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/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
  21 #if 0
  22 #define kdebug(FMT, ...) \
  23         printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
  24 #else
  25 #define kdebug(FMT, ...) \
  26         no_printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
  27 #endif
  28
  29 static struct kmem_cache *cred_jar;
  30
  31 /*
  32  * The common credentials for the initial task's thread group
  33  */
  34 #ifdef CONFIG_KEYS
  35 static struct thread_group_cred init_tgcred = {
  36         .usage  = ATOMIC_INIT(2),
  37         .tgid   = 0,
  38         .lock   = __SPIN_LOCK_UNLOCKED(init_cred.tgcred.lock),
  39 };
  40 #endif
  41
  42 /*
  43  * The initial credentials for the initial task
  44  */
  45 struct cred init_cred = {
  46         .usage                  = ATOMIC_INIT(4),
  47 #ifdef CONFIG_DEBUG_CREDENTIALS
  48         .subscribers            = ATOMIC_INIT(2),
  49         .magic                  = CRED_MAGIC,
  50 #endif
  51         .securebits             = SECUREBITS_DEFAULT,
  52         .cap_inheritable        = CAP_EMPTY_SET,
  53         .cap_permitted          = CAP_FULL_SET,
  54         .cap_effective          = CAP_FULL_SET,
  55         .cap_bset               = CAP_FULL_SET,
  56         .user                   = INIT_USER,
  57         .user_ns                = &init_user_ns,
  58         .group_info             = &init_groups,
  59 #ifdef CONFIG_KEYS
  60         .tgcred                 = &init_tgcred,
  61 #endif
  62 };
  63
  64 static inline void set_cred_subscribers(struct cred *cred, int n)
  65 {
  66 #ifdef CONFIG_DEBUG_CREDENTIALS
  67         atomic_set(&cred->subscribers, n);
  68 #endif
  69 }
  70
  71 static inline int read_cred_subscribers(const struct cred *cred)
  72 {
  73 #ifdef CONFIG_DEBUG_CREDENTIALS
  74         return atomic_read(&cred->subscribers);
  75 #else
  76         return 0;
  77 #endif
  78 }
  79
  80 static inline void alter_cred_subscribers(const struct cred *_cred, int n)
  81 {
  82 #ifdef CONFIG_DEBUG_CREDENTIALS
  83         struct cred *cred = (struct cred *) _cred;
  84
  85         atomic_add(n, &cred->subscribers);
  86 #endif
  87 }
  88
  89 /*
  90  * Dispose of the shared task group credentials
  91  */
  92 #ifdef CONFIG_KEYS
  93 static void release_tgcred_rcu(struct rcu_head *rcu)
  94 {
  95         struct thread_group_cred *tgcred =
  96                 container_of(rcu, struct thread_group_cred, rcu);
  97
  98         BUG_ON(atomic_read(&tgcred->usage) != 0);
  99
 100         key_put(tgcred->session_keyring);
 101         key_put(tgcred->process_keyring);
 102         kfree(tgcred);
 103 }
 104 #endif
 105
 106 /*
 107  * Release a set of thread group credentials.
 108  */
 109 static void release_tgcred(struct cred *cred)
 110 {
 111 #ifdef CONFIG_KEYS
 112         struct thread_group_cred *tgcred = cred->tgcred;
 113
 114         if (atomic_dec_and_test(&tgcred->usage))
 115                 call_rcu(&tgcred->rcu, release_tgcred_rcu);
 116 #endif
 117 }
 118
 119 /*
 120  * The RCU callback to actually dispose of a set of credentials
 121  */
 122 static void put_cred_rcu(struct rcu_head *rcu)
 123 {
 124         struct cred *cred = container_of(rcu, struct cred, rcu);
 125
 126         kdebug("put_cred_rcu(%p)", cred);
 127
 128 #ifdef CONFIG_DEBUG_CREDENTIALS
 129         if (cred->magic != CRED_MAGIC_DEAD ||
 130             atomic_read(&cred->usage) != 0 ||
 131             read_cred_subscribers(cred) != 0)
 132                 panic("CRED: put_cred_rcu() sees %p with"
 133                       " mag %x, put %p, usage %d, subscr %d\n",
 134                       cred, cred->magic, cred->put_addr,
 135                       atomic_read(&cred->usage),
 136                       read_cred_subscribers(cred));
 137 #else
 138         if (atomic_read(&cred->usage) != 0)
 139                 panic("CRED: put_cred_rcu() sees %p with usage %d\n",
 140                       cred, atomic_read(&cred->usage));
 141 #endif
 142
 143         security_cred_free(cred);
 144         key_put(cred->thread_keyring);
 145         key_put(cred->request_key_auth);
 146         release_tgcred(cred);
 147         if (cred->group_info)
 148                 put_group_info(cred->group_info);
 149         free_uid(cred->user);
 150         kmem_cache_free(cred_jar, cred);
 151 }
 152
 153 /**
 154  * __put_cred - Destroy a set of credentials
 155  * @cred: The record to release
 156  *
 157  * Destroy a set of credentials on which no references remain.
