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