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",                                 \
  25               current->comm, current->pid, ##__VA_ARGS__)
  26#else
  27#define kdebug(FMT, ...)                                                \
  28do {                                                                    \
  29        if (0)                                                          \
  30                no_printk("[%-5.5s%5u] " FMT "\n",                      \
  31                          current->comm, current->pid, ##__VA_ARGS__);  \
  32} while (0)
  33#endif
  34
  35static struct kmem_cache *cred_jar;
  36
  37/* init to 2 - one for init_task, one to ensure it is never freed */
  38struct group_info init_groups = { .usage = ATOMIC_INIT(2) };
  39
  40/*
  41 * The initial credentials for the initial task
  42 */
  43struct cred init_cred = {
  44        .usage                  = ATOMIC_INIT(4),
  45#ifdef CONFIG_DEBUG_CREDENTIALS
  46        .subscribers            = ATOMIC_INIT(2),
  47        .magic                  = CRED_MAGIC,
  48#endif
  49        .uid                    = GLOBAL_ROOT_UID,
  50        .gid                    = GLOBAL_ROOT_GID,
  51        .suid                   = GLOBAL_ROOT_UID,
  52        .sgid                   = GLOBAL_ROOT_GID,
  53        .euid                   = GLOBAL_ROOT_UID,
  54        .egid                   = GLOBAL_ROOT_GID,
  55        .fsuid                  = GLOBAL_ROOT_UID,
  56        .fsgid                  = GLOBAL_ROOT_GID,
  57        .securebits             = SECUREBITS_DEFAULT,
  58        .cap_inheritable        = CAP_EMPTY_SET,
  59        .cap_permitted          = CAP_FULL_SET,
  60        .cap_effective          = CAP_FULL_SET,
  61        .cap_bset               = CAP_FULL_SET,
  62        .user                   = INIT_USER,
  63        .user_ns                = &init_user_ns,
  64        .group_info             = &init_groups,
  65};
  66
  67static 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
  74static 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
  83static 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 * The RCU callback to actually dispose of a set of credentials
  94 */
  95static void put_cred_rcu(struct rcu_head *rcu)
  96{
  97        struct cred *cred = container_of(rcu, struct cred, rcu);
  98
  99        kdebug("put_cred_rcu(%p)", cred);
 100
 101#ifdef CONFIG_DEBUG_CREDENTIALS
 102        if (cred->magic != CRED_MAGIC_DEAD ||
 103            atomic_read(&cred->usage) != 0 ||
 104            read_cred_subscribers(cred) != 0)
 105                panic("CRED: put_cred_rcu() sees %p with"
 106                      " mag %x, put %p, usage %d, subscr %d\n",
 107                      cred, cred->magic, cred->put_addr,
 108                      atomic_read(&cred->usage),
 109                      read_cred_subscribers(cred));
 110#else
 111        if (atomic_read(&cred->usage) != 0)
 112                panic("CRED: put_cred_rcu() sees %p with usage %d\n",
 113                      cred, atomic_read(&cred->usage));
 114#endif
 115
 116        security_cred_free(cred);
 117        key_put(cred->session_keyring);
 118        key_put(cred->process_keyring);
 119        key_put(cred->thread_keyring);
 120        key_put(cred->request_key_auth);
 121        if (cred->group_info)
 122                put_group_info(cred->group_info);
 123        free_uid(cred->user);
 124        put_user_ns(cred->user_ns);
 125        kmem_cache_free(cred_jar, cred);
 126}
 127
 128/**
 129 * __put_cred - Destroy a set of credentials
 130 * @cred: The record to release
 131 *
 132 * Destroy a set of credentials on which no references remain.
