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  * 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                 kfree(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                 return NULL;
 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
 403 /*
 404  * Copy credentials for the new process created by fork()
 405  *
 406  * We share if we can, but under some circumstances we have to generate a new
 407  * set.
 408  *
 409  * The new process gets the current process's subjective credentials as its
 410  * objective and subjective credentials
 411  */
 412 int copy_creds(struct task_struct *p, unsigned long clone_flags)
 413 {
 414 #ifdef CONFIG_KEYS
 415         struct thread_group_cred *tgcred;
 416 #endif
 417         struct cred *new;
 418         int ret;
 419
 420         mutex_init(&p->cred_guard_mutex);
 421
 422         if (
 423 #ifdef CONFIG_KEYS
 424                 !p->cred->thread_keyring &&
 425 #endif
 426                 clone_flags & CLONE_THREAD
 427             ) {
 428                 p->real_cred = get_cred(p->cred);
 429                 get_cred(p->cred);
 430                 alter_cred_subscribers(p->cred, 2);
 431                 kdebug("share_creds(%p{%d,%d})",
 432                        p->cred, atomic_read(&p->cred->usage),
 433                        read_cred_subscribers(p->cred));
 434                 atomic_inc(&p->cred->user->processes);
 435                 return 0;
 436         }
 437
 438         new = prepare_creds();
 439         if (!new)
 440                 return -ENOMEM;
 441
 442         if (clone_flags & CLONE_NEWUSER) {
 443                 ret = create_user_ns(new);
 444                 if (ret < 0)
 445                         goto error_put;
 446         }
 447
 448 #ifdef CONFIG_KEYS
 449         /* new threads get their own thread keyrings if their parent already
 450          * had one */
 451         if (new->thread_keyring) {
 452                 key_put(new->thread_keyring);
 453                 new->thread_keyring = NULL;
 454                 if (clone_flags & CLONE_THREAD)
 455                         install_thread_keyring_to_cred(new);
 456         }
 457
 458         /* we share the process and session keyrings between all the threads in
 459          * a process - this is slightly icky as we violate COW credentials a
 460          * bit */
 461         if (!(clone_flags & CLONE_THREAD)) {
 462                 tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
 463                 if (!tgcred) {
 464                         ret = -ENOMEM;
 465                         goto error_put;
 466                 }
 467                 atomic_set(&tgcred->usage, 1);
 468                 spin_lock_init(&tgcred->lock);
 469                 tgcred->process_keyring = NULL;
 470                 tgcred->session_keyring = key_get(new->tgcred->session_keyring);
 471
 472                 release_tgcred(new);
 473                 new->tgcred = tgcred;
 474         }
 475 #endif
 476
 477         atomic_inc(&new->user->processes);
 478         p->cred = p->real_cred = get_cred(new);
 479         alter_cred_subscribers(new, 2);
 480         validate_creds(new);
 481         return 0;
 482
 483 error_put:
 484         put_cred(new);
 485         return ret;
 486 }
 487
 488 /**
 489  * commit_creds - Install new credentials upon the current task
 490  * @new: The credentials to be assigned
 491  *
 492  * Install a new set of credentials to the current task, using RCU to replace
 493  * the old set.  Both the objective and the subjective credentials pointers are
 494  * updated.  This function may not be called if the subjective credentials are
 495  * in an overridden state.
 496  *
 497  * This function eats the caller's reference to the new credentials.
 498  *
 499  * Always returns 0 thus allowing this function to be tail-called at the end
 500  * of, say, sys_setgid().
