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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/export.h> | |
11 | #include <linux/list.h> | |
12 | #include <linux/uaccess.h> | |
13 | #include <linux/seq_file.h> | |
14 | #include <linux/slab.h> | |
15 | #include <linux/rcupdate.h> | |
16 | #include <linux/mutex.h> | |
17 | ||
18 | #define ACC_MKNOD 1 | |
19 | #define ACC_READ 2 | |
20 | #define ACC_WRITE 4 | |
21 | #define ACC_MASK (ACC_MKNOD | ACC_READ | ACC_WRITE) | |
22 | ||
23 | #define DEV_BLOCK 1 | |
24 | #define DEV_CHAR 2 | |
25 | #define DEV_ALL 4 /* this represents all devices */ | |
26 | ||
27 | static DEFINE_MUTEX(devcgroup_mutex); | |
28 | ||
29 | enum devcg_behavior { | |
30 | DEVCG_DEFAULT_NONE, | |
31 | DEVCG_DEFAULT_ALLOW, | |
32 | DEVCG_DEFAULT_DENY, | |
33 | }; | |
34 | ||
35 | /* | |
36 | * exception list locking rules: | |
37 | * hold devcgroup_mutex for update/read. | |
38 | * hold rcu_read_lock() for read. | |
39 | */ | |
40 | ||
41 | struct dev_exception_item { | |
42 | u32 major, minor; | |
43 | short type; | |
44 | short access; | |
45 | struct list_head list; | |
46 | struct rcu_head rcu; | |
47 | }; | |
48 | ||
49 | struct dev_cgroup { | |
50 | struct cgroup_subsys_state css; | |
51 | struct list_head exceptions; | |
52 | enum devcg_behavior behavior; | |
53 | }; | |
54 | ||
55 | static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s) | |
56 | { | |
57 | return s ? container_of(s, struct dev_cgroup, css) : NULL; | |
58 | } | |
59 | ||
60 | static inline struct dev_cgroup *task_devcgroup(struct task_struct *task) | |
61 | { | |
62 | return css_to_devcgroup(task_css(task, devices_cgrp_id)); | |
63 | } | |
64 | ||
65 | /* | |
66 | * called under devcgroup_mutex | |
67 | */ | |
68 | static int dev_exceptions_copy(struct list_head *dest, struct list_head *orig) | |
69 | { | |
70 | struct dev_exception_item *ex, *tmp, *new; | |
71 | ||
72 | lockdep_assert_held(&devcgroup_mutex); | |
73 | ||
74 | list_for_each_entry(ex, orig, list) { | |
75 | new = kmemdup(ex, sizeof(*ex), GFP_KERNEL); | |
76 | if (!new) | |
77 | goto free_and_exit; | |
78 | list_add_tail(&new->list, dest); | |
79 | } | |
80 | ||
81 | return 0; | |
82 | ||
83 | free_and_exit: | |
84 | list_for_each_entry_safe(ex, tmp, dest, list) { | |
85 | list_del(&ex->list); | |
86 | kfree(ex); | |
87 | } | |
88 | return -ENOMEM; | |
89 | } | |
90 | ||
91 | /* | |
92 | * called under devcgroup_mutex | |
93 | */ | |
94 | static int dev_exception_add(struct dev_cgroup *dev_cgroup, | |
95 | struct dev_exception_item *ex) | |
96 | { | |
97 | struct dev_exception_item *excopy, *walk; | |
98 | ||
99 | lockdep_assert_held(&devcgroup_mutex); | |
100 | ||
101 | excopy = kmemdup(ex, sizeof(*ex), GFP_KERNEL); | |
102 | if (!excopy) | |
103 | return -ENOMEM; | |
104 | ||
105 | list_for_each_entry(walk, &dev_cgroup->exceptions, list) { | |
106 | if (walk->type != ex->type) | |
107 | continue; | |
108 | if (walk->major != ex->major) | |
109 | continue; | |
110 | if (walk->minor != ex->minor) | |
111 | continue; | |
112 | ||
113 | walk->access |= ex->access; | |
114 | kfree(excopy); | |
115 | excopy = NULL; | |
116 | } | |
117 | ||
118 | if (excopy != NULL) | |
119 | list_add_tail_rcu(&excopy->list, &dev_cgroup->exceptions); | |
120 | return 0; | |
121 | } | |
122 | ||
123 | /* | |
124 | * called under devcgroup_mutex | |
125 | */ | |
126 | static void dev_exception_rm(struct dev_cgroup *dev_cgroup, | |
127 | struct dev_exception_item *ex) | |
128 | { | |
129 | struct dev_exception_item *walk, *tmp; | |
130 | ||
