security/keys/process_keys.c

   1 /* Manage a process's keyrings
   2  *
   3  * Copyright (C) 2004-2005, 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/sched.h>
  15 #include <linux/keyctl.h>
  16 #include <linux/fs.h>
  17 #include <linux/err.h>
  18 #include <linux/mutex.h>
  19 #include <linux/security.h>
  20 #include <linux/user_namespace.h>
  21 #include <asm/uaccess.h>
  22 #include "internal.h"
  23
  24 /* Session keyring create vs join semaphore */
  25 static DEFINE_MUTEX(key_session_mutex);
  26
  27 /* User keyring creation semaphore */
  28 static DEFINE_MUTEX(key_user_keyring_mutex);
  29
  30 /* The root user's tracking struct */
  31 struct key_user root_key_user = {
  32         .usage          = ATOMIC_INIT(3),
  33         .cons_lock      = __MUTEX_INITIALIZER(root_key_user.cons_lock),
  34         .lock           = __SPIN_LOCK_UNLOCKED(root_key_user.lock),
  35         .nkeys          = ATOMIC_INIT(2),
  36         .nikeys         = ATOMIC_INIT(2),
  37         .uid            = GLOBAL_ROOT_UID,
  38 };
  39
  40 /*
  41  * Install the user and user session keyrings for the current process's UID.
  42  */
  43 int install_user_keyrings(void)
  44 {
  45         struct user_struct *user;
  46         const struct cred *cred;
  47         struct key *uid_keyring, *session_keyring;
  48         char buf[20];
  49         int ret;
  50         uid_t uid;
  51
  52         cred = current_cred();
  53         user = cred->user;
  54         uid = from_kuid(cred->user_ns, user->uid);
  55
  56         kenter("%p{%u}", user, uid);
  57
  58         if (user->uid_keyring) {
  59                 kleave(" = 0 [exist]");
  60                 return 0;
  61         }
  62
  63         mutex_lock(&key_user_keyring_mutex);
  64         ret = 0;
  65
  66         if (!user->uid_keyring) {
  67                 /* get the UID-specific keyring
  68                  * - there may be one in existence already as it may have been
  69                  *   pinned by a session, but the user_struct pointing to it
  70                  *   may have been destroyed by setuid */
  71                 sprintf(buf, "_uid.%u", uid);
  72
  73                 uid_keyring = find_keyring_by_name(buf, true);
  74                 if (IS_ERR(uid_keyring)) {
  75                         uid_keyring = keyring_alloc(buf, user->uid, INVALID_GID,
  76                                                     cred, KEY_ALLOC_IN_QUOTA,
  77                                                     NULL);
  78                         if (IS_ERR(uid_keyring)) {
  79                                 ret = PTR_ERR(uid_keyring);
  80                                 goto error;
  81                         }
  82                 }
  83
  84                 /* get a default session keyring (which might also exist
  85                  * already) */
  86                 sprintf(buf, "_uid_ses.%u", uid);
  87
  88                 session_keyring = find_keyring_by_name(buf, true);
  89                 if (IS_ERR(session_keyring)) {
  90                         session_keyring =
  91                                 keyring_alloc(buf, user->uid, INVALID_GID,
  92                                               cred, KEY_ALLOC_IN_QUOTA, NULL);
  93                         if (IS_ERR(session_keyring)) {
  94                                 ret = PTR_ERR(session_keyring);
  95                                 goto error_release;
  96                         }
  97
  98                         /* we install a link from the user session keyring to
  99                          * the user keyring */
 100                         ret = key_link(session_keyring, uid_keyring);
 101                         if (ret < 0)
 102                                 goto error_release_both;
 103                 }
 104
 105                 /* install the keyrings */
 106                 user->uid_keyring = uid_keyring;
 107                 user->session_keyring = session_keyring;
 108         }
 109
 110         mutex_unlock(&key_user_keyring_mutex);
 111         kleave(" = 0");
 112         return 0;
 113
 114 error_release_both:
 115         key_put(session_keyring);
 116 error_release:
 117         key_put(uid_keyring);
 118 error:
 119         mutex_unlock(&key_user_keyring_mutex);
 120         kleave(" = %d", ret);
 121         return ret;
 122 }
 123
 124 /*
 125  * Install a fresh thread keyring directly to new credentials.  This keyring is
 126  * allowed to overrun the quota.
