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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 | }; |
53 | |
54 | static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s) |
55 | { |
56 | return s ? container_of(s, struct dev_cgroup, css) : NULL; |
57 | } |
58 | |
59 | static inline struct dev_cgroup *task_devcgroup(struct task_struct *task) |
60 | { |
61 | return css_to_devcgroup(task_css(task, devices_cgrp_id)); |
62 | } |
63 | |
64 | /* |
65 | * called under devcgroup_mutex |
66 | */ |
67 | static int dev_exceptions_copy(struct list_head *dest, struct list_head *orig) |
68 | { |
69 | struct dev_exception_item *ex, *tmp, *new; |
70 | |
71 | lockdep_assert_held(&devcgroup_mutex); |
72 | |
73 | list_for_each_entry(ex, orig, list) { |
74 | new = kmemdup(ex, sizeof(*ex), GFP_KERNEL); |
75 | if (!new) |
76 | goto free_and_exit; |
77 | list_add_tail(&new->list, dest); |
78 | } |
79 | |
80 | return 0; |
81 | |
82 | free_and_exit: |
83 | list_for_each_entry_safe(ex, tmp, dest, list) { |
84 | list_del(&ex->list); |
85 | kfree(ex); |
86 | } |
87 | return -ENOMEM; |
88 | } |
89 | |
90 | /* |
91 | * called under devcgroup_mutex |
92 | */ |
93 | static int dev_exception_add(struct dev_cgroup *dev_cgroup, |
94 | struct dev_exception_item *ex) |
95 | { |
96 | struct dev_exception_item *excopy, *walk; |
97 | |
98 | lockdep_assert_held(&devcgroup_mutex); |
99 | |
100 | excopy = kmemdup(ex, sizeof(*ex), GFP_KERNEL); |
101 | if (!excopy) |
102 | return -ENOMEM; |
103 | |
104 | list_for_each_entry(walk, &dev_cgroup->exceptions, list) { |
105 | if (walk->type != ex->type) |
106 | continue; |
107 | if (walk->major != ex->major) |
108 | continue; |
109 | if (walk->minor != ex->minor) |
110 | continue; |
111 | |
112 | walk->access |= ex->access; |
113 | kfree(excopy); |
114 | excopy = NULL; |
115 | } |
116 | |
117 | if (excopy != NULL) |
118 | list_add_tail_rcu(&excopy->list, &dev_cgroup->exceptions); |
119 | return 0; |
120 | } |
121 | |
122 | /* |
123 | * called under devcgroup_mutex |
124 | */ |
125 | static void dev_exception_rm(struct dev_cgroup *dev_cgroup, |
126 | struct dev_exception_item *ex) |
127 | { |
128 | struct dev_exception_item *walk, *tmp; |
129 | |
130 | lockdep_assert_held(&devcgroup_mutex); |
131 | |
132 | list_for_each_entry_safe(walk, tmp, &dev_cgroup->exceptions, list) { |
133 | if (walk->type != ex->type) |
134 | continue; |
135 | if (walk->major != ex->major) |
136 | continue; |
137 | if (walk->minor != ex->minor) |
138 | continue; |
139 | |
140 | walk->access &= ~ex->access; |
141 | if (!walk->access) { |
142 | list_del_rcu(&walk->list); |
143 | kfree_rcu(walk, rcu); |
144 | } |
145 | } |
146 | } |
147 | |
148 | static void __dev_exception_clean(struct dev_cgroup *dev_cgroup) |
149 | { |
150 | struct dev_exception_item *ex, *tmp; |
151 | |
152 | list_for_each_entry_safe(ex, tmp, &dev_cgroup->exceptions, list) { |
153 | list_del_rcu(&ex->list); |
154 | kfree_rcu(ex, rcu); |
155 | } |
156 | } |
157 | |
158 | /** |
159 | * dev_exception_clean - frees all entries of the exception list |
160 | * @dev_cgroup: dev_cgroup with the exception list to be cleaned |
161 | * |
162 | * called under devcgroup_mutex |
163 | */ |
164 | static void dev_exception_clean(struct dev_cgroup *dev_cgroup) |
