kernel/cred.c

   1 /* Task credentials management - see Documentation/credentials.txt
   2  *
   3  * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public Licence
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the Licence, or (at your option) any later version.
  10  */
  11 #include <linux/module.h>
  12 #include <linux/cred.h>
  13 #include <linux/sched.h>
  14 #include <linux/key.h>
  15 #include <linux/keyctl.h>
  16 #include <linux/init_task.h>
  17 #include <linux/security.h>
  18 #include <linux/cn_proc.h>
  19 #include "cred-internals.h"
  20
  21 #if 0
  22 #define kdebug(FMT, ...) \
  23         printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
  24 #else
  25 static inline __attribute__((format(printf, 1, 2)))
  26 void no_printk(const char *fmt, ...)
  27 {
  28 }
  29 #define kdebug(FMT, ...) \
  30         no_printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
  31 #endif
  32
  33 static struct kmem_cache *cred_jar;
  34
  35 /*
  36  * The common credentials for the initial task's thread group
  37  */
  38 #ifdef CONFIG_KEYS
  39 static struct thread_group_cred init_tgcred = {
  40         .usage  = ATOMIC_INIT(2),
  41         .tgid   = 0,
  42         .lock   = SPIN_LOCK_UNLOCKED,
  43 };
  44 #endif
  45
  46 /*
  47  * The initial credentials for the initial task
  48  */
  49 struct cred init_cred = {
  50         .usage                  = ATOMIC_INIT(4),
  51 #ifdef CONFIG_DEBUG_CREDENTIALS
  52         .subscribers            = ATOMIC_INIT(2),
  53         .magic                  = CRED_MAGIC,
  54 #endif
  55         .securebits             = SECUREBITS_DEFAULT,
  56         .cap_inheritable        = CAP_INIT_INH_SET,
  57         .cap_permitted          = CAP_FULL_SET,
  58         .cap_effective          = CAP_INIT_EFF_SET,
  59         .cap_bset               = CAP_INIT_BSET,
  60         .user                   = INIT_USER,
  61         .group_info             = &init_groups,
  62 #ifdef CONFIG_KEYS
  63         .tgcred                 = &init_tgcred,
  64 #endif
  65 };
  66
  67 static 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
  74 static 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
  83 static 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  * Dispose of the shared task group credentials
  94  */
  95 #ifdef CONFIG_KEYS
  96 static void release_tgcred_rcu(struct rcu_head *rcu)
  97 {
  98         struct thread_group_cred *tgcred =
  99                 container_of(rcu, struct thread_group_cred, rcu);
 100
 101         BUG_ON(atomic_read(&tgcred->usage) != 0);
 102
 103         key_put(tgcred->session_keyring);
 104         key_put(tgcred->process_keyring);
 105         kfree(tgcred);
 106 }
 107 #endif
 108
 109 /*
 110  * Release a set of thread group credentials.
 111  */
 112 static void release_tgcred(struct cred *cred)
 113 {
 114 #ifdef CONFIG_KEYS
 115         struct thread_group_cred *tgcred = cred->tgcred;
 116
 117         if (atomic_dec_and_test(&tgcred->usage))
 118                 call_rcu(&tgcred->rcu, release_tgcred_rcu);
 119 #endif
 120 }
 121
 122 /*
 123  * The RCU callback to actually dispose of a set of credentials
 124  */
 125 static void put_cred_rcu(struct rcu_head *rcu)
 126 {
 127         struct cred *cred = container_of(rcu, struct cred, rcu);
 128
 129         kdebug("put_cred_rcu(%p)", cred);
 130
 131 #ifdef CONFIG_DEBUG_CREDENTIALS
 132         if (cred->magic != CRED_MAGIC_DEAD ||
 133             atomic_read(&cred->usage) != 0 ||
 134             read_cred_subscribers(cred) != 0)
 135                 panic("CRED: put_cred_rcu() sees %p with"
 136                       " mag %x, put %p, usage %d, subscr %d\n",
 137                       cred, cred->magic, cred->put_addr,
 138                       atomic_read(&cred->usage),
 139                       read_cred_subscribers(cred));
 140 #else
 141         if (atomic_read(&cred->usage) != 0)
 142                 panic("CRED: put_cred_rcu() sees %p with usage %d\n",
 143                       cred, atomic_read(&cred->usage));
 144 #endif
 145
 146         security_cred_free(cred);
 147         key_put(cred->thread_keyring);
 148         key_put(cred->request_key_auth);
 149         release_tgcred(cred);
 150         put_group_info(cred->group_info);
 151         free_uid(cred->user);
 152         kmem_cache_free(cred_jar, cred);
 153 }
 154
 155 /**
 156  * __put_cred - Destroy a set of credentials
 157  * @cred: The record to release
 158  *
 159  * Destroy a set of credentials on which no references remain.
