linux/kernel/cred.c
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   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#define kdebug(FMT, ...) \
  26        no_printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
  27#endif
  28
  29static struct kmem_cache *cred_jar;
  30
  31/*
  32 * The common credentials for the initial task's thread group
  33 */
  34#ifdef CONFIG_KEYS
  35static struct thread_group_cred init_tgcred = {
  36        .usage  = ATOMIC_INIT(2),
  37        .tgid   = 0,
  38        .lock   = SPIN_LOCK_UNLOCKED,
  39};
  40#endif
  41
  42/*
  43 * The initial credentials for the initial task
  44 */
  45struct 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_INIT_INH_SET,
  53        .cap_permitted          = CAP_FULL_SET,
  54        .cap_effective          = CAP_INIT_EFF_SET,
  55        .cap_bset               = CAP_INIT_BSET,
  56        .user                   = INIT_USER,
  57        .group_info             = &init_groups,
  58#ifdef CONFIG_KEYS
  59        .tgcred                 = &init_tgcred,
  60#endif
  61};
  62
  63static inline void set_cred_subscribers(struct cred *cred, int n)
  64{
  65#ifdef CONFIG_DEBUG_CREDENTIALS
  66        atomic_set(&cred->subscribers, n);
  67#endif
  68}
  69
  70static inline int read_cred_subscribers(const struct cred *cred)
  71{
  72#ifdef CONFIG_DEBUG_CREDENTIALS
  73        return atomic_read(&cred->subscribers);
  74#else
  75        return 0;
  76#endif
  77}
  78
  79static inline void alter_cred_subscribers(const struct cred *_cred, int n)
  80{
  81#ifdef CONFIG_DEBUG_CREDENTIALS
  82        struct cred *cred = (struct cred *) _cred;
  83
  84        atomic_add(n, &cred->subscribers);
  85#endif
  86}
  87
  88/*
  89 * Dispose of the shared task group credentials
  90 */
  91#ifdef CONFIG_KEYS
  92static void release_tgcred_rcu(struct rcu_head *rcu)
  93{
  94        struct thread_group_cred *tgcred =
  95                container_of(rcu, struct thread_group_cred, rcu);
  96
  97        BUG_ON(atomic_read(&tgcred->usage) != 0);
  98
  99        key_put(tgcred->session_keyring);
 100        key_put(tgcred->process_keyring);
 101        kfree(tgcred);
 102}
 103#endif
 104
 105/*
 106 * Release a set of thread group credentials.
 107 */
 108static void release_tgcred(struct cred *cred)
 109{
 110#ifdef CONFIG_KEYS
 111        struct thread_group_cred *tgcred = cred->tgcred;
 112
 113        if (atomic_dec_and_test(&tgcred->usage))
 114                call_rcu(&tgcred->rcu, release_tgcred_rcu);
 115#endif
 116}
 117
 118/*
 119 * The RCU callback to actually dispose of a set of credentials
 120 */
 121static void put_cred_rcu(struct rcu_head *rcu)
 122{
 123        struct cred *cred = container_of(rcu, struct cred, rcu);
 124
 125        kdebug("put_cred_rcu(%p)", cred);
 126
 127#ifdef CONFIG_DEBUG_CREDENTIALS
 128        if (cred->magic != CRED_MAGIC_DEAD ||
 129            atomic_read(&cred->usage) != 0 ||
 130            read_cred_subscribers(cred) != 0)
 131                panic("CRED: put_cred_rcu() sees %p with"
 132                      " mag %x, put %p, usage %d, subscr %d\n",
 133                      cred, cred->magic, cred->put_addr,
 134                      atomic_read(&cred->usage),
 135                      read_cred_subscribers(cred));
 136#else
 137        if (atomic_read(&cred->usage) != 0)
 138                panic("CRED: put_cred_rcu() sees %p with usage %d\n",
 139                      cred, atomic_read(&cred->usage));
 140#endif
 141
 142        security_cred_free(cred);
 143        key_put(cred->thread_keyring);
 144        key_put(cred->request_key_auth);
 145        release_tgcred(cred);
 146        if (cred->group_info)
 147                put_group_info(cred->group_info);
 148        free_uid(cred->user);
 149        kmem_cache_free(cred_jar, cred);
 150}
 151
 152/**
 153 * __put_cred - Destroy a set of credentials
 154 * @cred: The record to release
 155 *
 156 * Destroy a set of credentials on which no references remain.
