fs/xfs/linux-2.6/xfs_acl.c

   1 /*
   2  * Copyright (c) 2008, Christoph Hellwig
   3  * All Rights Reserved.
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU General Public License as
   7  * published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it would be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write the Free Software Foundation,
  16  * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  17  */
  18 #include "xfs.h"
  19 #include "xfs_acl.h"
  20 #include "xfs_attr.h"
  21 #include "xfs_bmap_btree.h"
  22 #include "xfs_inode.h"
  23 #include "xfs_vnodeops.h"
  24 #include <linux/xattr.h>
  25 #include <linux/posix_acl_xattr.h>
  26
  27
  28 /*
  29  * Locking scheme:
  30  *  - all ACL updates are protected by inode->i_mutex, which is taken before
  31  *    calling into this file.
  32  */
  33
  34 STATIC struct posix_acl *
  35 xfs_acl_from_disk(struct xfs_acl *aclp)
  36 {
  37         struct posix_acl_entry *acl_e;
  38         struct posix_acl *acl;
  39         struct xfs_acl_entry *ace;
  40         unsigned int count, i;
  41
  42         count = be32_to_cpu(aclp->acl_cnt);
  43         if (count > XFS_ACL_MAX_ENTRIES)
  44                 return ERR_PTR(-EFSCORRUPTED);
  45
  46         acl = posix_acl_alloc(count, GFP_KERNEL);
  47         if (!acl)
  48                 return ERR_PTR(-ENOMEM);
  49
  50         for (i = 0; i < count; i++) {
  51                 acl_e = &acl->a_entries[i];
  52                 ace = &aclp->acl_entry[i];
  53
  54                 /*
  55                  * The tag is 32 bits on disk and 16 bits in core.
  56                  *
  57                  * Because every access to it goes through the core
  58                  * format first this is not a problem.
  59                  */
  60                 acl_e->e_tag = be32_to_cpu(ace->ae_tag);
  61                 acl_e->e_perm = be16_to_cpu(ace->ae_perm);
  62
  63                 switch (acl_e->e_tag) {
  64                 case ACL_USER:
  65                 case ACL_GROUP:
  66                         acl_e->e_id = be32_to_cpu(ace->ae_id);
  67                         break;
  68                 case ACL_USER_OBJ:
  69                 case ACL_GROUP_OBJ:
  70                 case ACL_MASK:
  71                 case ACL_OTHER:
  72                         acl_e->e_id = ACL_UNDEFINED_ID;
  73                         break;
  74                 default:
  75                         goto fail;
  76                 }
  77         }
  78         return acl;
  79
  80 fail:
  81         posix_acl_release(acl);
  82         return ERR_PTR(-EINVAL);
  83 }
  84
  85 STATIC void
  86 xfs_acl_to_disk(struct xfs_acl *aclp, const struct posix_acl *acl)
  87 {
  88         const struct posix_acl_entry *acl_e;
  89         struct xfs_acl_entry *ace;
  90         int i;
  91
  92         aclp->acl_cnt = cpu_to_be32(acl->a_count);
  93         for (i = 0; i < acl->a_count; i++) {
  94                 ace = &aclp->acl_entry[i];
  95                 acl_e = &acl->a_entries[i];
  96
  97                 ace->ae_tag = cpu_to_be32(acl_e->e_tag);
  98                 ace->ae_id = cpu_to_be32(acl_e->e_id);
  99                 ace->ae_perm = cpu_to_be16(acl_e->e_perm);
 100         }
 101 }
 102
 103 struct posix_acl *
 104 xfs_get_acl(struct inode *inode, int type)
 105 {
 106         struct xfs_inode *ip = XFS_I(inode);
 107         struct posix_acl *acl;
 108         struct xfs_acl *xfs_acl;
 109         int len = sizeof(struct xfs_acl);
 110         char *ea_name;
 111         int error;
 112
 113         acl = get_cached_acl(inode, type);
 114         if (acl != ACL_NOT_CACHED)
 115                 return acl;
 116
 117         switch (type) {
 118         case ACL_TYPE_ACCESS:
 119                 ea_name = SGI_ACL_FILE;
 120                 break;
 121         case ACL_TYPE_DEFAULT:
 122                 ea_name = SGI_ACL_DEFAULT;
 123                 break;
 124         default:
 125                 BUG();
 126         }
 127
 128         /*
 129          * If we have a cached ACLs value just return it, not need to
 130          * go out to the disk.