 160  */
 161 void __put_cred(struct cred *cred)
 162 {
 163         kdebug("__put_cred(%p{%d,%d})", cred,
 164                atomic_read(&cred->usage),
 165                read_cred_subscribers(cred));
 166
 167         BUG_ON(atomic_read(&cred->usage) != 0);
 168 #ifdef CONFIG_DEBUG_CREDENTIALS
 169         BUG_ON(read_cred_subscribers(cred) != 0);
 170         cred->magic = CRED_MAGIC_DEAD;
 171         cred->put_addr = __builtin_return_address(0);
 172 #endif
 173         BUG_ON(cred == current->cred);
 174         BUG_ON(cred == current->real_cred);
 175
 176         call_rcu(&cred->rcu, put_cred_rcu);
 177 }
 178 EXPORT_SYMBOL(__put_cred);
 179
 180 /*
 181  * Clean up a task's credentials when it exits
 182  */
 183 void exit_creds(struct task_struct *tsk)
 184 {
 185         struct cred *cred;
 186
 187         kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
 188                atomic_read(&tsk->cred->usage),
 189                read_cred_subscribers(tsk->cred));
 190
 191         cred = (struct cred *) tsk->real_cred;
 192         tsk->real_cred = NULL;
 193         validate_creds(cred);
 194         alter_cred_subscribers(cred, -1);
 195         put_cred(cred);
 196
 197         cred = (struct cred *) tsk->cred;
 198         tsk->cred = NULL;
 199         validate_creds(cred);
 200         alter_cred_subscribers(cred, -1);
 201         put_cred(cred);
 202 }
 203
 204 /**
 205  * prepare_creds - Prepare a new set of credentials for modification
 206  *
 207  * Prepare a new set of task credentials for modification.  A task's creds
 208  * shouldn't generally be modified directly, therefore this function is used to
 209  * prepare a new copy, which the caller then modifies and then commits by
 210  * calling commit_creds().
 211  *
 212  * Preparation involves making a copy of the objective creds for modification.
 213  *
 214  * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
 215  *
 216  * Call commit_creds() or abort_creds() to clean up.
