1 /* 2 * device_cgroup.c - device cgroup subsystem 3 * 4 * Copyright 2007 IBM Corp 5 */ 6 7 #include <linux/device_cgroup.h> 8 #include <linux/cgroup.h> 9 #include <linux/ctype.h> 10 #include <linux/list.h> 11 #include <linux/uaccess.h> 12 #include <linux/seq_file.h> 13 #include <linux/slab.h> 14 #include <linux/rcupdate.h> 15 #include <linux/mutex.h> 16 17 #define ACC_MKNOD 1 18 #define ACC_READ 2 19 #define ACC_WRITE 4 20 #define ACC_MASK (ACC_MKNOD | ACC_READ | ACC_WRITE) 21 22 #define DEV_BLOCK 1 23 #define DEV_CHAR 2 24 #define DEV_ALL 4 /* this represents all devices */ 25 26 static DEFINE_MUTEX(devcgroup_mutex); 27 28 enum devcg_behavior { 29 DEVCG_DEFAULT_NONE, 30 DEVCG_DEFAULT_ALLOW, 31 DEVCG_DEFAULT_DENY, 32 }; 33 34 /* 35 * exception list locking rules: 36 * hold devcgroup_mutex for update/read. 37 * hold rcu_read_lock() for read. 38 */ 39 40 struct dev_exception_item { 41 u32 major, minor; 42 short type; 43 short access; 44 struct list_head list; 45 struct rcu_head rcu; 46 }; 47 48 struct dev_cgroup { 49 struct cgroup_subsys_state css; 50 struct list_head exceptions; 51 enum devcg_behavior behavior; 52 /* temporary list for pending propagation operations */ 53 struct list_head propagate_pending; 54 }; 55 56 static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s) 57 { 58 return container_of(s, struct dev_cgroup, css); 59 } 60 61 static inline struct dev_cgroup *cgroup_to_devcgroup(struct cgroup *cgroup) 62 { 63 return css_to_devcgroup(cgroup_subsys_state(cgroup, devices_subsys_id)); 64 } 65 66 static inline struct dev_cgroup *task_devcgroup(struct task_struct *task) 67 { 68 return css_to_devcgroup(task_subsys_state(task, devices_subsys_id)); 69 } 70 71 struct cgroup_subsys devices_subsys; 72 73 static int devcgroup_can_attach(struct cgroup *new_cgrp, 74 struct cgroup_taskset *set) 75 { 76 struct task_struct *task = cgroup_taskset_first(set); 77 78 if (current != task && !capable(CAP_SYS_ADMIN)) 79 return -EPERM; 80 return 0; 81 } 82 83 /* 84 * called under devcgroup_mutex 85 */ 86 static int dev_exceptions_copy(struct list_head *dest, struct list_head *orig) 87 { 88 struct dev_exception_item *ex, *tmp, *new; 89 90 lockdep_assert_held(&devcgroup_mutex); 91 92 list_for_each_entry(ex, orig, list) { 93 new = kmemdup(ex, sizeof(*ex), GFP_KERNEL); 94 if (!new) 95 goto free_and_exit; 96 list_add_tail(&new->list, dest); 97 } 98 99 return 0; 100 101 free_and_exit: 102 list_for_each_entry_safe(ex, tmp, dest, list) { 103 list_del(&ex->list); 104 kfree(ex); 105 } 106 return -ENOMEM; 107 } 108 109 /* 110 * called under devcgroup_mutex 111 */ 112 static int dev_exception_add(struct dev_cgroup *dev_cgroup, 113 struct dev_exception_item *ex) 114 { 115 struct dev_exception_item *excopy, *walk; 116 117 lockdep_assert_held(&devcgroup_mutex); 118 119 excopy = kmemdup(ex, sizeof(*ex), GFP_KERNEL); 120 if (!excopy) 121 return -ENOMEM; 122 123 list_for_each_entry(walk, &dev_cgroup->exceptions, list) { 124 if (walk->type != ex->type) 125 continue; 126 if (walk->major != ex->major) 127 continue; 128 if (walk->minor != ex->minor) 129 continue; 130 131 walk->access |= ex->access; 132 kfree(excopy); 133 excopy = NULL; 134 } 135 136 if (excopy != NULL) 137 list_add_tail_rcu(&excopy->list, &dev_cgroup->exceptions); 138 return 0; 139 } 140 141 /* 142 * called under devcgroup_mutex 143 */ 144 static void dev_exception_rm(struct dev_cgroup *dev_cgroup, 145 struct dev_exception_item *ex) 146 { 147 struct dev_exception_item *walk, *tmp; 148 149 lockdep_assert_held(&devcgroup_mutex); 150 151 