kernel/cred.c

   1 /* Task credentials management - see Documentation/credentials.txt
   2  *
   3  * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public Licence
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the Licence, or (at your option) any later version.
  10  */
  11 #include <linux/module.h>
  12 #include <linux/cred.h>
  13 #include <linux/slab.h>
  14 #include <linux/sched.h>
  15 #include <linux/key.h>
  16 #include <linux/keyctl.h>
  17 #include <linux/init_task.h>
  18 #include <linux/security.h>
  19 #include <linux/cn_proc.h>
  20 #include "cred-internals.h"
  21
  22 #if 0
  23 #define kdebug(FMT, ...) \
  24         printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
  25 #else
  26 static inline __attribute__((format(printf, 1, 2)))
  27 void no_printk(const char *fmt, ...)
  28 {
  29 }
  30 #define kdebug(FMT, ...) \
  31         no_printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
  32 #endif
  33
  34 static struct kmem_cache *cred_jar;
  35
  36 /*
  37  * The common credentials for the initial task's thread group
  38  */
  39 #ifdef CONFIG_KEYS
  40 static struct thread_group_cred init_tgcred = {
  41         .usage  = ATOMIC_INIT(2),
  42         .tgid   = 0,
  43         .lock   = SPIN_LOCK_UNLOCKED,
  44 };
  45 #endif
  46
  47 /*
  48  * The initial credentials for the initial task
  49  */
  50 struct cred init_cred = {
  51         .usage                  = ATOMIC_INIT(4),
  52 #ifdef CONFIG_DEBUG_CREDENTIALS
  53         .subscribers            = ATOMIC_INIT(2),
  54         .magic                  = CRED_MAGIC,
  55 #endif
  56         .securebits             = SECUREBITS_DEFAULT,
  57         .cap_inheritable        = CAP_INIT_INH_SET,
  58         .cap_permitted          = CAP_FULL_SET,
  59         .cap_effective          = CAP_INIT_EFF_SET,
  60         .cap_bset               = CAP_INIT_BSET,
  61         .user                   = INIT_USER,
  62         .group_info             = &init_groups,
  63 #ifdef CONFIG_KEYS
  64         .tgcred                 = &init_tgcred,
  65 #endif
  66 };
  67
  68 static inline void set_cred_subscribers(struct cred *cred, int n)
  69 {
  70 #ifdef CONFIG_DEBUG_CREDENTIALS
  71         atomic_set(&cred->subscribers, n);
  72 #endif
  73 }
  74
  75 static inline int read_cred_subscribers(const struct cred *cred)
  76 {
  77 #ifdef CONFIG_DEBUG_CREDENTIALS
  78         return atomic_read(&cred->subscribers);
  79 #else
  80         return 0;
  81 #endif
  82 }
  83
  84 static inline void alter_cred_subscribers(const struct cred *_cred, int n)
  85 {
  86 #ifdef CONFIG_DEBUG_CREDENTIALS
  87         struct cred *cred = (struct cred *) _cred;
  88
  89         atomic_add(n, &cred->subscribers);
  90 #endif
  91 }
  92
  93 /*
  94  * Dispose of the shared task group credentials
  95  */
  96 #ifdef CONFIG_KEYS
  97 static void release_tgcred_rcu(struct rcu_head *rcu)
  98 {
  99         struct thread_group_cred *tgcred =
 100                 container_of(rcu, struct thread_group_cred, rcu);
 101
 102         BUG_ON(atomic_read(&tgcred->usage) != 0);
 103
 104         key_put(tgcred->session_keyring);
 105         key_put(tgcred->process_keyring);
 106         kfree(tgcred);
 107 }
 108 #endif
 109
 110 /*
 111  * Release a set of thread group credentials.
