fs/ext2/acl.c

   1 /*
   2  * linux/fs/ext2/acl.c
   3  *
   4  * Copyright (C) 2001-2003 Andreas Gruenbacher, <agruen@suse.de>
   5  */
   6
   7 #include <linux/init.h>
   8 #include <linux/sched.h>
   9 #include <linux/slab.h>
  10 #include <linux/fs.h>
  11 #include <linux/namei.h>
  12 #include "ext2.h"
  13 #include "xattr.h"
  14 #include "acl.h"
  15
  16 /*
  17  * Convert from filesystem to in-memory representation.
  18  */
  19 static struct posix_acl *
  20 ext2_acl_from_disk(const void *value, size_t size)
  21 {
  22         const char *end = (char *)value + size;
  23         int n, count;
  24         struct posix_acl *acl;
  25
  26         if (!value)
  27                 return NULL;
  28         if (size < sizeof(ext2_acl_header))
  29                  return ERR_PTR(-EINVAL);
  30         if (((ext2_acl_header *)value)->a_version !=
  31             cpu_to_le32(EXT2_ACL_VERSION))
  32                 return ERR_PTR(-EINVAL);
  33         value = (char *)value + sizeof(ext2_acl_header);
  34         count = ext2_acl_count(size);
  35         if (count < 0)
  36                 return ERR_PTR(-EINVAL);
  37         if (count == 0)
  38                 return NULL;
  39         acl = posix_acl_alloc(count, GFP_KERNEL);
  40         if (!acl)
  41                 return ERR_PTR(-ENOMEM);
  42         for (n=0; n < count; n++) {
  43                 ext2_acl_entry *entry =
  44                         (ext2_acl_entry *)value;
  45                 if ((char *)value + sizeof(ext2_acl_entry_short) > end)
  46                         goto fail;
  47                 acl->a_entries[n].e_tag  = le16_to_cpu(entry->e_tag);
  48                 acl->a_entries[n].e_perm = le16_to_cpu(entry->e_perm);
  49                 switch(acl->a_entries[n].e_tag) {
  50                         case ACL_USER_OBJ:
  51                         case ACL_GROUP_OBJ:
  52                         case ACL_MASK:
  53                         case ACL_OTHER:
  54                                 value = (char *)value +
  55                                         sizeof(ext2_acl_entry_short);
  56                                 acl->a_entries[n].e_id = ACL_UNDEFINED_ID;
  57                                 break;
  58
  59                         case ACL_USER:
  60                         case ACL_GROUP:
  61                                 value = (char *)value + sizeof(ext2_acl_entry);
  62                                 if ((char *)value > end)
  63                                         goto fail;
  64                                 acl->a_entries[n].e_id =
  65                                         le32_to_cpu(entry->e_id);
  66                                 break;
  67
  68                         default:
  69                                 goto fail;
  70                 }
  71         }
  72         if (value != end)
  73                 goto fail;
  74         return acl;
  75
  76 fail:
  77         posix_acl_release(acl);
  78         return ERR_PTR(-EINVAL);
  79 }
  80
  81 /*
  82  * Convert from in-memory to filesystem representation.
  83  */
  84 static void *
  85 ext2_acl_to_disk(const struct posix_acl *acl, size_t *size)
  86 {
  87         ext2_acl_header *ext_acl;
  88         char *e;
  89         size_t n;
  90
  91         *size = ext2_acl_size(acl->a_count);
  92         ext_acl = (ext2_acl_header *)kmalloc(sizeof(ext2_acl_header) +
  93                 acl->a_count * sizeof(ext2_acl_entry), GFP_KERNEL);
  94         if (!ext_acl)
  95                 return ERR_PTR(-ENOMEM);
  96         ext_acl->a_version = cpu_to_le32(EXT2_ACL_VERSION);
  97         e = (char *)ext_acl + sizeof(ext2_acl_header);
  98         for (n=0; n < acl->a_count; n++) {
  99                 ext2_acl_entry *entry = (ext2_acl_entry *)e;
 100                 entry->e_tag  = cpu_to_le16(acl->a_entries[n].e_tag);
 101                 entry->e_perm = cpu_to_le16(acl->a_entries[n].e_perm);
 102                 switch(acl->a_entries[n].e_tag) {
 103                         case ACL_USER:
 104                         case ACL_GROUP:
 105                                 entry->e_id =
 106                                         cpu_to_le32(acl->a_entries[n].e_id);
 107                                 e += sizeof(ext2_acl_entry);
 108                                 break;
 109
 110                         case ACL_USER_OBJ:
