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 common credentials for the initial task's thread group 34 */ 35 #ifdef CONFIG_KEYS 36 static struct thread_group_cred init_tgcred = { 37 .usage = ATOMIC_INIT(2), 38 .tgid = 0, 39 .lock = __SPIN_LOCK_UNLOCKED(init_cred.tgcred.lock), 40 }; 41 #endif 42 43 /* 44 * The initial credentials for the initial task 45 */ 46 struct cred init_cred = { 47 .usage = ATOMIC_INIT(4), 48 #ifdef CONFIG_DEBUG_CREDENTIALS 49 .subscribers = ATOMIC_INIT(2), 50 .magic = CRED_MAGIC, 51 #endif 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 #ifdef CONFIG_KEYS 61 .tgcred = &init_tgcred, 62 #endif 63 }; 64 65 static inline void set_cred_subscribers(struct cred *cred, int n) 66 { 67 #ifdef CONFIG_DEBUG_CREDENTIALS 68 atomic_set(&cred->subscribers, n); 69 #endif 70 } 71 72 static inline int read_cred_subscribers(const struct cred *cred) 73 { 74 #ifdef CONFIG_DEBUG_CREDENTIALS 75 return atomic_read(&cred->subscribers); 76 #else 77 return 0; 78 #endif 79 } 80 81 static inline void alter_cred_subscribers(const struct cred *_cred, int n) 82 { 83 #ifdef CONFIG_DEBUG_CREDENTIALS 84 struct cred *cred = (struct cred *) _cred; 85 86 atomic_add(n, &cred->subscribers); 87 #endif 88 } 89 90 /* 91 * Dispose of the shared task group credentials 92 */ 93 #ifdef CONFIG_KEYS 94 static void release_tgcred_rcu(struct rcu_head *rcu) 95 { 96 struct thread_group_cred *tgcred = 97 container_of(rcu, struct thread_group_cred, rcu); 98 99 BUG_ON(atomic_read(&tgcred->usage) != 0); 100 101 key_put(tgcred->session_keyring); 102 key_put(tgcred->process_keyring); 103 kfree(tgcred); 104 } 105 #endif 106 107 /* 108 * Release a set of thread group credentials. 109 */ 110 static void release_tgcred(struct cred *cred) 111 { 112 #ifdef CONFIG_KEYS 113 struct thread_group_cred *tgcred = cred->tgcred; 114 115 if (atomic_dec_and_test(&tgcred->usage)) 116 call_rcu(&tgcred->rcu, release_tgcred_rcu); 117 #endif 118 } 119 120 /* 121 * The RCU callback to actually dispose of a set of credentials 122 */ 123 static void put_cred_rcu(struct rcu_head *rcu) 124 { 125 struct cred *cred = container_of(rcu, struct cred, rcu); 126 127 kdebug("put_cred_rcu(%p)", cred); 128 129 #ifdef CONFIG_DEBUG_CREDENTIALS 130 if (cred->magic != CRED_MAGIC_DEAD || 131 atomic_read(&cred->usage) != 0 || 132 read_cred_subscribers(cred) != 0) 133 panic("CRED: put_cred_rcu() sees %p with" 134 " mag %x, put %p, usage %d, subscr %d\n", 135 cred, cred->magic, cred->put_addr, 136 atomic_read(&cred->usage), 137 read_cred_subscribers(cred)); 138 #else 139 if (atomic_read(&cred->usage) != 0) 140 panic("CRED: put_cred_rcu() sees %p with usage %d\n", 141 cred, atomic_read(&cred->usage)); 142 #endif 143 144 security_cred_free(cred); 145 key_put(cred->thread_keyring); 146 key_put(cred->request_key_auth); 147 release_tgcred(cred); 148 if (cred->group_info) 149 put_group_info(cred->group_info); 150 free_uid(cred->user); 151 kmem_cache_free(cred_jar, cred); 152 } 153 154 /** 155 * __put_cred - Destroy a set of credentials 156 * @cred: The record to release 157 * 158 * Destroy a set of credentials on which no references remain. 