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1 | // SPDX-License-Identifier: GPL-2.0 | |
2 | /* | |
3 | * device_cgroup.c - device cgroup subsystem | |
4 | * | |
5 | * Copyright 2007 IBM Corp | |
6 | */ | |
7 | ||
8 | #include <linux/device_cgroup.h> | |
9 | #include <linux/cgroup.h> | |
10 | #include <linux/ctype.h> | |
11 | #include <linux/export.h> | |
12 | #include <linux/list.h> | |
13 | #include <linux/uaccess.h> | |
14 | #include <linux/seq_file.h> | |
15 | #include <linux/slab.h> | |
16 | #include <linux/rcupdate.h> | |
17 | #include <linux/mutex.h> | |
18 | ||
19 | static DEFINE_MUTEX(devcgroup_mutex); | |
20 | ||
21 | enum devcg_behavior { | |
22 | DEVCG_DEFAULT_NONE, | |
23 | DEVCG_DEFAULT_ALLOW, | |
24 | DEVCG_DEFAULT_DENY, | |
25 | }; | |
26 | ||
27 | /* | |
28 | * exception list locking rules: | |
29 | * hold devcgroup_mutex for update/read. | |
30 | * hold rcu_read_lock() for read. | |
31 | */ | |
32 | ||
33 | struct dev_exception_item { | |
34 | u32 major, minor; | |
35 | short type; | |
36 | short access; | |
37 | struct list_head list; | |
38 | struct rcu_head rcu; | |
39 | }; | |
40 | ||
41 | struct dev_cgroup { | |
42 | struct cgroup_subsys_state css; | |
43 | struct list_head exceptions; | |
44 | enum devcg_behavior behavior; | |
45 | }; | |
46 | ||
47 | static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s) | |
48 | { | |
49 | return s ? container_of(s, struct dev_cgroup, css) : NULL; | |
50 | } | |
51 | ||
52 | static inline struct dev_cgroup *task_devcgroup(struct task_struct *task) | |
53 | { | |
54 | return css_to_devcgroup(task_css(task, devices_cgrp_id)); | |
55 | } | |
56 | ||
57 | /* | |
58 | * called under devcgroup_mutex | |
59 | */ | |
60 | static int dev_exceptions_copy(struct list_head *dest, struct list_head *orig) | |
61 | { | |
62 | struct dev_exception_item *ex, *tmp, *new; | |
63 | ||
64 | lockdep_assert_held(&devcgroup_mutex); | |
65 | ||
66 | list_for_each_entry(ex, orig, list) { | |
67 | new = kmemdup(ex, sizeof(*ex), GFP_KERNEL); | |
68 | if (!new) | |
69 | goto free_and_exit; | |
70 | list_add_tail(&new->list, dest); | |
71 | } | |
72 | ||
73 | return 0; | |
74 | ||
75 | free_and_exit: | |
76 | list_for_each_entry_safe(ex, tmp, dest, list) { | |
77 | list_del(&ex->list); | |
78 | kfree(ex); | |
79 | } | |
80 | return -ENOMEM; | |
81 | } | |
82 | ||
83 | /* | |
84 | * called under devcgroup_mutex | |
85 | */ | |
86 | static int dev_exception_add(struct dev_cgroup *dev_cgroup, | |
87 | struct dev_exception_item *ex) | |
88 | { | |
89 | struct dev_exception_item *excopy, *walk; | |
90 | ||
91 | lockdep_assert_held(&devcgroup_mutex); | |
92 | ||
93 | excopy = kmemdup(ex, sizeof(*ex), GFP_KERNEL); | |
94 | if (!excopy) | |
95 | return -ENOMEM; | |
96 | ||
97 | list_for_each_entry(walk, &dev_cgroup->exceptions, list) { | |
98 | if (walk->type != ex->type) | |
99 | continue; | |
100 | if (walk->major != ex->major) | |
101 | continue; | |
102 | if (walk->minor != ex->minor) | |
103 | continue; | |
104 | ||
105 | walk->access |= ex->access; | |
106 | kfree(excopy); | |
107 | excopy = NULL; | |
108 | } | |
109 | ||
110 | if (excopy != NULL) | |
111 | list_add_tail_rcu(&excopy->list, &dev_cgroup->exceptions); | |
112 | return 0; | |
113 | } | |
114 | ||
115 | /* | |
116 | * called under devcgroup_mutex | |
117 | */ | |
118 | static void dev_exception_rm(struct dev_cgroup *dev_cgroup, | |
119 | struct dev_exception_item *ex) | |
120 | { | |
121 | struct dev_exception_item *walk, *tmp; | |
