pa->e_perm & S_IRWXO) << 3;
 308                                 break;
 309                         case ACL_OTHER:
 310                                 mode |= pa->e_perm & S_IRWXO;
 311                                 break;
 312                         case ACL_MASK:
 313                                 mode = (mode & ~S_IRWXG) |
 314                                        ((pa->e_perm & S_IRWXO) << 3);
 315                                 not_equiv = 1;
 316                                 break;
 317                         case ACL_USER:
 318                         case ACL_GROUP:
 319                                 not_equiv = 1;
 320                                 break;
 321                         default:
 322                                 return -EINVAL;
 323                 }
 324         }
 325         if (mode_p)
 326                 *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
 327         return not_equiv;
 328 }
 329 EXPORT_SYMBOL(posix_acl_equiv_mode);
 330
 331 /*
 332  * Create an ACL representing the file mode permission bits of an inode.
 333  */
 334 struct posix_acl *
 335 posix_acl_from_mode(umode_t mode, gfp_t flags)
 336 {
 337         struct posix_acl *acl = posix_acl_alloc(3, flags);
 338         if (!acl)
 339                 return ERR_PTR(-ENOMEM);
 340
 341         acl->a_entries[0].e_tag  = ACL_USER_OBJ;
 342         acl->a_entries[0].e_perm = (mode & S_IRWXU) >> 6;
 343
 344         acl->a_entries[1].e_tag  = ACL_GROUP_OBJ;
 345         acl->a_entries[1].e_perm = (mode & S_IRWXG) >> 3;
 346
 347         acl->a_entries[2].e_tag  = ACL_OTHER;
 348         acl->a_entries[2].e_perm = (mode & S_IRWXO);
 349         return acl;
 350 }
 351 EXPORT_SYMBOL(posix_acl_from_mode);
 352
 353 /*
 354  * Return 0 if current is granted want access to the inode
 355  * by the acl. Returns -E... otherwise.
 356  */
 357 int
 358 posix_acl_permission(struct user_namespace *mnt_userns, struct inode *inode,
 359                      const struct posix_acl *acl, int want)
 360 {
 361         const struct posix_acl_entry *pa, *pe, *mask_obj;
 362         int found = 0;
 363         kuid_t uid;
 364         kgid_t gid;
 365
 366         want &= MAY_READ | MAY_WRITE | MAY_EXEC;
 367
 368         FOREACH_ACL_ENTRY(pa, acl, pe) {
 369                 switch(pa->e_tag) {
 370                         case ACL_USER_OBJ:
 371                                 /* (May have been checked already) */
 372                                 uid = i_uid_into_mnt(mnt_userns, inode);
 373                                 if (uid_eq(uid, current_fsuid()))
 374                                         goto check_perm;
 375                                 break;
 376                         case ACL_USER:
 377                                 uid = kuid_into_mnt(mnt_userns, pa->e_uid);
 378                                 if (uid_eq(uid, current_fsuid()))
 379                                         goto mask;
 380                                 break;
 381                         case ACL_GROUP_OBJ:
 382                                 gid = i_gid_into_mnt(mnt_userns, inode);
 383                                 if (in_group_p(gid)) {
 384                                         found = 1;
 385                                         if ((pa->e_perm & want) == want)
 386                                                 goto mask;
 387                                 }
 388                                 break;
 389                         case ACL_GROUP:
 390                                 gid = kgid_into_mnt(mnt_userns, pa->e_gid);
 391                                 if (in_group_p(gid)) {
 392                                         found = 1;
 393                                         if ((pa->e_perm & want) == want)
 394                                                 goto mask;
 395                                 }
 396                                 break;
 397                         case ACL_MASK:
 398                                 break;
 399                         case ACL_OTHER:
 400                                 if (found)
 401                                         return -EACCES;
 402                                 else
 403                                         goto check_perm;
 404                         default:
 405                                 return -EIO;
 406                 }
 407         }
 408         return -EIO;
 409
 410 mask:
 411         for (mask_obj = pa+1; mask_obj != pe; mask_obj++) {
 412                 if (mask_obj->e_tag == ACL_MASK) {
 413                         if ((pa->e_perm & mask_obj->e_perm & want) == want)
 414                                 return 0;
 415                         return -EACCES;
 416                 }
 417         }
 418
 419 check_perm:
 420         if ((pa->e_perm & want) == want)
 421                 return 0;
 422         return -EACCES;
 423 }
 424
 425 /*
 426  * Modify acl when creating a new inode. The caller must ensure the acl is
 427  * only referenced once.