 217  */
 218 struct cred *prepare_creds(void)
 219 {
 220         struct task_struct *task = current;
 221         const struct cred *old;
 222         struct cred *new;
 223
 224         validate_process_creds();
 225
 226         new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
 227         if (!new)
 228                 return NULL;
 229
 230         kdebug("prepare_creds() alloc %p", new);
 231
 232         old = task->cred;
 233         memcpy(new, old, sizeof(struct cred));
 234
 235         atomic_set(&new->usage, 1);
 236         set_cred_subscribers(new, 0);
 237         get_group_info(new->group_info);
 238         get_uid(new->user);
 239
 240 #ifdef CONFIG_KEYS
 241         key_get(new->thread_keyring);
 242         key_get(new->request_key_auth);
 243         atomic_inc(&new->tgcred->usage);
 244 #endif
 245
 246 #ifdef CONFIG_SECURITY
 247         new->security = NULL;
 248 #endif
 249
 250         if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
 251                 goto error;
 252         validate_creds(new);
 253         return new;
 254
 255 error:
 256         abort_creds(new);
 257         return NULL;
 258 }
 259 EXPORT_SYMBOL(prepare_creds);
 260
 261 /*
 262  * Prepare credentials for current to perform an execve()
 263  * - The caller must hold current->cred_guard_mutex
 264  */
 265 struct cred *prepare_exec_creds(void)
 266 {
 267         struct thread_group_cred *tgcred = NULL;
 268         struct cred *new;
 269
 270 #ifdef CONFIG_KEYS
 271         tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
 272         if (!tgcred)
 273                 return NULL;
 274 #endif
 275
 276         new = prepare_creds();
 277         if (!new) {
 278                 kfree(tgcred);
 279                 return new;
 280         }
 281
 282 #ifdef CONFIG_KEYS
 283         /* newly exec'd tasks don't get a thread keyring */
 284         key_put(new->thread_keyring);
 285         new->thread_keyring = NULL;
 286
 287         /* create a new per-thread-group creds for all this set of threads to
 288          * share */
 289         memcpy(tgcred, new->tgcred, sizeof(struct thread_group_cred));
 290
 291         atomic_set(&tgcred->usage, 1);
 292         spin_lock_init(&tgcred->lock);
 293
 294         /* inherit the session keyring; new process keyring */
 295         key_get(tgcred->session_keyring);
 296         tgcred->process_keyring = NULL;
 297
 298         release_tgcred(new);
 299         new->tgcred = tgcred;
 300 #endif
 301
 302         return new;
 303 }
 304
 305 /*
 306  * prepare new credentials for the usermode helper dispatcher
 307  */
 308 struct cred *prepare_usermodehelper_creds(void)
 309 {
 310 #ifdef CONFIG_KEYS
 311         struct thread_group_cred *tgcred = NULL;
 312 #endif
 313         struct cred *new;
 314
 315 #ifdef CONFIG_KEYS
 316         tgcred = kzalloc(sizeof(*new->tgcred), GFP_ATOMIC);
 317         if (!tgcred)
 318                 return NULL;
 319 #endif
 320
 321         new = kmem_cache_alloc(cred_jar, GFP_ATOMIC);
 322         if (!new)
 323                 return NULL;
 324
 325         kdebug("prepare_usermodehelper_creds() alloc %p", new);
 326
 327         memcpy(new, &init_cred, sizeof(struct cred));
 328
 329         atomic_set(&new->usage, 1);
 330         set_cred_subscribers(new, 0);
 331         get_group_info(new->group_info);
 332         get_uid(new->user);
 333
 334 #ifdef CONFIG_KEYS
 335         new->thread_keyring = NULL;
 336         new->request_key_auth = NULL;
 337         new->jit_keyring = KEY_REQKEY_DEFL_DEFAULT;
 338
 339         atomic_set(&tgcred->usage, 1);
 340         spin_lock_init(&tgcred->lock);
 341         new->tgcred = tgcred;
 342 #endif
 343
 344 #ifdef CONFIG_SECURITY
 345         new->security = NULL;
 346 #endif
 347         if (security_prepare_creds(new, &init_cred, GFP_ATOMIC) < 0)
 348                 goto error;
 349         validate_creds(new);
 350
 351         BUG_ON(atomic_read(&new->usage) != 1);
 352         return new;
 353
 354 error:
 355         put_cred(new);
 356         return NULL;
 357 }
 358
 359 /*
 360  * Copy credentials for the new process created by fork()
 361  *
 362  * We share if we can, but under some circumstances we have to generate a new
 363  * set.