 158  */
 159 void __put_cred(struct cred *cred)
 160 {
 161         kdebug("__put_cred(%p{%d,%d})", cred,
 162                atomic_read(&cred->usage),
 163                read_cred_subscribers(cred));
 164
 165         BUG_ON(atomic_read(&cred->usage) != 0);
 166 #ifdef CONFIG_DEBUG_CREDENTIALS
 167         BUG_ON(read_cred_subscribers(cred) != 0);
 168         cred->magic = CRED_MAGIC_DEAD;
 169         cred->put_addr = __builtin_return_address(0);
 170 #endif
 171         BUG_ON(cred == current->cred);
 172         BUG_ON(cred == current->real_cred);
 173
 174         call_rcu(&cred->rcu, put_cred_rcu);
 175 }
 176 EXPORT_SYMBOL(__put_cred);
 177
 178 /*
 179  * Clean up a task's credentials when it exits
 180  */
 181 void exit_creds(struct task_struct *tsk)
 182 {
 183         struct cred *cred;
 184
 185         kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
 186                atomic_read(&tsk->cred->usage),
 187                read_cred_subscribers(tsk->cred));
 188
 189         cred = (struct cred *) tsk->real_cred;
 190         tsk->real_cred = NULL;
 191         validate_creds(cred);
 192         alter_cred_subscribers(cred, -1);
 193         put_cred(cred);
 194
 195         cred = (struct cred *) tsk->cred;
 196         tsk->cred = NULL;
 197         validate_creds(cred);
 198         alter_cred_subscribers(cred, -1);
 199         put_cred(cred);
 200
 201         cred = (struct cred *) tsk->replacement_session_keyring;
 202         if (cred) {
 203                 tsk->replacement_session_keyring = NULL;
 204                 validate_creds(cred);
 205                 put_cred(cred);
 206         }
 207 }
 208
 209 /**
 210  * get_task_cred - Get another task's objective credentials
 211  * @task: The task to query
 212  *
 213  * Get the objective credentials of a task, pinning them so that they can't go
 214  * away.  Accessing a task's credentials directly is not permitted.
 215  *
 216  * The caller must also make sure task doesn't get deleted, either by holding a
 217  * ref on task or by holding tasklist_lock to prevent it from being unlinked.
 218  */
 219 const struct cred *get_task_cred(struct task_struct *task)
 220 {
 221         const struct cred *cred;
 222
 223         rcu_read_lock();
 224
 225         do {
 226                 cred = __task_cred((task));
 227                 BUG_ON(!cred);
 228         } while (!atomic_inc_not_zero(&((struct cred *)cred)->usage));
 229
 230         rcu_read_unlock();
 231         return cred;
 232 }
 233
 234 /*
 235  * Allocate blank credentials, such that the credentials can be filled in at a
 236  * later date without risk of ENOMEM.
