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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(css)); | |
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(css_parent(&childcg->css)); | |
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(css_parent(&childcg->css)); | |
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 | static inline bool has_children(struct dev_cgroup *devcgroup) | |
591 | { | |
592 | struct cgroup *cgrp = devcgroup->css.cgroup; | |
593 | ||
594 | return !list_empty(&cgrp->children); | |
595 | } | |
596 | ||
597 | /* | |
598 | * Modify the exception list using allow/deny rules. | |
599 | * CAP_SYS_ADMIN is needed for this. It's at least separate from CAP_MKNOD | |
600 | * so we can give a container CAP_MKNOD to let it create devices but not | |
601 | * modify the exception list. | |
602 | * It seems likely we'll want to add a CAP_CONTAINER capability to allow | |
603 | * us to also grant CAP_SYS_ADMIN to containers without giving away the | |
604 | * device exception list controls, but for now we'll stick with CAP_SYS_ADMIN | |
605 | * | |
606 | * Taking rules away is always allowed (given CAP_SYS_ADMIN). Granting | |
607 | * new access is only allowed if you're in the top-level cgroup, or your | |
608 | * parent cgroup has the access you're asking for. | |
609 | */ | |
610 | static int devcgroup_update_access(struct dev_cgroup *devcgroup, | |
611 | int filetype, char *buffer) | |
612 | { | |
613 | const char *b; | |
614 | char temp[12]; /* 11 + 1 characters needed for a u32 */ | |
615 | int count, rc = 0; | |
616 | struct dev_exception_item ex; | |
617 | struct dev_cgroup *parent = css_to_devcgroup(css_parent(&devcgroup->css)); | |
618 | ||
619 | if (!capable(CAP_SYS_ADMIN)) | |
620 | return -EPERM; | |
621 | ||
622 | memset(&ex, 0, sizeof(ex)); | |
623 | b = buffer; | |
624 | ||
625 | switch (*b) { | |
626 | case 'a': | |
627 | switch (filetype) { | |
628 | case DEVCG_ALLOW: | |
629 | if (has_children(devcgroup)) | |
630 | return -EINVAL; | |
631 | ||
632 | if (!may_allow_all(parent)) | |
633 | return -EPERM; | |
634 | dev_exception_clean(devcgroup); | |
635 | devcgroup->behavior = DEVCG_DEFAULT_ALLOW; | |
636 | if (!parent) | |
637 | break; | |
638 | ||
639 | rc = dev_exceptions_copy(&devcgroup->exceptions, | |
640 | &parent->exceptions); | |
641 | if (rc) | |
642 | return rc; | |
643 | break; | |
644 | case DEVCG_DENY: | |
645 | if (has_children(devcgroup)) | |
646 | return -EINVAL; | |
647 | ||
648 | dev_exception_clean(devcgroup); | |
649 | devcgroup->behavior = DEVCG_DEFAULT_DENY; | |
650 | break; | |
651 | default: | |
652 | return -EINVAL; | |
653 | } | |
654 | return 0; | |
655 | case 'b': | |
656 | ex.type = DEV_BLOCK; | |
657 | break; | |
658 | case 'c': | |
659 | ex.type = DEV_CHAR; | |
660 | break; | |
661 | default: | |
662 | return -EINVAL; | |
663 | } | |
664 | b++; | |
665 | if (!isspace(*b)) | |
666 | return -EINVAL; | |
667 | b++; | |
668 | if (*b == '*') { | |
669 | ex.major = ~0; | |
670 | b++; | |
671 | } else if (isdigit(*b)) { | |
672 | memset(temp, 0, sizeof(temp)); | |
673 | for (count = 0; count < sizeof(temp) - 1; count++) { | |
674 | temp[count] = *b; | |
675 | b++; | |
676 | if (!isdigit(*b)) | |
677 | break; | |
678 | } | |
679 | rc = kstrtou32(temp, 10, &ex.major); | |
680 | if (rc) | |
681 | return -EINVAL; | |
682 | } else { | |
683 | return -EINVAL; | |
684 | } | |
685 | if (*b != ':') | |
686 | return -EINVAL; | |
687 | b++; | |
688 | ||
689 | /* read minor */ | |
690 | if (*b == '*') { | |
691 | ex.minor = ~0; | |
692 | b++; | |
693 | } else if (isdigit(*b)) { | |
694 | memset(temp, 0, sizeof(temp)); | |
695 | for (count = 0; count < sizeof(temp) - 1; count++) { | |
696 | temp[count] = *b; | |
697 | b++; | |
698 | if (!isdigit(*b)) | |
699 | break; | |
700 | } | |
701 | rc = kstrtou32(temp, 10, &ex.minor); | |
702 | if (rc) | |
703 | return -EINVAL; | |
704 | } else { | |
705 | return -EINVAL; | |
706 | } | |
707 | if (!isspace(*b)) | |
708 | return -EINVAL; | |
709 | for (b++, count = 0; count < 3; count++, b++) { | |
710 | switch (*b) { | |
711 | case 'r': | |
712 | ex.access |= ACC_READ; | |
713 | break; | |
714 | case 'w': | |
715 | ex.access |= ACC_WRITE; | |
716 | break; | |
717 | case 'm': | |
718 | ex.access |= ACC_MKNOD; | |
719 | break; | |
720 | case '\n': | |
721 | case '\0': | |
722 | count = 3; | |
723 | break; | |
724 | default: | |
725 | return -EINVAL; | |
726 | } | |
727 | } | |
728 | ||
729 | switch (filetype) { | |
730 | case DEVCG_ALLOW: | |
731 | /* | |
732 | * If the default policy is to allow by default, try to remove | |
