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 <linux/vs_base.h>
  13 #include "ext2.h"
  14 #include "xattr.h"
  15 #include "acl.h"
  16
  17 /*
  18  * Convert from filesystem to in-memory representation.
  19  */
  20 static struct posix_acl *
  21 ext2_acl_from_disk(const void *value, size_t size)
  22 {
  23         const char *end = (char *)value + size;
  24         int n, count;
  25         struct posix_acl *acl;
  26
  27         if (!value)
  28                 return NULL;
  29         if (size < sizeof(ext2_acl_header))
  30                  return ERR_PTR(-EINVAL);
  31         if (((ext2_acl_header *)value)->a_version !=
  32             cpu_to_le32(EXT2_ACL_VERSION))
  33                 return ERR_PTR(-EINVAL);
  34         value = (char *)value + sizeof(ext2_acl_header);
  35         count = ext2_acl_count(size);
  36         if (count < 0)
  37                 return ERR_PTR(-EINVAL);
  38         if (count == 0)
  39                 return NULL;
  40         acl = posix_acl_alloc(count, GFP_KERNEL);
  41         if (!acl)
  42                 return ERR_PTR(-ENOMEM);
  43         for (n=0; n < count; n++) {
  44                 ext2_acl_entry *entry =
  45                         (ext2_acl_entry *)value;
  46                 if ((char *)value + sizeof(ext2_acl_entry_short) > end)
  47                         goto fail;
  48                 acl->a_entries[n].e_tag  = le16_to_cpu(entry->e_tag);
  49                 acl->a_entries[n].e_perm = le16_to_cpu(entry->e_perm);
  50                 switch(acl->a_entries[n].e_tag) {
  51                         case ACL_USER_OBJ:
  52                         case ACL_GROUP_OBJ:
  53                         case ACL_MASK:
  54                         case ACL_OTHER:
  55                                 value = (char *)value +
  56                                         sizeof(ext2_acl_entry_short);
  57                                 acl->a_entries[n].e_id = ACL_UNDEFINED_ID;
  58                                 break;
  59
  60                         case ACL_USER:
  61                         case ACL_GROUP:
  62                                 value = (char *)value + sizeof(ext2_acl_entry);
  63                                 if ((char *)value > end)
  64                                         goto fail;
  65                                 acl->a_entries[n].e_id =
  66                                         le32_to_cpu(entry->e_id);
  67                                 break;
  68
  69                         default:
  70                                 goto fail;
  71                 }
  72         }
  73         if (value != end)
  74                 goto fail;
  75         return acl;
  76
  77 fail:
  78         posix_acl_release(acl);
  79         return ERR_PTR(-EINVAL);
  80 }
  81
  82 /*
  83  * Convert from in-memory to filesystem representation.
  84  */
  85 static void *
  86 ext2_acl_to_disk(const struct posix_acl *acl, size_t *size)
  87 {
  88         ext2_acl_header *ext_acl;
  89         char *e;
  90         size_t n;
  91
  92         *size = ext2_acl_size(acl->a_count);
  93         ext_acl = (ext2_acl_header *)kmalloc(sizeof(ext2_acl_header) +
  94                 acl->a_count * sizeof(ext2_acl_entry), GFP_KERNEL);
  95         if (!ext_acl)
  96                 return ERR_PTR(-ENOMEM);
  97         ext_acl->a_version = cpu_to_le32(EXT2_ACL_VERSION);
  98         e = (char *)ext_acl + sizeof(ext2_acl_header);
  99         for (n=0; n < acl->a_count; n++) {
 100                 ext2_acl_entry *entry = (ext2_acl_entry *)e;
 101                 entry->e_tag  = cpu_to_le16(acl->a_entries[n].e_tag);
 102                 entry->e_perm = cpu_to_le16(acl->a_entries[n].e_perm);
 103                 switch(acl->a_entries[n].e_tag) {
 104                         case ACL_USER:
 105                         case ACL_GROUP:
 106                                 entry->e_id =
 107                                         cpu_to_le32(acl->a_entries[n].e_id);
 108                                 e += sizeof(ext2_acl_entry);
 109                                 break;
 110
 111                         case ACL_USER_OBJ:
 112                         case ACL_GROUP_OBJ:
 113                         case ACL_MASK:
 114                         case ACL_OTHER:
 115                                 e += sizeof(ext2_acl_entry_short);
