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 <asm/atomic.h>
  18 #include <linux/fs.h>
  19 #include <linux/sched.h>
  20 #include <linux/posix_acl.h>
  21 #include <linux/module.h>
  22
  23 #include <linux/errno.h>
  24
  25 EXPORT_SYMBOL(posix_acl_init);
  26 EXPORT_SYMBOL(posix_acl_alloc);
  27 EXPORT_SYMBOL(posix_acl_clone);
  28 EXPORT_SYMBOL(posix_acl_valid);
  29 EXPORT_SYMBOL(posix_acl_equiv_mode);
  30 EXPORT_SYMBOL(posix_acl_from_mode);
  31 EXPORT_SYMBOL(posix_acl_create_masq);
  32 EXPORT_SYMBOL(posix_acl_chmod_masq);
  33 EXPORT_SYMBOL(posix_acl_permission);
  34
  35 /*
  36  * Init a fresh posix_acl
  37  */
  38 void
  39 posix_acl_init(struct posix_acl *acl, int count)
  40 {
  41         atomic_set(&acl->a_refcount, 1);
  42         acl->a_count = count;
  43 }
  44
  45 /*
  46  * Allocate a new ACL with the specified number of entries.
  47  */
  48 struct posix_acl *
  49 posix_acl_alloc(int count, gfp_t flags)
  50 {
  51         const size_t size = sizeof(struct posix_acl) +
  52                             count * sizeof(struct posix_acl_entry);
  53         struct posix_acl *acl = kmalloc(size, flags);
  54         if (acl)
  55                 posix_acl_init(acl, count);
  56         return acl;
  57 }
  58
  59 /*
  60  * Clone an ACL.
  61  */
  62 struct posix_acl *
  63 posix_acl_clone(const struct posix_acl *acl, gfp_t flags)
  64 {
  65         struct posix_acl *clone = NULL;
  66
  67         if (acl) {
  68                 int size = sizeof(struct posix_acl) + acl->a_count *
  69                            sizeof(struct posix_acl_entry);
  70                 clone = kmemdup(acl, size, flags);
  71                 if (clone)
  72                         atomic_set(&clone->a_refcount, 1);
  73         }
  74         return clone;
  75 }
  76
  77 /*
  78  * Check if an acl is valid. Returns 0 if it is, or -E... otherwise.
  79  */
  80 int
  81 posix_acl_valid(const struct posix_acl *acl)
  82 {
  83         const struct posix_acl_entry *pa, *pe;
  84         int state = ACL_USER_OBJ;
  85         unsigned int id = 0;  /* keep gcc happy */
  86         int needs_mask = 0;
  87
  88         FOREACH_ACL_ENTRY(pa, acl, pe) {
  89                 if (pa->e_perm & ~(ACL_READ|ACL_WRITE|ACL_EXECUTE))
  90                         return -EINVAL;
  91                 switch (pa->e_tag) {
  92                         case ACL_USER_OBJ:
  93                                 if (state == ACL_USER_OBJ) {
  94                                         id = 0;
  95                                         state = ACL_USER;
  96                                         break;
  97                                 }
  98                                 return -EINVAL;
  99
 100                         case ACL_USER:
 101                                 if (state != ACL_USER)
 102                                         return -EINVAL;
 103                                 if (pa->e_id == ACL_UNDEFINED_ID ||
 104                                     pa->e_id < id)
 105                                         return -EINVAL;
 106                                 id = pa->e_id + 1;
 107                                 needs_mask = 1;
 108                                 break;
 109
 110                         case ACL_GROUP_OBJ:
 111                                 if (state == ACL_USER) {
 112                                         id = 0;
 113                                         state = ACL_GROUP;
 114                                         break;
 115                                 }
 116                                 return -EINVAL;
 117
 118                         case ACL_GROUP:
 119                                 if (state != ACL_GROUP)
 120                                         return -EINVAL;
 121                                 if (pa->e_id == ACL_UNDEFINED_ID ||
 122                                     pa->e_id < id)
 123                                         return -EINVAL;
 124                                 id = pa->e_id + 1;
 125                                 needs_mask = 1;
 126                                 break;
 127
 128                         case ACL_MASK:
 129                                 if (state != ACL_GROUP)
 130                                         return -EINVAL;
 131                                 state = ACL_OTHER;
 132                                 break;
 133
 134                         case ACL_OTHER:
 135                                 if (state == ACL_OTHER ||
 136                                     (state == ACL_GROUP && !needs_mask)) {
 137                                         state = 0;
 138                                         break;
 139                                 }
 140                                 return -EINVAL;
 141
 142                         default:
 143                                 return -EINVAL;
 144                 }
 145         }
 146         if (state == 0)
 147                 return 0;
 148         return -EINVAL;
 149 }
 150
 151 /*
 152  * Returns 0 if the acl can be exactly represented in the traditional
 153  * file mode permission bits, or else 1. Returns -E... on error.