 127  */
 128 int install_thread_keyring_to_cred(struct cred *new)
 129 {
 130         struct key *keyring;
 131
 132         keyring = keyring_alloc("_tid", new->uid, new->gid, new,
 133                                 KEY_ALLOC_QUOTA_OVERRUN, NULL);
 134         if (IS_ERR(keyring))
 135                 return PTR_ERR(keyring);
 136
 137         new->thread_keyring = keyring;
 138         return 0;
 139 }
 140
 141 /*
 142  * Install a fresh thread keyring, discarding the old one.
 143  */
 144 static int install_thread_keyring(void)
 145 {
 146         struct cred *new;
 147         int ret;
 148
 149         new = prepare_creds();
 150         if (!new)
 151                 return -ENOMEM;
 152
 153         BUG_ON(new->thread_keyring);
 154
 155         ret = install_thread_keyring_to_cred(new);
 156         if (ret < 0) {
 157                 abort_creds(new);
 158                 return ret;
 159         }
 160
 161         return commit_creds(new);
 162 }
 163
 164 /*
 165  * Install a process keyring directly to a credentials struct.
 166  *
 167  * Returns -EEXIST if there was already a process keyring, 0 if one installed,
 168  * and other value on any other error
 169  */
 170 int install_process_keyring_to_cred(struct cred *new)
 171 {
 172         struct key *keyring;
 173         int ret;
 174
 175         if (new->tgcred->process_keyring)
 176                 return -EEXIST;
 177
 178         keyring = keyring_alloc("_pid", new->uid, new->gid,
 179                                 new, KEY_ALLOC_QUOTA_OVERRUN, NULL);
 180         if (IS_ERR(keyring))
 181                 return PTR_ERR(keyring);
 182
 183         spin_lock_irq(&new->tgcred->lock);
 184         if (!new->tgcred->process_keyring) {
 185                 new->tgcred->process_keyring = keyring;
 186                 keyring = NULL;
 187                 ret = 0;
 188         } else {
 189                 ret = -EEXIST;
 190         }
 191         spin_unlock_irq(&new->tgcred->lock);
 192         key_put(keyring);
 193         return ret;
 194 }
 195
 196 /*
 197  * Make sure a process keyring is installed for the current process.  The
 198  * existing process keyring is not replaced.
 199  *
 200  * Returns 0 if there is a process keyring by the end of this function, some
 201  * error otherwise.
 202  */
 203 static int install_process_keyring(void)
 204 {
 205         struct cred *new;
 206         int ret;
 207
 208         new = prepare_creds();
 209         if (!new)
 210                 return -ENOMEM;
 211
 212         ret = install_process_keyring_to_cred(new);
 213         if (ret < 0) {
 214                 abort_creds(new);
 215                 return ret != -EEXIST ? ret : 0;
 216         }
 217
 218         return commit_creds(new);
 219 }
 220
 221 /*
 222  * Install a session keyring directly to a credentials struct.
 223  */
 224 int install_session_keyring_to_cred(struct cred *cred, struct key *keyring)
 225 {
 226         unsigned long flags;
 227         struct key *old;
 228
 229         might_sleep();
 230
 231         /* create an empty session keyring */
 232         if (!keyring) {
 233                 flags = KEY_ALLOC_QUOTA_OVERRUN;
 234                 if (cred->tgcred->session_keyring)
 235                         flags = KEY_ALLOC_IN_QUOTA;
 236
 237                 keyring = keyring_alloc("_ses", cred->uid, cred->gid,
 238                                         cred, flags, NULL);
 239                 if (IS_ERR(keyring))
 240                         return PTR_ERR(keyring);
 241         } else {
 242                 atomic_inc(&keyring->usage);
 243         }
 244
 245         /* install the keyring */
 246         spin_lock_irq(&cred->tgcred->lock);
 247         old = cred->tgcred->session_keyring;
 248         rcu_assign_pointer(cred->tgcred->session_keyring, keyring);
 249         spin_unlock_irq(&cred->tgcred->lock);
 250
 251         /* we're using RCU on the pointer, but there's no point synchronising
 252          * on it if it didn't previously point to anything */
 253         if (old) {
 254                 synchronize_rcu();
 255                 key_put(old);
 256         }
 257
 258         return 0;
 259 }
 260
 261 /*
 262  * Install a session keyring, discarding the old one.  If a keyring is not
 263  * supplied, an empty one is invented.
