linux/kernel/cred.c
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   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/* Task credentials management - see Documentation/security/credentials.rst
   3 *
   4 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
   5 * Written by David Howells (dhowells@redhat.com)
   6 */
   7#include <linux/export.h>
   8#include <linux/cred.h>
   9#include <linux/slab.h>
  10#include <linux/sched.h>
  11#include <linux/sched/coredump.h>
  12#include <linux/key.h>
  13#include <linux/keyctl.h>
  14#include <linux/init_task.h>
  15#include <linux/security.h>
  16#include <linux/binfmts.h>
  17#include <linux/cn_proc.h>
  18#include <linux/uidgid.h>
  19
  20#if 0
  21#define kdebug(FMT, ...)                                                \
  22        printk("[%-5.5s%5u] " FMT "\n",                                 \
  23               current->comm, current->pid, ##__VA_ARGS__)
  24#else
  25#define kdebug(FMT, ...)                                                \
  26do {                                                                    \
  27        if (0)                                                          \
  28                no_printk("[%-5.5s%5u] " FMT "\n",                      \
  29                          current->comm, current->pid, ##__VA_ARGS__);  \
  30} while (0)
  31#endif
  32
  33static struct kmem_cache *cred_jar;
  34
  35/* init to 2 - one for init_task, one to ensure it is never freed */
  36static struct group_info init_groups = { .usage = ATOMIC_INIT(2) };
  37
  38/*
  39 * The initial credentials for the initial task
  40 */
  41struct cred init_cred = {
  42        .usage                  = ATOMIC_INIT(4),
  43#ifdef CONFIG_DEBUG_CREDENTIALS
  44        .subscribers            = ATOMIC_INIT(2),
  45        .magic                  = CRED_MAGIC,
  46#endif
  47        .uid                    = GLOBAL_ROOT_UID,
  48        .gid                    = GLOBAL_ROOT_GID,
  49        .suid                   = GLOBAL_ROOT_UID,
  50        .sgid                   = GLOBAL_ROOT_GID,
  51        .euid                   = GLOBAL_ROOT_UID,
  52        .egid                   = GLOBAL_ROOT_GID,
  53        .fsuid                  = GLOBAL_ROOT_UID,
  54        .fsgid                  = GLOBAL_ROOT_GID,
  55        .securebits             = SECUREBITS_DEFAULT,
  56        .cap_inheritable        = CAP_EMPTY_SET,
  57        .cap_permitted          = CAP_FULL_SET,
  58        .cap_effective          = CAP_FULL_SET,
  59        .cap_bset               = CAP_FULL_SET,
  60        .user                   = INIT_USER,
  61        .user_ns                = &init_user_ns,
  62        .group_info             = &init_groups,
  63};
  64
  65static inline void set_cred_subscribers(struct cred *cred, int n)
  66{
  67#ifdef CONFIG_DEBUG_CREDENTIALS
  68        atomic_set(&cred->subscribers, n);
  69#endif
  70}
  71
  72static inline int read_cred_subscribers(const struct cred *cred)
  73{
  74#ifdef CONFIG_DEBUG_CREDENTIALS
  75        return atomic_read(&cred->subscribers);
  76#else
  77        return 0;
  78#endif
  79}
  80
  81static inline void alter_cred_subscribers(const struct cred *_cred, int n)
  82{
  83#ifdef CONFIG_DEBUG_CREDENTIALS
  84        struct cred *cred = (struct cred *) _cred;
  85
  86        atomic_add(n, &cred->subscribers);
  87#endif
  88}
  89
  90/*
  91 * The RCU callback to actually dispose of a set of credentials
  92 */
  93static void put_cred_rcu(struct rcu_head *rcu)
  94{
  95        struct cred *cred = container_of(rcu, struct cred, rcu);
  96
  97        kdebug("put_cred_rcu(%p)", cred);
  98
  99#ifdef CONFIG_DEBUG_CREDENTIALS
 100        if (cred->magic != CRED_MAGIC_DEAD ||
 101            atomic_read(&cred->usage) != 0 ||
