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         int needs_mask = 0;
 153
 154         FOREACH_ACL_ENTRY(pa, acl, pe) {
 155                 if (pa->e_perm & ~(ACL_READ|ACL_WRITE|ACL_EXECUTE))
 156                         return -EINVAL;
 157                 switch (pa->e_tag) {
 158                         case ACL_USER_OBJ:
 159                                 if (state == ACL_USER_OBJ) {
 160                                         state = ACL_USER;
 161                                         break;
 162                                 }
 163                                 return -EINVAL;
 164
 165                         case ACL_USER:
 166                                 if (state != ACL_USER)
 167                                         return -EINVAL;
 168                                 if (!uid_valid(pa->e_uid))
 169                                         return -EINVAL;
 170                                 needs_mask = 1;
 171                                 break;
 172
 173                         case ACL_GROUP_OBJ:
 174                                 if (state == ACL_USER) {
 175                                         state = ACL_GROUP;
 176                                         break;
 177                                 }
 178                                 return -EINVAL;
 179
 180                         case ACL_GROUP:
 181                                 if (state != ACL_GROUP)
 182                                         return -EINVAL;
 183                                 if (!gid_valid(pa->e_gid))
 184                                         return -EINVAL;
 185                                 needs_mask = 1;
 186                                 break;
 187
 188                         case ACL_MASK:
 189                                 if (state != ACL_GROUP)
 190                                         return -EINVAL;
 191                                 state = ACL_OTHER;
 192                                 break;
 193
 194                         case ACL_OTHER:
 195                                 if (state == ACL_OTHER ||
 196                                     (state == ACL_GROUP && !needs_mask)) {
 197                                         state = 0;
 198                                         break;
 199                                 }
 200                                 return -EINVAL;
 201
 202                         default:
 203                                 return -EINVAL;
 204                 }
 205         }
 206         if (state == 0)
 207                 return 0;
 208         return -EINVAL;
 209 }
 210 EXPORT_SYMBOL(posix_acl_valid);
 211
 212 /*
 213  * Returns 0 if the acl can be exactly represented in the traditional
 214  * file mode permission bits, or else 1. Returns -E... on error.
 215  */
 216 int
 217 posix_acl_equiv_mode(const struct posix_acl *acl, umode_t *mode_p)
 218 {
 219         const struct posix_acl_entry *pa, *pe;
 220         umode_t mode = 0;
 221         int not_equiv = 0;
 222
 223         FOREACH_ACL_ENTRY(pa, acl, pe) {
 224                 switch (pa->e_tag) {
 225                         case ACL_USER_OBJ:
 226                                 mode |= (pa->e_perm & S_IRWXO) << 6;
 227                                 break;
 228                         case ACL_GROUP_OBJ:
 229                                 mode |= (pa->e_perm & S_IRWXO) << 3;
 230                                 break;
 231                         case ACL_OTHER:
 232                                 mode |= pa->e_perm & S_IRWXO;
 233                                 break;
 234                         case ACL_MASK:
 235                                 mode = (mode & ~S_IRWXG) |
 236                                        ((pa->e_perm & S_IRWXO) << 3);
 237                                 not_equiv = 1;
 238                                 break;
 239                         case ACL_USER:
 240                         case ACL_GROUP:
 241                                 not_equiv = 1;
 242                                 break;
 243                         default:
 244                                 return -EINVAL;
 245                 }
 246         }
 247         if (mode_p)
 248                 *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
 249         return not_equiv;
 250 }
 251 EXPORT_SYMBOL(posix_acl_equiv_mode);
 252
 253 /*
 254  * Create an ACL representing the file mode permission bits of an inode.
