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/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
  30static struct kmem_cache *cred_jar;
  31
  32/*
  33 * The common credentials for the initial task's thread group
  34 */
  35#ifdef CONFIG_KEYS
  36static 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 */
  46struct 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        .uid                    = GLOBAL_ROOT_UID,
  53        .gid                    = GLOBAL_ROOT_GID,
  54        .suid                   = GLOBAL_ROOT_UID,
  55        .sgid                   = GLOBAL_ROOT_GID,
  56        .euid                   = GLOBAL_ROOT_UID,
  57        .egid                   = GLOBAL_ROOT_GID,
  58        .fsuid                  = GLOBAL_ROOT_UID,
  59        .fsgid                  = GLOBAL_ROOT_GID,
  60        .securebits             = SECUREBITS_DEFAULT,
  61        .cap_inheritable        = CAP_EMPTY_SET,
  62        .cap_permitted          = CAP_FULL_SET,
  63        .cap_effective          = CAP_FULL_SET,
  64        .cap_bset               = CAP_FULL_SET,
  65        .user                   = INIT_USER,
  66        .user_ns                = &init_user_ns,
  67        .group_info             = &init_groups,
  68#ifdef CONFIG_KEYS
  69        .tgcred                 = &init_tgcred,
  70#endif
  71};
  72
  73static inline void set_cred_subscribers(struct cred *cred, int n)
  74{
  75#ifdef CONFIG_DEBUG_CREDENTIALS
  76        atomic_set(&cred->subscribers, n);
  77#endif
  78}
  79
  80static inline int read_cred_subscribers(const struct cred *cred)
  81{
  82#ifdef CONFIG_DEBUG_CREDENTIALS
  83        return atomic_read(&cred->subscribers);
  84#else
  85        return 0;
  86#endif
  87}
  88
  89static inline void alter_cred_subscribers(const struct cred *_cred, int n)
  90{
  91#ifdef CONFIG_DEBUG_CREDENTIALS
  92        struct cred *cred = (struct cred *) _cred;
  93
  94        atomic_add(n, &cred->subscribers);
  95#endif
  96}
  97
  98/*
  99 * Dispose of the shared task group credentials
 100 */
 101#ifdef CONFIG_KEYS
 102static void release_tgcred_rcu(struct rcu_head *rcu)
 103{
 104        struct thread_group_cred *tgcred =
 105                container_of(rcu, struct thread_group_cred, rcu);
 106
 107        BUG_ON(atomic_read(&tgcred->usage) != 0);
 108
 109        key_put(tgcred->session_keyring);
 110        key_put(tgcred->process_keyring);
 111        kfree(tgcred);
 112}
 113#endif
 114
 115/*
 116 * Release a set of thread group credentials.
 117 */
 118static void release_tgcred(struct cred *cred)
 119{
 120#ifdef CONFIG_KEYS
 121        struct thread_group_cred *tgcred = cred->tgcred;
 122
 123        if (atomic_dec_and_test(&tgcred->usage))
 124                call_rcu(&tgcred->rcu, release_tgcred_rcu);
 125#endif
 126}
 127
 128/*
 129 * The RCU callback to actually dispose of a set of credentials
 130 */
 131static void put_cred_rcu(struct rcu_head *rcu)
 132{
 133        struct cred *cred = container_of(rcu, struct cred, rcu);
 134
 135        kdebug("put_cred_rcu(%p)", cred);
 136
 137#ifdef CONFIG_DEBUG_CREDENTIALS
 138        if (cred->magic != CRED_MAGIC_DEAD ||
 139            atomic_read(&cred->usage) != 0 ||
 140            read_cred_subscribers(cred) != 0)
 141                panic("CRED: put_cred_rcu() sees %p with"
 142                      " mag %x, put %p, usage %d, subscr %d\n",
 143                      cred, cred->magic, cred->put_addr,
 144                      atomic_read(&cred->usage),
 145                      read_cred_subscribers(cred));
 146#else
 147        if (atomic_read(&cred->usage) != 0)
 148                panic("CRED: put_cred_rcu() sees %p with usage %d\n",
 149                      cred, atomic_read(&cred->usage));
 150#endif
 151
 152        security_cred_free(cred);
 153        key_put(cred->thread_keyring);
 154        key_put(cred->request_key_auth);
 155        release_tgcred(cred);
 156        if (cred->group_info)
 157                put_group_info(cred->group_info);
 158        free_uid(cred->user);
 159        put_user_ns(cred->user_ns);
 160        kmem_cache_free(cred_jar, cred);
 161}
 162
 163/**
 164 * __put_cred - Destroy a set of credentials
 165 * @cred: The record to release
 166 *
 167 * Destroy a set of credentials on which no references remain.
