security/keys/key.c

   1 /* key.c: basic authentication token and access key management
   2  *
   3  * Copyright (C) 2004 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/workqueue.h>
  18 #include <linux/err.h>
  19 #include "internal.h"
  20
  21 static kmem_cache_t     *key_jar;
  22 static key_serial_t     key_serial_next = 3;
  23 struct rb_root          key_serial_tree; /* tree of keys indexed by serial */
  24 DEFINE_SPINLOCK(key_serial_lock);
  25
  26 struct rb_root  key_user_tree; /* tree of quota records indexed by UID */
  27 DEFINE_SPINLOCK(key_user_lock);
  28
  29 static LIST_HEAD(key_types_list);
  30 static DECLARE_RWSEM(key_types_sem);
  31
  32 static void key_cleanup(void *data);
  33 static DECLARE_WORK(key_cleanup_task, key_cleanup, NULL);
  34
  35 /* we serialise key instantiation and link */
  36 DECLARE_RWSEM(key_construction_sem);
  37
  38 /* any key who's type gets unegistered will be re-typed to this */
  39 static struct key_type key_type_dead = {
  40         .name           = "dead",
  41 };
  42
  43 #ifdef KEY_DEBUGGING
  44 void __key_check(const struct key *key)
  45 {
  46         printk("__key_check: key %p {%08x} should be {%08x}\n",
  47                key, key->magic, KEY_DEBUG_MAGIC);
  48         BUG();
  49 }
  50 #endif
  51
  52 /*****************************************************************************/
  53 /*
  54  * get the key quota record for a user, allocating a new record if one doesn't
  55  * already exist
  56  */
  57 struct key_user *key_user_lookup(uid_t uid)
  58 {
  59         struct key_user *candidate = NULL, *user;
  60         struct rb_node *parent = NULL;
  61         struct rb_node **p;
  62
  63  try_again:
  64         p = &key_user_tree.rb_node;
  65         spin_lock(&key_user_lock);
  66
  67         /* search the tree for a user record with a matching UID */
  68         while (*p) {
  69                 parent = *p;
  70                 user = rb_entry(parent, struct key_user, node);
  71
  72                 if (uid < user->uid)
  73                         p = &(*p)->rb_left;
  74                 else if (uid > user->uid)
  75                         p = &(*p)->rb_right;
  76                 else
  77                         goto found;
  78         }
  79
  80         /* if we get here, we failed to find a match in the tree */
  81         if (!candidate) {
  82                 /* allocate a candidate user record if we don't already have
  83                  * one */
  84                 spin_unlock(&key_user_lock);
  85
  86                 user = NULL;
  87                 candidate = kmalloc(sizeof(struct key_user), GFP_KERNEL);
  88                 if (unlikely(!candidate))
  89                         goto out;
  90
  91                 /* the allocation may have scheduled, so we need to repeat the
  92                  * search lest someone else added the record whilst we were
  93                  * asleep */
  94                 goto try_again;
  95         }
  96
  97         /* if we get here, then the user record still hadn't appeared on the
  98          * second pass - so we use the candidate record */
  99         atomic_set(&candidate->usage, 1);
 100         atomic_set(&candidate->nkeys, 0);
 101         atomic_set(&candidate->nikeys, 0);
 102         candidate->uid = uid;
 103         candidate->qnkeys = 0;
 104         candidate->qnbytes = 0;
 105         spin_lock_init(&candidate->lock);
 106         INIT_LIST_HEAD(&candidate->consq);
 107
 108         rb_link_node(&candidate->node, parent, p);
 109         rb_insert_color(&candidate->node, &key_user_tree);
 110         spin_unlock(&key_user_lock);
 111         user = candidate;
 112         goto out;
 113
 114         /* okay - we found a user record for this UID */
 115  found:
 116         atomic_inc(&user->usage);
 117         spin_unlock(&key_user_lock);
 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
 244  *   key_create_or_update()
 245  *   - this prevents unregistration 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         int ret;
 257
 258         key = ERR_PTR(-EINVAL);
 259         if (!desc || !*desc)
 260                 goto error;
 261
 262         desclen = strlen(desc) + 1;
