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