131 | lockdep_assert_held(&devcgroup_mutex); | |
132 | ||
133 | list_for_each_entry_safe(walk, tmp, &dev_cgroup->exceptions, list) { | |
134 | if (walk->type != ex->type) | |
135 | continue; | |
136 | if (walk->major != ex->major) | |
137 | continue; | |
138 | if (walk->minor != ex->minor) | |
139 | continue; | |
140 | ||
141 | walk->access &= ~ex->access; | |
142 | if (!walk->access) { | |
143 | list_del_rcu(&walk->list); | |
144 | kfree_rcu(walk, rcu); | |
145 | } | |
146 | } | |
147 | } | |
148 | ||
149 | static void __dev_exception_clean(struct dev_cgroup *dev_cgroup) | |
150 | { | |
151 | struct dev_exception_item *ex, *tmp; | |
152 | ||
153 | list_for_each_entry_safe(ex, tmp, &dev_cgroup->exceptions, list) { | |
154 | list_del_rcu(&ex->list); | |
155 | kfree_rcu(ex, rcu); | |
156 | } | |
157 | } | |
158 | ||
159 | /** | |
160 | * dev_exception_clean - frees all entries of the exception list | |
161 | * @dev_cgroup: dev_cgroup with the exception list to be cleaned | |
162 | * | |
163 | * called under devcgroup_mutex | |
164 | */ | |
165 | static void dev_exception_clean(struct dev_cgroup *dev_cgroup) | |
166 | { | |
167 | lockdep_assert_held(&devcgroup_mutex); | |
168 | ||
169 | __dev_exception_clean(dev_cgroup); | |
170 | } | |
171 | ||
172 | static inline bool is_devcg_online(const struct dev_cgroup *devcg) | |
173 | { | |
174 | return (devcg->behavior != DEVCG_DEFAULT_NONE); | |
175 | } | |
176 | ||
177 | /** | |
178 | * devcgroup_online - initializes devcgroup's behavior and exceptions based on | |
179 | * parent's | |
180 | * @css: css getting online | |
181 | * returns 0 in case of success, error code otherwise | |
182 | */ | |
183 | static int devcgroup_online(struct cgroup_subsys_state *css) | |
184 | { | |
185 | struct dev_cgroup *dev_cgroup = css_to_devcgroup(css); | |
186 | struct dev_cgroup *parent_dev_cgroup = css_to_devcgroup(css->parent); | |
187 | int ret = 0; | |
188 | ||
189 | mutex_lock(&devcgroup_mutex); | |
190 | ||
191 | if (parent_dev_cgroup == NULL) | |
192 | dev_cgroup->behavior = DEVCG_DEFAULT_ALLOW; | |
193 | else { | |
194 | ret = dev_exceptions_copy(&dev_cgroup->exceptions, | |
195 | &parent_dev_cgroup->exceptions); | |
196 | if (!ret) | |
197 | dev_cgroup->behavior = parent_dev_cgroup->behavior; | |
198 | } | |
199 | mutex_unlock(&devcgroup_mutex); | |
200 | ||
201 | return ret; | |
202 | } | |
203 | ||
204 | static void devcgroup_offline(struct cgroup_subsys_state *css) | |
205 | { | |
206 | struct dev_cgroup *dev_cgroup = css_to_devcgroup(css); | |
207 | ||
208 | mutex_lock(&devcgroup_mutex); | |
209 | dev_cgroup->behavior = DEVCG_DEFAULT_NONE; | |
210 | mutex_unlock(&devcgroup_mutex); | |
211 | } | |
212 | ||
213 | /* | |
214 | * called from kernel/cgroup.c with cgroup_lock() held. | |
215 | */ | |
216 | static struct cgroup_subsys_state * | |
217 | devcgroup_css_alloc(struct cgroup_subsys_state *parent_css) | |
218 | { | |
219 | struct dev_cgroup *dev_cgroup; | |
220 | ||
221 | dev_cgroup = kzalloc(sizeof(*dev_cgroup), GFP_KERNEL); | |
222 | if (!dev_cgroup) | |
223 | return ERR_PTR(-ENOMEM); | |
224 | INIT_LIST_HEAD(&dev_cgroup->exceptions); | |
225 | dev_cgroup->behavior = DEVCG_DEFAULT_NONE; | |
226 | ||
227 | return &dev_cgroup->css; | |
228 | } | |
229 | ||
230 | static void devcgroup_css_free(struct cgroup_subsys_state *css) | |
231 | { | |
232 | struct dev_cgroup *dev_cgroup = css_to_devcgroup(css); | |
233 | ||
234 | __dev_exception_clean(dev_cgroup); | |
235 | kfree(dev_cgroup); | |
236 | } | |
237 | ||
238 | #define DEVCG_ALLOW 1 | |
239 | #define DEVCG_DENY 2 | |
240 | #define DEVCG_LIST 3 | |
