Pileus Git - ~andy/linux/blob - fs/posix_acl.c

   1 /*
   2  * linux/fs/posix_acl.c
   3  *
   4  *  Copyright (C) 2002 by Andreas Gruenbacher <a.gruenbacher@computer.org>
   5  *
   6  *  Fixes from William Schumacher incorporated on 15 March 2001.
   7  *     (Reported by Charles Bertsch, <CBertsch@microtest.com>).
   8  */
   9
  10 /*
  11  *  This file contains generic functions for manipulating
  12  *  POSIX 1003.1e draft standard 17 ACLs.
  13  */
  14
  15 #include <linux/kernel.h>
  16 #include <linux/slab.h>
  17 #include <linux/atomic.h>
  18 #include <linux/fs.h>
  19 #include <linux/sched.h>
  20 #include <linux/posix_acl.h>
  21 #include <linux/export.h>
  22
  23 #include <linux/errno.h>
  24
  25 struct posix_acl **acl_by_type(struct inode *inode, int type)
  26 {
  27         switch (type) {
  28         case ACL_TYPE_ACCESS:
  29                 return &inode->i_acl;
  30         case ACL_TYPE_DEFAULT:
  31                 return &inode->i_default_acl;
  32         default:
  33                 BUG();
  34         }
  35 }
  36 EXPORT_SYMBOL(acl_by_type);
  37
  38 struct posix_acl *get_cached_acl(struct inode *inode, int type)
  39 {
  40         struct posix_acl **p = acl_by_type(inode, type);
  41         struct posix_acl *acl = ACCESS_ONCE(*p);
  42         if (acl) {
  43                 spin_lock(&inode->i_lock);
  44                 acl = *p;
  45                 if (acl != ACL_NOT_CACHED)
  46                         acl = posix_acl_dup(acl);
  47                 spin_unlock(&inode->i_lock);
  48         }
  49         return acl;
  50 }
  51 EXPORT_SYMBOL(get_cached_acl);
  52
  53 struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type)
  54 {
  55         return rcu_dereference(*acl_by_type(inode, type));
  56 }
  57 EXPORT_SYMBOL(get_cached_acl_rcu);
  58
  59 void set_cached_acl(struct inode *inode, int type, struct posix_acl *acl)
  60 {
  61         struct posix_acl **p = acl_by_type(inode, type);
  62         struct posix_acl *old;
  63         spin_lock(&inode->i_lock);
  64         old = *p;
  65         rcu_assign_pointer(*p, posix_acl_dup(acl));
  66         spin_unlock(&inode->i_lock);
  67         if (old != ACL_NOT_CACHED)
  68                 posix_acl_release(old);
  69 }
  70 EXPORT_SYMBOL(set_cached_acl);
  71
  72 void forget_cached_acl(struct inode *inode, int type)
  73 {
  74         struct posix_acl **p = acl_by_type(inode, type);
  75         struct posix_acl *old;
  76         spin_lock(&inode->i_lock);
  77         old = *p;
  78         *p = ACL_NOT_CACHED;
  79         spin_unlock(&inode->i_lock);
  80         if (old != ACL_NOT_CACHED)
  81                 posix_acl_release(old);
  82 }
  83 EXPORT_SYMBOL(forget_cached_acl);
  84
  85 void forget_all_cached_acls(struct inode *inode)
  86 {
  87         struct posix_acl *old_access, *old_default;
  88         spin_lock(&inode->i_lock);
  89         old_access = inode->i_acl;
  90         old_default = inode->i_default_acl;
  91         inode->i_acl = inode->i_default_acl = ACL_NOT_CACHED;
  92         spin_unlock(&inode->i_lock);
  93         if (old_access != ACL_NOT_CACHED)
  94                 posix_acl_release(old_access);
  95         if (old_default != ACL_NOT_CACHED)
  96                 posix_acl_release(old_default);
  97 }
  98 EXPORT_SYMBOL(forget_all_cached_acls);
  99
 100 /*
 101  * Init a fresh posix_acl
 102  */
 103 void
 104 posix_acl_init(struct posix_acl *acl, int count)
 105 {
 106         atomic_set(&acl->a_refcount, 1);
 107         acl->a_count = count;
 108 }
 109 EXPORT_SYMBOL(posix_acl_init);
 110
 111 /*
 112  * Allocate a new ACL with the specified number of entries.