 364  *
 365  * The new process gets the current process's subjective credentials as its
 366  * objective and subjective credentials
 367  */
 368 int copy_creds(struct task_struct *p, unsigned long clone_flags)
 369 {
 370 #ifdef CONFIG_KEYS
 371         struct thread_group_cred *tgcred;
 372 #endif
 373         struct cred *new;
 374         int ret;
 375
 376         mutex_init(&p->cred_guard_mutex);
 377
 378         if (
 379 #ifdef CONFIG_KEYS
 380                 !p->cred->thread_keyring &&
 381 #endif
 382                 clone_flags & CLONE_THREAD
 383             ) {
 384                 p->real_cred = get_cred(p->cred);
 385                 get_cred(p->cred);
 386                 alter_cred_subscribers(p->cred, 2);
 387                 kdebug("share_creds(%p{%d,%d})",
 388                        p->cred, atomic_read(&p->cred->usage),
 389                        read_cred_subscribers(p->cred));
 390                 atomic_inc(&p->cred->user->processes);
 391                 return 0;
 392         }
 393
 394         new = prepare_creds();
 395         if (!new)
 396                 return -ENOMEM;
 397
 398         if (clone_flags & CLONE_NEWUSER) {
 399                 ret = create_user_ns(new);
 400                 if (ret < 0)
 401                         goto error_put;
 402         }
 403
 404 #ifdef CONFIG_KEYS
 405         /* new threads get their own thread keyrings if their parent already
 406          * had one */
 407         if (new->thread_keyring) {
 408                 key_put(new->thread_keyring);
 409                 new->thread_keyring = NULL;
 410                 if (clone_flags & CLONE_THREAD)
 411                         install_thread_keyring_to_cred(new);
 412         }
 413
 414         /* we share the process and session keyrings between all the threads in
 415          * a process - this is slightly icky as we violate COW credentials a
 416          * bit */
 417         if (!(clone_flags & CLONE_THREAD)) {
 418                 tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
 419                 if (!tgcred) {
 420                         ret = -ENOMEM;
 421                         goto error_put;
 422                 }
 423                 atomic_set(&tgcred->usage, 1);
 424                 spin_lock_init(&tgcred->lock);
 425                 tgcred->process_keyring = NULL;
 426                 tgcred->session_keyring = key_get(new->tgcred->session_keyring);
 427
 428                 release_tgcred(new);
 429                 new->tgcred = tgcred;
 430         }
 431 #endif
 432
 433         atomic_inc(&new->user->processes);
 434         p->cred = p->real_cred = get_cred(new);
 435         alter_cred_subscribers(new, 2);
 436         validate_creds(new);
 437         return 0;
 438
 439 error_put:
 440         put_cred(new);
 441         return ret;
 442 }
 443
 444 /**
 445  * commit_creds - Install new credentials upon the current task
 446  * @new: The credentials to be assigned
 447  *
 448  * Install a new set of credentials to the current task, using RCU to replace
 449  * the old set.  Both the objective and the subjective credentials pointers are
 450  * updated.  This function may not be called if the subjective credentials are
 451  * in an overridden state.
 452  *
 453  * This function eats the caller's reference to the new credentials.
 454  *
 455  * Always returns 0 thus allowing this function to be tail-called at the end
 456  * of, say, sys_setgid().
