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   1 /* keyring.c: keyring handling
   2  *
   3  * Copyright (C) 2004-5 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  */
  11
  12 #include <linux/module.h>
  13 #include <linux/init.h>
  14 #include <linux/sched.h>
  15 #include <linux/slab.h>
  16 #include <linux/security.h>
  17 #include <linux/seq_file.h>
  18 #include <linux/err.h>
  19 #include <asm/uaccess.h>
  20 #include "internal.h"
  21
  22 /*
  23  * when plumbing the depths of the key tree, this sets a hard limit set on how
  24  * deep we're willing to go
  25  */
  26 #define KEYRING_SEARCH_MAX_DEPTH 6
  27
  28 /*
  29  * we keep all named keyrings in a hash to speed looking them up
  30  */
  31 #define KEYRING_NAME_HASH_SIZE  (1 << 5)
  32
  33 static struct list_head keyring_name_hash[KEYRING_NAME_HASH_SIZE];
  34 static DEFINE_RWLOCK(keyring_name_lock);
  35
  36 static inline unsigned keyring_hash(const char *desc)
  37 {
  38         unsigned bucket = 0;
  39
  40         for (; *desc; desc++)
  41                 bucket += (unsigned char) *desc;
  42
  43         return bucket & (KEYRING_NAME_HASH_SIZE - 1);
  44 }
  45
  46 /*
  47  * the keyring type definition
  48  */
  49 static int keyring_instantiate(struct key *keyring,
  50                                const void *data, size_t datalen);
  51 static int keyring_match(const struct key *keyring, const void *criterion);
  52 static void keyring_revoke(struct key *keyring);
  53 static void keyring_destroy(struct key *keyring);
  54 static void keyring_describe(const struct key *keyring, struct seq_file *m);
  55 static long keyring_read(const struct key *keyring,
  56                          char __user *buffer, size_t buflen);
  57
  58 struct key_type key_type_keyring = {
  59         .name           = "keyring",
  60         .def_datalen    = sizeof(struct keyring_list),
  61         .instantiate    = keyring_instantiate,
  62         .match          = keyring_match,
  63         .revoke         = keyring_revoke,
  64         .destroy        = keyring_destroy,
  65         .describe       = keyring_describe,
  66         .read           = keyring_read,
  67 };
  68
  69 EXPORT_SYMBOL(key_type_keyring);
  70
  71 /*
  72  * semaphore to serialise link/link calls to prevent two link calls in parallel
  73  * introducing a cycle
  74  */
  75 static DECLARE_RWSEM(keyring_serialise_link_sem);
  76
  77 /*****************************************************************************/
  78 /*
  79  * publish the name of a keyring so that it can be found by name (if it has
  80  * one)
  81  */
  82 void keyring_publish_name(struct key *keyring)
  83 {
  84         int bucket;
  85
  86         if (keyring->description) {
  87                 bucket = keyring_hash(keyring->description);
  88
  89                 write_lock(&keyring_name_lock);
  90
  91                 if (!keyring_name_hash[bucket].next)
  92                         INIT_LIST_HEAD(&keyring_name_hash[bucket]);
  93
  94                 list_add_tail(&keyring->type_data.link,
  95                               &keyring_name_hash[bucket]);
  96
  97                 write_unlock(&keyring_name_lock);
  98         }
  99
 100 } /* end keyring_publish_name() */
 101
 102 /*****************************************************************************/
 103 /*
 104  * initialise a keyring
 105  * - we object if we were given any data
 106  */
 107 static int keyring_instantiate(struct key *keyring,
 108                                const void *data, size_t datalen)
 109 {
 110         int ret;
 111
 112         ret = -EINVAL;
 113         if (datalen == 0) {
 114                 /* make the keyring available by name if it has one */
 115                 keyring_publish_name(keyring);
 116                 ret = 0;
 117         }
 118
 119         return ret;
 120
 121 } /* end keyring_instantiate() */
 122
 123 /*****************************************************************************/
 124 /*
 125  * match keyrings on their name
 126  */
 127 static int keyring_match(const struct key *keyring, const void *description)
 128 {
 129         return keyring->description &&
 130                 strcmp(keyring->description, description) == 0;
 131
 132 } /* end keyring_match() */
 133
 134 /*****************************************************************************/