159 */ 160 void __put_cred(struct cred *cred) 161 { 162 kdebug("__put_cred(%p{%d,%d})", cred, 163 atomic_read(&cred->usage), 164 read_cred_subscribers(cred)); 165 166 BUG_ON(atomic_read(&cred->usage) != 0); 167 #ifdef CONFIG_DEBUG_CREDENTIALS 168 BUG_ON(read_cred_subscribers(cred) != 0); 169 cred->magic = CRED_MAGIC_DEAD; 170 cred->put_addr = __builtin_return_address(0); 171 #endif 172 BUG_ON(cred == current->cred); 173 BUG_ON(cred == current->real_cred); 174 175 call_rcu(&cred->rcu, put_cred_rcu); 176 } 177 EXPORT_SYMBOL(__put_cred); 178 179 /* 180 * Clean up a task's credentials when it exits 181 */ 182 void exit_creds(struct task_struct *tsk) 183 { 184 struct cred *cred; 185 186 kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred, 187 atomic_read(&tsk->cred->usage), 188 read_cred_subscribers(tsk->cred)); 189 190 cred = (struct cred *) tsk->real_cred; 191 tsk->real_cred = NULL; 192 validate_creds(cred); 193 alter_cred_subscribers(cred, -1); 194 put_cred(cred); 195 196 cred = (struct cred *) tsk->cred; 197 tsk->cred = NULL; 198 validate_creds(cred); 199 alter_cred_subscribers(cred, -1); 200 put_cred(cred); 201 202 cred = (struct cred *) tsk->replacement_session_keyring; 203 if (cred) { 204 tsk->replacement_session_keyring = NULL; 205 validate_creds(cred); 206 put_cred(cred); 207 } 208 } 209 210 /** 211 * get_task_cred - Get another task's objective credentials 212 * @task: The task to query 213 * 214 * Get the objective credentials of a task, pinning them so that they can't go 215 * away. Accessing a task's credentials directly is not permitted. 216 * 217 * The caller must also make sure task doesn't get deleted, either by holding a 218 * ref on task or by holding tasklist_lock to prevent it from being unlinked. 219 */ 220 const struct cred *get_task_cred(struct task_struct *task) 221 { 222 const struct cred *cred; 223 224 rcu_read_lock(); 225 226 do { 227 cred = __task_cred((task)); 228 BUG_ON(!cred); 229 } while (!atomic_inc_not_zero(&((struct cred *)cred)->usage)); 230 231 rcu_read_unlock(); 232 return cred; 233 } 234 235 /* 236 * Allocate blank credentials, such that the credentials can be filled in at a 237 * later date without risk of ENOMEM. 238 */ 239 struct cred *cred_alloc_blank(void) 240 { 241 struct cred *new; 242 243 new = kmem_cache_zalloc(cred_jar, GFP_KERNEL); 244 if (!new) 245 return NULL; 246 247 #ifdef CONFIG_KEYS 248 new->tgcred = kzalloc(sizeof(*new->tgcred), GFP_KERNEL); 249 if (!new->tgcred) { 250 kmem_cache_free(cred_jar, new); 251 return NULL; 252 } 253 atomic_set(&new->tgcred->usage, 1); 254 #endif 255 256 atomic_set(&new->usage, 1); 257 #ifdef CONFIG_DEBUG_CREDENTIALS 258 new->magic = CRED_MAGIC; 259 #endif 260 261 if (security_cred_alloc_blank(new, GFP_KERNEL) < 0) 262 goto error; 263 264 return new; 265 266 error: 267 abort_creds(new); 268 return NULL; 269 } 270 271 /** 272 * prepare_creds - Prepare a new set of credentials for modification 273 * 274 * Prepare a new set of task credentials for modification. A task's creds 275 * shouldn't generally be modified directly, therefore this function is used to 276 * prepare a new copy, which the caller then modifies and then commits by 277 * calling commit_creds(). 278 * 279 * Preparation involves making a copy of the objective creds for modification. 280 * 281 * Returns a pointer to the new creds-to-be if successful, NULL otherwise. 