 428  *
 429  * mode_p initially must contain the mode parameter to the open() / creat()
 430  * system calls. All permissions that are not granted by the acl are removed.
 431  * The permissions in the acl are changed to reflect the mode_p parameter.
 432  */
 433 static int posix_acl_create_masq(struct posix_acl *acl, umode_t *mode_p)
 434 {
 435         struct posix_acl_entry *pa, *pe;
 436         struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
 437         umode_t mode = *mode_p;
 438         int not_equiv = 0;
 439
 440         /* assert(atomic_read(acl->a_refcount) == 1); */
 441
 442         FOREACH_ACL_ENTRY(pa, acl, pe) {
 443                 switch(pa->e_tag) {
 444                         case ACL_USER_OBJ:
 445                                 pa->e_perm &= (mode >> 6) | ~S_IRWXO;
 446                                 mode &= (pa->e_perm << 6) | ~S_IRWXU;
 447                                 break;
 448
 449                         case ACL_USER:
 450                         case ACL_GROUP:
 451                                 not_equiv = 1;
 452                                 break;
 453
 454                         case ACL_GROUP_OBJ:
 455                                 group_obj = pa;
 456                                 break;
 457
 458                         case ACL_OTHER:
 459                                 pa->e_perm &= mode | ~S_IRWXO;
 460                                 mode &= pa->e_perm | ~S_IRWXO;
 461                                 break;
 462
 463                         case ACL_MASK:
 464                                 mask_obj = pa;
 465                                 not_equiv = 1;
 466                                 break;
 467
 468                         default:
 469                                 return -EIO;
 470                 }
 471         }
 472
 473         if (mask_obj) {
 474                 mask_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
 475                 mode &= (mask_obj->e_perm << 3) | ~S_IRWXG;
 476         } else {
 477                 if (!group_obj)
 478                         return -EIO;
 479                 group_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
 480                 mode &= (group_obj->e_perm << 3) | ~S_IRWXG;
 481         }
 482
 483         *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
 484         return not_equiv;
 485 }
 486
 487 /*
 488  * Modify the ACL for the chmod syscall.
 489  */
 490 static int __posix_acl_chmod_masq(struct posix_acl *acl, umode_t mode)
 491 {
 492         struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
 493         struct posix_acl_entry *pa, *pe;
 494
 495         /* assert(atomic_read(acl->a_refcount) == 1); */
 496
 497         FOREACH_ACL_ENTRY(pa, acl, pe) {
 498                 switch(pa->e_tag) {
 499                         case ACL_USER_OBJ:
 500                                 pa->e_perm = (mode & S_IRWXU) >> 6;
 501                                 break;
 502
 503                         case ACL_USER:
 504                         case ACL_GROUP:
 505                                 break;
 506
 507                         case ACL_GROUP_OBJ:
 508                                 group_obj = pa;
 509                                 break;
 510
 511                         case ACL_MASK:
 512                                 mask_obj = pa;
 513                                 break;
 514
 515                         case ACL_OTHER:
 516                                 pa->e_perm = (mode & S_IRWXO);
 517                                 break;
 518
 519                         default:
 520                                 return -EIO;
 521                 }
 522         }
 523
 524         if (mask_obj) {
 525                 mask_obj->e_perm = (mode & S_IRWXG) >> 3;
 526         } else {
 527                 if (!group_obj)
 528                         return -EIO;
 529                 group_obj->e_perm = (mode & S_IRWXG) >> 3;
 530         }
 531
 532         return 0;
 533 }
 534
 535 int
 536 __posix_acl_create(struct posix_acl **acl, gfp_t gfp, umode_t *mode_p)
 537 {
 538         struct posix_acl *clone = posix_acl_clone(*acl, gfp);
 539         int err = -ENOMEM;
 540         if (clone) {
 541                 err = posix_acl_create_masq(clone, mode_p);
 542                 if (err < 0) {
 543                         posix_acl_release(clone);
 544                         clone = NULL;
 545                 }
 546         }
 547         posix_acl_release(*acl);
 548         *acl = clone;
 549         return err;
 550 }
 551 EXPORT_SYMBOL(__posix_acl_create);
 552
 553 int
 554 __posix_acl_chmod(struct posix_acl **acl, gfp_t gfp, umode_t mode)
 555 {
 556         struct posix_acl *clone = posix_acl_clone(*acl, gfp);
 557         int err = -ENOMEM;
 558         if (clone) {
 559                 err = __posix_acl_chmod_masq(clone, mode);
 560                 if (err) {
 561                         posix_acl_release(clone);
 562                         clone = NULL;
 563                 }
 564         }
 565         posix_acl_release(*acl);
 566         *acl = clone;
 567         return err;
 568 }
 569 EXPORT_SYMBOL(__posix_acl_chmod);
 570
 571 /**
 572  * posix_acl_chmod - chmod a posix acl
 573  *
 574  * @mnt_userns: user namespace of the mount @inode was found from
 575  * @inode:      inode to check permissions on
 576  * @mode:       the new mode of @inode
 577  *
 578  * If the inode has been found through an idmapped mount the user namespace of
 579  * the vfsmount must be passed through @mnt_userns. This function will then
 580  * take care to map the inode according to @mnt_userns before checking
 581  * permissions. On non-idmapped mounts or if permission checking is to be
 582  * performed on the raw inode simply passs init_user_ns.
