security/keys/key.c

   1 /* key.c: basic authentication token and access key management
   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/workqueue.h>
  17 #include <linux/err.h>
  18 #include "internal.h"
  19
  20 static kmem_cache_t     *key_jar;
  21 static key_serial_t     key_serial_next = 3;
  22 struct rb_root          key_serial_tree; /* tree of keys indexed by serial */
  23 DEFINE_SPINLOCK(key_serial_lock);
  24
  25 struct rb_root  key_user_tree; /* tree of quota records indexed by UID */
  26 DEFINE_SPINLOCK(key_user_lock);
  27
  28 static LIST_HEAD(key_types_list);
  29 static DECLARE_RWSEM(key_types_sem);
  30
  31 static void key_cleanup(void *data);
  32 static DECLARE_WORK(key_cleanup_task, key_cleanup, NULL);
  33
  34 /* we serialise key instantiation and link */
  35 DECLARE_RWSEM(key_construction_sem);
  36
  37 /* any key who's type gets unegistered will be re-typed to this */
  38 struct key_type key_type_dead = {
  39         .name           = "dead",
  40 };
  41
  42 #ifdef KEY_DEBUGGING
  43 void __key_check(const struct key *key)
  44 {
  45         printk("__key_check: key %p {%08x} should be {%08x}\n",
  46                key, key->magic, KEY_DEBUG_MAGIC);
  47         BUG();
  48 }
  49 #endif
  50
  51 /*****************************************************************************/
  52 /*
  53  * get the key quota record for a user, allocating a new record if one doesn't
  54  * already exist
  55  */
  56 struct key_user *key_user_lookup(uid_t uid)
  57 {
  58         struct key_user *candidate = NULL, *user;
  59         struct rb_node *parent = NULL;
  60         struct rb_node **p;
  61
  62  try_again:
  63         p = &key_user_tree.rb_node;
  64         spin_lock(&key_user_lock);
  65
  66         /* search the tree for a user record with a matching UID */
  67         while (*p) {
  68                 parent = *p;
  69                 user = rb_entry(parent, struct key_user, node);
  70
  71                 if (uid < user->uid)
  72                         p = &(*p)->rb_left;
  73                 else if (uid > user->uid)
  74                         p = &(*p)->rb_right;
  75                 else
  76                         goto found;
  77         }
  78
  79         /* if we get here, we failed to find a match in the tree */
  80         if (!candidate) {
  81                 /* allocate a candidate user record if we don't already have
  82                  * one */
  83                 spin_unlock(&key_user_lock);
  84
  85                 user = NULL;
  86                 candidate = kmalloc(sizeof(struct key_user), GFP_KERNEL);
  87                 if (unlikely(!candidate))
  88                         goto out;
  89
  90                 /* the allocation may have scheduled, so we need to repeat the
  91                  * search lest someone else added the record whilst we were
  92                  * asleep */
  93                 goto try_again;
  94         }
  95
  96         /* if we get here, then the user record still hadn't appeared on the
  97          * second pass - so we use the candidate record */
  98         atomic_set(&candidate->usage, 1);
  99         atomic_set(&candidate->nkeys, 0);
 100         atomic_set(&candidate->nikeys, 0);
 101         candidate->uid = uid;
 102         candidate->qnkeys = 0;
 103         candidate->qnbytes = 0;
 104         spin_lock_init(&candidate->lock);
 105         INIT_LIST_HEAD(&candidate->consq);
 106
 107         rb_link_node(&candidate->node, parent, p);
 108         rb_insert_color(&candidate->node, &key_user_tree);
 109         spin_unlock(&key_user_lock);
 110         user = candidate;
 111         goto out;
 112
 113         /* okay - we found a user record for this UID */
 114  found:
 115         atomic_inc(&user->usage);
 116         spin_unlock(&key_user_lock);
 117         if (candidate)
 118                 kfree(candidate);
 119  out:
 120         return user;
 121
 122 } /* end key_user_lookup() */
 123
 124 /*****************************************************************************/
 125 /*
 126  * dispose of a user structure
 127  */
 128 void key_user_put(struct key_user *user)
 129 {
 130         if (atomic_dec_and_lock(&user->usage, &key_user_lock)) {
 131                 rb_erase(&user->node, &key_user_tree);
 132                 spin_unlock(&key_user_lock);
 133
 134                 kfree(user);
 135         }
 136