 168 */
 169void __put_cred(struct cred *cred)
 170{
 171        kdebug("__put_cred(%p{%d,%d})", cred,
 172               atomic_read(&cred->usage),
 173               read_cred_subscribers(cred));
 174
 175        BUG_ON(atomic_read(&cred->usage) != 0);
 176#ifdef CONFIG_DEBUG_CREDENTIALS
 177        BUG_ON(read_cred_subscribers(cred) != 0);
 178        cred->magic = CRED_MAGIC_DEAD;
 179        cred->put_addr = __builtin_return_address(0);
 180#endif
 181        BUG_ON(cred == current->cred);
 182        BUG_ON(cred == current->real_cred);
 183
 184        call_rcu(&cred->rcu, put_cred_rcu);
 185}
 186EXPORT_SYMBOL(__put_cred);
 187
 188/*
 189 * Clean up a task's credentials when it exits
 190 */
 191void exit_creds(struct task_struct *tsk)
 192{
 193        struct cred *cred;
 194
 195        kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
 196               atomic_read(&tsk->cred->usage),
 197               read_cred_subscribers(tsk->cred));
 198
 199        cred = (struct cred *) tsk->real_cred;
 200        tsk->real_cred = NULL;
 201        validate_creds(cred);
 202        alter_cred_subscribers(cred, -1);
 203        put_cred(cred);
 204
 205        cred = (struct cred *) tsk->cred;
 206        tsk->cred = NULL;
 207        validate_creds(cred);
 208        alter_cred_subscribers(cred, -1);
 209        put_cred(cred);
 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 */
 222const 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 */
 241struct 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#ifdef CONFIG_DEBUG_CREDENTIALS
 260        new->magic = CRED_MAGIC;
 261#endif
 262
 263        if (security_cred_alloc_blank(new, GFP_KERNEL) < 0)
 264                goto error;
 265
 266        return new;
 267
 268error:
 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 */
 287struct 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        get_user_ns(new->user_ns);
 309
 310#ifdef CONFIG_KEYS
 311        key_get(new->thread_keyring);
 312        key_get(new->request_key_auth);
 313        atomic_inc(&new->tgcred->usage);
 314#endif
 315
 316#ifdef CONFIG_SECURITY
 317        new->security = NULL;
 318#endif
 319
 320        if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
 321                goto error;
 322        validate_creds(new);
 323        return new;
 324
 325error:
 326        abort_creds(new);
 327        return NULL;
 328}
 329EXPORT_SYMBOL(prepare_creds);
 330
 331/*
 332 * Prepare credentials for current to perform an execve()
 333 * - The caller must hold ->cred_guard_mutex
 334 */
 335struct cred *prepare_exec_creds(void)
 336{
 337        struct thread_group_cred *tgcred = NULL;
 338        struct cred *new;
 339
 340#ifdef CONFIG_KEYS
 341        tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
 342        if (!tgcred)
 343                return NULL;
 344#endif
 345
 346        new = prepare_creds();
 347        if (!new) {
 348                kfree(tgcred);
 349                return new;
 350        }
 351
 352#ifdef CONFIG_KEYS
 353        /* newly exec'd tasks don't get a thread keyring */
 354        key_put(new->thread_keyring);
 355        new->thread_keyring = NULL;
 356
 357        /* create a new per-thread-group creds for all this set of threads to
 358         * share */
 359        memcpy(tgcred, new->tgcred, sizeof(struct thread_group_cred));
 360
 361        atomic_set(&tgcred->usage, 1);
 362        spin_lock_init(&tgcred->lock);
 363
 364        /* inherit the session keyring; new process keyring */
 365        key_get(tgcred->session_keyring);
 366        tgcred->process_keyring = NULL;
 367
 368        release_tgcred(new);
 369        new->tgcred = tgcred;
 370#endif
 371
 372        return new;
 373}
 374
 375/*
 376 * Copy credentials for the new process created by fork()
 377 *
 378 * We share if we can, but under some circumstances we have to generate a new
 379 * set.