 583  */
 584 int
 585  posix_acl_chmod(struct user_namespace *mnt_userns, struct inode *inode,
 586                     umode_t mode)
 587 {
 588         struct posix_acl *acl;
 589         int ret = 0;
 590
 591         if (!IS_POSIXACL(inode))
 592                 return 0;
 593         if (!inode->i_op->set_acl)
 594                 return -EOPNOTSUPP;
 595
 596         acl = get_acl(inode, ACL_TYPE_ACCESS);
 597         if (IS_ERR_OR_NULL(acl)) {
 598                 if (acl == ERR_PTR(-EOPNOTSUPP))
 599                         return 0;
 600                 return PTR_ERR(acl);
 601         }
 602
 603         ret = __posix_acl_chmod(&acl, GFP_KERNEL, mode);
 604         if (ret)
 605                 return ret;
 606         ret = inode->i_op->set_acl(mnt_userns, inode, acl, ACL_TYPE_ACCESS);
 607         posix_acl_release(acl);
 608         return ret;
 609 }
 610 EXPORT_SYMBOL(posix_acl_chmod);
 611
 612 int
 613 posix_acl_create(struct inode *dir, umode_t *mode,
 614                 struct posix_acl **default_acl, struct posix_acl **acl)
 615 {
 616         struct posix_acl *p;
 617         struct posix_acl *clone;
 618         int ret;
 619
 620         *acl = NULL;
 621         *default_acl = NULL;
 622
 623         if (S_ISLNK(*mode) || !IS_POSIXACL(dir))
 624                 return 0;
 625
 626         p = get_acl(dir, ACL_TYPE_DEFAULT);
 627         if (!p || p == ERR_PTR(-EOPNOTSUPP)) {
 628                 *mode &= ~current_umask();
 629                 return 0;
 630         }
 631         if (IS_ERR(p))
 632                 return PTR_ERR(p);
 633
 634         ret = -ENOMEM;
 635         clone = posix_acl_clone(p, GFP_NOFS);
 636         if (!clone)
 637                 goto err_release;
 638
 639         ret = posix_acl_create_masq(clone, mode);
 640         if (ret < 0)
 641                 goto err_release_clone;
 642
 643         if (ret == 0)
 644                 posix_acl_release(clone);
 645         else
 646                 *acl = clone;
 647
 648         if (!S_ISDIR(*mode))
 649                 posix_acl_release(p);
 650         else
 651                 *default_acl = p;
 652
 653         return 0;
 654
 655 err_release_clone:
 656         posix_acl_release(clone);
 657 err_release:
 658         posix_acl_release(p);
 659         return ret;
 660 }
 661 EXPORT_SYMBOL_GPL(posix_acl_create);
 662
 663 /**
 664  * posix_acl_update_mode  -  update mode in set_acl
 665  * @mnt_userns: user namespace of the mount @inode was found from
 666  * @inode:      target inode
 667  * @mode_p:     mode (pointer) for update
 668  * @acl:        acl pointer
 669  *
 670  * Update the file mode when setting an ACL: compute the new file permission
 671  * bits based on the ACL.  In addition, if the ACL is equivalent to the new
 672  * file mode, set *@acl to NULL to indicate that no ACL should be set.