 116                                 break;
 117
 118                         default:
 119                                 goto fail;
 120                 }
 121         }
 122         return (char *)ext_acl;
 123
 124 fail:
 125         kfree(ext_acl);
 126         return ERR_PTR(-EINVAL);
 127 }
 128
 129 static inline struct posix_acl *
 130 ext2_iget_acl(struct inode *inode, struct posix_acl **i_acl)
 131 {
 132         struct posix_acl *acl = EXT2_ACL_NOT_CACHED;
 133
 134         spin_lock(&inode->i_lock);
 135         if (*i_acl != EXT2_ACL_NOT_CACHED)
 136                 acl = posix_acl_dup(*i_acl);
 137         spin_unlock(&inode->i_lock);
 138
 139         return acl;
 140 }
 141
 142 static inline void
 143 ext2_iset_acl(struct inode *inode, struct posix_acl **i_acl,
 144                    struct posix_acl *acl)
 145 {
 146         spin_lock(&inode->i_lock);
 147         if (*i_acl != EXT2_ACL_NOT_CACHED)
 148                 posix_acl_release(*i_acl);
 149         *i_acl = posix_acl_dup(acl);
 150         spin_unlock(&inode->i_lock);
 151 }
 152
 153 /*
 154  * inode->i_sem: don't care
 155  */
 156 static struct posix_acl *
 157 ext2_get_acl(struct inode *inode, int type)
 158 {
 159         struct ext2_inode_info *ei = EXT2_I(inode);
 160         int name_index;
 161         char *value = NULL;
 162         struct posix_acl *acl;
 163         int retval;
 164
 165         if (!test_opt(inode->i_sb, POSIX_ACL))
 166                 return NULL;
 167
 168         switch(type) {
 169                 case ACL_TYPE_ACCESS:
 170                         acl = ext2_iget_acl(inode, &ei->i_acl);
 171                         if (acl != EXT2_ACL_NOT_CACHED)
 172                                 return acl;
 173                         name_index = EXT2_XATTR_INDEX_POSIX_ACL_ACCESS;
 174                         break;
 175
 176                 case ACL_TYPE_DEFAULT:
 177                         acl = ext2_iget_acl(inode, &ei->i_default_acl);
 178                         if (acl != EXT2_ACL_NOT_CACHED)
 179                                 return acl;
 180                         name_index = EXT2_XATTR_INDEX_POSIX_ACL_DEFAULT;
 181                         break;
 182
 183                 default:
 184                         return ERR_PTR(-EINVAL);
 185         }
 186         retval = ext2_xattr_get(inode, name_index, "", NULL, 0);
 187         if (retval > 0) {
 188                 value = kmalloc(retval, GFP_KERNEL);
 189                 if (!value)
 190                         return ERR_PTR(-ENOMEM);
 191                 retval = ext2_xattr_get(inode, name_index, "", value, retval);
 192         }
 193         if (retval > 0)
 194                 acl = ext2_acl_from_disk(value, retval);
 195         else if (retval == -ENODATA || retval == -ENOSYS)
 196                 acl = NULL;
 197         else
 198                 acl = ERR_PTR(retval);
 199         if (value)
 200                 kfree(value);
 201
 202         if (!IS_ERR(acl)) {
 203                 switch(type) {
 204                         case ACL_TYPE_ACCESS:
 205                                 ext2_iset_acl(inode, &ei->i_acl, acl);
 206                                 break;
 207
 208                         case ACL_TYPE_DEFAULT:
 209                                 ext2_iset_acl(inode, &ei->i_default_acl, acl);
 210                                 break;
 211                 }
 212         }
 213         return acl;
 214 }
 215
 216 /*
 217  * inode->i_sem: down
 218  */
 219 static int
 220 ext2_set_acl(struct inode *inode, int type, struct posix_acl *acl)
 221 {
 222         struct ext2_inode_info *ei = EXT2_I(inode);
 223         int name_index;
 224         void *value = NULL;
 225         size_t size;
 226         int error;
 227
 228         if (S_ISLNK(inode->i_mode))
 229                 return -EOPNOTSUPP;
 230         if (!test_opt(inode->i_sb, POSIX_ACL))
 231                 return 0;
 232
 233         switch(type) {
 234                 case ACL_TYPE_ACCESS:
 235                         name_index = EXT2_XATTR_INDEX_POSIX_ACL_ACCESS;
 236                         if (acl) {
 237                                 mode_t mode = inode->i_mode;
 238                                 error = posix_acl_equiv_mode(acl, &mode);
 239                                 if (error < 0)
 240                                         return error;