 135 /*
 136  * dispose of the data dangling from the corpse of a keyring
 137  */
 138 static void keyring_destroy(struct key *keyring)
 139 {
 140         struct keyring_list *klist;
 141         int loop;
 142
 143         if (keyring->description) {
 144                 write_lock(&keyring_name_lock);
 145
 146                 if (keyring->type_data.link.next != NULL &&
 147                     !list_empty(&keyring->type_data.link))
 148                         list_del(&keyring->type_data.link);
 149
 150                 write_unlock(&keyring_name_lock);
 151         }
 152
 153         klist = rcu_dereference(keyring->payload.subscriptions);
 154         if (klist) {
 155                 for (loop = klist->nkeys - 1; loop >= 0; loop--)
 156                         key_put(klist->keys[loop]);
 157                 kfree(klist);
 158         }
 159
 160 } /* end keyring_destroy() */
 161
 162 /*****************************************************************************/
 163 /*
 164  * describe the keyring
 165  */
 166 static void keyring_describe(const struct key *keyring, struct seq_file *m)
 167 {
 168         struct keyring_list *klist;
 169
 170         if (keyring->description) {
 171                 seq_puts(m, keyring->description);
 172         }
 173         else {
 174                 seq_puts(m, "[anon]");
 175         }
 176
 177         rcu_read_lock();
 178         klist = rcu_dereference(keyring->payload.subscriptions);
 179         if (klist)
 180                 seq_printf(m, ": %u/%u", klist->nkeys, klist->maxkeys);
 181         else
 182                 seq_puts(m, ": empty");
 183         rcu_read_unlock();
 184
 185 } /* end keyring_describe() */
 186
 187 /*****************************************************************************/
 188 /*
 189  * read a list of key IDs from the keyring's contents
 190  * - the keyring's semaphore is read-locked
 191  */
 192 static long keyring_read(const struct key *keyring,
 193                          char __user *buffer, size_t buflen)
 194 {
 195         struct keyring_list *klist;
 196         struct key *key;
 197         size_t qty, tmp;
 198         int loop, ret;
 199
 200         ret = 0;
 201         klist = rcu_dereference(keyring->payload.subscriptions);
 202
 203         if (klist) {
 204                 /* calculate how much data we could return */
 205                 qty = klist->nkeys * sizeof(key_serial_t);
 206
 207                 if (buffer && buflen > 0) {
 208                         if (buflen > qty)
 209                                 buflen = qty;
 210
 211                         /* copy the IDs of the subscribed keys into the
 212                          * buffer */
 213                         ret = -EFAULT;
 214
 215                         for (loop = 0; loop < klist->nkeys; loop++) {
 216                                 key = klist->keys[loop];
 217
 218                                 tmp = sizeof(key_serial_t);
 219                                 if (tmp > buflen)
 220                                         tmp = buflen;
 221
 222                                 if (copy_to_user(buffer,
 223                                                  &key->serial,
 224                                                  tmp) != 0)
 225                                         goto error;
 226
 227                                 buflen -= tmp;
 228                                 if (buflen == 0)
 229                                         break;
 230                                 buffer += tmp;
 231                         }
 232                 }
 233
 234                 ret = qty;
 235         }
 236
 237  error:
 238         return ret;
 239
 240 } /* end keyring_read() */
 241
 242 /*****************************************************************************/
 243 /*
 244  * allocate a keyring and link into the destination keyring
 245  */
 246 struct key *keyring_alloc(const char *description, uid_t uid, gid_t gid,
 247                           struct task_struct *ctx, unsigned long flags,
 248                           struct key *dest)
 249 {
 250         struct key *keyring;
 251         int ret;
 252
 253         keyring = key_alloc(&key_type_keyring, description,
 254                             uid, gid, ctx,
 255                             (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL,