 255  */
 256 struct posix_acl *
 257 posix_acl_from_mode(umode_t mode, gfp_t flags)
 258 {
 259         struct posix_acl *acl = posix_acl_alloc(3, flags);
 260         if (!acl)
 261                 return ERR_PTR(-ENOMEM);
 262
 263         acl->a_entries[0].e_tag  = ACL_USER_OBJ;
 264         acl->a_entries[0].e_perm = (mode & S_IRWXU) >> 6;
 265
 266         acl->a_entries[1].e_tag  = ACL_GROUP_OBJ;
 267         acl->a_entries[1].e_perm = (mode & S_IRWXG) >> 3;
 268
 269         acl->a_entries[2].e_tag  = ACL_OTHER;
 270         acl->a_entries[2].e_perm = (mode & S_IRWXO);
 271         return acl;
 272 }
 273 EXPORT_SYMBOL(posix_acl_from_mode);
 274
 275 /*
 276  * Return 0 if current is granted want access to the inode
 277  * by the acl. Returns -E... otherwise.
 278  */
 279 int
 280 posix_acl_permission(struct inode *inode, const struct posix_acl *acl, int want)
 281 {
 282         const struct posix_acl_entry *pa, *pe, *mask_obj;
 283         int found = 0;
 284
 285         want &= MAY_READ | MAY_WRITE | MAY_EXEC | MAY_NOT_BLOCK;
 286
 287         FOREACH_ACL_ENTRY(pa, acl, pe) {
 288                 switch(pa->e_tag) {
 289                         case ACL_USER_OBJ:
 290                                 /* (May have been checked already) */
 291                                 if (uid_eq(inode->i_uid, current_fsuid()))
 292                                         goto check_perm;
 293                                 break;
 294                         case ACL_USER:
 295                                 if (uid_eq(pa->e_uid, current_fsuid()))
 296                                         goto mask;
 297                                 break;
 298                         case ACL_GROUP_OBJ:
 299                                 if (in_group_p(inode->i_gid)) {
 300                                         found = 1;
 301                                         if ((pa->e_perm & want) == want)
 302                                                 goto mask;
 303                                 }
 304                                 break;
 305                         case ACL_GROUP:
 306                                 if (in_group_p(pa->e_gid)) {
 307                                         found = 1;
 308                                         if ((pa->e_perm & want) == want)
 309                                                 goto mask;
 310                                 }
 311                                 break;
 312                         case ACL_MASK:
 313                                 break;
 314                         case ACL_OTHER:
 315                                 if (found)
 316                                         return -EACCES;
 317                                 else
 318                                         goto check_perm;
 319                         default:
 320                                 return -EIO;
 321                 }
 322         }
 323         return -EIO;
 324
 325 mask:
 326         for (mask_obj = pa+1; mask_obj != pe; mask_obj++) {
 327                 if (mask_obj->e_tag == ACL_MASK) {
 328                         if ((pa->e_perm & mask_obj->e_perm & want) == want)
 329                                 return 0;
 330                         return -EACCES;
 331                 }
 332         }
 333
 334 check_perm:
 335         if ((pa->e_perm & want) == want)
 336                 return 0;
 337         return -EACCES;
 338 }
 339
 340 /*
 341  * Modify acl when creating a new inode. The caller must ensure the acl is
 342  * only referenced once.
 343  *
 344  * mode_p initially must contain the mode parameter to the open() / creat()
 345  * system calls. All permissions that are not granted by the acl are removed.
 346  * The permissions in the acl are changed to reflect the mode_p parameter.
