linux/fs/ext2/acl.c
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   1/*
   2 * linux/fs/ext2/acl.c
   3 *
   4 * Copyright (C) 2001-2003 Andreas Gruenbacher, <agruen@suse.de>
   5 */
   6
   7#include <linux/capability.h>
   8#include <linux/init.h>
   9#include <linux/sched.h>
  10#include <linux/slab.h>
  11#include <linux/fs.h>
  12#include "ext2.h"
  13#include "xattr.h"
  14#include "acl.h"
  15
  16/*
  17 * Convert from filesystem to in-memory representation.
  18 */
  19static struct posix_acl *
  20ext2_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
  76fail:
  77        posix_acl_release(acl);
  78        return ERR_PTR(-EINVAL);
  79}
  80
  81/*
  82 * Convert from in-memory to filesystem representation.
  83 */
  84static void *
  85ext2_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 = kmalloc(sizeof(ext2_acl_header) + acl->a_count *
  93                        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
 123fail:
 124        kfree(ext_acl);
 125        return ERR_PTR(-EINVAL);
 126}
 127
 128/*
 129 * inode->i_mutex: don't care
 130 */
 131static struct posix_acl *
 132ext2_get_acl(struct inode *inode, int type)
 133{
 134        int name_index;
 135        char *value = NULL;
 136        struct posix_acl *acl;
 137        int retval;
 138
 139        if (!test_opt(inode->i_sb, POSIX_ACL))
 140                return NULL;
 141
 142        acl = get_cached_acl(inode, type);
 143        if (acl != ACL_NOT_CACHED)
 144                return acl;
 145
 146        switch (type) {
 147        case ACL_TYPE_ACCESS:
 148                name_index = EXT2_XATTR_INDEX_POSIX_ACL_ACCESS;
 149                break;
 150        case ACL_TYPE_DEFAULT:
 151                name_index = EXT2_XATTR_INDEX_POSIX_ACL_DEFAULT;
 152                break;
 153        default:
 154                BUG();
 155        }
 156        retval = ext2_xattr_get(inode, name_index, "", NULL, 0);
 157        if (retval > 0) {
 158                value = kmalloc(retval, GFP_KERNEL);
 159                if (!value)
 160                        return ERR_PTR(-ENOMEM);
 161                retval = ext2_xattr_get(inode, name_index, "", value, retval);
 162        }
 163        if (retval > 0)
 164                acl = ext2_acl_from_disk(value, retval);
 165        else if (retval == -ENODATA || retval == -ENOSYS)
 166                acl = NULL;
 167        else
 168                acl = ERR_PTR(retval);
 169        kfree(value);
 170
 171        if (!IS_ERR(acl))
 172                set_cached_acl(inode, type, acl);
 173
 174        return acl;
 175}
 176
 177/*
 178 * inode->i_mutex: down
 179 */
 180static int
 181ext2_set_acl(struct inode *inode, int type, struct posix_acl *acl)
 182{
 183        int name_index;
 184        void *value = NULL;
 185        size_t size = 0;
 186        int error;
 187
 188        if (S_ISLNK(inode->i_mode))
 189                return -EOPNOTSUPP;
 190        if (!test_opt(inode->i_sb, POSIX_ACL))
 191                return 0;
 192
 193        switch(type) {
 194                case ACL_TYPE_ACCESS:
 195                        name_index = EXT2_XATTR_INDEX_POSIX_ACL_ACCESS;
 196                        if (acl) {
 197                                mode_t mode = inode->i_mode;
 198                                error = posix_acl_equiv_mode(acl, &mode);
 199                                if (error < 0)
 200                                        return error;
 201                                else {
 202                                        inode->i_mode = mode;
 203                                        mark_inode_dirty(inode);
 204                                        if (error == 0)
 205                                                acl = NULL;
 206                                }
 207                        }
 208                        break;
 209
 210                case ACL_TYPE_DEFAULT:
 211                        name_index = EXT2_XATTR_INDEX_POSIX_ACL_DEFAULT;
 212                        if (!S_ISDIR(inode->i_mode))
 213                                return acl ? -EACCES : 0;
 214                        break;
 215
 216                default:
 217                        return -EINVAL;
 218        }
 219        if (acl) {
 220                value = ext2_acl_to_disk(acl, &size);
 221                if (IS_ERR(value))
 222                        return (int)PTR_ERR(value);
 223        }
 224
 225        error = ext2_xattr_set(inode, name_index, "", value, size, 0);
 226
 227        kfree(value);
 228        if (!error)
 229                set_cached_acl(inode, type, acl);
 230        return error;
 231}
 232
 233int
 234ext2_check_acl(struct inode *inode, int mask)
 235{
 236        struct posix_acl *acl = ext2_get_acl(inode, ACL_TYPE_ACCESS);
 237
 238        if (IS_ERR(acl))
 239                return PTR_ERR(acl);
 240        if (acl) {
 241                int error = posix_acl_permission(inode, acl, mask);
 242                posix_acl_release(acl);
 243                return error;
 244        }
 245
 246        return -EAGAIN;
 247}
 248
 249/*
 250 * Initialize the ACLs of a new inode. Called from ext2_new_inode.