 137 } /* end key_user_put() */
 138
 139 /*****************************************************************************/
 140 /*
 141  * insert a key with a fixed serial number
 142  */
 143 static void __init __key_insert_serial(struct key *key)
 144 {
 145         struct rb_node *parent, **p;
 146         struct key *xkey;
 147
 148         parent = NULL;
 149         p = &key_serial_tree.rb_node;
 150
 151         while (*p) {
 152                 parent = *p;
 153                 xkey = rb_entry(parent, struct key, serial_node);
 154
 155                 if (key->serial < xkey->serial)
 156                         p = &(*p)->rb_left;
 157                 else if (key->serial > xkey->serial)
 158                         p = &(*p)->rb_right;
 159                 else
 160                         BUG();
 161         }
 162
 163         /* we've found a suitable hole - arrange for this key to occupy it */
 164         rb_link_node(&key->serial_node, parent, p);
 165         rb_insert_color(&key->serial_node, &key_serial_tree);
 166
 167 } /* end __key_insert_serial() */
 168
 169 /*****************************************************************************/
 170 /*
 171  * assign a key the next unique serial number
 172  * - we work through all the serial numbers between 2 and 2^31-1 in turn and
 173  *   then wrap
 174  */
 175 static inline void key_alloc_serial(struct key *key)
 176 {
 177         struct rb_node *parent, **p;
 178         struct key *xkey;
 179
 180         spin_lock(&key_serial_lock);
 181
 182         /* propose a likely serial number and look for a hole for it in the
 183          * serial number tree */
 184         key->serial = key_serial_next;
 185         if (key->serial < 3)
 186                 key->serial = 3;
 187         key_serial_next = key->serial + 1;
 188
 189         parent = NULL;
 190         p = &key_serial_tree.rb_node;
 191
 192         while (*p) {
 193                 parent = *p;
 194                 xkey = rb_entry(parent, struct key, serial_node);
 195
 196                 if (key->serial < xkey->serial)
 197                         p = &(*p)->rb_left;
 198                 else if (key->serial > xkey->serial)
 199                         p = &(*p)->rb_right;
 200                 else
 201                         goto serial_exists;
 202         }
 203         goto insert_here;
 204
 205         /* we found a key with the proposed serial number - walk the tree from
 206          * that point looking for the next unused serial number */
 207  serial_exists:
 208         for (;;) {
 209                 key->serial = key_serial_next;
 210                 if (key->serial < 2)
 211                         key->serial = 2;
 212                 key_serial_next = key->serial + 1;
 213
 214                 if (!parent->rb_parent)
 215                         p = &key_serial_tree.rb_node;
 216                 else if (parent->rb_parent->rb_left == parent)
 217                         p = &parent->rb_parent->rb_left;
 218                 else
 219                         p = &parent->rb_parent->rb_right;
 220
 221                 parent = rb_next(parent);
 222                 if (!parent)
 223                         break;
 224
 225                 xkey = rb_entry(parent, struct key, serial_node);
 226                 if (key->serial < xkey->serial)
 227                         goto insert_here;
 228         }
 229
 230         /* we've found a suitable hole - arrange for this key to occupy it */
 231  insert_here:
 232         rb_link_node(&key->serial_node, parent, p);
 233         rb_insert_color(&key->serial_node, &key_serial_tree);
 234
 235         spin_unlock(&key_serial_lock);
 236
 237 } /* end key_alloc_serial() */
 238
 239 /*****************************************************************************/
 240 /*
 241  * allocate a key of the specified type
 242  * - update the user's quota to reflect the existence of the key
 243  * - called from a key-type operation with key_types_sem read-locked by either
 244  *   key_create_or_update() or by key_duplicate(); this prevents unregistration
 245  *   of the key type
 246  * - upon return the key is as yet uninstantiated; the caller needs to either
 247  *   instantiate the key or discard it before returning
 248  */
 249 struct key *key_alloc(struct key_type *type, const char *desc,
 250                       uid_t uid, gid_t gid, key_perm_t perm,
