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                                        inode->i_ctime = CURRENT_TIME_SEC;
 204                                        mark_inode_dirty(inode);
 205                                        if (error == 0)
 206                                                acl = NULL;
 207                                }
 208                        }
 209                        break;
 210
 211                case ACL_TYPE_DEFAULT:
 212                        name_index = EXT2_XATTR_INDEX_POSIX_ACL_DEFAULT;
 213                        if (!S_ISDIR(inode->i_mode))
 214                                return acl ? -EACCES : 0;
 215                        break;
 216
 217                default:
 218                        return -EINVAL;
 219        }
 220        if (acl) {
 221                value = ext2_acl_to_disk(acl, &size);
 222                if (IS_ERR(value))
 223                        return (int)PTR_ERR(value);
 224        }
 225
 226        error = ext2_xattr_set(inode, name_index, "", value, size, 0);
 227
 228        kfree(value);
 229        if (!error)
 230                set_cached_acl(inode, type, acl);
 231        return error;
 232}
 233
 234int
 235ext2_check_acl(struct inode *inode, int mask, unsigned int flags)
 236{
 237        struct posix_acl *acl;
 238
 239        if (flags & IPERM_FLAG_RCU) {
 240                if (!negative_cached_acl(inode, ACL_TYPE_ACCESS))
 241                        return -ECHILD;
 242                return -EAGAIN;
 243        }
 244
 245        acl = ext2_get_acl(inode, ACL_TYPE_ACCESS);
 246        if (IS_ERR(acl))
 247                return PTR_ERR(acl);
 248        if (acl) {
 249                int error = posix_acl_permission(inode, acl, mask);
 250                posix_acl_release(acl);
 251                return error;
 252        }
 253
 254        return -EAGAIN;
 255}
 256
 257/*
 258 * Initialize the ACLs of a new inode. Called from ext2_new_inode.
 259 *
 260 * dir->i_mutex: down
 261 * inode->i_mutex: up (access to inode is still exclusive)
 262 */
 263int
 264ext2_init_acl(struct inode *inode, struct inode *dir)
 265{
 266        struct posix_acl *acl = NULL;
 267        int error = 0;
 268
 269        if (!S_ISLNK(inode->i_mode)) {
 270                if (test_opt(dir->i_sb, POSIX_ACL)) {
 271                        acl = ext2_get_acl(dir, ACL_TYPE_DEFAULT);
 272                        if (IS_ERR(acl))
 273                                return PTR_ERR(acl);
 274                }
 275                if (!acl)
 276                        inode->i_mode &= ~current_umask();
 277        }
 278        if (test_opt(inode->i_sb, POSIX_ACL) && acl) {
 279               struct posix_acl *clone;
 280               mode_t mode;
 281
 282                if (S_ISDIR(inode->i_mode)) {
 283                        error = ext2_set_acl(inode, ACL_TYPE_DEFAULT, acl);
 284                        if (error)
 285                                goto cleanup;
 286                }
 287                clone = posix_acl_clone(acl, GFP_KERNEL);
 288                error = -ENOMEM;
 289                if (!clone)
 290                        goto cleanup;
 291                mode = inode->i_mode;
 292                error = posix_acl_create_masq(clone, &mode);
 293                if (error >= 0) {
 294                        inode->i_mode = mode;
 295                        if (error > 0) {
 296                                /* This is an extended ACL */
 297                                error = ext2_set_acl(inode,
 298                                                     ACL_TYPE_ACCESS, clone);
 299                        }
 300                }
 301                posix_acl_release(clone);
 302        }
 303cleanup:
 304       posix_acl_release(acl);
 305       return error;
 306}
 307
 308/*
 309 * Does chmod for an inode that may have an Access Control List. The
 310 * inode->i_mode field must be updated to the desired value by the caller
 311 * before calling this function.
 312 * Returns 0 on success, or a negative error number.
 313 *
 314 * We change the ACL rather than storing some ACL entries in the file
 315 * mode permission bits (which would be more efficient), because that
 316 * would break once additional permissions (like  ACL_APPEND, ACL_DELETE
 317 * for directories) are added. There are no more bits available in the
 318 * file mode.
