kernel/cred.c

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