122 | ||
123 | lockdep_assert_held(&devcgroup_mutex); | |
124 | ||
125 | list_for_each_entry_safe(walk, tmp, &dev_cgroup->exceptions, list) { | |
126 | if (walk->type != ex->type) | |
127 | continue; | |
128 | if (walk->major != ex->major) | |
129 | continue; | |
130 | if (walk->minor != ex->minor) | |
131 | continue; | |
132 | ||
133 | walk->access &= ~ex->access; | |
134 | if (!walk->access) { | |
135 | list_del_rcu(&walk->list); | |
136 | kfree_rcu(walk, rcu); | |
137 | } | |
138 | } | |
139 | } | |
140 | ||
141 | static void __dev_exception_clean(struct dev_cgroup *dev_cgroup) | |
142 | { | |
143 | struct dev_exception_item *ex, *tmp; | |
144 | ||
145 | list_for_each_entry_safe(ex, tmp, &dev_cgroup->exceptions, list) { | |
146 | list_del_rcu(&ex->list); | |
147 | kfree_rcu(ex, rcu); | |
148 | } | |
149 | } | |
150 | ||
151 | /** | |
152 | * dev_exception_clean - frees all entries of the exception list | |
153 | * @dev_cgroup: dev_cgroup with the exception list to be cleaned | |
154 | * | |
155 | * called under devcgroup_mutex | |
156 | */ | |
157 | static void dev_exception_clean(struct dev_cgroup *dev_cgroup) | |
158 | { | |
159 | lockdep_assert_held(&devcgroup_mutex); | |
160 | ||
161 | __dev_exception_clean(dev_cgroup); | |
162 | } | |
163 | ||
164 | static inline bool is_devcg_online(const struct dev_cgroup *devcg) | |
165 | { | |
166 | return (devcg->behavior != DEVCG_DEFAULT_NONE); | |
167 | } | |
168 | ||
169 | /** | |
170 | * devcgroup_online - initializes devcgroup's behavior and exceptions based on | |
171 | * parent's | |
172 | * @css: css getting online | |
173 | * returns 0 in case of success, error code otherwise | |
174 | */ | |
175 | static int devcgroup_online(struct cgroup_subsys_state *css) | |
176 | { | |
177 | struct dev_cgroup *dev_cgroup = css_to_devcgroup(css); | |
178 | struct dev_cgroup *parent_dev_cgroup = css_to_devcgroup(css->parent); | |
179 | int ret = 0; | |
180 | ||
181 | mutex_lock(&devcgroup_mutex); | |
182 | ||
183 | if (parent_dev_cgroup == NULL) | |
184 | dev_cgroup->behavior = DEVCG_DEFAULT_ALLOW; | |
185 | else { | |
186 | ret = dev_exceptions_copy(&dev_cgroup->exceptions, | |
187 | &parent_dev_cgroup->exceptions); | |
188 | if (!ret) | |
189 | dev_cgroup->behavior = parent_dev_cgroup->behavior; | |
190 | } | |
191 | mutex_unlock(&devcgroup_mutex); | |
192 | ||
193 | return ret; | |
194 | } | |
195 | ||
196 | static void devcgroup_offline(struct cgroup_subsys_state *css) | |
197 | { | |
198 | struct dev_cgroup *dev_cgroup = css_to_devcgroup(css); | |
199 | ||
200 | mutex_lock(&devcgroup_mutex); | |
201 | dev_cgroup->behavior = DEVCG_DEFAULT_NONE; | |
202 | mutex_unlock(&devcgroup_mutex); | |
203 | } | |
204 | ||
205 | /* | |
206 | * called from kernel/cgroup.c with cgroup_lock() held. | |
207 | */ | |
208 | static struct cgroup_subsys_state * | |
209 | devcgroup_css_alloc(struct cgroup_subsys_state *parent_css) | |
210 | { | |
211 | struct dev_cgroup *dev_cgroup; | |
212 | ||
213 | dev_cgroup = kzalloc(sizeof(*dev_cgroup), GFP_KERNEL); | |
214 | if (!dev_cgroup) | |
215 | return ERR_PTR(-ENOMEM); | |
216 | INIT_LIST_HEAD(&dev_cgroup->exceptions); | |
217 | dev_cgroup->behavior = DEVCG_DEFAULT_NONE; | |
218 | ||
219 | return &dev_cgroup->css; | |
220 | } | |
221 | ||
222 | static void devcgroup_css_free(struct cgroup_subsys_state *css) | |
223 | { | |
224 | struct dev_cgroup *dev_cgroup = css_to_devcgroup(css); | |
225 | ||
226 | __dev_exception_clean(dev_cgroup); | |
