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         if (
 447 #ifdef CONFIG_KEYS
 448                 !p->cred->thread_keyring &&
 449 #endif
 450                 clone_flags & CLONE_THREAD
 451             ) {
 452                 p->real_cred = get_cred(p->cred);
 453                 get_cred(p->cred);
 454                 alter_cred_subscribers(p->cred, 2);
 455                 kdebug("share_creds(%p{%d,%d})",
 456                        p->cred, atomic_read(&p->cred->usage),
 457                        read_cred_subscribers(p->cred));
 458                 atomic_inc(&p->cred->user->processes);
 459                 return 0;
 460         }
 461
 462         new = prepare_creds();
 463         if (!new)
 464                 return -ENOMEM;
 465
 466         if (clone_flags & CLONE_NEWUSER) {
 467                 ret = create_user_ns(new);
 468                 if (ret < 0)
 469                         goto error_put;
 470         }
 471
 472 #ifdef CONFIG_KEYS
 473         /* new threads get their own thread keyrings if their parent already
 474          * had one */
 475         if (new->thread_keyring) {
 476                 key_put(new->thread_keyring);
 477                 new->thread_keyring = NULL;
 478                 if (clone_flags & CLONE_THREAD)
 479                         install_thread_keyring_to_cred(new);
 480         }
 481
 482         /* we share the process and session keyrings between all the threads in
 483          * a process - this is slightly icky as we violate COW credentials a
 484          * bit */
 485         if (!(clone_flags & CLONE_THREAD)) {
 486                 tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
 487                 if (!tgcred) {
 488                         ret = -ENOMEM;
 489                         goto error_put;
 490                 }
 491                 atomic_set(&tgcred->usage, 1);
 492                 spin_lock_init(&tgcred->lock);
 493                 tgcred->process_keyring = NULL;
 494                 tgcred->session_keyring = key_get(new->tgcred->session_keyring);
 495
 496                 release_tgcred(new);
 497                 new->tgcred = tgcred;
 498         }
 499 #endif
 500
 501         atomic_inc(&new->user->processes);
 502         p->cred = p->real_cred = get_cred(new);
 503         alter_cred_subscribers(new, 2);
 504         validate_creds(new);
 505         return 0;
 506
 507 error_put:
 508         put_cred(new);
 509         return ret;
 510 }
 511
 512 /**
 513  * commit_creds - Install new credentials upon the current task
 514  * @new: The credentials to be assigned
 515  *
 516  * Install a new set of credentials to the current task, using RCU to replace
 517  * the old set.  Both the objective and the subjective credentials pointers are
 518  * updated.  This function may not be called if the subjective credentials are
 519  * in an overridden state.
 520  *
 521  * This function eats the caller's reference to the new credentials.
 522  *
 523  * Always returns 0 thus allowing this function to be tail-called at the end
 524  * of, say, sys_setgid().
 525  */
 526 int commit_creds(struct cred *new)
 527 {
 528         struct task_struct *task = current;
 529         const struct cred *old = task->real_cred;
 530
 531         kdebug("commit_creds(%p{%d,%d})", new,
 532                atomic_read(&new->usage),
 533                read_cred_subscribers(new));
 534
 535         BUG_ON(task->cred != old);
 536 #ifdef CONFIG_DEBUG_CREDENTIALS
 537         BUG_ON(read_cred_subscribers(old) < 2);
 538         validate_creds(old);
 539         validate_creds(new);
 540 #endif
 541         BUG_ON(atomic_read(&new->usage) < 1);
 542
 543         security_commit_creds(new, old);
 544
 545         get_cred(new); /* we will require a ref for the subj creds too */
 546
 547         /* dumpability changes */
 548         if (old->euid != new->euid ||
 549             old->egid != new->egid ||
 550             old->fsuid != new->fsuid ||
 551             old->fsgid != new->fsgid ||
 552             !cap_issubset(new->cap_permitted, old->cap_permitted)) {
 553                 if (task->mm)
 554                         set_dumpable(task->mm, suid_dumpable);
 555                 task->pdeath_signal = 0;
 556                 smp_wmb();
 557         }
 558
 559         /* alter the thread keyring */
 560         if (new->fsuid != old->fsuid)
 561                 key_fsuid_changed(task);
 562         if (new->fsgid != old->fsgid)
 563                 key_fsgid_changed(task);
 564
 565         /* do it
 566          * - What if a process setreuid()'s and this brings the