 237  */
 238 struct cred *cred_alloc_blank(void)
 239 {
 240         struct cred *new;
 241
 242         new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
 243         if (!new)
 244                 return NULL;
 245
 246 #ifdef CONFIG_KEYS
 247         new->tgcred = kzalloc(sizeof(*new->tgcred), GFP_KERNEL);
 248         if (!new->tgcred) {
 249                 kmem_cache_free(cred_jar, new);
 250                 return NULL;
 251         }
 252         atomic_set(&new->tgcred->usage, 1);
 253 #endif
 254
 255         atomic_set(&new->usage, 1);
 256 #ifdef CONFIG_DEBUG_CREDENTIALS
 257         new->magic = CRED_MAGIC;
 258 #endif
 259
 260         if (security_cred_alloc_blank(new, GFP_KERNEL) < 0)
 261                 goto error;
 262
 263         return new;
 264
 265 error:
 266         abort_creds(new);
 267         return NULL;
 268 }
 269
 270 /**
 271  * prepare_creds - Prepare a new set of credentials for modification
 272  *
 273  * Prepare a new set of task credentials for modification.  A task's creds
 274  * shouldn't generally be modified directly, therefore this function is used to
 275  * prepare a new copy, which the caller then modifies and then commits by
 276  * calling commit_creds().
 277  *
 278  * Preparation involves making a copy of the objective creds for modification.
 279  *
 280  * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
 281  *
 282  * Call commit_creds() or abort_creds() to clean up.
 283  */
 284 struct cred *prepare_creds(void)
 285 {
 286         struct task_struct *task = current;
 287         const struct cred *old;
 288         struct cred *new;
 289
 290         validate_process_creds();
 291
 292         new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
 293         if (!new)
 294                 return NULL;
 295
 296         kdebug("prepare_creds() alloc %p", new);
 297
 298         old = task->cred;
 299         memcpy(new, old, sizeof(struct cred));
 300
 301         atomic_set(&new->usage, 1);
 302         set_cred_subscribers(new, 0);
 303         get_group_info(new->group_info);
 304         get_uid(new->user);
 305
 306 #ifdef CONFIG_KEYS
 307         key_get(new->thread_keyring);
 308         key_get(new->request_key_auth);
 309         atomic_inc(&new->tgcred->usage);
 310 #endif
 311
 312 #ifdef CONFIG_SECURITY
 313         new->security = NULL;
 314 #endif
 315
 316         if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
 317                 goto error;
 318         validate_creds(new);
 319         return new;
 320
 321 error:
 322         abort_creds(new);
 323         return NULL;
 324 }
 325 EXPORT_SYMBOL(prepare_creds);
 326
 327 /*
 328  * Prepare credentials for current to perform an execve()
 329  * - The caller must hold ->cred_guard_mutex
 330  */
 331 struct cred *prepare_exec_creds(void)
 332 {
 333         struct thread_group_cred *tgcred = NULL;
 334         struct cred *new;
 335
 336 #ifdef CONFIG_KEYS
 337         tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
 338         if (!tgcred)
 339                 return NULL;
 340 #endif
 341
 342         new = prepare_creds();
 343         if (!new) {
 344                 kfree(tgcred);
 345                 return new;
 346         }
 347
 348 #ifdef CONFIG_KEYS
 349         /* newly exec'd tasks don't get a thread keyring */
 350         key_put(new->thread_keyring);
 351         new->thread_keyring = NULL;
 352
 353         /* create a new per-thread-group creds for all this set of threads to
 354          * share */
 355         memcpy(tgcred, new->tgcred, sizeof(struct thread_group_cred));
 356
 357         atomic_set(&tgcred->usage, 1);
 358         spin_lock_init(&tgcred->lock);
 359
 360         /* inherit the session keyring; new process keyring */
 361         key_get(tgcred->session_keyring);
 362         tgcred->process_keyring = NULL;
 363
 364         release_tgcred(new);
 365         new->tgcred = tgcred;
 366 #endif
 367
 368         return new;
 369 }
 370
 371 /*
 372  * Copy credentials for the new process created by fork()
 373  *
 374  * We share if we can, but under some circumstances we have to generate a new
 375  * set.