 157 */
 158void __put_cred(struct cred *cred)
 159{
 160        kdebug("__put_cred(%p{%d,%d})", cred,
 161               atomic_read(&cred->usage),
 162               read_cred_subscribers(cred));
 163
 164        BUG_ON(atomic_read(&cred->usage) != 0);
 165#ifdef CONFIG_DEBUG_CREDENTIALS
 166        BUG_ON(read_cred_subscribers(cred) != 0);
 167        cred->magic = CRED_MAGIC_DEAD;
 168        cred->put_addr = __builtin_return_address(0);
 169#endif
 170        BUG_ON(cred == current->cred);
 171        BUG_ON(cred == current->real_cred);
 172
 173        call_rcu(&cred->rcu, put_cred_rcu);
 174}
 175EXPORT_SYMBOL(__put_cred);
 176
 177/*
 178 * Clean up a task's credentials when it exits
 179 */
 180void exit_creds(struct task_struct *tsk)
 181{
 182        struct cred *cred;
 183
 184        kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
 185               atomic_read(&tsk->cred->usage),
 186               read_cred_subscribers(tsk->cred));
 187
 188        cred = (struct cred *) tsk->real_cred;
 189        tsk->real_cred = NULL;
 190        validate_creds(cred);
 191        alter_cred_subscribers(cred, -1);
 192        put_cred(cred);
 193
 194        cred = (struct cred *) tsk->cred;
 195        tsk->cred = NULL;
 196        validate_creds(cred);
 197        alter_cred_subscribers(cred, -1);
 198        put_cred(cred);
 199
 200        cred = (struct cred *) tsk->replacement_session_keyring;
 201        if (cred) {
 202                tsk->replacement_session_keyring = NULL;
 203                validate_creds(cred);
 204                put_cred(cred);
 205        }
 206}
 207
 208/**
 209 * get_task_cred - Get another task's objective credentials
 210 * @task: The task to query
 211 *
 212 * Get the objective credentials of a task, pinning them so that they can't go
 213 * away.  Accessing a task's credentials directly is not permitted.
 214 *
 215 * The caller must also make sure task doesn't get deleted, either by holding a
 216 * ref on task or by holding tasklist_lock to prevent it from being unlinked.
 217 */
 218const struct cred *get_task_cred(struct task_struct *task)
 219{
 220        const struct cred *cred;
 221
 222        rcu_read_lock();
 223
 224        do {
 225                cred = __task_cred((task));
 226                BUG_ON(!cred);
 227        } while (!atomic_inc_not_zero(&((struct cred *)cred)->usage));
 228
 229        rcu_read_unlock();
 230        return cred;
 231}
 232
 233/*
 234 * Allocate blank credentials, such that the credentials can be filled in at a
 235 * later date without risk of ENOMEM.
 236 */
 237struct cred *cred_alloc_blank(void)
 238{
 239        struct cred *new;
 240
 241        new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
 242        if (!new)
 243                return NULL;
 244
 245#ifdef CONFIG_KEYS
 246        new->tgcred = kzalloc(sizeof(*new->tgcred), GFP_KERNEL);
 247        if (!new->tgcred) {
 248                kmem_cache_free(cred_jar, new);
 249                return NULL;
 250        }
 251        atomic_set(&new->tgcred->usage, 1);
 252#endif
 253
 254        atomic_set(&new->usage, 1);
 255
 256        if (security_cred_alloc_blank(new, GFP_KERNEL) < 0)
 257                goto error;
 258
 259#ifdef CONFIG_DEBUG_CREDENTIALS
 260        new->magic = CRED_MAGIC;
 261#endif
 262        return new;
 263
 264error:
 265        abort_creds(new);
 266        return NULL;
 267}
 268
 269/**
 270 * prepare_creds - Prepare a new set of credentials for modification
 271 *
 272 * Prepare a new set of task credentials for modification.  A task's creds
 273 * shouldn't generally be modified directly, therefore this function is used to
 274 * prepare a new copy, which the caller then modifies and then commits by
 275 * calling commit_creds().
 276 *
 277 * Preparation involves making a copy of the objective creds for modification.
 278 *
 279 * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
 280 *
 281 * Call commit_creds() or abort_creds() to clean up.