 251                       int not_in_quota)
 252 {
 253         struct key_user *user = NULL;
 254         struct key *key;
 255         size_t desclen, quotalen;
 256
 257         key = ERR_PTR(-EINVAL);
 258         if (!desc || !*desc)
 259                 goto error;
 260
 261         desclen = strlen(desc) + 1;
 262         quotalen = desclen + type->def_datalen;
 263
 264         /* get hold of the key tracking for this user */
 265         user = key_user_lookup(uid);
 266         if (!user)
 267                 goto no_memory_1;
 268
 269         /* check that the user's quota permits allocation of another key and
 270          * its description */
 271         if (!not_in_quota) {
 272                 spin_lock(&user->lock);
 273                 if (user->qnkeys + 1 >= KEYQUOTA_MAX_KEYS &&
 274                     user->qnbytes + quotalen >= KEYQUOTA_MAX_BYTES
 275                     )
 276                         goto no_quota;
 277
 278                 user->qnkeys++;
 279                 user->qnbytes += quotalen;
 280                 spin_unlock(&user->lock);
 281         }
 282
 283         /* allocate and initialise the key and its description */
 284         key = kmem_cache_alloc(key_jar, SLAB_KERNEL);
 285         if (!key)
 286                 goto no_memory_2;
 287
 288         if (desc) {
 289                 key->description = kmalloc(desclen, GFP_KERNEL);
 290                 if (!key->description)
 291                         goto no_memory_3;
 292
 293                 memcpy(key->description, desc, desclen);
 294         }
 295
 296         atomic_set(&key->usage, 1);
 297         init_rwsem(&key->sem);
 298         key->type = type;
 299         key->user = user;
 300         key->quotalen = quotalen;
 301         key->datalen = type->def_datalen;
 302         key->uid = uid;
 303         key->gid = gid;
 304         key->perm = perm;
 305         key->flags = 0;
 306         key->expiry = 0;
 307         key->payload.data = NULL;
 308
 309         if (!not_in_quota)
 310                 key->flags |= 1 << KEY_FLAG_IN_QUOTA;
 311
 312         memset(&key->type_data, 0, sizeof(key->type_data));
 313
 314 #ifdef KEY_DEBUGGING
 315         key->magic = KEY_DEBUG_MAGIC;
 316 #endif
 317
 318         /* publish the key by giving it a serial number */
 319         atomic_inc(&user->nkeys);
 320         key_alloc_serial(key);
 321
 322  error:
 323         return key;
 324
 325  no_memory_3:
 326         kmem_cache_free(key_jar, key);
 327  no_memory_2:
 328         if (!not_in_quota) {
 329                 spin_lock(&user->lock);
 330                 user->qnkeys--;
 331                 user->qnbytes -= quotalen;
 332                 spin_unlock(&user->lock);
 333         }
 334         key_user_put(user);
 335  no_memory_1:
 336         key = ERR_PTR(-ENOMEM);
 337         goto error;
 338
 339  no_quota:
 340         spin_unlock(&user->lock);
 341         key_user_put(user);
 342         key = ERR_PTR(-EDQUOT);
 343         goto error;
 344
 345 } /* end key_alloc() */
 346
 347 EXPORT_SYMBOL(key_alloc);
 348
 349 /*****************************************************************************/
 350 /*
 351  * reserve an amount of quota for the key's payload
 352  */
 353 int key_payload_reserve(struct key *key, size_t datalen)
 354 {
 355         int delta = (int) datalen - key->datalen;
 356         int ret = 0;
 357
 358         key_check(key);
 359
 360         /* contemplate the quota adjustment */
 361         if (delta != 0 && test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
 362                 spin_lock(&key->user->lock);
 363
 364                 if (delta > 0 &&
 365                     key->user->qnbytes + delta > KEYQUOTA_MAX_BYTES
 366                     ) {
 367                         ret = -EDQUOT;
 368                 }
 369                 else {
 370                         key->user->qnbytes += delta;
 371                         key->quotalen += delta;
 372                 }
 373                 spin_unlock(&key->user->lock);
 374         }
 375
 376         /* change the recorded data length if that didn't generate an error */
 377         if (ret == 0)
 378                 key->datalen = datalen;
 379
 380         return ret;
 381
 382 } /* end key_payload_reserve() */
 383
 384 EXPORT_SYMBOL(key_payload_reserve);
 385
 386 /*****************************************************************************/