 264  */
 265 static int install_session_keyring(struct key *keyring)
 266 {
 267         struct cred *new;
 268         int ret;
 269
 270         new = prepare_creds();
 271         if (!new)
 272                 return -ENOMEM;
 273
 274         ret = install_session_keyring_to_cred(new, keyring);
 275         if (ret < 0) {
 276                 abort_creds(new);
 277                 return ret;
 278         }
 279
 280         return commit_creds(new);
 281 }
 282
 283 /*
 284  * Handle the fsuid changing.
 285  */
 286 void key_fsuid_changed(struct task_struct *tsk)
 287 {
 288         /* update the ownership of the thread keyring */
 289         BUG_ON(!tsk->cred);
 290         if (tsk->cred->thread_keyring) {
 291                 down_write(&tsk->cred->thread_keyring->sem);
 292                 tsk->cred->thread_keyring->uid = tsk->cred->fsuid;
 293                 up_write(&tsk->cred->thread_keyring->sem);
 294         }
 295 }
 296
 297 /*
 298  * Handle the fsgid changing.
 299  */
 300 void key_fsgid_changed(struct task_struct *tsk)
 301 {
 302         /* update the ownership of the thread keyring */
 303         BUG_ON(!tsk->cred);
 304         if (tsk->cred->thread_keyring) {
 305                 down_write(&tsk->cred->thread_keyring->sem);
 306                 tsk->cred->thread_keyring->gid = tsk->cred->fsgid;
 307                 up_write(&tsk->cred->thread_keyring->sem);
 308         }
 309 }
 310
 311 /*
 312  * Search the process keyrings attached to the supplied cred for the first
 313  * matching key.
 314  *
 315  * The search criteria are the type and the match function.  The description is
 316  * given to the match function as a parameter, but doesn't otherwise influence
 317  * the search.  Typically the match function will compare the description
 318  * parameter to the key's description.
 319  *
 320  * This can only search keyrings that grant Search permission to the supplied
 321  * credentials.  Keyrings linked to searched keyrings will also be searched if
 322  * they grant Search permission too.  Keys can only be found if they grant
 323  * Search permission to the credentials.
 324  *
 325  * Returns a pointer to the key with the key usage count incremented if
 326  * successful, -EAGAIN if we didn't find any matching key or -ENOKEY if we only
 327  * matched negative keys.
 328  *
 329  * In the case of a successful return, the possession attribute is set on the
 330  * returned key reference.
 331  */
 332 key_ref_t search_my_process_keyrings(struct key_type *type,
 333                                      const void *description,
 334                                      key_match_func_t match,
 335                                      bool no_state_check,
 336                                      const struct cred *cred)
 337 {
 338         key_ref_t key_ref, ret, err;
 339
 340         /* we want to return -EAGAIN or -ENOKEY if any of the keyrings were
 341          * searchable, but we failed to find a key or we found a negative key;
 342          * otherwise we want to return a sample error (probably -EACCES) if
 343          * none of the keyrings were searchable
 344          *
 345          * in terms of priority: success > -ENOKEY > -EAGAIN > other error
 346          */
 347         key_ref = NULL;
 348         ret = NULL;
 349         err = ERR_PTR(-EAGAIN);
 350
 351         /* search the thread keyring first */
 352         if (cred->thread_keyring) {
 353                 key_ref = keyring_search_aux(
 354                         make_key_ref(cred->thread_keyring, 1),
 355                         cred, type, description, match, no_state_check);
 356                 if (!IS_ERR(key_ref))
 357                         goto found;
 358
 359                 switch (PTR_ERR(key_ref)) {
 360                 case -EAGAIN: /* no key */
 361                 case -ENOKEY: /* negative key */
 362                         ret = key_ref;
 363                         break;
 364                 default:
 365                         err = key_ref;
 366                         break;
 367                 }
 368         }
 369
 370         /* search the process keyring second */
 371         if (cred->tgcred->process_keyring) {
 372                 key_ref = keyring_search_aux(
 373                         make_key_ref(cred->tgcred->process_keyring, 1),
 374                         cred, type, description, match, no_state_check);
 375                 if (!IS_ERR(key_ref))
 376                         goto found;
 377
 378                 switch (PTR_ERR(key_ref)) {
 379                 case -EAGAIN: /* no key */
 380                         if (ret)
 381                                 break;
 382                 case -ENOKEY: /* negative key */
 383                         ret = key_ref;
 384                         break;
 385                 default:
 386                         err = key_ref;
 387                         break;
 388                 }
 389         }
 390
 391         /* search the session keyring */
 392         if (cred->tgcred->session_keyring) {
 393                 rcu_read_lock();
 394                 key_ref = keyring_search_aux(
 395                         make_key_ref(rcu_dereference(
 396                                              cred->tgcred->session_keyring),
 397                                      1),
 398                         cred, type, description, match, no_state_check);
 399                 rcu_read_unlock();
 400
 401                 if (!IS_ERR(key_ref))
 402                         goto found;
 403
 404                 switch (PTR_ERR(key_ref)) {
 405                 case -EAGAIN: /* no key */
 406                         if (ret)
 407                                 break;
 408                 case -ENOKEY: /* negative key */
 409                         ret = key_ref;
 410                         break;
 411                 default:
 412                         err = key_ref;
 413                         break;
 414                 }
 415         }
 416         /* or search the user-session keyring */
 417         else if (cred->user->session_keyring) {
 418                 key_ref = keyring_search_aux(
 419                         make_key_ref(cred->user->session_keyring, 1),
 420                         cred, type, description, match, no_state_check);
 421                 if (!IS_ERR(key_ref))
 422                         goto found;
 423
 424                 switch (PTR_ERR(key_ref)) {
 425                 case -EAGAIN: /* no key */
 426                         if (ret)
 427                                 break;
 428                 case -ENOKEY: /* negative key */
 429                         ret = key_ref;
 430                         break;
 431                 default:
 432                         err = key_ref;
 433                         break;
 434                 }
 435         }
 436
 437         /* no key - decide on the error we're going to go for */
 438         key_ref = ret ? ret : err;
 439
 440 found:
 441         return key_ref;
 442 }
 443
 444 /*
 445  * Search the process keyrings attached to the supplied cred for the first
 446  * matching key in the manner of search_my_process_keyrings(), but also search
 447  * the keys attached to the assumed authorisation key using its credentials if
 448  * one is available.
 449  *
 450  * Return same as search_my_process_keyrings().
 451  */
 452 key_ref_t search_process_keyrings(struct key_type *type,
 453                                   const void *description,
 454                                   key_match_func_t match,
 455                                   const struct cred *cred)
 456 {
 457         struct request_key_auth *rka;
 458         key_ref_t key_ref, ret = ERR_PTR(-EACCES), err;
 459
 460         might_sleep();
 461
 462         key_ref = search_my_process_keyrings(type, description, match,
 463                                              false, cred);
 464         if (!IS_ERR(key_ref))
 465                 goto found;
 466         err = key_ref;
 467
 468         /* if this process has an instantiation authorisation key, then we also
 469          * search the keyrings of the process mentioned there
 470          * - we don't permit access to request_key auth keys via this method
 471          */
 472         if (cred->request_key_auth &&
 473             cred == current_cred() &&
 474             type != &key_type_request_key_auth
 475             ) {
 476                 /* defend against the auth key being revoked */
 477                 down_read(&cred->request_key_auth->sem);
 478
 479                 if (key_validate(cred->request_key_auth) == 0) {
 480                         rka = cred->request_key_auth->payload.data;
 481
 482                         key_ref = search_process_keyrings(type, description,
 483                                                           match, rka->cred);
 484
 485                         up_read(&cred->request_key_auth->sem);
 486
 487                         if (!IS_ERR(key_ref))
 488                                 goto found;
 489
 490                         ret = key_ref;
 491                 } else {
 492                         up_read(&cred->request_key_auth->sem);
 493                 }
 494         }
 495
 496         /* no key - decide on the error we're going to go for */
 497         if (err == ERR_PTR(-ENOKEY) || ret == ERR_PTR(-ENOKEY))
 498                 key_ref = ERR_PTR(-ENOKEY);
 499         else if (err == ERR_PTR(-EACCES))
 500                 key_ref = ret;
 501         else
 502                 key_ref = err;
 503
 504 found:
 505         return key_ref;
 506 }
 507
 508 /*
 509  * See if the key we're looking at is the target key.