 131          */
 132
 133         xfs_acl = kzalloc(sizeof(struct xfs_acl), GFP_KERNEL);
 134         if (!xfs_acl)
 135                 return ERR_PTR(-ENOMEM);
 136
 137         error = -xfs_attr_get(ip, ea_name, (char *)xfs_acl, &len, ATTR_ROOT);
 138         if (error) {
 139                 /*
 140                  * If the attribute doesn't exist make sure we have a negative
 141                  * cache entry, for any other error assume it is transient and
 142                  * leave the cache entry as ACL_NOT_CACHED.
 143                  */
 144                 if (error == -ENOATTR) {
 145                         acl = NULL;
 146                         goto out_update_cache;
 147                 }
 148                 goto out;
 149         }
 150
 151         acl = xfs_acl_from_disk(xfs_acl);
 152         if (IS_ERR(acl))
 153                 goto out;
 154
 155  out_update_cache:
 156         set_cached_acl(inode, type, acl);
 157  out:
 158         kfree(xfs_acl);
 159         return acl;
 160 }
 161
 162 STATIC int
 163 xfs_set_acl(struct inode *inode, int type, struct posix_acl *acl)
 164 {
 165         struct xfs_inode *ip = XFS_I(inode);
 166         char *ea_name;
 167         int error;
 168
 169         if (S_ISLNK(inode->i_mode))
 170                 return -EOPNOTSUPP;
 171
 172         switch (type) {
 173         case ACL_TYPE_ACCESS:
 174                 ea_name = SGI_ACL_FILE;
 175                 break;
 176         case ACL_TYPE_DEFAULT:
 177                 if (!S_ISDIR(inode->i_mode))
 178                         return acl ? -EACCES : 0;
 179                 ea_name = SGI_ACL_DEFAULT;
 180                 break;
 181         default:
 182                 return -EINVAL;
 183         }
 184
 185         if (acl) {
 186                 struct xfs_acl *xfs_acl;
 187                 int len;
 188
 189                 xfs_acl = kzalloc(sizeof(struct xfs_acl), GFP_KERNEL);
 190                 if (!xfs_acl)
 191                         return -ENOMEM;
 192
 193                 xfs_acl_to_disk(xfs_acl, acl);
 194                 len = sizeof(struct xfs_acl) -
 195                         (sizeof(struct xfs_acl_entry) *
 196                          (XFS_ACL_MAX_ENTRIES - acl->a_count));
 197
 198                 error = -xfs_attr_set(ip, ea_name, (char *)xfs_acl,
 199                                 len, ATTR_ROOT);
 200
 201                 kfree(xfs_acl);
 202         } else {
 203                 /*
 204                  * A NULL ACL argument means we want to remove the ACL.
 205                  */
 206                 error = -xfs_attr_remove(ip, ea_name, ATTR_ROOT);
 207
 208                 /*
 209                  * If the attribute didn't exist to start with that's fine.
 210                  */
 211                 if (error == -ENOATTR)
 212                         error = 0;
 213         }
 214
 215         if (!error)
 216                 set_cached_acl(inode, type, acl);
 217         return error;
 218 }
 219
 220 int
 221 xfs_check_acl(struct inode *inode, int mask)
 222 {
 223         struct xfs_inode *ip = XFS_I(inode);
 224         struct posix_acl *acl;
 225         int error = -EAGAIN;
 226
 227         xfs_itrace_entry(ip);
 228
 229         /*
 230          * If there is no attribute fork no ACL exists on this inode and
 231          * we can skip the whole exercise.