list_for_each_entry_safe(walk, tmp, &dev_cgroup->exceptions, list) { 152 if (walk->type != ex->type) 153 continue; 154 if (walk->major != ex->major) 155 continue; 156 if (walk->minor != ex->minor) 157 continue; 158 159 walk->access &= ~ex->access; 160 if (!walk->access) { 161 list_del_rcu(&walk->list); 162 kfree_rcu(walk, rcu); 163 } 164 } 165 } 166 167 static void __dev_exception_clean(struct dev_cgroup *dev_cgroup) 168 { 169 struct dev_exception_item *ex, *tmp; 170 171 list_for_each_entry_safe(ex, tmp, &dev_cgroup->exceptions, list) { 172 list_del_rcu(&ex->list); 173 kfree_rcu(ex, rcu); 174 } 175 } 176 177 /** 178 * dev_exception_clean - frees all entries of the exception list 179 * @dev_cgroup: dev_cgroup with the exception list to be cleaned 180 * 181 * called under devcgroup_mutex 182 */ 183 static void dev_exception_clean(struct dev_cgroup *dev_cgroup) 184 { 185 lockdep_assert_held(&devcgroup_mutex); 186 187 __dev_exception_clean(dev_cgroup); 188 } 189 190 static inline bool is_devcg_online(const struct dev_cgroup *devcg) 191 { 192 return (devcg->behavior != DEVCG_DEFAULT_NONE); 193 } 194 195 /** 196 * devcgroup_online - initializes devcgroup's behavior and exceptions based on 197 * parent's 198 * @cgroup: cgroup getting online 199 * returns 0 in case of success, error code otherwise 200 */ 201 static int devcgroup_online(struct cgroup *cgroup) 202 { 203 struct dev_cgroup *dev_cgroup, *parent_dev_cgroup = NULL; 204 int ret = 0; 205 206 mutex_lock(&devcgroup_mutex); 207 dev_cgroup = cgroup_to_devcgroup(cgroup); 208 if (cgroup->parent) 209 parent_dev_cgroup = cgroup_to_devcgroup(cgroup->parent); 210 211 if (parent_dev_cgroup == NULL) 212 dev_cgroup->behavior = DEVCG_DEFAULT_ALLOW; 213 else { 214 ret = dev_exceptions_copy(&dev_cgroup->exceptions, 215 &parent_dev_cgroup->exceptions); 216 if (!ret) 217 dev_cgroup->behavior = parent_dev_cgroup->behavior; 218 } 219 mutex_unlock(&devcgroup_mutex); 220 221 return ret; 222 } 223 224 static void devcgroup_offline(struct cgroup *cgroup) 225 { 226 struct dev_cgroup *dev_cgroup = cgroup_to_devcgroup(cgroup); 227 228 mutex_lock(&devcgroup_mutex); 229 dev_cgroup->behavior = DEVCG_DEFAULT_NONE; 230 mutex_unlock(&devcgroup_mutex); 231 } 232 233 /* 234 * called from kernel/cgroup.c with cgroup_lock() held. 235 */ 236 static struct cgroup_subsys_state *devcgroup_css_alloc(struct cgroup *cgroup) 237 { 238 struct dev_cgroup *dev_cgroup; 239 240 dev_cgroup = kzalloc(sizeof(*dev_cgroup), GFP_KERNEL); 241 if (!dev_cgroup) 242 return ERR_PTR(-ENOMEM); 243 INIT_LIST_HEAD(&dev_cgroup->exceptions); 244 INIT_LIST_HEAD(&dev_cgroup->propagate_pending); 245 dev_cgroup->behavior = DEVCG_DEFAULT_NONE; 246 247 return &dev_cgroup->css; 248 } 249 250 static void devcgroup_css_free(struct cgroup *cgroup) 251 { 252 struct dev_cgroup *dev_cgroup; 253 254 dev_cgroup = cgroup_to_devcgroup(cgroup); 255 __dev_exception_clean(dev_cgroup); 256 kfree(dev_cgroup); 257 } 258 259 #define DEVCG_ALLOW 1 260 #define DEVCG_DENY 2 261 #define DEVCG_LIST 3 262 263 #define MAJMINLEN 13 264 #define ACCLEN 4 265 266 static void set_access(char *acc, short access) 267 { 268 int idx = 0; 269 memset(acc, 0, ACCLEN); 270 if (access & ACC_READ) 271 acc[idx++] = 'r'; 272 if (access & ACC_WRITE) 273 acc[idx++] = 'w'; 274 if (access & ACC_MKNOD) 275 acc[idx++] = 'm'; 276 } 277 278 static char type_to_char(short type) 279 { 280 if (type == DEV_ALL) 281 return 'a'; 282 if (type == DEV_CHAR) 283 return 'c'; 284 if (type == DEV_BLOCK) 285 return 'b'; 286 return 'X'; 287 } 288 289 static void set_majmin(char *str, unsigned m) 