 263         quotalen = desclen + type->def_datalen;
 264
 265         /* get hold of the key tracking for this user */
 266         user = key_user_lookup(uid);
 267         if (!user)
 268                 goto no_memory_1;
 269
 270         /* check that the user's quota permits allocation of another key and
 271          * its description */
 272         if (!not_in_quota) {
 273                 spin_lock(&user->lock);
 274                 if (user->qnkeys + 1 >= KEYQUOTA_MAX_KEYS &&
 275                     user->qnbytes + quotalen >= KEYQUOTA_MAX_BYTES
 276                     )
 277                         goto no_quota;
 278
 279                 user->qnkeys++;
 280                 user->qnbytes += quotalen;
 281                 spin_unlock(&user->lock);
 282         }
 283
 284         /* allocate and initialise the key and its description */
 285         key = kmem_cache_alloc(key_jar, SLAB_KERNEL);
 286         if (!key)
 287                 goto no_memory_2;
 288
 289         if (desc) {
 290                 key->description = kmalloc(desclen, GFP_KERNEL);
 291                 if (!key->description)
 292                         goto no_memory_3;
 293
 294                 memcpy(key->description, desc, desclen);
 295         }
 296
 297         atomic_set(&key->usage, 1);
 298         init_rwsem(&key->sem);
 299         key->type = type;
 300         key->user = user;
 301         key->quotalen = quotalen;
 302         key->datalen = type->def_datalen;
 303         key->uid = uid;
 304         key->gid = gid;
 305         key->perm = perm;
 306         key->flags = 0;
 307         key->expiry = 0;
 308         key->payload.data = NULL;
 309         key->security = NULL;
 310
 311         if (!not_in_quota)
 312                 key->flags |= 1 << KEY_FLAG_IN_QUOTA;
 313
 314         memset(&key->type_data, 0, sizeof(key->type_data));
 315
 316 #ifdef KEY_DEBUGGING
 317         key->magic = KEY_DEBUG_MAGIC;
 318 #endif
 319
 320         /* let the security module know about the key */
 321         ret = security_key_alloc(key);
 322         if (ret < 0)
 323                 goto security_error;
 324
 325         /* publish the key by giving it a serial number */
 326         atomic_inc(&user->nkeys);
 327         key_alloc_serial(key);
 328
 329 error:
 330         return key;
 331
 332 security_error:
 333         kfree(key->description);
 334         kmem_cache_free(key_jar, key);
 335         if (!not_in_quota) {
 336                 spin_lock(&user->lock);
 337                 user->qnkeys--;
 338                 user->qnbytes -= quotalen;
 339                 spin_unlock(&user->lock);
 340         }
 341         key_user_put(user);
 342         key = ERR_PTR(ret);
 343         goto error;
 344
 345 no_memory_3:
 346         kmem_cache_free(key_jar, key);
 347 no_memory_2:
 348         if (!not_in_quota) {
 349                 spin_lock(&user->lock);
 350                 user->qnkeys--;
 351                 user->qnbytes -= quotalen;
 352                 spin_unlock(&user->lock);
 353         }
 354         key_user_put(user);
 355 no_memory_1:
 356         key = ERR_PTR(-ENOMEM);
 357         goto error;
 358
 359 no_quota:
 360         spin_unlock(&user->lock);
 361         key_user_put(user);
 362         key = ERR_PTR(-EDQUOT);
 363         goto error;
 364
 365 } /* end key_alloc() */
 366
 367 EXPORT_SYMBOL(key_alloc);
 368
 369 /*****************************************************************************/
 370 /*
 371  * reserve an amount of quota for the key's payload
 372  */
 373 int key_payload_reserve(struct key *key, size_t datalen)
 374 {
 375         int delta = (int) datalen - key->datalen;
 376         int ret = 0;
 377
 378         key_check(key);
 379
 380         /* contemplate the quota adjustment */
 381         if (delta != 0 && test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
 382                 spin_lock(&key->user->lock);
 383
 384                 if (delta > 0 &&
 385                     key->user->qnbytes + delta > KEYQUOTA_MAX_BYTES
 386                     ) {
 387                         ret = -EDQUOT;
 388                 }
 389                 else {
 390                         key->user->qnbytes += delta;