 376  *
 377  * The new process gets the current process's subjective credentials as its
 378  * objective and subjective credentials
 379  */
 380 int copy_creds(struct task_struct *p, unsigned long clone_flags)
 381 {
 382 #ifdef CONFIG_KEYS
 383         struct thread_group_cred *tgcred;
 384 #endif
 385         struct cred *new;
 386         int ret;
 387
 388         if (
 389 #ifdef CONFIG_KEYS
 390                 !p->cred->thread_keyring &&
 391 #endif
 392                 clone_flags & CLONE_THREAD
 393             ) {
 394                 p->real_cred = get_cred(p->cred);
 395                 get_cred(p->cred);
 396                 alter_cred_subscribers(p->cred, 2);
 397                 kdebug("share_creds(%p{%d,%d})",
 398                        p->cred, atomic_read(&p->cred->usage),
 399                        read_cred_subscribers(p->cred));
 400                 atomic_inc(&p->cred->user->processes);
 401                 return 0;
 402         }
 403
 404         new = prepare_creds();
 405         if (!new)
 406                 return -ENOMEM;
 407
 408         if (clone_flags & CLONE_NEWUSER) {
 409                 ret = create_user_ns(new);
 410                 if (ret < 0)
 411                         goto error_put;
 412         }
 413
 414         /* cache user_ns in cred.  Doesn't need a refcount because it will
 415          * stay pinned by cred->user
 416          */
 417         new->user_ns = new->user->user_ns;
 418
 419 #ifdef CONFIG_KEYS
 420         /* new threads get their own thread keyrings if their parent already
 421          * had one */
 422         if (new->thread_keyring) {
 423                 key_put(new->thread_keyring);
 424                 new->thread_keyring = NULL;
 425                 if (clone_flags & CLONE_THREAD)
 426                         install_thread_keyring_to_cred(new);
 427         }
 428
 429         /* we share the process and session keyrings between all the threads in
 430          * a process - this is slightly icky as we violate COW credentials a
 431          * bit */
 432         if (!(clone_flags & CLONE_THREAD)) {
 433                 tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
 434                 if (!tgcred) {
 435                         ret = -ENOMEM;
 436                         goto error_put;
 437                 }
 438                 atomic_set(&tgcred->usage, 1);
 439                 spin_lock_init(&tgcred->lock);
 440                 tgcred->process_keyring = NULL;
 441                 tgcred->session_keyring = key_get(new->tgcred->session_keyring);
 442
 443                 release_tgcred(new);
 444                 new->tgcred = tgcred;
 445         }
 446 #endif
 447
 448         atomic_inc(&new->user->processes);
 449         p->cred = p->real_cred = get_cred(new);
 450         alter_cred_subscribers(new, 2);
 451         validate_creds(new);
 452         return 0;
 453
 454 error_put:
 455         put_cred(new);
 456         return ret;
 457 }
 458
 459 /**
 460  * commit_creds - Install new credentials upon the current task
 461  * @new: The credentials to be assigned
 462  *
 463  * Install a new set of credentials to the current task, using RCU to replace
 464  * the old set.  Both the objective and the subjective credentials pointers are
 465  * updated.  This function may not be called if the subjective credentials are
 466  * in an overridden state.
 467  *
 468  * This function eats the caller's reference to the new credentials.
 469  *
 470  * Always returns 0 thus allowing this function to be tail-called at the end
 471  * of, say, sys_setgid().
 472  */
 473 int commit_creds(struct cred *new)
 474 {
 475         struct task_struct *task = current;
 476         const struct cred *old = task->real_cred;
 477
 478         kdebug("commit_creds(%p{%d,%d})", new,
 479                atomic_read(&new->usage),
 480                read_cred_subscribers(new));
 481
 482         BUG_ON(task->cred != old);
 483 #ifdef CONFIG_DEBUG_CREDENTIALS
 484         BUG_ON(read_cred_subscribers(old) < 2);
 485         validate_creds(old);
 486         validate_creds(new);
 487 #endif
 488         BUG_ON(atomic_read(&new->usage) < 1);
 489
 490         get_cred(new); /* we will require a ref for the subj creds too */
 491
 492         /* dumpability changes */
 493         if (old->euid != new->euid ||
 494             old->egid != new->egid ||
 495             old->fsuid != new->fsuid ||
 496             old->fsgid != new->fsgid ||
 497             !cap_issubset(new->cap_permitted, old->cap_permitted)) {
 498                 if (task->mm)
 499                         set_dumpable(task->mm, suid_dumpable);
 500                 task->pdeath_signal = 0;
 501                 smp_wmb();
 502         }
 503
 504         /* alter the thread keyring */
 505         if (new->fsuid != old->fsuid)
 506                 key_fsuid_changed(task);
 507         if (new->fsgid != old->fsgid)
 508                 key_fsgid_changed(task);
 509
 510         /* do it
 511          * RLIMIT_NPROC limits on user->processes have already been checked
 512          * in set_user().