282 * 283 * Call commit_creds() or abort_creds() to clean up. 284 */ 285 struct cred *prepare_creds(void) 286 { 287 struct task_struct *task = current; 288 const struct cred *old; 289 struct cred *new; 290 291 validate_process_creds(); 292 293 new = kmem_cache_alloc(cred_jar, GFP_KERNEL); 294 if (!new) 295 return NULL; 296 297 kdebug("prepare_creds() alloc %p", new); 298 299 old = task->cred; 300 memcpy(new, old, sizeof(struct cred)); 301 302 atomic_set(&new->usage, 1); 303 set_cred_subscribers(new, 0); 304 get_group_info(new->group_info); 305 get_uid(new->user); 306 307 #ifdef CONFIG_KEYS 308 key_get(new->thread_keyring); 309 key_get(new->request_key_auth); 310 atomic_inc(&new->tgcred->usage); 311 #endif 312 313 #ifdef CONFIG_SECURITY 314 new->security = NULL; 315 #endif 316 317 if (security_prepare_creds(new, old, GFP_KERNEL) < 0) 318 goto error; 319 validate_creds(new); 320 return new; 321 322 error: 323 abort_creds(new); 324 return NULL; 325 } 326 EXPORT_SYMBOL(prepare_creds); 327 328 /* 329 * Prepare credentials for current to perform an execve() 330 * - The caller must hold ->cred_guard_mutex 331 */ 332 struct cred *prepare_exec_creds(void) 333 { 334 struct thread_group_cred *tgcred = NULL; 335 struct cred *new; 336 337 #ifdef CONFIG_KEYS 338 tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL); 339 if (!tgcred) 340 return NULL; 341 #endif 342 343 new = prepare_creds(); 344 if (!new) { 345 kfree(tgcred); 346 return new; 347 } 348 349 #ifdef CONFIG_KEYS 350 /* newly exec'd tasks don't get a thread keyring */ 351 key_put(new->thread_keyring); 352 new->thread_keyring = NULL; 353 354 /* create a new per-thread-group creds for all this set of threads to 355 * share */ 356 memcpy(tgcred, new->tgcred, sizeof(struct thread_group_cred)); 357 358 atomic_set(&tgcred->usage, 1); 359 spin_lock_init(&tgcred->lock); 360 361 /* inherit the session keyring; new process keyring */ 362 key_get(tgcred->session_keyring); 363 tgcred->process_keyring = NULL; 364 365 release_tgcred(new); 366 new->tgcred = tgcred; 367 #endif 368 369 return new; 370 } 371 372 /* 373 * Copy credentials for the new process created by fork() 374 * 375 * We share if we can, but under some circumstances we have to generate a new 376 * set. 377 * 378 * The new process gets the current process's subjective credentials as its 379 * objective and subjective credentials 380 */ 381 int copy_creds(struct task_struct *p, unsigned long clone_flags) 382 { 383 #ifdef CONFIG_KEYS 384 struct thread_group_cred *tgcred; 385 #endif 386 struct cred *new; 387 int ret; 388 389 p->replacement_session_keyring = NULL; 390 391 if ( 392 #ifdef CONFIG_KEYS 393 !p->cred->thread_keyring && 394 #endif 395 clone_flags & CLONE_THREAD 396 ) { 397 p->real_cred = get_cred(p->cred); 398 get_cred(p->cred); 399 alter_cred_subscribers(p->cred, 2); 400 kdebug("share_creds(%p{%d,%d})", 401 p->cred, atomic_read(&p->cred->usage), 402 read_cred_subscribers(p->cred)); 403 atomic_inc(&p->cred->user->processes); 404 return 0; 405 } 406 407 new = prepare_creds(); 408 if (!new) 409 return -ENOMEM; 410 411 if (clone_flags & CLONE_NEWUSER) { 412 ret = create_user_ns(new); 413 if (ret < 0) 414 goto error_put; 415 } 416 417 /* cache user_ns in cred. Doesn't need a refcount because it will 418 * stay pinned by cred->user 419 */ 420 new->user_ns = new->user->user_ns; 421 422 #ifdef CONFIG_KEYS 423 /* new threads get their own thread keyrings if their parent already 424 * had one */ 425 if (new->thread_keyring) { 426 key_put(new->thread_keyring); 427 new->thread_keyring = NULL; 428 if (clone_flags & CLONE_THREAD) 429 install_thread_keyring_to_cred(new); 430 } 431 432 /* we share the process and session keyrings between all the threads in 433 * a process - this is slightly icky as we violate COW credentials a 434 * bit */ 435 if (!