 112  */
 113 static void release_tgcred(struct cred *cred)
 114 {
 115 #ifdef CONFIG_KEYS
 116         struct thread_group_cred *tgcred = cred->tgcred;
 117
 118         if (atomic_dec_and_test(&tgcred->usage))
 119                 call_rcu(&tgcred->rcu, release_tgcred_rcu);
 120 #endif
 121 }
 122
 123 /*
 124  * The RCU callback to actually dispose of a set of credentials
 125  */
 126 static void put_cred_rcu(struct rcu_head *rcu)
 127 {
 128         struct cred *cred = container_of(rcu, struct cred, rcu);
 129
 130         kdebug("put_cred_rcu(%p)", cred);
 131
 132 #ifdef CONFIG_DEBUG_CREDENTIALS
 133         if (cred->magic != CRED_MAGIC_DEAD ||
 134             atomic_read(&cred->usage) != 0 ||
 135             read_cred_subscribers(cred) != 0)
 136                 panic("CRED: put_cred_rcu() sees %p with"
 137                       " mag %x, put %p, usage %d, subscr %d\n",
 138                       cred, cred->magic, cred->put_addr,
 139                       atomic_read(&cred->usage),
 140                       read_cred_subscribers(cred));
 141 #else
 142         if (atomic_read(&cred->usage) != 0)
 143                 panic("CRED: put_cred_rcu() sees %p with usage %d\n",
 144                       cred, atomic_read(&cred->usage));
 145 #endif
 146
 147         security_cred_free(cred);
 148         key_put(cred->thread_keyring);
 149         key_put(cred->request_key_auth);
 150         release_tgcred(cred);
 151         if (cred->group_info)
 152                 put_group_info(cred->group_info);
 153         free_uid(cred->user);
 154         kmem_cache_free(cred_jar, cred);
 155 }
 156
 157 /**
 158  * __put_cred - Destroy a set of credentials
 159  * @cred: The record to release
 160  *
 161  * Destroy a set of credentials on which no references remain.
 162  */
 163 void __put_cred(struct cred *cred)
 164 {
 165         kdebug("__put_cred(%p{%d,%d})", cred,
 166                atomic_read(&cred->usage),
 167                read_cred_subscribers(cred));
 168
 169         BUG_ON(atomic_read(&cred->usage) != 0);
 170 #ifdef CONFIG_DEBUG_CREDENTIALS
 171         BUG_ON(read_cred_subscribers(cred) != 0);
 172         cred->magic = CRED_MAGIC_DEAD;
 173         cred->put_addr = __builtin_return_address(0);
 174 #endif
 175         BUG_ON(cred == current->cred);
 176         BUG_ON(cred == current->real_cred);
 177
 178         call_rcu(&cred->rcu, put_cred_rcu);
 179 }
 180 EXPORT_SYMBOL(__put_cred);
 181
 182 /*
 183  * Clean up a task's credentials when it exits
 184  */
 185 void exit_creds(struct task_struct *tsk)
 186 {
 187         struct cred *cred;
 188
 189         kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
 190                atomic_read(&tsk->cred->usage),
 191                read_cred_subscribers(tsk->cred));
 192
 193         cred = (struct cred *) tsk->real_cred;
 194         tsk->real_cred = NULL;
 195         validate_creds(cred);
 196         alter_cred_subscribers(cred, -1);
 197         put_cred(cred);
 198
 199         cred = (struct cred *) tsk->cred;
 200         tsk->cred = NULL;
 201         validate_creds(cred);
 202         alter_cred_subscribers(cred, -1);
 203         put_cred(cred);
 204
 205         cred = (struct cred *) tsk->replacement_session_keyring;
 206         if (cred) {
 207                 tsk->replacement_session_keyring = NULL;
 208                 validate_creds(cred);
 209                 put_cred(cred);
 210         }
 211 }
 212
 213 /*
 214  * Allocate blank credentials, such that the credentials can be filled in at a
 215  * later date without risk of ENOMEM.
 216  */
 217 struct cred *cred_alloc_blank(void)
 218 {
 219         struct cred *new;
 220
 221         new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
 222         if (!new)
 223                 return NULL;
 224
 225 #ifdef CONFIG_KEYS
 226         new->tgcred = kzalloc(sizeof(*new->tgcred), GFP_KERNEL);
 227         if (!new->tgcred) {
 228                 kmem_cache_free(cred_jar, new);
 229                 return NULL;
 230         }
 231         atomic_set(&new->tgcred->usage, 1);
 232 #endif
 233
 234         atomic_set(&new->usage, 1);
 235
 236         if (security_cred_alloc_blank(new, GFP_KERNEL) < 0)
 237                 goto error;
 238
 239 #ifdef CONFIG_DEBUG_CREDENTIALS
 240         new->magic = CRED_MAGIC;
 241 #endif
 242         return new;
 243
 244 error:
 245         abort_creds(new);
 246         return NULL;
 247 }
 248
 249 /**
 250  * prepare_creds - Prepare a new set of credentials for modification
 251  *
 252  * Prepare a new set of task credentials for modification.  A task's creds
 253  * shouldn't generally be modified directly, therefore this function is used to
 254  * prepare a new copy, which the caller then modifies and then commits by
 255  * calling commit_creds().