165 | { |
166 | lockdep_assert_held(&devcgroup_mutex); |
167 | |
168 | __dev_exception_clean(dev_cgroup); |
169 | } |
170 | |
171 | static inline bool is_devcg_online(const struct dev_cgroup *devcg) |
172 | { |
173 | return (devcg->behavior != DEVCG_DEFAULT_NONE); |
174 | } |
175 | |
176 | /** |
177 | * devcgroup_online - initializes devcgroup's behavior and exceptions based on |
178 | * parent's |
179 | * @css: css getting online |
180 | * returns 0 in case of success, error code otherwise |
181 | */ |
182 | static int devcgroup_online(struct cgroup_subsys_state *css) |
183 | { |
184 | struct dev_cgroup *dev_cgroup = css_to_devcgroup(css); |
185 | struct dev_cgroup *parent_dev_cgroup = css_to_devcgroup(css->parent); |
186 | int ret = 0; |
187 | |
188 | mutex_lock(&devcgroup_mutex); |
189 | |
190 | if (parent_dev_cgroup == NULL) |
191 | dev_cgroup->behavior = DEVCG_DEFAULT_ALLOW; |
192 | else { |
193 | ret = dev_exceptions_copy(&dev_cgroup->exceptions, |
194 | &parent_dev_cgroup->exceptions); |
195 | if (!ret) |
196 | dev_cgroup->behavior = parent_dev_cgroup->behavior; |
197 | } |
198 | mutex_unlock(&devcgroup_mutex); |
199 | |
200 | return ret; |
201 | } |
202 | |
203 | static void devcgroup_offline(struct cgroup_subsys_state *css) |
204 | { |
205 | struct dev_cgroup *dev_cgroup = css_to_devcgroup(css); |
206 | |
207 | mutex_lock(&devcgroup_mutex); |
208 | dev_cgroup->behavior = DEVCG_DEFAULT_NONE; |
209 | mutex_unlock(&devcgroup_mutex); |
210 | } |
211 | |
212 | /* |
213 | * called from kernel/cgroup.c with cgroup_lock() held. |
214 | */ |
215 | static struct cgroup_subsys_state * |
216 | devcgroup_css_alloc(struct cgroup_subsys_state *parent_css) |
217 | { |
218 | struct dev_cgroup *dev_cgroup; |
219 | |
220 | dev_cgroup = kzalloc(sizeof(*dev_cgroup), GFP_KERNEL); |
221 | if (!dev_cgroup) |
222 | return ERR_PTR(-ENOMEM); |
223 | INIT_LIST_HEAD(&dev_cgroup->exceptions); |
224 | dev_cgroup->behavior = DEVCG_DEFAULT_NONE; |
225 | |
226 | return &dev_cgroup->css; |
227 | } |
228 | |
229 | static void devcgroup_css_free(struct cgroup_subsys_state *css) |
230 | { |
231 | struct dev_cgroup *dev_cgroup = css_to_devcgroup(css); |
232 | |
233 | __dev_exception_clean(dev_cgroup); |
234 | kfree(dev_cgroup); |
235 | } |
236 | |
237 | #define DEVCG_ALLOW 1 |
238 | #define DEVCG_DENY 2 |
239 | #define DEVCG_LIST 3 |
240 | |
241 | #define MAJMINLEN 13 |
242 | #define ACCLEN 4 |
243 | |
244 | static void set_access(char *acc, short access) |
245 | { |
246 | int idx = 0; |
247 | memset(acc, 0, ACCLEN); |
248 | if (access & ACC_READ) |
249 | acc[idx++] = 'r'; |
250 | if (access & ACC_WRITE) |
251 | acc[idx++] = 'w'; |
252 | if (access & ACC_MKNOD) |
253 | acc[idx++] = 'm'; |
254 | } |
255 | |
256 | static char type_to_char(short type) |
257 | { |
258 | if (type == DEV_ALL) |
259 | return 'a'; |
260 | if (type == DEV_CHAR) |
261 | return 'c'; |
262 | if (type == DEV_BLOCK) |
263 | return 'b'; |
264 | return 'X'; |
265 | } |
266 | |
267 | static void set_majmin(char *str, unsigned m) |
268 | { |
269 | if (m == ~0) |
270 | strcpy(str, "*"); |
271 | else |
272 | sprintf(str, "%u", m); |
273 | } |
274 | |
275 | static int devcgroup_seq_show(struct seq_file *m, void *v) |
276 | { |