227 | kfree(dev_cgroup); | |
228 | } | |
229 | ||
230 | #define DEVCG_ALLOW 1 | |
231 | #define DEVCG_DENY 2 | |
232 | #define DEVCG_LIST 3 | |
233 | ||
234 | #define MAJMINLEN 13 | |
235 | #define ACCLEN 4 | |
236 | ||
237 | static void set_access(char *acc, short access) | |
238 | { | |
239 | int idx = 0; | |
240 | memset(acc, 0, ACCLEN); | |
241 | if (access & DEVCG_ACC_READ) | |
242 | acc[idx++] = 'r'; | |
243 | if (access & DEVCG_ACC_WRITE) | |
244 | acc[idx++] = 'w'; | |
245 | if (access & DEVCG_ACC_MKNOD) | |
246 | acc[idx++] = 'm'; | |
247 | } | |
248 | ||
249 | static char type_to_char(short type) | |
250 | { | |
251 | if (type == DEVCG_DEV_ALL) | |
252 | return 'a'; | |
253 | if (type == DEVCG_DEV_CHAR) | |
254 | return 'c'; | |
255 | if (type == DEVCG_DEV_BLOCK) | |
256 | return 'b'; | |
257 | return 'X'; | |
258 | } | |
259 | ||
260 | static void set_majmin(char *str, unsigned m) | |
261 | { | |
262 | if (m == ~0) | |
263 | strcpy(str, "*"); | |
264 | else | |
265 | sprintf(str, "%u", m); | |
266 | } | |
267 | ||
268 | static int devcgroup_seq_show(struct seq_file *m, void *v) | |
269 | { | |
270 | struct dev_cgroup *devcgroup = css_to_devcgroup(seq_css(m)); | |
271 | struct dev_exception_item *ex; | |
272 | char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN]; | |
273 | ||
274 | rcu_read_lock(); | |
275 | /* | |
276 | * To preserve the compatibility: | |
277 | * - Only show the "all devices" when the default policy is to allow | |
278 | * - List the exceptions in case the default policy is to deny | |
279 | * This way, the file remains as a "whitelist of devices" | |
280 | */ | |
281 | if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) { | |
282 | set_access(acc, DEVCG_ACC_MASK); | |
283 | set_majmin(maj, ~0); | |
284 | set_majmin(min, ~0); | |
285 | seq_printf(m, "%c %s:%s %s\n", type_to_char(DEVCG_DEV_ALL), | |
286 | maj, min, acc); | |
287 | } else { | |
288 | list_for_each_entry_rcu(ex, &devcgroup->exceptions, list) { | |
289 | set_access(acc, ex->access); | |
290 | set_majmin(maj, ex->major); | |
291 | set_majmin(min, ex->minor); | |
292 | seq_printf(m, "%c %s:%s %s\n", type_to_char(ex->type), | |
293 | maj, min, acc); | |
294 | } | |
295 | } | |
296 | rcu_read_unlock(); | |
297 | ||
298 | return 0; | |
299 | } | |
300 | ||
301 | /** | |
302 | * match_exception - iterates the exception list trying to find a complete match | |
303 | * @exceptions: list of exceptions | |
304 | * @type: device type (DEVCG_DEV_BLOCK or DEVCG_DEV_CHAR) | |
305 | * @major: device file major number, ~0 to match all | |
306 | * @minor: device file minor number, ~0 to match all | |
307 | * @access: permission mask (DEVCG_ACC_READ, DEVCG_ACC_WRITE, DEVCG_ACC_MKNOD) | |
308 | * | |
309 | * It is considered a complete match if an exception is found that will | |
310 | * contain the entire range of provided parameters. | |
311 | * | |
312 | * Return: true in case it matches an exception completely | |
313 | */ | |
314 | static bool match_exception(struct list_head *exceptions, short type, | |
315 | u32 major, u32 minor, short access) | |
316 | { | |
317 | struct dev_exception_item *ex; | |
318 | ||
319 | list_for_each_entry_rcu(ex, exceptions, list) { | |
320 | if ((type & DEVCG_DEV_BLOCK) && !(ex->type & DEVCG_DEV_BLOCK)) | |
321 | continue; | |
322 | if ((type & DEVCG_DEV_CHAR) && !(ex->type & DEVCG_DEV_CHAR)) | |
323 | continue; | |
324 | if (ex->major != ~0 && ex->major != major) | |