(clone_flags & CLONE_THREAD)) { 436 tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL); 437 if (!tgcred) { 438 ret = -ENOMEM; 439 goto error_put; 440 } 441 atomic_set(&tgcred->usage, 1); 442 spin_lock_init(&tgcred->lock); 443 tgcred->process_keyring = NULL; 444 tgcred->session_keyring = key_get(new->tgcred->session_keyring); 445 446 release_tgcred(new); 447 new->tgcred = tgcred; 448 } 449 #endif 450 451 atomic_inc(&new->user->processes); 452 p->cred = p->real_cred = get_cred(new); 453 alter_cred_subscribers(new, 2); 454 validate_creds(new); 455 return 0; 456 457 error_put: 458 put_cred(new); 459 return ret; 460 } 461 462 /** 463 * commit_creds - Install new credentials upon the current task 464 * @new: The credentials to be assigned 465 * 466 * Install a new set of credentials to the current task, using RCU to replace 467 * the old set. Both the objective and the subjective credentials pointers are 468 * updated. This function may not be called if the subjective credentials are 469 * in an overridden state. 470 * 471 * This function eats the caller's reference to the new credentials. 472 * 473 * Always returns 0 thus allowing this function to be tail-called at the end 474 * of, say, sys_setgid(). 475 */ 476 int commit_creds(struct cred *new) 477 { 478 struct task_struct *task = current; 479 const struct cred *old = task->real_cred; 480 481 kdebug("commit_creds(%p{%d,%d})", new, 482 atomic_read(&new->usage), 483 read_cred_subscribers(new)); 484 485 BUG_ON(task->cred != old); 486 #ifdef CONFIG_DEBUG_CREDENTIALS 487 BUG_ON(read_cred_subscribers(old) < 2); 488 validate_creds(old); 489 validate_creds(new); 490 #endif 491 BUG_ON(atomic_read(&new->usage) < 1); 492 493 get_cred(new); /* we will require a ref for the subj creds too */ 494 495 /* dumpability changes */ 496 if (old->euid != new->euid || 497 old->egid != new->egid || 498 old->fsuid != new->fsuid || 499 old->fsgid != new->fsgid || 500 !cap_issubset(new->cap_permitted, old->cap_permitted)) { 501 if (task->mm) 502 set_dumpable(task->mm, suid_dumpable); 503 task->pdeath_signal = 0; 504 smp_wmb(); 505 } 506 507 /* alter the thread keyring */ 508 if (new->fsuid != old->fsuid) 509 key_fsuid_changed(task); 510 if (new->fsgid != old->fsgid) 511 key_fsgid_changed(task); 512 513 /* do it 514 * RLIMIT_NPROC limits on user->processes have already been checked 515 * in set_user(). 516 */ 517 alter_cred_subscribers(new, 2); 518 if (new->user != old->user) 519 atomic_inc(&new->user->processes); 520 rcu_assign_pointer(task->real_cred, new); 521 rcu_assign_pointer(task->cred, new); 522 if (new->user != old->user) 523 atomic_dec(&old->user->processes); 524 alter_cred_subscribers(old, -2); 525 526 /* send notifications */ 527 if (new->uid != old->uid || 528 new->euid != old->euid || 529 new->suid != old->suid || 530 new->fsuid != old->fsuid) 531 proc_id_connector(task, PROC_EVENT_UID); 532 533 if (new->gid != old->gid || 534 new->egid != old->egid || 535 new->sgid != old->sgid || 536 new->fsgid != old->fsgid) 537 proc_id_connector(task, PROC_EVENT_GID); 538 539 /* release the old obj and subj refs both */ 540 put_cred(old); 541 put_cred(old); 542 return 0; 543 } 544 EXPORT_SYMBOL(commit_creds); 545 546 /** 547 * abort_creds - Discard a set of credentials and unlock the current task 548 * @new: The credentials that were going to be applied 549 * 550 * Discard a set of credentials that were under construction and unlock the 551 * current task. 552 */ 553 void abort_creds(struct cred *new) 554 { 555 kdebug("abort_creds(%p{%d,%d})", new, 556 atomic_read(&new->usage), 557 read_cred_subscribers(new)); 558 559 #ifdef CONFIG_DEBUG_CREDENTIALS 560 BUG_ON(read_cred_subscribers(new) != 0); 561 #endif 562 BUG_ON(atomic_read(&new->usage) < 1); 563 put_cred(new); 564 } 565 EXPORT_SYMBOL(abort_creds); 566 567 /** 568 * override_creds - Override the current process's subjective credentials 569 * @new: The credentials to be assigned 570 * 571 * Install a set of temporary override subjective credentials on the current 572 * process, returning the old set for later reversion. 573 */ 574 const struct cred *override_creds(const struct cred *new) 575 { 576 const struct cred *old = current->cred; 577 578 kdebug("override_creds(%p{%d,%d})", new, 579 atomic_read(&new->usage), 580 read_cred_subscribers(new)); 581 582 validate_creds(old); 583 validate_creds(new); 584 get_cred(new); 585 alter_cred_subscribers(new, 1); 586 rcu_assign_pointer(current->cred, new); 587 alter_cred_subscribers(old, -1); 588 589 kdebug("override_creds() = %p{%d,%d}", old, 590 atomic_read(&old->usage), 591 read_cred_subscribers(old)); 592 return old; 593 } 594 EXPORT_SYMBOL(override_creds); 595 596 /** 597 * revert_creds - Revert a temporary subjective credentials override 598 * @old: The credentials to be restored 599 * 600 * Revert a temporary set of override subjective credentials to an old set, 601 * discarding the override set. 602 */ 603 void revert_creds(const struct cred *old) 604 { 605 const struct cred *override = current->cred; 606 607 kdebug("revert_creds(%p{%d,%d})", old, 608 atomic_read(&old->usage), 609 read_cred_subscribers(old)); 610 611 validate_creds(old); 612 validate_creds(override); 613 alter_cred_subscribers(old, 1); 614 rcu_assign_pointer(current->cred, old); 615 alter_cred_subscribers(override, -1); 616 put_cred(override); 617 } 618 EXPORT_SYMBOL(revert_creds); 619 620 /* 621 * initialise the credentials stuff 622 */ 623 void __init cred_init(void) 624 { 625 /* allocate a slab in which we can store credentials */ 626 cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred), 627 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 628 } 629 630 /** 631 * prepare_kernel_cred - Prepare a set of credentials for a kernel service 632 * @daemon: A userspace daemon to be used as a reference 633 * 634 * Prepare a set of credentials for a kernel service. This can then be used to 635 * override a task's own credentials so that work can be done on behalf of that 636 * task that requires a different subjective context. 637 * 638 * @daemon is used to provide a base for the security record, but can be NULL. 639 * If @daemon is supplied, then the security data will be derived from that; 640 * otherwise they'll be set to 0 and no groups, full capabilities and no keys. 641 * 642 * The caller may change these controls afterwards if desired. 643 * 644 * Returns the new credentials or NULL if out of memory. 645 * 646 * Does not take, and does not return holding current->cred_replace_mutex. 