 111                         case ACL_GROUP_OBJ:
 112                         case ACL_MASK:
 113                         case ACL_OTHER:
 114                                 e += sizeof(ext2_acl_entry_short);
 115                                 break;
 116
 117                         default:
 118                                 goto fail;
 119                 }
 120         }
 121         return (char *)ext_acl;
 122
 123 fail:
 124         kfree(ext_acl);
 125         return ERR_PTR(-EINVAL);
 126 }
 127
 128 static inline struct posix_acl *
 129 ext2_iget_acl(struct inode *inode, struct posix_acl **i_acl)
 130 {
 131         struct posix_acl *acl = EXT2_ACL_NOT_CACHED;
 132
 133         spin_lock(&inode->i_lock);
 134         if (*i_acl != EXT2_ACL_NOT_CACHED)
 135                 acl = posix_acl_dup(*i_acl);
 136         spin_unlock(&inode->i_lock);
 137
 138         return acl;
 139 }
 140
 141 static inline void
 142 ext2_iset_acl(struct inode *inode, struct posix_acl **i_acl,
 143                    struct posix_acl *acl)
 144 {
 145         spin_lock(&inode->i_lock);
 146         if (*i_acl != EXT2_ACL_NOT_CACHED)
 147                 posix_acl_release(*i_acl);
 148         *i_acl = posix_acl_dup(acl);
 149         spin_unlock(&inode->i_lock);
 150 }
 151
 152 /*
 153  * inode->i_sem: don't care
 154  */
 155 static struct posix_acl *
 156 ext2_get_acl(struct inode *inode, int type)
 157 {
 158         struct ext2_inode_info *ei = EXT2_I(inode);
 159         int name_index;
 160         char *value = NULL;
 161         struct posix_acl *acl;
 162         int retval;
 163
 164         if (!test_opt(inode->i_sb, POSIX_ACL))
 165                 return NULL;
 166
 167         switch(type) {
 168                 case ACL_TYPE_ACCESS:
 169                         acl = ext2_iget_acl(inode, &ei->i_acl);
 170                         if (acl != EXT2_ACL_NOT_CACHED)
 171                                 return acl;
 172                         name_index = EXT2_XATTR_INDEX_POSIX_ACL_ACCESS;
 173                         break;
 174
 175                 case ACL_TYPE_DEFAULT:
 176                         acl = ext2_iget_acl(inode, &ei->i_default_acl);
 177                         if (acl != EXT2_ACL_NOT_CACHED)
 178                                 return acl;
 179                         name_index = EXT2_XATTR_INDEX_POSIX_ACL_DEFAULT;
 180                         break;
 181
 182                 default:
 183                         return ERR_PTR(-EINVAL);
 184         }
 185         retval = ext2_xattr_get(inode, name_index, "", NULL, 0);
 186         if (retval > 0) {
 187                 value = kmalloc(retval, GFP_KERNEL);
 188                 if (!value)
 189                         return ERR_PTR(-ENOMEM);
 190                 retval = ext2_xattr_get(inode, name_index, "", value, retval);
 191         }
 192         if (retval > 0)
 193                 acl = ext2_acl_from_disk(value, retval);
 194         else if (retval == -ENODATA || retval == -ENOSYS)
 195                 acl = NULL;
 196         else
 197                 acl = ERR_PTR(retval);
 198         if (value)
 199                 kfree(value);
 200
 201         if (!IS_ERR(acl)) {
 202                 switch(type) {
 203                         case ACL_TYPE_ACCESS:
 204                                 ext2_iset_acl(inode, &ei->i_acl, acl);
 205                                 break;
 206
 207                         case ACL_TYPE_DEFAULT:
 208                                 ext2_iset_acl(inode, &ei->i_default_acl, acl);
 209                                 break;
 210                 }
 211         }
 212         return acl;
 213 }
 214
 215 /*
 216  * inode->i_sem: down
 217  */
 218 static int
 219 ext2_set_acl(struct inode *inode, int type, struct posix_acl *acl)
 220 {
 221         struct ext2_inode_info *ei = EXT2_I(inode);
 222         int name_index;
 223         void *value = NULL;
 224         size_t size;
 225         int error;
 226
 227         if (S_ISLNK(inode->i_mode))
 228                 return -EOPNOTSUPP;
 229         if (!test_opt(inode->i_sb, POSIX_ACL))
 230                 return 0;
 231
 232         switch(type) {
 233                 case ACL_TYPE_ACCESS:
 234                         name_index = EXT2_XATTR_INDEX_POSIX_ACL_ACCESS;
 235                         if (acl) {
 236                                 mode_t mode = inode->i_mode;