 133 */
 134void __put_cred(struct cred *cred)
 135{
 136        kdebug("__put_cred(%p{%d,%d})", cred,
 137               atomic_read(&cred->usage),
 138               read_cred_subscribers(cred));
 139
 140        BUG_ON(atomic_read(&cred->usage) != 0);
 141#ifdef CONFIG_DEBUG_CREDENTIALS
 142        BUG_ON(read_cred_subscribers(cred) != 0);
 143        cred->magic = CRED_MAGIC_DEAD;
 144        cred->put_addr = __builtin_return_address(0);
 145#endif
 146        BUG_ON(cred == current->cred);
 147        BUG_ON(cred == current->real_cred);
 148
 149        call_rcu(&cred->rcu, put_cred_rcu);
 150}
 151EXPORT_SYMBOL(__put_cred);
 152
 153/*
 154 * Clean up a task's credentials when it exits
 155 */
 156void exit_creds(struct task_struct *tsk)
 157{
 158        struct cred *cred;
 159
 160        kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
 161               atomic_read(&tsk->cred->usage),
 162               read_cred_subscribers(tsk->cred));
 163
 164        cred = (struct cred *) tsk->real_cred;
 165        tsk->real_cred = NULL;
 166        validate_creds(cred);
 167        alter_cred_subscribers(cred, -1);
 168        put_cred(cred);
 169
 170        cred = (struct cred *) tsk->cred;
 171        tsk->cred = NULL;
 172        validate_creds(cred);
 173        alter_cred_subscribers(cred, -1);
 174        put_cred(cred);
 175}
 176
 177/**
 178 * get_task_cred - Get another task's objective credentials
 179 * @task: The task to query
 180 *
 181 * Get the objective credentials of a task, pinning them so that they can't go
 182 * away.  Accessing a task's credentials directly is not permitted.
 183 *
 184 * The caller must also make sure task doesn't get deleted, either by holding a
 185 * ref on task or by holding tasklist_lock to prevent it from being unlinked.
 186 */
 187const struct cred *get_task_cred(struct task_struct *task)
 188{
 189        const struct cred *cred;
 190
 191        rcu_read_lock();
 192
 193        do {
 194                cred = __task_cred((task));
 195                BUG_ON(!cred);
 196        } while (!atomic_inc_not_zero(&((struct cred *)cred)->usage));
 197
 198        rcu_read_unlock();
 199        return cred;
 200}
 201
 202/*
 203 * Allocate blank credentials, such that the credentials can be filled in at a
 204 * later date without risk of ENOMEM.
 205 */
 206struct cred *cred_alloc_blank(void)
 207{
 208        struct cred *new;
 209
 210        new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
 211        if (!new)
 212                return NULL;
 213
 214        atomic_set(&new->usage, 1);
 215#ifdef CONFIG_DEBUG_CREDENTIALS
 216        new->magic = CRED_MAGIC;
 217#endif
 218
 219        if (security_cred_alloc_blank(new, GFP_KERNEL) < 0)
 220                goto error;
 221
 222        return new;
 223
 224error:
 225        abort_creds(new);
 226        return NULL;
 227}
 228
 229/**
 230 * prepare_creds - Prepare a new set of credentials for modification
 231 *
 232 * Prepare a new set of task credentials for modification.  A task's creds
 233 * shouldn't generally be modified directly, therefore this function is used to
 234 * prepare a new copy, which the caller then modifies and then commits by
 235 * calling commit_creds().
 236 *
 237 * Preparation involves making a copy of the objective creds for modification.
 238 *
 239 * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
 240 *
 241 * Call commit_creds() or abort_creds() to clean up.
