kernel/cred.c

   1 /* Task credentials management - see Documentation/credentials.txt
   2  *
   3  * Copyright (C) 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 Licence
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the Licence, or (at your option) any later version.
  10  */
  11 #include <linux/module.h>
  12 #include <linux/cred.h>
  13 #include <linux/sched.h>
  14 #include <linux/key.h>
  15 #include <linux/keyctl.h>
  16 #include <linux/init_task.h>
  17 #include <linux/security.h>
  18 #include <linux/cn_proc.h>
  19
  20 #if 0
  21 #define kdebug(FMT, ...) \
  22         printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
  23 #else
  24 static inline __attribute__((format(printf, 1, 2)))
  25 void no_printk(const char *fmt, ...)
  26 {
  27 }
  28 #define kdebug(FMT, ...) \
  29         no_printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
  30 #endif
  31
  32 static struct kmem_cache *cred_jar;
  33
  34 /*
  35  * The common credentials for the initial task's thread group
  36  */
  37 #ifdef CONFIG_KEYS
  38 static struct thread_group_cred init_tgcred = {
  39         .usage  = ATOMIC_INIT(2),
  40         .tgid   = 0,
  41         .lock   = SPIN_LOCK_UNLOCKED,
  42 };
  43 #endif
  44
  45 /*
  46  * The initial credentials for the initial task
  47  */
  48 struct cred init_cred = {
  49         .usage                  = ATOMIC_INIT(4),
  50 #ifdef CONFIG_DEBUG_CREDENTIALS
  51         .subscribers            = ATOMIC_INIT(2),
  52         .magic                  = CRED_MAGIC,
  53 #endif
  54         .securebits             = SECUREBITS_DEFAULT,
  55         .cap_inheritable        = CAP_INIT_INH_SET,
  56         .cap_permitted          = CAP_FULL_SET,
  57         .cap_effective          = CAP_INIT_EFF_SET,
  58         .cap_bset               = CAP_INIT_BSET,
  59         .user                   = INIT_USER,
  60         .group_info             = &init_groups,
  61 #ifdef CONFIG_KEYS
  62         .tgcred                 = &init_tgcred,
  63 #endif
  64 };
  65
  66 static inline void set_cred_subscribers(struct cred *cred, int n)
  67 {
  68 #ifdef CONFIG_DEBUG_CREDENTIALS
  69         atomic_set(&cred->subscribers, n);
  70 #endif
  71 }
  72
  73 static inline int read_cred_subscribers(const struct cred *cred)
  74 {
  75 #ifdef CONFIG_DEBUG_CREDENTIALS
  76         return atomic_read(&cred->subscribers);
  77 #else
  78         return 0;
  79 #endif
  80 }
  81
  82 static inline void alter_cred_subscribers(const struct cred *_cred, int n)
  83 {
  84 #ifdef CONFIG_DEBUG_CREDENTIALS
  85         struct cred *cred = (struct cred *) _cred;
  86
  87         atomic_add(n, &cred->subscribers);
  88 #endif
  89 }
  90
  91 /*
  92  * Dispose of the shared task group credentials
  93  */
  94 #ifdef CONFIG_KEYS
  95 static void release_tgcred_rcu(struct rcu_head *rcu)
  96 {
  97         struct thread_group_cred *tgcred =
  98                 container_of(rcu, struct thread_group_cred, rcu);
  99
 100         BUG_ON(atomic_read(&tgcred->usage) != 0);
 101
 102         key_put(tgcred->session_keyring);
 103         key_put(tgcred->process_keyring);
 104         kfree(tgcred);
 105 }
 106 #endif
 107
 108 /*
 109  * Release a set of thread group credentials.