277 | struct dev_cgroup *devcgroup = css_to_devcgroup(seq_css(m)); |
278 | struct dev_exception_item *ex; |
279 | char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN]; |
280 | |
281 | rcu_read_lock(); |
282 | /* |
283 | * To preserve the compatibility: |
284 | * - Only show the "all devices" when the default policy is to allow |
285 | * - List the exceptions in case the default policy is to deny |
286 | * This way, the file remains as a "whitelist of devices" |
287 | */ |
288 | if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) { |
289 | set_access(acc, ACC_MASK); |
290 | set_majmin(maj, ~0); |
291 | set_majmin(min, ~0); |
292 | seq_printf(m, "%c %s:%s %s\n", type_to_char(DEV_ALL), |
293 | maj, min, acc); |
294 | } else { |
295 | list_for_each_entry_rcu(ex, &devcgroup->exceptions, list) { |
296 | set_access(acc, ex->access); |
297 | set_majmin(maj, ex->major); |
298 | set_majmin(min, ex->minor); |
299 | seq_printf(m, "%c %s:%s %s\n", type_to_char(ex->type), |
300 | maj, min, acc); |
301 | } |
302 | } |
303 | rcu_read_unlock(); |
304 | |
305 | return 0; |
306 | } |
307 | |
308 | /** |
309 | * match_exception - iterates the exception list trying to find a complete match |
310 | * @exceptions: list of exceptions |
311 | * @type: device type (DEV_BLOCK or DEV_CHAR) |
312 | * @major: device file major number, ~0 to match all |
313 | * @minor: device file minor number, ~0 to match all |
314 | * @access: permission mask (ACC_READ, ACC_WRITE, ACC_MKNOD) |
315 | * |
316 | * It is considered a complete match if an exception is found that will |
317 | * contain the entire range of provided parameters. |
318 | * |
319 | * Return: true in case it matches an exception completely |
320 | */ |
321 | static bool match_exception(struct list_head *exceptions, short type, |
322 | u32 major, u32 minor, short access) |
323 | { |
324 | struct dev_exception_item *ex; |
325 | |
326 | list_for_each_entry_rcu(ex, exceptions, list) { |
327 | if ((type & DEV_BLOCK) && !(ex->type & DEV_BLOCK)) |
328 | continue; |
329 | if ((type & DEV_CHAR) && !(ex->type & DEV_CHAR)) |
330 | continue; |
331 | if (ex->major != ~0 && ex->major != major) |
332 | continue; |
333 | if (ex->minor != ~0 && ex->minor != minor) |
334 | continue; |
335 | /* provided access cannot have more than the exception rule */ |
336 | if (access & (~ex->access)) |
337 | continue; |
338 | return true; |
339 | } |
340 | return false; |
341 | } |
342 | |
343 | /** |
344 | * match_exception_partial - iterates the exception list trying to find a partial match |
345 | * @exceptions: list of exceptions |
346 | * @type: device type (DEV_BLOCK or DEV_CHAR) |
347 | * @major: device file major number, ~0 to match all |
348 | * @minor: device file minor number, ~0 to match all |
349 | * @access: permission mask (ACC_READ, ACC_WRITE, ACC_MKNOD) |
350 | * |
351 | * It is considered a partial match if an exception's range is found to |
352 | * contain *any* of the devices specified by provided parameters. This is |
353 | * used to make sure no extra access is being granted that is forbidden by |
354 | * any of the exception list. |
355 | * |
356 | * Return: true in case the provided range mat matches an exception completely |
357 | */ |