 391                         key->quotalen += delta;
 392                 }
 393                 spin_unlock(&key->user->lock);
 394         }
 395
 396         /* change the recorded data length if that didn't generate an error */
 397         if (ret == 0)
 398                 key->datalen = datalen;
 399
 400         return ret;
 401
 402 } /* end key_payload_reserve() */
 403
 404 EXPORT_SYMBOL(key_payload_reserve);
 405
 406 /*****************************************************************************/
 407 /*
 408  * instantiate a key and link it into the target keyring atomically
 409  * - called with the target keyring's semaphore writelocked
 410  */
 411 static int __key_instantiate_and_link(struct key *key,
 412                                       const void *data,
 413                                       size_t datalen,
 414                                       struct key *keyring,
 415                                       struct key *instkey)
 416 {
 417         int ret, awaken;
 418
 419         key_check(key);
 420         key_check(keyring);
 421
 422         awaken = 0;
 423         ret = -EBUSY;
 424
 425         down_write(&key_construction_sem);
 426
 427         /* can't instantiate twice */
 428         if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
 429                 /* instantiate the key */
 430                 ret = key->type->instantiate(key, data, datalen);
 431
 432                 if (ret == 0) {
 433                         /* mark the key as being instantiated */
 434                         atomic_inc(&key->user->nikeys);
 435                         set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
 436
 437                         if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
 438                                 awaken = 1;
 439
 440                         /* and link it into the destination keyring */
 441                         if (keyring)
 442                                 ret = __key_link(keyring, key);
 443
 444                         /* disable the authorisation key */
 445                         if (instkey)
 446                                 key_revoke(instkey);
 447                 }
 448         }
 449
 450         up_write(&key_construction_sem);
 451
 452         /* wake up anyone waiting for a key to be constructed */
 453         if (awaken)
 454                 wake_up_all(&request_key_conswq);
 455
 456         return ret;
 457
 458 } /* end __key_instantiate_and_link() */
 459
 460 /*****************************************************************************/
 461 /*
 462  * instantiate a key and link it into the target keyring atomically
 463  */
 464 int key_instantiate_and_link(struct key *key,
 465                              const void *data,
 466                              size_t datalen,
 467                              struct key *keyring,
 468                              struct key *instkey)
 469 {
 470         int ret;
 471
 472         if (keyring)
 473                 down_write(&keyring->sem);
 474
 475         ret = __key_instantiate_and_link(key, data, datalen, keyring, instkey);
 476
 477         if (keyring)
 478                 up_write(&keyring->sem);
 479
 480         return ret;
 481
 482 } /* end key_instantiate_and_link() */
 483
 484 EXPORT_SYMBOL(key_instantiate_and_link);
 485
 486 /*****************************************************************************/
 487 /*
 488  * negatively instantiate a key and link it into the target keyring atomically
 489  */
 490 int key_negate_and_link(struct key *key,
 491                         unsigned timeout,
 492                         struct key *keyring,
 493                         struct key *instkey)
 494 {
 495         struct timespec now;
 496         int ret, awaken;
 497
 498         key_check(key);
 499         key_check(keyring);
 500
 501         awaken = 0;
 502         ret = -EBUSY;
 503
 504         if (keyring)
 505                 down_write(&keyring->sem);
 506
 507         down_write(&key_construction_sem);
 508
 509         /* can't instantiate twice */
 510         if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
 511                 /* mark the key as being negatively instantiated */