 110  */
 111 static void release_tgcred(struct cred *cred)
 112 {
 113 #ifdef CONFIG_KEYS
 114         struct thread_group_cred *tgcred = cred->tgcred;
 115
 116         if (atomic_dec_and_test(&tgcred->usage))
 117                 call_rcu(&tgcred->rcu, release_tgcred_rcu);
 118 #endif
 119 }
 120
 121 /*
 122  * The RCU callback to actually dispose of a set of credentials
 123  */
 124 static void put_cred_rcu(struct rcu_head *rcu)
 125 {
 126         struct cred *cred = container_of(rcu, struct cred, rcu);
 127
 128         kdebug("put_cred_rcu(%p)", cred);
 129
 130 #ifdef CONFIG_DEBUG_CREDENTIALS
 131         if (cred->magic != CRED_MAGIC_DEAD ||
 132             atomic_read(&cred->usage) != 0 ||
 133             read_cred_subscribers(cred) != 0)
 134                 panic("CRED: put_cred_rcu() sees %p with"
 135                       " mag %x, put %p, usage %d, subscr %d\n",
 136                       cred, cred->magic, cred->put_addr,
 137                       atomic_read(&cred->usage),
 138                       read_cred_subscribers(cred));
 139 #else
 140         if (atomic_read(&cred->usage) != 0)
 141                 panic("CRED: put_cred_rcu() sees %p with usage %d\n",
 142                       cred, atomic_read(&cred->usage));
 143 #endif
 144
 145         security_cred_free(cred);
 146         key_put(cred->thread_keyring);
 147         key_put(cred->request_key_auth);
 148         release_tgcred(cred);
 149         if (cred->group_info)
 150                 put_group_info(cred->group_info);
 151         free_uid(cred->user);
 152         kmem_cache_free(cred_jar, cred);
 153 }
 154
 155 /**
 156  * __put_cred - Destroy a set of credentials
 157  * @cred: The record to release
 158  *
 159  * Destroy a set of credentials on which no references remain.
 160  */
 161 void __put_cred(struct cred *cred)
 162 {
 163         kdebug("__put_cred(%p{%d,%d})", cred,
 164                atomic_read(&cred->usage),
 165                read_cred_subscribers(cred));
 166
 167         BUG_ON(atomic_read(&cred->usage) != 0);
 168 #ifdef CONFIG_DEBUG_CREDENTIALS
 169         BUG_ON(read_cred_subscribers(cred) != 0);
 170         cred->magic = CRED_MAGIC_DEAD;
 171         cred->put_addr = __builtin_return_address(0);
 172 #endif
 173         BUG_ON(cred == current->cred);
 174         BUG_ON(cred == current->real_cred);
 175
 176         call_rcu(&cred->rcu, put_cred_rcu);
 177 }
 178 EXPORT_SYMBOL(__put_cred);
 179
 180 /*
 181  * Clean up a task's credentials when it exits
 182  */
 183 void exit_creds(struct task_struct *tsk)
 184 {
 185         struct cred *cred;
 186
 187         kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
 188                atomic_read(&tsk->cred->usage),
 189                read_cred_subscribers(tsk->cred));
 190
 191         cred = (struct cred *) tsk->real_cred;
 192         tsk->real_cred = NULL;
 193         validate_creds(cred);
 194         alter_cred_subscribers(cred, -1);
 195         put_cred(cred);
 196
 197         cred = (struct cred *) tsk->cred;
 198         tsk->cred = NULL;
 199         validate_creds(cred);
 200         alter_cred_subscribers(cred, -1);
 201         put_cred(cred);
 202
 203         cred = (struct cred *) tsk->replacement_session_keyring;
 204         if (cred) {
 205                 tsk->replacement_session_keyring = NULL;
 206                 validate_creds(cred);
 207                 put_cred(cred);
 208         }
 209 }
 210
 211 /**
 212  * get_task_cred - Get another task's objective credentials
 213  * @task: The task to query
 214  *
 215  * Get the objective credentials of a task, pinning them so that they can't go
 216  * away.  Accessing a task's credentials directly is not permitted.
 217  *
 218  * The caller must also make sure task doesn't get deleted, either by holding a
 219  * ref on task or by holding tasklist_lock to prevent it from being unlinked.
