security/keys/key.c

   1 /* Basic authentication token and access key management
   2  *
   3  * Copyright (C) 2004-2008 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/poison.h>
  15 #include <linux/sched.h>
  16 #include <linux/slab.h>
  17 #include <linux/security.h>
  18 #include <linux/workqueue.h>
  19 #include <linux/random.h>
  20 #include <linux/err.h>
  21 #include "internal.h"
  22
  23 static struct kmem_cache        *key_jar;
  24 struct rb_root          key_serial_tree; /* tree of keys indexed by serial */
  25 DEFINE_SPINLOCK(key_serial_lock);
  26
  27 struct rb_root  key_user_tree; /* tree of quota records indexed by UID */
  28 DEFINE_SPINLOCK(key_user_lock);
  29
  30 unsigned int key_quota_root_maxkeys = 200;      /* root's key count quota */
  31 unsigned int key_quota_root_maxbytes = 20000;   /* root's key space quota */
  32 unsigned int key_quota_maxkeys = 200;           /* general key count quota */
  33 unsigned int key_quota_maxbytes = 20000;        /* general key space quota */
  34
  35 static LIST_HEAD(key_types_list);
  36 static DECLARE_RWSEM(key_types_sem);
  37
  38 static void key_cleanup(struct work_struct *work);
  39 static DECLARE_WORK(key_cleanup_task, key_cleanup);
  40
  41 /* we serialise key instantiation and link */
  42 DEFINE_MUTEX(key_construction_mutex);
  43
  44 /* any key who's type gets unegistered will be re-typed to this */
  45 static struct key_type key_type_dead = {
  46         .name           = "dead",
  47 };
  48
  49 #ifdef KEY_DEBUGGING
  50 void __key_check(const struct key *key)
  51 {
  52         printk("__key_check: key %p {%08x} should be {%08x}\n",
  53                key, key->magic, KEY_DEBUG_MAGIC);
  54         BUG();
  55 }
  56 #endif
  57
  58 /*****************************************************************************/
  59 /*
  60  * get the key quota record for a user, allocating a new record if one doesn't
  61  * already exist
  62  */
  63 struct key_user *key_user_lookup(uid_t uid)
  64 {
  65         struct key_user *candidate = NULL, *user;
  66         struct rb_node *parent = NULL;
  67         struct rb_node **p;
  68
  69  try_again:
  70         p = &key_user_tree.rb_node;
  71         spin_lock(&key_user_lock);
  72
  73         /* search the tree for a user record with a matching UID */
  74         while (*p) {
  75                 parent = *p;
  76                 user = rb_entry(parent, struct key_user, node);
  77
  78                 if (uid < user->uid)
  79                         p = &(*p)->rb_left;
  80                 else if (uid > user->uid)
  81                         p = &(*p)->rb_right;
  82                 else
  83                         goto found;
  84         }
  85
  86         /* if we get here, we failed to find a match in the tree */
  87         if (!candidate) {
  88                 /* allocate a candidate user record if we don't already have
  89                  * one */
  90                 spin_unlock(&key_user_lock);
  91
  92                 user = NULL;
  93                 candidate = kmalloc(sizeof(struct key_user), GFP_KERNEL);
  94                 if (unlikely(!candidate))
  95                         goto out;
  96
  97                 /* the allocation may have scheduled, so we need to repeat the
  98                  * search lest someone else added the record whilst we were
  99                  * asleep */
 100                 goto try_again;
 101         }
 102
 103         /* if we get here, then the user record still hadn't appeared on the
 104          * second pass - so we use the candidate record */
 105         atomic_set(&candidate->usage, 1);
 106         atomic_set(&candidate->nkeys, 0);
 107         atomic_set(&candidate->nikeys, 0);
 108         candidate->uid = uid;
 109         candidate->qnkeys = 0;
 110         candidate->qnbytes = 0;
 111         spin_lock_init(&candidate->lock);
 112         mutex_init(&candidate->cons_lock);
 113
 114         rb_link_node(&candidate->node, parent, p);
 115         rb_insert_color(&candidate->node, &key_user_tree);
 116         spin_unlock(&key_user_lock);
 117         user = candidate;
 118         goto out;
 119
 120         /* okay - we found a user record for this UID */
 121  found:
 122         atomic_inc(&user->usage);
 123         spin_unlock(&key_user_lock);
 124         kfree(candidate);
 125  out:
 126         return user;
 127
 128 } /* end key_user_lookup() */
 129