 242 */
 243struct cred *prepare_creds(void)
 244{
 245        struct task_struct *task = current;
 246        const struct cred *old;
 247        struct cred *new;
 248
 249        validate_process_creds();
 250
 251        new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
 252        if (!new)
 253                return NULL;
 254
 255        kdebug("prepare_creds() alloc %p", new);
 256
 257        old = task->cred;
 258        memcpy(new, old, sizeof(struct cred));
 259
 260        atomic_set(&new->usage, 1);
 261        set_cred_subscribers(new, 0);
 262        get_group_info(new->group_info);
 263        get_uid(new->user);
 264        get_user_ns(new->user_ns);
 265
 266#ifdef CONFIG_KEYS
 267        key_get(new->session_keyring);
 268        key_get(new->process_keyring);
 269        key_get(new->thread_keyring);
 270        key_get(new->request_key_auth);
 271#endif
 272
 273#ifdef CONFIG_SECURITY
 274        new->security = NULL;
 275#endif
 276
 277        if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
 278                goto error;
 279        validate_creds(new);
 280        return new;
 281
 282error:
 283        abort_creds(new);
 284        return NULL;
 285}
 286EXPORT_SYMBOL(prepare_creds);
 287
 288/*
 289 * Prepare credentials for current to perform an execve()
 290 * - The caller must hold ->cred_guard_mutex
 291 */
 292struct cred *prepare_exec_creds(void)
 293{
 294        struct cred *new;
 295
 296        new = prepare_creds();
 297        if (!new)
 298                return new;
 299
 300#ifdef CONFIG_KEYS
 301        /* newly exec'd tasks don't get a thread keyring */
 302        key_put(new->thread_keyring);
 303        new->thread_keyring = NULL;
 304
 305        /* inherit the session keyring; new process keyring */
 306        key_put(new->process_keyring);
 307        new->process_keyring = NULL;
 308#endif
 309
 310        return new;
 311}
 312
 313/*
 314 * Copy credentials for the new process created by fork()
 315 *
 316 * We share if we can, but under some circumstances we have to generate a new
 317 * set.
 318 *
 319 * The new process gets the current process's subjective credentials as its
 320 * objective and subjective credentials
 321 */
 322int copy_creds(struct task_struct *p, unsigned long clone_flags)
 323{
 324        struct cred *new;
 325        int ret;
 326
 327        if (
 328#ifdef CONFIG_KEYS
 329                !p->cred->thread_keyring &&
 330#endif
 331                clone_flags & CLONE_THREAD
 332            ) {
 333                p->real_cred = get_cred(p->cred);
 334                get_cred(p->cred);
 335                alter_cred_subscribers(p->cred, 2);
 336                kdebug("share_creds(%p{%d,%d})",
 337                       p->cred, atomic_read(&p->cred->usage),
 338                       read_cred_subscribers(p->cred));
 339                atomic_inc(&p->cred->user->processes);
 340                return 0;
 341        }
 342
 343        new = prepare_creds();
 344        if (!new)
 345                return -ENOMEM;
 346
 347        if (clone_flags & CLONE_NEWUSER) {
 348                ret = create_user_ns(new);
 349                if (ret < 0)
 350                        goto error_put;
 351        }
 352
 353#ifdef CONFIG_KEYS
 354        /* new threads get their own thread keyrings if their parent already
 355         * had one */
 356        if (new->thread_keyring) {
 357                key_put(new->thread_keyring);
 358                new->thread_keyring = NULL;
 359                if (clone_flags & CLONE_THREAD)
 360                        install_thread_keyring_to_cred(new);
 361        }
 362
 363        /* The process keyring is only shared between the threads in a process;
 364         * anything outside of those threads doesn't inherit.
 365         */
 366        if (!(clone_flags & CLONE_THREAD)) {
 367                key_put(new->process_keyring);
 368                new->process_keyring = NULL;
 369        }
 370#endif
 371
 372        atomic_inc(&new->user->processes);
 373        p->cred = p->real_cred = get_cred(new);
 374        alter_cred_subscribers(new, 2);
 375        validate_creds(new);
 376        return 0;
 377
 378error_put:
 379        put_cred(new);
 380        return ret;
 381}
 382
 383static bool cred_cap_issubset(const struct cred *set, const struct cred *subset)
 384{
 385        const struct user_namespace *set_ns = set->user_ns;
 386        const struct user_namespace *subset_ns = subset->user_ns;
 387
 388        /* If the two credentials are in the same user namespace see if
 389         * the capabilities of subset are a subset of set.
