fs/xfs/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 "xfs_trace.h"
  25 #include <linux/slab.h>
  26 #include <linux/xattr.h>
  27 #include <linux/posix_acl_xattr.h>
  28
  29
  30 /*
  31  * Locking scheme:
  32  *  - all ACL updates are protected by inode->i_mutex, which is taken before
  33  *    calling into this file.
  34  */
  35
  36 STATIC struct posix_acl *
  37 xfs_acl_from_disk(struct xfs_acl *aclp)
  38 {
  39         struct posix_acl_entry *acl_e;
  40         struct posix_acl *acl;
  41         struct xfs_acl_entry *ace;
  42         int count, i;
  43
  44         count = be32_to_cpu(aclp->acl_cnt);
  45         if (count > XFS_ACL_MAX_ENTRIES)
  46                 return ERR_PTR(-EFSCORRUPTED);
  47
  48         acl = posix_acl_alloc(count, GFP_KERNEL);
  49         if (!acl)
  50                 return ERR_PTR(-ENOMEM);
  51
  52         for (i = 0; i < count; i++) {
  53                 acl_e = &acl->a_entries[i];
  54                 ace = &aclp->acl_entry[i];
  55
  56                 /*
  57                  * The tag is 32 bits on disk and 16 bits in core.
  58                  *
  59                  * Because every access to it goes through the core
  60                  * format first this is not a problem.
  61                  */
  62                 acl_e->e_tag = be32_to_cpu(ace->ae_tag);
  63                 acl_e->e_perm = be16_to_cpu(ace->ae_perm);
  64
  65                 switch (acl_e->e_tag) {
  66                 case ACL_USER:
  67                 case ACL_GROUP:
  68                         acl_e->e_id = be32_to_cpu(ace->ae_id);
  69                         break;
  70                 case ACL_USER_OBJ:
  71                 case ACL_GROUP_OBJ:
  72                 case ACL_MASK:
  73                 case ACL_OTHER:
  74                         acl_e->e_id = ACL_UNDEFINED_ID;
  75                         break;
  76                 default:
  77                         goto fail;
  78                 }
  79         }
  80         return acl;
  81
  82 fail:
  83         posix_acl_release(acl);
  84         return ERR_PTR(-EINVAL);
  85 }
  86
  87 STATIC void
  88 xfs_acl_to_disk(struct xfs_acl *aclp, const struct posix_acl *acl)
  89 {
  90         const struct posix_acl_entry *acl_e;
  91         struct xfs_acl_entry *ace;
  92         int i;
  93
  94         aclp->acl_cnt = cpu_to_be32(acl->a_count);
  95         for (i = 0; i < acl->a_count; i++) {
  96                 ace = &aclp->acl_entry[i];
  97                 acl_e = &acl->a_entries[i];
  98
  99                 ace->ae_tag = cpu_to_be32(acl_e->e_tag);
 100                 ace->ae_id = cpu_to_be32(acl_e->e_id);
 101                 ace->ae_perm = cpu_to_be16(acl_e->e_perm);
 102         }
 103 }
 104
 105 struct posix_acl *
 106 xfs_get_acl(struct inode *inode, int type)
 107 {
 108         struct xfs_inode *ip = XFS_I(inode);
 109         struct posix_acl *acl;
 110         struct xfs_acl *xfs_acl;
 111         int len = sizeof(struct xfs_acl);
 112         unsigned char *ea_name;
 113         int error;
 114
 115         acl = get_cached_acl(inode, type);
 116         if (acl != ACL_NOT_CACHED)
 117                 return acl;
 118
 119         trace_xfs_get_acl(ip);
 120
 121         switch (type) {
 122         case ACL_TYPE_ACCESS:
 123                 ea_name = SGI_ACL_FILE;
 124                 break;
 125         case ACL_TYPE_DEFAULT:
 126                 ea_name = SGI_ACL_DEFAULT;
 127                 break;
 128         default:
 129                 BUG();
 130         }
 131
 132         /*
 133          * If we have a cached ACLs value just return it, not need to
 134          * go out to the disk.
 135          */
 136
 137         xfs_acl = kzalloc(sizeof(struct xfs_acl), GFP_KERNEL);
 138         if (!xfs_acl)
 139                 return ERR_PTR(-ENOMEM);
 140
 141         error = -xfs_attr_get(ip, ea_name, (unsigned char *)xfs_acl,
 142                                                         &len, ATTR_ROOT);
 143         if (error) {
 144                 /*
 145                  * If the attribute doesn't exist make sure we have a negative
 146                  * cache entry, for any other error assume it is transient and
 147                  * leave the cache entry as ACL_NOT_CACHED.