 256                             flags);
 257
 258         if (!IS_ERR(keyring)) {
 259                 ret = key_instantiate_and_link(keyring, NULL, 0, dest, NULL);
 260                 if (ret < 0) {
 261                         key_put(keyring);
 262                         keyring = ERR_PTR(ret);
 263                 }
 264         }
 265
 266         return keyring;
 267
 268 } /* end keyring_alloc() */
 269
 270 /*****************************************************************************/
 271 /*
 272  * search the supplied keyring tree for a key that matches the criterion
 273  * - perform a breadth-then-depth search up to the prescribed limit
 274  * - we only find keys on which we have search permission
 275  * - we use the supplied match function to see if the description (or other
 276  *   feature of interest) matches
 277  * - we rely on RCU to prevent the keyring lists from disappearing on us
 278  * - we return -EAGAIN if we didn't find any matching key
 279  * - we return -ENOKEY if we only found negative matching keys
 280  * - we propagate the possession attribute from the keyring ref to the key ref
 281  */
 282 key_ref_t keyring_search_aux(key_ref_t keyring_ref,
 283                              struct task_struct *context,
 284                              struct key_type *type,
 285                              const void *description,
 286                              key_match_func_t match)
 287 {
 288         struct {
 289                 struct keyring_list *keylist;
 290                 int kix;
 291         } stack[KEYRING_SEARCH_MAX_DEPTH];
 292
 293         struct keyring_list *keylist;
 294         struct timespec now;
 295         unsigned long possessed;
 296         struct key *keyring, *key;
 297         key_ref_t key_ref;
 298         long err;
 299         int sp, kix;
 300
 301         keyring = key_ref_to_ptr(keyring_ref);
 302         possessed = is_key_possessed(keyring_ref);
 303         key_check(keyring);
 304
 305         /* top keyring must have search permission to begin the search */
 306         err = key_task_permission(keyring_ref, context, KEY_SEARCH);
 307         if (err < 0) {
 308                 key_ref = ERR_PTR(err);
 309                 goto error;
 310         }
 311
 312         key_ref = ERR_PTR(-ENOTDIR);
 313         if (keyring->type != &key_type_keyring)
 314                 goto error;
 315
 316         rcu_read_lock();
 317
 318         now = current_kernel_time();
 319         err = -EAGAIN;
 320         sp = 0;
 321
 322         /* start processing a new keyring */
 323 descend:
 324         if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
 325                 goto not_this_keyring;
 326
 327         keylist = rcu_dereference(keyring->payload.subscriptions);
 328         if (!keylist)
 329                 goto not_this_keyring;
 330
 331         /* iterate through the keys in this keyring first */
 332         for (kix = 0; kix < keylist->nkeys; kix++) {
 333                 key = keylist->keys[kix];
 334
 335                 /* ignore keys not of this type */
 336                 if (key->type != type)
 337                         continue;
 338
 339                 /* skip revoked keys and expired keys */
 340                 if (test_bit(KEY_FLAG_REVOKED, &key->flags))
 341                         continue;
 342
 343                 if (key->expiry && now.tv_sec >= key->expiry)
 344                         continue;
 345
 346                 /* keys that don't match */
 347                 if (!match(key, description))
 348                         continue;
 349
 350                 /* key must have search permissions */
 351                 if (key_task_permission(make_key_ref(key, possessed),
 352                                         context, KEY_SEARCH) < 0)
 353                         continue;
 354
 355                 /* we set a different error code if we find a negative key */
 356                 if (test_bit(KEY_FLAG_NEGATIVE, &key->flags)) {
 357                         err = -ENOKEY;
 358                         continue;
 359                 }
 360
 361                 goto found;
 362         }
 363
 364         /* search through the keyrings nested in this one */
 365         kix = 0;
 366 ascend:
 367         for (; kix < keylist->nkeys; kix++) {
 368                 key = keylist->keys[kix];