 512                 atomic_inc(&key->user->nikeys);
 513                 set_bit(KEY_FLAG_NEGATIVE, &key->flags);
 514                 set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
 515                 now = current_kernel_time();
 516                 key->expiry = now.tv_sec + timeout;
 517
 518                 if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
 519                         awaken = 1;
 520
 521                 ret = 0;
 522
 523                 /* and link it into the destination keyring */
 524                 if (keyring)
 525                         ret = __key_link(keyring, key);
 526
 527                 /* disable the authorisation key */
 528                 if (instkey)
 529                         key_revoke(instkey);
 530         }
 531
 532         up_write(&key_construction_sem);
 533
 534         if (keyring)
 535                 up_write(&keyring->sem);
 536
 537         /* wake up anyone waiting for a key to be constructed */
 538         if (awaken)
 539                 wake_up_all(&request_key_conswq);
 540
 541         return ret;
 542
 543 } /* end key_negate_and_link() */
 544
 545 EXPORT_SYMBOL(key_negate_and_link);
 546
 547 /*****************************************************************************/
 548 /*
 549  * do cleaning up in process context so that we don't have to disable
 550  * interrupts all over the place
 551  */
 552 static void key_cleanup(void *data)
 553 {
 554         struct rb_node *_n;
 555         struct key *key;
 556
 557  go_again:
 558         /* look for a dead key in the tree */
 559         spin_lock(&key_serial_lock);
 560
 561         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 562                 key = rb_entry(_n, struct key, serial_node);
 563
 564                 if (atomic_read(&key->usage) == 0)
 565                         goto found_dead_key;
 566         }
 567
 568         spin_unlock(&key_serial_lock);
 569         return;
 570
 571  found_dead_key:
 572         /* we found a dead key - once we've removed it from the tree, we can
 573          * drop the lock */
 574         rb_erase(&key->serial_node, &key_serial_tree);
 575         spin_unlock(&key_serial_lock);
 576
 577         key_check(key);
 578
 579         security_key_free(key);
 580
 581         /* deal with the user's key tracking and quota */
 582         if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
 583                 spin_lock(&key->user->lock);
 584                 key->user->qnkeys--;
 585                 key->user->qnbytes -= key->quotalen;
 586                 spin_unlock(&key->user->lock);
 587         }
 588
 589         atomic_dec(&key->user->nkeys);
 590         if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
 591                 atomic_dec(&key->user->nikeys);
 592
 593         key_user_put(key->user);
 594
 595         /* now throw away the key memory */
 596         if (key->type->destroy)
 597                 key->type->destroy(key);
 598
 599         kfree(key->description);
 600
 601 #ifdef KEY_DEBUGGING
 602         key->magic = KEY_DEBUG_MAGIC_X;
 603 #endif
 604         kmem_cache_free(key_jar, key);
 605
 606         /* there may, of course, be more than one key to destroy */
 607         goto go_again;
 608
 609 } /* end key_cleanup() */
 610
 611 /*****************************************************************************/
 612 /*
 613  * dispose of a reference to a key
 614  * - when all the references are gone, we schedule the cleanup task to come and
 615  *   pull it out of the tree in definite process context
 616  */
 617 void key_put(struct key *key)
 618 {
 619         if (key) {
 620                 key_check(key);
 621
 622                 if (atomic_dec_and_test(&key->usage))
 623                         schedule_work(&key_cleanup_task);
 624         }
 625
 626 } /* end key_put() */
 627
 628 EXPORT_SYMBOL(key_put);
 629
 630 /*****************************************************************************/
 631 /*
 632  * find a key by its serial number
 633  */
 634 struct key *key_lookup(key_serial_t id)
 635 {
 636         struct rb_node *n;
 637         struct key *key;
 638
 639         spin_lock(&key_serial_lock);
 640