 102            read_cred_subscribers(cred) != 0)
 103                panic("CRED: put_cred_rcu() sees %p with"
 104                      " mag %x, put %p, usage %d, subscr %d\n",
 105                      cred, cred->magic, cred->put_addr,
 106                      atomic_read(&cred->usage),
 107                      read_cred_subscribers(cred));
 108#else
 109        if (atomic_read(&cred->usage) != 0)
 110                panic("CRED: put_cred_rcu() sees %p with usage %d\n",
 111                      cred, atomic_read(&cred->usage));
 112#endif
 113
 114        security_cred_free(cred);
 115        key_put(cred->session_keyring);
 116        key_put(cred->process_keyring);
 117        key_put(cred->thread_keyring);
 118        key_put(cred->request_key_auth);
 119        if (cred->group_info)
 120                put_group_info(cred->group_info);
 121        free_uid(cred->user);
 122        put_user_ns(cred->user_ns);
 123        kmem_cache_free(cred_jar, cred);
 124}
 125
 126/**
 127 * __put_cred - Destroy a set of credentials
 128 * @cred: The record to release
 129 *
 130 * Destroy a set of credentials on which no references remain.
 131 */
 132void __put_cred(struct cred *cred)
 133{
 134        kdebug("__put_cred(%p{%d,%d})", cred,
 135               atomic_read(&cred->usage),
 136               read_cred_subscribers(cred));
 137
 138        BUG_ON(atomic_read(&cred->usage) != 0);
 139#ifdef CONFIG_DEBUG_CREDENTIALS
 140        BUG_ON(read_cred_subscribers(cred) != 0);
 141        cred->magic = CRED_MAGIC_DEAD;
 142        cred->put_addr = __builtin_return_address(0);
 143#endif
 144        BUG_ON(cred == current->cred);
 145        BUG_ON(cred == current->real_cred);
 146
 147        if (cred->non_rcu)
 148                put_cred_rcu(&cred->rcu);
 149        else
 150                call_rcu(&cred->rcu, put_cred_rcu);
 151}
 152EXPORT_SYMBOL(__put_cred);
 153
 154/*
 155 * Clean up a task's credentials when it exits
 156 */
 157void exit_creds(struct task_struct *tsk)
 158{
 159        struct cred *cred;
 160
 161        kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
 162               atomic_read(&tsk->cred->usage),
 163               read_cred_subscribers(tsk->cred));
 164
 165        cred = (struct cred *) tsk->real_cred;
 166        tsk->real_cred = NULL;
 167        validate_creds(cred);
 168        alter_cred_subscribers(cred, -1);
 169        put_cred(cred);
 170
 171        cred = (struct cred *) tsk->cred;
 172        tsk->cred = NULL;
 173        validate_creds(cred);
 174        alter_cred_subscribers(cred, -1);
 175        put_cred(cred);
 176
 177#ifdef CONFIG_KEYS_REQUEST_CACHE
 178        key_put(tsk->cached_requested_key);
 179        tsk->cached_requested_key = NULL;
 180#endif
 181}
 182
 183/**
 184 * get_task_cred - Get another task's objective credentials
 185 * @task: The task to query
 186 *
 187 * Get the objective credentials of a task, pinning them so that they can't go
 188 * away.  Accessing a task's credentials directly is not permitted.
 189 *
 190 * The caller must also make sure task doesn't get deleted, either by holding a
 191 * ref on task or by holding tasklist_lock to prevent it from being unlinked.
 192 */
 193const struct cred *get_task_cred(struct task_struct *task)
 194{
 195        const struct cred *cred;
 196
 197        rcu_read_lock();
 198
 199        do {
 200                cred = __task_cred((task));
 201                BUG_ON(!cred);
 202        } while (!get_cred_rcu(cred));
 203
 204        rcu_read_unlock();
 205        return cred;
 206}
 207EXPORT_SYMBOL(get_task_cred);
 208
 209/*
 210 * Allocate blank credentials, such that the credentials can be filled in at a
 211 * later date without risk of ENOMEM.