 130 /*****************************************************************************/
 131 /*
 132  * dispose of a user structure
 133  */
 134 void key_user_put(struct key_user *user)
 135 {
 136         if (atomic_dec_and_lock(&user->usage, &key_user_lock)) {
 137                 rb_erase(&user->node, &key_user_tree);
 138                 spin_unlock(&key_user_lock);
 139
 140                 kfree(user);
 141         }
 142
 143 } /* end key_user_put() */
 144
 145 /*****************************************************************************/
 146 /*
 147  * assign a key the next unique serial number
 148  * - these are assigned randomly to avoid security issues through covert
 149  *   channel problems
 150  */
 151 static inline void key_alloc_serial(struct key *key)
 152 {
 153         struct rb_node *parent, **p;
 154         struct key *xkey;
 155
 156         /* propose a random serial number and look for a hole for it in the
 157          * serial number tree */
 158         do {
 159                 get_random_bytes(&key->serial, sizeof(key->serial));
 160
 161                 key->serial >>= 1; /* negative numbers are not permitted */
 162         } while (key->serial < 3);
 163
 164         spin_lock(&key_serial_lock);
 165
 166 attempt_insertion:
 167         parent = NULL;
 168         p = &key_serial_tree.rb_node;
 169
 170         while (*p) {
 171                 parent = *p;
 172                 xkey = rb_entry(parent, struct key, serial_node);
 173
 174                 if (key->serial < xkey->serial)
 175                         p = &(*p)->rb_left;
 176                 else if (key->serial > xkey->serial)
 177                         p = &(*p)->rb_right;
 178                 else
 179                         goto serial_exists;
 180         }
 181
 182         /* we've found a suitable hole - arrange for this key to occupy it */
 183         rb_link_node(&key->serial_node, parent, p);
 184         rb_insert_color(&key->serial_node, &key_serial_tree);
 185
 186         spin_unlock(&key_serial_lock);
 187         return;
 188
 189         /* we found a key with the proposed serial number - walk the tree from
 190          * that point looking for the next unused serial number */
 191 serial_exists:
 192         for (;;) {
 193                 key->serial++;
 194                 if (key->serial < 3) {
 195                         key->serial = 3;
 196                         goto attempt_insertion;
 197                 }
 198
 199                 parent = rb_next(parent);
 200                 if (!parent)
 201                         goto attempt_insertion;
 202
 203                 xkey = rb_entry(parent, struct key, serial_node);
 204                 if (key->serial < xkey->serial)
 205                         goto attempt_insertion;
 206         }
 207
 208 } /* end key_alloc_serial() */
 209
 210 /*****************************************************************************/
 211 /*
 212  * allocate a key of the specified type
 213  * - update the user's quota to reflect the existence of the key
 214  * - called from a key-type operation with key_types_sem read-locked by
 215  *   key_create_or_update()
 216  *   - this prevents unregistration of the key type
 217  * - upon return the key is as yet uninstantiated; the caller needs to either
 218  *   instantiate the key or discard it before returning
 219  */
 220 struct key *key_alloc(struct key_type *type, const char *desc,
 221                       uid_t uid, gid_t gid, struct task_struct *ctx,
 222                       key_perm_t perm, unsigned long flags)
 223 {
 224         struct key_user *user = NULL;
 225         struct key *key;
 226         size_t desclen, quotalen;
 227         int ret;
 228
 229         key = ERR_PTR(-EINVAL);
 230         if (!desc || !*desc)
 231                 goto error;
 232
 233         desclen = strlen(desc) + 1;
 234         quotalen = desclen + type->def_datalen;
 235
 236         /* get hold of the key tracking for this user */
 237         user = key_user_lookup(uid);
 238         if (!user)
 239                 goto no_memory_1;
 240
 241         /* check that the user's quota permits allocation of another key and
 242          * its description */
 243         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
 244                 unsigned maxkeys = (uid == 0) ?
 245                         key_quota_root_maxkeys : key_quota_maxkeys;
 246                 unsigned maxbytes = (uid == 0) ?