 148                  */
 149                 if (error == -ENOATTR) {
 150                         acl = NULL;
 151                         goto out_update_cache;
 152                 }
 153                 goto out;
 154         }
 155
 156         acl = xfs_acl_from_disk(xfs_acl);
 157         if (IS_ERR(acl))
 158                 goto out;
 159
 160  out_update_cache:
 161         set_cached_acl(inode, type, acl);
 162  out:
 163         kfree(xfs_acl);
 164         return acl;
 165 }
 166
 167 STATIC int
 168 xfs_set_acl(struct inode *inode, int type, struct posix_acl *acl)
 169 {
 170         struct xfs_inode *ip = XFS_I(inode);
 171         unsigned char *ea_name;
 172         int error;
 173
 174         if (S_ISLNK(inode->i_mode))
 175                 return -EOPNOTSUPP;
 176
 177         switch (type) {
 178         case ACL_TYPE_ACCESS:
 179                 ea_name = SGI_ACL_FILE;
 180                 break;
 181         case ACL_TYPE_DEFAULT:
 182                 if (!S_ISDIR(inode->i_mode))
 183                         return acl ? -EACCES : 0;
 184                 ea_name = SGI_ACL_DEFAULT;
 185                 break;
 186         default:
 187                 return -EINVAL;
 188         }
 189
 190         if (acl) {
 191                 struct xfs_acl *xfs_acl;
 192                 int len;
 193
 194                 xfs_acl = kzalloc(sizeof(struct xfs_acl), GFP_KERNEL);
 195                 if (!xfs_acl)
 196                         return -ENOMEM;
 197
 198                 xfs_acl_to_disk(xfs_acl, acl);
 199                 len = sizeof(struct xfs_acl) -
 200                         (sizeof(struct xfs_acl_entry) *
 201                          (XFS_ACL_MAX_ENTRIES - acl->a_count));
 202
 203                 error = -xfs_attr_set(ip, ea_name, (unsigned char *)xfs_acl,
 204                                 len, ATTR_ROOT);
 205
 206                 kfree(xfs_acl);
 207         } else {
 208                 /*
 209                  * A NULL ACL argument means we want to remove the ACL.
 210                  */
 211                 error = -xfs_attr_remove(ip, ea_name, ATTR_ROOT);
 212
 213                 /*
 214                  * If the attribute didn't exist to start with that's fine.
 215                  */
 216                 if (error == -ENOATTR)
 217                         error = 0;
 218         }
 219
 220         if (!error)
 221                 set_cached_acl(inode, type, acl);
 222         return error;
 223 }
 224
 225 static int
 226 xfs_set_mode(struct inode *inode, umode_t mode)
 227 {
 228         int error = 0;
 229
 230         if (mode != inode->i_mode) {
 231                 struct iattr iattr;
 232
 233                 iattr.ia_valid = ATTR_MODE | ATTR_CTIME;
 234                 iattr.ia_mode = mode;
 235                 iattr.ia_ctime = current_fs_time(inode->i_sb);
 236
 237                 error = -xfs_setattr_nonsize(XFS_I(inode), &iattr, XFS_ATTR_NOACL);
 238         }
 239
 240         return error;
 241 }
 242
 243 static int
 244 xfs_acl_exists(struct inode *inode, unsigned char *name)
 245 {
 246         int len = sizeof(struct xfs_acl);
 247
 248         return (xfs_attr_get(XFS_I(inode), name, NULL, &len,
 249                             ATTR_ROOT|ATTR_KERNOVAL) == 0);
 250 }
 251
 252 int
 253 posix_acl_access_exists(struct inode *inode)
 254 {
 255         return xfs_acl_exists(inode, SGI_ACL_FILE);
 256 }
 257
 258 int
 259 posix_acl_default_exists(struct inode *inode)
 260 {
 261         if (!S_ISDIR(inode->i_mode))
 262                 return 0;
 263         return xfs_acl_exists(inode, SGI_ACL_DEFAULT);
 264 }
 265
 266 /*
 267  * No need for i_mutex because the inode is not yet exposed to the VFS.
 268  */
 269 int
 270 xfs_inherit_acl(struct inode *inode, struct posix_acl *acl)
 271 {
 272         umode_t mode = inode->i_mode;
 273         int error = 0, inherit = 0;
 274
 275         if (S_ISDIR(inode->i_mode)) {
 276                 error = xfs_set_acl(inode, ACL_TYPE_DEFAULT, acl);
 277                 if (error)
 278                         goto out;
 279         }
 280
 281         error = posix_acl_create(&acl, GFP_KERNEL, &mode);
 282         if (error < 0)
 283                 return error;
 284
 285         /*
 286          * If posix_acl_create returns a positive value we need to
 287          * inherit a permission that can't be represented using the Unix
 288          * mode bits and we actually need to set an ACL.