 220  */
 221 const struct cred *get_task_cred(struct task_struct *task)
 222 {
 223         const struct cred *cred;
 224
 225         rcu_read_lock();
 226
 227         do {
 228                 cred = __task_cred((task));
 229                 BUG_ON(!cred);
 230         } while (!atomic_inc_not_zero(&((struct cred *)cred)->usage));
 231
 232         rcu_read_unlock();
 233         return cred;
 234 }
 235
 236 /*
 237  * Allocate blank credentials, such that the credentials can be filled in at a
 238  * later date without risk of ENOMEM.
 239  */
 240 struct cred *cred_alloc_blank(void)
 241 {
 242         struct cred *new;
 243
 244         new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
 245         if (!new)
 246                 return NULL;
 247
 248 #ifdef CONFIG_KEYS
 249         new->tgcred = kzalloc(sizeof(*new->tgcred), GFP_KERNEL);
 250         if (!new->tgcred) {
 251                 kmem_cache_free(cred_jar, new);
 252                 return NULL;
 253         }
 254         atomic_set(&new->tgcred->usage, 1);
 255 #endif
 256
 257         atomic_set(&new->usage, 1);
 258 #ifdef CONFIG_DEBUG_CREDENTIALS
 259         new->magic = CRED_MAGIC;
 260 #endif
 261
 262         if (security_cred_alloc_blank(new, GFP_KERNEL) < 0)
 263                 goto error;
 264
 265         return new;
 266
 267 error:
 268         abort_creds(new);
 269         return NULL;
 270 }
 271
 272 /**
 273  * prepare_creds - Prepare a new set of credentials for modification
 274  *
 275  * Prepare a new set of task credentials for modification.  A task's creds
 276  * shouldn't generally be modified directly, therefore this function is used to
 277  * prepare a new copy, which the caller then modifies and then commits by
 278  * calling commit_creds().
 279  *
 280  * Preparation involves making a copy of the objective creds for modification.
 281  *
 282  * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
 283  *
 284  * Call commit_creds() or abort_creds() to clean up.
 285  */
 286 struct cred *prepare_creds(void)
 287 {
 288         struct task_struct *task = current;
 289         const struct cred *old;
 290         struct cred *new;
 291
 292         validate_process_creds();
 293
 294         new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
 295         if (!new)
 296                 return NULL;
 297
 298         kdebug("prepare_creds() alloc %p", new);
 299
 300         old = task->cred;
 301         memcpy(new, old, sizeof(struct cred));
 302
 303         atomic_set(&new->usage, 1);
 304         set_cred_subscribers(new, 0);
 305         get_group_info(new->group_info);
 306         get_uid(new->user);
 307
 308 #ifdef CONFIG_KEYS
 309         key_get(new->thread_keyring);
 310         key_get(new->request_key_auth);
 311         atomic_inc(&new->tgcred->usage);
 312 #endif
 313
 314 #ifdef CONFIG_SECURITY
 315         new->security = NULL;
 316 #endif
 317
 318         if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
 319                 goto error;
 320         validate_creds(new);
 321         return new;
 322
 323 error:
 324         abort_creds(new);
 325         return NULL;
 326 }
 327 EXPORT_SYMBOL(prepare_creds);
 328
 329 /*
 330  * Prepare credentials for current to perform an execve()
 331  * - The caller must hold current->cred_guard_mutex
 332  */
 333 struct cred *prepare_exec_creds(void)
 334 {
 335         struct thread_group_cred *tgcred = NULL;
 336         struct cred *new;
 337
 338 #ifdef CONFIG_KEYS
 339         tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
 340         if (!tgcred)
 341                 return NULL;
 342 #endif
 343
 344         new = prepare_creds();
 345         if (!new) {
 346                 kfree(tgcred);
 347                 return new;
 348         }
 349
 350 #ifdef CONFIG_KEYS
 351         /* newly exec'd tasks don't get a thread keyring */
 352         key_put(new->thread_keyring);
 353         new->thread_keyring = NULL;
 354
 355         /* create a new per-thread-group creds for all this set of threads to
 356          * share */
 357         memcpy(tgcred, new->tgcred, sizeof(struct thread_group_cred));
 358
 359         atomic_set(&tgcred->usage, 1);
 360         spin_lock_init(&tgcred->lock);
 361
 362         /* inherit the session keyring; new process keyring */