 380 *
 381 * The new process gets the current process's subjective credentials as its
 382 * objective and subjective credentials
 383 */
 384int copy_creds(struct task_struct *p, unsigned long clone_flags)
 385{
 386#ifdef CONFIG_KEYS
 387        struct thread_group_cred *tgcred;
 388#endif
 389        struct cred *new;
 390        int ret;
 391
 392        if (
 393#ifdef CONFIG_KEYS
 394                !p->cred->thread_keyring &&
 395#endif
 396                clone_flags & CLONE_THREAD
 397            ) {
 398                p->real_cred = get_cred(p->cred);
 399                get_cred(p->cred);
 400                alter_cred_subscribers(p->cred, 2);
 401                kdebug("share_creds(%p{%d,%d})",
 402                       p->cred, atomic_read(&p->cred->usage),
 403                       read_cred_subscribers(p->cred));
 404                atomic_inc(&p->cred->user->processes);
 405                return 0;
 406        }
 407
 408        new = prepare_creds();
 409        if (!new)
 410                return -ENOMEM;
 411
 412        if (clone_flags & CLONE_NEWUSER) {
 413                ret = create_user_ns(new);
 414                if (ret < 0)
 415                        goto error_put;
 416        }
 417
 418#ifdef CONFIG_KEYS
 419        /* new threads get their own thread keyrings if their parent already
 420         * had one */
 421        if (new->thread_keyring) {
 422                key_put(new->thread_keyring);
 423                new->thread_keyring = NULL;
 424                if (clone_flags & CLONE_THREAD)
 425                        install_thread_keyring_to_cred(new);
 426        }
 427
 428        /* we share the process and session keyrings between all the threads in
 429         * a process - this is slightly icky as we violate COW credentials a
 430         * bit */
 431        if (!(clone_flags & CLONE_THREAD)) {
 432                tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
 433                if (!tgcred) {
 434                        ret = -ENOMEM;
 435                        goto error_put;
 436                }
 437                atomic_set(&tgcred->usage, 1);
 438                spin_lock_init(&tgcred->lock);
 439                tgcred->process_keyring = NULL;
 440                tgcred->session_keyring = key_get(new->tgcred->session_keyring);
 441
 442                release_tgcred(new);
 443                new->tgcred = tgcred;
 444        }
 445#endif
 446
 447        atomic_inc(&new->user->processes);
 448        p->cred = p->real_cred = get_cred(new);
 449        alter_cred_subscribers(new, 2);
 450        validate_creds(new);
 451        return 0;
 452
 453error_put:
 454        put_cred(new);
 455        return ret;
 456}
 457
 458/**
 459 * commit_creds - Install new credentials upon the current task
 460 * @new: The credentials to be assigned
 461 *
 462 * Install a new set of credentials to the current task, using RCU to replace
 463 * the old set.  Both the objective and the subjective credentials pointers are
 464 * updated.  This function may not be called if the subjective credentials are
 465 * in an overridden state.
 466 *
 467 * This function eats the caller's reference to the new credentials.
 468 *
 469 * Always returns 0 thus allowing this function to be tail-called at the end
 470 * of, say, sys_setgid().
 471 */
 472int commit_creds(struct cred *new)
 473{
 474        struct task_struct *task = current;
 475        const struct cred *old = task->real_cred;
 476
 477        kdebug("commit_creds(%p{%d,%d})", new,
 478               atomic_read(&new->usage),
 479               read_cred_subscribers(new));
 480
 481        BUG_ON(task->cred != old);
 482#ifdef CONFIG_DEBUG_CREDENTIALS
 483        BUG_ON(read_cred_subscribers(old) < 2);
 484        validate_creds(old);
 485        validate_creds(new);
 486#endif
 487        BUG_ON(atomic_read(&new->usage) < 1);
 488
 489        get_cred(new); /* we will require a ref for the subj creds too */
 490
 491        /* dumpability changes */
 492        if (!uid_eq(old->euid, new->euid) ||
 493            !gid_eq(old->egid, new->egid) ||
 494            !uid_eq(old->fsuid, new->fsuid) ||
 495            !gid_eq(old->fsgid, new->fsgid) ||
 496            !cap_issubset(new->cap_permitted, old->cap_permitted)) {
 497                if (task->mm)
 498                        set_dumpable(task->mm, suid_dumpable);
 499                task->pdeath_signal = 0;
 500                smp_wmb();
 501        }
 502
 503        /* alter the thread keyring */
 504        if (!uid_eq(new->fsuid, old->fsuid))
 505                key_fsuid_changed(task);
 506        if (!gid_eq(new->fsgid, old->fsgid))
 507                key_fsgid_changed(task);
 508
 509        /* do it
 510         * RLIMIT_NPROC limits on user->processes have already been checked
 511         * in set_user().