 113  */
 114 struct posix_acl *
 115 posix_acl_alloc(int count, gfp_t flags)
 116 {
 117         const size_t size = sizeof(struct posix_acl) +
 118                             count * sizeof(struct posix_acl_entry);
 119         struct posix_acl *acl = kmalloc(size, flags);
 120         if (acl)
 121                 posix_acl_init(acl, count);
 122         return acl;
 123 }
 124 EXPORT_SYMBOL(posix_acl_alloc);
 125
 126 /*
 127  * Clone an ACL.
 128  */
 129 static struct posix_acl *
 130 posix_acl_clone(const struct posix_acl *acl, gfp_t flags)
 131 {
 132         struct posix_acl *clone = NULL;
 133
 134         if (acl) {
 135                 int size = sizeof(struct posix_acl) + acl->a_count *
 136                            sizeof(struct posix_acl_entry);
 137                 clone = kmemdup(acl, size, flags);
 138                 if (clone)
 139                         atomic_set(&clone->a_refcount, 1);
 140         }
 141         return clone;
 142 }
 143
 144 /*
 145  * Check if an acl is valid. Returns 0 if it is, or -E... otherwise.
 146  */
 147 int
 148 posix_acl_valid(const struct posix_acl *acl)
 149 {
 150         const struct posix_acl_entry *pa, *pe;
 151         int state = ACL_USER_OBJ;
 152         kuid_t prev_uid = INVALID_UID;
 153         kgid_t prev_gid = INVALID_GID;
 154         int needs_mask = 0;
 155
 156         FOREACH_ACL_ENTRY(pa, acl, pe) {
 157                 if (pa->e_perm & ~(ACL_READ|ACL_WRITE|ACL_EXECUTE))
 158                         return -EINVAL;
 159                 switch (pa->e_tag) {
 160                         case ACL_USER_OBJ:
 161                                 if (state == ACL_USER_OBJ) {
 162                                         state = ACL_USER;
 163                                         break;
 164                                 }
 165                                 return -EINVAL;
 166
 167                         case ACL_USER:
 168                                 if (state != ACL_USER)
 169                                         return -EINVAL;
 170                                 if (!uid_valid(pa->e_uid))
 171                                         return -EINVAL;
 172                                 if (uid_valid(prev_uid) &&
 173                                     uid_lte(pa->e_uid, prev_uid))
 174                                         return -EINVAL;
 175                                 prev_uid = pa->e_uid;
 176                                 needs_mask = 1;
 177                                 break;
 178
 179                         case ACL_GROUP_OBJ:
 180                                 if (state == ACL_USER) {
 181                                         state = ACL_GROUP;
 182                                         break;
 183                                 }
 184                                 return -EINVAL;
 185
 186                         case ACL_GROUP:
 187                                 if (state != ACL_GROUP)
 188                                         return -EINVAL;
 189                                 if (!gid_valid(pa->e_gid))
 190                                         return -EINVAL;
 191                                 if (gid_valid(prev_gid) &&
 192                                     gid_lte(pa->e_gid, prev_gid))
 193                                         return -EINVAL;
 194                                 prev_gid = pa->e_gid;
 195                                 needs_mask = 1;
 196                                 break;
 197
 198                         case ACL_MASK:
 199                                 if (state != ACL_GROUP)
 200                                         return -EINVAL;
 201                                 state = ACL_OTHER;
 202                                 break;
 203
 204                         case ACL_OTHER:
 205                                 if (state == ACL_OTHER ||
 206                                     (state == ACL_GROUP && !needs_mask)) {
 207                                         state = 0;
 208                                         break;
 209                                 }
 210                                 return -EINVAL;
 211
 212                         default:
 213                                 return -EINVAL;
 214                 }
 215         }
 216         if (state == 0)
 217                 return 0;
 218         return -EINVAL;
 219 }
 220 EXPORT_SYMBOL(posix_acl_valid);
 221
 222 /*
 223  * Returns 0 if the acl can be exactly represented in the traditional
 224  * file mode permission bits, or else 1. Returns -E... on error.