 247                         key_quota_root_maxbytes : key_quota_maxbytes;
 248
 249                 spin_lock(&user->lock);
 250                 if (!(flags & KEY_ALLOC_QUOTA_OVERRUN)) {
 251                         if (user->qnkeys + 1 >= maxkeys ||
 252                             user->qnbytes + quotalen >= maxbytes ||
 253                             user->qnbytes + quotalen < user->qnbytes)
 254                                 goto no_quota;
 255                 }
 256
 257                 user->qnkeys++;
 258                 user->qnbytes += quotalen;
 259                 spin_unlock(&user->lock);
 260         }
 261
 262         /* allocate and initialise the key and its description */
 263         key = kmem_cache_alloc(key_jar, GFP_KERNEL);
 264         if (!key)
 265                 goto no_memory_2;
 266
 267         if (desc) {
 268                 key->description = kmemdup(desc, desclen, GFP_KERNEL);
 269                 if (!key->description)
 270                         goto no_memory_3;
 271         }
 272
 273         atomic_set(&key->usage, 1);
 274         init_rwsem(&key->sem);
 275         key->type = type;
 276         key->user = user;
 277         key->quotalen = quotalen;
 278         key->datalen = type->def_datalen;
 279         key->uid = uid;
 280         key->gid = gid;
 281         key->perm = perm;
 282         key->flags = 0;
 283         key->expiry = 0;
 284         key->payload.data = NULL;
 285         key->security = NULL;
 286
 287         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA))
 288                 key->flags |= 1 << KEY_FLAG_IN_QUOTA;
 289
 290         memset(&key->type_data, 0, sizeof(key->type_data));
 291
 292 #ifdef KEY_DEBUGGING
 293         key->magic = KEY_DEBUG_MAGIC;
 294 #endif
 295
 296         /* let the security module know about the key */
 297         ret = security_key_alloc(key, ctx, flags);
 298         if (ret < 0)
 299                 goto security_error;
 300
 301         /* publish the key by giving it a serial number */
 302         atomic_inc(&user->nkeys);
 303         key_alloc_serial(key);
 304
 305 error:
 306         return key;
 307
 308 security_error:
 309         kfree(key->description);
 310         kmem_cache_free(key_jar, key);
 311         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
 312                 spin_lock(&user->lock);
 313                 user->qnkeys--;
 314                 user->qnbytes -= quotalen;
 315                 spin_unlock(&user->lock);
 316         }
 317         key_user_put(user);
 318         key = ERR_PTR(ret);
 319         goto error;
 320
 321 no_memory_3:
 322         kmem_cache_free(key_jar, key);
 323 no_memory_2:
 324         if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
 325                 spin_lock(&user->lock);
 326                 user->qnkeys--;
 327                 user->qnbytes -= quotalen;
 328                 spin_unlock(&user->lock);
 329         }
 330         key_user_put(user);
 331 no_memory_1:
 332         key = ERR_PTR(-ENOMEM);
 333         goto error;
 334
 335 no_quota:
 336         spin_unlock(&user->lock);
 337         key_user_put(user);
 338         key = ERR_PTR(-EDQUOT);
 339         goto error;
 340
 341 } /* end key_alloc() */
 342
 343 EXPORT_SYMBOL(key_alloc);
 344
 345 /*****************************************************************************/
 346 /*
 347  * reserve an amount of quota for the key's payload
 348  */
 349 int key_payload_reserve(struct key *key, size_t datalen)
 350 {
 351         int delta = (int) datalen - key->datalen;
 352         int ret = 0;
 353
 354         key_check(key);
 355
 356         /* contemplate the quota adjustment */
 357         if (delta != 0 && test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
 358                 unsigned maxbytes = (key->user->uid == 0) ?