 567          *   new uid over his NPROC rlimit?  We can check this now
 568          *   cheaply with the new uid cache, so if it matters
 569          *   we should be checking for it.  -DaveM
 570          */
 571         alter_cred_subscribers(new, 2);
 572         if (new->user != old->user)
 573                 atomic_inc(&new->user->processes);
 574         rcu_assign_pointer(task->real_cred, new);
 575         rcu_assign_pointer(task->cred, new);
 576         if (new->user != old->user)
 577                 atomic_dec(&old->user->processes);
 578         alter_cred_subscribers(old, -2);
 579
 580         /* send notifications */
 581         if (new->uid   != old->uid  ||
 582             new->euid  != old->euid ||
 583             new->suid  != old->suid ||
 584             new->fsuid != old->fsuid)
 585                 proc_id_connector(task, PROC_EVENT_UID);
 586
 587         if (new->gid   != old->gid  ||
 588             new->egid  != old->egid ||
 589             new->sgid  != old->sgid ||
 590             new->fsgid != old->fsgid)
 591                 proc_id_connector(task, PROC_EVENT_GID);
 592
 593         /* release the old obj and subj refs both */
 594         put_cred(old);
 595         put_cred(old);
 596         return 0;
 597 }
 598 EXPORT_SYMBOL(commit_creds);
 599
 600 /**
 601  * abort_creds - Discard a set of credentials and unlock the current task
 602  * @new: The credentials that were going to be applied
 603  *
 604  * Discard a set of credentials that were under construction and unlock the
 605  * current task.
 606  */
 607 void abort_creds(struct cred *new)
 608 {
 609         kdebug("abort_creds(%p{%d,%d})", new,
 610                atomic_read(&new->usage),
 611                read_cred_subscribers(new));
 612
 613 #ifdef CONFIG_DEBUG_CREDENTIALS
 614         BUG_ON(read_cred_subscribers(new) != 0);
 615 #endif
 616         BUG_ON(atomic_read(&new->usage) < 1);
 617         put_cred(new);
 618 }
 619 EXPORT_SYMBOL(abort_creds);
 620
 621 /**
 622  * override_creds - Override the current process's subjective credentials
 623  * @new: The credentials to be assigned
 624  *
 625  * Install a set of temporary override subjective credentials on the current
 626  * process, returning the old set for later reversion.
 627  */
 628 const struct cred *override_creds(const struct cred *new)
 629 {
 630         const struct cred *old = current->cred;
 631
 632         kdebug("override_creds(%p{%d,%d})", new,
 633                atomic_read(&new->usage),
 634                read_cred_subscribers(new));
 635
 636         validate_creds(old);
 637         validate_creds(new);
 638         get_cred(new);
 639         alter_cred_subscribers(new, 1);
 640         rcu_assign_pointer(current->cred, new);
 641         alter_cred_subscribers(old, -1);
 642
 643         kdebug("override_creds() = %p{%d,%d}", old,
 644                atomic_read(&old->usage),
 645                read_cred_subscribers(old));
 646         return old;
 647 }
 648 EXPORT_SYMBOL(override_creds);
 649
 650 /**
 651  * revert_creds - Revert a temporary subjective credentials override
 652  * @old: The credentials to be restored
 653  *
 654  * Revert a temporary set of override subjective credentials to an old set,
 655  * discarding the override set.
 656  */
 657 void revert_creds(const struct cred *old)
 658 {
 659         const struct cred *override = current->cred;
 660
 661         kdebug("revert_creds(%p{%d,%d})", old,
 662                atomic_read(&old->usage),
 663                read_cred_subscribers(old));
 664
 665         validate_creds(old);
 666         validate_creds(override);
 667         alter_cred_subscribers(old, 1);
 668         rcu_assign_pointer(current->cred, old);
 669         alter_cred_subscribers(override, -1);
 670         put_cred(override);
 671 }
 672 EXPORT_SYMBOL(revert_creds);
 673
 674 /*
 675  * initialise the credentials stuff
 676  */
 677 void __init cred_init(void)
 678 {
 679         /* allocate a slab in which we can store credentials */
 680         cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred),
 681                                      0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
 682 }
 683
 684 /**
 685  * prepare_kernel_cred - Prepare a set of credentials for a kernel service
 686  * @daemon: A userspace daemon to be used as a reference
 687  *
 688  * Prepare a set of credentials for a kernel service.  This can then be used to
 689  * override a task's own credentials so that work can be done on behalf of that
 690  * task that requires a different subjective context.