 256  *
 257  * Preparation involves making a copy of the objective creds for modification.
 258  *
 259  * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
 260  *
 261  * Call commit_creds() or abort_creds() to clean up.
 262  */
 263 struct cred *prepare_creds(void)
 264 {
 265         struct task_struct *task = current;
 266         const struct cred *old;
 267         struct cred *new;
 268
 269         validate_process_creds();
 270
 271         new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
 272         if (!new)
 273                 return NULL;
 274
 275         kdebug("prepare_creds() alloc %p", new);
 276
 277         old = task->cred;
 278         memcpy(new, old, sizeof(struct cred));
 279
 280         atomic_set(&new->usage, 1);
 281         set_cred_subscribers(new, 0);
 282         get_group_info(new->group_info);
 283         get_uid(new->user);
 284
 285 #ifdef CONFIG_KEYS
 286         key_get(new->thread_keyring);
 287         key_get(new->request_key_auth);
 288         atomic_inc(&new->tgcred->usage);
 289 #endif
 290
 291 #ifdef CONFIG_SECURITY
 292         new->security = NULL;
 293 #endif
 294
 295         if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
 296                 goto error;
 297         validate_creds(new);
 298         return new;
 299
 300 error:
 301         abort_creds(new);
 302         return NULL;
 303 }
 304 EXPORT_SYMBOL(prepare_creds);
 305
 306 /*
 307  * Prepare credentials for current to perform an execve()
 308  * - The caller must hold current->cred_guard_mutex
 309  */
 310 struct cred *prepare_exec_creds(void)
 311 {
 312         struct thread_group_cred *tgcred = NULL;
 313         struct cred *new;
 314
 315 #ifdef CONFIG_KEYS
 316         tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
 317         if (!tgcred)
 318                 return NULL;
 319 #endif
 320
 321         new = prepare_creds();
 322         if (!new) {
 323                 kfree(tgcred);
 324                 return new;
 325         }
 326
 327 #ifdef CONFIG_KEYS
 328         /* newly exec'd tasks don't get a thread keyring */
 329         key_put(new->thread_keyring);
 330         new->thread_keyring = NULL;
 331
 332         /* create a new per-thread-group creds for all this set of threads to
 333          * share */
 334         memcpy(tgcred, new->tgcred, sizeof(struct thread_group_cred));
 335
 336         atomic_set(&tgcred->usage, 1);
 337         spin_lock_init(&tgcred->lock);
 338
 339         /* inherit the session keyring; new process keyring */
 340         key_get(tgcred->session_keyring);
 341         tgcred->process_keyring = NULL;
 342
 343         release_tgcred(new);
 344         new->tgcred = tgcred;
 345 #endif
 346
 347         return new;
 348 }
 349
 350 /*
 351  * prepare new credentials for the usermode helper dispatcher
 352  */
 353 struct cred *prepare_usermodehelper_creds(void)
 354 {
 355 #ifdef CONFIG_KEYS
 356         struct thread_group_cred *tgcred = NULL;
 357 #endif
 358         struct cred *new;
 359
 360 #ifdef CONFIG_KEYS
 361         tgcred = kzalloc(sizeof(*new->tgcred), GFP_ATOMIC);
 362         if (!tgcred)
 363                 return NULL;
 364 #endif
 365
 366         new = kmem_cache_alloc(cred_jar, GFP_ATOMIC);
 367         if (!new)
 368                 goto free_tgcred;
 369
 370         kdebug("prepare_usermodehelper_creds() alloc %p", new);
 371
 372         memcpy(new, &init_cred, sizeof(struct cred));
 373
 374         atomic_set(&new->usage, 1);
 375         set_cred_subscribers(new, 0);
 376         get_group_info(new->group_info);
 377         get_uid(new->user);
 378
 379 #ifdef CONFIG_KEYS
 380         new->thread_keyring = NULL;
 381         new->request_key_auth = NULL;
 382         new->jit_keyring = KEY_REQKEY_DEFL_DEFAULT;
 383
 384         atomic_set(&tgcred->usage, 1);
 385         spin_lock_init(&tgcred->lock);
 386         new->tgcred = tgcred;
 387 #endif
 388
 389 #ifdef CONFIG_SECURITY
 390         new->security = NULL;
 391 #endif
 392         if (security_prepare_creds(new, &init_cred, GFP_ATOMIC) < 0)
 393                 goto error;
 394         validate_creds(new);
 395
 396         BUG_ON(atomic_read(&new->usage) != 1);
 397         return new;
 398
 399 error:
 400         put_cred(new);
 401         return NULL;
 402
 403 free_tgcred:
 404 #ifdef CONFIG_KEYS
 405         kfree(tgcred);
 406 #endif
 407         return NULL;
 408 }
 409
 410 /*
 411  * Copy credentials for the new process created by fork()
 412  *
 413  * We share if we can, but under some circumstances we have to generate a new
 414  * set.