358 | static bool match_exception_partial(struct list_head *exceptions, short type, |
359 | u32 major, u32 minor, short access) |
360 | { |
361 | struct dev_exception_item *ex; |
362 | |
363 | list_for_each_entry_rcu(ex, exceptions, list) { |
364 | if ((type & DEV_BLOCK) && !(ex->type & DEV_BLOCK)) |
365 | continue; |
366 | if ((type & DEV_CHAR) && !(ex->type & DEV_CHAR)) |
367 | continue; |
368 | /* |
369 | * We must be sure that both the exception and the provided |
370 | * range aren't masking all devices |
371 | */ |
372 | if (ex->major != ~0 && major != ~0 && ex->major != major) |
373 | continue; |
374 | if (ex->minor != ~0 && minor != ~0 && ex->minor != minor) |
375 | continue; |
376 | /* |
377 | * In order to make sure the provided range isn't matching |
378 | * an exception, all its access bits shouldn't match the |
379 | * exception's access bits |
380 | */ |
381 | if (!(access & ex->access)) |
382 | continue; |
383 | return true; |
384 | } |
385 | return false; |
386 | } |
387 | |
388 | /** |
389 | * verify_new_ex - verifies if a new exception is allowed by parent cgroup's permissions |
390 | * @dev_cgroup: dev cgroup to be tested against |
391 | * @refex: new exception |
392 | * @behavior: behavior of the exception's dev_cgroup |
393 | * |
394 | * This is used to make sure a child cgroup won't have more privileges |
395 | * than its parent |
396 | */ |
397 | static bool verify_new_ex(struct dev_cgroup *dev_cgroup, |
398 | struct dev_exception_item *refex, |
399 | enum devcg_behavior behavior) |
400 | { |
401 | bool match = false; |
402 | |
403 | rcu_lockdep_assert(rcu_read_lock_held() || |
404 | lockdep_is_held(&devcgroup_mutex), |
405 | "device_cgroup:verify_new_ex called without proper synchronization"); |
406 | |
407 | if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) { |
408 | if (behavior == DEVCG_DEFAULT_ALLOW) { |
409 | /* |
410 | * new exception in the child doesn't matter, only |
411 | * adding extra restrictions |
412 | */ |
413 | return true; |
414 | } else { |
415 | /* |
416 | * new exception in the child will add more devices |
417 | * that can be acessed, so it can't match any of |
418 | * parent's exceptions, even slightly |
419 | */ |
420 | match = match_exception_partial(&dev_cgroup->exceptions, |
421 | refex->type, |
422 | refex->major, |
423 | refex->minor, |
424 | refex->access); |
425 | |
426 | if (match) |
427 | return false; |
428 | return true; |
429 | } |
430 | } else { |
431 | /* |
432 | * Only behavior == DEVCG_DEFAULT_DENY allowed here, therefore |
433 | * the new exception will add access to more devices and must |
434 | * be contained completely in an parent's exception to be |
435 | * allowed |
436 | */ |
437 | match = match_exception(&dev_cgroup->exceptions, refex->type, |
438 | refex->major, refex->minor, |
439 | refex->access); |
440 | |
441 | if (match) |
442 | /* parent has an exception that matches the proposed */ |
443 | return true; |
444 | else |
445 | return false; |
446 | } |
447 | return false; |
448 | } |
449 | |
450 | /* |
451 | * parent_has_perm: |
452 | * when adding a new allow rule to a device exception list, the rule |
453 | * must be allowed in the parent device |
454 | */ |
455 | static int parent_has_perm(struct dev_cgroup *childcg, |