 673  *
 674  * As with chmod, clear the setgid bit if the caller is not in the owning group
 675  * or capable of CAP_FSETID (see inode_change_ok).
 676  *
 677  * If the inode has been found through an idmapped mount the user namespace of
 678  * the vfsmount must be passed through @mnt_userns. This function will then
 679  * take care to map the inode according to @mnt_userns before checking
 680  * permissions. On non-idmapped mounts or if permission checking is to be
 681  * performed on the raw inode simply passs init_user_ns.
 682  *
 683  * Called from set_acl inode operations.
 684  */
 685 int posix_acl_update_mode(struct user_namespace *mnt_userns,
 686                           struct inode *inode, umode_t *mode_p,
 687                           struct posix_acl **acl)
 688 {
 689         umode_t mode = inode->i_mode;
 690         int error;
 691
 692         error = posix_acl_equiv_mode(*acl, &mode);
 693         if (error < 0)
 694                 return error;
 695         if (error == 0)
 696                 *acl = NULL;
 697         if (!in_group_p(i_gid_into_mnt(mnt_userns, inode)) &&
 698             !capable_wrt_inode_uidgid(mnt_userns, inode, CAP_FSETID))
 699                 mode &= ~S_ISGID;
 700         *mode_p = mode;
 701         return 0;
 702 }
 703 EXPORT_SYMBOL(posix_acl_update_mode);
 704
 705 /*
 706  * Fix up the uids and gids in posix acl extended attributes in place.
 707  */
 708 static void posix_acl_fix_xattr_userns(
 709         struct user_namespace *to, struct user_namespace *from,
 710         struct user_namespace *mnt_userns,
 711         void *value, size_t size, bool from_user)
 712 {
 713         struct posix_acl_xattr_header *header = value;
 714         struct posix_acl_xattr_entry *entry = (void *)(header + 1), *end;
 715         int count;
 716         kuid_t uid;
 717         kgid_t gid;
 718
 719         if (!value)
 720                 return;
 721         if (size < sizeof(struct posix_acl_xattr_header))
 722                 return;
 723         if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
 724                 return;
 725
 726         count = posix_acl_xattr_count(size);
 727         if (count < 0)
 728                 return;
 729         if (count == 0)
 730                 return;
 731
 732         for (end = entry + count; entry != end; entry++) {
 733                 switch(le16_to_cpu(entry->e_tag)) {
 734                 case ACL_USER:
 735                         uid = make_kuid(from, le32_to_cpu(entry->e_id));
 736                         if (from_user)
 737                                 uid = kuid_from_mnt(mnt_userns, uid);
 738                         else
 739                                 uid = kuid_into_mnt(mnt_userns, uid);
 740                         entry->e_id = cpu_to_le32(from_kuid(to, uid));
 741                         break;
 742                 case ACL_GROUP:
 743                         gid = make_kgid(from, le32_to_cpu(entry->e_id));
 744                         if (from_user)
 745                                 gid = kgid_from_mnt(mnt_userns, gid);
 746                         else
 747                                 gid = kgid_into_mnt(mnt_userns, gid);
 748                         entry->e_id = cpu_to_le32(from_kgid(to, gid));
 749                         break;
 750                 default:
 751                         break;
 752                 }
 753         }
 754 }
 755
 756 void posix_acl_fix_xattr_from_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(&init_user_ns, user_ns, mnt_userns, value,
 763                                    size, true);
 764 }
 765
 766 void posix_acl_fix_xattr_to_user(struct user_namespace *mnt_userns,
 767                                  void *value, size_t size)
 768 {
 769         struct user_namespace *user_ns = current_user_ns();
 770         if ((user_ns == &init_user_ns) && (mnt_userns == &init_user_ns))
 771                 return;
 772         posix_acl_fix_xattr_userns(user_ns, &init_user_ns, mnt_userns, value,
 773                                    size, false);
 774 }
 775
 776 /*
 777  * Convert from extended attribute to in-memory representation.