 415  *
 416  * The new process gets the current process's subjective credentials as its
 417  * objective and subjective credentials
 418  */
 419 int copy_creds(struct task_struct *p, unsigned long clone_flags)
 420 {
 421 #ifdef CONFIG_KEYS
 422         struct thread_group_cred *tgcred;
 423 #endif
 424         struct cred *new;
 425         int ret;
 426
 427         mutex_init(&p->cred_guard_mutex);
 428
 429         if (
 430 #ifdef CONFIG_KEYS
 431                 !p->cred->thread_keyring &&
 432 #endif
 433                 clone_flags & CLONE_THREAD
 434             ) {
 435                 p->real_cred = get_cred(p->cred);
 436                 get_cred(p->cred);
 437                 alter_cred_subscribers(p->cred, 2);
 438                 kdebug("share_creds(%p{%d,%d})",
 439                        p->cred, atomic_read(&p->cred->usage),
 440                        read_cred_subscribers(p->cred));
 441                 atomic_inc(&p->cred->user->processes);
 442                 return 0;
 443         }
 444
 445         new = prepare_creds();
 446         if (!new)
 447                 return -ENOMEM;
 448
 449         if (clone_flags & CLONE_NEWUSER) {
 450                 ret = create_user_ns(new);
 451                 if (ret < 0)
 452                         goto error_put;
 453         }
 454
 455 #ifdef CONFIG_KEYS
 456         /* new threads get their own thread keyrings if their parent already
 457          * had one */
 458         if (new->thread_keyring) {
 459                 key_put(new->thread_keyring);
 460                 new->thread_keyring = NULL;
 461                 if (clone_flags & CLONE_THREAD)
 462                         install_thread_keyring_to_cred(new);
 463         }
 464
 465         /* we share the process and session keyrings between all the threads in
 466          * a process - this is slightly icky as we violate COW credentials a
 467          * bit */
 468         if (!(clone_flags & CLONE_THREAD)) {
 469                 tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
 470                 if (!tgcred) {
 471                         ret = -ENOMEM;
 472                         goto error_put;
 473                 }
 474                 atomic_set(&tgcred->usage, 1);
 475                 spin_lock_init(&tgcred->lock);
 476                 tgcred->process_keyring = NULL;
 477                 tgcred->session_keyring = key_get(new->tgcred->session_keyring);
 478
 479                 release_tgcred(new);
 480                 new->tgcred = tgcred;
 481         }
 482 #endif
 483
 484         atomic_inc(&new->user->processes);
 485         p->cred = p->real_cred = get_cred(new);
 486         alter_cred_subscribers(new, 2);
 487         validate_creds(new);
 488         return 0;
 489
 490 error_put:
 491         put_cred(new);
 492         return ret;
 493 }
 494
 495 /**
 496  * commit_creds - Install new credentials upon the current task
 497  * @new: The credentials to be assigned
 498  *
 499  * Install a new set of credentials to the current task, using RCU to replace
 500  * the old set.  Both the objective and the subjective credentials pointers are
 501  * updated.  This function may not be called if the subjective credentials are
 502  * in an overridden state.
 503  *
 504  * This function eats the caller's reference to the new credentials.
 505  *
 506  * Always returns 0 thus allowing this function to be tail-called at the end
 507  * of, say, sys_setgid().