647 */ 648 struct cred *prepare_kernel_cred(struct task_struct *daemon) 649 { 650 #ifdef CONFIG_KEYS 651 struct thread_group_cred *tgcred; 652 #endif 653 const struct cred *old; 654 struct cred *new; 655 656 new = kmem_cache_alloc(cred_jar, GFP_KERNEL); 657 if (!new) 658 return NULL; 659 660 #ifdef CONFIG_KEYS 661 tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL); 662 if (!tgcred) { 663 kmem_cache_free(cred_jar, new); 664 return NULL; 665 } 666 #endif 667 668 kdebug("prepare_kernel_cred() alloc %p", new); 669 670 if (daemon) 671 old = get_task_cred(daemon); 672 else 673 old = get_cred(&init_cred); 674 675 validate_creds(old); 676 677 *new = *old; 678 atomic_set(&new->usage, 1); 679 set_cred_subscribers(new, 0); 680 get_uid(new->user); 681 get_group_info(new->group_info); 682 683 #ifdef CONFIG_KEYS 684 atomic_set(&tgcred->usage, 1); 685 spin_lock_init(&tgcred->lock); 686 tgcred->process_keyring = NULL; 687 tgcred->session_keyring = NULL; 688 new->tgcred = tgcred; 689 new->request_key_auth = NULL; 690 new->thread_keyring = NULL; 691 new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING; 692 #endif 693 694 #ifdef CONFIG_SECURITY 695 new->security = NULL; 696 #endif 697 if (security_prepare_creds(new, old, GFP_KERNEL) < 0) 698 goto error; 699 700 put_cred(old); 701 validate_creds(new); 702 return new; 703 704 error: 705 put_cred(new); 706 put_cred(old); 707 return NULL; 708 } 709 EXPORT_SYMBOL(prepare_kernel_cred); 710 711 /** 712 * set_security_override - Set the security ID in a set of credentials 713 * @new: The credentials to alter 714 * @secid: The LSM security ID to set 715 * 716 * Set the LSM security ID in a set of credentials so that the subjective 717 * security is overridden when an alternative set of credentials is used. 718 */ 719 int set_security_override(struct cred *new, u32 secid) 720 { 721 return security_kernel_act_as(new, secid); 722 } 723 EXPORT_SYMBOL(set_security_override); 724 725 /** 726 * set_security_override_from_ctx - Set the security ID in a set of credentials 727 * @new: The credentials to alter 728 * @secctx: The LSM security context to generate the security ID from. 729 * 730 * Set the LSM security ID in a set of credentials so that the subjective 731 * security is overridden when an alternative set of credentials is used. The 732 * security ID is specified in string form as a security context to be 733 * interpreted by the LSM. 734 */ 735 int set_security_override_from_ctx(struct cred *new, const char *secctx) 736 { 737 u32 secid; 738 int ret; 739 740 ret = security_secctx_to_secid(secctx, strlen(secctx), &secid); 741 if (ret < 0) 742 return ret; 743 744 return set_security_override(new, secid); 745 } 746 EXPORT_SYMBOL(set_security_override_from_ctx); 747 748 /** 749 * set_create_files_as - Set the LSM file create context in a set of credentials 750 * @new: The credentials to alter 751 * @inode: The inode to take the context from 752 * 753 * Change the LSM file creation context in a set of credentials to be the same 754 * as the object context of the specified inode, so that the new inodes have 755 * the same MAC context as that inode. 756 */ 757 int set_create_files_as(struct cred *new, struct inode *inode) 758 { 759 new->fsuid = inode->i_uid; 760 new->fsgid = inode->i_gid; 761 return security_kernel_create_files_as(new, inode); 762 } 763 EXPORT_SYMBOL(set_create_files_as); 764 765 #ifdef CONFIG_DEBUG_CREDENTIALS 766 767 bool creds_are_invalid(const struct cred *cred) 768 { 769 if (cred->magic != CRED_MAGIC) 770 return true; 771 #ifdef CONFIG_SECURITY_SELINUX 772 /* 773 * cred->security == NULL if security_cred_alloc_blank() or 774 * security_prepare_creds() returned an error. 