 237                                 error = posix_acl_equiv_mode(acl, &mode);
 238                                 if (error < 0)
 239                                         return error;
 240                                 else {
 241                                         inode->i_mode = mode;
 242                                         mark_inode_dirty(inode);
 243                                         if (error == 0)
 244                                                 acl = NULL;
 245                                 }
 246                         }
 247                         break;
 248
 249                 case ACL_TYPE_DEFAULT:
 250                         name_index = EXT2_XATTR_INDEX_POSIX_ACL_DEFAULT;
 251                         if (!S_ISDIR(inode->i_mode))
 252                                 return acl ? -EACCES : 0;
 253                         break;
 254
 255                 default:
 256                         return -EINVAL;
 257         }
 258         if (acl) {
 259                 if (acl->a_count > EXT2_ACL_MAX_ENTRIES)
 260                         return -EINVAL;
 261                 value = ext2_acl_to_disk(acl, &size);
 262                 if (IS_ERR(value))
 263                         return (int)PTR_ERR(value);
 264         }
 265
 266         error = ext2_xattr_set(inode, name_index, "", value, size, 0);
 267
 268         if (value)
 269                 kfree(value);
 270         if (!error) {
 271                 switch(type) {
 272                         case ACL_TYPE_ACCESS:
 273                                 ext2_iset_acl(inode, &ei->i_acl, acl);
 274                                 break;
 275
 276                         case ACL_TYPE_DEFAULT:
 277                                 ext2_iset_acl(inode, &ei->i_default_acl, acl);
 278                                 break;
 279                 }
 280         }
 281         return error;
 282 }
 283
 284 /*
 285  * Inode operation permission().
 286  *
 287  * inode->i_sem: don't care
 288  */
 289 int
 290 ext2_permission(struct inode *inode, int mask, struct nameidata *nd)
 291 {
 292         int mode = inode->i_mode;
 293
 294         /* Nobody gets write access to a read-only fs */
 295         if ((mask & MAY_WRITE) && (IS_RDONLY(inode) ||
 296             (nd && MNT_IS_RDONLY(nd->mnt))) &&
 297             (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
 298                 return -EROFS;
 299         /* Nobody gets write access to an immutable file */
 300         if ((mask & MAY_WRITE) && IS_IMMUTABLE(inode))
 301             return -EACCES;
 302         if (current->fsuid == inode->i_uid) {
 303                 mode >>= 6;
 304         } else if (test_opt(inode->i_sb, POSIX_ACL)) {
 305                 struct posix_acl *acl;
 306
 307                 /* The access ACL cannot grant access if the group class
 308                    permission bits don't contain all requested permissions. */
 309                 if (((mode >> 3) & mask & S_IRWXO) != mask)
 310                         goto check_groups;
 311                 acl = ext2_get_acl(inode, ACL_TYPE_ACCESS);
 312                 if (acl) {
 313                         int error = posix_acl_permission(inode, acl, mask);
 314                         posix_acl_release(acl);
 315                         if (error == -EACCES)
 316                                 goto check_capabilities;
 317                         return error;
 318                 } else
 319                         goto check_groups;
 320         } else {
 321 check_groups:
 322                 if (in_group_p(inode->i_gid))
 323                         mode >>= 3;
 324         }
 325         if ((mode & mask & S_IRWXO) == mask)
 326                 return 0;
 327
 328 check_capabilities:
 329         /* Allowed to override Discretionary Access Control? */
 330         if (!(mask & MAY_EXEC) ||
 331             (inode->i_mode & S_IXUGO) || S_ISDIR(inode->i_mode))
 332                 if (capable(CAP_DAC_OVERRIDE))
 333                         return 0;
 334         /* Read and search granted if capable(CAP_DAC_READ_SEARCH) */
 335         if (capable(CAP_DAC_READ_SEARCH) && ((mask == MAY_READ) ||
 336             (S_ISDIR(inode->i_mode) && !(mask & MAY_WRITE))))
 337                 return 0;
 338         return -EACCES;
 339 }
 340
 341 /*
 342  * Initialize the ACLs of a new inode. Called from ext2_new_inode.