 232          */
 233         if (!XFS_IFORK_Q(ip))
 234                 return -EAGAIN;
 235
 236         acl = xfs_get_acl(inode, ACL_TYPE_ACCESS);
 237         if (IS_ERR(acl))
 238                 return PTR_ERR(acl);
 239         if (acl) {
 240                 error = posix_acl_permission(inode, acl, mask);
 241                 posix_acl_release(acl);
 242         }
 243
 244         return error;
 245 }
 246
 247 static int
 248 xfs_set_mode(struct inode *inode, mode_t mode)
 249 {
 250         int error = 0;
 251
 252         if (mode != inode->i_mode) {
 253                 struct iattr iattr;
 254
 255                 iattr.ia_valid = ATTR_MODE | ATTR_CTIME;
 256                 iattr.ia_mode = mode;
 257                 iattr.ia_ctime = current_fs_time(inode->i_sb);
 258
 259                 error = -xfs_setattr(XFS_I(inode), &iattr, XFS_ATTR_NOACL);
 260         }
 261
 262         return error;
 263 }
 264
 265 static int
 266 xfs_acl_exists(struct inode *inode, char *name)
 267 {
 268         int len = sizeof(struct xfs_acl);
 269
 270         return (xfs_attr_get(XFS_I(inode), name, NULL, &len,
 271                             ATTR_ROOT|ATTR_KERNOVAL) == 0);
 272 }
 273
 274 int
 275 posix_acl_access_exists(struct inode *inode)
 276 {
 277         return xfs_acl_exists(inode, SGI_ACL_FILE);
 278 }
 279
 280 int
 281 posix_acl_default_exists(struct inode *inode)
 282 {
 283         if (!S_ISDIR(inode->i_mode))
 284                 return 0;
 285         return xfs_acl_exists(inode, SGI_ACL_DEFAULT);
 286 }
 287
 288 /*
 289  * No need for i_mutex because the inode is not yet exposed to the VFS.
 290  */
 291 int
 292 xfs_inherit_acl(struct inode *inode, struct posix_acl *default_acl)
 293 {
 294         struct posix_acl *clone;
 295         mode_t mode;
 296         int error = 0, inherit = 0;
 297
 298         if (S_ISDIR(inode->i_mode)) {
 299                 error = xfs_set_acl(inode, ACL_TYPE_DEFAULT, default_acl);
 300                 if (error)
 301                         return error;
 302         }
 303
 304         clone = posix_acl_clone(default_acl, GFP_KERNEL);
 305         if (!clone)
 306                 return -ENOMEM;
 307
 308         mode = inode->i_mode;
 309         error = posix_acl_create_masq(clone, &mode);
 310         if (error < 0)
 311                 goto out_release_clone;
 312
 313         /*
 314          * If posix_acl_create_masq returns a positive value we need to
 315          * inherit a permission that can't be represented using the Unix
 316          * mode bits and we actually need to set an ACL.
 317          */
 318         if (error > 0)
 319                 inherit = 1;
 320
 321         error = xfs_set_mode(inode, mode);
 322         if (error)
 323                 goto out_release_clone;
 324
 325         if (inherit)
 326                 error = xfs_set_acl(inode, ACL_TYPE_ACCESS, clone);
 327
 328  out_release_clone:
 329         posix_acl_release(clone);
 330         return error;
 331 }
 332
 333 int
 334 xfs_acl_chmod(struct inode *inode)
 335 {
 336         struct posix_acl *acl, *clone;
 337         int error;
 338
 339         if (S_ISLNK(inode->i_mode))
 340                 return -EOPNOTSUPP;
 341
 342         acl = xfs_get_acl(inode, ACL_TYPE_ACCESS);
 343         if (IS_ERR(acl) || !acl)
 344                 return PTR_ERR(acl);
 345
 346         clone = posix_acl_clone(acl, GFP_KERNEL);
 347         posix_acl_release(acl);
 348         if (!clone)
 349                 return -ENOMEM;
 350
 351         error = posix_acl_chmod_masq(clone, inode->i_mode);
 352         if (!error)
 353                 error = xfs_set_acl(inode, ACL_TYPE_ACCESS, clone);
 354
 355         posix_acl_release(clone);
 356         return error;
 357 }
 358
 359 /*
 360  * System xattr handlers.
