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