 778  */
 779 struct posix_acl *
 780 posix_acl_from_xattr(struct user_namespace *user_ns,
 781                      const void *value, size_t size)
 782 {
 783         const struct posix_acl_xattr_header *header = value;
 784         const struct posix_acl_xattr_entry *entry = (const void *)(header + 1), *end;
 785         int count;
 786         struct posix_acl *acl;
 787         struct posix_acl_entry *acl_e;
 788
 789         if (!value)
 790                 return NULL;
 791         if (size < sizeof(struct posix_acl_xattr_header))
 792                  return ERR_PTR(-EINVAL);
 793         if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
 794                 return ERR_PTR(-EOPNOTSUPP);
 795
 796         count = posix_acl_xattr_count(size);
 797         if (count < 0)
 798                 return ERR_PTR(-EINVAL);
 799         if (count == 0)
 800                 return NULL;
 801
 802         acl = posix_acl_alloc(count, GFP_NOFS);
 803         if (!acl)
 804                 return ERR_PTR(-ENOMEM);
 805         acl_e = acl->a_entries;
 806
 807         for (end = entry + count; entry != end; acl_e++, entry++) {
 808                 acl_e->e_tag  = le16_to_cpu(entry->e_tag);
 809                 acl_e->e_perm = le16_to_cpu(entry->e_perm);
 810
 811                 switch(acl_e->e_tag) {
 812                         case ACL_USER_OBJ:
 813                         case ACL_GROUP_OBJ:
 814                         case ACL_MASK:
 815                         case ACL_OTHER:
 816                                 break;
 817
 818                         case ACL_USER:
 819                                 acl_e->e_uid =
 820                                         make_kuid(user_ns,
 821                                                   le32_to_cpu(entry->e_id));
 822                                 if (!uid_valid(acl_e->e_uid))
 823                                         goto fail;
 824                                 break;
 825                         case ACL_GROUP:
 826                                 acl_e->e_gid =
 827                                         make_kgid(user_ns,
 828                                                   le32_to_cpu(entry->e_id));
 829                                 if (!gid_valid(acl_e->e_gid))
 830                                         goto fail;
 831                                 break;
 832
 833                         default:
 834                                 goto fail;
 835                 }
 836         }
 837         return acl;
 838
 839 fail:
 840         posix_acl_release(acl);
 841         return ERR_PTR(-EINVAL);
 842 }
 843 EXPORT_SYMBOL (posix_acl_from_xattr);
 844
 845 /*
 846  * Convert from in-memory to extended attribute representation.
 847  */
 848 int
 849 posix_acl_to_xattr(struct user_namespace *user_ns, const struct posix_acl *acl,
 850                    void *buffer, size_t size)
 851 {
 852         struct posix_acl_xattr_header *ext_acl = buffer;
 853         struct posix_acl_xattr_entry *ext_entry;
 854         int real_size, n;
 855
 856         real_size = posix_acl_xattr_size(acl->a_count);
 857         if (!buffer)
 858                 return real_size;
 859         if (real_size > size)
 860                 return -ERANGE;
 861
 862         ext_entry = (void *)(ext_acl + 1);
 863         ext_acl->a_version = cpu_to_le32(POSIX_ACL_XATTR_VERSION);
 864
 865         for (n=0; n < acl->a_count; n++, ext_entry++) {
 866                 const struct posix_acl_entry *acl_e = &acl->a_entries[n];
 867                 ext_entry->e_tag  = cpu_to_le16(acl_e->e_tag);
 868                 ext_entry->e_perm = cpu_to_le16(acl_e->e_perm);
 869                 switch(acl_e->e_tag) {
 870                 case ACL_USER:
 871                         ext_entry->e_id =
 872                                 cpu_to_le32(from_kuid(user_ns, acl_e->e_uid));
 873                         break;
 874                 case ACL_GROUP:
 875                         ext_entry->e_id =
 876                                 cpu_to_le32(from_kgid(user_ns, acl_e->e_gid));
 877                         break;
 878                 default:
 879                         ext_entry->e_id = cpu_to_le32(ACL_UNDEFINED_ID);
 880                         break;
 881                 }
 882         }
 883         return real_size;
 884 }
 885 EXPORT_SYMBOL (posix_acl_to_xattr);
 886
 887 static int