 282 */
 283struct cred *prepare_creds(void)
 284{
 285        struct task_struct *task = current;
 286        const struct cred *old;
 287        struct cred *new;
 288
 289        validate_process_creds();
 290
 291        new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
 292        if (!new)
 293                return NULL;
 294
 295        kdebug("prepare_creds() alloc %p", new);
 296
 297        old = task->cred;
 298        memcpy(new, old, sizeof(struct cred));
 299
 300        atomic_set(&new->usage, 1);
 301        set_cred_subscribers(new, 0);
 302        get_group_info(new->group_info);
 303        get_uid(new->user);
 304
 305#ifdef CONFIG_KEYS
 306        key_get(new->thread_keyring);
 307        key_get(new->request_key_auth);
 308        atomic_inc(&new->tgcred->usage);
 309#endif
 310
 311#ifdef CONFIG_SECURITY
 312        new->security = NULL;
 313#endif
 314
 315        if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
 316                goto error;
 317        validate_creds(new);
 318        return new;
 319
 320error:
 321        abort_creds(new);
 322        return NULL;
 323}
 324EXPORT_SYMBOL(prepare_creds);
 325
 326/*
 327 * Prepare credentials for current to perform an execve()
 328 * - The caller must hold current->cred_guard_mutex
 329 */
 330struct cred *prepare_exec_creds(void)
 331{
 332        struct thread_group_cred *tgcred = NULL;
 333        struct cred *new;
 334
 335#ifdef CONFIG_KEYS
 336        tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
 337        if (!tgcred)
 338                return NULL;
 339#endif
 340
 341        new = prepare_creds();
 342        if (!new) {
 343                kfree(tgcred);
 344                return new;
 345        }
 346
 347#ifdef CONFIG_KEYS
 348        /* newly exec'd tasks don't get a thread keyring */
 349        key_put(new->thread_keyring);
 350        new->thread_keyring = NULL;
 351
 352        /* create a new per-thread-group creds for all this set of threads to
 353         * share */
 354        memcpy(tgcred, new->tgcred, sizeof(struct thread_group_cred));
 355
 356        atomic_set(&tgcred->usage, 1);
 357        spin_lock_init(&tgcred->lock);
 358
 359        /* inherit the session keyring; new process keyring */
 360        key_get(tgcred->session_keyring);
 361        tgcred->process_keyring = NULL;
 362
 363        release_tgcred(new);
 364        new->tgcred = tgcred;
 365#endif
 366
 367        return new;
 368}
 369
 370/*
 371 * Copy credentials for the new process created by fork()
 372 *
 373 * We share if we can, but under some circumstances we have to generate a new
 374 * set.
 375 *
 376 * The new process gets the current process's subjective credentials as its
 377 * objective and subjective credentials
 378 */
 379int copy_creds(struct task_struct *p, unsigned long clone_flags)
 380{
 381#ifdef CONFIG_KEYS
 382        struct thread_group_cred *tgcred;
 383#endif
 384        struct cred *new;
 385        int ret;
 386
 387        mutex_init(&p->cred_guard_mutex);
 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#ifdef CONFIG_KEYS
 416        /* new threads get their own thread keyrings if their parent already
 417         * had one */
 418        if (new->thread_keyring) {
 419                key_put(new->thread_keyring);
 420                new->thread_keyring = NULL;
 421                if (clone_flags & CLONE_THREAD)
 422                        install_thread_keyring_to_cred(new);
 423        }
 424
 425        /* we share the process and session keyrings between all the threads in
 426         * a process - this is slightly icky as we violate COW credentials a
 427         * bit */
 428        if (!(clone_flags & CLONE_THREAD)) {
 429                tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
 430                if (!tgcred) {
 431                        ret = -ENOMEM;
 432                        goto error_put;
 433                }
 434                atomic_set(&tgcred->usage, 1);
 435                spin_lock_init(&tgcred->lock);
 436                tgcred->process_keyring = NULL;
 437                tgcred->session_keyring = key_get(new->tgcred->session_keyring);
 438
 439                release_tgcred(new);
 440                new->tgcred = tgcred;
 441        }
 442#endif
 443
 444        atomic_inc(&new->user->processes);
 445        p->cred = p->real_cred = get_cred(new);
 446        alter_cred_subscribers(new, 2);
 447        validate_creds(new);
 448        return 0;
 449
 450error_put:
 451        put_cred(new);
 452        return ret;
 453}
 454
 455/**
 456 * commit_creds - Install new credentials upon the current task
 457 * @new: The credentials to be assigned
 458 *
 459 * Install a new set of credentials to the current task, using RCU to replace
 460 * the old set.  Both the objective and the subjective credentials pointers are
 461 * updated.  This function may not be called if the subjective credentials are
 462 * in an overridden state.
 463 *
 464 * This function eats the caller's reference to the new credentials.
