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