kernel/cred.c

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