kernel/cred.c

   1 /* Task credentials management - see Documentation/security/credentials.rst
   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/sched/coredump.h>
  16 #include <linux/key.h>
  17 #include <linux/keyctl.h>
  18 #include <linux/init_task.h>
  19 #include <linux/security.h>
  20 #include <linux/binfmts.h>
  21 #include <linux/cn_proc.h>
  22
  23 #if 0
  24 #define kdebug(FMT, ...)                                                \
  25         printk("[%-5.5s%5u] " FMT "\n",                                 \
  26                current->comm, current->pid, ##__VA_ARGS__)
  27 #else
  28 #define kdebug(FMT, ...)                                                \
  29 do {                                                                    \
  30         if (0)                                                          \
  31                 no_printk("[%-5.5s%5u] " FMT "\n",                      \
  32                           current->comm, current->pid, ##__VA_ARGS__);  \
  33 } while (0)
  34 #endif
  35
  36 static struct kmem_cache *cred_jar;
  37
  38 /* init to 2 - one for init_task, one to ensure it is never freed */
  39 struct group_info init_groups = { .usage = ATOMIC_INIT(2) };
  40
  41 /*
  42  * The initial credentials for the initial task
  43  */
  44 struct cred init_cred = {
  45         .usage                  = ATOMIC_INIT(4),
  46 #ifdef CONFIG_DEBUG_CREDENTIALS
  47         .subscribers            = ATOMIC_INIT(2),
  48         .magic                  = CRED_MAGIC,
  49 #endif
  50         .uid                    = GLOBAL_ROOT_UID,
  51         .gid                    = GLOBAL_ROOT_GID,
  52         .suid                   = GLOBAL_ROOT_UID,
  53         .sgid                   = GLOBAL_ROOT_GID,
  54         .euid                   = GLOBAL_ROOT_UID,
  55         .egid                   = GLOBAL_ROOT_GID,
  56         .fsuid                  = GLOBAL_ROOT_UID,
  57         .fsgid                  = GLOBAL_ROOT_GID,
  58         .securebits             = SECUREBITS_DEFAULT,
  59         .cap_inheritable        = CAP_EMPTY_SET,
  60         .cap_permitted          = CAP_FULL_SET,
  61         .cap_effective          = CAP_FULL_SET,
  62         .cap_bset               = CAP_FULL_SET,
  63         .user                   = INIT_USER,
  64         .user_ns                = &init_user_ns,
  65         .group_info             = &init_groups,
  66 };
  67
  68 static inline void set_cred_subscribers(struct cred *cred, int n)
  69 {
  70 #ifdef CONFIG_DEBUG_CREDENTIALS
  71         atomic_set(&cred->subscribers, n);
  72 #endif
  73 }
  74
  75 static inline int read_cred_subscribers(const struct cred *cred)
  76 {
  77 #ifdef CONFIG_DEBUG_CREDENTIALS
  78         return atomic_read(&cred->subscribers);
  79 #else
  80         return 0;
  81 #endif
  82 }
  83
  84 static inline void alter_cred_subscribers(const struct cred *_cred, int n)
  85 {
  86 #ifdef CONFIG_DEBUG_CREDENTIALS
  87         struct cred *cred = (struct cred *) _cred;
  88
  89         atomic_add(n, &cred->subscribers);
  90 #endif
  91 }
  92
  93 /*
  94  * The RCU callback to actually dispose of a set of credentials
  95  */
  96 static void put_cred_rcu(struct rcu_head *rcu)
  97 {
  98         struct cred *cred = container_of(rcu, struct cred, rcu);
  99
 100         kdebug("put_cred_rcu(%p)", cred);
 101
 102 #ifdef CONFIG_DEBUG_CREDENTIALS
 103         if (cred->magic != CRED_MAGIC_DEAD ||
 104             atomic_read(&cred->usage) != 0 ||
 105             read_cred_subscribers(cred) != 0)
 106                 panic("CRED: put_cred_rcu() sees %p with"
 107                       " mag %x, put %p, usage %d, subscr %d\n",
 108                       cred, cred->magic, cred->put_addr,
 109                       atomic_read(&cred->usage),
 110                       read_cred_subscribers(cred));
 111 #else
 112         if (atomic_read(&cred->usage) != 0)
 113                 panic("CRED: put_cred_rcu() sees %p with usage %d\n",
 114                       cred, atomic_read(&cred->usage));
 115 #endif
 116
 117         security_cred_free(cred);
 118         key_put(cred->session_keyring);
 119         key_put(cred->process_keyring);
 120         key_put(cred->thread_keyring);
 121         key_put(cred->request_key_auth);
 122         if (cred->group_info)
 123                 put_group_info(cred->group_info);
 124         free_uid(cred->user);
 125         put_user_ns(cred->user_ns);
 126         kmem_cache_free(cred_jar, cred);
 127 }
 128
 129 /**
 130  * __put_cred - Destroy a set of credentials
 131  * @cred: The record to release
 132  *
 133  * Destroy a set of credentials on which no references remain.