290 { 291 if (m == ~0) 292 strcpy(str, "*"); 293 else 294 sprintf(str, "%u", m); 295 } 296 297 static int devcgroup_seq_read(struct cgroup *cgroup, struct cftype *cft, 298 struct seq_file *m) 299 { 300 struct dev_cgroup *devcgroup = cgroup_to_devcgroup(cgroup); 301 struct dev_exception_item *ex; 302 char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN]; 303 304 rcu_read_lock(); 305 /* 306 * To preserve the compatibility: 307 * - Only show the "all devices" when the default policy is to allow 308 * - List the exceptions in case the default policy is to deny 309 * This way, the file remains as a "whitelist of devices" 310 */ 311 if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) { 312 set_access(acc, ACC_MASK); 313 set_majmin(maj, ~0); 314 set_majmin(min, ~0); 315 seq_printf(m, "%c %s:%s %s\n", type_to_char(DEV_ALL), 316 maj, min, acc); 317 } else { 318 list_for_each_entry_rcu(ex, &devcgroup->exceptions, list) { 319 set_access(acc, ex->access); 320 set_majmin(maj, ex->major); 321 set_majmin(min, ex->minor); 322 seq_printf(m, "%c %s:%s %s\n", type_to_char(ex->type), 323 maj, min, acc); 324 } 325 } 326 rcu_read_unlock(); 327 328 return 0; 329 } 330 331 /** 332 * may_access - verifies if a new exception is part of what is allowed 333 * by a dev cgroup based on the default policy + 334 * exceptions. This is used to make sure a child cgroup 335 * won't have more privileges than its parent or to 336 * verify if a certain access is allowed. 337 * @dev_cgroup: dev cgroup to be tested against 338 * @refex: new exception 339 * @behavior: behavior of the exception 340 */ 341 static bool may_access(struct dev_cgroup *dev_cgroup, 342 struct dev_exception_item *refex, 343 enum devcg_behavior behavior) 344 { 345 struct dev_exception_item *ex; 346 bool match = false; 347 348 rcu_lockdep_assert(rcu_read_lock_held() || 349 lockdep_is_held(&devcgroup_mutex), 350 "device_cgroup::may_access() called without proper synchronization"); 351 352 list_for_each_entry_rcu(ex, &dev_cgroup->exceptions, list) { 353 if ((refex->type & DEV_BLOCK) && !(ex->type & DEV_BLOCK)) 354 continue; 355 if ((refex->type & DEV_CHAR) && !(ex->type & DEV_CHAR)) 356 continue; 357 if (ex->major != ~0 && ex->major != refex->major) 358 continue; 359 if (ex->minor != ~0 && ex->minor != refex->minor) 360 continue; 361 if (refex->access & (~ex->access)) 362 continue; 363 match = true; 364 break; 365 } 366 367 if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) { 368 if (behavior == DEVCG_DEFAULT_ALLOW) { 369 /* the exception will deny access to certain devices */ 370 return true; 371 } else { 372 /* the exception will allow access to certain devices */ 373 if (match) 374 /* 375 * a new exception allowing access shouldn't 376 * match an parent's exception 377 */ 378 return false; 379 return true; 380 } 381 } else { 382 /* only behavior == DEVCG_DEFAULT_DENY allowed here */ 383 if (match) 384 /* parent has an exception that matches the proposed */ 385 return true; 386 else 387 return false; 388 } 389 return false; 390 } 391 392 /* 393 * parent_has_perm: 394 * when adding a new allow rule to a device exception list, the rule 395 * must be allowed in the parent device 396 */ 397 static int parent_has_perm(struct dev_cgroup *childcg, 398 struct dev_exception_item *ex) 399 { 400 struct cgroup *pcg = childcg->css.cgroup->parent; 401 struct dev_cgroup *parent; 402 403 if (!pcg) 404 return 1; 405 parent = cgroup_to_devcgroup(pcg); 406 return may_access(parent, ex, childcg->behavior); 407 } 408 409 /** 410 * may_allow_all - checks if it's possible to change the behavior to 411 * allow based on parent's rules. 