 212 */
 213struct cred *cred_alloc_blank(void)
 214{
 215        struct cred *new;
 216
 217        new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
 218        if (!new)
 219                return NULL;
 220
 221        atomic_set(&new->usage, 1);
 222#ifdef CONFIG_DEBUG_CREDENTIALS
 223        new->magic = CRED_MAGIC;
 224#endif
 225
 226        if (security_cred_alloc_blank(new, GFP_KERNEL_ACCOUNT) < 0)
 227                goto error;
 228
 229        return new;
 230
 231error:
 232        abort_creds(new);
 233        return NULL;
 234}
 235
 236/**
 237 * prepare_creds - Prepare a new set of credentials for modification
 238 *
 239 * Prepare a new set of task credentials for modification.  A task's creds
 240 * shouldn't generally be modified directly, therefore this function is used to
 241 * prepare a new copy, which the caller then modifies and then commits by
 242 * calling commit_creds().
 243 *
 244 * Preparation involves making a copy of the objective creds for modification.
 245 *
 246 * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
 247 *
 248 * Call commit_creds() or abort_creds() to clean up.
 249 */
 250struct cred *prepare_creds(void)
 251{
 252        struct task_struct *task = current;
 253        const struct cred *old;
 254        struct cred *new;
 255
 256        validate_process_creds();
 257
 258        new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
 259        if (!new)
 260                return NULL;
 261
 262        kdebug("prepare_creds() alloc %p", new);
 263
 264        old = task->cred;
 265        memcpy(new, old, sizeof(struct cred));
 266
 267        new->non_rcu = 0;
 268        atomic_set(&new->usage, 1);
 269        set_cred_subscribers(new, 0);
 270        get_group_info(new->group_info);
 271        get_uid(new->user);
 272        get_user_ns(new->user_ns);
 273
 274#ifdef CONFIG_KEYS
 275        key_get(new->session_keyring);
 276        key_get(new->process_keyring);
 277        key_get(new->thread_keyring);
 278        key_get(new->request_key_auth);
 279#endif
 280
 281#ifdef CONFIG_SECURITY
 282        new->security = NULL;
 283#endif
 284
 285        if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)
 286                goto error;
 287        validate_creds(new);
 288        return new;
 289
 290error:
 291        abort_creds(new);
 292        return NULL;
 293}
 294EXPORT_SYMBOL(prepare_creds);
 295
 296/*
 297 * Prepare credentials for current to perform an execve()
 298 * - The caller must hold ->cred_guard_mutex
 299 */
 300struct cred *prepare_exec_creds(void)
 301{
 302        struct cred *new;
 303
 304        new = prepare_creds();
 305        if (!new)
 306                return new;
 307
 308#ifdef CONFIG_KEYS
 309        /* newly exec'd tasks don't get a thread keyring */
 310        key_put(new->thread_keyring);
 311        new->thread_keyring = NULL;
 312
 313        /* inherit the session keyring; new process keyring */
 314        key_put(new->process_keyring);
 315        new->process_keyring = NULL;
 316#endif
 317
 318        new->suid = new->fsuid = new->euid;
 319        new->sgid = new->fsgid = new->egid;
 320
 321        return new;
 322}
 323
 324/*
 325 * Copy credentials for the new process created by fork()
 326 *
 327 * We share if we can, but under some circumstances we have to generate a new
 328 * set.