 387 /*
 388  * instantiate a key and link it into the target keyring atomically
 389  * - called with the target keyring's semaphore writelocked
 390  */
 391 static int __key_instantiate_and_link(struct key *key,
 392                                       const void *data,
 393                                       size_t datalen,
 394                                       struct key *keyring,
 395                                       struct key *instkey)
 396 {
 397         int ret, awaken;
 398
 399         key_check(key);
 400         key_check(keyring);
 401
 402         awaken = 0;
 403         ret = -EBUSY;
 404
 405         down_write(&key_construction_sem);
 406
 407         /* can't instantiate twice */
 408         if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
 409                 /* instantiate the key */
 410                 ret = key->type->instantiate(key, data, datalen);
 411
 412                 if (ret == 0) {
 413                         /* mark the key as being instantiated */
 414                         atomic_inc(&key->user->nikeys);
 415                         set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
 416
 417                         if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
 418                                 awaken = 1;
 419
 420                         /* and link it into the destination keyring */
 421                         if (keyring)
 422                                 ret = __key_link(keyring, key);
 423
 424                         /* disable the authorisation key */
 425                         if (instkey)
 426                                 key_revoke(instkey);
 427                 }
 428         }
 429
 430         up_write(&key_construction_sem);
 431
 432         /* wake up anyone waiting for a key to be constructed */
 433         if (awaken)
 434                 wake_up_all(&request_key_conswq);
 435
 436         return ret;
 437
 438 } /* end __key_instantiate_and_link() */
 439
 440 /*****************************************************************************/
 441 /*
 442  * instantiate a key and link it into the target keyring atomically
 443  */
 444 int key_instantiate_and_link(struct key *key,
 445                              const void *data,
 446                              size_t datalen,
 447                              struct key *keyring,
 448                              struct key *instkey)
 449 {
 450         int ret;
 451
 452         if (keyring)
 453                 down_write(&keyring->sem);
 454
 455         ret = __key_instantiate_and_link(key, data, datalen, keyring, instkey);
 456
 457         if (keyring)
 458                 up_write(&keyring->sem);
 459
 460         return ret;
 461
 462 } /* end key_instantiate_and_link() */
 463
 464 EXPORT_SYMBOL(key_instantiate_and_link);
 465
 466 /*****************************************************************************/
 467 /*
 468  * negatively instantiate a key and link it into the target keyring atomically
 469  */
 470 int key_negate_and_link(struct key *key,
 471                         unsigned timeout,
 472                         struct key *keyring,
 473                         struct key *instkey)
 474 {
 475         struct timespec now;
 476         int ret, awaken;
 477
 478         key_check(key);
 479         key_check(keyring);
 480
 481         awaken = 0;
 482         ret = -EBUSY;
 483
 484         if (keyring)
 485                 down_write(&keyring->sem);
 486
 487         down_write(&key_construction_sem);
 488
 489         /* can't instantiate twice */
 490         if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
 491                 /* mark the key as being negatively instantiated */
 492                 atomic_inc(&key->user->nikeys);
 493                 set_bit(KEY_FLAG_NEGATIVE, &key->flags);
 494                 set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
 495                 now = current_kernel_time();
 496                 key->expiry = now.tv_sec + timeout;
 497
 498                 if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
 499                         awaken = 1;
 500
 501                 ret = 0;
 502
 503                 /* and link it into the destination keyring */
 504                 if (keyring)
 505                         ret = __key_link(keyring, key);
 506
 507                 /* disable the authorisation key */
