fs/ext4/acl.c

   1 /*
   2  * linux/fs/ext4/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/capability.h>
  11 #include <linux/fs.h>
  12 #include "ext4_jbd2.h"
  13 #include "ext4.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 ext4_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(ext4_acl_header))
  30                  return ERR_PTR(-EINVAL);
  31         if (((ext4_acl_header *)value)->a_version !=
  32             cpu_to_le32(EXT4_ACL_VERSION))
  33                 return ERR_PTR(-EINVAL);
  34         value = (char *)value + sizeof(ext4_acl_header);
  35         count = ext4_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_NOFS);
  41         if (!acl)
  42                 return ERR_PTR(-ENOMEM);
  43         for (n = 0; n < count; n++) {
  44                 ext4_acl_entry *entry =
  45                         (ext4_acl_entry *)value;
  46                 if ((char *)value + sizeof(ext4_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
  51                 switch (acl->a_entries[n].e_tag) {
  52                 case ACL_USER_OBJ:
  53                 case ACL_GROUP_OBJ:
  54                 case ACL_MASK:
  55                 case ACL_OTHER:
  56                         value = (char *)value +
  57                                 sizeof(ext4_acl_entry_short);
  58                         acl->a_entries[n].e_id = ACL_UNDEFINED_ID;
  59                         break;
  60
  61                 case ACL_USER:
  62                 case ACL_GROUP:
  63                         value = (char *)value + sizeof(ext4_acl_entry);
  64                         if ((char *)value > end)
  65                                 goto fail;
  66                         acl->a_entries[n].e_id =
  67                                 le32_to_cpu(entry->e_id);
  68                         break;
  69
  70                 default:
  71                         goto fail;
  72                 }
  73         }
  74         if (value != end)
  75                 goto fail;
  76         return acl;
  77
  78 fail:
  79         posix_acl_release(acl);
  80         return ERR_PTR(-EINVAL);
  81 }
  82
  83 /*
  84  * Convert from in-memory to filesystem representation.
  85  */
  86 static void *
  87 ext4_acl_to_disk(const struct posix_acl *acl, size_t *size)
  88 {
  89         ext4_acl_header *ext_acl;
  90         char *e;
  91         size_t n;
  92
  93         *size = ext4_acl_size(acl->a_count);
  94         ext_acl = kmalloc(sizeof(ext4_acl_header) + acl->a_count *
  95                         sizeof(ext4_acl_entry), GFP_NOFS);
  96         if (!ext_acl)
  97                 return ERR_PTR(-ENOMEM);
  98         ext_acl->a_version = cpu_to_le32(EXT4_ACL_VERSION);
  99         e = (char *)ext_acl + sizeof(ext4_acl_header);
 100         for (n = 0; n < acl->a_count; n++) {
 101                 ext4_acl_entry *entry = (ext4_acl_entry *)e;
 102                 entry->e_tag  = cpu_to_le16(acl->a_entries[n].e_tag);
 103                 entry->e_perm = cpu_to_le16(acl->a_entries[n].e_perm);
 104                 switch (acl->a_entries[n].e_tag) {
 105                 case ACL_USER:
 106                 case ACL_GROUP:
 107                         entry->e_id = cpu_to_le32(acl->a_entries[n].e_id);
 108                         e += sizeof(ext4_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(ext4_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 /*
 130  * Inode operation get_posix_acl().