 888 posix_acl_xattr_get(const struct xattr_handler *handler,
 889                     struct dentry *unused, struct inode *inode,
 890                     const char *name, void *value, size_t size)
 891 {
 892         struct posix_acl *acl;
 893         int error;
 894
 895         if (!IS_POSIXACL(inode))
 896                 return -EOPNOTSUPP;
 897         if (S_ISLNK(inode->i_mode))
 898                 return -EOPNOTSUPP;
 899
 900         acl = get_acl(inode, handler->flags);
 901         if (IS_ERR(acl))
 902                 return PTR_ERR(acl);
 903         if (acl == NULL)
 904                 return -ENODATA;
 905
 906         error = posix_acl_to_xattr(&init_user_ns, acl, value, size);
 907         posix_acl_release(acl);
 908
 909         return error;
 910 }
 911
 912 int
 913 set_posix_acl(struct user_namespace *mnt_userns, struct inode *inode,
 914               int type, struct posix_acl *acl)
 915 {
 916         if (!IS_POSIXACL(inode))
 917                 return -EOPNOTSUPP;
 918         if (!inode->i_op->set_acl)
 919                 return -EOPNOTSUPP;
 920
 921         if (type == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode))
 922                 return acl ? -EACCES : 0;
 923         if (!inode_owner_or_capable(mnt_userns, inode))
 924                 return -EPERM;
 925
 926         if (acl) {
 927                 int ret = posix_acl_valid(inode->i_sb->s_user_ns, acl);
 928                 if (ret)
 929                         return ret;
 930         }
 931         return inode->i_op->set_acl(mnt_userns, inode, acl, type);
 932 }
 933 EXPORT_SYMBOL(set_posix_acl);
 934
 935 static int
 936 posix_acl_xattr_set(const struct xattr_handler *handler,
 937                            struct user_namespace *mnt_userns,
 938                            struct dentry *unused, struct inode *inode,
 939                            const char *name, const void *value, size_t size,
 940                            int flags)
 941 {
 942         struct posix_acl *acl = NULL;
 943         int ret;
 944
 945         if (value) {
 946                 acl = posix_acl_from_xattr(&init_user_ns, value, size);
 947                 if (IS_ERR(acl))
 948                         return PTR_ERR(acl);
 949         }
 950         ret = set_posix_acl(mnt_userns, inode, handler->flags, acl);
 951         posix_acl_release(acl);
 952         return ret;
 953 }
 954
 955 static bool
 956 posix_acl_xattr_list(struct dentry *dentry)
 957 {
 958         return IS_POSIXACL(d_backing_inode(dentry));
 959 }
 960
 961 const struct xattr_handler posix_acl_access_xattr_handler = {
 962         .name = XATTR_NAME_POSIX_ACL_ACCESS,
 963         .flags = ACL_TYPE_ACCESS,
 964         .list = posix_acl_xattr_list,
 965         .get = posix_acl_xattr_get,
 966         .set = posix_acl_xattr_set,
 967 };
 968 EXPORT_SYMBOL_GPL(posix_acl_access_xattr_handler);
 969
 970 const struct xattr_handler posix_acl_default_xattr_handler = {
 971         .name = XATTR_NAME_POSIX_ACL_DEFAULT,
 972         .flags = ACL_TYPE_DEFAULT,
 973         .list = posix_acl_xattr_list,
 974         .get = posix_acl_xattr_get,
 975         .set = posix_acl_xattr_set,
 976 };
 977 EXPORT_SYMBOL_GPL(posix_acl_default_xattr_handler);
 978
 979 int simple_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
 980                    struct posix_acl *acl, int type)
 981 {
 982         int error;
 983
 984         if (type == ACL_TYPE_ACCESS) {
 985                 error = posix_acl_update_mode(mnt_userns, inode,
 986                                 &inode->i_mode, &acl);
 987                 if (error)
 988                         return error;
 989         }
 990
 991         inode->i_ctime = current_time(inode);
 992         set_cached_acl(inode, type, acl);
 993         return 0;
 994 }
 995
 996 int simple_acl_create(struct inode *dir, struct inode *inode)
 997 {
 998         struct posix_acl *default_acl, *acl;
 999         int error;
1000
1001         error = posix_acl_create(dir, &inode->i_mode, &default_acl, &acl);
1002         if (error)
1003                 return error;
1004
1005         set_cached_acl(inode, ACL_TYPE_DEFAULT, default_acl);
1006         set_cached_acl(inode, ACL_TYPE_ACCESS, acl);
1007
1008         if (default_acl)
1009                 posix_acl_release(default_acl);
1010         if (acl)
1011                 posix_acl_release(acl);
1012         return 0;
1013 }