412 * @parent: device cgroup's parent 413 * returns: != 0 in case it's allowed, 0 otherwise 414 */ 415 static inline int may_allow_all(struct dev_cgroup *parent) 416 { 417 if (!parent) 418 return 1; 419 return parent->behavior == DEVCG_DEFAULT_ALLOW; 420 } 421 422 /** 423 * revalidate_active_exceptions - walks through the active exception list and 424 * revalidates the exceptions based on parent's 425 * behavior and exceptions. The exceptions that 426 * are no longer valid will be removed. 427 * Called with devcgroup_mutex held. 428 * @devcg: cgroup which exceptions will be checked 429 * 430 * This is one of the three key functions for hierarchy implementation. 431 * This function is responsible for re-evaluating all the cgroup's active 432 * exceptions due to a parent's exception change. 433 * Refer to Documentation/cgroups/devices.txt for more details. 434 */ 435 static void revalidate_active_exceptions(struct dev_cgroup *devcg) 436 { 437 struct dev_exception_item *ex; 438 struct list_head *this, *tmp; 439 440 list_for_each_safe(this, tmp, &devcg->exceptions) { 441 ex = container_of(this, struct dev_exception_item, list); 442 if (!parent_has_perm(devcg, ex)) 443 dev_exception_rm(devcg, ex); 444 } 445 } 446 447 /** 448 * get_online_devcg - walks the cgroup tree and fills a list with the online 449 * groups 450 * @root: cgroup used as starting point 451 * @online: list that will be filled with online groups 452 * 453 * Must be called with devcgroup_mutex held. Grabs RCU lock. 454 * Because devcgroup_mutex is held, no devcg will become online or offline 455 * during the tree walk (see devcgroup_online, devcgroup_offline) 456 * A separated list is needed because propagate_behavior() and 457 * propagate_exception() need to allocate memory and can block. 458 */ 459 static void get_online_devcg(struct cgroup *root, struct list_head *online) 460 { 461 struct cgroup *pos; 462 struct dev_cgroup *devcg; 463 464 lockdep_assert_held(&devcgroup_mutex); 465 466 rcu_read_lock(); 467 cgroup_for_each_descendant_pre(pos, root) { 468 devcg = cgroup_to_devcgroup(pos); 469 if (is_devcg_online(devcg)) 470 list_add_tail(&devcg->propagate_pending, online); 471 } 472 rcu_read_unlock(); 473 } 474 475 /** 476 * propagate_exception - propagates a new exception to the children 477 * @devcg_root: device cgroup that added a new exception 478 * @ex: new exception to be propagated 479 * 480 * returns: 0 in case of success, != 0 in case of error 481 */ 482 static int propagate_exception(struct dev_cgroup *devcg_root, 483 struct dev_exception_item *ex) 484 { 485 struct cgroup *root = devcg_root->css.cgroup; 486 struct dev_cgroup *devcg, *parent, *tmp; 487 int rc = 0; 488 LIST_HEAD(pending); 489 490 get_online_devcg(root, &pending); 491 492 list_for_each_entry_safe(devcg, tmp, &pending, propagate_pending) { 493 parent = cgroup_to_devcgroup(devcg->css.cgroup->parent); 494 495 /* 496 * in case both root's behavior and devcg is allow, a new 497 * restriction means adding to the exception list 498 */ 499 if (devcg_root->behavior == DEVCG_DEFAULT_ALLOW && 500 devcg->behavior == DEVCG_DEFAULT_ALLOW) { 501 rc = dev_exception_add(devcg, ex); 502 if (rc) 503 break; 504 } else { 505 /* 506 * in the other possible cases: 507 * root's behavior: allow, devcg's: deny 508 * root's behavior: deny, devcg's: deny 509 * the exception will be removed 510 */ 511 dev_exception_rm(devcg, ex); 512 } 513 revalidate_active_exceptions(devcg); 514 515 list_del_init(&devcg->propagate_pending); 516 } 517 return rc; 518 } 519 520 static inline bool has_children(struct dev_cgroup *devcgroup) 521 { 522 struct cgroup *cgrp = devcgroup->css.cgroup; 523 524 return !list_empty(&cgrp->children); 525 } 526 527 /* 528 * Modify the exception list using allow/deny rules. 