 369                 if (key->type != &key_type_keyring)
 370                         continue;
 371
 372                 /* recursively search nested keyrings
 373                  * - only search keyrings for which we have search permission
 374                  */
 375                 if (sp >= KEYRING_SEARCH_MAX_DEPTH)
 376                         continue;
 377
 378                 if (key_task_permission(make_key_ref(key, possessed),
 379                                         context, KEY_SEARCH) < 0)
 380                         continue;
 381
 382                 /* stack the current position */
 383                 stack[sp].keylist = keylist;
 384                 stack[sp].kix = kix;
 385                 sp++;
 386
 387                 /* begin again with the new keyring */
 388                 keyring = key;
 389                 goto descend;
 390         }
 391
 392         /* the keyring we're looking at was disqualified or didn't contain a
 393          * matching key */
 394 not_this_keyring:
 395         if (sp > 0) {
 396                 /* resume the processing of a keyring higher up in the tree */
 397                 sp--;
 398                 keylist = stack[sp].keylist;
 399                 kix = stack[sp].kix + 1;
 400                 goto ascend;
 401         }
 402
 403         key_ref = ERR_PTR(err);
 404         goto error_2;
 405
 406         /* we found a viable match */
 407 found:
 408         atomic_inc(&key->usage);
 409         key_check(key);
 410         key_ref = make_key_ref(key, possessed);
 411 error_2:
 412         rcu_read_unlock();
 413 error:
 414         return key_ref;
 415
 416 } /* end keyring_search_aux() */
 417
 418 /*****************************************************************************/
 419 /*
 420  * search the supplied keyring tree for a key that matches the criterion
 421  * - perform a breadth-then-depth search up to the prescribed limit
 422  * - we only find keys on which we have search permission
 423  * - we readlock the keyrings as we search down the tree
 424  * - we return -EAGAIN if we didn't find any matching key
 425  * - we return -ENOKEY if we only found negative matching keys
 426  */
 427 key_ref_t keyring_search(key_ref_t keyring,
 428                          struct key_type *type,
 429                          const char *description)
 430 {
 431         if (!type->match)
 432                 return ERR_PTR(-ENOKEY);
 433
 434         return keyring_search_aux(keyring, current,
 435                                   type, description, type->match);
 436
 437 } /* end keyring_search() */
 438
 439 EXPORT_SYMBOL(keyring_search);
 440
 441 /*****************************************************************************/
 442 /*
 443  * search the given keyring only (no recursion)
 444  * - keyring must be locked by caller
 445  * - caller must guarantee that the keyring is a keyring
 446  */
 447 key_ref_t __keyring_search_one(key_ref_t keyring_ref,
 448                                const struct key_type *ktype,
 449                                const char *description,
 450                                key_perm_t perm)
 451 {
 452         struct keyring_list *klist;
 453         unsigned long possessed;
 454         struct key *keyring, *key;
 455         int loop;
 456
 457         keyring = key_ref_to_ptr(keyring_ref);
 458         possessed = is_key_possessed(keyring_ref);
 459
 460         rcu_read_lock();
 461
 462         klist = rcu_dereference(keyring->payload.subscriptions);
 463         if (klist) {
 464                 for (loop = 0; loop < klist->nkeys; loop++) {
 465                         key = klist->keys[loop];
 466
 467                         if (key->type == ktype &&
 468                             (!key->type->match ||
 469                              key->type->match(key, description)) &&
 470                             key_permission(make_key_ref(key, possessed),
 471                                            perm) == 0 &&
 472                             !test_bit(KEY_FLAG_REVOKED, &key->flags)
 473                             )
 474                                 goto found;
 475                 }
 476         }
 477
 478         rcu_read_unlock();
 479         return ERR_PTR(-ENOKEY);
 480
 481  found:
 482         atomic_inc(&key->usage);
 483         rcu_read_unlock();
 484         return make_key_ref(key, possessed);
