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