 457  */
 458 int commit_creds(struct cred *new)
 459 {
 460         struct task_struct *task = current;
 461         const struct cred *old = task->real_cred;
 462
 463         kdebug("commit_creds(%p{%d,%d})", new,
 464                atomic_read(&new->usage),
 465                read_cred_subscribers(new));
 466
 467         BUG_ON(task->cred != old);
 468 #ifdef CONFIG_DEBUG_CREDENTIALS
 469         BUG_ON(read_cred_subscribers(old) < 2);
 470         validate_creds(old);
 471         validate_creds(new);
 472 #endif
 473         BUG_ON(atomic_read(&new->usage) < 1);
 474
 475         security_commit_creds(new, old);
 476
 477         get_cred(new); /* we will require a ref for the subj creds too */
 478
 479         /* dumpability changes */
 480         if (old->euid != new->euid ||
 481             old->egid != new->egid ||
 482             old->fsuid != new->fsuid ||
 483             old->fsgid != new->fsgid ||
 484             !cap_issubset(new->cap_permitted, old->cap_permitted)) {
 485                 if (task->mm)
 486                         set_dumpable(task->mm, suid_dumpable);
 487                 task->pdeath_signal = 0;
 488                 smp_wmb();
 489         }
 490
 491         /* alter the thread keyring */
 492         if (new->fsuid != old->fsuid)
 493                 key_fsuid_changed(task);
 494         if (new->fsgid != old->fsgid)
 495                 key_fsgid_changed(task);
 496
 497         /* do it
 498          * - What if a process setreuid()'s and this brings the
 499          *   new uid over his NPROC rlimit?  We can check this now
 500          *   cheaply with the new uid cache, so if it matters
 501          *   we should be checking for it.  -DaveM
 502          */
 503         alter_cred_subscribers(new, 2);
 504         if (new->user != old->user)
 505                 atomic_inc(&new->user->processes);
 506         rcu_assign_pointer(task->real_cred, new);
 507         rcu_assign_pointer(task->cred, new);
 508         if (new->user != old->user)
 509                 atomic_dec(&old->user->processes);
 510         alter_cred_subscribers(old, -2);
 511
 512         sched_switch_user(task);
 513
 514         /* send notifications */
 515         if (new->uid   != old->uid  ||
 516             new->euid  != old->euid ||
 517             new->suid  != old->suid ||
 518             new->fsuid != old->fsuid)
 519                 proc_id_connector(task, PROC_EVENT_UID);
 520
 521         if (new->gid   != old->gid  ||
 522             new->egid  != old->egid ||
 523             new->sgid  != old->sgid ||
 524             new->fsgid != old->fsgid)
 525                 proc_id_connector(task, PROC_EVENT_GID);
 526
 527         /* release the old obj and subj refs both */
 528         put_cred(old);
 529         put_cred(old);
 530         return 0;
 531 }
 532 EXPORT_SYMBOL(commit_creds);
 533
 534 /**
 535  * abort_creds - Discard a set of credentials and unlock the current task
 536  * @new: The credentials that were going to be applied
 537  *
 538  * Discard a set of credentials that were under construction and unlock the
 539  * current task.
 540  */
 541 void abort_creds(struct cred *new)
 542 {
 543         kdebug("abort_creds(%p{%d,%d})", new,
 544                atomic_read(&new->usage),
 545                read_cred_subscribers(new));
 546
 547 #ifdef CONFIG_DEBUG_CREDENTIALS
 548         BUG_ON(read_cred_subscribers(new) != 0);
 549 #endif
 550         BUG_ON(atomic_read(&new->usage) < 1);
 551         put_cred(new);
 552 }
 553 EXPORT_SYMBOL(abort_creds);
 554
 555 /**
 556  * override_creds - Override the current process's subjective credentials
 557  * @new: The credentials to be assigned
 558  *
 559  * Install a set of temporary override subjective credentials on the current
 560  * process, returning the old set for later reversion.
 561  */
 562 const struct cred *override_creds(const struct cred *new)
 563 {
 564         const struct cred *old = current->cred;
 565
 566         kdebug("override_creds(%p{%d,%d})", new,
 567                atomic_read(&new->usage),
 568                read_cred_subscribers(new));
 569
 570         validate_creds(old);
 571         validate_creds(new);
 572         get_cred(new);
 573         alter_cred_subscribers(new, 1);
 574         rcu_assign_pointer(current->cred, new);
 575         alter_cred_subscribers(old, -1);
 576
 577         kdebug("override_creds() = %p{%d,%d}", old,
 578                atomic_read(&old->usage),
 579                read_cred_subscribers(old));
 580         return old;
 581 }
 582 EXPORT_SYMBOL(override_creds);
 583
 584 /**
 585  * revert_creds - Revert a temporary subjective credentials override
 586  * @old: The credentials to be restored
 587  *
 588  * Revert a temporary set of override subjective credentials to an old set,
 589  * discarding the override set.
