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