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
  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         unsigned 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         trace_xfs_get_acl(ip);
 118
 119         switch (type) {
 120         case ACL_TYPE_ACCESS:
 121                 ea_name = SGI_ACL_FILE;
 122                 break;
 123         case ACL_TYPE_DEFAULT:
 124                 ea_name = SGI_ACL_DEFAULT;
 125                 break;
 126         default:
 127                 BUG();
 128         }
 129
 130         /*
 131          * If we have a cached ACLs value just return it, not need to
 132          * go out to the disk.
 133          */
 134
 135         xfs_acl = kzalloc(sizeof(struct xfs_acl), GFP_KERNEL);
 136         if (!xfs_acl)
 137                 return ERR_PTR(-ENOMEM);
 138
 139         error = -xfs_attr_get(ip, ea_name, (unsigned char *)xfs_acl,
 140                                                         &len, ATTR_ROOT);
 141         if (error) {
 142                 /*
 143                  * If the attribute doesn't exist make sure we have a negative
 144                  * cache entry, for any other error assume it is transient and
 145                  * leave the cache entry as ACL_NOT_CACHED.
 146                  */
 147                 if (error == -ENOATTR) {
 148                         acl = NULL;
 149                         goto out_update_cache;
 150                 }
 151                 goto out;
 152         }
 153
 154         acl = xfs_acl_from_disk(xfs_acl);
 155         if (IS_ERR(acl))
 156                 goto out;
 157
 158  out_update_cache:
 159         set_cached_acl(inode, type, acl);
 160  out:
 161         kfree(xfs_acl);
 162         return acl;
 163 }
 164
 165 STATIC int
 166 xfs_set_acl(struct inode *inode, int type, struct posix_acl *acl)
 167 {
 168         struct xfs_inode *ip = XFS_I(inode);
 169         unsigned char *ea_name;
 170         int error;
 171
 172         if (S_ISLNK(inode->i_mode))
 173                 return -EOPNOTSUPP;
 174
 175         switch (type) {
 176         case ACL_TYPE_ACCESS:
 177                 ea_name = SGI_ACL_FILE;
 178                 break;
 179         case ACL_TYPE_DEFAULT:
 180                 if (!S_ISDIR(inode->i_mode))
 181                         return acl ? -EACCES : 0;
 182                 ea_name = SGI_ACL_DEFAULT;
 183                 break;
 184         default:
 185                 return -EINVAL;
 186         }
 187
 188         if (acl) {
 189                 struct xfs_acl *xfs_acl;
 190                 int len;
 191
 192                 xfs_acl = kzalloc(sizeof(struct xfs_acl), GFP_KERNEL);
 193                 if (!xfs_acl)
 194                         return -ENOMEM;
 195
 196                 xfs_acl_to_disk(xfs_acl, acl);
 197                 len = sizeof(struct xfs_acl) -
 198                         (sizeof(struct xfs_acl_entry) *
 199                          (XFS_ACL_MAX_ENTRIES - acl->a_count));
 200
 201                 error = -xfs_attr_set(ip, ea_name, (unsigned char *)xfs_acl,
 202                                 len, ATTR_ROOT);
 203
 204                 kfree(xfs_acl);
 205         } else {
 206                 /*
 207                  * A NULL ACL argument means we want to remove the ACL.
 208                  */
 209                 error = -xfs_attr_remove(ip, ea_name, ATTR_ROOT);
 210
 211                 /*
 212                  * If the attribute didn't exist to start with that's fine.
 213                  */
 214                 if (error == -ENOATTR)
 215                         error = 0;
 216         }
 217
 218         if (!error)
 219                 set_cached_acl(inode, type, acl);
 220         return error;
 221 }
 222
 223 static int
 224 xfs_set_mode(struct inode *inode, umode_t mode)
 225 {
 226         int error = 0;
 227
 228         if (mode != inode->i_mode) {
 229                 struct iattr iattr;
 230
 231                 iattr.ia_valid = ATTR_MODE | ATTR_CTIME;
 232                 iattr.ia_mode = mode;
 233                 iattr.ia_ctime = current_fs_time(inode->i_sb);
 234
 235                 error = -xfs_setattr_nonsize(XFS_I(inode), &iattr, XFS_ATTR_NOACL);
 236         }
 237
 238         return error;
 239 }
 240
 241 static int
 242 xfs_acl_exists(struct inode *inode, unsigned char *name)
 243 {
 244         int len = sizeof(struct xfs_acl);
 245
 246         return (xfs_attr_get(XFS_I(inode), name, NULL, &len,
 247                             ATTR_ROOT|ATTR_KERNOVAL) == 0);
 248 }
 249
 250 int
 251 posix_acl_access_exists(struct inode *inode)
 252 {
 253         return xfs_acl_exists(inode, SGI_ACL_FILE);
 254 }
 255
 256 int
 257 posix_acl_default_exists(struct inode *inode)
 258 {
 259         if (!S_ISDIR(inode->i_mode))
 260                 return 0;
 261         return xfs_acl_exists(inode, SGI_ACL_DEFAULT);
 262 }
 263
 264 /*
 265  * No need for i_mutex because the inode is not yet exposed to the VFS.