 319 *
 320 * inode->i_mutex: down
 321 */
 322int
 323ext2_acl_chmod(struct inode *inode)
 324{
 325        struct posix_acl *acl, *clone;
 326        int error;
 327
 328        if (!test_opt(inode->i_sb, POSIX_ACL))
 329                return 0;
 330        if (S_ISLNK(inode->i_mode))
 331                return -EOPNOTSUPP;
 332        acl = ext2_get_acl(inode, ACL_TYPE_ACCESS);
 333        if (IS_ERR(acl) || !acl)
 334                return PTR_ERR(acl);
 335        clone = posix_acl_clone(acl, GFP_KERNEL);
 336        posix_acl_release(acl);
 337        if (!clone)
 338                return -ENOMEM;
 339        error = posix_acl_chmod_masq(clone, inode->i_mode);
 340        if (!error)
 341                error = ext2_set_acl(inode, ACL_TYPE_ACCESS, clone);
 342        posix_acl_release(clone);
 343        return error;
 344}
 345
 346/*
 347 * Extended attribut handlers
 348 */
 349static size_t
 350ext2_xattr_list_acl_access(struct dentry *dentry, char *list, size_t list_size,
 351                           const char *name, size_t name_len, int type)
 352{
 353        const size_t size = sizeof(POSIX_ACL_XATTR_ACCESS);
 354
 355        if (!test_opt(dentry->d_sb, POSIX_ACL))
 356                return 0;
 357        if (list && size <= list_size)
 358                memcpy(list, POSIX_ACL_XATTR_ACCESS, size);
 359        return size;
 360}
 361
 362static size_t
 363ext2_xattr_list_acl_default(struct dentry *dentry, char *list, size_t list_size,
 364                            const char *name, size_t name_len, int type)
 365{
 366        const size_t size = sizeof(POSIX_ACL_XATTR_DEFAULT);
 367
 368        if (!test_opt(dentry->d_sb, POSIX_ACL))
 369                return 0;
 370        if (list && size <= list_size)
 371                memcpy(list, POSIX_ACL_XATTR_DEFAULT, size);
 372        return size;
 373}
 374
 375static int
 376ext2_xattr_get_acl(struct dentry *dentry, const char *name, void *buffer,
 377                   size_t size, int type)
 378{
 379        struct posix_acl *acl;
 380        int error;
 381
 382        if (strcmp(name, "") != 0)
 383                return -EINVAL;
 384        if (!test_opt(dentry->d_sb, POSIX_ACL))
 385                return -EOPNOTSUPP;
 386
 387        acl = ext2_get_acl(dentry->d_inode, type);
 388        if (IS_ERR(acl))
 389                return PTR_ERR(acl);
 390        if (acl == NULL)
 391                return -ENODATA;
 392        error = posix_acl_to_xattr(acl, buffer, size);
 393        posix_acl_release(acl);
 394
 395        return error;
 396}
 397
 398static int
 399ext2_xattr_set_acl(struct dentry *dentry, const char *name, const void *value,
 400                   size_t size, int flags, int type)
 401{
 402        struct posix_acl *acl;
 403        int error;
 404
 405        if (strcmp(name, "") != 0)
 406                return -EINVAL;
 407        if (!test_opt(dentry->d_sb, POSIX_ACL))
 408                return -EOPNOTSUPP;
 409        if (!is_owner_or_cap(dentry->d_inode))
 410                return -EPERM;
 411
 412        if (value) {
 413                acl = posix_acl_from_xattr(value, size);
 414                if (IS_ERR(acl))
 415                        return PTR_ERR(acl);
 416                else if (acl) {
 417                        error = posix_acl_valid(acl);
 418                        if (error)
 419                                goto release_and_out;
 420                }
 421        } else
 422                acl = NULL;
 423
 424        error = ext2_set_acl(dentry->d_inode, type, acl);
 425
 426release_and_out:
 427        posix_acl_release(acl);
 428        return error;
 429}
 430
 431const struct xattr_handler ext2_xattr_acl_access_handler = {
 432        .prefix = POSIX_ACL_XATTR_ACCESS,
 433        .flags  = ACL_TYPE_ACCESS,
 434        .list   = ext2_xattr_list_acl_access,
 435        .get    = ext2_xattr_get_acl,
 436        .set    = ext2_xattr_set_acl,
 437};
 438
 439const struct xattr_handler ext2_xattr_acl_default_handler = {
 440        .prefix = POSIX_ACL_XATTR_DEFAULT,
 441        .flags  = ACL_TYPE_DEFAULT,
 442        .list   = ext2_xattr_list_acl_default,
 443        .get    = ext2_xattr_get_acl,
 444        .set    = ext2_xattr_set_acl,
 445};
 446