241 | ||
242 | #define MAJMINLEN 13 | |
243 | #define ACCLEN 4 | |
244 | ||
245 | static void set_access(char *acc, short access) | |
246 | { | |
247 | int idx = 0; | |
248 | memset(acc, 0, ACCLEN); | |
249 | if (access & ACC_READ) | |
250 | acc[idx++] = 'r'; | |
251 | if (access & ACC_WRITE) | |
252 | acc[idx++] = 'w'; | |
253 | if (access & ACC_MKNOD) | |
254 | acc[idx++] = 'm'; | |
255 | } | |
256 | ||
257 | static char type_to_char(short type) | |
258 | { | |
259 | if (type == DEV_ALL) | |
260 | return 'a'; | |
261 | if (type == DEV_CHAR) | |
262 | return 'c'; | |
263 | if (type == DEV_BLOCK) | |
264 | return 'b'; | |
265 | return 'X'; | |
266 | } | |
267 | ||
268 | static void set_majmin(char *str, unsigned m) | |
269 | { | |
270 | if (m == ~0) | |
271 | strcpy(str, "*"); | |
272 | else | |
273 | sprintf(str, "%u", m); | |
274 | } | |
275 | ||
276 | static int devcgroup_seq_show(struct seq_file *m, void *v) | |
277 | { | |
278 | struct dev_cgroup *devcgroup = css_to_devcgroup(seq_css(m)); | |
279 | struct dev_exception_item *ex; | |
280 | char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN]; | |
281 | ||
282 | rcu_read_lock(); | |
283 | /* | |
284 | * To preserve the compatibility: | |
285 | * - Only show the "all devices" when the default policy is to allow | |
286 | * - List the exceptions in case the default policy is to deny | |
287 | * This way, the file remains as a "whitelist of devices" | |
288 | */ | |
289 | if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) { | |
290 | set_access(acc, ACC_MASK); | |
291 | set_majmin(maj, ~0); | |
292 | set_majmin(min, ~0); | |
293 | seq_printf(m, "%c %s:%s %s\n", type_to_char(DEV_ALL), | |
294 | maj, min, acc); | |
295 | } else { | |
296 | list_for_each_entry_rcu(ex, &devcgroup->exceptions, list) { | |
297 | set_access(acc, ex->access); | |
298 | set_majmin(maj, ex->major); | |
299 | set_majmin(min, ex->minor); | |
300 | seq_printf(m, "%c %s:%s %s\n", type_to_char(ex->type), | |
301 | maj, min, acc); | |
302 | } | |
303 | } | |
304 | rcu_read_unlock(); | |
305 | ||
306 | return 0; | |
307 | } | |
308 | ||
309 | /** | |
310 | * match_exception - iterates the exception list trying to find a complete match | |
311 | * @exceptions: list of exceptions | |
312 | * @type: device type (DEV_BLOCK or DEV_CHAR) | |
313 | * @major: device file major number, ~0 to match all | |
314 | * @minor: device file minor number, ~0 to match all | |
315 | * @access: permission mask (ACC_READ, ACC_WRITE, ACC_MKNOD) | |
316 | * | |
317 | * It is considered a complete match if an exception is found that will | |
318 | * contain the entire range of provided parameters. | |
319 | * | |
320 | * Return: true in case it matches an exception completely | |
321 | */ | |
322 | static bool match_exception(struct list_head *exceptions, short type, | |
323 | u32 major, u32 minor, short access) | |
324 | { | |
325 | struct dev_exception_item *ex; | |
326 | ||
327 | list_for_each_entry_rcu(ex, exceptions, list) { | |
328 | if ((type & DEV_BLOCK) && !(ex->type & DEV_BLOCK)) | |
329 | continue; | |
330 | if ((type & DEV_CHAR) && !(ex->type & DEV_CHAR)) | |
331 | continue; | |
332 | if (ex->major != ~0 && ex->major != major) | |
333 | continue; | |
334 | if (ex->minor != ~0 && ex->minor != minor) | |
335 | continue; | |
336 | /* provided access cannot have more than the exception rule */ | |
337 | if (access & (~ex->access)) | |
338 | continue; | |
339 | return true; | |
340 | } | |
341 | return false; | |
342 | } | |
343 | ||
344 | /** | |