 510  */
 511 int lookup_user_key_possessed(const struct key *key, const void *target)
 512 {
 513         return key == target;
 514 }
 515
 516 /*
 517  * Look up a key ID given us by userspace with a given permissions mask to get
 518  * the key it refers to.
 519  *
 520  * Flags can be passed to request that special keyrings be created if referred
 521  * to directly, to permit partially constructed keys to be found and to skip
 522  * validity and permission checks on the found key.
 523  *
 524  * Returns a pointer to the key with an incremented usage count if successful;
 525  * -EINVAL if the key ID is invalid; -ENOKEY if the key ID does not correspond
 526  * to a key or the best found key was a negative key; -EKEYREVOKED or
 527  * -EKEYEXPIRED if the best found key was revoked or expired; -EACCES if the
 528  * found key doesn't grant the requested permit or the LSM denied access to it;
 529  * or -ENOMEM if a special keyring couldn't be created.
 530  *
 531  * In the case of a successful return, the possession attribute is set on the
 532  * returned key reference.
 533  */
 534 key_ref_t lookup_user_key(key_serial_t id, unsigned long lflags,
 535                           key_perm_t perm)
 536 {
 537         struct request_key_auth *rka;
 538         const struct cred *cred;
 539         struct key *key;
 540         key_ref_t key_ref, skey_ref;
 541         int ret;
 542
 543 try_again:
 544         cred = get_current_cred();
 545         key_ref = ERR_PTR(-ENOKEY);
 546
 547         switch (id) {
 548         case KEY_SPEC_THREAD_KEYRING:
 549                 if (!cred->thread_keyring) {
 550                         if (!(lflags & KEY_LOOKUP_CREATE))
 551                                 goto error;
 552
 553                         ret = install_thread_keyring();
 554                         if (ret < 0) {
 555                                 key_ref = ERR_PTR(ret);
 556                                 goto error;
 557                         }
 558                         goto reget_creds;
 559                 }
 560
 561                 key = cred->thread_keyring;
 562                 atomic_inc(&key->usage);
 563                 key_ref = make_key_ref(key, 1);
 564                 break;
 565
 566         case KEY_SPEC_PROCESS_KEYRING:
 567                 if (!cred->tgcred->process_keyring) {
 568                         if (!(lflags & KEY_LOOKUP_CREATE))
 569                                 goto error;
 570
 571                         ret = install_process_keyring();
 572                         if (ret < 0) {
 573                                 key_ref = ERR_PTR(ret);
 574                                 goto error;
 575                         }
 576                         goto reget_creds;
 577                 }
 578
 579                 key = cred->tgcred->process_keyring;
 580                 atomic_inc(&key->usage);
 581                 key_ref = make_key_ref(key, 1);
 582                 break;
 583
 584         case KEY_SPEC_SESSION_KEYRING:
 585                 if (!cred->tgcred->session_keyring) {
 586                         /* always install a session keyring upon access if one
 587                          * doesn't exist yet */
 588                         ret = install_user_keyrings();
 589                         if (ret < 0)
 590                                 goto error;
 591                         if (lflags & KEY_LOOKUP_CREATE)
 592                                 ret = join_session_keyring(NULL);
 593                         else
 594                                 ret = install_session_keyring(
 595                                         cred->user->session_keyring);
 596
 597                         if (ret < 0)
 598                                 goto error;
 599                         goto reget_creds;
 600                 } else if (cred->tgcred->session_keyring ==
 601                            cred->user->session_keyring &&
 602                            lflags & KEY_LOOKUP_CREATE) {
 603                         ret = join_session_keyring(NULL);
 604                         if (ret < 0)
 605                                 goto error;
 606                         goto reget_creds;
 607                 }
 608
 609                 rcu_read_lock();
 610                 key = rcu_dereference(cred->tgcred->session_keyring);
 611                 atomic_inc(&key->usage);
 612                 rcu_read_unlock();
 613                 key_ref = make_key_ref(key, 1);
 614                 break;
 615
 616         case KEY_SPEC_USER_KEYRING:
 617                 if (!cred->user->uid_keyring) {
 618                         ret = install_user_keyrings();
 619                         if (ret < 0)
 620                                 goto error;
 621                 }
 622
 623                 key = cred->user->uid_keyring;