 513          */
 514         alter_cred_subscribers(new, 2);
 515         if (new->user != old->user)
 516                 atomic_inc(&new->user->processes);
 517         rcu_assign_pointer(task->real_cred, new);
 518         rcu_assign_pointer(task->cred, new);
 519         if (new->user != old->user)
 520                 atomic_dec(&old->user->processes);
 521         alter_cred_subscribers(old, -2);
 522
 523         /* send notifications */
 524         if (new->uid   != old->uid  ||
 525             new->euid  != old->euid ||
 526             new->suid  != old->suid ||
 527             new->fsuid != old->fsuid)
 528                 proc_id_connector(task, PROC_EVENT_UID);
 529
 530         if (new->gid   != old->gid  ||
 531             new->egid  != old->egid ||
 532             new->sgid  != old->sgid ||
 533             new->fsgid != old->fsgid)
 534                 proc_id_connector(task, PROC_EVENT_GID);
 535
 536         /* release the old obj and subj refs both */
 537         put_cred(old);
 538         put_cred(old);
 539         return 0;
 540 }
 541 EXPORT_SYMBOL(commit_creds);
 542
 543 /**
 544  * abort_creds - Discard a set of credentials and unlock the current task
 545  * @new: The credentials that were going to be applied
 546  *
 547  * Discard a set of credentials that were under construction and unlock the
 548  * current task.
 549  */
 550 void abort_creds(struct cred *new)
 551 {
 552         kdebug("abort_creds(%p{%d,%d})", new,
 553                atomic_read(&new->usage),
 554                read_cred_subscribers(new));
 555
 556 #ifdef CONFIG_DEBUG_CREDENTIALS
 557         BUG_ON(read_cred_subscribers(new) != 0);
 558 #endif
 559         BUG_ON(atomic_read(&new->usage) < 1);
 560         put_cred(new);
 561 }
 562 EXPORT_SYMBOL(abort_creds);
 563
 564 /**
 565  * override_creds - Override the current process's subjective credentials
 566  * @new: The credentials to be assigned
 567  *
 568  * Install a set of temporary override subjective credentials on the current
 569  * process, returning the old set for later reversion.
 570  */
 571 const struct cred *override_creds(const struct cred *new)
 572 {
 573         const struct cred *old = current->cred;
 574
 575         kdebug("override_creds(%p{%d,%d})", new,
 576                atomic_read(&new->usage),
 577                read_cred_subscribers(new));
 578
 579         validate_creds(old);
 580         validate_creds(new);
 581         get_cred(new);
 582         alter_cred_subscribers(new, 1);
 583         rcu_assign_pointer(current->cred, new);
 584         alter_cred_subscribers(old, -1);
 585
 586         kdebug("override_creds() = %p{%d,%d}", old,
 587                atomic_read(&old->usage),
 588                read_cred_subscribers(old));
 589         return old;
 590 }
 591 EXPORT_SYMBOL(override_creds);
 592
 593 /**
 594  * revert_creds - Revert a temporary subjective credentials override
 595  * @old: The credentials to be restored
 596  *
 597  * Revert a temporary set of override subjective credentials to an old set,
 598  * discarding the override set.
 599  */
 600 void revert_creds(const struct cred *old)
 601 {
 602         const struct cred *override = current->cred;
 603
 604         kdebug("revert_creds(%p{%d,%d})", old,
 605                atomic_read(&old->usage),
 606                read_cred_subscribers(old));
 607
 608         validate_creds(old);
 609         validate_creds(override);
 610         alter_cred_subscribers(old, 1);
 611         rcu_assign_pointer(current->cred, old);
 612         alter_cred_subscribers(override, -1);
 613         put_cred(override);
 614 }
 615 EXPORT_SYMBOL(revert_creds);
 616
 617 /*
 618  * initialise the credentials stuff
 619  */
 620 void __init cred_init(void)
 621 {
 622         /* allocate a slab in which we can store credentials */
 623         cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred),
 624                                      0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
 625 }
 626
 627 /**
 628  * prepare_kernel_cred - Prepare a set of credentials for a kernel service
 629  * @daemon: A userspace daemon to be used as a reference
 630  *
 631  * Prepare a set of credentials for a kernel service.  This can then be used to
 632  * override a task's own credentials so that work can be done on behalf of that
 633  * task that requires a different subjective context.