345 | * match_exception_partial - iterates the exception list trying to find a partial match | |
346 | * @exceptions: list of exceptions | |
347 | * @type: device type (DEV_BLOCK or DEV_CHAR) | |
348 | * @major: device file major number, ~0 to match all | |
349 | * @minor: device file minor number, ~0 to match all | |
350 | * @access: permission mask (ACC_READ, ACC_WRITE, ACC_MKNOD) | |
351 | * | |
352 | * It is considered a partial match if an exception's range is found to | |
353 | * contain *any* of the devices specified by provided parameters. This is | |
354 | * used to make sure no extra access is being granted that is forbidden by | |
355 | * any of the exception list. | |
356 | * | |
357 | * Return: true in case the provided range mat matches an exception completely | |
358 | */ | |
359 | static bool match_exception_partial(struct list_head *exceptions, short type, | |
360 | u32 major, u32 minor, short access) | |
361 | { | |
362 | struct dev_exception_item *ex; | |
363 | ||
364 | list_for_each_entry_rcu(ex, exceptions, list) { | |
365 | if ((type & DEV_BLOCK) && !(ex->type & DEV_BLOCK)) | |
366 | continue; | |
367 | if ((type & DEV_CHAR) && !(ex->type & DEV_CHAR)) | |
368 | continue; | |
369 | /* | |
370 | * We must be sure that both the exception and the provided | |
371 | * range aren't masking all devices | |
372 | */ | |
373 | if (ex->major != ~0 && major != ~0 && ex->major != major) | |
374 | continue; | |
375 | if (ex->minor != ~0 && minor != ~0 && ex->minor != minor) | |
376 | continue; | |
377 | /* | |
378 | * In order to make sure the provided range isn't matching | |
379 | * an exception, all its access bits shouldn't match the | |
380 | * exception's access bits | |
381 | */ | |
382 | if (!(access & ex->access)) | |
383 | continue; | |
384 | return true; | |
385 | } | |
386 | return false; | |
387 | } | |
388 | ||
389 | /** | |
390 | * verify_new_ex - verifies if a new exception is allowed by parent cgroup's permissions | |
391 | * @dev_cgroup: dev cgroup to be tested against | |
392 | * @refex: new exception | |
393 | * @behavior: behavior of the exception's dev_cgroup | |
394 | * | |
395 | * This is used to make sure a child cgroup won't have more privileges | |
396 | * than its parent | |
397 | */ | |
398 | static bool verify_new_ex(struct dev_cgroup *dev_cgroup, | |
399 | struct dev_exception_item *refex, | |
400 | enum devcg_behavior behavior) | |
401 | { | |
402 | bool match = false; | |
403 | ||
404 | RCU_LOCKDEP_WARN(!rcu_read_lock_held() && | |
405 | !lockdep_is_held(&devcgroup_mutex), | |
406 | "device_cgroup:verify_new_ex called without proper synchronization"); | |
407 | ||
408 | if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) { | |
409 | if (behavior == DEVCG_DEFAULT_ALLOW) { | |
410 | /* | |
411 | * new exception in the child doesn't matter, only | |
412 | * adding extra restrictions | |
413 | */ | |
414 | return true; | |
415 | } else { | |
416 | /* | |
417 | * new exception in the child will add more devices | |
418 | * that can be acessed, so it can't match any of | |
419 | * parent's exceptions, even slightly | |
420 | */ | |
421 | match = match_exception_partial(&dev_cgroup->exceptions, | |
422 | refex->type, | |
423 | refex->major, | |
424 | refex->minor, | |
425 | refex->access); | |
426 | ||
427 | if (match) | |
428 | return false; | |
429 | return true; | |
430 | } | |
431 | } else { | |
432 | /* | |
433 | * Only behavior == DEVCG_DEFAULT_DENY allowed here, therefore | |
434 | * the new exception will add access to more devices and must | |
435 | * be contained completely in an parent's exception to be | |
