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