 390         */
 391        if (set_ns == subset_ns)
 392                return cap_issubset(subset->cap_permitted, set->cap_permitted);
 393
 394        /* The credentials are in a different user namespaces
 395         * therefore one is a subset of the other only if a set is an
 396         * ancestor of subset and set->euid is owner of subset or one
 397         * of subsets ancestors.
 398         */
 399        for (;subset_ns != &init_user_ns; subset_ns = subset_ns->parent) {
 400                if ((set_ns == subset_ns->parent)  &&
 401                    uid_eq(subset_ns->owner, set->euid))
 402                        return true;
 403        }
 404
 405        return false;
 406}
 407
 408/**
 409 * commit_creds - Install new credentials upon the current task
 410 * @new: The credentials to be assigned
 411 *
 412 * Install a new set of credentials to the current task, using RCU to replace
 413 * the old set.  Both the objective and the subjective credentials pointers are
 414 * updated.  This function may not be called if the subjective credentials are
 415 * in an overridden state.
 416 *
 417 * This function eats the caller's reference to the new credentials.
 418 *
 419 * Always returns 0 thus allowing this function to be tail-called at the end
 420 * of, say, sys_setgid().
 421 */
 422int commit_creds(struct cred *new)
 423{
 424        struct task_struct *task = current;
 425        const struct cred *old = task->real_cred;
 426
 427        kdebug("commit_creds(%p{%d,%d})", new,
 428               atomic_read(&new->usage),
 429               read_cred_subscribers(new));
 430
 431        BUG_ON(task->cred != old);
 432#ifdef CONFIG_DEBUG_CREDENTIALS
 433        BUG_ON(read_cred_subscribers(old) < 2);
 434        validate_creds(old);
 435        validate_creds(new);
 436#endif
 437        BUG_ON(atomic_read(&new->usage) < 1);
 438
 439        get_cred(new); /* we will require a ref for the subj creds too */
 440
 441        /* dumpability changes */
 442        if (!uid_eq(old->euid, new->euid) ||
 443            !gid_eq(old->egid, new->egid) ||
 444            !uid_eq(old->fsuid, new->fsuid) ||
 445            !gid_eq(old->fsgid, new->fsgid) ||
 446            !cred_cap_issubset(old, new)) {
 447                if (task->mm)
 448                        set_dumpable(task->mm, suid_dumpable);
 449                task->pdeath_signal = 0;
 450                smp_wmb();
 451        }
 452
 453        /* alter the thread keyring */
 454        if (!uid_eq(new->fsuid, old->fsuid))
 455                key_fsuid_changed(task);
 456        if (!gid_eq(new->fsgid, old->fsgid))
 457                key_fsgid_changed(task);
 458
 459        /* do it
 460         * RLIMIT_NPROC limits on user->processes have already been checked
 461         * in set_user().
 462         */
 463        alter_cred_subscribers(new, 2);
 464        if (new->user != old->user)
 465                atomic_inc(&new->user->processes);
 466        rcu_assign_pointer(task->real_cred, new);
 467        rcu_assign_pointer(task->cred, new);
 468        if (new->user != old->user)
 469                atomic_dec(&old->user->processes);
 470        alter_cred_subscribers(old, -2);
 471
 472        /* send notifications */
 473        if (!uid_eq(new->uid,   old->uid)  ||
 474            !uid_eq(new->euid,  old->euid) ||
 475            !uid_eq(new->suid,  old->suid) ||
 476            !uid_eq(new->fsuid, old->fsuid))
 477                proc_id_connector(task, PROC_EVENT_UID);
 478
 479        if (!gid_eq(new->gid,   old->gid)  ||
 480            !gid_eq(new->egid,  old->egid) ||
 481            !gid_eq(new->sgid,  old->sgid) ||
 482            !gid_eq(new->fsgid, old->fsgid))
 483                proc_id_connector(task, PROC_EVENT_GID);
 484
 485        /* release the old obj and subj refs both */
 486        put_cred(old);
 487        put_cred(old);
 488        return 0;
 489}
 490EXPORT_SYMBOL(commit_creds);
 491
 492/**
 493 * abort_creds - Discard a set of credentials and unlock the current task
 494 * @new: The credentials that were going to be applied
 495 *
 496 * Discard a set of credentials that were under construction and unlock the
 497 * current task.