 363         key_get(tgcred->session_keyring);
 364         tgcred->process_keyring = NULL;
 365
 366         release_tgcred(new);
 367         new->tgcred = tgcred;
 368 #endif
 369
 370         return new;
 371 }
 372
 373 /*
 374  * prepare new credentials for the usermode helper dispatcher
 375  */
 376 struct cred *prepare_usermodehelper_creds(void)
 377 {
 378 #ifdef CONFIG_KEYS
 379         struct thread_group_cred *tgcred = NULL;
 380 #endif
 381         struct cred *new;
 382
 383 #ifdef CONFIG_KEYS
 384         tgcred = kzalloc(sizeof(*new->tgcred), GFP_ATOMIC);
 385         if (!tgcred)
 386                 return NULL;
 387 #endif
 388
 389         new = kmem_cache_alloc(cred_jar, GFP_ATOMIC);
 390         if (!new)
 391                 return NULL;
 392
 393         kdebug("prepare_usermodehelper_creds() alloc %p", new);
 394
 395         memcpy(new, &init_cred, sizeof(struct cred));
 396
 397         atomic_set(&new->usage, 1);
 398         set_cred_subscribers(new, 0);
 399         get_group_info(new->group_info);
 400         get_uid(new->user);
 401
 402 #ifdef CONFIG_KEYS
 403         new->thread_keyring = NULL;
 404         new->request_key_auth = NULL;
 405         new->jit_keyring = KEY_REQKEY_DEFL_DEFAULT;
 406
 407         atomic_set(&tgcred->usage, 1);
 408         spin_lock_init(&tgcred->lock);
 409         new->tgcred = tgcred;
 410 #endif
 411
 412 #ifdef CONFIG_SECURITY
 413         new->security = NULL;
 414 #endif
 415         if (security_prepare_creds(new, &init_cred, GFP_ATOMIC) < 0)
 416                 goto error;
 417         validate_creds(new);
 418
 419         BUG_ON(atomic_read(&new->usage) != 1);
 420         return new;
 421
 422 error:
 423         put_cred(new);
 424         return NULL;
 425 }
 426
 427 /*
 428  * Copy credentials for the new process created by fork()
 429  *
 430  * We share if we can, but under some circumstances we have to generate a new
 431  * set.
 432  *
 433  * The new process gets the current process's subjective credentials as its
 434  * objective and subjective credentials
 435  */
 436 int copy_creds(struct task_struct *p, unsigned long clone_flags)
 437 {
 438 #ifdef CONFIG_KEYS
 439         struct thread_group_cred *tgcred;
 440 #endif
 441         struct cred *new;
 442         int ret;
 443
 444         mutex_init(&p->cred_guard_mutex);
 445
 446         p->replacement_session_keyring = NULL;
 447
 448         if (
 449 #ifdef CONFIG_KEYS
 450                 !p->cred->thread_keyring &&
 451 #endif
 452                 clone_flags & CLONE_THREAD
 453             ) {
 454                 p->real_cred = get_cred(p->cred);
 455                 get_cred(p->cred);
 456                 alter_cred_subscribers(p->cred, 2);
 457                 kdebug("share_creds(%p{%d,%d})",
 458                        p->cred, atomic_read(&p->cred->usage),
 459                        read_cred_subscribers(p->cred));
 460                 atomic_inc(&p->cred->user->processes);
 461                 return 0;
 462         }
 463
 464         new = prepare_creds();
 465         if (!new)
 466                 return -ENOMEM;
 467
 468         if (clone_flags & CLONE_NEWUSER) {
 469                 ret = create_user_ns(new);
 470                 if (ret < 0)
 471                         goto error_put;
 472         }
 473
 474 #ifdef CONFIG_KEYS
 475         /* new threads get their own thread keyrings if their parent already
 476          * had one */
 477         if (new->thread_keyring) {
 478                 key_put(new->thread_keyring);
 479                 new->thread_keyring = NULL;
 480                 if (clone_flags & CLONE_THREAD)
 481                         install_thread_keyring_to_cred(new);
 482         }
 483
 484         /* we share the process and session keyrings between all the threads in
 485          * a process - this is slightly icky as we violate COW credentials a
 486          * bit */
 487         if (!(clone_flags & CLONE_THREAD)) {
 488                 tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
 489                 if (!tgcred) {
 490                         ret = -ENOMEM;
 491                         goto error_put;
 492                 }
 493                 atomic_set(&tgcred->usage, 1);