 508                 if (instkey)
 509                         key_revoke(instkey);
 510         }
 511
 512         up_write(&key_construction_sem);
 513
 514         if (keyring)
 515                 up_write(&keyring->sem);
 516
 517         /* wake up anyone waiting for a key to be constructed */
 518         if (awaken)
 519                 wake_up_all(&request_key_conswq);
 520
 521         return ret;
 522
 523 } /* end key_negate_and_link() */
 524
 525 EXPORT_SYMBOL(key_negate_and_link);
 526
 527 /*****************************************************************************/
 528 /*
 529  * do cleaning up in process context so that we don't have to disable
 530  * interrupts all over the place
 531  */
 532 static void key_cleanup(void *data)
 533 {
 534         struct rb_node *_n;
 535         struct key *key;
 536
 537  go_again:
 538         /* look for a dead key in the tree */
 539         spin_lock(&key_serial_lock);
 540
 541         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 542                 key = rb_entry(_n, struct key, serial_node);
 543
 544                 if (atomic_read(&key->usage) == 0)
 545                         goto found_dead_key;
 546         }
 547
 548         spin_unlock(&key_serial_lock);
 549         return;
 550
 551  found_dead_key:
 552         /* we found a dead key - once we've removed it from the tree, we can
 553          * drop the lock */
 554         rb_erase(&key->serial_node, &key_serial_tree);
 555         spin_unlock(&key_serial_lock);
 556
 557         key_check(key);
 558
 559         /* deal with the user's key tracking and quota */
 560         if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
 561                 spin_lock(&key->user->lock);
 562                 key->user->qnkeys--;
 563                 key->user->qnbytes -= key->quotalen;
 564                 spin_unlock(&key->user->lock);
 565         }
 566
 567         atomic_dec(&key->user->nkeys);
 568         if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
 569                 atomic_dec(&key->user->nikeys);
 570
 571         key_user_put(key->user);
 572
 573         /* now throw away the key memory */
 574         if (key->type->destroy)
 575                 key->type->destroy(key);
 576
 577         kfree(key->description);
 578
 579 #ifdef KEY_DEBUGGING
 580         key->magic = KEY_DEBUG_MAGIC_X;
 581 #endif
 582         kmem_cache_free(key_jar, key);
 583
 584         /* there may, of course, be more than one key to destroy */
 585         goto go_again;
 586
 587 } /* end key_cleanup() */
 588
 589 /*****************************************************************************/
 590 /*
 591  * dispose of a reference to a key
 592  * - when all the references are gone, we schedule the cleanup task to come and
 593  *   pull it out of the tree in definite process context
 594  */
 595 void key_put(struct key *key)
 596 {
 597         if (key) {
 598                 key_check(key);
 599
 600                 if (atomic_dec_and_test(&key->usage))
 601                         schedule_work(&key_cleanup_task);
 602         }
 603
 604 } /* end key_put() */
 605
 606 EXPORT_SYMBOL(key_put);
 607
 608 /*****************************************************************************/
 609 /*
 610  * find a key by its serial number
 611  */
 612 struct key *key_lookup(key_serial_t id)
 613 {
 614         struct rb_node *n;
 615         struct key *key;
 616
 617         spin_lock(&key_serial_lock);
 618
 619         /* search the tree for the specified key */
 620         n = key_serial_tree.rb_node;
 621         while (n) {
 622                 key = rb_entry(n, struct key, serial_node);
 623
 624                 if (id < key->serial)
 625                         n = n->rb_left;
 626                 else if (id > key->serial)
 627                         n = n->rb_right;
 628                 else
 629                         goto found;
 630         }
 631
 632  not_found:
 633         key = ERR_PTR(-ENOKEY);
 634         goto error;
 635
 636  found:
 637         /* pretend it doesn't exist if it's dead */
 638         if (atomic_read(&key->usage) == 0 ||
 639             test_bit(KEY_FLAG_DEAD, &key->flags) ||
 640             key->type == &key_type_dead)
 641                 goto not_found;
 642
 643         /* this races with key_put(), but that doesn't matter since key_put()
 644          * doesn't actually change the key