 329 *
 330 * The new process gets the current process's subjective credentials as its
 331 * objective and subjective credentials
 332 */
 333int copy_creds(struct task_struct *p, unsigned long clone_flags)
 334{
 335        struct cred *new;
 336        int ret;
 337
 338#ifdef CONFIG_KEYS_REQUEST_CACHE
 339        p->cached_requested_key = NULL;
 340#endif
 341
 342        if (
 343#ifdef CONFIG_KEYS
 344                !p->cred->thread_keyring &&
 345#endif
 346                clone_flags & CLONE_THREAD
 347            ) {
 348                p->real_cred = get_cred(p->cred);
 349                get_cred(p->cred);
 350                alter_cred_subscribers(p->cred, 2);
 351                kdebug("share_creds(%p{%d,%d})",
 352                       p->cred, atomic_read(&p->cred->usage),
 353                       read_cred_subscribers(p->cred));
 354                atomic_inc(&p->cred->user->processes);
 355                return 0;
 356        }
 357
 358        new = prepare_creds();
 359        if (!new)
 360                return -ENOMEM;
 361
 362        if (clone_flags & CLONE_NEWUSER) {
 363                ret = create_user_ns(new);
 364                if (ret < 0)
 365                        goto error_put;
 366        }
 367
 368#ifdef CONFIG_KEYS
 369        /* new threads get their own thread keyrings if their parent already
 370         * had one */
 371        if (new->thread_keyring) {
 372                key_put(new->thread_keyring);
 373                new->thread_keyring = NULL;
 374                if (clone_flags & CLONE_THREAD)
 375                        install_thread_keyring_to_cred(new);
 376        }
 377
 378        /* The process keyring is only shared between the threads in a process;
 379         * anything outside of those threads doesn't inherit.
 380         */
 381        if (!(clone_flags & CLONE_THREAD)) {
 382                key_put(new->process_keyring);
 383                new->process_keyring = NULL;
 384        }
 385#endif
 386
 387        atomic_inc(&new->user->processes);
 388        p->cred = p->real_cred = get_cred(new);
 389        alter_cred_subscribers(new, 2);
 390        validate_creds(new);
 391        return 0;
 392
 393error_put:
 394        put_cred(new);
 395        return ret;
 396}
 397
 398static bool cred_cap_issubset(const struct cred *set, const struct cred *subset)
 399{
 400        const struct user_namespace *set_ns = set->user_ns;
 401        const struct user_namespace *subset_ns = subset->user_ns;
 402
 403        /* If the two credentials are in the same user namespace see if
 404         * the capabilities of subset are a subset of set.
 405         */
 406        if (set_ns == subset_ns)
 407                return cap_issubset(subset->cap_permitted, set->cap_permitted);
 408
 409        /* The credentials are in a different user namespaces
 410         * therefore one is a subset of the other only if a set is an
 411         * ancestor of subset and set->euid is owner of subset or one
 412         * of subsets ancestors.
 413         */
 414        for (;subset_ns != &init_user_ns; subset_ns = subset_ns->parent) {
 415                if ((set_ns == subset_ns->parent)  &&
 416                    uid_eq(subset_ns->owner, set->euid))
 417                        return true;
 418        }
 419
 420        return false;
 421}
 422
 423/**
 424 * commit_creds - Install new credentials upon the current task
 425 * @new: The credentials to be assigned
 426 *
 427 * Install a new set of credentials to the current task, using RCU to replace
 428 * the old set.  Both the objective and the subjective credentials pointers are
 429 * updated.  This function may not be called if the subjective credentials are
 430 * in an overridden state.
 431 *
 432 * This function eats the caller's reference to the new credentials.
 433 *
 434 * Always returns 0 thus allowing this function to be tail-called at the end
 435 * of, say, sys_setgid().
