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