 590  */
 591 void revert_creds(const struct cred *old)
 592 {
 593         const struct cred *override = current->cred;
 594
 595         kdebug("revert_creds(%p{%d,%d})", old,
 596                atomic_read(&old->usage),
 597                read_cred_subscribers(old));
 598
 599         validate_creds(old);
 600         validate_creds(override);
 601         alter_cred_subscribers(old, 1);
 602         rcu_assign_pointer(current->cred, old);
 603         alter_cred_subscribers(override, -1);
 604         put_cred(override);
 605 }
 606 EXPORT_SYMBOL(revert_creds);
 607
 608 /*
 609  * initialise the credentials stuff
 610  */
 611 void __init cred_init(void)
 612 {
 613         /* allocate a slab in which we can store credentials */
 614         cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred),
 615                                      0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
 616 }
 617
 618 /**
 619  * prepare_kernel_cred - Prepare a set of credentials for a kernel service
 620  * @daemon: A userspace daemon to be used as a reference
 621  *
 622  * Prepare a set of credentials for a kernel service.  This can then be used to
 623  * override a task's own credentials so that work can be done on behalf of that
 624  * task that requires a different subjective context.
 625  *
 626  * @daemon is used to provide a base for the security record, but can be NULL.
 627  * If @daemon is supplied, then the security data will be derived from that;
 628  * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
 629  *
 630  * The caller may change these controls afterwards if desired.
 631  *
 632  * Returns the new credentials or NULL if out of memory.
 633  *
 634  * Does not take, and does not return holding current->cred_replace_mutex.
 635  */
 636 struct cred *prepare_kernel_cred(struct task_struct *daemon)
 637 {
 638         const struct cred *old;
 639         struct cred *new;
 640
 641         new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
 642         if (!new)
 643                 return NULL;
 644
 645         kdebug("prepare_kernel_cred() alloc %p", new);
 646
 647         if (daemon)
 648                 old = get_task_cred(daemon);
 649         else
 650                 old = get_cred(&init_cred);
 651
 652         validate_creds(old);
 653
 654         *new = *old;
 655         get_uid(new->user);
 656         get_group_info(new->group_info);
 657
 658 #ifdef CONFIG_KEYS
 659         atomic_inc(&init_tgcred.usage);
 660         new->tgcred = &init_tgcred;
 661         new->request_key_auth = NULL;
 662         new->thread_keyring = NULL;
 663         new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
 664 #endif
 665
 666 #ifdef CONFIG_SECURITY
 667         new->security = NULL;
 668 #endif
 669         if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
 670                 goto error;
 671
 672         atomic_set(&new->usage, 1);
 673         set_cred_subscribers(new, 0);
 674         put_cred(old);
 675         validate_creds(new);
 676         return new;
 677
 678 error:
 679         put_cred(new);
 680         put_cred(old);
 681         return NULL;
 682 }
 683 EXPORT_SYMBOL(prepare_kernel_cred);
 684
 685 /**
 686  * set_security_override - Set the security ID in a set of credentials
 687  * @new: The credentials to alter
 688  * @secid: The LSM security ID to set
 689  *
 690  * Set the LSM security ID in a set of credentials so that the subjective
 691  * security is overridden when an alternative set of credentials is used.
 692  */
 693 int set_security_override(struct cred *new, u32 secid)
 694 {
 695         return security_kernel_act_as(new, secid);
 696 }
 697 EXPORT_SYMBOL(set_security_override);
 698
 699 /**
 700  * set_security_override_from_ctx - Set the security ID in a set of credentials
 701  * @new: The credentials to alter
 702  * @secctx: The LSM security context to generate the security ID from.
 703  *
 704  * Set the LSM security ID in a set of credentials so that the subjective
 705  * security is overridden when an alternative set of credentials is used.  The
 706  * security ID is specified in string form as a security context to be
 707  * interpreted by the LSM.