 634  *
 635  * @daemon is used to provide a base for the security record, but can be NULL.
 636  * If @daemon is supplied, then the security data will be derived from that;
 637  * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
 638  *
 639  * The caller may change these controls afterwards if desired.
 640  *
 641  * Returns the new credentials or NULL if out of memory.
 642  *
 643  * Does not take, and does not return holding current->cred_replace_mutex.
 644  */
 645 struct cred *prepare_kernel_cred(struct task_struct *daemon)
 646 {
 647 #ifdef CONFIG_KEYS
 648         struct thread_group_cred *tgcred;
 649 #endif
 650         const struct cred *old;
 651         struct cred *new;
 652
 653         new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
 654         if (!new)
 655                 return NULL;
 656
 657 #ifdef CONFIG_KEYS
 658         tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
 659         if (!tgcred) {
 660                 kmem_cache_free(cred_jar, new);
 661                 return NULL;
 662         }
 663 #endif
 664
 665         kdebug("prepare_kernel_cred() alloc %p", new);
 666
 667         if (daemon)
 668                 old = get_task_cred(daemon);
 669         else
 670                 old = get_cred(&init_cred);
 671
 672         validate_creds(old);
 673
 674         *new = *old;
 675         atomic_set(&new->usage, 1);
 676         set_cred_subscribers(new, 0);
 677         get_uid(new->user);
 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                cred->uid, cred->euid, cred->suid, cred->fsuid);
 803         printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
 804                cred->gid, cred->egid, cred->sgid, cred->fsgid);
 805 #ifdef CONFIG_SECURITY
 806         printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
 807         if ((unsigned long) cred->security >= PAGE_SIZE &&
 808             (((unsigned long) cred->security & 0xffffff00) !=
 809              (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
 810                 printk(KERN_ERR "CRED: ->security {%x, %x}\n",
 811                        ((u32*)cred->security)[0],
 812                        ((u32*)cred->security)[1]);
 813 #endif
 814 }
 815
 816 /*
 817  * report use of invalid credentials
 818  */
 819 void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
 820 {
 821         printk(KERN_ERR "CRED: Invalid credentials\n");
 822         printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 823         dump_invalid_creds(cred, "Specified", current);
 824         BUG();
 825 }
 826 EXPORT_SYMBOL(__invalid_creds);
 827
 828 /*
 829  * check the credentials on a process
 830  */
 831 void __validate_process_creds(struct task_struct *tsk,
 832                               const char *file, unsigned line)
 833 {
 834         if (tsk->cred == tsk->real_cred) {
 835                 if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
 836                              creds_are_invalid(tsk->cred)))
 837                         goto invalid_creds;
 838         } else {
 839                 if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
 840                              read_cred_subscribers(tsk->cred) < 1 ||
 841                              creds_are_invalid(tsk->real_cred) ||
 842                              creds_are_invalid(tsk->cred)))
 843                         goto invalid_creds;
 844         }
 845         return;
 846
 847 invalid_creds:
 848         printk(KERN_ERR "CRED: Invalid process credentials\n");
 849         printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 850
 851         dump_invalid_creds(tsk->real_cred, "Real", tsk);
 852         if (tsk->cred != tsk->real_cred)
 853                 dump_invalid_creds(tsk->cred, "Effective", tsk);
 854         else
 855                 printk(KERN_ERR "CRED: Effective creds == Real creds\n");
 856         BUG();
 857 }
 858 EXPORT_SYMBOL(__validate_process_creds);
 859
 860 /*
 861  * check creds for do_exit()
 862  */
 863 void validate_creds_for_do_exit(struct task_struct *tsk)
 864 {
 865         kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
 866                tsk->real_cred, tsk->cred,
 867                atomic_read(&tsk->cred->usage),
 868                read_cred_subscribers(tsk->cred));
 869
 870         __validate_process_creds(tsk, __FILE__, __LINE__);
 871 }
 872
 873 #endif /* CONFIG_DEBUG_CREDENTIALS */