 691  *
 692  * @daemon is used to provide a base for the security record, but can be NULL.
 693  * If @daemon is supplied, then the security data will be derived from that;
 694  * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
 695  *
 696  * The caller may change these controls afterwards if desired.
 697  *
 698  * Returns the new credentials or NULL if out of memory.
 699  *
 700  * Does not take, and does not return holding current->cred_replace_mutex.
 701  */
 702 struct cred *prepare_kernel_cred(struct task_struct *daemon)
 703 {
 704         const struct cred *old;
 705         struct cred *new;
 706
 707         new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
 708         if (!new)
 709                 return NULL;
 710
 711         kdebug("prepare_kernel_cred() alloc %p", new);
 712
 713         if (daemon)
 714                 old = get_task_cred(daemon);
 715         else
 716                 old = get_cred(&init_cred);
 717
 718         validate_creds(old);
 719
 720         *new = *old;
 721         atomic_set(&new->usage, 1);
 722         set_cred_subscribers(new, 0);
 723         get_uid(new->user);
 724         get_group_info(new->group_info);
 725
 726 #ifdef CONFIG_KEYS
 727         atomic_inc(&init_tgcred.usage);
 728         new->tgcred = &init_tgcred;
 729         new->request_key_auth = NULL;
 730         new->thread_keyring = NULL;
 731         new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
 732 #endif
 733
 734 #ifdef CONFIG_SECURITY
 735         new->security = NULL;
 736 #endif
 737         if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
 738                 goto error;
 739
 740         put_cred(old);
 741         validate_creds(new);
 742         return new;
 743
 744 error:
 745         put_cred(new);
 746         put_cred(old);
 747         return NULL;
 748 }
 749 EXPORT_SYMBOL(prepare_kernel_cred);
 750
 751 /**
 752  * set_security_override - Set the security ID in a set of credentials
 753  * @new: The credentials to alter
 754  * @secid: The LSM security ID to set
 755  *
 756  * Set the LSM security ID in a set of credentials so that the subjective
 757  * security is overridden when an alternative set of credentials is used.
 758  */
 759 int set_security_override(struct cred *new, u32 secid)
 760 {
 761         return security_kernel_act_as(new, secid);
 762 }
 763 EXPORT_SYMBOL(set_security_override);
 764
 765 /**
 766  * set_security_override_from_ctx - Set the security ID in a set of credentials
 767  * @new: The credentials to alter
 768  * @secctx: The LSM security context to generate the security ID from.
 769  *
 770  * Set the LSM security ID in a set of credentials so that the subjective
 771  * security is overridden when an alternative set of credentials is used.  The
 772  * security ID is specified in string form as a security context to be
 773  * interpreted by the LSM.
 774  */
 775 int set_security_override_from_ctx(struct cred *new, const char *secctx)
 776 {
 777         u32 secid;
 778         int ret;
 779
 780         ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
 781         if (ret < 0)
 782                 return ret;
 783
 784         return set_security_override(new, secid);
 785 }
 786 EXPORT_SYMBOL(set_security_override_from_ctx);
 787
 788 /**
 789  * set_create_files_as - Set the LSM file create context in a set of credentials
 790  * @new: The credentials to alter
 791  * @inode: The inode to take the context from
 792  *
 793  * Change the LSM file creation context in a set of credentials to be the same
 794  * as the object context of the specified inode, so that the new inodes have
 795  * the same MAC context as that inode.