 154  */
 155 int
 156 posix_acl_equiv_mode(const struct posix_acl *acl, mode_t *mode_p)
 157 {
 158         const struct posix_acl_entry *pa, *pe;
 159         mode_t mode = 0;
 160         int not_equiv = 0;
 161
 162         FOREACH_ACL_ENTRY(pa, acl, pe) {
 163                 switch (pa->e_tag) {
 164                         case ACL_USER_OBJ:
 165                                 mode |= (pa->e_perm & S_IRWXO) << 6;
 166                                 break;
 167                         case ACL_GROUP_OBJ:
 168                                 mode |= (pa->e_perm & S_IRWXO) << 3;
 169                                 break;
 170                         case ACL_OTHER:
 171                                 mode |= pa->e_perm & S_IRWXO;
 172                                 break;
 173                         case ACL_MASK:
 174                                 mode = (mode & ~S_IRWXG) |
 175                                        ((pa->e_perm & S_IRWXO) << 3);
 176                                 not_equiv = 1;
 177                                 break;
 178                         case ACL_USER:
 179                         case ACL_GROUP:
 180                                 not_equiv = 1;
 181                                 break;
 182                         default:
 183                                 return -EINVAL;
 184                 }
 185         }
 186         if (mode_p)
 187                 *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
 188         return not_equiv;
 189 }
 190
 191 /*
 192  * Create an ACL representing the file mode permission bits of an inode.
 193  */
 194 struct posix_acl *
 195 posix_acl_from_mode(mode_t mode, gfp_t flags)
 196 {
 197         struct posix_acl *acl = posix_acl_alloc(3, flags);
 198         if (!acl)
 199                 return ERR_PTR(-ENOMEM);
 200
 201         acl->a_entries[0].e_tag  = ACL_USER_OBJ;
 202         acl->a_entries[0].e_id   = ACL_UNDEFINED_ID;
 203         acl->a_entries[0].e_perm = (mode & S_IRWXU) >> 6;
 204
 205         acl->a_entries[1].e_tag  = ACL_GROUP_OBJ;
 206         acl->a_entries[1].e_id   = ACL_UNDEFINED_ID;
 207         acl->a_entries[1].e_perm = (mode & S_IRWXG) >> 3;
 208
 209         acl->a_entries[2].e_tag  = ACL_OTHER;
 210         acl->a_entries[2].e_id   = ACL_UNDEFINED_ID;
 211         acl->a_entries[2].e_perm = (mode & S_IRWXO);
 212         return acl;
 213 }
 214
 215 /*
 216  * Return 0 if current is granted want access to the inode
 217  * by the acl. Returns -E... otherwise.
 218  */
 219 int
 220 posix_acl_permission(struct inode *inode, const struct posix_acl *acl, int want)
 221 {
 222         const struct posix_acl_entry *pa, *pe, *mask_obj;
 223         int found = 0;
 224
 225         FOREACH_ACL_ENTRY(pa, acl, pe) {
 226                 switch(pa->e_tag) {
 227                         case ACL_USER_OBJ:
 228                                 /* (May have been checked already) */
 229                                 if (inode->i_uid == current_fsuid())
 230                                         goto check_perm;
 231                                 break;
 232                         case ACL_USER:
 233                                 if (pa->e_id == current_fsuid())
 234                                         goto mask;
 235                                 break;
 236                         case ACL_GROUP_OBJ:
 237                                 if (in_group_p(inode->i_gid)) {
 238                                         found = 1;
 239                                         if ((pa->e_perm & want) == want)
 240                                                 goto mask;
 241                                 }
 242                                 break;
 243                         case ACL_GROUP:
 244                                 if (in_group_p(pa->e_id)) {
 245                                         found = 1;
 246                                         if ((pa->e_perm & want) == want)
 247                                                 goto mask;
 248                                 }
 249                                 break;
 250                         case ACL_MASK:
 251                                 break;
 252                         case ACL_OTHER:
 253                                 if (found)
 254                                         return -EACCES;
 255                                 else
 256                                         goto check_perm;
 257                         default:
 258                                 return -EIO;
 259                 }
 260         }
 261         return -EIO;
 262
 263 mask:
 264         for (mask_obj = pa+1; mask_obj != pe; mask_obj++) {
 265                 if (mask_obj->e_tag == ACL_MASK) {
 266                         if ((pa->e_perm & mask_obj->e_perm & want) == want)
 267                                 return 0;
 268                         return -EACCES;
 269                 }
 270         }
 271
 272 check_perm:
 273         if ((pa->e_perm & want) == want)
 274                 return 0;
 275         return -EACCES;
 276 }
 277
 278 /*
 279  * Modify acl when creating a new inode. The caller must ensure the acl is
 280  * only referenced once.
