linux/kernel/cred.c
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   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
  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(init_cred.tgcred.lock),
  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_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
  64static 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
  71static 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
  80static 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
  93static 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 */
 109static 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 */
 122static 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 */
 159void __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}
 176EXPORT_SYMBOL(__put_cred);
 177
 178/*
 179 * Clean up a task's credentials when it exits
 180 */
 181void 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 */
 219const 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 */
 238struct 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
 265error:
 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 */
 284struct 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
 321error:
 322        abort_creds(new);
 323        return NULL;
 324}
 325EXPORT_SYMBOL(prepare_creds);
 326
 327/*
 328 * Prepare credentials for current to perform an execve()
 329 * - The caller must hold ->cred_guard_mutex
 330 */
 331struct 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 */
 380int 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
 454error_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 */
 473int 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}
 541EXPORT_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 */
 550void 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}
 562EXPORT_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 */
 571const 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}
 591EXPORT_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 */
 600void 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}
 615EXPORT_SYMBOL(revert_creds);
 616
 617/*
 618 * initialise the credentials stuff
 619 */
 620void __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 */
 645struct cred *prepare_kernel_cred(struct task_struct *daemon)
 646{
 647        const struct cred *old;
 648        struct cred *new;
 649
 650        new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
 651        if (!new)
 652                return NULL;
 653
 654        kdebug("prepare_kernel_cred() alloc %p", new);
 655
 656        if (daemon)
 657                old = get_task_cred(daemon);
 658        else
 659                old = get_cred(&init_cred);
 660
 661        validate_creds(old);
 662
 663        *new = *old;
 664        atomic_set(&new->usage, 1);
 665        set_cred_subscribers(new, 0);
 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        put_cred(old);
 684        validate_creds(new);
 685        return new;
 686
 687error:
 688        put_cred(new);
 689        put_cred(old);
 690        return NULL;
 691}
 692EXPORT_SYMBOL(prepare_kernel_cred);
 693
 694/**
 695 * set_security_override - Set the security ID in a set of credentials
 696 * @new: The credentials to alter
 697 * @secid: The LSM security ID to set
 698 *
 699 * Set the LSM security ID in a set of credentials so that the subjective
 700 * security is overridden when an alternative set of credentials is used.
 701 */
 702int set_security_override(struct cred *new, u32 secid)
 703{
 704        return security_kernel_act_as(new, secid);
 705}
 706EXPORT_SYMBOL(set_security_override);
 707
 708/**
 709 * set_security_override_from_ctx - Set the security ID in a set of credentials
 710 * @new: The credentials to alter
 711 * @secctx: The LSM security context to generate the security ID from.
 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.  The
 715 * security ID is specified in string form as a security context to be
 716 * interpreted by the LSM.
 717 */
 718int set_security_override_from_ctx(struct cred *new, const char *secctx)
 719{
 720        u32 secid;
 721        int ret;
 722
 723        ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
 724        if (ret < 0)
 725                return ret;
 726
 727        return set_security_override(new, secid);
 728}
 729EXPORT_SYMBOL(set_security_override_from_ctx);
 730
 731/**
 732 * set_create_files_as - Set the LSM file create context in a set of credentials
 733 * @new: The credentials to alter
 734 * @inode: The inode to take the context from
 735 *
 736 * Change the LSM file creation context in a set of credentials to be the same
 737 * as the object context of the specified inode, so that the new inodes have
 738 * the same MAC context as that inode.
 739 */
 740int set_create_files_as(struct cred *new, struct inode *inode)
 741{
 742        new->fsuid = inode->i_uid;
 743        new->fsgid = inode->i_gid;
 744        return security_kernel_create_files_as(new, inode);
 745}
 746EXPORT_SYMBOL(set_create_files_as);
 747
 748#ifdef CONFIG_DEBUG_CREDENTIALS
 749
 750bool creds_are_invalid(const struct cred *cred)
 751{
 752        if (cred->magic != CRED_MAGIC)
 753                return true;
 754#ifdef CONFIG_SECURITY_SELINUX
 755        /*
 756         * cred->security == NULL if security_cred_alloc_blank() or
 757         * security_prepare_creds() returned an error.
 758         */
 759        if (selinux_is_enabled() && cred->security) {
 760                if ((unsigned long) cred->security < PAGE_SIZE)
 761                        return true;
 762                if ((*(u32 *)cred->security & 0xffffff00) ==
 763                    (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
 764                        return true;
 765        }
 766#endif
 767        return false;
 768}
 769EXPORT_SYMBOL(creds_are_invalid);
 770
 771/*
 772 * dump invalid credentials
 773 */
 774static void dump_invalid_creds(const struct cred *cred, const char *label,
 775                               const struct task_struct *tsk)
 776{
 777        printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
 778               label, cred,
 779               cred == &init_cred ? "[init]" : "",
 780               cred == tsk->real_cred ? "[real]" : "",
 781               cred == tsk->cred ? "[eff]" : "");
 782        printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
 783               cred->magic, cred->put_addr);
 784        printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
 785               atomic_read(&cred->usage),
 786               read_cred_subscribers(cred));
 787        printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
 788               cred->uid, cred->euid, cred->suid, cred->fsuid);
 789        printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
 790               cred->gid, cred->egid, cred->sgid, cred->fsgid);
 791#ifdef CONFIG_SECURITY
 792        printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
 793        if ((unsigned long) cred->security >= PAGE_SIZE &&
 794            (((unsigned long) cred->security & 0xffffff00) !=
 795             (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
 796                printk(KERN_ERR "CRED: ->security {%x, %x}\n",
 797                       ((u32*)cred->security)[0],
 798                       ((u32*)cred->security)[1]);
 799#endif
 800}
 801
 802/*
 803 * report use of invalid credentials
 804 */
 805void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
 806{
 807        printk(KERN_ERR "CRED: Invalid credentials\n");
 808        printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 809        dump_invalid_creds(cred, "Specified", current);
 810        BUG();
 811}
 812EXPORT_SYMBOL(__invalid_creds);
 813
 814/*
 815 * check the credentials on a process
 816 */
 817void __validate_process_creds(struct task_struct *tsk,
 818                              const char *file, unsigned line)
 819{
 820        if (tsk->cred == tsk->real_cred) {
 821                if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
 822                             creds_are_invalid(tsk->cred)))
 823                        goto invalid_creds;
 824        } else {
 825                if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
 826                             read_cred_subscribers(tsk->cred) < 1 ||
 827                             creds_are_invalid(tsk->real_cred) ||
 828                             creds_are_invalid(tsk->cred)))
 829                        goto invalid_creds;
 830        }
 831        return;
 832
 833invalid_creds:
 834        printk(KERN_ERR "CRED: Invalid process credentials\n");
 835        printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 836
 837        dump_invalid_creds(tsk->real_cred, "Real", tsk);
 838        if (tsk->cred != tsk->real_cred)
 839                dump_invalid_creds(tsk->cred, "Effective", tsk);
 840        else
 841                printk(KERN_ERR "CRED: Effective creds == Real creds\n");
 842        BUG();
 843}
 844EXPORT_SYMBOL(__validate_process_creds);
 845
 846/*
 847 * check creds for do_exit()
 848 */
 849void validate_creds_for_do_exit(struct task_struct *tsk)
 850{
 851        kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
 852               tsk->real_cred, tsk->cred,
 853               atomic_read(&tsk->cred->usage),
 854               read_cred_subscribers(tsk->cred));
 855
 856        __validate_process_creds(tsk, __FILE__, __LINE__);
 857}
 858
 859#endif /* CONFIG_DEBUG_CREDENTIALS */
 860
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