436 | * allowed | |
437 | */ | |
438 | match = match_exception(&dev_cgroup->exceptions, refex->type, | |
439 | refex->major, refex->minor, | |
440 | refex->access); | |
441 | ||
442 | if (match) | |
443 | /* parent has an exception that matches the proposed */ | |
444 | return true; | |
445 | else | |
446 | return false; | |
447 | } | |
448 | return false; | |
449 | } | |
450 | ||
451 | /* | |
452 | * parent_has_perm: | |
453 | * when adding a new allow rule to a device exception list, the rule | |
454 | * must be allowed in the parent device | |
455 | */ | |
456 | static int parent_has_perm(struct dev_cgroup *childcg, | |
457 | struct dev_exception_item *ex) | |
458 | { | |
459 | struct dev_cgroup *parent = css_to_devcgroup(childcg->css.parent); | |
460 | ||
461 | if (!parent) | |
462 | return 1; | |
463 | return verify_new_ex(parent, ex, childcg->behavior); | |
464 | } | |
465 | ||
466 | /** | |
467 | * parent_allows_removal - verify if it's ok to remove an exception | |
468 | * @childcg: child cgroup from where the exception will be removed | |
469 | * @ex: exception being removed | |
470 | * | |
471 | * When removing an exception in cgroups with default ALLOW policy, it must | |
472 | * be checked if removing it will give the child cgroup more access than the | |
473 | * parent. | |
474 | * | |
475 | * Return: true if it's ok to remove exception, false otherwise | |
476 | */ | |
477 | static bool parent_allows_removal(struct dev_cgroup *childcg, | |
478 | struct dev_exception_item *ex) | |
479 | { | |
480 | struct dev_cgroup *parent = css_to_devcgroup(childcg->css.parent); | |
481 | ||
482 | if (!parent) | |
483 | return true; | |
484 | ||
485 | /* It's always allowed to remove access to devices */ | |
486 | if (childcg->behavior == DEVCG_DEFAULT_DENY) | |
487 | return true; | |
488 | ||
489 | /* | |
490 | * Make sure you're not removing part or a whole exception existing in | |
491 | * the parent cgroup | |
492 | */ | |
493 | return !match_exception_partial(&parent->exceptions, ex->type, | |
494 | ex->major, ex->minor, ex->access); | |
495 | } | |
496 | ||
497 | /** | |
498 | * may_allow_all - checks if it's possible to change the behavior to | |
499 | * allow based on parent's rules. | |
500 | * @parent: device cgroup's parent | |
501 | * returns: != 0 in case it's allowed, 0 otherwise | |
502 | */ | |
503 | static inline int may_allow_all(struct dev_cgroup *parent) | |
504 | { | |
505 | if (!parent) | |
506 | return 1; | |
507 | return parent->behavior == DEVCG_DEFAULT_ALLOW; | |
508 | } | |
509 | ||
510 | /** | |
511 | * revalidate_active_exceptions - walks through the active exception list and | |
512 | * revalidates the exceptions based on parent's | |
513 | * behavior and exceptions. The exceptions that | |
514 | * are no longer valid will be removed. | |
515 | * Called with devcgroup_mutex held. | |
516 | * @devcg: cgroup which exceptions will be checked | |
517 | * | |
518 | * This is one of the three key functions for hierarchy implementation. | |
519 | * This function is responsible for re-evaluating all the cgroup's active | |
520 | * exceptions due to a parent's exception change. | |
521 | * Refer to Documentation/cgroups/devices.txt for more details. | |
522 | */ | |
523 | static void revalidate_active_exceptions(struct dev_cgroup *devcg) | |
524 | { | |
525 | struct dev_exception_item *ex; | |
526 | struct list_head *this, *tmp; | |
527 | ||
528 | list_for_each_safe(this, tmp, &devcg->exceptions) { | |
529 | ex = container_of(this, struct dev_exception_item, list); | |
