linux/fs/ext4/acl.c
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   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 */
  20static struct posix_acl *
  21ext4_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
  78fail:
  79        posix_acl_release(acl);
  80        return ERR_PTR(-EINVAL);
  81}
  82
  83/*
  84 * Convert from in-memory to filesystem representation.
  85 */
  86static void *
  87ext4_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
 124fail:
 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 */
 134struct posix_acl *
 135ext4_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 */
 185static int
 186ext4_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                        error = posix_acl_equiv_mode(acl, &inode->i_mode);
 202                        if (error < 0)
 203                                return error;
 204                        else {
 205                                inode->i_ctime = ext4_current_time(inode);
 206                                ext4_mark_inode_dirty(handle, inode);
 207                                if (error == 0)
 208                                        acl = NULL;
 209                        }
 210                }
 211                break;
 212
 213        case ACL_TYPE_DEFAULT:
 214                name_index = EXT4_XATTR_INDEX_POSIX_ACL_DEFAULT;
 215                if (!S_ISDIR(inode->i_mode))
 216                        return acl ? -EACCES : 0;
 217                break;
 218
 219        default:
 220                return -EINVAL;
 221        }
 222        if (acl) {
 223                value = ext4_acl_to_disk(acl, &size);
 224                if (IS_ERR(value))
 225                        return (int)PTR_ERR(value);
 226        }
 227
 228        error = ext4_xattr_set_handle(handle, inode, name_index, "",
 229                                      value, size, 0);
 230
 231        kfree(value);
 232        if (!error)
 233                set_cached_acl(inode, type, acl);
 234
 235        return error;
 236}
 237
 238/*
 239 * Initialize the ACLs of a new inode. Called from ext4_new_inode.
 240 *
 241 * dir->i_mutex: down
 242 * inode->i_mutex: up (access to inode is still exclusive)
 243 */
 244int
 245ext4_init_acl(handle_t *handle, struct inode *inode, struct inode *dir)
 246{
 247        struct posix_acl *acl = NULL;
 248        int error = 0;
 249
 250        if (!S_ISLNK(inode->i_mode)) {
 251                if (test_opt(dir->i_sb, POSIX_ACL)) {
 252                        acl = ext4_get_acl(dir, ACL_TYPE_DEFAULT);
 253                        if (IS_ERR(acl))
 254                                return PTR_ERR(acl);
 255                }
 256                if (!acl)
 257                        inode->i_mode &= ~current_umask();
 258        }
 259        if (test_opt(inode->i_sb, POSIX_ACL) && acl) {
 260                if (S_ISDIR(inode->i_mode)) {
 261                        error = ext4_set_acl(handle, inode,
 262                                             ACL_TYPE_DEFAULT, acl);
 263                        if (error)
 264                                goto cleanup;
 265                }
 266                error = posix_acl_create(&acl, GFP_NOFS, &inode->i_mode);
 267                if (error < 0)
 268                        return error;
 269
 270                if (error > 0) {
 271                        /* This is an extended ACL */
 272                        error = ext4_set_acl(handle, inode, ACL_TYPE_ACCESS, acl);
 273                }
 274        }
 275cleanup:
 276        posix_acl_release(acl);
 277        return error;
 278}
 279
 280/*
 281 * Does chmod for an inode that may have an Access Control List. The
 282 * inode->i_mode field must be updated to the desired value by the caller
 283 * before calling this function.
 284 * Returns 0 on success, or a negative error number.
 285 *
 286 * We change the ACL rather than storing some ACL entries in the file
 287 * mode permission bits (which would be more efficient), because that
 288 * would break once additional permissions (like  ACL_APPEND, ACL_DELETE
 289 * for directories) are added. There are no more bits available in the
 290 * file mode.