 485
 486 } /* end __keyring_search_one() */
 487
 488 /*****************************************************************************/
 489 /*
 490  * find a keyring with the specified name
 491  * - all named keyrings are searched
 492  * - only find keyrings with search permission for the process
 493  * - only find keyrings with a serial number greater than the one specified
 494  */
 495 struct key *find_keyring_by_name(const char *name, key_serial_t bound)
 496 {
 497         struct key *keyring;
 498         int bucket;
 499
 500         keyring = ERR_PTR(-EINVAL);
 501         if (!name)
 502                 goto error;
 503
 504         bucket = keyring_hash(name);
 505
 506         read_lock(&keyring_name_lock);
 507
 508         if (keyring_name_hash[bucket].next) {
 509                 /* search this hash bucket for a keyring with a matching name
 510                  * that's readable and that hasn't been revoked */
 511                 list_for_each_entry(keyring,
 512                                     &keyring_name_hash[bucket],
 513                                     type_data.link
 514                                     ) {
 515                         if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
 516                                 continue;
 517
 518                         if (strcmp(keyring->description, name) != 0)
 519                                 continue;
 520
 521                         if (key_permission(make_key_ref(keyring, 0),
 522                                            KEY_SEARCH) < 0)
 523                                 continue;
 524
 525                         /* found a potential candidate, but we still need to
 526                          * check the serial number */
 527                         if (keyring->serial <= bound)
 528                                 continue;
 529
 530                         /* we've got a match */
 531                         atomic_inc(&keyring->usage);
 532                         read_unlock(&keyring_name_lock);
 533                         goto error;
 534                 }
 535         }
 536
 537         read_unlock(&keyring_name_lock);
 538         keyring = ERR_PTR(-ENOKEY);
 539
 540  error:
 541         return keyring;
 542
 543 } /* end find_keyring_by_name() */
 544
 545 /*****************************************************************************/
 546 /*
 547  * see if a cycle will will be created by inserting acyclic tree B in acyclic
 548  * tree A at the topmost level (ie: as a direct child of A)
 549  * - since we are adding B to A at the top level, checking for cycles should
 550  *   just be a matter of seeing if node A is somewhere in tree B
 551  */
 552 static int keyring_detect_cycle(struct key *A, struct key *B)
 553 {
 554         struct {
 555                 struct keyring_list *keylist;
 556                 int kix;
 557         } stack[KEYRING_SEARCH_MAX_DEPTH];
 558
 559         struct keyring_list *keylist;
 560         struct key *subtree, *key;
 561         int sp, kix, ret;
 562
 563         rcu_read_lock();
 564
 565         ret = -EDEADLK;
 566         if (A == B)
 567                 goto cycle_detected;
 568
 569         subtree = B;
 570         sp = 0;
 571
 572         /* start processing a new keyring */
 573  descend:
 574         if (test_bit(KEY_FLAG_REVOKED, &subtree->flags))
 575                 goto not_this_keyring;
 576
 577         keylist = rcu_dereference(subtree->payload.subscriptions);
 578         if (!keylist)
 579                 goto not_this_keyring;
 580         kix = 0;
 581
 582  ascend:
 583         /* iterate through the remaining keys in this keyring */
 584         for (; kix < keylist->nkeys; kix++) {
 585                 key = keylist->keys[kix];
 586
 587                 if (key == A)
 588                         goto cycle_detected;
 589
 590                 /* recursively check nested keyrings */
 591                 if (key->type == &key_type_keyring) {
 592                         if (sp >= KEYRING_SEARCH_MAX_DEPTH)
 593                                 goto too_deep;
 594
 595                         /* stack the current position */
 596                         stack[sp].keylist = keylist;
 597                         stack[sp].kix = kix;
 598                         sp++;
 599
 600                         /* begin again with the new keyring */
