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