 498 */
 499void abort_creds(struct cred *new)
 500{
 501        kdebug("abort_creds(%p{%d,%d})", new,
 502               atomic_read(&new->usage),
 503               read_cred_subscribers(new));
 504
 505#ifdef CONFIG_DEBUG_CREDENTIALS
 506        BUG_ON(read_cred_subscribers(new) != 0);
 507#endif
 508        BUG_ON(atomic_read(&new->usage) < 1);
 509        put_cred(new);
 510}
 511EXPORT_SYMBOL(abort_creds);
 512
 513/**
 514 * override_creds - Override the current process's subjective credentials
 515 * @new: The credentials to be assigned
 516 *
 517 * Install a set of temporary override subjective credentials on the current
 518 * process, returning the old set for later reversion.
 519 */
 520const struct cred *override_creds(const struct cred *new)
 521{
 522        const struct cred *old = current->cred;
 523
 524        kdebug("override_creds(%p{%d,%d})", new,
 525               atomic_read(&new->usage),
 526               read_cred_subscribers(new));
 527
 528        validate_creds(old);
 529        validate_creds(new);
 530        get_cred(new);
 531        alter_cred_subscribers(new, 1);
 532        rcu_assign_pointer(current->cred, new);
 533        alter_cred_subscribers(old, -1);
 534
 535        kdebug("override_creds() = %p{%d,%d}", old,
 536               atomic_read(&old->usage),
 537               read_cred_subscribers(old));
 538        return old;
 539}
 540EXPORT_SYMBOL(override_creds);
 541
 542/**
 543 * revert_creds - Revert a temporary subjective credentials override
 544 * @old: The credentials to be restored
 545 *
 546 * Revert a temporary set of override subjective credentials to an old set,
 547 * discarding the override set.
 548 */
 549void revert_creds(const struct cred *old)
 550{
 551        const struct cred *override = current->cred;
 552
 553        kdebug("revert_creds(%p{%d,%d})", old,
 554               atomic_read(&old->usage),
 555               read_cred_subscribers(old));
 556
 557        validate_creds(old);
 558        validate_creds(override);
 559        alter_cred_subscribers(old, 1);
 560        rcu_assign_pointer(current->cred, old);
 561        alter_cred_subscribers(override, -1);
 562        put_cred(override);
 563}
 564EXPORT_SYMBOL(revert_creds);
 565
 566/*
 567 * initialise the credentials stuff
 568 */
 569void __init cred_init(void)
 570{
 571        /* allocate a slab in which we can store credentials */
 572        cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred), 0,
 573                        SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL);
 574}
 575
 576/**
 577 * prepare_kernel_cred - Prepare a set of credentials for a kernel service
 578 * @daemon: A userspace daemon to be used as a reference
 579 *
 580 * Prepare a set of credentials for a kernel service.  This can then be used to
 581 * override a task's own credentials so that work can be done on behalf of that
 582 * task that requires a different subjective context.
 583 *
 584 * @daemon is used to provide a base for the security record, but can be NULL.
 585 * If @daemon is supplied, then the security data will be derived from that;
 586 * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
 587 *
 588 * The caller may change these controls afterwards if desired.
 589 *
 590 * Returns the new credentials or NULL if out of memory.
 591 *
 592 * Does not take, and does not return holding current->cred_replace_mutex.