 501  */
 502 int commit_creds(struct cred *new)
 503 {
 504         struct task_struct *task = current;
 505         const struct cred *old = task->real_cred;
 506
 507         kdebug("commit_creds(%p{%d,%d})", new,
 508                atomic_read(&new->usage),
 509                read_cred_subscribers(new));
 510
 511         BUG_ON(task->cred != old);
 512 #ifdef CONFIG_DEBUG_CREDENTIALS
 513         BUG_ON(read_cred_subscribers(old) < 2);
 514         validate_creds(old);
 515         validate_creds(new);
 516 #endif
 517         BUG_ON(atomic_read(&new->usage) < 1);
 518
 519         security_commit_creds(new, old);
 520
 521         get_cred(new); /* we will require a ref for the subj creds too */
 522
 523         /* dumpability changes */
 524         if (old->euid != new->euid ||
 525             old->egid != new->egid ||
 526             old->fsuid != new->fsuid ||
 527             old->fsgid != new->fsgid ||
 528             !cap_issubset(new->cap_permitted, old->cap_permitted)) {
 529                 if (task->mm)
 530                         set_dumpable(task->mm, suid_dumpable);
 531                 task->pdeath_signal = 0;
 532                 smp_wmb();
 533         }
 534
 535         /* alter the thread keyring */
 536         if (new->fsuid != old->fsuid)
 537                 key_fsuid_changed(task);
 538         if (new->fsgid != old->fsgid)
 539                 key_fsgid_changed(task);
 540
 541         /* do it
 542          * - What if a process setreuid()'s and this brings the
 543          *   new uid over his NPROC rlimit?  We can check this now
 544          *   cheaply with the new uid cache, so if it matters
 545          *   we should be checking for it.  -DaveM
 546          */
 547         alter_cred_subscribers(new, 2);
 548         if (new->user != old->user)
 549                 atomic_inc(&new->user->processes);
 550         rcu_assign_pointer(task->real_cred, new);
 551         rcu_assign_pointer(task->cred, new);
 552         if (new->user != old->user)
 553                 atomic_dec(&old->user->processes);
 554         alter_cred_subscribers(old, -2);
 555
 556         sched_switch_user(task);
 557
 558         /* send notifications */
 559         if (new->uid   != old->uid  ||
 560             new->euid  != old->euid ||
 561             new->suid  != old->suid ||
 562             new->fsuid != old->fsuid)
 563                 proc_id_connector(task, PROC_EVENT_UID);
 564
 565         if (new->gid   != old->gid  ||
 566             new->egid  != old->egid ||
 567             new->sgid  != old->sgid ||
 568             new->fsgid != old->fsgid)
 569                 proc_id_connector(task, PROC_EVENT_GID);
 570
 571         /* release the old obj and subj refs both */
 572         put_cred(old);
 573         put_cred(old);
 574         return 0;
 575 }
 576 EXPORT_SYMBOL(commit_creds);
 577
 578 /**
 579  * abort_creds - Discard a set of credentials and unlock the current task
 580  * @new: The credentials that were going to be applied
 581  *
 582  * Discard a set of credentials that were under construction and unlock the
 583  * current task.
 584  */
 585 void abort_creds(struct cred *new)
 586 {
 587         kdebug("abort_creds(%p{%d,%d})", new,
 588                atomic_read(&new->usage),
 589                read_cred_subscribers(new));
 590
 591 #ifdef CONFIG_DEBUG_CREDENTIALS
 592         BUG_ON(read_cred_subscribers(new) != 0);
 593 #endif
 594         BUG_ON(atomic_read(&new->usage) < 1);
 595         put_cred(new);
 596 }
 597 EXPORT_SYMBOL(abort_creds);
 598
 599 /**
 600  * override_creds - Override the current process's subjective credentials
 601  * @new: The credentials to be assigned
 602  *
 603  * Install a set of temporary override subjective credentials on the current
 604  * process, returning the old set for later reversion.
 605  */
 606 const struct cred *override_creds(const struct cred *new)
 607 {
 608         const struct cred *old = current->cred;
 609
 610         kdebug("override_creds(%p{%d,%d})", new,
 611                atomic_read(&new->usage),
 612                read_cred_subscribers(new));
 613
 614         validate_creds(old);
 615         validate_creds(new);
 616         get_cred(new);
 617         alter_cred_subscribers(new, 1);
 618         rcu_assign_pointer(current->cred, new);
 619         alter_cred_subscribers(old, -1);
 620
 621         kdebug("override_creds() = %p{%d,%d}", old,
 622                atomic_read(&old->usage),
 623                read_cred_subscribers(old));
 624         return old;
 625 }
 626 EXPORT_SYMBOL(override_creds);
 627
 628 /**
 629  * revert_creds - Revert a temporary subjective credentials override
 630  * @old: The credentials to be restored
 631  *
 632  * Revert a temporary set of override subjective credentials to an old set,
 633  * discarding the override set.