456 | struct dev_exception_item *ex) |
457 | { |
458 | struct dev_cgroup *parent = css_to_devcgroup(childcg->css.parent); |
459 | |
460 | if (!parent) |
461 | return 1; |
462 | return verify_new_ex(parent, ex, childcg->behavior); |
463 | } |
464 | |
465 | /** |
466 | * parent_allows_removal - verify if it's ok to remove an exception |
467 | * @childcg: child cgroup from where the exception will be removed |
468 | * @ex: exception being removed |
469 | * |
470 | * When removing an exception in cgroups with default ALLOW policy, it must |
471 | * be checked if removing it will give the child cgroup more access than the |
472 | * parent. |
473 | * |
474 | * Return: true if it's ok to remove exception, false otherwise |
475 | */ |
476 | static bool parent_allows_removal(struct dev_cgroup *childcg, |
477 | struct dev_exception_item *ex) |
478 | { |
479 | struct dev_cgroup *parent = css_to_devcgroup(childcg->css.parent); |
480 | |
481 | if (!parent) |
482 | return true; |
483 | |
484 | /* It's always allowed to remove access to devices */ |
485 | if (childcg->behavior == DEVCG_DEFAULT_DENY) |
486 | return true; |
487 | |
488 | /* |
489 | * Make sure you're not removing part or a whole exception existing in |
490 | * the parent cgroup |
491 | */ |
492 | return !match_exception_partial(&parent->exceptions, ex->type, |
493 | ex->major, ex->minor, ex->access); |
494 | } |
495 | |
496 | /** |
497 | * may_allow_all - checks if it's possible to change the behavior to |
498 | * allow based on parent's rules. |
499 | * @parent: device cgroup's parent |
500 | * returns: != 0 in case it's allowed, 0 otherwise |
501 | */ |
502 | static inline int may_allow_all(struct dev_cgroup *parent) |
503 | { |
504 | if (!parent) |
505 | return 1; |
506 | return parent->behavior == DEVCG_DEFAULT_ALLOW; |
507 | } |
508 | |
509 | /** |
510 | * revalidate_active_exceptions - walks through the active exception list and |
511 | * revalidates the exceptions based on parent's |
512 | * behavior and exceptions. The exceptions that |
513 | * are no longer valid will be removed. |
514 | * Called with devcgroup_mutex held. |
515 | * @devcg: cgroup which exceptions will be checked |
516 | * |
517 | * This is one of the three key functions for hierarchy implementation. |
518 | * This function is responsible for re-evaluating all the cgroup's active |
519 | * exceptions due to a parent's exception change. |
520 | * Refer to Documentation/cgroups/devices.txt for more details. |
521 | */ |
522 | static void revalidate_active_exceptions(struct dev_cgroup *devcg) |
523 | { |
524 | struct dev_exception_item *ex; |
525 | struct list_head *this, *tmp; |
526 | |
527 | list_for_each_safe(this, tmp, &devcg->exceptions) { |
528 | ex = container_of(this, struct dev_exception_item, list); |
529 | if (!parent_has_perm(devcg, ex)) |
530 | dev_exception_rm(devcg, ex); |
531 | } |
532 | } |
533 | |
534 | /** |
535 | * propagate_exception - propagates a new exception to the children |
536 | * @devcg_root: device cgroup that added a new exception |
537 | * @ex: new exception to be propagated |
538 | * |
539 | * returns: 0 in case of success, != 0 in case of error |
540 | */ |
541 | static int propagate_exception(struct dev_cgroup *devcg_root, |