 266  */
 267 int
 268 xfs_inherit_acl(struct inode *inode, struct posix_acl *acl)
 269 {
 270         umode_t mode = inode->i_mode;
 271         int error = 0, inherit = 0;
 272
 273         if (S_ISDIR(inode->i_mode)) {
 274                 error = xfs_set_acl(inode, ACL_TYPE_DEFAULT, acl);
 275                 if (error)
 276                         goto out;
 277         }
 278
 279         error = posix_acl_create(&acl, GFP_KERNEL, &mode);
 280         if (error < 0)
 281                 return error;
 282
 283         /*
 284          * If posix_acl_create returns a positive value we need to
 285          * inherit a permission that can't be represented using the Unix
 286          * mode bits and we actually need to set an ACL.
 287          */
 288         if (error > 0)
 289                 inherit = 1;
 290
 291         error = xfs_set_mode(inode, mode);
 292         if (error)
 293                 goto out;
 294
 295         if (inherit)
 296                 error = xfs_set_acl(inode, ACL_TYPE_ACCESS, acl);
 297
 298 out:
 299         posix_acl_release(acl);
 300         return error;
 301 }
 302
 303 int
 304 xfs_acl_chmod(struct inode *inode)
 305 {
 306         struct posix_acl *acl;
 307         int error;
 308
 309         if (S_ISLNK(inode->i_mode))
 310                 return -EOPNOTSUPP;
 311
 312         acl = xfs_get_acl(inode, ACL_TYPE_ACCESS);
 313         if (IS_ERR(acl) || !acl)
 314                 return PTR_ERR(acl);
 315
 316         error = posix_acl_chmod(&acl, GFP_KERNEL, inode->i_mode);
 317         if (error)
 318                 return error;
 319
 320         error = xfs_set_acl(inode, ACL_TYPE_ACCESS, acl);
 321         posix_acl_release(acl);
 322         return error;
 323 }
 324
 325 static int
 326 xfs_xattr_acl_get(struct dentry *dentry, const char *name,
 327                 void *value, size_t size, int type)
 328 {
 329         struct posix_acl *acl;
 330         int error;
 331
 332         acl = xfs_get_acl(dentry->d_inode, type);
 333         if (IS_ERR(acl))
 334                 return PTR_ERR(acl);
 335         if (acl == NULL)
 336                 return -ENODATA;
 337
 338         error = posix_acl_to_xattr(acl, value, size);
 339         posix_acl_release(acl);
 340
 341         return error;
 342 }
 343
 344 static int
 345 xfs_xattr_acl_set(struct dentry *dentry, const char *name,
 346                 const void *value, size_t size, int flags, int type)
 347 {
 348         struct inode *inode = dentry->d_inode;
 349         struct posix_acl *acl = NULL;
 350         int error = 0;
 351
 352         if (flags & XATTR_CREATE)
 353                 return -EINVAL;
 354         if (type == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode))
 355                 return value ? -EACCES : 0;
 356         if ((current_fsuid() != inode->i_uid) && !capable(CAP_FOWNER))
 357                 return -EPERM;
 358
 359         if (!value)
 360                 goto set_acl;
 361
 362         acl = posix_acl_from_xattr(value, size);
 363         if (!acl) {
 364                 /*
 365                  * acl_set_file(3) may request that we set default ACLs with
 366                  * zero length -- defend (gracefully) against that here.
 367                  */
 368                 goto out;
 369         }
 370         if (IS_ERR(acl)) {
 371                 error = PTR_ERR(acl);
 372                 goto out;
 373         }
 374
 375         error = posix_acl_valid(acl);
 376         if (error)
 377                 goto out_release;
 378
 379         error = -EINVAL;
 380         if (acl->a_count > XFS_ACL_MAX_ENTRIES)
 381                 goto out_release;
 382
 383         if (type == ACL_TYPE_ACCESS) {
 384                 umode_t mode = inode->i_mode;
 385                 error = posix_acl_equiv_mode(acl, &mode);
 386
 387                 if (error <= 0) {
 388                         posix_acl_release(acl);
 389                         acl = NULL;
 390
 391                         if (error < 0)
 392                                 return error;
 393                 }
 394
 395                 error = xfs_set_mode(inode, mode);
 396                 if (error)
 397                         goto out_release;
 398         }
 399
 400  set_acl:
 401         error = xfs_set_acl(inode, type, acl);
 402  out_release:
 403         posix_acl_release(acl);
 404  out:
 405         return error;
 406 }
 407
 408 const struct xattr_handler xfs_xattr_acl_access_handler = {
 409         .prefix = POSIX_ACL_XATTR_ACCESS,
 410         .flags  = ACL_TYPE_ACCESS,
 411         .get    = xfs_xattr_acl_get,
 412         .set    = xfs_xattr_acl_set,
 413 };
 414
 415 const struct xattr_handler xfs_xattr_acl_default_handler = {
 416         .prefix = POSIX_ACL_XATTR_DEFAULT,
 417         .flags  = ACL_TYPE_DEFAULT,
 418         .get    = xfs_xattr_acl_get,
 419         .set    = xfs_xattr_acl_set,
 420 };