 508  */
 509 int commit_creds(struct cred *new)
 510 {
 511         struct task_struct *task = current;
 512         const struct cred *old = task->real_cred;
 513
 514         kdebug("commit_creds(%p{%d,%d})", new,
 515                atomic_read(&new->usage),
 516                read_cred_subscribers(new));
 517
 518         BUG_ON(task->cred != old);
 519 #ifdef CONFIG_DEBUG_CREDENTIALS
 520         BUG_ON(read_cred_subscribers(old) < 2);
 521         validate_creds(old);
 522         validate_creds(new);
 523 #endif
 524         BUG_ON(atomic_read(&new->usage) < 1);
 525
 526         security_commit_creds(new, old);
 527
 528         get_cred(new); /* we will require a ref for the subj creds too */
 529
 530         /* dumpability changes */
 531         if (old->euid != new->euid ||
 532             old->egid != new->egid ||
 533             old->fsuid != new->fsuid ||
 534             old->fsgid != new->fsgid ||
 535             !cap_issubset(new->cap_permitted, old->cap_permitted)) {
 536                 if (task->mm)
 537                         set_dumpable(task->mm, suid_dumpable);
 538                 task->pdeath_signal = 0;
 539                 smp_wmb();
 540         }
 541
 542         /* alter the thread keyring */
 543         if (new->fsuid != old->fsuid)
 544                 key_fsuid_changed(task);
 545         if (new->fsgid != old->fsgid)
 546                 key_fsgid_changed(task);
 547
 548         /* do it
 549          * - What if a process setreuid()'s and this brings the
 550          *   new uid over his NPROC rlimit?  We can check this now
 551          *   cheaply with the new uid cache, so if it matters
 552          *   we should be checking for it.  -DaveM
 553          */
 554         alter_cred_subscribers(new, 2);
 555         if (new->user != old->user)
 556                 atomic_inc(&new->user->processes);
 557         rcu_assign_pointer(task->real_cred, new);
 558         rcu_assign_pointer(task->cred, new);
 559         if (new->user != old->user)
 560                 atomic_dec(&old->user->processes);
 561         alter_cred_subscribers(old, -2);
 562
 563         sched_switch_user(task);
 564
 565         /* send notifications */
 566         if (new->uid   != old->uid  ||
 567             new->euid  != old->euid ||
 568             new->suid  != old->suid ||
 569             new->fsuid != old->fsuid)
 570                 proc_id_connector(task, PROC_EVENT_UID);
 571
 572         if (new->gid   != old->gid  ||
 573             new->egid  != old->egid ||
 574             new->sgid  != old->sgid ||
 575             new->fsgid != old->fsgid)
 576                 proc_id_connector(task, PROC_EVENT_GID);
 577
 578         /* release the old obj and subj refs both */
 579         put_cred(old);
 580         put_cred(old);
 581         return 0;
 582 }
 583 EXPORT_SYMBOL(commit_creds);
 584
 585 /**
 586  * abort_creds - Discard a set of credentials and unlock the current task
 587  * @new: The credentials that were going to be applied
 588  *
 589  * Discard a set of credentials that were under construction and unlock the
 590  * current task.
 591  */
 592 void abort_creds(struct cred *new)
 593 {
 594         kdebug("abort_creds(%p{%d,%d})", new,
 595                atomic_read(&new->usage),
 596                read_cred_subscribers(new));
 597
 598 #ifdef CONFIG_DEBUG_CREDENTIALS
 599         BUG_ON(read_cred_subscribers(new) != 0);
 600 #endif
 601         BUG_ON(atomic_read(&new->usage) < 1);
 602         put_cred(new);
 603 }
 604 EXPORT_SYMBOL(abort_creds);
 605
 606 /**
 607  * override_creds - Override the current process's subjective credentials
 608  * @new: The credentials to be assigned
 609  *
 610  * Install a set of temporary override subjective credentials on the current
 611  * process, returning the old set for later reversion.
 612  */
 613 const struct cred *override_creds(const struct cred *new)
 614 {
 615         const struct cred *old = current->cred;
 616
 617         kdebug("override_creds(%p{%d,%d})", new,
 618                atomic_read(&new->usage),
 619                read_cred_subscribers(new));
 620
 621         validate_creds(old);
 622         validate_creds(new);
 623         get_cred(new);
 624         alter_cred_subscribers(new, 1);
 625         rcu_assign_pointer(current->cred, new);
 626         alter_cred_subscribers(old, -1);
 627
 628         kdebug("override_creds() = %p{%d,%d}", old,
 629                atomic_read(&old->usage),
 630                read_cred_subscribers(old));
 631         return old;
 632 }
 633 EXPORT_SYMBOL(override_creds);
 634
 635 /**
 636  * revert_creds - Revert a temporary subjective credentials override
 637  * @old: The credentials to be restored
 638  *
 639  * Revert a temporary set of override subjective credentials to an old set,
 640  * discarding the override set.