 131  *
 132  * inode->i_mutex: don't care
 133  */
 134 static struct posix_acl *
 135 ext4_get_acl(struct inode *inode, int type)
 136 {
 137         int name_index;
 138         char *value = NULL;
 139         struct posix_acl *acl;
 140         int retval;
 141
 142         if (!test_opt(inode->i_sb, POSIX_ACL))
 143                 return NULL;
 144
 145         acl = get_cached_acl(inode, type);
 146         if (acl != ACL_NOT_CACHED)
 147                 return acl;
 148
 149         switch (type) {
 150         case ACL_TYPE_ACCESS:
 151                 name_index = EXT4_XATTR_INDEX_POSIX_ACL_ACCESS;
 152                 break;
 153         case ACL_TYPE_DEFAULT:
 154                 name_index = EXT4_XATTR_INDEX_POSIX_ACL_DEFAULT;
 155                 break;
 156         default:
 157                 BUG();
 158         }
 159         retval = ext4_xattr_get(inode, name_index, "", NULL, 0);
 160         if (retval > 0) {
 161                 value = kmalloc(retval, GFP_NOFS);
 162                 if (!value)
 163                         return ERR_PTR(-ENOMEM);
 164                 retval = ext4_xattr_get(inode, name_index, "", value, retval);
 165         }
 166         if (retval > 0)
 167                 acl = ext4_acl_from_disk(value, retval);
 168         else if (retval == -ENODATA || retval == -ENOSYS)
 169                 acl = NULL;
 170         else
 171                 acl = ERR_PTR(retval);
 172         kfree(value);
 173
 174         if (!IS_ERR(acl))
 175                 set_cached_acl(inode, type, acl);
 176
 177         return acl;
 178 }
 179
 180 /*
 181  * Set the access or default ACL of an inode.
 182  *
 183  * inode->i_mutex: down unless called from ext4_new_inode
 184  */
 185 static int
 186 ext4_set_acl(handle_t *handle, struct inode *inode, int type,
 187              struct posix_acl *acl)
 188 {
 189         int name_index;
 190         void *value = NULL;
 191         size_t size = 0;
 192         int error;
 193
 194         if (S_ISLNK(inode->i_mode))
 195                 return -EOPNOTSUPP;
 196
 197         switch (type) {
 198         case ACL_TYPE_ACCESS:
 199                 name_index = EXT4_XATTR_INDEX_POSIX_ACL_ACCESS;
 200                 if (acl) {
 201                         mode_t mode = inode->i_mode;
 202                         error = posix_acl_equiv_mode(acl, &mode);
 203                         if (error < 0)
 204                                 return error;
 205                         else {
 206                                 inode->i_mode = mode;
 207                                 inode->i_ctime = ext4_current_time(inode);
 208                                 ext4_mark_inode_dirty(handle, inode);
 209                                 if (error == 0)
 210                                         acl = NULL;
 211                         }
 212                 }
 213                 break;
 214
 215         case ACL_TYPE_DEFAULT:
 216                 name_index = EXT4_XATTR_INDEX_POSIX_ACL_DEFAULT;
 217                 if (!S_ISDIR(inode->i_mode))
 218                         return acl ? -EACCES : 0;
 219                 break;
 220
 221         default:
 222                 return -EINVAL;
 223         }
 224         if (acl) {
 225                 value = ext4_acl_to_disk(acl, &size);
 226                 if (IS_ERR(value))
 227                         return (int)PTR_ERR(value);
 228         }
 229
 230         error = ext4_xattr_set_handle(handle, inode, name_index, "",
 231                                       value, size, 0);
 232
 233         kfree(value);
 234         if (!error)
 235                 set_cached_acl(inode, type, acl);
 236
 237         return error;
 238 }
 239
 240 int
 241 ext4_check_acl(struct inode *inode, int mask, unsigned int flags)
 242 {
 243         struct posix_acl *acl;
 244
 245         if (flags & IPERM_FLAG_RCU) {
 246                 if (!negative_cached_acl(inode, ACL_TYPE_ACCESS))
 247                         return -ECHILD;
 248                 return -EAGAIN;
 249         }
 250
 251         acl = ext4_get_acl(inode, ACL_TYPE_ACCESS);
 252         if (IS_ERR(acl))
 253                 return PTR_ERR(acl);
 254         if (acl) {
 255                 int error = posix_acl_permission(inode, acl, mask);
 256                 posix_acl_release(acl);
 257                 return error;
 258         }
 259
 260         return -EAGAIN;
 261 }
 262
 263 /*
 264  * Initialize the ACLs of a new inode. Called from ext4_new_inode.