 134  */
 135 void __put_cred(struct cred *cred)
 136 {
 137         kdebug("__put_cred(%p{%d,%d})", cred,
 138                atomic_read(&cred->usage),
 139                read_cred_subscribers(cred));
 140
 141         BUG_ON(atomic_read(&cred->usage) != 0);
 142 #ifdef CONFIG_DEBUG_CREDENTIALS
 143         BUG_ON(read_cred_subscribers(cred) != 0);
 144         cred->magic = CRED_MAGIC_DEAD;
 145         cred->put_addr = __builtin_return_address(0);
 146 #endif
 147         BUG_ON(cred == current->cred);
 148         BUG_ON(cred == current->real_cred);
 149
 150         call_rcu(&cred->rcu, put_cred_rcu);
 151 }
 152 EXPORT_SYMBOL(__put_cred);
 153
 154 /*
 155  * Clean up a task's credentials when it exits
 156  */
 157 void exit_creds(struct task_struct *tsk)
 158 {
 159         struct cred *cred;
 160
 161         kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
 162                atomic_read(&tsk->cred->usage),
 163                read_cred_subscribers(tsk->cred));
 164
 165         cred = (struct cred *) tsk->real_cred;
 166         tsk->real_cred = NULL;
 167         validate_creds(cred);
 168         alter_cred_subscribers(cred, -1);
 169         put_cred(cred);
 170
 171         cred = (struct cred *) tsk->cred;
 172         tsk->cred = NULL;
 173         validate_creds(cred);
 174         alter_cred_subscribers(cred, -1);
 175         put_cred(cred);
 176 }
 177
 178 /**
 179  * get_task_cred - Get another task's objective credentials
 180  * @task: The task to query
 181  *
 182  * Get the objective credentials of a task, pinning them so that they can't go
 183  * away.  Accessing a task's credentials directly is not permitted.
 184  *
 185  * The caller must also make sure task doesn't get deleted, either by holding a
 186  * ref on task or by holding tasklist_lock to prevent it from being unlinked.
 187  */
 188 const struct cred *get_task_cred(struct task_struct *task)
 189 {
 190         const struct cred *cred;
 191
 192         rcu_read_lock();
 193
 194         do {
 195                 cred = __task_cred((task));
 196                 BUG_ON(!cred);
 197         } while (!atomic_inc_not_zero(&((struct cred *)cred)->usage));
 198
 199         rcu_read_unlock();
 200         return cred;
 201 }
 202
 203 /*
 204  * Allocate blank credentials, such that the credentials can be filled in at a
 205  * later date without risk of ENOMEM.
 206  */
 207 struct cred *cred_alloc_blank(void)
 208 {
 209         struct cred *new;
 210
 211         new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
 212         if (!new)
 213                 return NULL;
 214
 215         atomic_set(&new->usage, 1);
 216 #ifdef CONFIG_DEBUG_CREDENTIALS
 217         new->magic = CRED_MAGIC;
 218 #endif
 219
 220         if (security_cred_alloc_blank(new, GFP_KERNEL) < 0)
 221                 goto error;
 222
 223         return new;
 224
 225 error:
 226         abort_creds(new);
 227         return NULL;
 228 }
 229
 230 /**
 231  * prepare_creds - Prepare a new set of credentials for modification
 232  *
 233  * Prepare a new set of task credentials for modification.  A task's creds
 234  * shouldn't generally be modified directly, therefore this function is used to
 235  * prepare a new copy, which the caller then modifies and then commits by
 236  * calling commit_creds().