325 | continue; | |
326 | if (ex->minor != ~0 && ex->minor != minor) | |
327 | continue; | |
328 | /* provided access cannot have more than the exception rule */ | |
329 | if (access & (~ex->access)) | |
330 | continue; | |
331 | return true; | |
332 | } | |
333 | return false; | |
334 | } | |
335 | ||
336 | /** | |
337 | * match_exception_partial - iterates the exception list trying to find a partial match | |
338 | * @exceptions: list of exceptions | |
339 | * @type: device type (DEVCG_DEV_BLOCK or DEVCG_DEV_CHAR) | |
340 | * @major: device file major number, ~0 to match all | |
341 | * @minor: device file minor number, ~0 to match all | |
342 | * @access: permission mask (DEVCG_ACC_READ, DEVCG_ACC_WRITE, DEVCG_ACC_MKNOD) | |
343 | * | |
344 | * It is considered a partial match if an exception's range is found to | |
345 | * contain *any* of the devices specified by provided parameters. This is | |
346 | * used to make sure no extra access is being granted that is forbidden by | |
347 | * any of the exception list. | |
348 | * | |
349 | * Return: true in case the provided range mat matches an exception completely | |
350 | */ | |
351 | static bool match_exception_partial(struct list_head *exceptions, short type, | |
352 | u32 major, u32 minor, short access) | |
353 | { | |
354 | struct dev_exception_item *ex; | |
355 | ||
356 | list_for_each_entry_rcu(ex, exceptions, list) { | |
357 | if ((type & DEVCG_DEV_BLOCK) && !(ex->type & DEVCG_DEV_BLOCK)) | |
358 | continue; | |
359 | if ((type & DEVCG_DEV_CHAR) && !(ex->type & DEVCG_DEV_CHAR)) | |
360 | continue; | |
361 | /* | |
362 | * We must be sure that both the exception and the provided | |
363 | * range aren't masking all devices | |
364 | */ | |
365 | if (ex->major != ~0 && major != ~0 && ex->major != major) | |
366 | continue; | |
367 | if (ex->minor != ~0 && minor != ~0 && ex->minor != minor) | |
368 | continue; | |
369 | /* | |
370 | * In order to make sure the provided range isn't matching | |
371 | * an exception, all its access bits shouldn't match the | |
372 | * exception's access bits | |
373 | */ | |
374 | if (!(access & ex->access)) | |
375 | continue; | |
376 | return true; | |
377 | } | |
378 | return false; | |
379 | } | |
380 | ||
381 | /** | |
382 | * verify_new_ex - verifies if a new exception is allowed by parent cgroup's permissions | |
383 | * @dev_cgroup: dev cgroup to be tested against | |
384 | * @refex: new exception | |
385 | * @behavior: behavior of the exception's dev_cgroup | |
386 | * | |
387 | * This is used to make sure a child cgroup won't have more privileges | |
388 | * than its parent | |
389 | */ | |
390 | static bool verify_new_ex(struct dev_cgroup *dev_cgroup, | |
391 | struct dev_exception_item *refex, | |
392 | enum devcg_behavior behavior) | |
393 | { | |
394 | bool match = false; | |
395 | ||
396 | RCU_LOCKDEP_WARN(!rcu_read_lock_held() && | |
397 | !lockdep_is_held(&devcgroup_mutex), | |
398 | "device_cgroup:verify_new_ex called without proper synchronization"); | |
399 | ||
400 | if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) { | |
401 | if (behavior == DEVCG_DEFAULT_ALLOW) { | |
402 | /* | |
403 | * new exception in the child doesn't matter, only | |
404 | * adding extra restrictions | |
405 | */ | |
406 | return true; | |
407 | } else { | |
408 | /* | |
409 | * new exception in the child will add more devices | |
410 | * that can be acessed, so it can't match any of | |
411 | * parent's exceptions, even slightly | |