 225  */
 226 int
 227 posix_acl_equiv_mode(const struct posix_acl *acl, umode_t *mode_p)
 228 {
 229         const struct posix_acl_entry *pa, *pe;
 230         umode_t mode = 0;
 231         int not_equiv = 0;
 232
 233         FOREACH_ACL_ENTRY(pa, acl, pe) {
 234                 switch (pa->e_tag) {
 235                         case ACL_USER_OBJ:
 236                                 mode |= (pa->e_perm & S_IRWXO) << 6;
 237                                 break;
 238                         case ACL_GROUP_OBJ:
 239                                 mode |= (pa->e_perm & S_IRWXO) << 3;
 240                                 break;
 241                         case ACL_OTHER:
 242                                 mode |= pa->e_perm & S_IRWXO;
 243                                 break;
 244                         case ACL_MASK:
 245                                 mode = (mode & ~S_IRWXG) |
 246                                        ((pa->e_perm & S_IRWXO) << 3);
 247                                 not_equiv = 1;
 248                                 break;
 249                         case ACL_USER:
 250                         case ACL_GROUP:
 251                                 not_equiv = 1;
 252                                 break;
 253                         default:
 254                                 return -EINVAL;
 255                 }
 256         }
 257         if (mode_p)
 258                 *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
 259         return not_equiv;
 260 }
 261 EXPORT_SYMBOL(posix_acl_equiv_mode);
 262
 263 /*
 264  * Create an ACL representing the file mode permission bits of an inode.
 265  */
 266 struct posix_acl *
 267 posix_acl_from_mode(umode_t mode, gfp_t flags)
 268 {
 269         struct posix_acl *acl = posix_acl_alloc(3, flags);
 270         if (!acl)
 271                 return ERR_PTR(-ENOMEM);
 272
 273         acl->a_entries[0].e_tag  = ACL_USER_OBJ;
 274         acl->a_entries[0].e_perm = (mode & S_IRWXU) >> 6;
 275
 276         acl->a_entries[1].e_tag  = ACL_GROUP_OBJ;
 277         acl->a_entries[1].e_perm = (mode & S_IRWXG) >> 3;
 278
 279         acl->a_entries[2].e_tag  = ACL_OTHER;
 280         acl->a_entries[2].e_perm = (mode & S_IRWXO);
 281         return acl;
 282 }
 283 EXPORT_SYMBOL(posix_acl_from_mode);
 284
 285 /*
 286  * Return 0 if current is granted want access to the inode
 287  * by the acl. Returns -E... otherwise.
 288  */
 289 int
 290 posix_acl_permission(struct inode *inode, const struct posix_acl *acl, int want)
 291 {
 292         const struct posix_acl_entry *pa, *pe, *mask_obj;
 293         int found = 0;
 294
 295         want &= MAY_READ | MAY_WRITE | MAY_EXEC | MAY_NOT_BLOCK;
 296
 297         FOREACH_ACL_ENTRY(pa, acl, pe) {
 298                 switch(pa->e_tag) {
 299                         case ACL_USER_OBJ:
 300                                 /* (May have been checked already) */
 301                                 if (uid_eq(inode->i_uid, current_fsuid()))
 302                                         goto check_perm;
 303                                 break;
 304                         case ACL_USER:
 305                                 if (uid_eq(pa->e_uid, current_fsuid()))
 306                                         goto mask;
 307                                 break;
 308                         case ACL_GROUP_OBJ:
 309                                 if (in_group_p(inode->i_gid)) {
 310                                         found = 1;
 311                                         if ((pa->e_perm & want) == want)
 312                                                 goto mask;
 313                                 }
 314                                 break;
 315                         case ACL_GROUP:
 316                                 if (in_group_p(pa->e_gid)) {
 317                                         found = 1;
 318                                         if ((pa->e_perm & want) == want)
 319                                                 goto mask;
 320                                 }
 321                                 break;
 322                         case ACL_MASK:
 323                                 break;
 324                         case ACL_OTHER:
 325                                 if (found)
 326                                         return -EACCES;
 327                                 else
 328                                         goto check_perm;
 329                         default:
 330                                 return -EIO;
 331                 }
 332         }
 333         return -EIO;
 334
 335 mask:
 336         for (mask_obj = pa+1; mask_obj != pe; mask_obj++) {
 337                 if (mask_obj->e_tag == ACL_MASK) {
 338                         if ((pa->e_perm & mask_obj->e_perm & want) == want)
 339                                 return 0;
 340                         return -EACCES;
 341                 }
 342         }
 343
 344 check_perm:
 345         if ((pa->e_perm & want) == want)
 346                 return 0;
 347         return -EACCES;
 348 }
 349
 350 /*
 351  * Modify acl when creating a new inode. The caller must ensure the acl is
 352  * only referenced once.
 353  *
 354  * mode_p initially must contain the mode parameter to the open() / creat()
 355  * system calls. All permissions that are not granted by the acl are removed.
 356  * The permissions in the acl are changed to reflect the mode_p parameter.