 796  */
 797 int set_create_files_as(struct cred *new, struct inode *inode)
 798 {
 799         new->fsuid = inode->i_uid;
 800         new->fsgid = inode->i_gid;
 801         return security_kernel_create_files_as(new, inode);
 802 }
 803 EXPORT_SYMBOL(set_create_files_as);
 804
 805 #ifdef CONFIG_DEBUG_CREDENTIALS
 806
 807 bool creds_are_invalid(const struct cred *cred)
 808 {
 809         if (cred->magic != CRED_MAGIC)
 810                 return true;
 811 #ifdef CONFIG_SECURITY_SELINUX
 812         /*
 813          * cred->security == NULL if security_cred_alloc_blank() or
 814          * security_prepare_creds() returned an error.
 815          */
 816         if (selinux_is_enabled() && cred->security) {
 817                 if ((unsigned long) cred->security < PAGE_SIZE)
 818                         return true;
 819                 if ((*(u32 *)cred->security & 0xffffff00) ==
 820                     (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
 821                         return true;
 822         }
 823 #endif
 824         return false;
 825 }
 826 EXPORT_SYMBOL(creds_are_invalid);
 827
 828 /*
 829  * dump invalid credentials
 830  */
 831 static void dump_invalid_creds(const struct cred *cred, const char *label,
 832                                const struct task_struct *tsk)
 833 {
 834         printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
 835                label, cred,
 836                cred == &init_cred ? "[init]" : "",
 837                cred == tsk->real_cred ? "[real]" : "",
 838                cred == tsk->cred ? "[eff]" : "");
 839         printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
 840                cred->magic, cred->put_addr);
 841         printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
 842                atomic_read(&cred->usage),
 843                read_cred_subscribers(cred));
 844         printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
 845                cred->uid, cred->euid, cred->suid, cred->fsuid);
 846         printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
 847                cred->gid, cred->egid, cred->sgid, cred->fsgid);
 848 #ifdef CONFIG_SECURITY
 849         printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
 850         if ((unsigned long) cred->security >= PAGE_SIZE &&
 851             (((unsigned long) cred->security & 0xffffff00) !=
 852              (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
 853                 printk(KERN_ERR "CRED: ->security {%x, %x}\n",
 854                        ((u32*)cred->security)[0],
 855                        ((u32*)cred->security)[1]);
 856 #endif
 857 }
 858
 859 /*
 860  * report use of invalid credentials
 861  */
 862 void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
 863 {
 864         printk(KERN_ERR "CRED: Invalid credentials\n");
 865         printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 866         dump_invalid_creds(cred, "Specified", current);
 867         BUG();
 868 }
 869 EXPORT_SYMBOL(__invalid_creds);
 870
 871 /*
 872  * check the credentials on a process
 873  */
 874 void __validate_process_creds(struct task_struct *tsk,
 875                               const char *file, unsigned line)
 876 {
 877         if (tsk->cred == tsk->real_cred) {
 878                 if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
 879                              creds_are_invalid(tsk->cred)))
 880                         goto invalid_creds;
 881         } else {
 882                 if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
 883                              read_cred_subscribers(tsk->cred) < 1 ||
 884                              creds_are_invalid(tsk->real_cred) ||
 885                              creds_are_invalid(tsk->cred)))
 886                         goto invalid_creds;
 887         }
 888         return;
 889
 890 invalid_creds:
 891         printk(KERN_ERR "CRED: Invalid process credentials\n");
 892         printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 893
 894         dump_invalid_creds(tsk->real_cred, "Real", tsk);
 895         if (tsk->cred != tsk->real_cred)
 896                 dump_invalid_creds(tsk->cred, "Effective", tsk);
 897         else
 898                 printk(KERN_ERR "CRED: Effective creds == Real creds\n");
 899         BUG();
 900 }
 901 EXPORT_SYMBOL(__validate_process_creds);
 902
 903 /*
 904  * check creds for do_exit()
 905  */
 906 void validate_creds_for_do_exit(struct task_struct *tsk)
 907 {
 908         kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
 909                tsk->real_cred, tsk->cred,
 910                atomic_read(&tsk->cred->usage),
 911                read_cred_subscribers(tsk->cred));
 912
 913         __validate_process_creds(tsk, __FILE__, __LINE__);
 914 }
 915
 916 #endif /* CONFIG_DEBUG_CREDENTIALS */