 241                                 else {
 242                                         inode->i_mode = mode;
 243                                         mark_inode_dirty(inode);
 244                                         if (error == 0)
 245                                                 acl = NULL;
 246                                 }
 247                         }
 248                         break;
 249
 250                 case ACL_TYPE_DEFAULT:
 251                         name_index = EXT2_XATTR_INDEX_POSIX_ACL_DEFAULT;
 252                         if (!S_ISDIR(inode->i_mode))
 253                                 return acl ? -EACCES : 0;
 254                         break;
 255
 256                 default:
 257                         return -EINVAL;
 258         }
 259         if (acl) {
 260                 if (acl->a_count > EXT2_ACL_MAX_ENTRIES)
 261                         return -EINVAL;
 262                 value = ext2_acl_to_disk(acl, &size);
 263                 if (IS_ERR(value))
 264                         return (int)PTR_ERR(value);
 265         }
 266
 267         error = ext2_xattr_set(inode, name_index, "", value, size, 0);
 268
 269         if (value)
 270                 kfree(value);
 271         if (!error) {
 272                 switch(type) {
 273                         case ACL_TYPE_ACCESS:
 274                                 ext2_iset_acl(inode, &ei->i_acl, acl);
 275                                 break;
 276
 277                         case ACL_TYPE_DEFAULT:
 278                                 ext2_iset_acl(inode, &ei->i_default_acl, acl);
 279                                 break;
 280                 }
 281         }
 282         return error;
 283 }
 284
 285 /*
 286  * Inode operation permission().
 287  *
 288  * inode->i_sem: don't care
 289  */
 290 int
 291 ext2_permission(struct inode *inode, int mask, struct nameidata *nd)
 292 {
 293         int mode = inode->i_mode;
 294
 295         /* Prevent vservers from escaping chroot() barriers */
 296         if (IS_BARRIER(inode) && !vx_check(0, VX_ADMIN))
 297                 return -EACCES;
 298         /* Nobody gets write access to a read-only fs */
 299         if ((mask & MAY_WRITE) && (IS_RDONLY(inode) ||
 300             (nd && MNT_IS_RDONLY(nd->mnt))) &&
 301             (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
 302                 return -EROFS;
 303         /* Nobody gets write access to an immutable file */
 304         if ((mask & MAY_WRITE) && IS_IMMUTABLE(inode))
 305             return -EACCES;
 306         if (current->fsuid == inode->i_uid) {
 307                 mode >>= 6;
 308         } else if (test_opt(inode->i_sb, POSIX_ACL)) {
 309                 struct posix_acl *acl;
 310
 311                 /* The access ACL cannot grant access if the group class
 312                    permission bits don't contain all requested permissions. */
 313                 if (((mode >> 3) & mask & S_IRWXO) != mask)
 314                         goto check_groups;
 315                 acl = ext2_get_acl(inode, ACL_TYPE_ACCESS);
 316                 if (acl) {
 317                         int error = posix_acl_permission(inode, acl, mask);
 318                         posix_acl_release(acl);
 319                         if (error == -EACCES)
 320                                 goto check_capabilities;
 321                         return error;
 322                 } else
 323                         goto check_groups;
 324         } else {
 325 check_groups:
 326                 if (in_group_p(inode->i_gid))
 327                         mode >>= 3;
 328         }
 329         if ((mode & mask & S_IRWXO) == mask)
 330                 return 0;
 331
 332 check_capabilities:
 333         /* Allowed to override Discretionary Access Control? */
 334         if (!(mask & MAY_EXEC) ||
 335             (inode->i_mode & S_IXUGO) || S_ISDIR(inode->i_mode))
 336                 if (capable(CAP_DAC_OVERRIDE))
 337                         return 0;
 338         /* Read and search granted if capable(CAP_DAC_READ_SEARCH) */
 339         if (capable(CAP_DAC_READ_SEARCH) && ((mask == MAY_READ) ||
 340             (S_ISDIR(inode->i_mode) && !(mask & MAY_WRITE))))
 341                 return 0;
 342         return -EACCES;
 343 }
 344
 345 /*
 346  * Initialize the ACLs of a new inode. Called from ext2_new_inode.