 641         /* search the tree for the specified key */
 642         n = key_serial_tree.rb_node;
 643         while (n) {
 644                 key = rb_entry(n, struct key, serial_node);
 645
 646                 if (id < key->serial)
 647                         n = n->rb_left;
 648                 else if (id > key->serial)
 649                         n = n->rb_right;
 650                 else
 651                         goto found;
 652         }
 653
 654  not_found:
 655         key = ERR_PTR(-ENOKEY);
 656         goto error;
 657
 658  found:
 659         /* pretend it doesn't exist if it's dead */
 660         if (atomic_read(&key->usage) == 0 ||
 661             test_bit(KEY_FLAG_DEAD, &key->flags) ||
 662             key->type == &key_type_dead)
 663                 goto not_found;
 664
 665         /* this races with key_put(), but that doesn't matter since key_put()
 666          * doesn't actually change the key
 667          */
 668         atomic_inc(&key->usage);
 669
 670  error:
 671         spin_unlock(&key_serial_lock);
 672         return key;
 673
 674 } /* end key_lookup() */
 675
 676 /*****************************************************************************/
 677 /*
 678  * find and lock the specified key type against removal
 679  * - we return with the sem readlocked
 680  */
 681 struct key_type *key_type_lookup(const char *type)
 682 {
 683         struct key_type *ktype;
 684
 685         down_read(&key_types_sem);
 686
 687         /* look up the key type to see if it's one of the registered kernel
 688          * types */
 689         list_for_each_entry(ktype, &key_types_list, link) {
 690                 if (strcmp(ktype->name, type) == 0)
 691                         goto found_kernel_type;
 692         }
 693
 694         up_read(&key_types_sem);
 695         ktype = ERR_PTR(-ENOKEY);
 696
 697  found_kernel_type:
 698         return ktype;
 699
 700 } /* end key_type_lookup() */
 701
 702 /*****************************************************************************/
 703 /*
 704  * unlock a key type
 705  */
 706 void key_type_put(struct key_type *ktype)
 707 {
 708         up_read(&key_types_sem);
 709
 710 } /* end key_type_put() */
 711
 712 /*****************************************************************************/
 713 /*
 714  * attempt to update an existing key
 715  * - the key has an incremented refcount
 716  * - we need to put the key if we get an error
 717  */
 718 static inline key_ref_t __key_update(key_ref_t key_ref,
 719                                      const void *payload, size_t plen)
 720 {
 721         struct key *key = key_ref_to_ptr(key_ref);
 722         int ret;
 723
 724         /* need write permission on the key to update it */
 725         ret = key_permission(key_ref, KEY_WRITE);
 726         if (ret < 0)
 727                 goto error;
 728
 729         ret = -EEXIST;
 730         if (!key->type->update)
 731                 goto error;
 732
 733         down_write(&key->sem);
 734
 735         ret = key->type->update(key, payload, plen);
 736         if (ret == 0)
 737                 /* updating a negative key instantiates it */
 738                 clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
 739
 740         up_write(&key->sem);
 741
 742         if (ret < 0)
 743                 goto error;
 744 out:
 745         return key_ref;
 746
 747 error:
 748         key_put(key);
 749         key_ref = ERR_PTR(ret);
 750         goto out;
 751
 752 } /* end __key_update() */
 753
 754 /*****************************************************************************/
 755 /*
 756  * search the specified keyring for a key of the same description; if one is
 757  * found, update it, otherwise add a new one
 758  */
 759 key_ref_t key_create_or_update(key_ref_t keyring_ref,
 760                                const char *type,
 761                                const char *description,
 762                                const void *payload,
 763                                size_t plen,
 764                                int not_in_quota)
 765 {
 766         struct key_type *ktype;
 767         struct key *keyring, *key = NULL;
 768         key_perm_t perm;
 769         key_ref_t key_ref;
 770         int ret;