542 | struct dev_exception_item *ex) |
543 | { |
544 | struct cgroup_subsys_state *pos; |
545 | int rc = 0; |
546 | |
547 | rcu_read_lock(); |
548 | |
549 | css_for_each_descendant_pre(pos, &devcg_root->css) { |
550 | struct dev_cgroup *devcg = css_to_devcgroup(pos); |
551 | |
552 | /* |
553 | * Because devcgroup_mutex is held, no devcg will become |
554 | * online or offline during the tree walk (see on/offline |
555 | * methods), and online ones are safe to access outside RCU |
556 | * read lock without bumping refcnt. |
557 | */ |
558 | if (pos == &devcg_root->css || !is_devcg_online(devcg)) |
559 | continue; |
560 | |
561 | rcu_read_unlock(); |
562 | |
563 | /* |
564 | * in case both root's behavior and devcg is allow, a new |
565 | * restriction means adding to the exception list |
566 | */ |
567 | if (devcg_root->behavior == DEVCG_DEFAULT_ALLOW && |
568 | devcg->behavior == DEVCG_DEFAULT_ALLOW) { |
569 | rc = dev_exception_add(devcg, ex); |
570 | if (rc) |
571 | break; |
572 | } else { |
573 | /* |
574 | * in the other possible cases: |
575 | * root's behavior: allow, devcg's: deny |
576 | * root's behavior: deny, devcg's: deny |
577 | * the exception will be removed |
578 | */ |
579 | dev_exception_rm(devcg, ex); |
580 | } |
581 | revalidate_active_exceptions(devcg); |
582 | |
583 | rcu_read_lock(); |
584 | } |
585 | |
586 | rcu_read_unlock(); |
587 | return rc; |
588 | } |
589 | |
590 | /* |
591 | * Modify the exception list using allow/deny rules. |
592 | * CAP_SYS_ADMIN is needed for this. It's at least separate from CAP_MKNOD |
593 | * so we can give a container CAP_MKNOD to let it create devices but not |
594 | * modify the exception list. |
595 | * It seems likely we'll want to add a CAP_CONTAINER capability to allow |
596 | * us to also grant CAP_SYS_ADMIN to containers without giving away the |
597 | * device exception list controls, but for now we'll stick with CAP_SYS_ADMIN |
598 | * |
599 | * Taking rules away is always allowed (given CAP_SYS_ADMIN). Granting |
600 | * new access is only allowed if you're in the top-level cgroup, or your |
601 | * parent cgroup has the access you're asking for. |
602 | */ |
603 | static int devcgroup_update_access(struct dev_cgroup *devcgroup, |
604 | int filetype, char *buffer) |
605 | { |
606 | const char *b; |
607 | char temp[12]; /* 11 + 1 characters needed for a u32 */ |
608 | int count, rc = 0; |
609 | struct dev_exception_item ex; |
610 | struct dev_cgroup *parent = css_to_devcgroup(devcgroup->css.parent); |
611 | |
612 | if (!capable(CAP_SYS_ADMIN)) |
613 | return -EPERM; |
614 | |
615 | memset(&ex, 0, sizeof(ex)); |
616 | b = buffer; |
617 | |
618 | switch (*b) { |
619 | case 'a': |
620 | switch (filetype) { |
621 | case DEVCG_ALLOW: |
622 | if (css_has_online_children(&devcgroup->css)) |
623 | return -EINVAL; |
624 | |
625 | if (!may_allow_all(parent)) |
626 | return -EPERM; |
627 | dev_exception_clean(devcgroup); |
628 | devcgroup->behavior = DEVCG_DEFAULT_ALLOW; |
629 | if (!parent) |
630 | break; |
631 | |
632 | rc = dev_exceptions_copy(&devcgroup->exceptions, |
633 | &parent->exceptions); |
634 | if (rc) |
635 | return rc; |
636 | break; |
637 | case DEVCG_DENY: |
638 | if (css_has_online_children(&devcgroup->css)) |