 494                 spin_lock_init(&tgcred->lock);
 495                 tgcred->process_keyring = NULL;
 496                 tgcred->session_keyring = key_get(new->tgcred->session_keyring);
 497
 498                 release_tgcred(new);
 499                 new->tgcred = tgcred;
 500         }
 501 #endif
 502
 503         atomic_inc(&new->user->processes);
 504         p->cred = p->real_cred = get_cred(new);
 505         alter_cred_subscribers(new, 2);
 506         validate_creds(new);
 507         return 0;
 508
 509 error_put:
 510         put_cred(new);
 511         return ret;
 512 }
 513
 514 /**
 515  * commit_creds - Install new credentials upon the current task
 516  * @new: The credentials to be assigned
 517  *
 518  * Install a new set of credentials to the current task, using RCU to replace
 519  * the old set.  Both the objective and the subjective credentials pointers are
 520  * updated.  This function may not be called if the subjective credentials are
 521  * in an overridden state.
 522  *
 523  * This function eats the caller's reference to the new credentials.
 524  *
 525  * Always returns 0 thus allowing this function to be tail-called at the end
 526  * of, say, sys_setgid().
 527  */
 528 int commit_creds(struct cred *new)
 529 {
 530         struct task_struct *task = current;
 531         const struct cred *old = task->real_cred;
 532
 533         kdebug("commit_creds(%p{%d,%d})", new,
 534                atomic_read(&new->usage),
 535                read_cred_subscribers(new));
 536
 537         BUG_ON(task->cred != old);
 538 #ifdef CONFIG_DEBUG_CREDENTIALS
 539         BUG_ON(read_cred_subscribers(old) < 2);
 540         validate_creds(old);
 541         validate_creds(new);
 542 #endif
 543         BUG_ON(atomic_read(&new->usage) < 1);
 544
 545         security_commit_creds(new, old);
 546
 547         get_cred(new); /* we will require a ref for the subj creds too */
 548
 549         /* dumpability changes */
 550         if (old->euid != new->euid ||
 551             old->egid != new->egid ||
 552             old->fsuid != new->fsuid ||
 553             old->fsgid != new->fsgid ||
 554             !cap_issubset(new->cap_permitted, old->cap_permitted)) {
 555                 if (task->mm)
 556                         set_dumpable(task->mm, suid_dumpable);
 557                 task->pdeath_signal = 0;
 558                 smp_wmb();
 559         }
 560
 561         /* alter the thread keyring */
 562         if (new->fsuid != old->fsuid)
 563                 key_fsuid_changed(task);
 564         if (new->fsgid != old->fsgid)
 565                 key_fsgid_changed(task);
 566
 567         /* do it
 568          * - What if a process setreuid()'s and this brings the
 569          *   new uid over his NPROC rlimit?  We can check this now
 570          *   cheaply with the new uid cache, so if it matters
 571          *   we should be checking for it.  -DaveM
 572          */
 573         alter_cred_subscribers(new, 2);
 574         if (new->user != old->user)
 575                 atomic_inc(&new->user->processes);
 576         rcu_assign_pointer(task->real_cred, new);
 577         rcu_assign_pointer(task->cred, new);
 578         if (new->user != old->user)
 579                 atomic_dec(&old->user->processes);
 580         alter_cred_subscribers(old, -2);
 581
 582         /* send notifications */
 583         if (new->uid   != old->uid  ||
 584             new->euid  != old->euid ||
 585             new->suid  != old->suid ||
 586             new->fsuid != old->fsuid)
 587                 proc_id_connector(task, PROC_EVENT_UID);
 588
 589         if (new->gid   != old->gid  ||
 590             new->egid  != old->egid ||
 591             new->sgid  != old->sgid ||
 592             new->fsgid != old->fsgid)
 593                 proc_id_connector(task, PROC_EVENT_GID);
 594
 595         /* release the old obj and subj refs both */
 596         put_cred(old);
 597         put_cred(old);
 598         return 0;
 599 }
 600 EXPORT_SYMBOL(commit_creds);
 601
 602 /**
 603  * abort_creds - Discard a set of credentials and unlock the current task
 604  * @new: The credentials that were going to be applied
 605  *
 606  * Discard a set of credentials that were under construction and unlock the
 607  * current task.
