kernel/cred.c

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