 343  *
 344  * dir->i_sem: down
 345  * inode->i_sem: up (access to inode is still exclusive)
 346  */
 347 int
 348 ext2_init_acl(struct inode *inode, struct inode *dir)
 349 {
 350         struct posix_acl *acl = NULL;
 351         int error = 0;
 352
 353         if (!S_ISLNK(inode->i_mode)) {
 354                 if (test_opt(dir->i_sb, POSIX_ACL)) {
 355                         acl = ext2_get_acl(dir, ACL_TYPE_DEFAULT);
 356                         if (IS_ERR(acl))
 357                                 return PTR_ERR(acl);
 358                 }
 359                 if (!acl)
 360                         inode->i_mode &= ~current->fs->umask;
 361         }
 362         if (test_opt(inode->i_sb, POSIX_ACL) && acl) {
 363                struct posix_acl *clone;
 364                mode_t mode;
 365
 366                 if (S_ISDIR(inode->i_mode)) {
 367                         error = ext2_set_acl(inode, ACL_TYPE_DEFAULT, acl);
 368                         if (error)
 369                                 goto cleanup;
 370                 }
 371                 clone = posix_acl_clone(acl, GFP_KERNEL);
 372                 error = -ENOMEM;
 373                 if (!clone)
 374                         goto cleanup;
 375                 mode = inode->i_mode;
 376                 error = posix_acl_create_masq(clone, &mode);
 377                 if (error >= 0) {
 378                         inode->i_mode = mode;
 379                         if (error > 0) {
 380                                 /* This is an extended ACL */
 381                                 error = ext2_set_acl(inode,
 382                                                      ACL_TYPE_ACCESS, clone);
 383                         }
 384                 }
 385                 posix_acl_release(clone);
 386         }
 387 cleanup:
 388        posix_acl_release(acl);
 389        return error;
 390 }
 391
 392 /*
 393  * Does chmod for an inode that may have an Access Control List. The
 394  * inode->i_mode field must be updated to the desired value by the caller
 395  * before calling this function.
 396  * Returns 0 on success, or a negative error number.
 397  *
 398  * We change the ACL rather than storing some ACL entries in the file
 399  * mode permission bits (which would be more efficient), because that
 400  * would break once additional permissions (like  ACL_APPEND, ACL_DELETE
 401  * for directories) are added. There are no more bits available in the
 402  * file mode.
 403  *
 404  * inode->i_sem: down
 405  */
 406 int
 407 ext2_acl_chmod(struct inode *inode)
 408 {
 409         struct posix_acl *acl, *clone;
 410         int error;
 411
 412         if (!test_opt(inode->i_sb, POSIX_ACL))
 413                 return 0;
 414         if (S_ISLNK(inode->i_mode))
 415                 return -EOPNOTSUPP;
 416         acl = ext2_get_acl(inode, ACL_TYPE_ACCESS);
 417         if (IS_ERR(acl) || !acl)
 418                 return PTR_ERR(acl);
 419         clone = posix_acl_clone(acl, GFP_KERNEL);
 420         posix_acl_release(acl);
 421         if (!clone)
 422                 return -ENOMEM;
 423         error = posix_acl_chmod_masq(clone, inode->i_mode);
 424         if (!error)
 425                 error = ext2_set_acl(inode, ACL_TYPE_ACCESS, clone);
 426         posix_acl_release(clone);
 427         return error;
 428 }
 429
 430 /*
 431  * Extended attribut handlers
 432  */
 433 static size_t
 434 ext2_xattr_list_acl_access(char *list, struct inode *inode,
 435                            const char *name, int name_len)
 436 {
 437         const size_t size = sizeof(XATTR_NAME_ACL_ACCESS);
 438
 439         if (!test_opt(inode->i_sb, POSIX_ACL))
 440                 return 0;
 441         if (list)
 442                 memcpy(list, XATTR_NAME_ACL_ACCESS, size);
 443         return size;
 444 }
 445
 446 static size_t
 447 ext2_xattr_list_acl_default(char *list, struct inode *inode,
 448                             const char *name, int name_len)
 449 {
 450         const size_t size = sizeof(XATTR_NAME_ACL_DEFAULT);
 451
 452         if (!test_opt(inode->i_sb, POSIX_ACL))
 453                 return 0;
 454         if (list)
 455                 memcpy(list, XATTR_NAME_ACL_DEFAULT, size);
 456         return size;
 457 }
 458
 459 static int