 265  *
 266  * dir->i_mutex: down
 267  * inode->i_mutex: up (access to inode is still exclusive)
 268  */
 269 int
 270 ext4_init_acl(handle_t *handle, struct inode *inode, struct inode *dir)
 271 {
 272         struct posix_acl *acl = NULL;
 273         int error = 0;
 274
 275         if (!S_ISLNK(inode->i_mode)) {
 276                 if (test_opt(dir->i_sb, POSIX_ACL)) {
 277                         acl = ext4_get_acl(dir, ACL_TYPE_DEFAULT);
 278                         if (IS_ERR(acl))
 279                                 return PTR_ERR(acl);
 280                 }
 281                 if (!acl)
 282                         inode->i_mode &= ~current_umask();
 283         }
 284         if (test_opt(inode->i_sb, POSIX_ACL) && acl) {
 285                 struct posix_acl *clone;
 286                 mode_t mode;
 287
 288                 if (S_ISDIR(inode->i_mode)) {
 289                         error = ext4_set_acl(handle, inode,
 290                                              ACL_TYPE_DEFAULT, acl);
 291                         if (error)
 292                                 goto cleanup;
 293                 }
 294                 clone = posix_acl_clone(acl, GFP_NOFS);
 295                 error = -ENOMEM;
 296                 if (!clone)
 297                         goto cleanup;
 298
 299                 mode = inode->i_mode;
 300                 error = posix_acl_create_masq(clone, &mode);
 301                 if (error >= 0) {
 302                         inode->i_mode = mode;
 303                         if (error > 0) {
 304                                 /* This is an extended ACL */
 305                                 error = ext4_set_acl(handle, inode,
 306                                                      ACL_TYPE_ACCESS, clone);
 307                         }
 308                 }
 309                 posix_acl_release(clone);
 310         }
 311 cleanup:
 312         posix_acl_release(acl);
 313         return error;
 314 }
 315
 316 /*
 317  * Does chmod for an inode that may have an Access Control List. The
 318  * inode->i_mode field must be updated to the desired value by the caller
 319  * before calling this function.
 320  * Returns 0 on success, or a negative error number.
 321  *
 322  * We change the ACL rather than storing some ACL entries in the file
 323  * mode permission bits (which would be more efficient), because that
 324  * would break once additional permissions (like  ACL_APPEND, ACL_DELETE
 325  * for directories) are added. There are no more bits available in the
 326  * file mode.
 327  *
 328  * inode->i_mutex: down
 329  */
 330 int
 331 ext4_acl_chmod(struct inode *inode)
 332 {
 333         struct posix_acl *acl, *clone;
 334         int error;
 335
 336         if (S_ISLNK(inode->i_mode))
 337                 return -EOPNOTSUPP;
 338         if (!test_opt(inode->i_sb, POSIX_ACL))
 339                 return 0;
 340         acl = ext4_get_acl(inode, ACL_TYPE_ACCESS);
 341         if (IS_ERR(acl) || !acl)
 342                 return PTR_ERR(acl);
 343         clone = posix_acl_clone(acl, GFP_KERNEL);
 344         posix_acl_release(acl);
 345         if (!clone)
 346                 return -ENOMEM;
 347         error = posix_acl_chmod_masq(clone, inode->i_mode);
 348         if (!error) {
 349                 handle_t *handle;
 350                 int retries = 0;
 351
 352         retry:
 353                 handle = ext4_journal_start(inode,
 354                                 EXT4_DATA_TRANS_BLOCKS(inode->i_sb));
 355                 if (IS_ERR(handle)) {
 356                         error = PTR_ERR(handle);
 357                         ext4_std_error(inode->i_sb, error);
 358                         goto out;
 359                 }
 360                 error = ext4_set_acl(handle, inode, ACL_TYPE_ACCESS, clone);
 361                 ext4_journal_stop(handle);
 362                 if (error == -ENOSPC &&
 363                     ext4_should_retry_alloc(inode->i_sb, &retries))