775 */ 776 if (selinux_is_enabled() && cred->security) { 777 if ((unsigned long) cred->security < PAGE_SIZE) 778 return true; 779 if ((*(u32 *)cred->security & 0xffffff00) == 780 (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)) 781 return true; 782 } 783 #endif 784 return false; 785 } 786 EXPORT_SYMBOL(creds_are_invalid); 787 788 /* 789 * dump invalid credentials 790 */ 791 static void dump_invalid_creds(const struct cred *cred, const char *label, 792 const struct task_struct *tsk) 793 { 794 printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n", 795 label, cred, 796 cred == &init_cred ? "[init]" : "", 797 cred == tsk->real_cred ? "[real]" : "", 798 cred == tsk->cred ? "[eff]" : ""); 799 printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n", 800 cred->magic, cred->put_addr); 801 printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n", 802 atomic_read(&cred->usage), 803 read_cred_subscribers(cred)); 804 printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n", 805 cred->uid, cred->euid, cred->suid, cred->fsuid); 806 printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n", 807 cred->gid, cred->egid, cred->sgid, cred->fsgid); 808 #ifdef CONFIG_SECURITY 809 printk(KERN_ERR "CRED: ->security is %p\n", cred->security); 810 if ((unsigned long) cred->security >= PAGE_SIZE && 811 (((unsigned long) cred->security & 0xffffff00) != 812 (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))) 813 printk(KERN_ERR "CRED: ->security {%x, %x}\n", 814 ((u32*)cred->security)[0], 815 ((u32*)cred->security)[1]); 816 #endif 817 } 818 819 /* 820 * report use of invalid credentials 821 */ 822 void __invalid_creds(const struct cred *cred, const char *file, unsigned line) 823 { 824 printk(KERN_ERR "CRED: Invalid credentials\n"); 825 printk(KERN_ERR "CRED: At %s:%u\n", file, line); 826 dump_invalid_creds(cred, "Specified", current); 827 BUG(); 828 } 829 EXPORT_SYMBOL(__invalid_creds); 830 831 /* 832 * check the credentials on a process 833 */ 834 void __validate_process_creds(struct task_struct *tsk, 835 const char *file, unsigned line) 836 { 837 if (tsk->cred == tsk->real_cred) { 838 if (unlikely(read_cred_subscribers(tsk->cred) < 2 || 839 creds_are_invalid(tsk->cred))) 840 goto invalid_creds; 841 } else { 842 if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 || 843 read_cred_subscribers(tsk->cred) < 1 || 844 creds_are_invalid(tsk->real_cred) || 845 creds_are_invalid(tsk->cred))) 846 goto invalid_creds; 847 } 848 return; 849 850 invalid_creds: 851 printk(KERN_ERR "CRED: Invalid process credentials\n"); 852 printk(KERN_ERR "CRED: At %s:%u\n", file, line); 853 854 dump_invalid_creds(tsk->real_cred, "Real", tsk); 855 if (tsk->cred != tsk->real_cred) 856 dump_invalid_creds(tsk->cred, "Effective", tsk); 857 else 858 printk(KERN_ERR "CRED: Effective creds == Real creds\n"); 859 BUG(); 860 } 861 EXPORT_SYMBOL(__validate_process_creds); 862 863 /* 864 * check creds for do_exit() 865 */ 866 void validate_creds_for_do_exit(struct task_struct *tsk) 867 { 868 kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})", 869 tsk->real_cred, tsk->cred, 870 atomic_read(&tsk->cred->usage), 871 read_cred_subscribers(tsk->cred)); 872 873 __validate_process_creds(tsk, __FILE__, __LINE__); 874 } 875 876 #endif /* CONFIG_DEBUG_CREDENTIALS */ 877