 645          */
 646         atomic_inc(&key->usage);
 647
 648  error:
 649         spin_unlock(&key_serial_lock);
 650         return key;
 651
 652 } /* end key_lookup() */
 653
 654 /*****************************************************************************/
 655 /*
 656  * find and lock the specified key type against removal
 657  * - we return with the sem readlocked
 658  */
 659 struct key_type *key_type_lookup(const char *type)
 660 {
 661         struct key_type *ktype;
 662
 663         down_read(&key_types_sem);
 664
 665         /* look up the key type to see if it's one of the registered kernel
 666          * types */
 667         list_for_each_entry(ktype, &key_types_list, link) {
 668                 if (strcmp(ktype->name, type) == 0)
 669                         goto found_kernel_type;
 670         }
 671
 672         up_read(&key_types_sem);
 673         ktype = ERR_PTR(-ENOKEY);
 674
 675  found_kernel_type:
 676         return ktype;
 677
 678 } /* end key_type_lookup() */
 679
 680 /*****************************************************************************/
 681 /*
 682  * unlock a key type
 683  */
 684 void key_type_put(struct key_type *ktype)
 685 {
 686         up_read(&key_types_sem);
 687
 688 } /* end key_type_put() */
 689
 690 /*****************************************************************************/
 691 /*
 692  * attempt to update an existing key
 693  * - the key has an incremented refcount
 694  * - we need to put the key if we get an error
 695  */
 696 static inline key_ref_t __key_update(key_ref_t key_ref,
 697                                      const void *payload, size_t plen)
 698 {
 699         struct key *key = key_ref_to_ptr(key_ref);
 700         int ret;
 701
 702         /* need write permission on the key to update it */
 703         ret = -EACCES;
 704         if (!key_permission(key_ref, KEY_WRITE))
 705                 goto error;
 706
 707         ret = -EEXIST;
 708         if (!key->type->update)
 709                 goto error;
 710
 711         down_write(&key->sem);
 712
 713         ret = key->type->update(key, payload, plen);
 714
 715         if (ret == 0)
 716                 /* updating a negative key instantiates it */
 717                 clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
 718
 719         up_write(&key->sem);
 720
 721         if (ret < 0)
 722                 goto error;
 723 out:
 724         return key_ref;
 725
 726 error:
 727         key_put(key);
 728         key_ref = ERR_PTR(ret);
 729         goto out;
 730
 731 } /* end __key_update() */
 732
 733 /*****************************************************************************/
 734 /*
 735  * search the specified keyring for a key of the same description; if one is
 736  * found, update it, otherwise add a new one
 737  */
 738 key_ref_t key_create_or_update(key_ref_t keyring_ref,
 739                                const char *type,
 740                                const char *description,
 741                                const void *payload,
 742                                size_t plen,
 743                                int not_in_quota)
 744 {
 745         struct key_type *ktype;
 746         struct key *keyring, *key = NULL;
 747         key_perm_t perm;
 748         key_ref_t key_ref;
 749         int ret;
 750
 751         /* look up the key type to see if it's one of the registered kernel
 752          * types */
 753         ktype = key_type_lookup(type);
 754         if (IS_ERR(ktype)) {
 755                 key_ref = ERR_PTR(-ENODEV);
 756                 goto error;
 757         }
 758
 759         key_ref = ERR_PTR(-EINVAL);
 760         if (!ktype->match || !ktype->instantiate)
 761                 goto error_2;
 762
 763         keyring = key_ref_to_ptr(keyring_ref);
 764
 765         key_check(keyring);
 766
 767         down_write(&keyring->sem);
 768
 769         /* if we're going to allocate a new key, we're going to have
 770          * to modify the keyring */
 771         key_ref = ERR_PTR(-EACCES);
 772         if (!key_permission(keyring_ref, KEY_WRITE))
 773                 goto error_3;
 774
 775         /* search for an existing key of the same type and description in the
 776          * destination keyring
 777          */
 778         key_ref = __keyring_search_one(keyring_ref, ktype, description, 0);
 779         if (!IS_ERR(key_ref))