530 | if (!parent_has_perm(devcg, ex)) | |
531 | dev_exception_rm(devcg, ex); | |
532 | } | |
533 | } | |
534 | ||
535 | /** | |
536 | * propagate_exception - propagates a new exception to the children | |
537 | * @devcg_root: device cgroup that added a new exception | |
538 | * @ex: new exception to be propagated | |
539 | * | |
540 | * returns: 0 in case of success, != 0 in case of error | |
541 | */ | |
542 | static int propagate_exception(struct dev_cgroup *devcg_root, | |
543 | struct dev_exception_item *ex) | |
544 | { | |
545 | struct cgroup_subsys_state *pos; | |
546 | int rc = 0; | |
547 | ||
548 | rcu_read_lock(); | |
549 | ||
550 | css_for_each_descendant_pre(pos, &devcg_root->css) { | |
551 | struct dev_cgroup *devcg = css_to_devcgroup(pos); | |
552 | ||
553 | /* | |
554 | * Because devcgroup_mutex is held, no devcg will become | |
555 | * online or offline during the tree walk (see on/offline | |
556 | * methods), and online ones are safe to access outside RCU | |
557 | * read lock without bumping refcnt. | |
558 | */ | |
559 | if (pos == &devcg_root->css || !is_devcg_online(devcg)) | |
560 | continue; | |
561 | ||
562 | rcu_read_unlock(); | |
563 | ||
564 | /* | |
565 | * in case both root's behavior and devcg is allow, a new | |
566 | * restriction means adding to the exception list | |
567 | */ | |
568 | if (devcg_root->behavior == DEVCG_DEFAULT_ALLOW && | |
569 | devcg->behavior == DEVCG_DEFAULT_ALLOW) { | |
570 | rc = dev_exception_add(devcg, ex); | |
571 | if (rc) | |
572 | break; | |
573 | } else { | |
574 | /* | |
575 | * in the other possible cases: | |
576 | * root's behavior: allow, devcg's: deny | |
577 | * root's behavior: deny, devcg's: deny | |
578 | * the exception will be removed | |
579 | */ | |
580 | dev_exception_rm(devcg, ex); | |
581 | } | |
582 | revalidate_active_exceptions(devcg); | |
583 | ||
584 | rcu_read_lock(); | |
585 | } | |
586 | ||
587 | rcu_read_unlock(); | |
588 | return rc; | |
589 | } | |
590 | ||
591 | /* | |
592 | * Modify the exception list using allow/deny rules. | |
593 | * CAP_SYS_ADMIN is needed for this. It's at least separate from CAP_MKNOD | |
594 | * so we can give a container CAP_MKNOD to let it create devices but not | |
595 | * modify the exception list. | |
596 | * It seems likely we'll want to add a CAP_CONTAINER capability to allow | |
597 | * us to also grant CAP_SYS_ADMIN to containers without giving away the | |
598 | * device exception list controls, but for now we'll stick with CAP_SYS_ADMIN | |
599 | * | |
600 | * Taking rules away is always allowed (given CAP_SYS_ADMIN). Granting | |
601 | * new access is only allowed if you're in the top-level cgroup, or your | |
602 | * parent cgroup has the access you're asking for. | |
603 | */ | |
604 | static int devcgroup_update_access(struct dev_cgroup *devcgroup, | |
605 | int filetype, char *buffer) | |
606 | { | |
607 | const char *b; | |
608 | char temp[12]; /* 11 + 1 characters needed for a u32 */ | |
609 | int count, rc = 0; | |
610 | struct dev_exception_item ex; | |
611 | struct dev_cgroup *parent = css_to_devcgroup(devcgroup->css.parent); | |
612 | ||
613 | if (!capable(CAP_SYS_ADMIN)) | |
614 | return -EPERM; | |
615 | ||
616 | memset(&ex, 0, sizeof(ex)); | |
617 | b = buffer; | |
618 | ||
619 | switch (*b) { | |
620 | case 'a': | |
621 | switch (filetype) { | |
622 | case DEVCG_ALLOW: | |
623 | if (css_has_online_children(&devcgroup->css)) | |
624 | return -EINVAL; | |
625 | ||
626 | if (!may_allow_all(parent)) | |
627 | return -EPERM; | |
628 | dev_exception_clean(devcgroup); | |