 465 *
 466 * Always returns 0 thus allowing this function to be tail-called at the end
 467 * of, say, sys_setgid().
 468 */
 469int commit_creds(struct cred *new)
 470{
 471        struct task_struct *task = current;
 472        const struct cred *old = task->real_cred;
 473
 474        kdebug("commit_creds(%p{%d,%d})", new,
 475               atomic_read(&new->usage),
 476               read_cred_subscribers(new));
 477
 478        BUG_ON(task->cred != old);
 479#ifdef CONFIG_DEBUG_CREDENTIALS
 480        BUG_ON(read_cred_subscribers(old) < 2);
 481        validate_creds(old);
 482        validate_creds(new);
 483#endif
 484        BUG_ON(atomic_read(&new->usage) < 1);
 485
 486        get_cred(new); /* we will require a ref for the subj creds too */
 487
 488        /* dumpability changes */
 489        if (old->euid != new->euid ||
 490            old->egid != new->egid ||
 491            old->fsuid != new->fsuid ||
 492            old->fsgid != new->fsgid ||
 493            !cap_issubset(new->cap_permitted, old->cap_permitted)) {
 494                if (task->mm)
 495                        set_dumpable(task->mm, suid_dumpable);
 496                task->pdeath_signal = 0;
 497                smp_wmb();
 498        }
 499
 500        /* alter the thread keyring */
 501        if (new->fsuid != old->fsuid)
 502                key_fsuid_changed(task);
 503        if (new->fsgid != old->fsgid)
 504                key_fsgid_changed(task);
 505
 506        /* do it
 507         * - What if a process setreuid()'s and this brings the
 508         *   new uid over his NPROC rlimit?  We can check this now
 509         *   cheaply with the new uid cache, so if it matters
 510         *   we should be checking for it.  -DaveM
 511         */
 512        alter_cred_subscribers(new, 2);
 513        if (new->user != old->user)
 514                atomic_inc(&new->user->processes);
 515        rcu_assign_pointer(task->real_cred, new);
 516        rcu_assign_pointer(task->cred, new);
 517        if (new->user != old->user)
 518                atomic_dec(&old->user->processes);
 519        alter_cred_subscribers(old, -2);
 520
 521        /* send notifications */
 522        if (new->uid   != old->uid  ||
 523            new->euid  != old->euid ||
 524            new->suid  != old->suid ||
 525            new->fsuid != old->fsuid)
 526                proc_id_connector(task, PROC_EVENT_UID);
 527
 528        if (new->gid   != old->gid  ||
 529            new->egid  != old->egid ||
 530            new->sgid  != old->sgid ||
 531            new->fsgid != old->fsgid)
 532                proc_id_connector(task, PROC_EVENT_GID);
 533
 534        /* release the old obj and subj refs both */
 535        put_cred(old);
 536        put_cred(old);
 537        return 0;
 538}
 539EXPORT_SYMBOL(commit_creds);
 540
 541/**
 542 * abort_creds - Discard a set of credentials and unlock the current task
 543 * @new: The credentials that were going to be applied
 544 *
 545 * Discard a set of credentials that were under construction and unlock the
 546 * current task.
 547 */
 548void abort_creds(struct cred *new)
 549{
 550        kdebug("abort_creds(%p{%d,%d})", new,
 551               atomic_read(&new->usage),
 552               read_cred_subscribers(new));
 553
 554#ifdef CONFIG_DEBUG_CREDENTIALS
 555        BUG_ON(read_cred_subscribers(new) != 0);
 556#endif
 557        BUG_ON(atomic_read(&new->usage) < 1);
 558        put_cred(new);
 559}
 560EXPORT_SYMBOL(abort_creds);
 561
 562/**
 563 * override_creds - Override the current process's subjective credentials
 564 * @new: The credentials to be assigned
 565 *
 566 * Install a set of temporary override subjective credentials on the current
 567 * process, returning the old set for later reversion.
 568 */
 569const struct cred *override_creds(const struct cred *new)
 570{
 571        const struct cred *old = current->cred;
 572
 573        kdebug("override_creds(%p{%d,%d})", new,
 574               atomic_read(&new->usage),
 575               read_cred_subscribers(new));
 576
 577        validate_creds(old);
 578        validate_creds(new);
 579        get_cred(new);
 580        alter_cred_subscribers(new, 1);
 581        rcu_assign_pointer(current->cred, new);
 582        alter_cred_subscribers(old, -1);
 583
 584        kdebug("override_creds() = %p{%d,%d}", old,
 585               atomic_read(&old->usage),
 586               read_cred_subscribers(old));
 587        return old;
 588}
 589EXPORT_SYMBOL(override_creds);
 590
 591/**
 592 * revert_creds - Revert a temporary subjective credentials override
 593 * @old: The credentials to be restored
 594 *
 595 * Revert a temporary set of override subjective credentials to an old set,
 596 * discarding the override set.