529 * CAP_SYS_ADMIN is needed for this. It's at least separate from CAP_MKNOD 530 * so we can give a container CAP_MKNOD to let it create devices but not 531 * modify the exception list. 532 * It seems likely we'll want to add a CAP_CONTAINER capability to allow 533 * us to also grant CAP_SYS_ADMIN to containers without giving away the 534 * device exception list controls, but for now we'll stick with CAP_SYS_ADMIN 535 * 536 * Taking rules away is always allowed (given CAP_SYS_ADMIN). Granting 537 * new access is only allowed if you're in the top-level cgroup, or your 538 * parent cgroup has the access you're asking for. 539 */ 540 static int devcgroup_update_access(struct dev_cgroup *devcgroup, 541 int filetype, const char *buffer) 542 { 543 const char *b; 544 char temp[12]; /* 11 + 1 characters needed for a u32 */ 545 int count, rc = 0; 546 struct dev_exception_item ex; 547 struct cgroup *p = devcgroup->css.cgroup; 548 struct dev_cgroup *parent = NULL; 549 550 if (!capable(CAP_SYS_ADMIN)) 551 return -EPERM; 552 553 if (p->parent) 554 parent = cgroup_to_devcgroup(p->parent); 555 556 memset(&ex, 0, sizeof(ex)); 557 b = buffer; 558 559 switch (*b) { 560 case 'a': 561 switch (filetype) { 562 case DEVCG_ALLOW: 563 if (has_children(devcgroup)) 564 return -EINVAL; 565 566 if (!may_allow_all(parent)) 567 return -EPERM; 568 dev_exception_clean(devcgroup); 569 devcgroup->behavior = DEVCG_DEFAULT_ALLOW; 570 if (!parent) 571 break; 572 573 rc = dev_exceptions_copy(&devcgroup->exceptions, 574 &parent->exceptions); 575 if (rc) 576 return rc; 577 break; 578 case DEVCG_DENY: 579 if (has_children(devcgroup)) 580 return -EINVAL; 581 582 dev_exception_clean(devcgroup); 583 devcgroup->behavior = DEVCG_DEFAULT_DENY; 584 break; 585 default: 586 return -EINVAL; 587 } 588 return 0; 589 case 'b': 590 ex.type = DEV_BLOCK; 591 break; 592 case 'c': 593 ex.type = DEV_CHAR; 594 break; 595 default: 596 return -EINVAL; 597 } 598 b++; 599 if (!isspace(*b)) 600 return -EINVAL; 601 b++; 602 if (*b == '*') { 603 ex.major = ~0; 604 b++; 605 } else if (isdigit(*b)) { 606 memset(temp, 0, sizeof(temp)); 607 for (count = 0; count < sizeof(temp) - 1; count++) { 608 temp[count] = *b; 609 b++; 610 if (!isdigit(*b)) 611 break; 612 } 613 rc = kstrtou32(temp, 10, &ex.major); 614 if (rc) 615 return -EINVAL; 616 } else { 617 return -EINVAL; 618 } 619 if (*b != ':') 620 return -EINVAL; 621 b++; 622 623 /* read minor */ 624 if (*b == '*') { 625 ex.minor = ~0; 626 b++; 627 } else if (isdigit(*b)) { 628 memset(temp, 0, sizeof(temp)); 629 for (count = 0; count < sizeof(temp) - 1; count++) { 630 temp[count] = *b; 631 b++; 632 if (!isdigit(*b)) 633 break; 634 } 635 rc = kstrtou32(temp, 10, &ex.minor); 636 if (rc) 637 return -EINVAL; 638 } else { 639 return -EINVAL; 640 } 641 if (!isspace(*b)) 642 return -EINVAL; 643 for (b++, count = 0; count < 3; count++, b++) { 644 switch (*b) { 645 case 'r': 646 ex.access |= ACC_READ; 647 break; 648 case 'w': 649 ex.access |= ACC_WRITE; 650 break; 651 case 'm': 652 ex.access |= ACC_MKNOD; 653 break; 654 case '\n': 655 case '\0': 656 count = 3; 657 break; 658 default: 659 return -EINVAL; 660 } 661 } 662 663 switch (filetype) { 664 case DEVCG_ALLOW: 665 if (!parent_has_perm(devcgroup, &ex)) 666 return -EPERM; 667 /* 668 * If the default