 347  */
 348 static int posix_acl_create_masq(struct posix_acl *acl, umode_t *mode_p)
 349 {
 350         struct posix_acl_entry *pa, *pe;
 351         struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
 352         umode_t mode = *mode_p;
 353         int not_equiv = 0;
 354
 355         /* assert(atomic_read(acl->a_refcount) == 1); */
 356
 357         FOREACH_ACL_ENTRY(pa, acl, pe) {
 358                 switch(pa->e_tag) {
 359                         case ACL_USER_OBJ:
 360                                 pa->e_perm &= (mode >> 6) | ~S_IRWXO;
 361                                 mode &= (pa->e_perm << 6) | ~S_IRWXU;
 362                                 break;
 363
 364                         case ACL_USER:
 365                         case ACL_GROUP:
 366                                 not_equiv = 1;
 367                                 break;
 368
 369                         case ACL_GROUP_OBJ:
 370                                 group_obj = pa;
 371                                 break;
 372
 373                         case ACL_OTHER:
 374                                 pa->e_perm &= mode | ~S_IRWXO;
 375                                 mode &= pa->e_perm | ~S_IRWXO;
 376                                 break;
 377
 378                         case ACL_MASK:
 379                                 mask_obj = pa;
 380                                 not_equiv = 1;
 381                                 break;
 382
 383                         default:
 384                                 return -EIO;
 385                 }
 386         }
 387
 388         if (mask_obj) {
 389                 mask_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
 390                 mode &= (mask_obj->e_perm << 3) | ~S_IRWXG;
 391         } else {
 392                 if (!group_obj)
 393                         return -EIO;
 394                 group_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
 395                 mode &= (group_obj->e_perm << 3) | ~S_IRWXG;
 396         }
 397
 398         *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
 399         return not_equiv;
 400 }
 401
 402 /*
 403  * Modify the ACL for the chmod syscall.
 404  */
 405 static int posix_acl_chmod_masq(struct posix_acl *acl, umode_t mode)
 406 {
 407         struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
 408         struct posix_acl_entry *pa, *pe;
 409
 410         /* assert(atomic_read(acl->a_refcount) == 1); */
 411
 412         FOREACH_ACL_ENTRY(pa, acl, pe) {
 413                 switch(pa->e_tag) {
 414                         case ACL_USER_OBJ:
 415                                 pa->e_perm = (mode & S_IRWXU) >> 6;
 416                                 break;
 417
 418                         case ACL_USER:
 419                         case ACL_GROUP:
 420                                 break;
 421
 422                         case ACL_GROUP_OBJ:
 423                                 group_obj = pa;
 424                                 break;
 425
 426                         case ACL_MASK:
 427                                 mask_obj = pa;
 428                                 break;
 429
 430                         case ACL_OTHER:
 431                                 pa->e_perm = (mode & S_IRWXO);
 432                                 break;
 433
 434                         default:
 435                                 return -EIO;
 436                 }
 437         }
 438
 439         if (mask_obj) {
 440                 mask_obj->e_perm = (mode & S_IRWXG) >> 3;
 441         } else {
 442                 if (!group_obj)
 443                         return -EIO;
 444                 group_obj->e_perm = (mode & S_IRWXG) >> 3;
 445         }
 446
 447         return 0;
 448 }
 449
 450 int
 451 posix_acl_create(struct posix_acl **acl, gfp_t gfp, umode_t *mode_p)
 452 {
 453         struct posix_acl *clone = posix_acl_clone(*acl, gfp);
 454         int err = -ENOMEM;
 455         if (clone) {
 456                 err = posix_acl_create_masq(clone, mode_p);
 457                 if (err < 0) {
 458                         posix_acl_release(clone);
 459                         clone = NULL;
 460                 }
 461         }
 462         posix_acl_release(*acl);
 463         *acl = clone;
 464         return err;
 465 }
 466 EXPORT_SYMBOL(posix_acl_create);
 467
 468 int
 469 posix_acl_chmod(struct posix_acl **acl, gfp_t gfp, umode_t mode)
 470 {
 471         struct posix_acl *clone = posix_acl_clone(*acl, gfp);
 472         int err = -ENOMEM;
 473         if (clone) {
 474                 err = posix_acl_chmod_masq(clone, mode);
 475                 if (err) {
 476                         posix_acl_release(clone);
 477                         clone = NULL;
 478                 }
 479         }
 480         posix_acl_release(*acl);
 481         *acl = clone;
 482         return err;
 483 }
 484 EXPORT_SYMBOL(posix_acl_chmod);