 436 */
 437int commit_creds(struct cred *new)
 438{
 439        struct task_struct *task = current;
 440        const struct cred *old = task->real_cred;
 441
 442        kdebug("commit_creds(%p{%d,%d})", new,
 443               atomic_read(&new->usage),
 444               read_cred_subscribers(new));
 445
 446        BUG_ON(task->cred != old);
 447#ifdef CONFIG_DEBUG_CREDENTIALS
 448        BUG_ON(read_cred_subscribers(old) < 2);
 449        validate_creds(old);
 450        validate_creds(new);
 451#endif
 452        BUG_ON(atomic_read(&new->usage) < 1);
 453
 454        get_cred(new); /* we will require a ref for the subj creds too */
 455
 456        /* dumpability changes */
 457        if (!uid_eq(old->euid, new->euid) ||
 458            !gid_eq(old->egid, new->egid) ||
 459            !uid_eq(old->fsuid, new->fsuid) ||
 460            !gid_eq(old->fsgid, new->fsgid) ||
 461            !cred_cap_issubset(old, new)) {
 462                if (task->mm)
 463                        set_dumpable(task->mm, suid_dumpable);
 464                task->pdeath_signal = 0;
 465                /*
 466                 * If a task drops privileges and becomes nondumpable,
 467                 * the dumpability change must become visible before
 468                 * the credential change; otherwise, a __ptrace_may_access()
 469                 * racing with this change may be able to attach to a task it
 470                 * shouldn't be able to attach to (as if the task had dropped
 471                 * privileges without becoming nondumpable).
 472                 * Pairs with a read barrier in __ptrace_may_access().
 473                 */
 474                smp_wmb();
 475        }
 476
 477        /* alter the thread keyring */
 478        if (!uid_eq(new->fsuid, old->fsuid))
 479                key_fsuid_changed(new);
 480        if (!gid_eq(new->fsgid, old->fsgid))
 481                key_fsgid_changed(new);
 482
 483        /* do it
 484         * RLIMIT_NPROC limits on user->processes have already been checked
 485         * in set_user().
 486         */
 487        alter_cred_subscribers(new, 2);
 488        if (new->user != old->user)
 489                atomic_inc(&new->user->processes);
 490        rcu_assign_pointer(task->real_cred, new);
 491        rcu_assign_pointer(task->cred, new);
 492        if (new->user != old->user)
 493                atomic_dec(&old->user->processes);
 494        alter_cred_subscribers(old, -2);
 495
 496        /* send notifications */
 497        if (!uid_eq(new->uid,   old->uid)  ||
 498            !uid_eq(new->euid,  old->euid) ||
 499            !uid_eq(new->suid,  old->suid) ||
 500            !uid_eq(new->fsuid, old->fsuid))
 501                proc_id_connector(task, PROC_EVENT_UID);
 502
 503        if (!gid_eq(new->gid,   old->gid)  ||
 504            !gid_eq(new->egid,  old->egid) ||
 505            !gid_eq(new->sgid,  old->sgid) ||
 506            !gid_eq(new->fsgid, old->fsgid))
 507                proc_id_connector(task, PROC_EVENT_GID);
 508
 509        /* release the old obj and subj refs both */
 510        put_cred(old);
 511        put_cred(old);
 512        return 0;
 513}
 514EXPORT_SYMBOL(commit_creds);
 515
 516/**
 517 * abort_creds - Discard a set of credentials and unlock the current task
 518 * @new: The credentials that were going to be applied
 519 *
 520 * Discard a set of credentials that were under construction and unlock the
 521 * current task.
 522 */
 523void abort_creds(struct cred *new)
 524{
 525        kdebug("abort_creds(%p{%d,%d})", new,
 526               atomic_read(&new->usage),
 527               read_cred_subscribers(new));
 528
 529#ifdef CONFIG_DEBUG_CREDENTIALS
 530        BUG_ON(read_cred_subscribers(new) != 0);
 531#endif
 532        BUG_ON(atomic_read(&new->usage) < 1);
 533        put_cred(new);
 534}
 535EXPORT_SYMBOL(abort_creds);
 536
 537/**
 538 * override_creds - Override the current process's subjective credentials
 539 * @new: The credentials to be assigned
 540 *
 541 * Install a set of temporary override subjective credentials on the current
 542 * process, returning the old set for later reversion.
 543 */
 544const struct cred *override_creds(const struct cred *new)
 545{
 546        const struct cred *old = current->cred;
 547
 548        kdebug("override_creds(%p{%d,%d})", new,
 549               atomic_read(&new->usage),
 550               read_cred_subscribers(new));
 551
 552        validate_creds(old);
 553        validate_creds(new);
 554
 555        /*
 556         * NOTE! This uses 'get_new_cred()' rather than 'get_cred()'.