 460 ext2_xattr_get_acl(struct inode *inode, int type, void *buffer, size_t size)
 461 {
 462         struct posix_acl *acl;
 463         int error;
 464
 465         if (!test_opt(inode->i_sb, POSIX_ACL))
 466                 return -EOPNOTSUPP;
 467
 468         acl = ext2_get_acl(inode, type);
 469         if (IS_ERR(acl))
 470                 return PTR_ERR(acl);
 471         if (acl == NULL)
 472                 return -ENODATA;
 473         error = posix_acl_to_xattr(acl, buffer, size);
 474         posix_acl_release(acl);
 475
 476         return error;
 477 }
 478
 479 static int
 480 ext2_xattr_get_acl_access(struct inode *inode, const char *name,
 481                           void *buffer, size_t size)
 482 {
 483         if (strcmp(name, "") != 0)
 484                 return -EINVAL;
 485         return ext2_xattr_get_acl(inode, ACL_TYPE_ACCESS, buffer, size);
 486 }
 487
 488 static int
 489 ext2_xattr_get_acl_default(struct inode *inode, const char *name,
 490                            void *buffer, size_t size)
 491 {
 492         if (strcmp(name, "") != 0)
 493                 return -EINVAL;
 494         return ext2_xattr_get_acl(inode, ACL_TYPE_DEFAULT, buffer, size);
 495 }
 496
 497 static int
 498 ext2_xattr_set_acl(struct inode *inode, int type, const void *value,
 499                    size_t size)
 500 {
 501         struct posix_acl *acl;
 502         int error;
 503
 504         if (!test_opt(inode->i_sb, POSIX_ACL))
 505                 return -EOPNOTSUPP;
 506         if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
 507                 return -EPERM;
 508
 509         if (value) {
 510                 acl = posix_acl_from_xattr(value, size);
 511                 if (IS_ERR(acl))
 512                         return PTR_ERR(acl);
 513                 else if (acl) {
 514                         error = posix_acl_valid(acl);
 515                         if (error)
 516                                 goto release_and_out;
 517                 }
 518         } else
 519                 acl = NULL;
 520
 521         error = ext2_set_acl(inode, type, acl);
 522
 523 release_and_out:
 524         posix_acl_release(acl);
 525         return error;
 526 }
 527
 528 static int
 529 ext2_xattr_set_acl_access(struct inode *inode, const char *name,
 530                           const void *value, size_t size, int flags)
 531 {
 532         if (strcmp(name, "") != 0)
 533                 return -EINVAL;
 534         return ext2_xattr_set_acl(inode, ACL_TYPE_ACCESS, value, size);
 535 }
 536
 537 static int
 538 ext2_xattr_set_acl_default(struct inode *inode, const char *name,
 539                            const void *value, size_t size, int flags)
 540 {
 541         if (strcmp(name, "") != 0)
 542                 return -EINVAL;
 543         return ext2_xattr_set_acl(inode, ACL_TYPE_DEFAULT, value, size);
 544 }
 545
 546 struct ext2_xattr_handler ext2_xattr_acl_access_handler = {
 547         .prefix = XATTR_NAME_ACL_ACCESS,
 548         .list   = ext2_xattr_list_acl_access,
 549         .get    = ext2_xattr_get_acl_access,
 550         .set    = ext2_xattr_set_acl_access,
 551 };
 552
 553 struct ext2_xattr_handler ext2_xattr_acl_default_handler = {
 554         .prefix = XATTR_NAME_ACL_DEFAULT,
 555         .list   = ext2_xattr_list_acl_default,
 556         .get    = ext2_xattr_get_acl_default,
 557         .set    = ext2_xattr_set_acl_default,
 558 };
 559
 560 void
 561 exit_ext2_acl(void)
 562 {
 563         ext2_xattr_unregister(EXT2_XATTR_INDEX_POSIX_ACL_ACCESS,
 564                               &ext2_xattr_acl_access_handler);
 565         ext2_xattr_unregister(EXT2_XATTR_INDEX_POSIX_ACL_DEFAULT,
 566                               &ext2_xattr_acl_default_handler);
 567 }
 568
 569 int __init
 570 init_ext2_acl(void)
 571 {
 572         int error;
 573
 574         error = ext2_xattr_register(EXT2_XATTR_INDEX_POSIX_ACL_ACCESS,
 575                                     &ext2_xattr_acl_access_handler);
 576         if (error)
 577                 goto fail;
 578         error = ext2_xattr_register(EXT2_XATTR_INDEX_POSIX_ACL_DEFAULT,
 579                                     &ext2_xattr_acl_default_handler);
 580         if (error)
 581                 goto fail;
 582         return 0;
 583
 584 fail:
 585         exit_ext2_acl();
 586         return error;
 587 }