412 | */ | |
413 | match = match_exception_partial(&dev_cgroup->exceptions, | |
414 | refex->type, | |
415 | refex->major, | |
416 | refex->minor, | |
417 | refex->access); | |
418 | ||
419 | if (match) | |
420 | return false; | |
421 | return true; | |
422 | } | |
423 | } else { | |
424 | /* | |
425 | * Only behavior == DEVCG_DEFAULT_DENY allowed here, therefore | |
426 | * the new exception will add access to more devices and must | |
427 | * be contained completely in an parent's exception to be | |
428 | * allowed | |
429 | */ | |
430 | match = match_exception(&dev_cgroup->exceptions, refex->type, | |
431 | refex->major, refex->minor, | |
432 | refex->access); | |
433 | ||
434 | if (match) | |
435 | /* parent has an exception that matches the proposed */ | |
436 | return true; | |
437 | else | |
438 | return false; | |
439 | } | |
440 | return false; | |
441 | } | |
442 | ||
443 | /* | |
444 | * parent_has_perm: | |
445 | * when adding a new allow rule to a device exception list, the rule | |
446 | * must be allowed in the parent device | |
447 | */ | |
448 | static int parent_has_perm(struct dev_cgroup *childcg, | |
449 | struct dev_exception_item *ex) | |
450 | { | |
451 | struct dev_cgroup *parent = css_to_devcgroup(childcg->css.parent); | |
452 | ||
453 | if (!parent) | |
454 | return 1; | |
455 | return verify_new_ex(parent, ex, childcg->behavior); | |
456 | } | |
457 | ||
458 | /** | |
459 | * parent_allows_removal - verify if it's ok to remove an exception | |
460 | * @childcg: child cgroup from where the exception will be removed | |
461 | * @ex: exception being removed | |
462 | * | |
463 | * When removing an exception in cgroups with default ALLOW policy, it must | |
464 | * be checked if removing it will give the child cgroup more access than the | |
465 | * parent. | |
466 | * | |
467 | * Return: true if it's ok to remove exception, false otherwise | |
468 | */ | |
469 | static bool parent_allows_removal(struct dev_cgroup *childcg, | |
470 | struct dev_exception_item *ex) | |
471 | { | |
472 | struct dev_cgroup *parent = css_to_devcgroup(childcg->css.parent); | |
473 | ||
474 | if (!parent) | |
475 | return true; | |
476 | ||
477 | /* It's always allowed to remove access to devices */ | |
478 | if (childcg->behavior == DEVCG_DEFAULT_DENY) | |
479 | return true; | |
480 | ||
481 | /* | |
482 | * Make sure you're not removing part or a whole exception existing in | |
483 | * the parent cgroup | |
484 | */ | |
485 | return !match_exception_partial(&parent->exceptions, ex->type, | |
486 | ex->major, ex->minor, ex->access); | |
487 | } | |
488 | ||
489 | /** | |
490 | * may_allow_all - checks if it's possible to change the behavior to | |
491 | * allow based on parent's rules. | |
492 | * @parent: device cgroup's parent | |
493 | * returns: != 0 in case it's allowed, 0 otherwise | |
494 | */ | |
495 | static inline int may_allow_all(struct dev_cgroup *parent) | |
496 | { | |
497 | if (!parent) | |
498 | return 1; | |
499 | return parent->behavior == DEVCG_DEFAULT_ALLOW; | |
500 | } | |
501 | ||
502 | /** | |
503 | * revalidate_active_exceptions - walks through the active exception list and | |
504 | * revalidates the exceptions based on parent's | |
505 | * behavior and exceptions. The exceptions that | |
506 | * are no longer valid will be removed. | |
507 | * Called with devcgroup_mutex held. | |
508 | * @devcg: cgroup which exceptions will be checked | |
509 | * | |