 557         *
 558         * That means that we do not clear the 'non_rcu' flag, since
 559         * we are only installing the cred into the thread-synchronous
 560         * '->cred' pointer, not the '->real_cred' pointer that is
 561         * visible to other threads under RCU.
 562         *
 563         * Also note that we did validate_creds() manually, not depending
 564         * on the validation in 'get_cred()'.
 565         */
 566        get_new_cred((struct cred *)new);
 567        alter_cred_subscribers(new, 1);
 568        rcu_assign_pointer(current->cred, new);
 569        alter_cred_subscribers(old, -1);
 570
 571        kdebug("override_creds() = %p{%d,%d}", old,
 572               atomic_read(&old->usage),
 573               read_cred_subscribers(old));
 574        return old;
 575}
 576EXPORT_SYMBOL(override_creds);
 577
 578/**
 579 * revert_creds - Revert a temporary subjective credentials override
 580 * @old: The credentials to be restored
 581 *
 582 * Revert a temporary set of override subjective credentials to an old set,
 583 * discarding the override set.
 584 */
 585void revert_creds(const struct cred *old)
 586{
 587        const struct cred *override = current->cred;
 588
 589        kdebug("revert_creds(%p{%d,%d})", old,
 590               atomic_read(&old->usage),
 591               read_cred_subscribers(old));
 592
 593        validate_creds(old);
 594        validate_creds(override);
 595        alter_cred_subscribers(old, 1);
 596        rcu_assign_pointer(current->cred, old);
 597        alter_cred_subscribers(override, -1);
 598        put_cred(override);
 599}
 600EXPORT_SYMBOL(revert_creds);
 601
 602/**
 603 * cred_fscmp - Compare two credentials with respect to filesystem access.
 604 * @a: The first credential
 605 * @b: The second credential
 606 *
 607 * cred_cmp() will return zero if both credentials have the same
 608 * fsuid, fsgid, and supplementary groups.  That is, if they will both
 609 * provide the same access to files based on mode/uid/gid.
 610 * If the credentials are different, then either -1 or 1 will
 611 * be returned depending on whether @a comes before or after @b
 612 * respectively in an arbitrary, but stable, ordering of credentials.
 613 *
 614 * Return: -1, 0, or 1 depending on comparison
 615 */
 616int cred_fscmp(const struct cred *a, const struct cred *b)
 617{
 618        struct group_info *ga, *gb;
 619        int g;
 620
 621        if (a == b)
 622                return 0;
 623        if (uid_lt(a->fsuid, b->fsuid))
 624                return -1;
 625        if (uid_gt(a->fsuid, b->fsuid))
 626                return 1;
 627
 628        if (gid_lt(a->fsgid, b->fsgid))
 629                return -1;
 630        if (gid_gt(a->fsgid, b->fsgid))
 631                return 1;
 632
 633        ga = a->group_info;
 634        gb = b->group_info;
 635        if (ga == gb)
 636                return 0;
 637        if (ga == NULL)
 638                return -1;
 639        if (gb == NULL)
 640                return 1;
 641        if (ga->ngroups < gb->ngroups)
 642                return -1;
 643        if (ga->ngroups > gb->ngroups)
 644                return 1;
 645
 646        for (g = 0; g < ga->ngroups; g++) {
 647                if (gid_lt(ga->gid[g], gb->gid[g]))
 648                        return -1;
 649                if (gid_gt(ga->gid[g], gb->gid[g]))
 650                        return 1;
 651        }
 652        return 0;
 653}
 654EXPORT_SYMBOL(cred_fscmp);
 655
 656/*
 657 * initialise the credentials stuff
 658 */
 659void __init cred_init(void)
 660{
 661        /* allocate a slab in which we can store credentials */
 662        cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred), 0,
 663                        SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL);
 664}
 665
 666/**
 667 * prepare_kernel_cred - Prepare a set of credentials for a kernel service
 668 * @daemon: A userspace daemon to be used as a reference
 669 *
 670 * Prepare a set of credentials for a kernel service.  This can then be used to
 671 * override a task's own credentials so that work can be done on behalf of that
 672 * task that requires a different subjective context.