 601                         subtree = key;
 602                         goto descend;
 603                 }
 604         }
 605
 606         /* the keyring we're looking at was disqualified or didn't contain a
 607          * matching key */
 608  not_this_keyring:
 609         if (sp > 0) {
 610                 /* resume the checking of a keyring higher up in the tree */
 611                 sp--;
 612                 keylist = stack[sp].keylist;
 613                 kix = stack[sp].kix + 1;
 614                 goto ascend;
 615         }
 616
 617         ret = 0; /* no cycles detected */
 618
 619  error:
 620         rcu_read_unlock();
 621         return ret;
 622
 623  too_deep:
 624         ret = -ELOOP;
 625         goto error;
 626
 627  cycle_detected:
 628         ret = -EDEADLK;
 629         goto error;
 630
 631 } /* end keyring_detect_cycle() */
 632
 633 /*****************************************************************************/
 634 /*
 635  * dispose of a keyring list after the RCU grace period
 636  */
 637 static void keyring_link_rcu_disposal(struct rcu_head *rcu)
 638 {
 639         struct keyring_list *klist =
 640                 container_of(rcu, struct keyring_list, rcu);
 641
 642         kfree(klist);
 643
 644 } /* end keyring_link_rcu_disposal() */
 645
 646 /*****************************************************************************/
 647 /*
 648  * dispose of a keyring list after the RCU grace period, freeing the unlinked
 649  * key
 650  */
 651 static void keyring_unlink_rcu_disposal(struct rcu_head *rcu)
 652 {
 653         struct keyring_list *klist =
 654                 container_of(rcu, struct keyring_list, rcu);
 655
 656         key_put(klist->keys[klist->delkey]);
 657         kfree(klist);
 658
 659 } /* end keyring_unlink_rcu_disposal() */
 660
 661 /*****************************************************************************/
 662 /*
 663  * link a key into to a keyring
 664  * - must be called with the keyring's semaphore write-locked
 665  * - discard already extant link to matching key if there is one
 666  */
 667 int __key_link(struct key *keyring, struct key *key)
 668 {
 669         struct keyring_list *klist, *nklist;
 670         unsigned max;
 671         size_t size;
 672         int loop, ret;
 673
 674         ret = -EKEYREVOKED;
 675         if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
 676                 goto error;
 677
 678         ret = -ENOTDIR;
 679         if (keyring->type != &key_type_keyring)
 680                 goto error;
 681
 682         /* serialise link/link calls to prevent parallel calls causing a
 683          * cycle when applied to two keyring in opposite orders */
 684         down_write(&keyring_serialise_link_sem);
 685
 686         /* check that we aren't going to create a cycle adding one keyring to
 687          * another */
 688         if (key->type == &key_type_keyring) {
 689                 ret = keyring_detect_cycle(keyring, key);
 690                 if (ret < 0)
 691                         goto error2;
 692         }
 693
 694         /* see if there's a matching key we can displace */
 695         klist = keyring->payload.subscriptions;
 696
 697         if (klist && klist->nkeys > 0) {
 698                 struct key_type *type = key->type;
 699
 700                 for (loop = klist->nkeys - 1; loop >= 0; loop--) {
 701                         if (klist->keys[loop]->type == type &&
 702                             strcmp(klist->keys[loop]->description,
 703                                    key->description) == 0
 704                             ) {
 705                                 /* found a match - replace with new key */
 706                                 size = sizeof(struct key *) * klist->maxkeys;
 707                                 size += sizeof(*klist);
 708                                 BUG_ON(size > PAGE_SIZE);
 709
 710                                 ret = -ENOMEM;
 711                                 nklist = kmemdup(klist, size, GFP_KERNEL);
 712                                 if (!nklist)
 713                                         goto error2;
 714
 715                                 /* replace matched key */
 716                                 atomic_inc(&key->usage);
 717                                 nklist->keys[loop] = key;
 718