 608  */
 609 void abort_creds(struct cred *new)
 610 {
 611         kdebug("abort_creds(%p{%d,%d})", new,
 612                atomic_read(&new->usage),
 613                read_cred_subscribers(new));
 614
 615 #ifdef CONFIG_DEBUG_CREDENTIALS
 616         BUG_ON(read_cred_subscribers(new) != 0);
 617 #endif
 618         BUG_ON(atomic_read(&new->usage) < 1);
 619         put_cred(new);
 620 }
 621 EXPORT_SYMBOL(abort_creds);
 622
 623 /**
 624  * override_creds - Override the current process's subjective credentials
 625  * @new: The credentials to be assigned
 626  *
 627  * Install a set of temporary override subjective credentials on the current
 628  * process, returning the old set for later reversion.
 629  */
 630 const struct cred *override_creds(const struct cred *new)
 631 {
 632         const struct cred *old = current->cred;
 633
 634         kdebug("override_creds(%p{%d,%d})", new,
 635                atomic_read(&new->usage),
 636                read_cred_subscribers(new));
 637
 638         validate_creds(old);
 639         validate_creds(new);
 640         get_cred(new);
 641         alter_cred_subscribers(new, 1);
 642         rcu_assign_pointer(current->cred, new);
 643         alter_cred_subscribers(old, -1);
 644
 645         kdebug("override_creds() = %p{%d,%d}", old,
 646                atomic_read(&old->usage),
 647                read_cred_subscribers(old));
 648         return old;
 649 }
 650 EXPORT_SYMBOL(override_creds);
 651
 652 /**
 653  * revert_creds - Revert a temporary subjective credentials override
 654  * @old: The credentials to be restored
 655  *
 656  * Revert a temporary set of override subjective credentials to an old set,
 657  * discarding the override set.
 658  */
 659 void revert_creds(const struct cred *old)
 660 {
 661         const struct cred *override = current->cred;
 662
 663         kdebug("revert_creds(%p{%d,%d})", old,
 664                atomic_read(&old->usage),
 665                read_cred_subscribers(old));
 666
 667         validate_creds(old);
 668         validate_creds(override);
 669         alter_cred_subscribers(old, 1);
 670         rcu_assign_pointer(current->cred, old);
 671         alter_cred_subscribers(override, -1);
 672         put_cred(override);
 673 }
 674 EXPORT_SYMBOL(revert_creds);
 675
 676 /*
 677  * initialise the credentials stuff
 678  */
 679 void __init cred_init(void)
 680 {
 681         /* allocate a slab in which we can store credentials */
 682         cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred),
 683                                      0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
 684 }
 685
 686 /**
 687  * prepare_kernel_cred - Prepare a set of credentials for a kernel service
 688  * @daemon: A userspace daemon to be used as a reference
 689  *
 690  * Prepare a set of credentials for a kernel service.  This can then be used to
 691  * override a task's own credentials so that work can be done on behalf of that
 692  * task that requires a different subjective context.