 251 *
 252 * dir->i_mutex: down
 253 * inode->i_mutex: up (access to inode is still exclusive)
 254 */
 255int
 256ext2_init_acl(struct inode *inode, struct inode *dir)
 257{
 258        struct posix_acl *acl = NULL;
 259        int error = 0;
 260
 261        if (!S_ISLNK(inode->i_mode)) {
 262                if (test_opt(dir->i_sb, POSIX_ACL)) {
 263                        acl = ext2_get_acl(dir, ACL_TYPE_DEFAULT);
 264                        if (IS_ERR(acl))
 265                                return PTR_ERR(acl);
 266                }
 267                if (!acl)
 268                        inode->i_mode &= ~current_umask();
 269        }
 270        if (test_opt(inode->i_sb, POSIX_ACL) && acl) {
 271               struct posix_acl *clone;
 272               mode_t mode;
 273
 274                if (S_ISDIR(inode->i_mode)) {
 275                        error = ext2_set_acl(inode, ACL_TYPE_DEFAULT, acl);
 276                        if (error)
 277                                goto cleanup;
 278                }
 279                clone = posix_acl_clone(acl, GFP_KERNEL);
 280                error = -ENOMEM;
 281                if (!clone)
 282                        goto cleanup;
 283                mode = inode->i_mode;
 284                error = posix_acl_create_masq(clone, &mode);
 285                if (error >= 0) {
 286                        inode->i_mode = mode;
 287                        if (error > 0) {
 288                                /* This is an extended ACL */
 289                                error = ext2_set_acl(inode,
 290                                                     ACL_TYPE_ACCESS, clone);
 291                        }
 292                }
 293                posix_acl_release(clone);
 294        }
 295cleanup:
 296       posix_acl_release(acl);
 297       return error;
 298}
 299
 300/*
 301 * Does chmod for an inode that may have an Access Control List. The
 302 * inode->i_mode field must be updated to the desired value by the caller
 303 * before calling this function.
 304 * Returns 0 on success, or a negative error number.
 305 *
 306 * We change the ACL rather than storing some ACL entries in the file
 307 * mode permission bits (which would be more efficient), because that
 308 * would break once additional permissions (like  ACL_APPEND, ACL_DELETE
 309 * for directories) are added. There are no more bits available in the
 310 * file mode.