 347  *
 348  * dir->i_sem: down
 349  * inode->i_sem: up (access to inode is still exclusive)
 350  */
 351 int
 352 ext2_init_acl(struct inode *inode, struct inode *dir)
 353 {
 354         struct posix_acl *acl = NULL;
 355         int error = 0;
 356
 357         if (!S_ISLNK(inode->i_mode)) {
 358                 if (test_opt(dir->i_sb, POSIX_ACL)) {
 359                         acl = ext2_get_acl(dir, ACL_TYPE_DEFAULT);
 360                         if (IS_ERR(acl))
 361                                 return PTR_ERR(acl);
 362                 }
 363                 if (!acl)
 364                         inode->i_mode &= ~current->fs->umask;
 365         }
 366         if (test_opt(inode->i_sb, POSIX_ACL) && acl) {
 367                struct posix_acl *clone;
 368                mode_t mode;
 369
 370                 if (S_ISDIR(inode->i_mode)) {
 371                         error = ext2_set_acl(inode, ACL_TYPE_DEFAULT, acl);
 372                         if (error)
 373                                 goto cleanup;
 374                 }
 375                 clone = posix_acl_clone(acl, GFP_KERNEL);
 376                 error = -ENOMEM;
 377                 if (!clone)
 378                         goto cleanup;
 379                 mode = inode->i_mode;
 380                 error = posix_acl_create_masq(clone, &mode);
 381                 if (error >= 0) {
 382                         inode->i_mode = mode;
 383                         if (error > 0) {
 384                                 /* This is an extended ACL */
 385                                 error = ext2_set_acl(inode,
 386                                                      ACL_TYPE_ACCESS, clone);
 387                         }
 388                 }
 389                 posix_acl_release(clone);
 390         }
 391 cleanup:
 392        posix_acl_release(acl);
 393        return error;
 394 }
 395
 396 /*
 397  * Does chmod for an inode that may have an Access Control List. The
 398  * inode->i_mode field must be updated to the desired value by the caller
 399  * before calling this function.
 400  * Returns 0 on success, or a negative error number.
 401  *
 402  * We change the ACL rather than storing some ACL entries in the file
 403  * mode permission bits (which would be more efficient), because that
 404  * would break once additional permissions (like  ACL_APPEND, ACL_DELETE
 405  * for directories) are added. There are no more bits available in the
 406  * file mode.
 407  *
 408  * inode->i_sem: down
 409  */
 410 int
 411 ext2_acl_chmod(struct inode *inode)
 412 {
 413         struct posix_acl *acl, *clone;
 414         int error;
 415
 416         if (!test_opt(inode->i_sb, POSIX_ACL))
 417                 return 0;
 418         if (S_ISLNK(inode->i_mode))
 419                 return -EOPNOTSUPP;
 420         acl = ext2_get_acl(inode, ACL_TYPE_ACCESS);
 421         if (IS_ERR(acl) || !acl)
 422                 return PTR_ERR(acl);
 423         clone = posix_acl_clone(acl, GFP_KERNEL);
 424         posix_acl_release(acl);
 425         if (!clone)
 426                 return -ENOMEM;
 427         error = posix_acl_chmod_masq(clone, inode->i_mode);
 428         if (!error)
 429                 error = ext2_set_acl(inode, ACL_TYPE_ACCESS, clone);
 430         posix_acl_release(clone);
 431         return error;
 432 }
 433
 434 /*
 435  * Extended attribut handlers
 436  */
 437 static size_t
 438 ext2_xattr_list_acl_access(char *list, struct inode *inode,
 439                            const char *name, int name_len)
 440 {
 441         const size_t size = sizeof(XATTR_NAME_ACL_ACCESS);
 442
 443         if (!test_opt(inode->i_sb, POSIX_ACL))
 444                 return 0;
 445         if (list)
 446                 memcpy(list, XATTR_NAME_ACL_ACCESS, size);
 447         return size;
 448 }
 449
 450 static size_t
 451 ext2_xattr_list_acl_default(char *list, struct inode *inode,
 452                             const char *name, int name_len)
 453 {
 454         const size_t size = sizeof(XATTR_NAME_ACL_DEFAULT);
 455
 456         if (!test_opt(inode->i_sb, POSIX_ACL))
 457                 return 0;
 458         if (list)
 459                 memcpy(list, XATTR_NAME_ACL_DEFAULT, size);
 460         return size;
 461 }
 462
 463 static int