 597 */
 598void revert_creds(const struct cred *old)
 599{
 600        const struct cred *override = current->cred;
 601
 602        kdebug("revert_creds(%p{%d,%d})", old,
 603               atomic_read(&old->usage),
 604               read_cred_subscribers(old));
 605
 606        validate_creds(old);
 607        validate_creds(override);
 608        alter_cred_subscribers(old, 1);
 609        rcu_assign_pointer(current->cred, old);
 610        alter_cred_subscribers(override, -1);
 611        put_cred(override);
 612}
 613EXPORT_SYMBOL(revert_creds);
 614
 615/*
 616 * initialise the credentials stuff
 617 */
 618void __init cred_init(void)
 619{
 620        /* allocate a slab in which we can store credentials */
 621        cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred),
 622                                     0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
 623}
 624
 625/**
 626 * prepare_kernel_cred - Prepare a set of credentials for a kernel service
 627 * @daemon: A userspace daemon to be used as a reference
 628 *
 629 * Prepare a set of credentials for a kernel service.  This can then be used to
 630 * override a task's own credentials so that work can be done on behalf of that
 631 * task that requires a different subjective context.
 632 *
 633 * @daemon is used to provide a base for the security record, but can be NULL.
 634 * If @daemon is supplied, then the security data will be derived from that;
 635 * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
 636 *
 637 * The caller may change these controls afterwards if desired.
 638 *
 639 * Returns the new credentials or NULL if out of memory.
 640 *
 641 * Does not take, and does not return holding current->cred_replace_mutex.
 642 */
 643struct cred *prepare_kernel_cred(struct task_struct *daemon)
 644{
 645        const struct cred *old;
 646        struct cred *new;
 647
 648        new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
 649        if (!new)
 650                return NULL;
 651
 652        kdebug("prepare_kernel_cred() alloc %p", new);
 653
 654        if (daemon)
 655                old = get_task_cred(daemon);
 656        else
 657                old = get_cred(&init_cred);
 658
 659        validate_creds(old);
 660
 661        *new = *old;
 662        get_uid(new->user);
 663        get_group_info(new->group_info);
 664
 665#ifdef CONFIG_KEYS
 666        atomic_inc(&init_tgcred.usage);
 667        new->tgcred = &init_tgcred;
 668        new->request_key_auth = NULL;
 669        new->thread_keyring = NULL;
 670        new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
 671#endif
 672
 673#ifdef CONFIG_SECURITY
 674        new->security = NULL;
 675#endif
 676        if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
 677                goto error;
 678
 679        atomic_set(&new->usage, 1);
 680        set_cred_subscribers(new, 0);
 681        put_cred(old);
 682        validate_creds(new);
 683        return new;
 684
 685error:
 686        put_cred(new);
 687        put_cred(old);
 688        return NULL;
 689}
 690EXPORT_SYMBOL(prepare_kernel_cred);
 691
 692/**
 693 * set_security_override - Set the security ID in a set of credentials
 694 * @new: The credentials to alter
 695 * @secid: The LSM security ID to set
 696 *
 697 * Set the LSM security ID in a set of credentials so that the subjective
 698 * security is overridden when an alternative set of credentials is used.
 699 */
 700int set_security_override(struct cred *new, u32 secid)
 701{
 702        return security_kernel_act_as(new, secid);
 703}
 704EXPORT_SYMBOL(set_security_override);
 705
 706/**
 707 * set_security_override_from_ctx - Set the security ID in a set of credentials
 708 * @new: The credentials to alter
 709 * @secctx: The LSM security context to generate the security ID from.
 710 *
 711 * Set the LSM security ID in a set of credentials so that the subjective
 712 * security is overridden when an alternative set of credentials is used.  The
 713 * security ID is specified in string form as a security context to be
 714 * interpreted by the LSM.