 237  *
 238  * Preparation involves making a copy of the objective creds for modification.
 239  *
 240  * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
 241  *
 242  * Call commit_creds() or abort_creds() to clean up.
 243  */
 244 struct cred *prepare_creds(void)
 245 {
 246         struct task_struct *task = current;
 247         const struct cred *old;
 248         struct cred *new;
 249
 250         validate_process_creds();
 251
 252         new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
 253         if (!new)
 254                 return NULL;
 255
 256         kdebug("prepare_creds() alloc %p", new);
 257
 258         old = task->cred;
 259         memcpy(new, old, sizeof(struct cred));
 260
 261         atomic_set(&new->usage, 1);
 262         set_cred_subscribers(new, 0);
 263         get_group_info(new->group_info);
 264         get_uid(new->user);
 265         get_user_ns(new->user_ns);
 266
 267 #ifdef CONFIG_KEYS
 268         key_get(new->session_keyring);
 269         key_get(new->process_keyring);
 270         key_get(new->thread_keyring);
 271         key_get(new->request_key_auth);
 272 #endif
 273
 274 #ifdef CONFIG_SECURITY
 275         new->security = NULL;
 276 #endif
 277
 278         if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
 279                 goto error;
 280         validate_creds(new);
 281         return new;
 282
 283 error:
 284         abort_creds(new);
 285         return NULL;
 286 }
 287 EXPORT_SYMBOL(prepare_creds);
 288
 289 /*
 290  * Prepare credentials for current to perform an execve()
 291  * - The caller must hold ->cred_guard_mutex
 292  */
 293 struct cred *prepare_exec_creds(void)
 294 {
 295         struct cred *new;
 296
 297         new = prepare_creds();
 298         if (!new)
 299                 return new;
 300
 301 #ifdef CONFIG_KEYS
 302         /* newly exec'd tasks don't get a thread keyring */
 303         key_put(new->thread_keyring);
 304         new->thread_keyring = NULL;
 305
 306         /* inherit the session keyring; new process keyring */
 307         key_put(new->process_keyring);
 308         new->process_keyring = NULL;
 309 #endif
 310
 311         return new;
 312 }
 313
 314 /*
 315  * Copy credentials for the new process created by fork()
 316  *
 317  * We share if we can, but under some circumstances we have to generate a new
 318  * set.
 319  *
 320  * The new process gets the current process's subjective credentials as its
 321  * objective and subjective credentials
 322  */
 323 int copy_creds(struct task_struct *p, unsigned long clone_flags)
 324 {
 325         struct cred *new;
 326         int ret;
 327
 328         if (
 329 #ifdef CONFIG_KEYS
 330                 !p->cred->thread_keyring &&
 331 #endif
 332                 clone_flags & CLONE_THREAD
 333             ) {
 334                 p->real_cred = get_cred(p->cred);
 335                 get_cred(p->cred);
 336                 alter_cred_subscribers(p->cred, 2);
 337                 kdebug("share_creds(%p{%d,%d})",
 338                        p->cred, atomic_read(&p->cred->usage),
 339                        read_cred_subscribers(p->cred));
 340                 atomic_inc(&p->cred->user->processes);
 341                 return 0;
 342         }
 343
 344         new = prepare_creds();
 345         if (!new)
 346                 return -ENOMEM;
 347
 348         if (clone_flags & CLONE_NEWUSER) {
 349                 ret = create_user_ns(new);
 350                 if (ret < 0)
 351                         goto error_put;
 352         }
 353
 354 #ifdef CONFIG_KEYS
 355         /* new threads get their own thread keyrings if their parent already
 356          * had one */
 357         if (new->thread_keyring) {
 358                 key_put(new->thread_keyring);
 359                 new->thread_keyring = NULL;
 360                 if (clone_flags & CLONE_THREAD)
 361                         install_thread_keyring_to_cred(new);
 362         }
 363
 364         /* The process keyring is only shared between the threads in a process;
 365          * anything outside of those threads doesn't inherit.