 634  */
 635 void revert_creds(const struct cred *old)
 636 {
 637         const struct cred *override = current->cred;
 638
 639         kdebug("revert_creds(%p{%d,%d})", old,
 640                atomic_read(&old->usage),
 641                read_cred_subscribers(old));
 642
 643         validate_creds(old);
 644         validate_creds(override);
 645         alter_cred_subscribers(old, 1);
 646         rcu_assign_pointer(current->cred, old);
 647         alter_cred_subscribers(override, -1);
 648         put_cred(override);
 649 }
 650 EXPORT_SYMBOL(revert_creds);
 651
 652 /*
 653  * initialise the credentials stuff
 654  */
 655 void __init cred_init(void)
 656 {
 657         /* allocate a slab in which we can store credentials */
 658         cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred),
 659                                      0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
 660 }
 661
 662 /**
 663  * prepare_kernel_cred - Prepare a set of credentials for a kernel service
 664  * @daemon: A userspace daemon to be used as a reference
 665  *
 666  * Prepare a set of credentials for a kernel service.  This can then be used to
 667  * override a task's own credentials so that work can be done on behalf of that
 668  * task that requires a different subjective context.
 669  *
 670  * @daemon is used to provide a base for the security record, but can be NULL.
 671  * If @daemon is supplied, then the security data will be derived from that;
 672  * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
 673  *
 674  * The caller may change these controls afterwards if desired.
 675  *
 676  * Returns the new credentials or NULL if out of memory.
 677  *
 678  * Does not take, and does not return holding current->cred_replace_mutex.
 679  */
 680 struct cred *prepare_kernel_cred(struct task_struct *daemon)
 681 {
 682         const struct cred *old;
 683         struct cred *new;
 684
 685         new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
 686         if (!new)
 687                 return NULL;
 688
 689         kdebug("prepare_kernel_cred() alloc %p", new);
 690
 691         if (daemon)
 692                 old = get_task_cred(daemon);
 693         else
 694                 old = get_cred(&init_cred);
 695
 696         validate_creds(old);
 697
 698         *new = *old;
 699         get_uid(new->user);
 700         get_group_info(new->group_info);
 701
 702 #ifdef CONFIG_KEYS
 703         atomic_inc(&init_tgcred.usage);
 704         new->tgcred = &init_tgcred;
 705         new->request_key_auth = NULL;
 706         new->thread_keyring = NULL;
 707         new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
 708 #endif
 709
 710 #ifdef CONFIG_SECURITY
 711         new->security = NULL;
 712 #endif
 713         if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
 714                 goto error;
 715
 716         atomic_set(&new->usage, 1);
 717         set_cred_subscribers(new, 0);
 718         put_cred(old);
 719         validate_creds(new);
 720         return new;
 721
 722 error:
 723         put_cred(new);
 724         put_cred(old);
 725         return NULL;
 726 }
 727 EXPORT_SYMBOL(prepare_kernel_cred);
 728
 729 /**
 730  * set_security_override - Set the security ID in a set of credentials
 731  * @new: The credentials to alter
 732  * @secid: The LSM security ID to set
 733  *
 734  * Set the LSM security ID in a set of credentials so that the subjective
 735  * security is overridden when an alternative set of credentials is used.
 736  */
 737 int set_security_override(struct cred *new, u32 secid)
 738 {
 739         return security_kernel_act_as(new, secid);
 740 }
 741 EXPORT_SYMBOL(set_security_override);
 742
 743 /**
 744  * set_security_override_from_ctx - Set the security ID in a set of credentials
 745  * @new: The credentials to alter
 746  * @secctx: The LSM security context to generate the security ID from.
 747  *
 748  * Set the LSM security ID in a set of credentials so that the subjective
 749  * security is overridden when an alternative set of credentials is used.  The
 750  * security ID is specified in string form as a security context to be
 751  * interpreted by the LSM.
 752  */
 753 int set_security_override_from_ctx(struct cred *new, const char *secctx)
 754 {
 755         u32 secid;
 756         int ret;
 757
 758         ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
 759         if (ret < 0)
 760                 return ret;
 761
 762         return set_security_override(new, secid);
 763 }
 764 EXPORT_SYMBOL(set_security_override_from_ctx);
 765
 766 /**
 767  * set_create_files_as - Set the LSM file create context in a set of credentials
 768  * @new: The credentials to alter
 769  * @inode: The inode to take the context from
 770  *
 771  * Change the LSM file creation context in a set of credentials to be the same
 772  * as the object context of the specified inode, so that the new inodes have
 773  * the same MAC context as that inode.