 359                         key_quota_root_maxbytes : key_quota_maxbytes;
 360
 361                 spin_lock(&key->user->lock);
 362
 363                 if (delta > 0 &&
 364                     (key->user->qnbytes + delta >= maxbytes ||
 365                      key->user->qnbytes + delta < key->user->qnbytes)) {
 366                         ret = -EDQUOT;
 367                 }
 368                 else {
 369                         key->user->qnbytes += delta;
 370                         key->quotalen += delta;
 371                 }
 372                 spin_unlock(&key->user->lock);
 373         }
 374
 375         /* change the recorded data length if that didn't generate an error */
 376         if (ret == 0)
 377                 key->datalen = datalen;
 378
 379         return ret;
 380
 381 } /* end key_payload_reserve() */
 382
 383 EXPORT_SYMBOL(key_payload_reserve);
 384
 385 /*****************************************************************************/
 386 /*
 387  * instantiate a key and link it into the target keyring atomically
 388  * - called with the target keyring's semaphore writelocked
 389  */
 390 static int __key_instantiate_and_link(struct key *key,
 391                                       const void *data,
 392                                       size_t datalen,
 393                                       struct key *keyring,
 394                                       struct key *instkey)
 395 {
 396         int ret, awaken;
 397
 398         key_check(key);
 399         key_check(keyring);
 400
 401         awaken = 0;
 402         ret = -EBUSY;
 403
 404         mutex_lock(&key_construction_mutex);
 405
 406         /* can't instantiate twice */
 407         if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
 408                 /* instantiate the key */
 409                 ret = key->type->instantiate(key, data, datalen);
 410
 411                 if (ret == 0) {
 412                         /* mark the key as being instantiated */
 413                         atomic_inc(&key->user->nikeys);
 414                         set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
 415
 416                         if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
 417                                 awaken = 1;
 418
 419                         /* and link it into the destination keyring */
 420                         if (keyring)
 421                                 ret = __key_link(keyring, key);
 422
 423                         /* disable the authorisation key */
 424                         if (instkey)
 425                                 key_revoke(instkey);
 426                 }
 427         }
 428
 429         mutex_unlock(&key_construction_mutex);
 430
 431         /* wake up anyone waiting for a key to be constructed */
 432         if (awaken)
 433                 wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
 434
 435         return ret;
 436
 437 } /* end __key_instantiate_and_link() */
 438
 439 /*****************************************************************************/
 440 /*
 441  * instantiate a key and link it into the target keyring atomically
 442  */
 443 int key_instantiate_and_link(struct key *key,
 444                              const void *data,
 445                              size_t datalen,
 446                              struct key *keyring,
 447                              struct key *instkey)
 448 {
 449         int ret;
 450
 451         if (keyring)
 452                 down_write(&keyring->sem);
 453
 454         ret = __key_instantiate_and_link(key, data, datalen, keyring, instkey);
 455
 456         if (keyring)
 457                 up_write(&keyring->sem);
 458
 459         return ret;
 460
 461 } /* end key_instantiate_and_link() */
 462
 463 EXPORT_SYMBOL(key_instantiate_and_link);
 464
 465 /*****************************************************************************/
 466 /*
 467  * negatively instantiate a key and link it into the target keyring atomically
 468  */
 469 int key_negate_and_link(struct key *key,
 470                         unsigned timeout,
 471                         struct key *keyring,
 472                         struct key *instkey)
 473 {
 474         struct timespec now;
 475         int ret, awaken;
 476
 477         key_check(key);
 478         key_check(keyring);
 479
 480         awaken = 0;
 481         ret = -EBUSY;
 482
 483         if (keyring)
 484                 down_write(&keyring->sem);
 485
 486         mutex_lock(&key_construction_mutex);
 487
 488         /* can't instantiate twice */
 489         if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
 490                 /* mark the key as being negatively instantiated */
 491                 atomic_inc(&key->user->nikeys);
 492                 set_bit(KEY_FLAG_NEGATIVE, &key->flags);
 493                 set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
 494                 now = current_kernel_time();
 495                 key->expiry = now.tv_sec + timeout;
 496
 497                 if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
 498                         awaken = 1;