 512         */
 513        alter_cred_subscribers(new, 2);
 514        if (new->user != old->user)
 515                atomic_inc(&new->user->processes);
 516        rcu_assign_pointer(task->real_cred, new);
 517        rcu_assign_pointer(task->cred, new);
 518        if (new->user != old->user)
 519                atomic_dec(&old->user->processes);
 520        alter_cred_subscribers(old, -2);
 521
 522        /* send notifications */
 523        if (!uid_eq(new->uid,   old->uid)  ||
 524            !uid_eq(new->euid,  old->euid) ||
 525            !uid_eq(new->suid,  old->suid) ||
 526            !uid_eq(new->fsuid, old->fsuid))
 527                proc_id_connector(task, PROC_EVENT_UID);
 528
 529        if (!gid_eq(new->gid,   old->gid)  ||
 530            !gid_eq(new->egid,  old->egid) ||
 531            !gid_eq(new->sgid,  old->sgid) ||
 532            !gid_eq(new->fsgid, old->fsgid))
 533                proc_id_connector(task, PROC_EVENT_GID);
 534
 535        /* release the old obj and subj refs both */
 536        put_cred(old);
 537        put_cred(old);
 538        return 0;
 539}
 540EXPORT_SYMBOL(commit_creds);
 541
 542/**
 543 * abort_creds - Discard a set of credentials and unlock the current task
 544 * @new: The credentials that were going to be applied
 545 *
 546 * Discard a set of credentials that were under construction and unlock the
 547 * current task.
 548 */
 549void abort_creds(struct cred *new)
 550{
 551        kdebug("abort_creds(%p{%d,%d})", new,
 552               atomic_read(&new->usage),
 553               read_cred_subscribers(new));
 554
 555#ifdef CONFIG_DEBUG_CREDENTIALS
 556        BUG_ON(read_cred_subscribers(new) != 0);
 557#endif
 558        BUG_ON(atomic_read(&new->usage) < 1);
 559        put_cred(new);
 560}
 561EXPORT_SYMBOL(abort_creds);
 562
 563/**
 564 * override_creds - Override the current process's subjective credentials
 565 * @new: The credentials to be assigned
 566 *
 567 * Install a set of temporary override subjective credentials on the current
 568 * process, returning the old set for later reversion.
 569 */
 570const struct cred *override_creds(const struct cred *new)
 571{
 572        const struct cred *old = current->cred;
 573
 574        kdebug("override_creds(%p{%d,%d})", new,
 575               atomic_read(&new->usage),
 576               read_cred_subscribers(new));
 577
 578        validate_creds(old);
 579        validate_creds(new);
 580        get_cred(new);
 581        alter_cred_subscribers(new, 1);
 582        rcu_assign_pointer(current->cred, new);
 583        alter_cred_subscribers(old, -1);
 584
 585        kdebug("override_creds() = %p{%d,%d}", old,
 586               atomic_read(&old->usage),
 587               read_cred_subscribers(old));
 588        return old;
 589}
 590EXPORT_SYMBOL(override_creds);
 591
 592/**
 593 * revert_creds - Revert a temporary subjective credentials override
 594 * @old: The credentials to be restored
 595 *
 596 * Revert a temporary set of override subjective credentials to an old set,
 597 * discarding the override set.