 593 */
 594struct cred *prepare_kernel_cred(struct task_struct *daemon)
 595{
 596        const struct cred *old;
 597        struct cred *new;
 598
 599        new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
 600        if (!new)
 601                return NULL;
 602
 603        kdebug("prepare_kernel_cred() alloc %p", new);
 604
 605        if (daemon)
 606                old = get_task_cred(daemon);
 607        else
 608                old = get_cred(&init_cred);
 609
 610        validate_creds(old);
 611
 612        *new = *old;
 613        atomic_set(&new->usage, 1);
 614        set_cred_subscribers(new, 0);
 615        get_uid(new->user);
 616        get_user_ns(new->user_ns);
 617        get_group_info(new->group_info);
 618
 619#ifdef CONFIG_KEYS
 620        new->session_keyring = NULL;
 621        new->process_keyring = NULL;
 622        new->thread_keyring = NULL;
 623        new->request_key_auth = NULL;
 624        new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
 625#endif
 626
 627#ifdef CONFIG_SECURITY
 628        new->security = NULL;
 629#endif
 630        if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
 631                goto error;
 632
 633        put_cred(old);
 634        validate_creds(new);
 635        return new;
 636
 637error:
 638        put_cred(new);
 639        put_cred(old);
 640        return NULL;
 641}
 642EXPORT_SYMBOL(prepare_kernel_cred);
 643
 644/**
 645 * set_security_override - Set the security ID in a set of credentials
 646 * @new: The credentials to alter
 647 * @secid: The LSM security ID to set
 648 *
 649 * Set the LSM security ID in a set of credentials so that the subjective
 650 * security is overridden when an alternative set of credentials is used.
 651 */
 652int set_security_override(struct cred *new, u32 secid)
 653{
 654        return security_kernel_act_as(new, secid);
 655}
 656EXPORT_SYMBOL(set_security_override);
 657
 658/**
 659 * set_security_override_from_ctx - Set the security ID in a set of credentials
 660 * @new: The credentials to alter
 661 * @secctx: The LSM security context to generate the security ID from.
 662 *
 663 * Set the LSM security ID in a set of credentials so that the subjective
 664 * security is overridden when an alternative set of credentials is used.  The
 665 * security ID is specified in string form as a security context to be
 666 * interpreted by the LSM.
 667 */
 668int set_security_override_from_ctx(struct cred *new, const char *secctx)
 669{
 670        u32 secid;
 671        int ret;
 672
 673        ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
 674        if (ret < 0)
 675                return ret;
 676
 677        return set_security_override(new, secid);
 678}
 679EXPORT_SYMBOL(set_security_override_from_ctx);
 680
 681/**
 682 * set_create_files_as - Set the LSM file create context in a set of credentials
 683 * @new: The credentials to alter
 684 * @inode: The inode to take the context from
 685 *
 686 * Change the LSM file creation context in a set of credentials to be the same
 687 * as the object context of the specified inode, so that the new inodes have
 688 * the same MAC context as that inode.
 689 */
 690int set_create_files_as(struct cred *new, struct inode *inode)
 691{
 692        if (!uid_valid(inode->i_uid) || !gid_valid(inode->i_gid))
 693                return -EINVAL;
 694        new->fsuid = inode->i_uid;
 695        new->fsgid = inode->i_gid;
 696        return security_kernel_create_files_as(new, inode);
 697}
 698EXPORT_SYMBOL(set_create_files_as);
 699
 700#ifdef CONFIG_DEBUG_CREDENTIALS
 701
 702bool creds_are_invalid(const struct cred *cred)
 703{
 704        if (cred->magic != CRED_MAGIC)
 705                return true;
 706#ifdef CONFIG_SECURITY_SELINUX
 707        /*
 708         * cred->security == NULL if security_cred_alloc_blank() or
 709         * security_prepare_creds() returned an error.