 641  */
 642 void revert_creds(const struct cred *old)
 643 {
 644         const struct cred *override = current->cred;
 645
 646         kdebug("revert_creds(%p{%d,%d})", old,
 647                atomic_read(&old->usage),
 648                read_cred_subscribers(old));
 649
 650         validate_creds(old);
 651         validate_creds(override);
 652         alter_cred_subscribers(old, 1);
 653         rcu_assign_pointer(current->cred, old);
 654         alter_cred_subscribers(override, -1);
 655         put_cred(override);
 656 }
 657 EXPORT_SYMBOL(revert_creds);
 658
 659 /*
 660  * initialise the credentials stuff
 661  */
 662 void __init cred_init(void)
 663 {
 664         /* allocate a slab in which we can store credentials */
 665         cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred),
 666                                      0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
 667 }
 668
 669 /**
 670  * prepare_kernel_cred - Prepare a set of credentials for a kernel service
 671  * @daemon: A userspace daemon to be used as a reference
 672  *
 673  * Prepare a set of credentials for a kernel service.  This can then be used to
 674  * override a task's own credentials so that work can be done on behalf of that
 675  * task that requires a different subjective context.
 676  *
 677  * @daemon is used to provide a base for the security record, but can be NULL.
 678  * If @daemon is supplied, then the security data will be derived from that;
 679  * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
 680  *
 681  * The caller may change these controls afterwards if desired.
 682  *
 683  * Returns the new credentials or NULL if out of memory.
 684  *
 685  * Does not take, and does not return holding current->cred_replace_mutex.
 686  */
 687 struct cred *prepare_kernel_cred(struct task_struct *daemon)
 688 {
 689         const struct cred *old;
 690         struct cred *new;
 691
 692         new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
 693         if (!new)
 694                 return NULL;
 695
 696         kdebug("prepare_kernel_cred() alloc %p", new);
 697
 698         if (daemon)
 699                 old = get_task_cred(daemon);
 700         else
 701                 old = get_cred(&init_cred);
 702
 703         validate_creds(old);
 704
 705         *new = *old;
 706         get_uid(new->user);
 707         get_group_info(new->group_info);
 708
 709 #ifdef CONFIG_KEYS
 710         atomic_inc(&init_tgcred.usage);
 711         new->tgcred = &init_tgcred;
 712         new->request_key_auth = NULL;
 713         new->thread_keyring = NULL;
 714         new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
 715 #endif
 716
 717 #ifdef CONFIG_SECURITY
 718         new->security = NULL;
 719 #endif
 720         if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
 721                 goto error;
 722
 723         atomic_set(&new->usage, 1);
 724         set_cred_subscribers(new, 0);
 725         put_cred(old);
 726         validate_creds(new);
 727         return new;
 728
 729 error:
 730         put_cred(new);
 731         put_cred(old);
 732         return NULL;
 733 }
 734 EXPORT_SYMBOL(prepare_kernel_cred);
 735
 736 /**
 737  * set_security_override - Set the security ID in a set of credentials
 738  * @new: The credentials to alter
 739  * @secid: The LSM security ID to set
 740  *
 741  * Set the LSM security ID in a set of credentials so that the subjective
 742  * security is overridden when an alternative set of credentials is used.
 743  */
 744 int set_security_override(struct cred *new, u32 secid)
 745 {
 746         return security_kernel_act_as(new, secid);
 747 }
 748 EXPORT_SYMBOL(set_security_override);
 749
 750 /**
 751  * set_security_override_from_ctx - Set the security ID in a set of credentials
 752  * @new: The credentials to alter
 753  * @secctx: The LSM security context to generate the security ID from.
 754  *
 755  * Set the LSM security ID in a set of credentials so that the subjective
 756  * security is overridden when an alternative set of credentials is used.  The
 757  * security ID is specified in string form as a security context to be
 758  * interpreted by the LSM.
 759  */
 760 int set_security_override_from_ctx(struct cred *new, const char *secctx)
 761 {
 762         u32 secid;
 763         int ret;
 764
 765         ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
 766         if (ret < 0)
 767                 return ret;
 768
 769         return set_security_override(new, secid);
 770 }
 771 EXPORT_SYMBOL(set_security_override_from_ctx);
 772
 773 /**
 774  * set_create_files_as - Set the LSM file create context in a set of credentials
 775  * @new: The credentials to alter
 776  * @inode: The inode to take the context from
 777  *
 778  * Change the LSM file creation context in a set of credentials to be the same
 779  * as the object context of the specified inode, so that the new inodes have
 780  * the same MAC context as that inode.