510 | * This is one of the three key functions for hierarchy implementation. | |
511 | * This function is responsible for re-evaluating all the cgroup's active | |
512 | * exceptions due to a parent's exception change. | |
513 | * Refer to Documentation/cgroups/devices.txt for more details. | |
514 | */ | |
515 | static void revalidate_active_exceptions(struct dev_cgroup *devcg) | |
516 | { | |
517 | struct dev_exception_item *ex; | |
518 | struct list_head *this, *tmp; | |
519 | ||
520 | list_for_each_safe(this, tmp, &devcg->exceptions) { | |
521 | ex = container_of(this, struct dev_exception_item, list); | |
522 | if (!parent_has_perm(devcg, ex)) | |
523 | dev_exception_rm(devcg, ex); | |
524 | } | |
525 | } | |
526 | ||
527 | /** | |
528 | * propagate_exception - propagates a new exception to the children | |
529 | * @devcg_root: device cgroup that added a new exception | |
530 | * @ex: new exception to be propagated | |
531 | * | |
532 | * returns: 0 in case of success, != 0 in case of error | |
533 | */ | |
534 | static int propagate_exception(struct dev_cgroup *devcg_root, | |
535 | struct dev_exception_item *ex) | |
536 | { | |
537 | struct cgroup_subsys_state *pos; | |
538 | int rc = 0; | |
539 | ||
540 | rcu_read_lock(); | |
541 | ||
542 | css_for_each_descendant_pre(pos, &devcg_root->css) { | |
543 | struct dev_cgroup *devcg = css_to_devcgroup(pos); | |
544 | ||
545 | /* | |
546 | * Because devcgroup_mutex is held, no devcg will become | |
547 | * online or offline during the tree walk (see on/offline | |
548 | * methods), and online ones are safe to access outside RCU | |
549 | * read lock without bumping refcnt. | |
550 | */ | |
551 | if (pos == &devcg_root->css || !is_devcg_online(devcg)) | |
552 | continue; | |
553 | ||
554 | rcu_read_unlock(); | |
555 | ||
556 | /* | |
557 | * in case both root's behavior and devcg is allow, a new | |
558 | * restriction means adding to the exception list | |
559 | */ | |
560 | if (devcg_root->behavior == DEVCG_DEFAULT_ALLOW && | |
561 | devcg->behavior == DEVCG_DEFAULT_ALLOW) { | |
562 | rc = dev_exception_add(devcg, ex); | |
563 | if (rc) | |
564 | break; | |
565 | } else { | |
566 | /* | |
567 | * in the other possible cases: | |
568 | * root's behavior: allow, devcg's: deny | |
569 | * root's behavior: deny, devcg's: deny | |
570 | * the exception will be removed | |
571 | */ | |
572 | dev_exception_rm(devcg, ex); | |
573 | } | |
574 | revalidate_active_exceptions(devcg); | |
575 | ||
576 | rcu_read_lock(); | |
577 | } | |
578 | ||
579 | rcu_read_unlock(); | |
580 | return rc; | |
581 | } | |
582 | ||
583 | /* | |
584 | * Modify the exception list using allow/deny rules. | |
585 | * CAP_SYS_ADMIN is needed for this. It's at least separate from CAP_MKNOD | |
586 | * so we can give a container CAP_MKNOD to let it create devices but not | |
587 | * modify the exception list. | |
588 | * It seems likely we'll want to add a CAP_CONTAINER capability to allow | |
589 | * us to also grant CAP_SYS_ADMIN to containers without giving away the | |
590 | * device exception list controls, but for now we'll stick with CAP_SYS_ADMIN | |
591 | * | |
592 | * Taking rules away is always allowed (given CAP_SYS_ADMIN). Granting | |
593 | * new access is only allowed if you're in the top-level cgroup, or your | |
594 | * parent cgroup has the access you're asking for. | |
595 | */ | |
596 | static int devcgroup_update_access(struct dev_cgroup *devcgroup, | |
597 | int filetype, char *buffer) | |
598 | { | |