 771
 772         /* look up the key type to see if it's one of the registered kernel
 773          * types */
 774         ktype = key_type_lookup(type);
 775         if (IS_ERR(ktype)) {
 776                 key_ref = ERR_PTR(-ENODEV);
 777                 goto error;
 778         }
 779
 780         key_ref = ERR_PTR(-EINVAL);
 781         if (!ktype->match || !ktype->instantiate)
 782                 goto error_2;
 783
 784         keyring = key_ref_to_ptr(keyring_ref);
 785
 786         key_check(keyring);
 787
 788         down_write(&keyring->sem);
 789
 790         /* if we're going to allocate a new key, we're going to have
 791          * to modify the keyring */
 792         ret = key_permission(keyring_ref, KEY_WRITE);
 793         if (ret < 0) {
 794                 key_ref = ERR_PTR(ret);
 795                 goto error_3;
 796         }
 797
 798         /* search for an existing key of the same type and description in the
 799          * destination keyring
 800          */
 801         key_ref = __keyring_search_one(keyring_ref, ktype, description, 0);
 802         if (!IS_ERR(key_ref))
 803                 goto found_matching_key;
 804
 805         /* decide on the permissions we want */
 806         perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
 807         perm |= KEY_USR_VIEW | KEY_USR_SEARCH | KEY_USR_LINK | KEY_USR_SETATTR;
 808
 809         if (ktype->read)
 810                 perm |= KEY_POS_READ | KEY_USR_READ;
 811
 812         if (ktype == &key_type_keyring || ktype->update)
 813                 perm |= KEY_USR_WRITE;
 814
 815         /* allocate a new key */
 816         key = key_alloc(ktype, description, current->fsuid, current->fsgid,
 817                         perm, not_in_quota);
 818         if (IS_ERR(key)) {
 819                 key_ref = ERR_PTR(PTR_ERR(key));
 820                 goto error_3;
 821         }
 822
 823         /* instantiate it and link it into the target keyring */
 824         ret = __key_instantiate_and_link(key, payload, plen, keyring, NULL);
 825         if (ret < 0) {
 826                 key_put(key);
 827                 key_ref = ERR_PTR(ret);
 828                 goto error_3;
 829         }
 830
 831         key_ref = make_key_ref(key, is_key_possessed(keyring_ref));
 832
 833  error_3:
 834         up_write(&keyring->sem);
 835  error_2:
 836         key_type_put(ktype);
 837  error:
 838         return key_ref;
 839
 840  found_matching_key:
 841         /* we found a matching key, so we're going to try to update it
 842          * - we can drop the locks first as we have the key pinned
 843          */
 844         up_write(&keyring->sem);
 845         key_type_put(ktype);
 846
 847         key_ref = __key_update(key_ref, payload, plen);
 848         goto error;
 849
 850 } /* end key_create_or_update() */
 851
 852 EXPORT_SYMBOL(key_create_or_update);
 853
 854 /*****************************************************************************/
 855 /*
 856  * update a key
 857  */
 858 int key_update(key_ref_t key_ref, const void *payload, size_t plen)
 859 {
 860         struct key *key = key_ref_to_ptr(key_ref);
 861         int ret;
 862
 863         key_check(key);
 864
 865         /* the key must be writable */
 866         ret = key_permission(key_ref, KEY_WRITE);
 867         if (ret < 0)
 868                 goto error;
 869
 870         /* attempt to update it if supported */
 871         ret = -EOPNOTSUPP;
 872         if (key->type->update) {
 873                 down_write(&key->sem);
 874
 875                 ret = key->type->update(key, payload, plen);
 876                 if (ret == 0)
 877                         /* updating a negative key instantiates it */
 878                         clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
 879
 880                 up_write(&key->sem);
 881         }
 882
 883  error:
 884         return ret;
 885
 886 } /* end key_update() */
 887
 888 EXPORT_SYMBOL(key_update);
 889
 890 /*****************************************************************************/
 891 /*
 892  * revoke a key
 893  */
 894 void key_revoke(struct key *key)
 895 {
 896         key_check(key);
 897
 898         /* make sure no one's trying to change or use the key when we mark
