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