 499
 500                 ret = 0;
 501
 502                 /* and link it into the destination keyring */
 503                 if (keyring)
 504                         ret = __key_link(keyring, key);
 505
 506                 /* disable the authorisation key */
 507                 if (instkey)
 508                         key_revoke(instkey);
 509         }
 510
 511         mutex_unlock(&key_construction_mutex);
 512
 513         if (keyring)
 514                 up_write(&keyring->sem);
 515
 516         /* wake up anyone waiting for a key to be constructed */
 517         if (awaken)
 518                 wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
 519
 520         return ret;
 521
 522 } /* end key_negate_and_link() */
 523
 524 EXPORT_SYMBOL(key_negate_and_link);
 525
 526 /*****************************************************************************/
 527 /*
 528  * do cleaning up in process context so that we don't have to disable
 529  * interrupts all over the place
 530  */
 531 static void key_cleanup(struct work_struct *work)
 532 {
 533         struct rb_node *_n;
 534         struct key *key;
 535
 536  go_again:
 537         /* look for a dead key in the tree */
 538         spin_lock(&key_serial_lock);
 539
 540         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 541                 key = rb_entry(_n, struct key, serial_node);
 542
 543                 if (atomic_read(&key->usage) == 0)
 544                         goto found_dead_key;
 545         }
 546
 547         spin_unlock(&key_serial_lock);
 548         return;
 549
 550  found_dead_key:
 551         /* we found a dead key - once we've removed it from the tree, we can
 552          * drop the lock */
 553         rb_erase(&key->serial_node, &key_serial_tree);
 554         spin_unlock(&key_serial_lock);
 555
 556         key_check(key);
 557
 558         security_key_free(key);
 559
 560         /* deal with the user's key tracking and quota */
 561         if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
 562                 spin_lock(&key->user->lock);
 563                 key->user->qnkeys--;
 564                 key->user->qnbytes -= key->quotalen;
 565                 spin_unlock(&key->user->lock);
 566         }
 567
 568         atomic_dec(&key->user->nkeys);
 569         if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
 570                 atomic_dec(&key->user->nikeys);
 571
 572         key_user_put(key->user);
 573
 574         /* now throw away the key memory */
 575         if (key->type->destroy)
 576                 key->type->destroy(key);
 577
 578         kfree(key->description);
 579
 580 #ifdef KEY_DEBUGGING
 581         key->magic = KEY_DEBUG_MAGIC_X;
 582 #endif
 583         kmem_cache_free(key_jar, key);
 584
 585         /* there may, of course, be more than one key to destroy */
 586         goto go_again;
 587
 588 } /* end key_cleanup() */
 589
 590 /*****************************************************************************/
 591 /*
 592  * dispose of a reference to a key
 593  * - when all the references are gone, we schedule the cleanup task to come and
 594  *   pull it out of the tree in definite process context
 595  */
 596 void key_put(struct key *key)
 597 {
 598         if (key) {
 599                 key_check(key);
 600
 601                 if (atomic_dec_and_test(&key->usage))
 602                         schedule_work(&key_cleanup_task);
 603         }
 604
 605 } /* end key_put() */
 606
 607 EXPORT_SYMBOL(key_put);
 608
 609 /*****************************************************************************/
 610 /*
 611  * find a key by its serial number
 612  */
 613 struct key *key_lookup(key_serial_t id)
 614 {
 615         struct rb_node *n;
 616         struct key *key;
 617
 618         spin_lock(&key_serial_lock);
 619
 620         /* search the tree for the specified key */
 621         n = key_serial_tree.rb_node;
 622         while (n) {
 623                 key = rb_entry(n, struct key, serial_node);
 624
 625                 if (id < key->serial)
 626                         n = n->rb_left;
 627                 else if (id > key->serial)
 628                         n = n->rb_right;
 629                 else
 630                         goto found;
 631         }
 632
 633  not_found:
 634         key = ERR_PTR(-ENOKEY);
 635         goto error;
 636
 637  found:
 638         /* pretend it doesn't exist if it's dead */
 639         if (atomic_read(&key->usage) == 0 ||
 640             test_bit(KEY_FLAG_DEAD, &key->flags) ||
 641             key->type == &key_type_dead)
 642                 goto not_found;
 643
 644         /* this races with key_put(), but that doesn't matter since key_put()
 645          * doesn't actually change the key
 646          */
 647         atomic_inc(&key->usage);
 648
 649  error:
 650         spin_unlock(&key_serial_lock);
 651         return key;
 652
 653 } /* end key_lookup() */
 654
 655 /*****************************************************************************/
 656 /*
 657  * find and lock the specified key type against removal