 715 */
 716int set_security_override_from_ctx(struct cred *new, const char *secctx)
 717{
 718        u32 secid;
 719        int ret;
 720
 721        ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
 722        if (ret < 0)
 723                return ret;
 724
 725        return set_security_override(new, secid);
 726}
 727EXPORT_SYMBOL(set_security_override_from_ctx);
 728
 729/**
 730 * set_create_files_as - Set the LSM file create context in a set of credentials
 731 * @new: The credentials to alter
 732 * @inode: The inode to take the context from
 733 *
 734 * Change the LSM file creation context in a set of credentials to be the same
 735 * as the object context of the specified inode, so that the new inodes have
 736 * the same MAC context as that inode.
 737 */
 738int set_create_files_as(struct cred *new, struct inode *inode)
 739{
 740        new->fsuid = inode->i_uid;
 741        new->fsgid = inode->i_gid;
 742        return security_kernel_create_files_as(new, inode);
 743}
 744EXPORT_SYMBOL(set_create_files_as);
 745
 746#ifdef CONFIG_DEBUG_CREDENTIALS
 747
 748bool creds_are_invalid(const struct cred *cred)
 749{
 750        if (cred->magic != CRED_MAGIC)
 751                return true;
 752#ifdef CONFIG_SECURITY_SELINUX
 753        if (selinux_is_enabled()) {
 754                if ((unsigned long) cred->security < PAGE_SIZE)
 755                        return true;
 756                if ((*(u32 *)cred->security & 0xffffff00) ==
 757                    (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
 758                        return true;
 759        }
 760#endif
 761        return false;
 762}
 763EXPORT_SYMBOL(creds_are_invalid);
 764
 765/*
 766 * dump invalid credentials
 767 */
 768static void dump_invalid_creds(const struct cred *cred, const char *label,
 769                               const struct task_struct *tsk)
 770{
 771        printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
 772               label, cred,
 773               cred == &init_cred ? "[init]" : "",
 774               cred == tsk->real_cred ? "[real]" : "",
 775               cred == tsk->cred ? "[eff]" : "");
 776        printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
 777               cred->magic, cred->put_addr);
 778        printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
 779               atomic_read(&cred->usage),
 780               read_cred_subscribers(cred));
 781        printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
 782               cred->uid, cred->euid, cred->suid, cred->fsuid);
 783        printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
 784               cred->gid, cred->egid, cred->sgid, cred->fsgid);
 785#ifdef CONFIG_SECURITY
 786        printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
 787        if ((unsigned long) cred->security >= PAGE_SIZE &&
 788            (((unsigned long) cred->security & 0xffffff00) !=
 789             (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
 790                printk(KERN_ERR "CRED: ->security {%x, %x}\n",
 791                       ((u32*)cred->security)[0],
 792                       ((u32*)cred->security)[1]);
 793#endif
 794}
 795
 796/*
 797 * report use of invalid credentials
 798 */
 799void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
 800{
 801        printk(KERN_ERR "CRED: Invalid credentials\n");
 802        printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 803        dump_invalid_creds(cred, "Specified", current);
 804        BUG();
 805}
 806EXPORT_SYMBOL(__invalid_creds);
 807
 808/*
 809 * check the credentials on a process
 810 */
 811void __validate_process_creds(struct task_struct *tsk,
 812                              const char *file, unsigned line)
 813{
 814        if (tsk->cred == tsk->real_cred) {
 815                if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
 816                             creds_are_invalid(tsk->cred)))
 817                        goto invalid_creds;
 818        } else {
 819                if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
 820                             read_cred_subscribers(tsk->cred) < 1 ||
 821                             creds_are_invalid(tsk->real_cred) ||
 822                             creds_are_invalid(tsk->cred)))
 823                        goto invalid_creds;
 824        }
 825        return;
 826
 827invalid_creds:
 828        printk(KERN_ERR "CRED: Invalid process credentials\n");
 829        printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 830
 831        dump_invalid_creds(tsk->real_cred, "Real", tsk);
 832        if (tsk->cred != tsk->real_cred)
 833                dump_invalid_creds(tsk->cred, "Effective", tsk);
 834        else
 835                printk(KERN_ERR "CRED: Effective creds == Real creds\n");
 836        BUG();
 837}
 838EXPORT_SYMBOL(__validate_process_creds);
 839
 840/*
 841 * check creds for do_exit()
 842 */
 843void validate_creds_for_do_exit(struct task_struct *tsk)
 844{
 845        kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
 846               tsk->real_cred, tsk->cred,
 847               atomic_read(&tsk->cred->usage),
 848               read_cred_subscribers(tsk->cred));
 849
 850        __validate_process_creds(tsk, __FILE__, __LINE__);
 851}
 852
 853#endif /* CONFIG_DEBUG_CREDENTIALS */
 854