 598 */
 599void revert_creds(const struct cred *old)
 600{
 601        const struct cred *override = current->cred;
 602
 603        kdebug("revert_creds(%p{%d,%d})", old,
 604               atomic_read(&old->usage),
 605               read_cred_subscribers(old));
 606
 607        validate_creds(old);
 608        validate_creds(override);
 609        alter_cred_subscribers(old, 1);
 610        rcu_assign_pointer(current->cred, old);
 611        alter_cred_subscribers(override, -1);
 612        put_cred(override);
 613}
 614EXPORT_SYMBOL(revert_creds);
 615
 616/*
 617 * initialise the credentials stuff
 618 */
 619void __init cred_init(void)
 620{
 621        /* allocate a slab in which we can store credentials */
 622        cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred),
 623                                     0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
 624}
 625
 626/**
 627 * prepare_kernel_cred - Prepare a set of credentials for a kernel service
 628 * @daemon: A userspace daemon to be used as a reference
 629 *
 630 * Prepare a set of credentials for a kernel service.  This can then be used to
 631 * override a task's own credentials so that work can be done on behalf of that
 632 * task that requires a different subjective context.
 633 *
 634 * @daemon is used to provide a base for the security record, but can be NULL.
 635 * If @daemon is supplied, then the security data will be derived from that;
 636 * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
 637 *
 638 * The caller may change these controls afterwards if desired.
 639 *
 640 * Returns the new credentials or NULL if out of memory.
 641 *
 642 * Does not take, and does not return holding current->cred_replace_mutex.
 643 */
 644struct cred *prepare_kernel_cred(struct task_struct *daemon)
 645{
 646#ifdef CONFIG_KEYS
 647        struct thread_group_cred *tgcred;
 648#endif
 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#ifdef CONFIG_KEYS
 657        tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
 658        if (!tgcred) {
 659                kmem_cache_free(cred_jar, new);
 660                return NULL;
 661        }
 662#endif
 663
 664        kdebug("prepare_kernel_cred() alloc %p", new);
 665
 666        if (daemon)
 667                old = get_task_cred(daemon);
 668        else
 669                old = get_cred(&init_cred);
 670
 671        validate_creds(old);
 672
 673        *new = *old;
 674        atomic_set(&new->usage, 1);
 675        set_cred_subscribers(new, 0);
 676        get_uid(new->user);
 677        get_user_ns(new->user_ns);
 678        get_group_info(new->group_info);
 679
 680#ifdef CONFIG_KEYS
 681        atomic_set(&tgcred->usage, 1);
 682        spin_lock_init(&tgcred->lock);
 683        tgcred->process_keyring = NULL;
 684        tgcred->session_keyring = NULL;
 685        new->tgcred = tgcred;
 686        new->request_key_auth = NULL;
 687        new->thread_keyring = NULL;
 688        new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
 689#endif
 690
 691#ifdef CONFIG_SECURITY
 692        new->security = NULL;
 693#endif
 694        if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
 695                goto error;
 696
 697        put_cred(old);
 698        validate_creds(new);
 699        return new;
 700
 701error:
 702        put_cred(new);
 703        put_cred(old);
 704        return NULL;
 705}
 706EXPORT_SYMBOL(prepare_kernel_cred);
 707
 708/**
 709 * set_security_override - Set the security ID in a set of credentials
 710 * @new: The credentials to alter
 711 * @secid: The LSM security ID to set
 712 *
 713 * Set the LSM security ID in a set of credentials so that the subjective
 714 * security is overridden when an alternative set of credentials is used.
 715 */
 716int set_security_override(struct cred *new, u32 secid)
 717{
 718        return security_kernel_act_as(new, secid);
 719}
 720EXPORT_SYMBOL(set_security_override);
 721
 722/**
 723 * set_security_override_from_ctx - Set the security ID in a set of credentials
 724 * @new: The credentials to alter
 725 * @secctx: The LSM security context to generate the security ID from.
 726 *
 727 * Set the LSM security ID in a set of credentials so that the subjective
 728 * security is overridden when an alternative set of credentials is used.  The
 729 * security ID is specified in string form as a security context to be
 730 * interpreted by the LSM.
 731 */
 732int set_security_override_from_ctx(struct cred *new, const char *secctx)
 733{
 734        u32 secid;
 735        int ret;
 736
 737        ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
 738        if (ret < 0)
 739                return ret;
 740
 741        return set_security_override(new, secid);
 742}
 743EXPORT_SYMBOL(set_security_override_from_ctx);
 744
 745/**
 746 * set_create_files_as - Set the LSM file create context in a set of credentials
 747 * @new: The credentials to alter
 748 * @inode: The inode to take the context from
 749 *
 750 * Change the LSM file creation context in a set of credentials to be the same
 751 * as the object context of the specified inode, so that the new inodes have
 752 * the same MAC context as that inode.