 658  * - we return with the sem readlocked
 659  */
 660 struct key_type *key_type_lookup(const char *type)
 661 {
 662         struct key_type *ktype;
 663
 664         down_read(&key_types_sem);
 665
 666         /* look up the key type to see if it's one of the registered kernel
 667          * types */
 668         list_for_each_entry(ktype, &key_types_list, link) {
 669                 if (strcmp(ktype->name, type) == 0)
 670                         goto found_kernel_type;
 671         }
 672
 673         up_read(&key_types_sem);
 674         ktype = ERR_PTR(-ENOKEY);
 675
 676  found_kernel_type:
 677         return ktype;
 678
 679 } /* end key_type_lookup() */
 680
 681 /*****************************************************************************/
 682 /*
 683  * unlock a key type
 684  */
 685 void key_type_put(struct key_type *ktype)
 686 {
 687         up_read(&key_types_sem);
 688
 689 } /* end key_type_put() */
 690
 691 /*****************************************************************************/
 692 /*
 693  * attempt to update an existing key
 694  * - the key has an incremented refcount
 695  * - we need to put the key if we get an error
 696  */
 697 static inline key_ref_t __key_update(key_ref_t key_ref,
 698                                      const void *payload, size_t plen)
 699 {
 700         struct key *key = key_ref_to_ptr(key_ref);
 701         int ret;
 702
 703         /* need write permission on the key to update it */
 704         ret = key_permission(key_ref, KEY_WRITE);
 705         if (ret < 0)
 706                 goto error;
 707
 708         ret = -EEXIST;
 709         if (!key->type->update)
 710                 goto error;
 711
 712         down_write(&key->sem);
 713
 714         ret = key->type->update(key, payload, plen);
 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                                key_perm_t perm,
 744                                unsigned long flags)
 745 {
 746         struct key_type *ktype;
 747         struct key *keyring, *key = NULL;
 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         key_ref = ERR_PTR(-ENOTDIR);
 768         if (keyring->type != &key_type_keyring)
 769                 goto error_2;
 770
 771         down_write(&keyring->sem);
 772
 773         /* if we're going to allocate a new key, we're going to have
 774          * to modify the keyring */
 775         ret = key_permission(keyring_ref, KEY_WRITE);
 776         if (ret < 0) {
 777                 key_ref = ERR_PTR(ret);
 778                 goto error_3;
 779         }
 780
 781         /* if it's possible to update this type of key, search for an existing
 782          * key of the same type and description in the destination keyring and
 783          * update that instead if possible
 784          */
 785         if (ktype->update) {
 786                 key_ref = __keyring_search_one(keyring_ref, ktype, description,
 787                                                0);
 788                 if (!IS_ERR(key_ref))
 789                         goto found_matching_key;
 790         }
 791
 792         /* if the client doesn't provide, decide on the permissions we want */
 793         if (perm == KEY_PERM_UNDEF) {
 794                 perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
 795                 perm |= KEY_USR_VIEW | KEY_USR_SEARCH | KEY_USR_LINK | KEY_USR_SETATTR;
 796
 797                 if (ktype->read)
 798                         perm |= KEY_POS_READ | KEY_USR_READ;
 799
 800                 if (ktype == &key_type_keyring || ktype->update)
 801                         perm |= KEY_USR_WRITE;
 802         }
 803
 804         /* allocate a new key */
 805         key = key_alloc(ktype, description, current->fsuid, current->fsgid,
 806                         current, perm, flags);
 807         if (IS_ERR(key)) {
 808                 key_ref = ERR_CAST(key);
 809                 goto error_3;
 810         }
 811
 812         /* instantiate it and link it into the target keyring */
 813         ret = __key_instantiate_and_link(key, payload, plen, keyring, NULL);
 814         if (ret < 0) {
 815                 key_put(key);
 816                 key_ref = ERR_PTR(ret);
 817                 goto error_3;
 818         }
 819
 820         key_ref = make_key_ref(key, is_key_possessed(keyring_ref));
 821
 822  error_3:
 823         up_write(&keyring->sem);
 824  error_2:
 825         key_type_put(ktype);
 826  error:
 827         return key_ref;
 828
 829  found_matching_key:
 830         /* we found a matching key, so we're going to try to update it
 831          * - we can drop the locks first as we have the key pinned
 832          */
 833         up_write(&keyring->sem);
 834         key_type_put(ktype);
 835
 836         key_ref = __key_update(key_ref, payload, plen);
 837         goto error;
 838
 839 } /* end key_create_or_update() */
 840
 841 EXPORT_SYMBOL(key_create_or_update);
 842
 843 /*****************************************************************************/
 844 /*
 845  * update a key
 846  */
 847 int key_update(key_ref_t key_ref, const void *payload, size_t plen)
 848 {