629 | devcgroup->behavior = DEVCG_DEFAULT_ALLOW; | |
630 | if (!parent) | |
631 | break; | |
632 | ||
633 | rc = dev_exceptions_copy(&devcgroup->exceptions, | |
634 | &parent->exceptions); | |
635 | if (rc) | |
636 | return rc; | |
637 | break; | |
638 | case DEVCG_DENY: | |
639 | if (css_has_online_children(&devcgroup->css)) | |
640 | return -EINVAL; | |
641 | ||
642 | dev_exception_clean(devcgroup); | |
643 | devcgroup->behavior = DEVCG_DEFAULT_DENY; | |
644 | break; | |
645 | default: | |
646 | return -EINVAL; | |
647 | } | |
648 | return 0; | |
649 | case 'b': | |
650 | ex.type = DEV_BLOCK; | |
651 | break; | |
652 | case 'c': | |
653 | ex.type = DEV_CHAR; | |
654 | break; | |
655 | default: | |
656 | return -EINVAL; | |
657 | } | |
658 | b++; | |
659 | if (!isspace(*b)) | |
660 | return -EINVAL; | |
661 | b++; | |
662 | if (*b == '*') { | |
663 | ex.major = ~0; | |
664 | b++; | |
665 | } else if (isdigit(*b)) { | |
666 | memset(temp, 0, sizeof(temp)); | |
667 | for (count = 0; count < sizeof(temp) - 1; count++) { | |
668 | temp[count] = *b; | |
669 | b++; | |
670 | if (!isdigit(*b)) | |
671 | break; | |
672 | } | |
673 | rc = kstrtou32(temp, 10, &ex.major); | |
674 | if (rc) | |
675 | return -EINVAL; | |
676 | } else { | |
677 | return -EINVAL; | |
678 | } | |
679 | if (*b != ':') | |
680 | return -EINVAL; | |
681 | b++; | |
682 | ||
683 | /* read minor */ | |
684 | if (*b == '*') { | |
685 | ex.minor = ~0; | |
686 | b++; | |
687 | } else if (isdigit(*b)) { | |
688 | memset(temp, 0, sizeof(temp)); | |
689 | for (count = 0; count < sizeof(temp) - 1; count++) { | |
690 | temp[count] = *b; | |
691 | b++; | |
692 | if (!isdigit(*b)) | |
693 | break; | |
694 | } | |
695 | rc = kstrtou32(temp, 10, &ex.minor); | |
696 | if (rc) | |
697 | return -EINVAL; | |
698 | } else { | |
699 | return -EINVAL; | |
700 | } | |
701 | if (!isspace(*b)) | |
702 | return -EINVAL; | |
703 | for (b++, count = 0; count < 3; count++, b++) { | |
704 | switch (*b) { | |
705 | case 'r': | |
706 | ex.access |= ACC_READ; | |
707 | break; | |
708 | case 'w': | |
709 | ex.access |= ACC_WRITE; | |
710 | break; | |
711 | case 'm': | |
712 | ex.access |= ACC_MKNOD; | |
713 | break; | |
714 | case '\n': | |
715 | case '\0': | |
716 | count = 3; | |
717 | break; | |
718 | default: | |
719 | return -EINVAL; | |
720 | } | |
721 | } | |
722 | ||
723 | switch (filetype) { | |
724 | case DEVCG_ALLOW: | |
725 | /* | |
726 | * If the default policy is to allow by default, try to remove | |
727 | * an matching exception instead. And be silent about it: we | |
728 | * don't want to break compatibility | |
729 | */ | |
730 | if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) { | |
731 | /* Check if the parent allows removing it first */ | |
732 | if (!parent_allows_removal(devcgroup, &ex)) | |
733 | return -EPERM; | |
734 | dev_exception_rm(devcgroup, &ex); | |
735 | break; | |
736 | } | |
737 | ||
738 | if (!parent_has_perm(devcgroup, &ex)) | |
739 | return -EPERM; | |
740 | rc = dev_exception_add(devcgroup, &ex); | |
741 | break; | |
742 | case DEVCG_DENY: | |
743 | /* | |
744 | * If the default policy is to deny by default, try to remove | |
745 | * an matching exception instead. And be silent about it: we | |
746 | * don't want to break compatibility | |
747 | */ | |
748 | if (devcgroup->behavior == DEVCG_DEFAULT_DENY) | |
749 | dev_exception_rm(devcgroup, &ex); | |
750 | else | |
751 | rc = dev_exception_add(devcgroup, &ex); | |
752 | ||
753 | if (rc) | |
754 | break; | |
755 | /* we only propagate new restrictions */ | |
756 | rc = propagate_exception(devcgroup, &ex); | |