 710         */
 711        if (selinux_is_enabled() && cred->security) {
 712                if ((unsigned long) cred->security < PAGE_SIZE)
 713                        return true;
 714                if ((*(u32 *)cred->security & 0xffffff00) ==
 715                    (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
 716                        return true;
 717        }
 718#endif
 719        return false;
 720}
 721EXPORT_SYMBOL(creds_are_invalid);
 722
 723/*
 724 * dump invalid credentials
 725 */
 726static void dump_invalid_creds(const struct cred *cred, const char *label,
 727                               const struct task_struct *tsk)
 728{
 729        printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
 730               label, cred,
 731               cred == &init_cred ? "[init]" : "",
 732               cred == tsk->real_cred ? "[real]" : "",
 733               cred == tsk->cred ? "[eff]" : "");
 734        printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
 735               cred->magic, cred->put_addr);
 736        printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
 737               atomic_read(&cred->usage),
 738               read_cred_subscribers(cred));
 739        printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
 740                from_kuid_munged(&init_user_ns, cred->uid),
 741                from_kuid_munged(&init_user_ns, cred->euid),
 742                from_kuid_munged(&init_user_ns, cred->suid),
 743                from_kuid_munged(&init_user_ns, cred->fsuid));
 744        printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
 745                from_kgid_munged(&init_user_ns, cred->gid),
 746                from_kgid_munged(&init_user_ns, cred->egid),
 747                from_kgid_munged(&init_user_ns, cred->sgid),
 748                from_kgid_munged(&init_user_ns, cred->fsgid));
 749#ifdef CONFIG_SECURITY
 750        printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
 751        if ((unsigned long) cred->security >= PAGE_SIZE &&
 752            (((unsigned long) cred->security & 0xffffff00) !=
 753             (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
 754                printk(KERN_ERR "CRED: ->security {%x, %x}\n",
 755                       ((u32*)cred->security)[0],
 756                       ((u32*)cred->security)[1]);
 757#endif
 758}
 759
 760/*
 761 * report use of invalid credentials
 762 */
 763void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
 764{
 765        printk(KERN_ERR "CRED: Invalid credentials\n");
 766        printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 767        dump_invalid_creds(cred, "Specified", current);
 768        BUG();
 769}
 770EXPORT_SYMBOL(__invalid_creds);
 771
 772/*
 773 * check the credentials on a process
 774 */
 775void __validate_process_creds(struct task_struct *tsk,
 776                              const char *file, unsigned line)
 777{
 778        if (tsk->cred == tsk->real_cred) {
 779                if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
 780                             creds_are_invalid(tsk->cred)))
 781                        goto invalid_creds;
 782        } else {
 783                if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
 784                             read_cred_subscribers(tsk->cred) < 1 ||
 785                             creds_are_invalid(tsk->real_cred) ||
 786                             creds_are_invalid(tsk->cred)))
 787                        goto invalid_creds;
 788        }
 789        return;
 790
 791invalid_creds:
 792        printk(KERN_ERR "CRED: Invalid process credentials\n");
 793        printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 794
 795        dump_invalid_creds(tsk->real_cred, "Real", tsk);
 796        if (tsk->cred != tsk->real_cred)
 797                dump_invalid_creds(tsk->cred, "Effective", tsk);
 798        else
 799                printk(KERN_ERR "CRED: Effective creds == Real creds\n");
 800        BUG();
 801}
 802EXPORT_SYMBOL(__validate_process_creds);
 803
 804/*
 805 * check creds for do_exit()
 806 */
 807void validate_creds_for_do_exit(struct task_struct *tsk)
 808{
 809        kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
 810               tsk->real_cred, tsk->cred,
 811               atomic_read(&tsk->cred->usage),
 812               read_cred_subscribers(tsk->cred));
 813
 814        __validate_process_creds(tsk, __FILE__, __LINE__);
 815}
 816
 817#endif /* CONFIG_DEBUG_CREDENTIALS */
 818