 719                                 rcu_assign_pointer(
 720                                         keyring->payload.subscriptions,
 721                                         nklist);
 722
 723                                 /* dispose of the old keyring list and the
 724                                  * displaced key */
 725                                 klist->delkey = loop;
 726                                 call_rcu(&klist->rcu,
 727                                          keyring_unlink_rcu_disposal);
 728
 729                                 goto done;
 730                         }
 731                 }
 732         }
 733
 734         /* check that we aren't going to overrun the user's quota */
 735         ret = key_payload_reserve(keyring,
 736                                   keyring->datalen + KEYQUOTA_LINK_BYTES);
 737         if (ret < 0)
 738                 goto error2;
 739
 740         klist = keyring->payload.subscriptions;
 741
 742         if (klist && klist->nkeys < klist->maxkeys) {
 743                 /* there's sufficient slack space to add directly */
 744                 atomic_inc(&key->usage);
 745
 746                 klist->keys[klist->nkeys] = key;
 747                 smp_wmb();
 748                 klist->nkeys++;
 749                 smp_wmb();
 750         }
 751         else {
 752                 /* grow the key list */
 753                 max = 4;
 754                 if (klist)
 755                         max += klist->maxkeys;
 756
 757                 ret = -ENFILE;
 758                 if (max > 65535)
 759                         goto error3;
 760                 size = sizeof(*klist) + sizeof(struct key *) * max;
 761                 if (size > PAGE_SIZE)
 762                         goto error3;
 763
 764                 ret = -ENOMEM;
 765                 nklist = kmalloc(size, GFP_KERNEL);
 766                 if (!nklist)
 767                         goto error3;
 768                 nklist->maxkeys = max;
 769                 nklist->nkeys = 0;
 770
 771                 if (klist) {
 772                         nklist->nkeys = klist->nkeys;
 773                         memcpy(nklist->keys,
 774                                klist->keys,
 775                                sizeof(struct key *) * klist->nkeys);
 776                 }
 777
 778                 /* add the key into the new space */
 779                 atomic_inc(&key->usage);
 780                 nklist->keys[nklist->nkeys++] = key;
 781
 782                 rcu_assign_pointer(keyring->payload.subscriptions, nklist);
 783
 784                 /* dispose of the old keyring list */
 785                 if (klist)
 786                         call_rcu(&klist->rcu, keyring_link_rcu_disposal);
 787         }
 788
 789 done:
 790         ret = 0;
 791 error2:
 792         up_write(&keyring_serialise_link_sem);
 793 error:
 794         return ret;
 795
 796 error3:
 797         /* undo the quota changes */
 798         key_payload_reserve(keyring,
 799                             keyring->datalen - KEYQUOTA_LINK_BYTES);
 800         goto error2;
 801
 802 } /* end __key_link() */
 803
 804 /*****************************************************************************/
 805 /*
 806  * link a key to a keyring
 807  */
 808 int key_link(struct key *keyring, struct key *key)
 809 {
 810         int ret;
 811
 812         key_check(keyring);
 813         key_check(key);
 814
 815         down_write(&keyring->sem);
 816         ret = __key_link(keyring, key);
 817         up_write(&keyring->sem);
 818
 819         return ret;
 820
 821 } /* end key_link() */
 822
 823 EXPORT_SYMBOL(key_link);
 824
 825 /*****************************************************************************/
 826 /*
 827  * unlink the first link to a key from a keyring
 828  */
 829 int key_unlink(struct key *keyring, struct key *key)
 830 {
 831         struct keyring_list *klist, *nklist;
 832         int loop, ret;
 833
 834         key_check(keyring);
 835         key_check(key);
 836
 837         ret = -ENOTDIR;
 838         if (keyring->type != &key_type_keyring)
 839                 goto error;
 840
 841         down_write(&keyring->sem);
 842
 843         klist = keyring->payload.subscriptions;
 844         if (klist) {
 845                 /* search the keyring for the key */
 846                 for (loop = 0; loop < klist->nkeys; loop++)