 357  */
 358 static int posix_acl_create_masq(struct posix_acl *acl, umode_t *mode_p)
 359 {
 360         struct posix_acl_entry *pa, *pe;
 361         struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
 362         umode_t mode = *mode_p;
 363         int not_equiv = 0;
 364
 365         /* assert(atomic_read(acl->a_refcount) == 1); */
 366
 367         FOREACH_ACL_ENTRY(pa, acl, pe) {
 368                 switch(pa->e_tag) {
 369                         case ACL_USER_OBJ:
 370                                 pa->e_perm &= (mode >> 6) | ~S_IRWXO;
 371                                 mode &= (pa->e_perm << 6) | ~S_IRWXU;
 372                                 break;
 373
 374                         case ACL_USER:
 375                         case ACL_GROUP:
 376                                 not_equiv = 1;
 377                                 break;
 378
 379                         case ACL_GROUP_OBJ:
 380                                 group_obj = pa;
 381                                 break;
 382
 383                         case ACL_OTHER:
 384                                 pa->e_perm &= mode | ~S_IRWXO;
 385                                 mode &= pa->e_perm | ~S_IRWXO;
 386                                 break;
 387
 388                         case ACL_MASK:
 389                                 mask_obj = pa;
 390                                 not_equiv = 1;
 391                                 break;
 392
 393                         default:
 394                                 return -EIO;
 395                 }
 396         }
 397
 398         if (mask_obj) {
 399                 mask_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
 400                 mode &= (mask_obj->e_perm << 3) | ~S_IRWXG;
 401         } else {
 402                 if (!group_obj)
 403                         return -EIO;
 404                 group_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
 405                 mode &= (group_obj->e_perm << 3) | ~S_IRWXG;
 406         }
 407
 408         *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
 409         return not_equiv;
 410 }
 411
 412 /*
 413  * Modify the ACL for the chmod syscall.
 414  */
 415 static int posix_acl_chmod_masq(struct posix_acl *acl, umode_t mode)
 416 {
 417         struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
 418         struct posix_acl_entry *pa, *pe;
 419
 420         /* assert(atomic_read(acl->a_refcount) == 1); */
 421
 422         FOREACH_ACL_ENTRY(pa, acl, pe) {
 423                 switch(pa->e_tag) {
 424                         case ACL_USER_OBJ:
 425                                 pa->e_perm = (mode & S_IRWXU) >> 6;
 426                                 break;
 427
 428                         case ACL_USER:
 429                         case ACL_GROUP:
 430                                 break;
 431
 432                         case ACL_GROUP_OBJ:
 433                                 group_obj = pa;
 434                                 break;
 435
 436                         case ACL_MASK:
 437                                 mask_obj = pa;
 438                                 break;
 439
 440                         case ACL_OTHER:
 441                                 pa->e_perm = (mode & S_IRWXO);
 442                                 break;
 443
 444                         default:
 445                                 return -EIO;
 446                 }
 447         }
 448
 449         if (mask_obj) {
 450                 mask_obj->e_perm = (mode & S_IRWXG) >> 3;
 451         } else {
 452                 if (!group_obj)
 453                         return -EIO;
 454                 group_obj->e_perm = (mode & S_IRWXG) >> 3;
 455         }
 456
 457         return 0;
 458 }
 459
 460 int
 461 posix_acl_create(struct posix_acl **acl, gfp_t gfp, umode_t *mode_p)
 462 {
 463         struct posix_acl *clone = posix_acl_clone(*acl, gfp);
 464         int err = -ENOMEM;
 465         if (clone) {
 466                 err = posix_acl_create_masq(clone, mode_p);
 467                 if (err < 0) {
 468                         posix_acl_release(clone);
 469                         clone = NULL;
 470                 }
 471         }
 472         posix_acl_release(*acl);
 473         *acl = clone;
 474         return err;
 475 }
 476 EXPORT_SYMBOL(posix_acl_create);
 477
 478 int
 479 posix_acl_chmod(struct posix_acl **acl, gfp_t gfp, umode_t mode)
 480 {
 481         struct posix_acl *clone = posix_acl_clone(*acl, gfp);
 482         int err = -ENOMEM;
 483         if (clone) {
 484                 err = posix_acl_chmod_masq(clone, mode);
 485                 if (err) {
 486                         posix_acl_release(clone);
 487                         clone = NULL;
 488                 }
 489         }
 490         posix_acl_release(*acl);
 491         *acl = clone;
 492         return err;
 493 }
 494 EXPORT_SYMBOL(posix_acl_chmod);