757 | break; | |
758 | default: | |
759 | rc = -EINVAL; | |
760 | } | |
761 | return rc; | |
762 | } | |
763 | ||
764 | static ssize_t devcgroup_access_write(struct kernfs_open_file *of, | |
765 | char *buf, size_t nbytes, loff_t off) | |
766 | { | |
767 | int retval; | |
768 | ||
769 | mutex_lock(&devcgroup_mutex); | |
770 | retval = devcgroup_update_access(css_to_devcgroup(of_css(of)), | |
771 | of_cft(of)->private, strstrip(buf)); | |
772 | mutex_unlock(&devcgroup_mutex); | |
773 | return retval ?: nbytes; | |
774 | } | |
775 | ||
776 | static struct cftype dev_cgroup_files[] = { | |
777 | { | |
778 | .name = "allow", | |
779 | .write = devcgroup_access_write, | |
780 | .private = DEVCG_ALLOW, | |
781 | }, | |
782 | { | |
783 | .name = "deny", | |
784 | .write = devcgroup_access_write, | |
785 | .private = DEVCG_DENY, | |
786 | }, | |
787 | { | |
788 | .name = "list", | |
789 | .seq_show = devcgroup_seq_show, | |
790 | .private = DEVCG_LIST, | |
791 | }, | |
792 | { } /* terminate */ | |
793 | }; | |
794 | ||
795 | struct cgroup_subsys devices_cgrp_subsys = { | |
796 | .css_alloc = devcgroup_css_alloc, | |
797 | .css_free = devcgroup_css_free, | |
798 | .css_online = devcgroup_online, | |
799 | .css_offline = devcgroup_offline, | |
800 | .legacy_cftypes = dev_cgroup_files, | |
801 | }; | |
802 | ||
803 | /** | |
804 | * __devcgroup_check_permission - checks if an inode operation is permitted | |
805 | * @dev_cgroup: the dev cgroup to be tested against | |
806 | * @type: device type | |
807 | * @major: device major number | |
808 | * @minor: device minor number | |
809 | * @access: combination of ACC_WRITE, ACC_READ and ACC_MKNOD | |
810 | * | |
811 | * returns 0 on success, -EPERM case the operation is not permitted | |
812 | */ | |
813 | static int __devcgroup_check_permission(short type, u32 major, u32 minor, | |
814 | short access) | |
815 | { | |
816 | struct dev_cgroup *dev_cgroup; | |
817 | bool rc; | |
818 | ||
819 | rcu_read_lock(); | |
820 | dev_cgroup = task_devcgroup(current); | |
821 | if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) | |
822 | /* Can't match any of the exceptions, even partially */ | |
823 | rc = !match_exception_partial(&dev_cgroup->exceptions, | |
824 | type, major, minor, access); | |
825 | else | |
826 | /* Need to match completely one exception to be allowed */ | |
827 | rc = match_exception(&dev_cgroup->exceptions, type, major, | |
828 | minor, access); | |
829 | rcu_read_unlock(); | |
830 | ||
831 | if (!rc) | |
832 | return -EPERM; | |
833 | ||
834 | return 0; | |
835 | } | |
836 | ||
837 | int __devcgroup_inode_permission(struct inode *inode, int mask) | |
838 | { | |
839 | short type, access = 0; | |
840 | ||
841 | if (S_ISBLK(inode->i_mode)) | |
842 | type = DEV_BLOCK; | |
843 | if (S_ISCHR(inode->i_mode)) | |
844 | type = DEV_CHAR; | |
845 | if (mask & MAY_WRITE) | |
846 | access |= ACC_WRITE; | |
847 | if (mask & MAY_READ) | |
848 | access |= ACC_READ; | |
849 | ||
850 | return __devcgroup_check_permission(type, imajor(inode), iminor(inode), | |
851 | access); | |
852 | } | |
853 | EXPORT_SYMBOL_GPL(__devcgroup_inode_permission); | |
854 | ||
855 | int devcgroup_inode_mknod(int mode, dev_t dev) | |
856 | { | |
857 | short type; | |
858 | ||
859 | if (!S_ISBLK(mode) && !S_ISCHR(mode)) | |
860 | return 0; | |
861 | ||
862 | if (S_ISBLK(mode)) | |
863 | type = DEV_BLOCK; | |
864 | else | |
865 | type = DEV_CHAR; | |
866 | ||
867 | return __devcgroup_check_permission(type, MAJOR(dev), MINOR(dev), | |
868 | ACC_MKNOD); | |
869 | ||
870 | } |