 708  */
 709 int set_security_override_from_ctx(struct cred *new, const char *secctx)
 710 {
 711         u32 secid;
 712         int ret;
 713
 714         ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
 715         if (ret < 0)
 716                 return ret;
 717
 718         return set_security_override(new, secid);
 719 }
 720 EXPORT_SYMBOL(set_security_override_from_ctx);
 721
 722 /**
 723  * set_create_files_as - Set the LSM file create context in a set of credentials
 724  * @new: The credentials to alter
 725  * @inode: The inode to take the context from
 726  *
 727  * Change the LSM file creation context in a set of credentials to be the same
 728  * as the object context of the specified inode, so that the new inodes have
 729  * the same MAC context as that inode.
 730  */
 731 int set_create_files_as(struct cred *new, struct inode *inode)
 732 {
 733         new->fsuid = inode->i_uid;
 734         new->fsgid = inode->i_gid;
 735         return security_kernel_create_files_as(new, inode);
 736 }
 737 EXPORT_SYMBOL(set_create_files_as);
 738
 739 #ifdef CONFIG_DEBUG_CREDENTIALS
 740
 741 /*
 742  * dump invalid credentials
 743  */
 744 static void dump_invalid_creds(const struct cred *cred, const char *label,
 745                                const struct task_struct *tsk)
 746 {
 747         printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
 748                label, cred,
 749                cred == &init_cred ? "[init]" : "",
 750                cred == tsk->real_cred ? "[real]" : "",
 751                cred == tsk->cred ? "[eff]" : "");
 752         printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
 753                cred->magic, cred->put_addr);
 754         printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
 755                atomic_read(&cred->usage),
 756                read_cred_subscribers(cred));
 757         printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
 758                cred->uid, cred->euid, cred->suid, cred->fsuid);
 759         printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
 760                cred->gid, cred->egid, cred->sgid, cred->fsgid);
 761 #ifdef CONFIG_SECURITY
 762         printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
 763         if ((unsigned long) cred->security >= PAGE_SIZE &&
 764             (((unsigned long) cred->security & 0xffffff00) !=
 765              (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
 766                 printk(KERN_ERR "CRED: ->security {%x, %x}\n",
 767                        ((u32*)cred->security)[0],
 768                        ((u32*)cred->security)[1]);
 769 #endif
 770 }
 771
 772 /*
 773  * report use of invalid credentials
 774  */
 775 void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
 776 {
 777         printk(KERN_ERR "CRED: Invalid credentials\n");
 778         printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 779         dump_invalid_creds(cred, "Specified", current);
 780         BUG();
 781 }
 782 EXPORT_SYMBOL(__invalid_creds);
 783
 784 /*
 785  * check the credentials on a process
 786  */
 787 void __validate_process_creds(struct task_struct *tsk,
 788                               const char *file, unsigned line)
 789 {
 790         if (tsk->cred == tsk->real_cred) {
 791                 if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
 792                              creds_are_invalid(tsk->cred)))
 793                         goto invalid_creds;
 794         } else {
 795                 if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
 796                              read_cred_subscribers(tsk->cred) < 1 ||
 797                              creds_are_invalid(tsk->real_cred) ||
 798                              creds_are_invalid(tsk->cred)))
 799                         goto invalid_creds;
 800         }
 801         return;
 802
 803 invalid_creds:
 804         printk(KERN_ERR "CRED: Invalid process credentials\n");
 805         printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 806
 807         dump_invalid_creds(tsk->real_cred, "Real", tsk);
 808         if (tsk->cred != tsk->real_cred)
 809                 dump_invalid_creds(tsk->cred, "Effective", tsk);
 810         else
 811                 printk(KERN_ERR "CRED: Effective creds == Real creds\n");
 812         BUG();
 813 }
 814 EXPORT_SYMBOL(__validate_process_creds);
 815
 816 /*
 817  * check creds for do_exit()
 818  */
 819 void validate_creds_for_do_exit(struct task_struct *tsk)
 820 {
 821         kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
 822                tsk->real_cred, tsk->cred,
 823                atomic_read(&tsk->cred->usage),
 824                read_cred_subscribers(tsk->cred));
 825
 826         __validate_process_creds(tsk, __FILE__, __LINE__);
 827 }
 828
 829 #endif /* CONFIG_DEBUG_CREDENTIALS */