 361  *
 362  * Currently Posix ACLs are the only system namespace extended attribute
 363  * handlers supported by XFS, so we just implement the handlers here.
 364  * If we ever support other system extended attributes this will need
 365  * some refactoring.
 366  */
 367
 368 static int
 369 xfs_decode_acl(const char *name)
 370 {
 371         if (strcmp(name, "posix_acl_access") == 0)
 372                 return ACL_TYPE_ACCESS;
 373         else if (strcmp(name, "posix_acl_default") == 0)
 374                 return ACL_TYPE_DEFAULT;
 375         return -EINVAL;
 376 }
 377
 378 static int
 379 xfs_xattr_system_get(struct inode *inode, const char *name,
 380                 void *value, size_t size)
 381 {
 382         struct posix_acl *acl;
 383         int type, error;
 384
 385         type = xfs_decode_acl(name);
 386         if (type < 0)
 387                 return type;
 388
 389         acl = xfs_get_acl(inode, type);
 390         if (IS_ERR(acl))
 391                 return PTR_ERR(acl);
 392         if (acl == NULL)
 393                 return -ENODATA;
 394
 395         error = posix_acl_to_xattr(acl, value, size);
 396         posix_acl_release(acl);
 397
 398         return error;
 399 }
 400
 401 static int
 402 xfs_xattr_system_set(struct inode *inode, const char *name,
 403                 const void *value, size_t size, int flags)
 404 {
 405         struct posix_acl *acl = NULL;
 406         int error = 0, type;
 407
 408         type = xfs_decode_acl(name);
 409         if (type < 0)
 410                 return type;
 411         if (flags & XATTR_CREATE)
 412                 return -EINVAL;
 413         if (type == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode))
 414                 return value ? -EACCES : 0;
 415         if ((current_fsuid() != inode->i_uid) && !capable(CAP_FOWNER))
 416                 return -EPERM;
 417
 418         if (!value)
 419                 goto set_acl;
 420
 421         acl = posix_acl_from_xattr(value, size);
 422         if (!acl) {
 423                 /*
 424                  * acl_set_file(3) may request that we set default ACLs with
 425                  * zero length -- defend (gracefully) against that here.
 426                  */
 427                 goto out;
 428         }
 429         if (IS_ERR(acl)) {
 430                 error = PTR_ERR(acl);
 431                 goto out;
 432         }
 433
 434         error = posix_acl_valid(acl);
 435         if (error)
 436                 goto out_release;
 437
 438         error = -EINVAL;
 439         if (acl->a_count > XFS_ACL_MAX_ENTRIES)
 440                 goto out_release;
 441
 442         if (type == ACL_TYPE_ACCESS) {
 443                 mode_t mode = inode->i_mode;
 444                 error = posix_acl_equiv_mode(acl, &mode);
 445
 446                 if (error <= 0) {
 447                         posix_acl_release(acl);
 448                         acl = NULL;
 449
 450                         if (error < 0)
 451                                 return error;
 452                 }
 453
 454                 error = xfs_set_mode(inode, mode);
 455                 if (error)
 456                         goto out_release;
 457         }
 458
 459  set_acl:
 460         error = xfs_set_acl(inode, type, acl);
 461  out_release:
 462         posix_acl_release(acl);
 463  out:
 464         return error;
 465 }
 466
 467 struct xattr_handler xfs_xattr_system_handler = {
 468         .prefix = XATTR_SYSTEM_PREFIX,
 469         .get    = xfs_xattr_system_get,
 470         .set    = xfs_xattr_system_set,
 471 };