 693  *
 694  * @daemon is used to provide a base for the security record, but can be NULL.
 695  * If @daemon is supplied, then the security data will be derived from that;
 696  * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
 697  *
 698  * The caller may change these controls afterwards if desired.
 699  *
 700  * Returns the new credentials or NULL if out of memory.
 701  *
 702  * Does not take, and does not return holding current->cred_replace_mutex.
 703  */
 704 struct cred *prepare_kernel_cred(struct task_struct *daemon)
 705 {
 706         const struct cred *old;
 707         struct cred *new;
 708
 709         new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
 710         if (!new)
 711                 return NULL;
 712
 713         kdebug("prepare_kernel_cred() alloc %p", new);
 714
 715         if (daemon)
 716                 old = get_task_cred(daemon);
 717         else
 718                 old = get_cred(&init_cred);
 719
 720         validate_creds(old);
 721
 722         *new = *old;
 723         atomic_set(&new->usage, 1);
 724         set_cred_subscribers(new, 0);
 725         get_uid(new->user);
 726         get_group_info(new->group_info);
 727
 728 #ifdef CONFIG_KEYS
 729         atomic_inc(&init_tgcred.usage);
 730         new->tgcred = &init_tgcred;
 731         new->request_key_auth = NULL;
 732         new->thread_keyring = NULL;
 733         new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
 734 #endif
 735
 736 #ifdef CONFIG_SECURITY
 737         new->security = NULL;
 738 #endif
 739         if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
 740                 goto error;
 741
 742         put_cred(old);
 743         validate_creds(new);
 744         return new;
 745
 746 error:
 747         put_cred(new);
 748         put_cred(old);
 749         return NULL;
 750 }
 751 EXPORT_SYMBOL(prepare_kernel_cred);
 752
 753 /**
 754  * set_security_override - Set the security ID in a set of credentials
 755  * @new: The credentials to alter
 756  * @secid: The LSM security ID to set
 757  *
 758  * Set the LSM security ID in a set of credentials so that the subjective
 759  * security is overridden when an alternative set of credentials is used.
 760  */
 761 int set_security_override(struct cred *new, u32 secid)
 762 {
 763         return security_kernel_act_as(new, secid);
 764 }
 765 EXPORT_SYMBOL(set_security_override);
 766
 767 /**
 768  * set_security_override_from_ctx - Set the security ID in a set of credentials
 769  * @new: The credentials to alter
 770  * @secctx: The LSM security context to generate the security ID from.
 771  *
 772  * Set the LSM security ID in a set of credentials so that the subjective
 773  * security is overridden when an alternative set of credentials is used.  The
 774  * security ID is specified in string form as a security context to be
 775  * interpreted by the LSM.
 776  */
 777 int set_security_override_from_ctx(struct cred *new, const char *secctx)
 778 {
 779         u32 secid;
 780         int ret;
 781
 782         ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
 783         if (ret < 0)
 784                 return ret;
 785
 786         return set_security_override(new, secid);
 787 }
 788 EXPORT_SYMBOL(set_security_override_from_ctx);
 789
 790 /**
 791  * set_create_files_as - Set the LSM file create context in a set of credentials
 792  * @new: The credentials to alter
 793  * @inode: The inode to take the context from
 794  *
 795  * Change the LSM file creation context in a set of credentials to be the same
 796  * as the object context of the specified inode, so that the new inodes have
 797  * the same MAC context as that inode.
 798  */
 799 int set_create_files_as(struct cred *new, struct inode *inode)
 800 {
 801         new->fsuid = inode->i_uid;
 802         new->fsgid = inode->i_gid;
 803         return security_kernel_create_files_as(new, inode);
 804 }
 805 EXPORT_SYMBOL(set_create_files_as);
 806
 807 #ifdef CONFIG_DEBUG_CREDENTIALS
 808
 809 bool creds_are_invalid(const struct cred *cred)
 810 {
 811         if (cred->magic != CRED_MAGIC)
 812                 return true;
 813 #ifdef CONFIG_SECURITY_SELINUX
 814         /*
 815          * cred->security == NULL if security_cred_alloc_blank() or
 816          * security_prepare_creds() returned an error.