 673 *
 674 * @daemon is used to provide a base for the security record, but can be NULL.
 675 * If @daemon is supplied, then the security data will be derived from that;
 676 * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
 677 *
 678 * The caller may change these controls afterwards if desired.
 679 *
 680 * Returns the new credentials or NULL if out of memory.
 681 */
 682struct cred *prepare_kernel_cred(struct task_struct *daemon)
 683{
 684        const struct cred *old;
 685        struct cred *new;
 686
 687        new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
 688        if (!new)
 689                return NULL;
 690
 691        kdebug("prepare_kernel_cred() alloc %p", new);
 692
 693        if (daemon)
 694                old = get_task_cred(daemon);
 695        else
 696                old = get_cred(&init_cred);
 697
 698        validate_creds(old);
 699
 700        *new = *old;
 701        new->non_rcu = 0;
 702        atomic_set(&new->usage, 1);
 703        set_cred_subscribers(new, 0);
 704        get_uid(new->user);
 705        get_user_ns(new->user_ns);
 706        get_group_info(new->group_info);
 707
 708#ifdef CONFIG_KEYS
 709        new->session_keyring = NULL;
 710        new->process_keyring = NULL;
 711        new->thread_keyring = NULL;
 712        new->request_key_auth = NULL;
 713        new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
 714#endif
 715
 716#ifdef CONFIG_SECURITY
 717        new->security = NULL;
 718#endif
 719        if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)
 720                goto error;
 721
 722        put_cred(old);
 723        validate_creds(new);
 724        return new;
 725
 726error:
 727        put_cred(new);
 728        put_cred(old);
 729        return NULL;
 730}
 731EXPORT_SYMBOL(prepare_kernel_cred);
 732
 733/**
 734 * set_security_override - Set the security ID in a set of credentials
 735 * @new: The credentials to alter
 736 * @secid: The LSM security ID to set
 737 *
 738 * Set the LSM security ID in a set of credentials so that the subjective
 739 * security is overridden when an alternative set of credentials is used.
 740 */
 741int set_security_override(struct cred *new, u32 secid)
 742{
 743        return security_kernel_act_as(new, secid);
 744}
 745EXPORT_SYMBOL(set_security_override);
 746
 747/**
 748 * set_security_override_from_ctx - Set the security ID in a set of credentials
 749 * @new: The credentials to alter
 750 * @secctx: The LSM security context to generate the security ID from.
 751 *
 752 * Set the LSM security ID in a set of credentials so that the subjective
 753 * security is overridden when an alternative set of credentials is used.  The
 754 * security ID is specified in string form as a security context to be
 755 * interpreted by the LSM.
 756 */
 757int set_security_override_from_ctx(struct cred *new, const char *secctx)
 758{
 759        u32 secid;
 760        int ret;
 761
 762        ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
 763        if (ret < 0)
 764                return ret;
 765
 766        return set_security_override(new, secid);
 767}
 768EXPORT_SYMBOL(set_security_override_from_ctx);
 769
 770/**
 771 * set_create_files_as - Set the LSM file create context in a set of credentials
 772 * @new: The credentials to alter
 773 * @inode: The inode to take the context from
 774 *
 775 * Change the LSM file creation context in a set of credentials to be the same
 776 * as the object context of the specified inode, so that the new inodes have
 777 * the same MAC context as that inode.