599 | const char *b; | |
600 | char temp[12]; /* 11 + 1 characters needed for a u32 */ | |
601 | int count, rc = 0; | |
602 | struct dev_exception_item ex; | |
603 | struct dev_cgroup *parent = css_to_devcgroup(devcgroup->css.parent); | |
604 | ||
605 | if (!capable(CAP_SYS_ADMIN)) | |
606 | return -EPERM; | |
607 | ||
608 | memset(&ex, 0, sizeof(ex)); | |
609 | b = buffer; | |
610 | ||
611 | switch (*b) { | |
612 | case 'a': | |
613 | switch (filetype) { | |
614 | case DEVCG_ALLOW: | |
615 | if (css_has_online_children(&devcgroup->css)) | |
616 | return -EINVAL; | |
617 | ||
618 | if (!may_allow_all(parent)) | |
619 | return -EPERM; | |
620 | dev_exception_clean(devcgroup); | |
621 | devcgroup->behavior = DEVCG_DEFAULT_ALLOW; | |
622 | if (!parent) | |
623 | break; | |
624 | ||
625 | rc = dev_exceptions_copy(&devcgroup->exceptions, | |
626 | &parent->exceptions); | |
627 | if (rc) | |
628 | return rc; | |
629 | break; | |
630 | case DEVCG_DENY: | |
631 | if (css_has_online_children(&devcgroup->css)) | |
632 | return -EINVAL; | |
633 | ||
634 | dev_exception_clean(devcgroup); | |
635 | devcgroup->behavior = DEVCG_DEFAULT_DENY; | |
636 | break; | |
637 | default: | |
638 | return -EINVAL; | |
639 | } | |
640 | return 0; | |
641 | case 'b': | |
642 | ex.type = DEVCG_DEV_BLOCK; | |
643 | break; | |
644 | case 'c': | |
645 | ex.type = DEVCG_DEV_CHAR; | |
646 | break; | |
647 | default: | |
648 | return -EINVAL; | |
649 | } | |
650 | b++; | |
651 | if (!isspace(*b)) | |
652 | return -EINVAL; | |
653 | b++; | |
654 | if (*b == '*') { | |
655 | ex.major = ~0; | |
656 | b++; | |
657 | } else if (isdigit(*b)) { | |
658 | memset(temp, 0, sizeof(temp)); | |
659 | for (count = 0; count < sizeof(temp) - 1; count++) { | |
660 | temp[count] = *b; | |
661 | b++; | |
662 | if (!isdigit(*b)) | |
663 | break; | |
664 | } | |
665 | rc = kstrtou32(temp, 10, &ex.major); | |
666 | if (rc) | |
667 | return -EINVAL; | |
668 | } else { | |
669 | return -EINVAL; | |
670 | } | |
671 | if (*b != ':') | |
672 | return -EINVAL; | |
673 | b++; | |
674 | ||
675 | /* read minor */ | |
676 | if (*b == '*') { | |
677 | ex.minor = ~0; | |
678 | b++; | |
679 | } else if (isdigit(*b)) { | |
680 | memset(temp, 0, sizeof(temp)); | |
681 | for (count = 0; count < sizeof(temp) - 1; count++) { | |
682 | temp[count] = *b; | |
683 | b++; | |
684 | if (!isdigit(*b)) | |
685 | break; | |
686 | } | |
687 | rc = kstrtou32(temp, 10, &ex.minor); | |
688 | if (rc) | |
689 | return -EINVAL; | |
690 | } else { | |
691 | return -EINVAL; | |
692 | } | |
693 | if (!isspace(*b)) | |
694 | return -EINVAL; | |
695 | for (b++, count = 0; count < 3; count++, b++) { | |
696 | switch (*b) { | |
697 | case 'r': | |
698 | ex.access |= DEVCG_ACC_READ; | |
699 | break; | |
700 | case 'w': | |
701 | ex.access |= DEVCG_ACC_WRITE; | |
702 | break; | |
703 | case 'm': | |
704 | ex.access |= DEVCG_ACC_MKNOD; | |
705 | break; | |
706 | case '\n': | |
707 | case '\0': | |
708 | count = 3; | |
709 | break; | |
710 | default: | |
711 | return -EINVAL; | |
712 | } | |
713 | } | |
714 | ||
715 | switch (filetype) { | |
716 | case DEVCG_ALLOW: | |
717 | /* | |
718 | * If the default policy is to allow by default, try to remove | |
719 | * an matching exception instead. And be silent about it: we | |
720 | * don't want to break compatibility | |
721 | */ | |
722 | if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) { | |
723 | /* Check if the parent allows removing it first */ | |