 291 *
 292 * inode->i_mutex: down
 293 */
 294int
 295ext4_acl_chmod(struct inode *inode)
 296{
 297        struct posix_acl *acl;
 298        handle_t *handle;
 299        int retries = 0;
 300        int error;
 301
 302
 303        if (S_ISLNK(inode->i_mode))
 304                return -EOPNOTSUPP;
 305        if (!test_opt(inode->i_sb, POSIX_ACL))
 306                return 0;
 307        acl = ext4_get_acl(inode, ACL_TYPE_ACCESS);
 308        if (IS_ERR(acl) || !acl)
 309                return PTR_ERR(acl);
 310        error = posix_acl_chmod(&acl, GFP_KERNEL, inode->i_mode);
 311        if (error)
 312                return error;
 313retry:
 314        handle = ext4_journal_start(inode,
 315                        EXT4_DATA_TRANS_BLOCKS(inode->i_sb));
 316        if (IS_ERR(handle)) {
 317                error = PTR_ERR(handle);
 318                ext4_std_error(inode->i_sb, error);
 319                goto out;
 320        }
 321        error = ext4_set_acl(handle, inode, ACL_TYPE_ACCESS, acl);
 322        ext4_journal_stop(handle);
 323        if (error == -ENOSPC &&
 324            ext4_should_retry_alloc(inode->i_sb, &retries))
 325                goto retry;
 326out:
 327        posix_acl_release(acl);
 328        return error;
 329}
 330
 331/*
 332 * Extended attribute handlers
 333 */
 334static size_t
 335ext4_xattr_list_acl_access(struct dentry *dentry, char *list, size_t list_len,
 336                           const char *name, size_t name_len, int type)
 337{
 338        const size_t size = sizeof(POSIX_ACL_XATTR_ACCESS);
 339
 340        if (!test_opt(dentry->d_sb, POSIX_ACL))
 341                return 0;
 342        if (list && size <= list_len)
 343                memcpy(list, POSIX_ACL_XATTR_ACCESS, size);
 344        return size;
 345}
 346
 347static size_t
 348ext4_xattr_list_acl_default(struct dentry *dentry, char *list, size_t list_len,
 349                            const char *name, size_t name_len, int type)
 350{
 351        const size_t size = sizeof(POSIX_ACL_XATTR_DEFAULT);
 352
 353        if (!test_opt(dentry->d_sb, POSIX_ACL))
 354                return 0;
 355        if (list && size <= list_len)
 356                memcpy(list, POSIX_ACL_XATTR_DEFAULT, size);
 357        return size;
 358}
 359
 360static int
 361ext4_xattr_get_acl(struct dentry *dentry, const char *name, void *buffer,
 362                   size_t size, int type)
 363{
 364        struct posix_acl *acl;
 365        int error;
 366
 367        if (strcmp(name, "") != 0)
 368                return -EINVAL;
 369        if (!test_opt(dentry->d_sb, POSIX_ACL))
 370                return -EOPNOTSUPP;
 371
 372        acl = ext4_get_acl(dentry->d_inode, type);
 373        if (IS_ERR(acl))
 374                return PTR_ERR(acl);
 375        if (acl == NULL)
 376                return -ENODATA;
 377        error = posix_acl_to_xattr(acl, buffer, size);
 378        posix_acl_release(acl);
 379
 380        return error;
 381}
 382
 383static int
 384ext4_xattr_set_acl(struct dentry *dentry, const char *name, const void *value,
 385                   size_t size, int flags, int type)
 386{
 387        struct inode *inode = dentry->d_inode;
 388        handle_t *handle;
 389        struct posix_acl *acl;
 390        int error, retries = 0;
 391
 392        if (strcmp(name, "") != 0)
 393                return -EINVAL;
 394        if (!test_opt(inode->i_sb, POSIX_ACL))
 395                return -EOPNOTSUPP;
 396        if (!inode_owner_or_capable(inode))
 397                return -EPERM;
 398
 399        if (value) {
 400                acl = posix_acl_from_xattr(value, size);
 401                if (IS_ERR(acl))
 402                        return PTR_ERR(acl);
 403                else if (acl) {
 404                        error = posix_acl_valid(acl);
 405                        if (error)
 406                                goto release_and_out;
 407                }
 408        } else
 409                acl = NULL;
 410
 411retry:
 412        handle = ext4_journal_start(inode, EXT4_DATA_TRANS_BLOCKS(inode->i_sb));
 413        if (IS_ERR(handle))
 414                return PTR_ERR(handle);
 415        error = ext4_set_acl(handle, inode, type, acl);
 416        ext4_journal_stop(handle);
 417        if (error == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
 418                goto retry;
 419
 420release_and_out:
 421        posix_acl_release(acl);
 422        return error;
 423}
 424
 425const struct xattr_handler ext4_xattr_acl_access_handler = {
 426        .prefix = POSIX_ACL_XATTR_ACCESS,
 427        .flags  = ACL_TYPE_ACCESS,
 428        .list   = ext4_xattr_list_acl_access,
 429        .get    = ext4_xattr_get_acl,
 430        .set    = ext4_xattr_set_acl,
 431};
 432
 433const struct xattr_handler ext4_xattr_acl_default_handler = {
 434        .prefix = POSIX_ACL_XATTR_DEFAULT,
 435        .flags  = ACL_TYPE_DEFAULT,
 436        .list   = ext4_xattr_list_acl_default,
 437        .get    = ext4_xattr_get_acl,
 438        .set    = ext4_xattr_set_acl,
 439};
 440
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