 780                 goto found_matching_key;
 781
 782         /* decide on the permissions we want */
 783         perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK;
 784         perm |= KEY_USR_VIEW | KEY_USR_SEARCH | KEY_USR_LINK;
 785
 786         if (ktype->read)
 787                 perm |= KEY_POS_READ | KEY_USR_READ;
 788
 789         if (ktype == &key_type_keyring || ktype->update)
 790                 perm |= KEY_USR_WRITE;
 791
 792         /* allocate a new key */
 793         key = key_alloc(ktype, description, current->fsuid, current->fsgid,
 794                         perm, not_in_quota);
 795         if (IS_ERR(key)) {
 796                 key_ref = ERR_PTR(PTR_ERR(key));
 797                 goto error_3;
 798         }
 799
 800         /* instantiate it and link it into the target keyring */
 801         ret = __key_instantiate_and_link(key, payload, plen, keyring, NULL);
 802         if (ret < 0) {
 803                 key_put(key);
 804                 key_ref = ERR_PTR(ret);
 805                 goto error_3;
 806         }
 807
 808         key_ref = make_key_ref(key, is_key_possessed(keyring_ref));
 809
 810  error_3:
 811         up_write(&keyring->sem);
 812  error_2:
 813         key_type_put(ktype);
 814  error:
 815         return key_ref;
 816
 817  found_matching_key:
 818         /* we found a matching key, so we're going to try to update it
 819          * - we can drop the locks first as we have the key pinned
 820          */
 821         up_write(&keyring->sem);
 822         key_type_put(ktype);
 823
 824         key_ref = __key_update(key_ref, payload, plen);
 825         goto error;
 826
 827 } /* end key_create_or_update() */
 828
 829 EXPORT_SYMBOL(key_create_or_update);
 830
 831 /*****************************************************************************/
 832 /*
 833  * update a key
 834  */
 835 int key_update(key_ref_t key_ref, const void *payload, size_t plen)
 836 {
 837         struct key *key = key_ref_to_ptr(key_ref);
 838         int ret;
 839
 840         key_check(key);
 841
 842         /* the key must be writable */
 843         ret = -EACCES;
 844         if (!key_permission(key_ref, KEY_WRITE))
 845                 goto error;
 846
 847         /* attempt to update it if supported */
 848         ret = -EOPNOTSUPP;
 849         if (key->type->update) {
 850                 down_write(&key->sem);
 851                 ret = key->type->update(key, payload, plen);
 852
 853                 if (ret == 0)
 854                         /* updating a negative key instantiates it */
 855                         clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
 856
 857                 up_write(&key->sem);
 858         }
 859
 860  error:
 861         return ret;
 862
 863 } /* end key_update() */
 864
 865 EXPORT_SYMBOL(key_update);
 866
 867 /*****************************************************************************/
 868 /*
 869  * duplicate a key, potentially with a revised description
 870  * - must be supported by the keytype (keyrings for instance can be duplicated)
 871  */
 872 struct key *key_duplicate(struct key *source, const char *desc)
 873 {
 874         struct key *key;
 875         int ret;
 876
 877         key_check(source);
 878
 879         if (!desc)
 880                 desc = source->description;
 881
 882         down_read(&key_types_sem);
 883
 884         ret = -EINVAL;
 885         if (!source->type->duplicate)
 886                 goto error;
 887
 888         /* allocate and instantiate a key */
 889         key = key_alloc(source->type, desc, current->fsuid, current->fsgid,
 890                         source->perm, 0);
 891         if (IS_ERR(key))
 892                 goto error_k;
 893
 894         down_read(&source->sem);
 895         ret = key->type->duplicate(key, source);
 896         up_read(&source->sem);
 897         if (ret < 0)
 898                 goto error2;
 899
 900         atomic_inc(&key->user->nikeys);
 901         set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
 902
 903  error_k:
 904         up_read(&key_types_sem);
 905  out:
 906         return key;
 907
 908  error2:
 909         key_put(key);
 910  error:
 911         up_read(&key_types_sem);
 912         key = ERR_PTR(ret);
 913         goto out;
 914
 915 } /* end key_duplicate() */
 916
 917 /*****************************************************************************/