 281  *
 282  * mode_p initially must contain the mode parameter to the open() / creat()
 283  * system calls. All permissions that are not granted by the acl are removed.
 284  * The permissions in the acl are changed to reflect the mode_p parameter.
 285  */
 286 int
 287 posix_acl_create_masq(struct posix_acl *acl, mode_t *mode_p)
 288 {
 289         struct posix_acl_entry *pa, *pe;
 290         struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
 291         mode_t mode = *mode_p;
 292         int not_equiv = 0;
 293
 294         /* assert(atomic_read(acl->a_refcount) == 1); */
 295
 296         FOREACH_ACL_ENTRY(pa, acl, pe) {
 297                 switch(pa->e_tag) {
 298                         case ACL_USER_OBJ:
 299                                 pa->e_perm &= (mode >> 6) | ~S_IRWXO;
 300                                 mode &= (pa->e_perm << 6) | ~S_IRWXU;
 301                                 break;
 302
 303                         case ACL_USER:
 304                         case ACL_GROUP:
 305                                 not_equiv = 1;
 306                                 break;
 307
 308                         case ACL_GROUP_OBJ:
 309                                 group_obj = pa;
 310                                 break;
 311
 312                         case ACL_OTHER:
 313                                 pa->e_perm &= mode | ~S_IRWXO;
 314                                 mode &= pa->e_perm | ~S_IRWXO;
 315                                 break;
 316
 317                         case ACL_MASK:
 318                                 mask_obj = pa;
 319                                 not_equiv = 1;
 320                                 break;
 321
 322                         default:
 323                                 return -EIO;
 324                 }
 325         }
 326
 327         if (mask_obj) {
 328                 mask_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
 329                 mode &= (mask_obj->e_perm << 3) | ~S_IRWXG;
 330         } else {
 331                 if (!group_obj)
 332                         return -EIO;
 333                 group_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
 334                 mode &= (group_obj->e_perm << 3) | ~S_IRWXG;
 335         }
 336
 337         *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
 338         return not_equiv;
 339 }
 340
 341 /*
 342  * Modify the ACL for the chmod syscall.
 343  */
 344 int
 345 posix_acl_chmod_masq(struct posix_acl *acl, mode_t mode)
 346 {
 347         struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
 348         struct posix_acl_entry *pa, *pe;
 349
 350         /* assert(atomic_read(acl->a_refcount) == 1); */
 351
 352         FOREACH_ACL_ENTRY(pa, acl, pe) {
 353                 switch(pa->e_tag) {
 354                         case ACL_USER_OBJ:
 355                                 pa->e_perm = (mode & S_IRWXU) >> 6;
 356                                 break;
 357
 358                         case ACL_USER:
 359                         case ACL_GROUP:
 360                                 break;
 361
 362                         case ACL_GROUP_OBJ:
 363                                 group_obj = pa;
 364                                 break;
 365
 366                         case ACL_MASK:
 367                                 mask_obj = pa;
 368                                 break;
 369
 370                         case ACL_OTHER:
 371                                 pa->e_perm = (mode & S_IRWXO);
 372                                 break;
 373
 374                         default:
 375                                 return -EIO;
 376                 }
 377         }
 378
 379         if (mask_obj) {
 380                 mask_obj->e_perm = (mode & S_IRWXG) >> 3;
 381         } else {
 382                 if (!group_obj)
 383                         return -EIO;
 384                 group_obj->e_perm = (mode & S_IRWXG) >> 3;
 385         }
 386
 387         return 0;
 388 }