 778 */
 779int set_create_files_as(struct cred *new, struct inode *inode)
 780{
 781        if (!uid_valid(inode->i_uid) || !gid_valid(inode->i_gid))
 782                return -EINVAL;
 783        new->fsuid = inode->i_uid;
 784        new->fsgid = inode->i_gid;
 785        return security_kernel_create_files_as(new, inode);
 786}
 787EXPORT_SYMBOL(set_create_files_as);
 788
 789#ifdef CONFIG_DEBUG_CREDENTIALS
 790
 791bool creds_are_invalid(const struct cred *cred)
 792{
 793        if (cred->magic != CRED_MAGIC)
 794                return true;
 795        return false;
 796}
 797EXPORT_SYMBOL(creds_are_invalid);
 798
 799/*
 800 * dump invalid credentials
 801 */
 802static void dump_invalid_creds(const struct cred *cred, const char *label,
 803                               const struct task_struct *tsk)
 804{
 805        printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
 806               label, cred,
 807               cred == &init_cred ? "[init]" : "",
 808               cred == tsk->real_cred ? "[real]" : "",
 809               cred == tsk->cred ? "[eff]" : "");
 810        printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
 811               cred->magic, cred->put_addr);
 812        printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
 813               atomic_read(&cred->usage),
 814               read_cred_subscribers(cred));
 815        printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
 816                from_kuid_munged(&init_user_ns, cred->uid),
 817                from_kuid_munged(&init_user_ns, cred->euid),
 818                from_kuid_munged(&init_user_ns, cred->suid),
 819                from_kuid_munged(&init_user_ns, cred->fsuid));
 820        printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
 821                from_kgid_munged(&init_user_ns, cred->gid),
 822                from_kgid_munged(&init_user_ns, cred->egid),
 823                from_kgid_munged(&init_user_ns, cred->sgid),
 824                from_kgid_munged(&init_user_ns, cred->fsgid));
 825#ifdef CONFIG_SECURITY
 826        printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
 827        if ((unsigned long) cred->security >= PAGE_SIZE &&
 828            (((unsigned long) cred->security & 0xffffff00) !=
 829             (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
 830                printk(KERN_ERR "CRED: ->security {%x, %x}\n",
 831                       ((u32*)cred->security)[0],
 832                       ((u32*)cred->security)[1]);
 833#endif
 834}
 835
 836/*
 837 * report use of invalid credentials
 838 */
 839void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
 840{
 841        printk(KERN_ERR "CRED: Invalid credentials\n");
 842        printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 843        dump_invalid_creds(cred, "Specified", current);
 844        BUG();
 845}
 846EXPORT_SYMBOL(__invalid_creds);
 847
 848/*
 849 * check the credentials on a process
 850 */
 851void __validate_process_creds(struct task_struct *tsk,
 852                              const char *file, unsigned line)
 853{
 854        if (tsk->cred == tsk->real_cred) {
 855                if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
 856                             creds_are_invalid(tsk->cred)))
 857                        goto invalid_creds;
 858        } else {
 859                if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
 860                             read_cred_subscribers(tsk->cred) < 1 ||
 861                             creds_are_invalid(tsk->real_cred) ||
 862                             creds_are_invalid(tsk->cred)))
 863                        goto invalid_creds;
 864        }
 865        return;
 866
 867invalid_creds:
 868        printk(KERN_ERR "CRED: Invalid process credentials\n");
 869        printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 870
 871        dump_invalid_creds(tsk->real_cred, "Real", tsk);
 872        if (tsk->cred != tsk->real_cred)
 873                dump_invalid_creds(tsk->cred, "Effective", tsk);
 874        else
 875                printk(KERN_ERR "CRED: Effective creds == Real creds\n");
 876        BUG();
 877}
 878EXPORT_SYMBOL(__validate_process_creds);
 879
 880/*
 881 * check creds for do_exit()
 882 */
 883void validate_creds_for_do_exit(struct task_struct *tsk)
 884{
 885        kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
 886               tsk->real_cred, tsk->cred,
 887               atomic_read(&tsk->cred->usage),
 888               read_cred_subscribers(tsk->cred));
 889
 890        __validate_process_creds(tsk, __FILE__, __LINE__);
 891}
 892
 893#endif /* CONFIG_DEBUG_CREDENTIALS */
 894