kernel/cred.c

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