 774  */
 775 int set_create_files_as(struct cred *new, struct inode *inode)
 776 {
 777         new->fsuid = inode->i_uid;
 778         new->fsgid = inode->i_gid;
 779         return security_kernel_create_files_as(new, inode);
 780 }
 781 EXPORT_SYMBOL(set_create_files_as);
 782
 783 #ifdef CONFIG_DEBUG_CREDENTIALS
 784
 785 bool creds_are_invalid(const struct cred *cred)
 786 {
 787         if (cred->magic != CRED_MAGIC)
 788                 return true;
 789         if (atomic_read(&cred->usage) < atomic_read(&cred->subscribers))
 790                 return true;
 791 #ifdef CONFIG_SECURITY_SELINUX
 792         if (selinux_is_enabled()) {
 793                 if ((unsigned long) cred->security < PAGE_SIZE)
 794                         return true;
 795                 if ((*(u32 *)cred->security & 0xffffff00) ==
 796                     (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
 797                         return true;
 798         }
 799 #endif
 800         return false;
 801 }
 802 EXPORT_SYMBOL(creds_are_invalid);
 803
 804 /*
 805  * dump invalid credentials
 806  */
 807 static void dump_invalid_creds(const struct cred *cred, const char *label,
 808                                const struct task_struct *tsk)
 809 {
 810         printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
 811                label, cred,
 812                cred == &init_cred ? "[init]" : "",
 813                cred == tsk->real_cred ? "[real]" : "",
 814                cred == tsk->cred ? "[eff]" : "");
 815         printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
 816                cred->magic, cred->put_addr);
 817         printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
 818                atomic_read(&cred->usage),
 819                read_cred_subscribers(cred));
 820         printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
 821                cred->uid, cred->euid, cred->suid, cred->fsuid);
 822         printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
 823                cred->gid, cred->egid, cred->sgid, cred->fsgid);
 824 #ifdef CONFIG_SECURITY
 825         printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
 826         if ((unsigned long) cred->security >= PAGE_SIZE &&
 827             (((unsigned long) cred->security & 0xffffff00) !=
 828              (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
 829                 printk(KERN_ERR "CRED: ->security {%x, %x}\n",
 830                        ((u32*)cred->security)[0],
 831                        ((u32*)cred->security)[1]);
 832 #endif
 833 }
 834
 835 /*
 836  * report use of invalid credentials
 837  */
 838 void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
 839 {
 840         printk(KERN_ERR "CRED: Invalid credentials\n");
 841         printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 842         dump_invalid_creds(cred, "Specified", current);
 843         BUG();
 844 }
 845 EXPORT_SYMBOL(__invalid_creds);
 846
 847 /*
 848  * check the credentials on a process
 849  */
 850 void __validate_process_creds(struct task_struct *tsk,
 851                               const char *file, unsigned line)
 852 {
 853         if (tsk->cred == tsk->real_cred) {
 854                 if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
 855                              creds_are_invalid(tsk->cred)))
 856                         goto invalid_creds;
 857         } else {
 858                 if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
 859                              read_cred_subscribers(tsk->cred) < 1 ||
 860                              creds_are_invalid(tsk->real_cred) ||
 861                              creds_are_invalid(tsk->cred)))
 862                         goto invalid_creds;
 863         }
 864         return;
 865
 866 invalid_creds:
 867         printk(KERN_ERR "CRED: Invalid process credentials\n");
 868         printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 869
 870         dump_invalid_creds(tsk->real_cred, "Real", tsk);
 871         if (tsk->cred != tsk->real_cred)
 872                 dump_invalid_creds(tsk->cred, "Effective", tsk);
 873         else
 874                 printk(KERN_ERR "CRED: Effective creds == Real creds\n");
 875         BUG();
 876 }
 877 EXPORT_SYMBOL(__validate_process_creds);
 878
 879 /*
 880  * check creds for do_exit()
 881  */
 882 void validate_creds_for_do_exit(struct task_struct *tsk)
 883 {
 884         kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
 885                tsk->real_cred, tsk->cred,
 886                atomic_read(&tsk->cred->usage),
 887                read_cred_subscribers(tsk->cred));
 888
 889         __validate_process_creds(tsk, __FILE__, __LINE__);
 890 }
 891
 892 #endif /* CONFIG_DEBUG_CREDENTIALS */