 624                 atomic_inc(&key->usage);
 625                 key_ref = make_key_ref(key, 1);
 626                 break;
 627
 628         case KEY_SPEC_USER_SESSION_KEYRING:
 629                 if (!cred->user->session_keyring) {
 630                         ret = install_user_keyrings();
 631                         if (ret < 0)
 632                                 goto error;
 633                 }
 634
 635                 key = cred->user->session_keyring;
 636                 atomic_inc(&key->usage);
 637                 key_ref = make_key_ref(key, 1);
 638                 break;
 639
 640         case KEY_SPEC_GROUP_KEYRING:
 641                 /* group keyrings are not yet supported */
 642                 key_ref = ERR_PTR(-EINVAL);
 643                 goto error;
 644
 645         case KEY_SPEC_REQKEY_AUTH_KEY:
 646                 key = cred->request_key_auth;
 647                 if (!key)
 648                         goto error;
 649
 650                 atomic_inc(&key->usage);
 651                 key_ref = make_key_ref(key, 1);
 652                 break;
 653
 654         case KEY_SPEC_REQUESTOR_KEYRING:
 655                 if (!cred->request_key_auth)
 656                         goto error;
 657
 658                 down_read(&cred->request_key_auth->sem);
 659                 if (test_bit(KEY_FLAG_REVOKED,
 660                              &cred->request_key_auth->flags)) {
 661                         key_ref = ERR_PTR(-EKEYREVOKED);
 662                         key = NULL;
 663                 } else {
 664                         rka = cred->request_key_auth->payload.data;
 665                         key = rka->dest_keyring;
 666                         atomic_inc(&key->usage);
 667                 }
 668                 up_read(&cred->request_key_auth->sem);
 669                 if (!key)
 670                         goto error;
 671                 key_ref = make_key_ref(key, 1);
 672                 break;
 673
 674         default:
 675                 key_ref = ERR_PTR(-EINVAL);
 676                 if (id < 1)
 677                         goto error;
 678
 679                 key = key_lookup(id);
 680                 if (IS_ERR(key)) {
 681                         key_ref = ERR_CAST(key);
 682                         goto error;
 683                 }
 684
 685                 key_ref = make_key_ref(key, 0);
 686
 687                 /* check to see if we possess the key */
 688                 skey_ref = search_process_keyrings(key->type, key,
 689                                                    lookup_user_key_possessed,
 690                                                    cred);
 691
 692                 if (!IS_ERR(skey_ref)) {
 693                         key_put(key);
 694                         key_ref = skey_ref;
 695                 }
 696
 697                 break;
 698         }
 699
 700         /* unlink does not use the nominated key in any way, so can skip all
 701          * the permission checks as it is only concerned with the keyring */
 702         if (lflags & KEY_LOOKUP_FOR_UNLINK) {
 703                 ret = 0;
 704                 goto error;
 705         }
 706
 707         if (!(lflags & KEY_LOOKUP_PARTIAL)) {
 708                 ret = wait_for_key_construction(key, true);
 709                 switch (ret) {
 710                 case -ERESTARTSYS:
 711                         goto invalid_key;
 712                 default:
 713                         if (perm)
 714                                 goto invalid_key;
 715                 case 0:
 716                         break;
 717                 }
 718         } else if (perm) {
 719                 ret = key_validate(key);
 720                 if (ret < 0)
 721                         goto invalid_key;
 722         }
 723
 724         ret = -EIO;
 725         if (!(lflags & KEY_LOOKUP_PARTIAL) &&
 726             !test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
 727                 goto invalid_key;
 728
 729         /* check the permissions */
 730         ret = key_task_permission(key_ref, cred, perm);
 731         if (ret < 0)
 732                 goto invalid_key;
 733
 734         key->last_used_at = current_kernel_time().tv_sec;
 735
 736 error:
 737         put_cred(cred);
 738         return key_ref;
 739
 740 invalid_key:
 741         key_ref_put(key_ref);
 742         key_ref = ERR_PTR(ret);
 743         goto error;
 744
 745         /* if we attempted to install a keyring, then it may have caused new
 746          * creds to be installed */
 747 reget_creds:
 748         put_cred(cred);
 749         goto try_again;
 750 }
 751
 752 /*
 753  * Join the named keyring as the session keyring if possible else attempt to
 754  * create a new one of that name and join that.