 849         struct key *key = key_ref_to_ptr(key_ref);
 850         int ret;
 851
 852         key_check(key);
 853
 854         /* the key must be writable */
 855         ret = key_permission(key_ref, KEY_WRITE);
 856         if (ret < 0)
 857                 goto error;
 858
 859         /* attempt to update it if supported */
 860         ret = -EOPNOTSUPP;
 861         if (key->type->update) {
 862                 down_write(&key->sem);
 863
 864                 ret = key->type->update(key, payload, plen);
 865                 if (ret == 0)
 866                         /* updating a negative key instantiates it */
 867                         clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
 868
 869                 up_write(&key->sem);
 870         }
 871
 872  error:
 873         return ret;
 874
 875 } /* end key_update() */
 876
 877 EXPORT_SYMBOL(key_update);
 878
 879 /*****************************************************************************/
 880 /*
 881  * revoke a key
 882  */
 883 void key_revoke(struct key *key)
 884 {
 885         key_check(key);
 886
 887         /* make sure no one's trying to change or use the key when we mark it
 888          * - we tell lockdep that we might nest because we might be revoking an
 889          *   authorisation key whilst holding the sem on a key we've just
 890          *   instantiated
 891          */
 892         down_write_nested(&key->sem, 1);
 893         if (!test_and_set_bit(KEY_FLAG_REVOKED, &key->flags) &&
 894             key->type->revoke)
 895                 key->type->revoke(key);
 896
 897         up_write(&key->sem);
 898
 899 } /* end key_revoke() */
 900
 901 EXPORT_SYMBOL(key_revoke);
 902
 903 /*****************************************************************************/
 904 /*
 905  * register a type of key
 906  */
 907 int register_key_type(struct key_type *ktype)
 908 {
 909         struct key_type *p;
 910         int ret;
 911
 912         ret = -EEXIST;
 913         down_write(&key_types_sem);
 914
 915         /* disallow key types with the same name */
 916         list_for_each_entry(p, &key_types_list, link) {
 917                 if (strcmp(p->name, ktype->name) == 0)
 918                         goto out;
 919         }
 920
 921         /* store the type */
 922         list_add(&ktype->link, &key_types_list);
 923         ret = 0;
 924
 925  out:
 926         up_write(&key_types_sem);
 927         return ret;
 928
 929 } /* end register_key_type() */
 930
 931 EXPORT_SYMBOL(register_key_type);
 932
 933 /*****************************************************************************/
 934 /*
 935  * unregister a type of key
 936  */
 937 void unregister_key_type(struct key_type *ktype)
 938 {
 939         struct rb_node *_n;
 940         struct key *key;
 941
 942         down_write(&key_types_sem);
 943
 944         /* withdraw the key type */
 945         list_del_init(&ktype->link);
 946
 947         /* mark all the keys of this type dead */
 948         spin_lock(&key_serial_lock);
 949
 950         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 951                 key = rb_entry(_n, struct key, serial_node);
 952
 953                 if (key->type == ktype)
 954                         key->type = &key_type_dead;
 955         }
 956
 957         spin_unlock(&key_serial_lock);
 958
 959         /* make sure everyone revalidates their keys */
 960         synchronize_rcu();
 961
 962         /* we should now be able to destroy the payloads of all the keys of
 963          * this type with impunity */
 964         spin_lock(&key_serial_lock);
 965
 966         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 967                 key = rb_entry(_n, struct key, serial_node);
 968
 969                 if (key->type == ktype) {
 970                         if (ktype->destroy)
 971                                 ktype->destroy(key);
 972                         memset(&key->payload, KEY_DESTROY, sizeof(key->payload));
 973                 }
 974         }
 975
 976         spin_unlock(&key_serial_lock);
 977         up_write(&key_types_sem);
 978
 979 } /* end unregister_key_type() */
 980
 981 EXPORT_SYMBOL(unregister_key_type);
 982
 983 /*****************************************************************************/
 984 /*
 985  * initialise the key management stuff
 986  */
 987 void __init key_init(void)
 988 {
 989         /* allocate a slab in which we can store keys */
 990         key_jar = kmem_cache_create("key_jar", sizeof(struct key),
 991                         0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
 992
 993         /* add the special key types */
 994         list_add_tail(&key_type_keyring.link, &key_types_list);
 995         list_add_tail(&key_type_dead.link, &key_types_list);
 996         list_add_tail(&key_type_user.link, &key_types_list);
 997
 998         /* record the root user tracking */
 999         rb_link_node(&root_key_user.node,
1000                      NULL,
1001                      &key_user_tree.rb_node);
1002
1003         rb_insert_color(&root_key_user.node,
1004                         &key_user_tree);
1005
1006 } /* end key_init() */