 847                         if (klist->keys[loop] == key)
 848                                 goto key_is_present;
 849         }
 850
 851         up_write(&keyring->sem);
 852         ret = -ENOENT;
 853         goto error;
 854
 855 key_is_present:
 856         /* we need to copy the key list for RCU purposes */
 857         nklist = kmalloc(sizeof(*klist) +
 858                          sizeof(struct key *) * klist->maxkeys,
 859                          GFP_KERNEL);
 860         if (!nklist)
 861                 goto nomem;
 862         nklist->maxkeys = klist->maxkeys;
 863         nklist->nkeys = klist->nkeys - 1;
 864
 865         if (loop > 0)
 866                 memcpy(&nklist->keys[0],
 867                        &klist->keys[0],
 868                        loop * sizeof(struct key *));
 869
 870         if (loop < nklist->nkeys)
 871                 memcpy(&nklist->keys[loop],
 872                        &klist->keys[loop + 1],
 873                        (nklist->nkeys - loop) * sizeof(struct key *));
 874
 875         /* adjust the user's quota */
 876         key_payload_reserve(keyring,
 877                             keyring->datalen - KEYQUOTA_LINK_BYTES);
 878
 879         rcu_assign_pointer(keyring->payload.subscriptions, nklist);
 880
 881         up_write(&keyring->sem);
 882
 883         /* schedule for later cleanup */
 884         klist->delkey = loop;
 885         call_rcu(&klist->rcu, keyring_unlink_rcu_disposal);
 886
 887         ret = 0;
 888
 889 error:
 890         return ret;
 891 nomem:
 892         ret = -ENOMEM;
 893         up_write(&keyring->sem);
 894         goto error;
 895
 896 } /* end key_unlink() */
 897
 898 EXPORT_SYMBOL(key_unlink);
 899
 900 /*****************************************************************************/
 901 /*
 902  * dispose of a keyring list after the RCU grace period, releasing the keys it
 903  * links to
 904  */
 905 static void keyring_clear_rcu_disposal(struct rcu_head *rcu)
 906 {
 907         struct keyring_list *klist;
 908         int loop;
 909
 910         klist = container_of(rcu, struct keyring_list, rcu);
 911
 912         for (loop = klist->nkeys - 1; loop >= 0; loop--)
 913                 key_put(klist->keys[loop]);
 914
 915         kfree(klist);
 916
 917 } /* end keyring_clear_rcu_disposal() */
 918
 919 /*****************************************************************************/
 920 /*
 921  * clear the specified process keyring
 922  * - implements keyctl(KEYCTL_CLEAR)
 923  */
 924 int keyring_clear(struct key *keyring)
 925 {
 926         struct keyring_list *klist;
 927         int ret;
 928
 929         ret = -ENOTDIR;
 930         if (keyring->type == &key_type_keyring) {
 931                 /* detach the pointer block with the locks held */
 932                 down_write(&keyring->sem);
 933
 934                 klist = keyring->payload.subscriptions;
 935                 if (klist) {
 936                         /* adjust the quota */
 937                         key_payload_reserve(keyring,
 938                                             sizeof(struct keyring_list));
 939
 940                         rcu_assign_pointer(keyring->payload.subscriptions,
 941                                            NULL);
 942                 }
 943
 944                 up_write(&keyring->sem);
 945
 946                 /* free the keys after the locks have been dropped */
 947                 if (klist)
 948                         call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
 949
 950                 ret = 0;
 951         }
 952
 953         return ret;
 954
 955 } /* end keyring_clear() */
 956
 957 EXPORT_SYMBOL(keyring_clear);
 958
 959 /*****************************************************************************/
 960 /*
 961  * dispose of the links from a revoked keyring
 962  * - called with the key sem write-locked
 963  */
 964 static void keyring_revoke(struct key *keyring)
 965 {
 966         struct keyring_list *klist = keyring->payload.subscriptions;
 967
 968         /* adjust the quota */
 969         key_payload_reserve(keyring, 0);
 970
 971         if (klist) {
 972                 rcu_assign_pointer(keyring->payload.subscriptions, NULL);
 973                 call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
 974         }
 975
 976 } /* end keyring_revoke() */