 289          */
 290         if (error > 0)
 291                 inherit = 1;
 292
 293         error = xfs_set_mode(inode, mode);
 294         if (error)
 295                 goto out;
 296
 297         if (inherit)
 298                 error = xfs_set_acl(inode, ACL_TYPE_ACCESS, acl);
 299
 300 out:
 301         posix_acl_release(acl);
 302         return error;
 303 }
 304
 305 int
 306 xfs_acl_chmod(struct inode *inode)
 307 {
 308         struct posix_acl *acl;
 309         int error;
 310
 311         if (S_ISLNK(inode->i_mode))
 312                 return -EOPNOTSUPP;
 313
 314         acl = xfs_get_acl(inode, ACL_TYPE_ACCESS);
 315         if (IS_ERR(acl) || !acl)
 316                 return PTR_ERR(acl);
 317
 318         error = posix_acl_chmod(&acl, GFP_KERNEL, inode->i_mode);
 319         if (error)
 320                 return error;
 321
 322         error = xfs_set_acl(inode, ACL_TYPE_ACCESS, acl);
 323         posix_acl_release(acl);
 324         return error;
 325 }
 326
 327 static int
 328 xfs_xattr_acl_get(struct dentry *dentry, const char *name,
 329                 void *value, size_t size, int type)
 330 {
 331         struct posix_acl *acl;
 332         int error;
 333
 334         acl = xfs_get_acl(dentry->d_inode, type);
 335         if (IS_ERR(acl))
 336                 return PTR_ERR(acl);
 337         if (acl == NULL)
 338                 return -ENODATA;
 339
 340         error = posix_acl_to_xattr(acl, value, size);
 341         posix_acl_release(acl);
 342
 343         return error;
 344 }
 345
 346 static int
 347 xfs_xattr_acl_set(struct dentry *dentry, const char *name,
 348                 const void *value, size_t size, int flags, int type)
 349 {
 350         struct inode *inode = dentry->d_inode;
 351         struct posix_acl *acl = NULL;
 352         int error = 0;
 353
 354         if (flags & XATTR_CREATE)
 355                 return -EINVAL;
 356         if (type == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode))
 357                 return value ? -EACCES : 0;
 358         if ((current_fsuid() != inode->i_uid) && !capable(CAP_FOWNER))
 359                 return -EPERM;
 360
 361         if (!value)
 362                 goto set_acl;
 363
 364         acl = posix_acl_from_xattr(value, size);
 365         if (!acl) {
 366                 /*
 367                  * acl_set_file(3) may request that we set default ACLs with
 368                  * zero length -- defend (gracefully) against that here.
 369                  */
 370                 goto out;
 371         }
 372         if (IS_ERR(acl)) {
 373                 error = PTR_ERR(acl);
 374                 goto out;
 375         }
 376
 377         error = posix_acl_valid(acl);
 378         if (error)
 379                 goto out_release;
 380
 381         error = -EINVAL;
 382         if (acl->a_count > XFS_ACL_MAX_ENTRIES)
 383                 goto out_release;
 384
 385         if (type == ACL_TYPE_ACCESS) {
 386                 umode_t mode = inode->i_mode;
 387                 error = posix_acl_equiv_mode(acl, &mode);
 388
 389                 if (error <= 0) {
 390                         posix_acl_release(acl);
 391                         acl = NULL;
 392
 393                         if (error < 0)
 394                                 return error;
 395                 }
 396
 397                 error = xfs_set_mode(inode, mode);
 398                 if (error)
 399                         goto out_release;
 400         }
 401
 402  set_acl:
 403         error = xfs_set_acl(inode, type, acl);
 404  out_release:
 405         posix_acl_release(acl);
 406  out:
 407         return error;
 408 }
 409
 410 const struct xattr_handler xfs_xattr_acl_access_handler = {
 411         .prefix = POSIX_ACL_XATTR_ACCESS,
 412         .flags  = ACL_TYPE_ACCESS,
 413         .get    = xfs_xattr_acl_get,
 414         .set    = xfs_xattr_acl_set,
 415 };
 416
 417 const struct xattr_handler xfs_xattr_acl_default_handler = {
 418         .prefix = POSIX_ACL_XATTR_DEFAULT,
 419         .flags  = ACL_TYPE_DEFAULT,
 420         .get    = xfs_xattr_acl_get,
 421         .set    = xfs_xattr_acl_set,
 422 };