 364                         goto retry;
 365         }
 366 out:
 367         posix_acl_release(clone);
 368         return error;
 369 }
 370
 371 /*
 372  * Extended attribute handlers
 373  */
 374 static size_t
 375 ext4_xattr_list_acl_access(struct dentry *dentry, char *list, size_t list_len,
 376                            const char *name, size_t name_len, int type)
 377 {
 378         const size_t size = sizeof(POSIX_ACL_XATTR_ACCESS);
 379
 380         if (!test_opt(dentry->d_sb, POSIX_ACL))
 381                 return 0;
 382         if (list && size <= list_len)
 383                 memcpy(list, POSIX_ACL_XATTR_ACCESS, size);
 384         return size;
 385 }
 386
 387 static size_t
 388 ext4_xattr_list_acl_default(struct dentry *dentry, char *list, size_t list_len,
 389                             const char *name, size_t name_len, int type)
 390 {
 391         const size_t size = sizeof(POSIX_ACL_XATTR_DEFAULT);
 392
 393         if (!test_opt(dentry->d_sb, POSIX_ACL))
 394                 return 0;
 395         if (list && size <= list_len)
 396                 memcpy(list, POSIX_ACL_XATTR_DEFAULT, size);
 397         return size;
 398 }
 399
 400 static int
 401 ext4_xattr_get_acl(struct dentry *dentry, const char *name, void *buffer,
 402                    size_t size, int type)
 403 {
 404         struct posix_acl *acl;
 405         int error;
 406
 407         if (strcmp(name, "") != 0)
 408                 return -EINVAL;
 409         if (!test_opt(dentry->d_sb, POSIX_ACL))
 410                 return -EOPNOTSUPP;
 411
 412         acl = ext4_get_acl(dentry->d_inode, type);
 413         if (IS_ERR(acl))
 414                 return PTR_ERR(acl);
 415         if (acl == NULL)
 416                 return -ENODATA;
 417         error = posix_acl_to_xattr(acl, buffer, size);
 418         posix_acl_release(acl);
 419
 420         return error;
 421 }
 422
 423 static int
 424 ext4_xattr_set_acl(struct dentry *dentry, const char *name, const void *value,
 425                    size_t size, int flags, int type)
 426 {
 427         struct inode *inode = dentry->d_inode;
 428         handle_t *handle;
 429         struct posix_acl *acl;
 430         int error, retries = 0;
 431
 432         if (strcmp(name, "") != 0)
 433                 return -EINVAL;
 434         if (!test_opt(inode->i_sb, POSIX_ACL))
 435                 return -EOPNOTSUPP;
 436         if (!inode_owner_or_capable(inode))
 437                 return -EPERM;
 438
 439         if (value) {
 440                 acl = posix_acl_from_xattr(value, size);
 441                 if (IS_ERR(acl))
 442                         return PTR_ERR(acl);
 443                 else if (acl) {
 444                         error = posix_acl_valid(acl);
 445                         if (error)
 446                                 goto release_and_out;
 447                 }
 448         } else
 449                 acl = NULL;
 450
 451 retry:
 452         handle = ext4_journal_start(inode, EXT4_DATA_TRANS_BLOCKS(inode->i_sb));
 453         if (IS_ERR(handle))
 454                 return PTR_ERR(handle);
 455         error = ext4_set_acl(handle, inode, type, acl);
 456         ext4_journal_stop(handle);
 457         if (error == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
 458                 goto retry;
 459
 460 release_and_out:
 461         posix_acl_release(acl);
 462         return error;
 463 }
 464
 465 const struct xattr_handler ext4_xattr_acl_access_handler = {
 466         .prefix = POSIX_ACL_XATTR_ACCESS,
 467         .flags  = ACL_TYPE_ACCESS,
 468         .list   = ext4_xattr_list_acl_access,
 469         .get    = ext4_xattr_get_acl,
 470         .set    = ext4_xattr_set_acl,
 471 };
 472
 473 const struct xattr_handler ext4_xattr_acl_default_handler = {
 474         .prefix = POSIX_ACL_XATTR_DEFAULT,
 475         .flags  = ACL_TYPE_DEFAULT,
 476         .list   = ext4_xattr_list_acl_default,
 477         .get    = ext4_xattr_get_acl,
 478         .set    = ext4_xattr_set_acl,
 479 };