639 | return -EINVAL; |
640 | |
641 | dev_exception_clean(devcgroup); |
642 | devcgroup->behavior = DEVCG_DEFAULT_DENY; |
643 | break; |
644 | default: |
645 | return -EINVAL; |
646 | } |
647 | return 0; |
648 | case 'b': |
649 | ex.type = DEV_BLOCK; |
650 | break; |
651 | case 'c': |
652 | ex.type = DEV_CHAR; |
653 | break; |
654 | default: |
655 | return -EINVAL; |
656 | } |
657 | b++; |
658 | if (!isspace(*b)) |
659 | return -EINVAL; |
660 | b++; |
661 | if (*b == '*') { |
662 | ex.major = ~0; |
663 | b++; |
664 | } else if (isdigit(*b)) { |
665 | memset(temp, 0, sizeof(temp)); |
666 | for (count = 0; count < sizeof(temp) - 1; count++) { |
667 | temp[count] = *b; |
668 | b++; |
669 | if (!isdigit(*b)) |
670 | break; |
671 | } |
672 | rc = kstrtou32(temp, 10, &ex.major); |
673 | if (rc) |
674 | return -EINVAL; |
675 | } else { |
676 | return -EINVAL; |
677 | } |
678 | if (*b != ':') |
679 | return -EINVAL; |
680 | b++; |
681 | |
682 | /* read minor */ |
683 | if (*b == '*') { |
684 | ex.minor = ~0; |
685 | b++; |
686 | } else if (isdigit(*b)) { |
687 | memset(temp, 0, sizeof(temp)); |
688 | for (count = 0; count < sizeof(temp) - 1; count++) { |
689 | temp[count] = *b; |
690 | b++; |
691 | if (!isdigit(*b)) |
692 | break; |
693 | } |
694 | rc = kstrtou32(temp, 10, &ex.minor); |
695 | if (rc) |
696 | return -EINVAL; |
697 | } else { |
698 | return -EINVAL; |
699 | } |
700 | if (!isspace(*b)) |
701 | return -EINVAL; |
702 | for (b++, count = 0; count < 3; count++, b++) { |
703 | switch (*b) { |
704 | case 'r': |
705 | ex.access |= ACC_READ; |
706 | break; |
707 | case 'w': |
708 | ex.access |= ACC_WRITE; |
709 | break; |
710 | case 'm': |
711 | ex.access |= ACC_MKNOD; |
712 | break; |
713 | case '\n': |
714 | case '\0': |
715 | count = 3; |
716 | break; |
717 | default: |
718 | return -EINVAL; |
719 | } |
720 | } |
721 | |
722 | switch (filetype) { |
723 | case DEVCG_ALLOW: |
724 | /* |
725 | * If the default policy is to allow by default, try to remove |
726 | * an matching exception instead. And be silent about it: we |
727 | * don't want to break compatibility |
728 | */ |
729 | if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) { |
730 | /* Check if the parent allows removing it first */ |
731 | if (!parent_allows_removal(devcgroup, &ex)) |
732 | return -EPERM; |
733 | dev_exception_rm(devcgroup, &ex); |
734 | break; |
735 | } |
736 | |
737 | if (!parent_has_perm(devcgroup, &ex)) |
738 | return -EPERM; |
739 | rc = dev_exception_add(devcgroup, &ex); |
740 | break; |
741 | case DEVCG_DENY: |
742 | /* |
743 | * If the default policy is to deny by default, try to remove |
744 | * an matching exception instead. And be silent about it: we |
745 | * don't want to break compatibility |
746 | */ |
747 | if (devcgroup->behavior == DEVCG_DEFAULT_DENY) |
748 | dev_exception_rm(devcgroup, &ex); |
749 | else |
750 | rc = dev_exception_add(devcgroup, &ex); |
751 | |
752 | if (rc) |
753 | break; |
754 | /* we only propagate new restrictions */ |
755 | rc = propagate_exception(devcgroup, &ex); |
756 | break; |
757 | default: |
758 | rc = -EINVAL; |
759 | } |
760 | return rc; |
761 | } |
762 | |
763 | static ssize_t devcgroup_access_write(struct kernfs_open_file *of, |