 753 */
 754int set_create_files_as(struct cred *new, struct inode *inode)
 755{
 756        new->fsuid = inode->i_uid;
 757        new->fsgid = inode->i_gid;
 758        return security_kernel_create_files_as(new, inode);
 759}
 760EXPORT_SYMBOL(set_create_files_as);
 761
 762#ifdef CONFIG_DEBUG_CREDENTIALS
 763
 764bool creds_are_invalid(const struct cred *cred)
 765{
 766        if (cred->magic != CRED_MAGIC)
 767                return true;
 768#ifdef CONFIG_SECURITY_SELINUX
 769        /*
 770         * cred->security == NULL if security_cred_alloc_blank() or
 771         * security_prepare_creds() returned an error.
 772         */
 773        if (selinux_is_enabled() && cred->security) {
 774                if ((unsigned long) cred->security < PAGE_SIZE)
 775                        return true;
 776                if ((*(u32 *)cred->security & 0xffffff00) ==
 777                    (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
 778                        return true;
 779        }
 780#endif
 781        return false;
 782}
 783EXPORT_SYMBOL(creds_are_invalid);
 784
 785/*
 786 * dump invalid credentials
 787 */
 788static void dump_invalid_creds(const struct cred *cred, const char *label,
 789                               const struct task_struct *tsk)
 790{
 791        printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
 792               label, cred,
 793               cred == &init_cred ? "[init]" : "",
 794               cred == tsk->real_cred ? "[real]" : "",
 795               cred == tsk->cred ? "[eff]" : "");
 796        printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
 797               cred->magic, cred->put_addr);
 798        printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
 799               atomic_read(&cred->usage),
 800               read_cred_subscribers(cred));
 801        printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
 802               cred->uid, cred->euid, cred->suid, cred->fsuid);
 803        printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
 804               cred->gid, cred->egid, cred->sgid, cred->fsgid);
 805#ifdef CONFIG_SECURITY
 806        printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
 807        if ((unsigned long) cred->security >= PAGE_SIZE &&
 808            (((unsigned long) cred->security & 0xffffff00) !=
 809             (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
 810                printk(KERN_ERR "CRED: ->security {%x, %x}\n",
 811                       ((u32*)cred->security)[0],
 812                       ((u32*)cred->security)[1]);
 813#endif
 814}
 815
 816/*
 817 * report use of invalid credentials
 818 */
 819void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
 820{
 821        printk(KERN_ERR "CRED: Invalid credentials\n");
 822        printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 823        dump_invalid_creds(cred, "Specified", current);
 824        BUG();
 825}
 826EXPORT_SYMBOL(__invalid_creds);
 827
 828/*
 829 * check the credentials on a process
 830 */
 831void __validate_process_creds(struct task_struct *tsk,
 832                              const char *file, unsigned line)
 833{
 834        if (tsk->cred == tsk->real_cred) {
 835                if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
 836                             creds_are_invalid(tsk->cred)))
 837                        goto invalid_creds;
 838        } else {
 839                if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
 840                             read_cred_subscribers(tsk->cred) < 1 ||
 841                             creds_are_invalid(tsk->real_cred) ||
 842                             creds_are_invalid(tsk->cred)))
 843                        goto invalid_creds;
 844        }
 845        return;
 846
 847invalid_creds:
 848        printk(KERN_ERR "CRED: Invalid process credentials\n");
 849        printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 850
 851        dump_invalid_creds(tsk->real_cred, "Real", tsk);
 852        if (tsk->cred != tsk->real_cred)
 853                dump_invalid_creds(tsk->cred, "Effective", tsk);
 854        else
 855                printk(KERN_ERR "CRED: Effective creds == Real creds\n");
 856        BUG();
 857}
 858EXPORT_SYMBOL(__validate_process_creds);
 859
 860/*
 861 * check creds for do_exit()
 862 */
 863void validate_creds_for_do_exit(struct task_struct *tsk)
 864{
 865        kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
 866               tsk->real_cred, tsk->cred,
 867               atomic_read(&tsk->cred->usage),
 868               read_cred_subscribers(tsk->cred));
 869
 870        __validate_process_creds(tsk, __FILE__, __LINE__);
 871}
 872
 873#endif /* CONFIG_DEBUG_CREDENTIALS */
 874
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