 817          */
 818         if (selinux_is_enabled() && cred->security) {
 819                 if ((unsigned long) cred->security < PAGE_SIZE)
 820                         return true;
 821                 if ((*(u32 *)cred->security & 0xffffff00) ==
 822                     (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
 823                         return true;
 824         }
 825 #endif
 826         return false;
 827 }
 828 EXPORT_SYMBOL(creds_are_invalid);
 829
 830 /*
 831  * dump invalid credentials
 832  */
 833 static void dump_invalid_creds(const struct cred *cred, const char *label,
 834                                const struct task_struct *tsk)
 835 {
 836         printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
 837                label, cred,
 838                cred == &init_cred ? "[init]" : "",
 839                cred == tsk->real_cred ? "[real]" : "",
 840                cred == tsk->cred ? "[eff]" : "");
 841         printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
 842                cred->magic, cred->put_addr);
 843         printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
 844                atomic_read(&cred->usage),
 845                read_cred_subscribers(cred));
 846         printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
 847                cred->uid, cred->euid, cred->suid, cred->fsuid);
 848         printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
 849                cred->gid, cred->egid, cred->sgid, cred->fsgid);
 850 #ifdef CONFIG_SECURITY
 851         printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
 852         if ((unsigned long) cred->security >= PAGE_SIZE &&
 853             (((unsigned long) cred->security & 0xffffff00) !=
 854              (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
 855                 printk(KERN_ERR "CRED: ->security {%x, %x}\n",
 856                        ((u32*)cred->security)[0],
 857                        ((u32*)cred->security)[1]);
 858 #endif
 859 }
 860
 861 /*
 862  * report use of invalid credentials
 863  */
 864 void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
 865 {
 866         printk(KERN_ERR "CRED: Invalid credentials\n");
 867         printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 868         dump_invalid_creds(cred, "Specified", current);
 869         BUG();
 870 }
 871 EXPORT_SYMBOL(__invalid_creds);
 872
 873 /*
 874  * check the credentials on a process
 875  */
 876 void __validate_process_creds(struct task_struct *tsk,
 877                               const char *file, unsigned line)
 878 {
 879         if (tsk->cred == tsk->real_cred) {
 880                 if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
 881                              creds_are_invalid(tsk->cred)))
 882                         goto invalid_creds;
 883         } else {
 884                 if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
 885                              read_cred_subscribers(tsk->cred) < 1 ||
 886                              creds_are_invalid(tsk->real_cred) ||
 887                              creds_are_invalid(tsk->cred)))
 888                         goto invalid_creds;
 889         }
 890         return;
 891
 892 invalid_creds:
 893         printk(KERN_ERR "CRED: Invalid process credentials\n");
 894         printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 895
 896         dump_invalid_creds(tsk->real_cred, "Real", tsk);
 897         if (tsk->cred != tsk->real_cred)
 898                 dump_invalid_creds(tsk->cred, "Effective", tsk);
 899         else
 900                 printk(KERN_ERR "CRED: Effective creds == Real creds\n");
 901         BUG();
 902 }
 903 EXPORT_SYMBOL(__validate_process_creds);
 904
 905 /*
 906  * check creds for do_exit()
 907  */
 908 void validate_creds_for_do_exit(struct task_struct *tsk)
 909 {
 910         kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
 911                tsk->real_cred, tsk->cred,
 912                atomic_read(&tsk->cred->usage),
 913                read_cred_subscribers(tsk->cred));
 914
 915         __validate_process_creds(tsk, __FILE__, __LINE__);
 916 }
 917
 918 #endif /* CONFIG_DEBUG_CREDENTIALS */