 899          * it */
 900         down_write(&key->sem);
 901         set_bit(KEY_FLAG_REVOKED, &key->flags);
 902         up_write(&key->sem);
 903
 904 } /* end key_revoke() */
 905
 906 EXPORT_SYMBOL(key_revoke);
 907
 908 /*****************************************************************************/
 909 /*
 910  * register a type of key
 911  */
 912 int register_key_type(struct key_type *ktype)
 913 {
 914         struct key_type *p;
 915         int ret;
 916
 917         ret = -EEXIST;
 918         down_write(&key_types_sem);
 919
 920         /* disallow key types with the same name */
 921         list_for_each_entry(p, &key_types_list, link) {
 922                 if (strcmp(p->name, ktype->name) == 0)
 923                         goto out;
 924         }
 925
 926         /* store the type */
 927         list_add(&ktype->link, &key_types_list);
 928         ret = 0;
 929
 930  out:
 931         up_write(&key_types_sem);
 932         return ret;
 933
 934 } /* end register_key_type() */
 935
 936 EXPORT_SYMBOL(register_key_type);
 937
 938 /*****************************************************************************/
 939 /*
 940  * unregister a type of key
 941  */
 942 void unregister_key_type(struct key_type *ktype)
 943 {
 944         struct rb_node *_n;
 945         struct key *key;
 946
 947         down_write(&key_types_sem);
 948
 949         /* withdraw the key type */
 950         list_del_init(&ktype->link);
 951
 952         /* mark all the keys of this type dead */
 953         spin_lock(&key_serial_lock);
 954
 955         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 956                 key = rb_entry(_n, struct key, serial_node);
 957
 958                 if (key->type == ktype)
 959                         key->type = &key_type_dead;
 960         }
 961
 962         spin_unlock(&key_serial_lock);
 963
 964         /* make sure everyone revalidates their keys */
 965         synchronize_rcu();
 966
 967         /* we should now be able to destroy the payloads of all the keys of
 968          * this type with impunity */
 969         spin_lock(&key_serial_lock);
 970
 971         for (_n = rb_first(&key_serial_tree); _n; _n = rb_next(_n)) {
 972                 key = rb_entry(_n, struct key, serial_node);
 973
 974                 if (key->type == ktype) {
 975                         if (ktype->destroy)
 976                                 ktype->destroy(key);
 977                         memset(&key->payload, 0xbd, sizeof(key->payload));
 978                 }
 979         }
 980
 981         spin_unlock(&key_serial_lock);
 982         up_write(&key_types_sem);
 983
 984 } /* end unregister_key_type() */
 985
 986 EXPORT_SYMBOL(unregister_key_type);
 987
 988 /*****************************************************************************/
 989 /*
 990  * initialise the key management stuff
 991  */
 992 void __init key_init(void)
 993 {
 994         /* allocate a slab in which we can store keys */
 995         key_jar = kmem_cache_create("key_jar", sizeof(struct key),
 996                         0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
 997
 998         /* add the special key types */
 999         list_add_tail(&key_type_keyring.link, &key_types_list);
1000         list_add_tail(&key_type_dead.link, &key_types_list);
1001         list_add_tail(&key_type_user.link, &key_types_list);
1002
1003         /* record the root user tracking */
1004         rb_link_node(&root_key_user.node,
1005                      NULL,
1006                      &key_user_tree.rb_node);
1007
1008         rb_insert_color(&root_key_user.node,
1009                         &key_user_tree);
1010
1011         /* record root's user standard keyrings */
1012         key_check(&root_user_keyring);
1013         key_check(&root_session_keyring);
1014
1015         __key_insert_serial(&root_user_keyring);
1016         __key_insert_serial(&root_session_keyring);
1017
1018         keyring_publish_name(&root_user_keyring);
1019         keyring_publish_name(&root_session_keyring);
1020
1021         /* link the two root keyrings together */
1022         key_link(&root_session_keyring, &root_user_keyring);
1023
1024 } /* end key_init() */