 311 *
 312 * inode->i_mutex: down
 313 */
 314int
 315ext2_acl_chmod(struct inode *inode)
 316{
 317        struct posix_acl *acl, *clone;
 318        int error;
 319
 320        if (!test_opt(inode->i_sb, POSIX_ACL))
 321                return 0;
 322        if (S_ISLNK(inode->i_mode))
 323                return -EOPNOTSUPP;
 324        acl = ext2_get_acl(inode, ACL_TYPE_ACCESS);
 325        if (IS_ERR(acl) || !acl)
 326                return PTR_ERR(acl);
 327        clone = posix_acl_clone(acl, GFP_KERNEL);
 328        posix_acl_release(acl);
 329        if (!clone)
 330                return -ENOMEM;
 331        error = posix_acl_chmod_masq(clone, inode->i_mode);
 332        if (!error)
 333                error = ext2_set_acl(inode, ACL_TYPE_ACCESS, clone);
 334        posix_acl_release(clone);
 335        return error;
 336}
 337
 338/*
 339 * Extended attribut handlers
 340 */
 341static size_t
 342ext2_xattr_list_acl_access(struct inode *inode, char *list, size_t list_size,
 343                           const char *name, size_t name_len)
 344{
 345        const size_t size = sizeof(POSIX_ACL_XATTR_ACCESS);
 346
 347        if (!test_opt(inode->i_sb, POSIX_ACL))
 348                return 0;
 349        if (list && size <= list_size)
 350                memcpy(list, POSIX_ACL_XATTR_ACCESS, size);
 351        return size;
 352}
 353
 354static size_t
 355ext2_xattr_list_acl_default(struct inode *inode, char *list, size_t list_size,
 356                            const char *name, size_t name_len)
 357{
 358        const size_t size = sizeof(POSIX_ACL_XATTR_DEFAULT);
 359
 360        if (!test_opt(inode->i_sb, POSIX_ACL))
 361                return 0;
 362        if (list && size <= list_size)
 363                memcpy(list, POSIX_ACL_XATTR_DEFAULT, size);
 364        return size;
 365}
 366
 367static int
 368ext2_xattr_get_acl(struct inode *inode, int type, void *buffer, size_t size)
 369{
 370        struct posix_acl *acl;
 371        int error;
 372
 373        if (!test_opt(inode->i_sb, POSIX_ACL))
 374                return -EOPNOTSUPP;
 375
 376        acl = ext2_get_acl(inode, type);
 377        if (IS_ERR(acl))
 378                return PTR_ERR(acl);
 379        if (acl == NULL)
 380                return -ENODATA;
 381        error = posix_acl_to_xattr(acl, buffer, size);
 382        posix_acl_release(acl);
 383
 384        return error;
 385}
 386
 387static int
 388ext2_xattr_get_acl_access(struct inode *inode, const char *name,
 389                          void *buffer, size_t size)
 390{
 391        if (strcmp(name, "") != 0)
 392                return -EINVAL;
 393        return ext2_xattr_get_acl(inode, ACL_TYPE_ACCESS, buffer, size);
 394}
 395
 396static int
 397ext2_xattr_get_acl_default(struct inode *inode, const char *name,
 398                           void *buffer, size_t size)
 399{
 400        if (strcmp(name, "") != 0)
 401                return -EINVAL;
 402        return ext2_xattr_get_acl(inode, ACL_TYPE_DEFAULT, buffer, size);
 403}
 404
 405static int
 406ext2_xattr_set_acl(struct inode *inode, int type, const void *value,
 407                   size_t size)
 408{
 409        struct posix_acl *acl;
 410        int error;
 411
 412        if (!test_opt(inode->i_sb, POSIX_ACL))
 413                return -EOPNOTSUPP;
 414        if (!is_owner_or_cap(inode))
 415                return -EPERM;
 416
 417        if (value) {
 418                acl = posix_acl_from_xattr(value, size);
 419                if (IS_ERR(acl))
 420                        return PTR_ERR(acl);
 421                else if (acl) {
 422                        error = posix_acl_valid(acl);
 423                        if (error)
 424                                goto release_and_out;
 425                }
 426        } else
 427                acl = NULL;
 428
 429        error = ext2_set_acl(inode, type, acl);
 430
 431release_and_out:
 432        posix_acl_release(acl);
 433        return error;
 434}
 435
 436static int
 437ext2_xattr_set_acl_access(struct inode *inode, const char *name,
 438                          const void *value, size_t size, int flags)
 439{
 440        if (strcmp(name, "") != 0)
 441                return -EINVAL;
 442        return ext2_xattr_set_acl(inode, ACL_TYPE_ACCESS, value, size);
 443}
 444
 445static int
 446ext2_xattr_set_acl_default(struct inode *inode, const char *name,
 447                           const void *value, size_t size, int flags)
 448{
 449        if (strcmp(name, "") != 0)
 450                return -EINVAL;
 451        return ext2_xattr_set_acl(inode, ACL_TYPE_DEFAULT, value, size);
 452}
 453
 454struct xattr_handler ext2_xattr_acl_access_handler = {
 455        .prefix = POSIX_ACL_XATTR_ACCESS,
 456        .list   = ext2_xattr_list_acl_access,
 457        .get    = ext2_xattr_get_acl_access,
 458        .set    = ext2_xattr_set_acl_access,
 459};
 460
 461struct xattr_handler ext2_xattr_acl_default_handler = {
 462        .prefix = POSIX_ACL_XATTR_DEFAULT,
 463        .list   = ext2_xattr_list_acl_default,
 464        .get    = ext2_xattr_get_acl_default,
 465        .set    = ext2_xattr_set_acl_default,
 466};
 467