 781  */
 782 int set_create_files_as(struct cred *new, struct inode *inode)
 783 {
 784         new->fsuid = inode->i_uid;
 785         new->fsgid = inode->i_gid;
 786         return security_kernel_create_files_as(new, inode);
 787 }
 788 EXPORT_SYMBOL(set_create_files_as);
 789
 790 #ifdef CONFIG_DEBUG_CREDENTIALS
 791
 792 bool creds_are_invalid(const struct cred *cred)
 793 {
 794         if (cred->magic != CRED_MAGIC)
 795                 return true;
 796 #ifdef CONFIG_SECURITY_SELINUX
 797         if (selinux_is_enabled()) {
 798                 if ((unsigned long) cred->security < PAGE_SIZE)
 799                         return true;
 800                 if ((*(u32 *)cred->security & 0xffffff00) ==
 801                     (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
 802                         return true;
 803         }
 804 #endif
 805         return false;
 806 }
 807 EXPORT_SYMBOL(creds_are_invalid);
 808
 809 /*
 810  * dump invalid credentials
 811  */
 812 static void dump_invalid_creds(const struct cred *cred, const char *label,
 813                                const struct task_struct *tsk)
 814 {
 815         printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
 816                label, cred,
 817                cred == &init_cred ? "[init]" : "",
 818                cred == tsk->real_cred ? "[real]" : "",
 819                cred == tsk->cred ? "[eff]" : "");
 820         printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
 821                cred->magic, cred->put_addr);
 822         printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
 823                atomic_read(&cred->usage),
 824                read_cred_subscribers(cred));
 825         printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
 826                cred->uid, cred->euid, cred->suid, cred->fsuid);
 827         printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
 828                cred->gid, cred->egid, cred->sgid, cred->fsgid);
 829 #ifdef CONFIG_SECURITY
 830         printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
 831         if ((unsigned long) cred->security >= PAGE_SIZE &&
 832             (((unsigned long) cred->security & 0xffffff00) !=
 833              (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
 834                 printk(KERN_ERR "CRED: ->security {%x, %x}\n",
 835                        ((u32*)cred->security)[0],
 836                        ((u32*)cred->security)[1]);
 837 #endif
 838 }
 839
 840 /*
 841  * report use of invalid credentials
 842  */
 843 void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
 844 {
 845         printk(KERN_ERR "CRED: Invalid credentials\n");
 846         printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 847         dump_invalid_creds(cred, "Specified", current);
 848         BUG();
 849 }
 850 EXPORT_SYMBOL(__invalid_creds);
 851
 852 /*
 853  * check the credentials on a process
 854  */
 855 void __validate_process_creds(struct task_struct *tsk,
 856                               const char *file, unsigned line)
 857 {
 858         if (tsk->cred == tsk->real_cred) {
 859                 if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
 860                              creds_are_invalid(tsk->cred)))
 861                         goto invalid_creds;
 862         } else {
 863                 if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
 864                              read_cred_subscribers(tsk->cred) < 1 ||
 865                              creds_are_invalid(tsk->real_cred) ||
 866                              creds_are_invalid(tsk->cred)))
 867                         goto invalid_creds;
 868         }
 869         return;
 870
 871 invalid_creds:
 872         printk(KERN_ERR "CRED: Invalid process credentials\n");
 873         printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 874
 875         dump_invalid_creds(tsk->real_cred, "Real", tsk);
 876         if (tsk->cred != tsk->real_cred)
 877                 dump_invalid_creds(tsk->cred, "Effective", tsk);
 878         else
 879                 printk(KERN_ERR "CRED: Effective creds == Real creds\n");
 880         BUG();
 881 }
 882 EXPORT_SYMBOL(__validate_process_creds);
 883
 884 /*
 885  * check creds for do_exit()
 886  */
 887 void validate_creds_for_do_exit(struct task_struct *tsk)
 888 {
 889         kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
 890                tsk->real_cred, tsk->cred,
 891                atomic_read(&tsk->cred->usage),
 892                read_cred_subscribers(tsk->cred));
 893
 894         __validate_process_creds(tsk, __FILE__, __LINE__);
 895 }
 896
 897 #endif /* CONFIG_DEBUG_CREDENTIALS */