 464 ext2_xattr_get_acl(struct inode *inode, int type, void *buffer, size_t size)
 465 {
 466         struct posix_acl *acl;
 467         int error;
 468
 469         if (!test_opt(inode->i_sb, POSIX_ACL))
 470                 return -EOPNOTSUPP;
 471
 472         acl = ext2_get_acl(inode, type);
 473         if (IS_ERR(acl))
 474                 return PTR_ERR(acl);
 475         if (acl == NULL)
 476                 return -ENODATA;
 477         error = posix_acl_to_xattr(acl, buffer, size);
 478         posix_acl_release(acl);
 479
 480         return error;
 481 }
 482
 483 static int
 484 ext2_xattr_get_acl_access(struct inode *inode, const char *name,
 485                           void *buffer, size_t size)
 486 {
 487         if (strcmp(name, "") != 0)
 488                 return -EINVAL;
 489         return ext2_xattr_get_acl(inode, ACL_TYPE_ACCESS, buffer, size);
 490 }
 491
 492 static int
 493 ext2_xattr_get_acl_default(struct inode *inode, const char *name,
 494                            void *buffer, size_t size)
 495 {
 496         if (strcmp(name, "") != 0)
 497                 return -EINVAL;
 498         return ext2_xattr_get_acl(inode, ACL_TYPE_DEFAULT, buffer, size);
 499 }
 500
 501 static int
 502 ext2_xattr_set_acl(struct inode *inode, int type, const void *value,
 503                    size_t size)
 504 {
 505         struct posix_acl *acl;
 506         int error;
 507
 508         if (!test_opt(inode->i_sb, POSIX_ACL))
 509                 return -EOPNOTSUPP;
 510         if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
 511                 return -EPERM;
 512
 513         if (value) {
 514                 acl = posix_acl_from_xattr(value, size);
 515                 if (IS_ERR(acl))
 516                         return PTR_ERR(acl);
 517                 else if (acl) {
 518                         error = posix_acl_valid(acl);
 519                         if (error)
 520                                 goto release_and_out;
 521                 }
 522         } else
 523                 acl = NULL;
 524
 525         error = ext2_set_acl(inode, type, acl);
 526
 527 release_and_out:
 528         posix_acl_release(acl);
 529         return error;
 530 }
 531
 532 static int
 533 ext2_xattr_set_acl_access(struct inode *inode, const char *name,
 534                           const void *value, size_t size, int flags)
 535 {
 536         if (strcmp(name, "") != 0)
 537                 return -EINVAL;
 538         return ext2_xattr_set_acl(inode, ACL_TYPE_ACCESS, value, size);
 539 }
 540
 541 static int
 542 ext2_xattr_set_acl_default(struct inode *inode, const char *name,
 543                            const void *value, size_t size, int flags)
 544 {
 545         if (strcmp(name, "") != 0)
 546                 return -EINVAL;
 547         return ext2_xattr_set_acl(inode, ACL_TYPE_DEFAULT, value, size);
 548 }
 549
 550 struct ext2_xattr_handler ext2_xattr_acl_access_handler = {
 551         .prefix = XATTR_NAME_ACL_ACCESS,
 552         .list   = ext2_xattr_list_acl_access,
 553         .get    = ext2_xattr_get_acl_access,
 554         .set    = ext2_xattr_set_acl_access,
 555 };
 556
 557 struct ext2_xattr_handler ext2_xattr_acl_default_handler = {
 558         .prefix = XATTR_NAME_ACL_DEFAULT,
 559         .list   = ext2_xattr_list_acl_default,
 560         .get    = ext2_xattr_get_acl_default,
 561         .set    = ext2_xattr_set_acl_default,
 562 };
 563
 564 void
 565 exit_ext2_acl(void)
 566 {
 567         ext2_xattr_unregister(EXT2_XATTR_INDEX_POSIX_ACL_ACCESS,
 568                               &ext2_xattr_acl_access_handler);
 569         ext2_xattr_unregister(EXT2_XATTR_INDEX_POSIX_ACL_DEFAULT,
 570                               &ext2_xattr_acl_default_handler);
 571 }
 572
 573 int __init
 574 init_ext2_acl(void)
 575 {
 576         int error;
 577
 578         error = ext2_xattr_register(EXT2_XATTR_INDEX_POSIX_ACL_ACCESS,
 579                                     &ext2_xattr_acl_access_handler);
 580         if (error)
 581                 goto fail;
 582         error = ext2_xattr_register(EXT2_XATTR_INDEX_POSIX_ACL_DEFAULT,
 583                                     &ext2_xattr_acl_default_handler);
 584         if (error)
 585                 goto fail;
 586         return 0;
 587
 588 fail:
 589         exit_ext2_acl();
 590         return error;
 591 }