764 | char *buf, size_t nbytes, loff_t off) |
765 | { |
766 | int retval; |
767 | |
768 | mutex_lock(&devcgroup_mutex); |
769 | retval = devcgroup_update_access(css_to_devcgroup(of_css(of)), |
770 | of_cft(of)->private, strstrip(buf)); |
771 | mutex_unlock(&devcgroup_mutex); |
772 | return retval ?: nbytes; |
773 | } |
774 | |
775 | static struct cftype dev_cgroup_files[] = { |
776 | { |
777 | .name = "allow", |
778 | .write = devcgroup_access_write, |
779 | .private = DEVCG_ALLOW, |
780 | }, |
781 | { |
782 | .name = "deny", |
783 | .write = devcgroup_access_write, |
784 | .private = DEVCG_DENY, |
785 | }, |
786 | { |
787 | .name = "list", |
788 | .seq_show = devcgroup_seq_show, |
789 | .private = DEVCG_LIST, |
790 | }, |
791 | { } /* terminate */ |
792 | }; |
793 | |
794 | struct cgroup_subsys devices_cgrp_subsys = { |
795 | .css_alloc = devcgroup_css_alloc, |
796 | .css_free = devcgroup_css_free, |
797 | .css_online = devcgroup_online, |
798 | .css_offline = devcgroup_offline, |
799 | .legacy_cftypes = dev_cgroup_files, |
800 | }; |
801 | |
802 | /** |
803 | * __devcgroup_check_permission - checks if an inode operation is permitted |
804 | * @dev_cgroup: the dev cgroup to be tested against |
805 | * @type: device type |
806 | * @major: device major number |
807 | * @minor: device minor number |
808 | * @access: combination of ACC_WRITE, ACC_READ and ACC_MKNOD |
809 | * |
810 | * returns 0 on success, -EPERM case the operation is not permitted |
811 | */ |
812 | static int __devcgroup_check_permission(short type, u32 major, u32 minor, |
813 | short access) |
814 | { |
815 | struct dev_cgroup *dev_cgroup; |
816 | bool rc; |
817 | |
818 | rcu_read_lock(); |
819 | dev_cgroup = task_devcgroup(current); |
820 | if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) |
821 | /* Can't match any of the exceptions, even partially */ |
822 | rc = !match_exception_partial(&dev_cgroup->exceptions, |
823 | type, major, minor, access); |
824 | else |
825 | /* Need to match completely one exception to be allowed */ |
826 | rc = match_exception(&dev_cgroup->exceptions, type, major, |
827 | minor, access); |
828 | rcu_read_unlock(); |
829 | |
830 | if (!rc) |
831 | return -EPERM; |
832 | |
833 | return 0; |
834 | } |
835 | |
836 | int __devcgroup_inode_permission(struct inode *inode, int mask) |
837 | { |
838 | short type, access = 0; |
839 | |
840 | if (S_ISBLK(inode->i_mode)) |
841 | type = DEV_BLOCK; |
842 | if (S_ISCHR(inode->i_mode)) |
843 | type = DEV_CHAR; |
844 | if (mask & MAY_WRITE) |
845 | access |= ACC_WRITE; |
846 | if (mask & MAY_READ) |
847 | access |= ACC_READ; |
848 | |
849 | return __devcgroup_check_permission(type, imajor(inode), iminor(inode), |
850 | access); |
851 | } |
852 | |
853 | int devcgroup_inode_mknod(int mode, dev_t dev) |
854 | { |
855 | short type; |
856 | |
857 | if (!S_ISBLK(mode) && !S_ISCHR(mode)) |
858 | return 0; |
859 | |
860 | if (S_ISBLK(mode)) |
861 | type = DEV_BLOCK; |
862 | else |
863 | type = DEV_CHAR; |
864 | |
865 | return __devcgroup_check_permission(type, MAJOR(dev), MINOR(dev), |
866 | ACC_MKNOD); |
867 | |
868 | } |
869 |
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v2.6.34-rc5
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