724 | if (!parent_allows_removal(devcgroup, &ex)) | |
725 | return -EPERM; | |
726 | dev_exception_rm(devcgroup, &ex); | |
727 | break; | |
728 | } | |
729 | ||
730 | if (!parent_has_perm(devcgroup, &ex)) | |
731 | return -EPERM; | |
732 | rc = dev_exception_add(devcgroup, &ex); | |
733 | break; | |
734 | case DEVCG_DENY: | |
735 | /* | |
736 | * If the default policy is to deny by default, try to remove | |
737 | * an matching exception instead. And be silent about it: we | |
738 | * don't want to break compatibility | |
739 | */ | |
740 | if (devcgroup->behavior == DEVCG_DEFAULT_DENY) | |
741 | dev_exception_rm(devcgroup, &ex); | |
742 | else | |
743 | rc = dev_exception_add(devcgroup, &ex); | |
744 | ||
745 | if (rc) | |
746 | break; | |
747 | /* we only propagate new restrictions */ | |
748 | rc = propagate_exception(devcgroup, &ex); | |
749 | break; | |
750 | default: | |
751 | rc = -EINVAL; | |
752 | } | |
753 | return rc; | |
754 | } | |
755 | ||
756 | static ssize_t devcgroup_access_write(struct kernfs_open_file *of, | |
757 | char *buf, size_t nbytes, loff_t off) | |
758 | { | |
759 | int retval; | |
760 | ||
761 | mutex_lock(&devcgroup_mutex); | |
762 | retval = devcgroup_update_access(css_to_devcgroup(of_css(of)), | |
763 | of_cft(of)->private, strstrip(buf)); | |
764 | mutex_unlock(&devcgroup_mutex); | |
765 | return retval ?: nbytes; | |
766 | } | |
767 | ||
768 | static struct cftype dev_cgroup_files[] = { | |
769 | { | |
770 | .name = "allow", | |
771 | .write = devcgroup_access_write, | |
772 | .private = DEVCG_ALLOW, | |
773 | }, | |
774 | { | |
775 | .name = "deny", | |
776 | .write = devcgroup_access_write, | |
777 | .private = DEVCG_DENY, | |
778 | }, | |
779 | { | |
780 | .name = "list", | |
781 | .seq_show = devcgroup_seq_show, | |
782 | .private = DEVCG_LIST, | |
783 | }, | |
784 | { } /* terminate */ | |
785 | }; | |
786 | ||
787 | struct cgroup_subsys devices_cgrp_subsys = { | |
788 | .css_alloc = devcgroup_css_alloc, | |
789 | .css_free = devcgroup_css_free, | |
790 | .css_online = devcgroup_online, | |
791 | .css_offline = devcgroup_offline, | |
792 | .legacy_cftypes = dev_cgroup_files, | |
793 | }; | |
794 | ||
795 | /** | |
796 | * __devcgroup_check_permission - checks if an inode operation is permitted | |
797 | * @dev_cgroup: the dev cgroup to be tested against | |
798 | * @type: device type | |
799 | * @major: device major number | |
800 | * @minor: device minor number | |
801 | * @access: combination of DEVCG_ACC_WRITE, DEVCG_ACC_READ and DEVCG_ACC_MKNOD | |
802 | * | |
803 | * returns 0 on success, -EPERM case the operation is not permitted | |
804 | */ | |
805 | int __devcgroup_check_permission(short type, u32 major, u32 minor, | |
806 | short access) | |
807 | { | |
808 | struct dev_cgroup *dev_cgroup; | |
809 | bool rc; | |
810 | ||
811 | rcu_read_lock(); | |
812 | dev_cgroup = task_devcgroup(current); | |
813 | if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) | |
814 | /* Can't match any of the exceptions, even partially */ | |
815 | rc = !match_exception_partial(&dev_cgroup->exceptions, | |
816 | type, major, minor, access); | |
817 | else | |
818 | /* Need to match completely one exception to be allowed */ | |
819 | rc = match_exception(&dev_cgroup->exceptions, type, major, | |
820 | minor, access); | |
821 | rcu_read_unlock(); | |
822 | ||
823 | if (!rc) | |
824 | return -EPERM; | |
825 | ||
826 | return 0; | |
827 | } | |
828 | EXPORT_SYMBOL_GPL(__devcgroup_check_permission); |