 366          */
 367         if (!(clone_flags & CLONE_THREAD)) {
 368                 key_put(new->process_keyring);
 369                 new->process_keyring = NULL;
 370         }
 371 #endif
 372
 373         atomic_inc(&new->user->processes);
 374         p->cred = p->real_cred = get_cred(new);
 375         alter_cred_subscribers(new, 2);
 376         validate_creds(new);
 377         return 0;
 378
 379 error_put:
 380         put_cred(new);
 381         return ret;
 382 }
 383
 384 static bool cred_cap_issubset(const struct cred *set, const struct cred *subset)
 385 {
 386         const struct user_namespace *set_ns = set->user_ns;
 387         const struct user_namespace *subset_ns = subset->user_ns;
 388
 389         /* If the two credentials are in the same user namespace see if
 390          * the capabilities of subset are a subset of set.
 391          */
 392         if (set_ns == subset_ns)
 393                 return cap_issubset(subset->cap_permitted, set->cap_permitted);
 394
 395         /* The credentials are in a different user namespaces
 396          * therefore one is a subset of the other only if a set is an
 397          * ancestor of subset and set->euid is owner of subset or one
 398          * of subsets ancestors.
 399          */
 400         for (;subset_ns != &init_user_ns; subset_ns = subset_ns->parent) {
 401                 if ((set_ns == subset_ns->parent)  &&
 402                     uid_eq(subset_ns->owner, set->euid))
 403                         return true;
 404         }
 405
 406         return false;
 407 }
 408
 409 /**
 410  * commit_creds - Install new credentials upon the current task
 411  * @new: The credentials to be assigned
 412  *
 413  * Install a new set of credentials to the current task, using RCU to replace
 414  * the old set.  Both the objective and the subjective credentials pointers are
 415  * updated.  This function may not be called if the subjective credentials are
 416  * in an overridden state.
 417  *
 418  * This function eats the caller's reference to the new credentials.
 419  *
 420  * Always returns 0 thus allowing this function to be tail-called at the end
 421  * of, say, sys_setgid().
 422  */
 423 int commit_creds(struct cred *new)
 424 {
 425         struct task_struct *task = current;
 426         const struct cred *old = task->real_cred;
 427
 428         kdebug("commit_creds(%p{%d,%d})", new,
 429                atomic_read(&new->usage),
 430                read_cred_subscribers(new));
 431
 432         BUG_ON(task->cred != old);
 433 #ifdef CONFIG_DEBUG_CREDENTIALS
 434         BUG_ON(read_cred_subscribers(old) < 2);
 435         validate_creds(old);
 436         validate_creds(new);
 437 #endif
 438         BUG_ON(atomic_read(&new->usage) < 1);
 439
 440         get_cred(new); /* we will require a ref for the subj creds too */
 441
 442         /* dumpability changes */
 443         if (!uid_eq(old->euid, new->euid) ||
 444             !gid_eq(old->egid, new->egid) ||
 445             !uid_eq(old->fsuid, new->fsuid) ||
 446             !gid_eq(old->fsgid, new->fsgid) ||
 447             !cred_cap_issubset(old, new)) {
 448                 if (task->mm)
 449                         set_dumpable(task->mm, suid_dumpable);
 450                 task->pdeath_signal = 0;
 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), 0,
 574                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, 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         if (!uid_valid(inode->i_uid) || !gid_valid(inode->i_gid))
 694                 return -EINVAL;
 695         new->fsuid = inode->i_uid;
 696         new->fsgid = inode->i_gid;
 697         return security_kernel_create_files_as(new, inode);
 698 }
 699 EXPORT_SYMBOL(set_create_files_as);
 700
 701 #ifdef CONFIG_DEBUG_CREDENTIALS
 702
 703 bool creds_are_invalid(const struct cred *cred)
 704 {
 705         if (cred->magic != CRED_MAGIC)
 706                 return true;
 707 #ifdef CONFIG_SECURITY_SELINUX
 708         /*
 709          * cred->security == NULL if security_cred_alloc_blank() or
 710          * security_prepare_creds() returned an error.