733 | * an matching exception instead. And be silent about it: we | |
734 | * don't want to break compatibility | |
735 | */ | |
736 | if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) { | |
737 | /* Check if the parent allows removing it first */ | |
738 | if (!parent_allows_removal(devcgroup, &ex)) | |
739 | return -EPERM; | |
740 | dev_exception_rm(devcgroup, &ex); | |
741 | break; | |
742 | } | |
743 | ||
744 | if (!parent_has_perm(devcgroup, &ex)) | |
745 | return -EPERM; | |
746 | rc = dev_exception_add(devcgroup, &ex); | |
747 | break; | |
748 | case DEVCG_DENY: | |
749 | /* | |
750 | * If the default policy is to deny by default, try to remove | |
751 | * an matching exception instead. And be silent about it: we | |
752 | * don't want to break compatibility | |
753 | */ | |
754 | if (devcgroup->behavior == DEVCG_DEFAULT_DENY) | |
755 | dev_exception_rm(devcgroup, &ex); | |
756 | else | |
757 | rc = dev_exception_add(devcgroup, &ex); | |
758 | ||
759 | if (rc) | |
760 | break; | |
761 | /* we only propagate new restrictions */ | |
762 | rc = propagate_exception(devcgroup, &ex); | |
763 | break; | |
764 | default: | |
765 | rc = -EINVAL; | |
766 | } | |
767 | return rc; | |
768 | } | |
769 | ||
770 | static int devcgroup_access_write(struct cgroup_subsys_state *css, | |
771 | struct cftype *cft, char *buffer) | |
772 | { | |
773 | int retval; | |
774 | ||
775 | mutex_lock(&devcgroup_mutex); | |
776 | retval = devcgroup_update_access(css_to_devcgroup(css), | |
777 | cft->private, buffer); | |
778 | mutex_unlock(&devcgroup_mutex); | |
779 | return retval; | |
780 | } | |
781 | ||
782 | static struct cftype dev_cgroup_files[] = { | |
783 | { | |
784 | .name = "allow", | |
785 | .write_string = devcgroup_access_write, | |
786 | .private = DEVCG_ALLOW, | |
787 | }, | |
788 | { | |
789 | .name = "deny", | |
790 | .write_string = devcgroup_access_write, | |
791 | .private = DEVCG_DENY, | |
792 | }, | |
793 | { | |
794 | .name = "list", | |
795 | .seq_show = devcgroup_seq_show, | |
796 | .private = DEVCG_LIST, | |
797 | }, | |
798 | { } /* terminate */ | |
799 | }; | |
800 | ||
801 | struct cgroup_subsys devices_cgrp_subsys = { | |
802 | .css_alloc = devcgroup_css_alloc, | |
803 | .css_free = devcgroup_css_free, | |
804 | .css_online = devcgroup_online, | |
805 | .css_offline = devcgroup_offline, | |
806 | .base_cftypes = dev_cgroup_files, | |
807 | }; | |
808 | ||
809 | /** | |
810 | * __devcgroup_check_permission - checks if an inode operation is permitted | |
811 | * @dev_cgroup: the dev cgroup to be tested against | |
812 | * @type: device type | |
813 | * @major: device major number | |
814 | * @minor: device minor number | |
815 | * @access: combination of ACC_WRITE, ACC_READ and ACC_MKNOD | |
816 | * | |
817 | * returns 0 on success, -EPERM case the operation is not permitted | |
818 | */ | |
819 | static int __devcgroup_check_permission(short type, u32 major, u32 minor, | |
820 | short access) | |
821 | { | |
822 | struct dev_cgroup *dev_cgroup; | |
823 | bool rc; | |
824 | ||
825 | rcu_read_lock(); | |
826 | dev_cgroup = task_devcgroup(current); | |
827 | if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) | |
828 | /* Can't match any of the exceptions, even partially */ | |
829 | rc = !match_exception_partial(&dev_cgroup->exceptions, | |
830 | type, major, minor, access); | |
831 | else | |
832 | /* Need to match completely one exception to be allowed */ | |
833 | rc = match_exception(&dev_cgroup->exceptions, type, major, | |
834 | minor, access); | |
835 | rcu_read_unlock(); | |
836 | ||
837 | if (!rc) | |
838 | return -EPERM; | |
839 | ||
840 | return 0; | |
841 | } | |
842 | ||
843 | int __devcgroup_inode_permission(struct inode *inode, int mask) | |
844 | { | |
845 | short type, access = 0; | |
846 | ||
847 | if (S_ISBLK(inode->i_mode)) | |
848 | type = DEV_BLOCK; | |
849 | if (S_ISCHR(inode->i_mode)) | |
850 | type = DEV_CHAR; | |
851 | if (mask & MAY_WRITE) | |
852 | access |= ACC_WRITE; | |
853 | if (mask & MAY_READ) | |
854 | access |= ACC_READ; | |
855 | ||
856 | return __devcgroup_check_permission(type, imajor(inode), iminor(inode), | |
857 | access); | |
858 | } | |
859 | ||
860 | int devcgroup_inode_mknod(int mode, dev_t dev) | |
861 | { | |
862 | short type; | |
863 | ||
864 | if (!S_ISBLK(mode) && !S_ISCHR(mode)) | |
865 | return 0; | |
866 | ||
867 | if (S_ISBLK(mode)) | |
868 | type = DEV_BLOCK; | |
869 | else | |
870 | type = DEV_CHAR; | |
871 | ||
872 | return __devcgroup_check_permission(type, MAJOR(dev), MINOR(dev), | |
873 | ACC_MKNOD); | |
874 | ||
875 | } |