 918 /*
 919  * revoke a key
 920  */
 921 void key_revoke(struct key *key)
 922 {
 923         key_check(key);
 924
 925         /* make sure no one's trying to change or use the key when we mark
 926          * it */
 927         down_write(&key->sem);
 928         set_bit(KEY_FLAG_REVOKED, &key->flags);
 929         up_write(&key->sem);
 930
 931 } /* end key_revoke() */
 932
 933 EXPORT_SYMBOL(key_revoke);
 934
 935 /*****************************************************************************/
 936 /*
 937  * register a type of key
 938  */
 939 int register_key_type(struct key_type *ktype)
 940 {
 941         struct key_type *p;
 942         int ret;
 943
 944         ret = -EEXIST;
 945         down_write(&key_types_sem);
 946
 947         /* disallow key types with the same name */
 948         list_for_each_entry(p, &key_types_list, link) {
 949                 if (strcmp(p->name, ktype->name) == 0)
 950                         goto out;
 951         }
 952
 953         /* store the type */
 954         list_add(&ktype->link, &key_types_list);
 955         ret = 0;
 956
 957  out:
 958         up_write(&key_types_sem);
 959         return ret;
 960
 961 } /* end register_key_type() */
 962
 963 EXPORT_SYMBOL(register_key_type);
 964
 965 /*****************************************************************************/
 966 /*
 967  * unregister a type of key
 968  */
 969 void unregister_key_type(struct key_type *ktype)
 970 {
 971         struct rb_node *_n;
 972         struct key *key;
 973
 974         down_write(&key_types_sem);
 975
 976         /* withdraw the key type */
 977         list_del_init(&ktype->link);
 978
 979         /* mark all the keys of this type dead */
 980         spin_lock(&key_serial_lock);
 981
 982         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 983                 key = rb_entry(_n, struct key, serial_node);
 984
 985                 if (key->type == ktype)
 986                         key->type = &key_type_dead;
 987         }
 988
 989         spin_unlock(&key_serial_lock);
 990
 991         /* make sure everyone revalidates their keys */
 992         synchronize_rcu();
 993
 994         /* we should now be able to destroy the payloads of all the keys of
 995          * this type with impunity */
 996         spin_lock(&key_serial_lock);
 997
 998         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 999                 key = rb_entry(_n, struct key, serial_node);
1000
1001                 if (key->type == ktype) {
1002                         if (ktype->destroy)
1003                                 ktype->destroy(key);
1004                         memset(&key->payload, 0xbd, sizeof(key->payload));
1005                 }
1006         }
1007
1008         spin_unlock(&key_serial_lock);
1009         up_write(&key_types_sem);
1010
1011 } /* end unregister_key_type() */
1012
1013 EXPORT_SYMBOL(unregister_key_type);
1014
1015 /*****************************************************************************/
1016 /*
1017  * initialise the key management stuff
1018  */
1019 void __init key_init(void)
1020 {
1021         /* allocate a slab in which we can store keys */
1022         key_jar = kmem_cache_create("key_jar", sizeof(struct key),
1023                         0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1024
1025         /* add the special key types */
1026         list_add_tail(&key_type_keyring.link, &key_types_list);
1027         list_add_tail(&key_type_dead.link, &key_types_list);
1028         list_add_tail(&key_type_user.link, &key_types_list);
1029
1030         /* record the root user tracking */
1031         rb_link_node(&root_key_user.node,
1032                      NULL,
1033                      &key_user_tree.rb_node);
1034
1035         rb_insert_color(&root_key_user.node,
1036                         &key_user_tree);
1037
1038         /* record root's user standard keyrings */
1039         key_check(&root_user_keyring);
1040         key_check(&root_session_keyring);
1041
1042         __key_insert_serial(&root_user_keyring);
1043         __key_insert_serial(&root_session_keyring);
1044
1045         keyring_publish_name(&root_user_keyring);
1046         keyring_publish_name(&root_session_keyring);
1047
1048         /* link the two root keyrings together */
1049         key_link(&root_session_keyring, &root_user_keyring);
1050
1051 } /* end key_init() */