policy is to allow by default, try to remove 669 * an matching exception instead. And be silent about it: we 670 * don't want to break compatibility 671 */ 672 if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) { 673 dev_exception_rm(devcgroup, &ex); 674 return 0; 675 } 676 rc = dev_exception_add(devcgroup, &ex); 677 break; 678 case DEVCG_DENY: 679 /* 680 * If the default policy is to deny by default, try to remove 681 * an matching exception instead. And be silent about it: we 682 * don't want to break compatibility 683 */ 684 if (devcgroup->behavior == DEVCG_DEFAULT_DENY) 685 dev_exception_rm(devcgroup, &ex); 686 else 687 rc = dev_exception_add(devcgroup, &ex); 688 689 if (rc) 690 break; 691 /* we only propagate new restrictions */ 692 rc = propagate_exception(devcgroup, &ex); 693 break; 694 default: 695 rc = -EINVAL; 696 } 697 return rc; 698 } 699 700 static int devcgroup_access_write(struct cgroup *cgrp, struct cftype *cft, 701 const char *buffer) 702 { 703 int retval; 704 705 mutex_lock(&devcgroup_mutex); 706 retval = devcgroup_update_access(cgroup_to_devcgroup(cgrp), 707 cft->private, buffer); 708 mutex_unlock(&devcgroup_mutex); 709 return retval; 710 } 711 712 static struct cftype dev_cgroup_files[] = { 713 { 714 .name = "allow", 715 .write_string = devcgroup_access_write, 716 .private = DEVCG_ALLOW, 717 }, 718 { 719 .name = "deny", 720 .write_string = devcgroup_access_write, 721 .private = DEVCG_DENY, 722 }, 723 { 724 .name = "list", 725 .read_seq_string = devcgroup_seq_read, 726 .private = DEVCG_LIST, 727 }, 728 { } /* terminate */ 729 }; 730 731 struct cgroup_subsys devices_subsys = { 732 .name = "devices", 733 .can_attach = devcgroup_can_attach, 734 .css_alloc = devcgroup_css_alloc, 735 .css_free = devcgroup_css_free, 736 .css_online = devcgroup_online, 737 .css_offline = devcgroup_offline, 738 .subsys_id = devices_subsys_id, 739 .base_cftypes = dev_cgroup_files, 740 }; 741 742 /** 743 * __devcgroup_check_permission - checks if an inode operation is permitted 744 * @dev_cgroup: the dev cgroup to be tested against 745 * @type: device type 746 * @major: device major number 747 * @minor: device minor number 748 * @access: combination of ACC_WRITE, ACC_READ and ACC_MKNOD 749 * 750 * returns 0 on success, -EPERM case the operation is not permitted 751 */ 752 static int __devcgroup_check_permission(short type, u32 major, u32 minor, 753 short access) 754 { 755 struct dev_cgroup *dev_cgroup; 756 struct dev_exception_item ex; 757 int rc; 758 759 memset(&ex, 0, sizeof(ex)); 760 ex.type = type; 761 ex.major = major; 762 ex.minor = minor; 763 ex.access = access; 764 765 rcu_read_lock(); 766 dev_cgroup = task_devcgroup(current); 767 rc = may_access(dev_cgroup, &ex, dev_cgroup->behavior); 768 rcu_read_unlock(); 769 770 if (!rc) 771 return -EPERM; 772 773 return 0; 774 } 775 776 int __devcgroup_inode_permission(struct inode *inode, int mask) 777 { 778 short type, access = 0; 779 780 if (S_ISBLK(inode->i_mode)) 781 type = DEV_BLOCK; 782 if (S_ISCHR(inode->i_mode)) 783 type = DEV_CHAR; 784 if (mask & MAY_WRITE) 785 access |= ACC_WRITE; 786 if (mask & MAY_READ) 787 access |= ACC_READ; 788 789 return __devcgroup_check_permission(type, imajor(inode), iminor(inode), 790 access); 791 } 792 793 int devcgroup_inode_mknod(int mode, dev_t dev) 794 { 795 short type; 796 797 if (!S_ISBLK(mode) && !S_ISCHR(mode)) 798 return 0; 799 800 if (S_ISBLK(mode)) 801 type = DEV_BLOCK; 802 else 803 type = DEV_CHAR; 804 805 return __devcgroup_check_permission(type, MAJOR(dev), MINOR(dev), 806 ACC_MKNOD); 807 808 } 809