 755  *
 756  * If the name is NULL, an empty anonymous keyring will be installed as the
 757  * session keyring.
 758  *
 759  * Named session keyrings are joined with a semaphore held to prevent the
 760  * keyrings from going away whilst the attempt is made to going them and also
 761  * to prevent a race in creating compatible session keyrings.
 762  */
 763 long join_session_keyring(const char *name)
 764 {
 765         const struct cred *old;
 766         struct cred *new;
 767         struct key *keyring;
 768         long ret, serial;
 769
 770         /* only permit this if there's a single thread in the thread group -
 771          * this avoids us having to adjust the creds on all threads and risking
 772          * ENOMEM */
 773         if (!current_is_single_threaded())
 774                 return -EMLINK;
 775
 776         new = prepare_creds();
 777         if (!new)
 778                 return -ENOMEM;
 779         old = current_cred();
 780
 781         /* if no name is provided, install an anonymous keyring */
 782         if (!name) {
 783                 ret = install_session_keyring_to_cred(new, NULL);
 784                 if (ret < 0)
 785                         goto error;
 786
 787                 serial = new->tgcred->session_keyring->serial;
 788                 ret = commit_creds(new);
 789                 if (ret == 0)
 790                         ret = serial;
 791                 goto okay;
 792         }
 793
 794         /* allow the user to join or create a named keyring */
 795         mutex_lock(&key_session_mutex);
 796
 797         /* look for an existing keyring of this name */
 798         keyring = find_keyring_by_name(name, false);
 799         if (PTR_ERR(keyring) == -ENOKEY) {
 800                 /* not found - try and create a new one */
 801                 keyring = keyring_alloc(name, old->uid, old->gid, old,
 802                                         KEY_ALLOC_IN_QUOTA, NULL);
 803                 if (IS_ERR(keyring)) {
 804                         ret = PTR_ERR(keyring);
 805                         goto error2;
 806                 }
 807         } else if (IS_ERR(keyring)) {
 808                 ret = PTR_ERR(keyring);
 809                 goto error2;
 810         }
 811
 812         /* we've got a keyring - now to install it */
 813         ret = install_session_keyring_to_cred(new, keyring);
 814         if (ret < 0)
 815                 goto error2;
 816
 817         commit_creds(new);
 818         mutex_unlock(&key_session_mutex);
 819
 820         ret = keyring->serial;
 821         key_put(keyring);
 822 okay:
 823         return ret;
 824
 825 error2:
 826         mutex_unlock(&key_session_mutex);
 827 error:
 828         abort_creds(new);
 829         return ret;
 830 }
 831
 832 /*
 833  * Replace a process's session keyring on behalf of one of its children when
 834  * the target  process is about to resume userspace execution.
 835  */
 836 void key_change_session_keyring(struct callback_head *twork)
 837 {
 838         const struct cred *old = current_cred();
 839         struct cred *new = container_of(twork, struct cred, rcu);
 840
 841         if (unlikely(current->flags & PF_EXITING)) {
 842                 put_cred(new);
 843                 return;
 844         }
 845
 846         new->  uid      = old->  uid;
 847         new-> euid      = old-> euid;
 848         new-> suid      = old-> suid;
 849         new->fsuid      = old->fsuid;
 850         new->  gid      = old->  gid;
 851         new-> egid      = old-> egid;
 852         new-> sgid      = old-> sgid;
 853         new->fsgid      = old->fsgid;
 854         new->user       = get_uid(old->user);
 855         new->user_ns    = get_user_ns(new->user_ns);
 856         new->group_info = get_group_info(old->group_info);
 857
 858         new->securebits = old->securebits;
 859         new->cap_inheritable    = old->cap_inheritable;
 860         new->cap_permitted      = old->cap_permitted;
 861         new->cap_effective      = old->cap_effective;
 862         new->cap_bset           = old->cap_bset;
 863
 864         new->jit_keyring        = old->jit_keyring;
 865         new->thread_keyring     = key_get(old->thread_keyring);
 866         new->tgcred->tgid       = old->tgcred->tgid;
 867         new->tgcred->process_keyring = key_get(old->tgcred->process_keyring);
 868
 869         security_transfer_creds(new, old);
 870
 871         commit_creds(new);
 872 }