 711          */
 712         if (selinux_is_enabled() && cred->security) {
 713                 if ((unsigned long) cred->security < PAGE_SIZE)
 714                         return true;
 715                 if ((*(u32 *)cred->security & 0xffffff00) ==
 716                     (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
 717                         return true;
 718         }
 719 #endif
 720         return false;
 721 }
 722 EXPORT_SYMBOL(creds_are_invalid);
 723
 724 /*
 725  * dump invalid credentials
 726  */
 727 static void dump_invalid_creds(const struct cred *cred, const char *label,
 728                                const struct task_struct *tsk)
 729 {
 730         printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
 731                label, cred,
 732                cred == &init_cred ? "[init]" : "",
 733                cred == tsk->real_cred ? "[real]" : "",
 734                cred == tsk->cred ? "[eff]" : "");
 735         printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
 736                cred->magic, cred->put_addr);
 737         printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
 738                atomic_read(&cred->usage),
 739                read_cred_subscribers(cred));
 740         printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
 741                 from_kuid_munged(&init_user_ns, cred->uid),
 742                 from_kuid_munged(&init_user_ns, cred->euid),
 743                 from_kuid_munged(&init_user_ns, cred->suid),
 744                 from_kuid_munged(&init_user_ns, cred->fsuid));
 745         printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
 746                 from_kgid_munged(&init_user_ns, cred->gid),
 747                 from_kgid_munged(&init_user_ns, cred->egid),
 748                 from_kgid_munged(&init_user_ns, cred->sgid),
 749                 from_kgid_munged(&init_user_ns, cred->fsgid));
 750 #ifdef CONFIG_SECURITY
 751         printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
 752         if ((unsigned long) cred->security >= PAGE_SIZE &&
 753             (((unsigned long) cred->security & 0xffffff00) !=
 754              (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
 755                 printk(KERN_ERR "CRED: ->security {%x, %x}\n",
 756                        ((u32*)cred->security)[0],
 757                        ((u32*)cred->security)[1]);
 758 #endif
 759 }
 760
 761 /*
 762  * report use of invalid credentials
 763  */
 764 void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
 765 {
 766         printk(KERN_ERR "CRED: Invalid credentials\n");
 767         printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 768         dump_invalid_creds(cred, "Specified", current);
 769         BUG();
 770 }
 771 EXPORT_SYMBOL(__invalid_creds);
 772
 773 /*
 774  * check the credentials on a process
 775  */
 776 void __validate_process_creds(struct task_struct *tsk,
 777                               const char *file, unsigned line)
 778 {
 779         if (tsk->cred == tsk->real_cred) {
 780                 if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
 781                              creds_are_invalid(tsk->cred)))
 782                         goto invalid_creds;
 783         } else {
 784                 if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
 785                              read_cred_subscribers(tsk->cred) < 1 ||
 786                              creds_are_invalid(tsk->real_cred) ||
 787                              creds_are_invalid(tsk->cred)))
 788                         goto invalid_creds;
 789         }
 790         return;
 791
 792 invalid_creds:
 793         printk(KERN_ERR "CRED: Invalid process credentials\n");
 794         printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 795
 796         dump_invalid_creds(tsk->real_cred, "Real", tsk);
 797         if (tsk->cred != tsk->real_cred)
 798                 dump_invalid_creds(tsk->cred, "Effective", tsk);
 799         else
 800                 printk(KERN_ERR "CRED: Effective creds == Real creds\n");
 801         BUG();
 802 }
 803 EXPORT_SYMBOL(__validate_process_creds);
 804
 805 /*
 806  * check creds for do_exit()
 807  */
 808 void validate_creds_for_do_exit(struct task_struct *tsk)
 809 {
 810         kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
 811                tsk->real_cred, tsk->cred,
 812                atomic_read(&tsk->cred->usage),
 813                read_cred_subscribers(tsk->cred));
 814
 815         __validate_process_creds(tsk, __FILE__, __LINE__);
 816 }
 817
 818 #endif /* CONFIG_DEBUG_CREDENTIALS */