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/bpf-cgroup.h>
9 #include <linux/device_cgroup.h>
10 #include <linux/cgroup.h>
11 #include <linux/ctype.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 #ifdef CONFIG_CGROUP_DEVICE
20
21 static DEFINE_MUTEX(devcgroup_mutex);
22
23 enum devcg_behavior {
24 DEVCG_DEFAULT_NONE,
25 DEVCG_DEFAULT_ALLOW,
26 DEVCG_DEFAULT_DENY,
27 };
28
29 /*
30 * exception list locking rules:
31 * hold devcgroup_mutex for update/read.
32 * hold rcu_read_lock() for read.
33 */
34
35 struct dev_exception_item {
36 u32 major, minor;
37 short type;
38 short access;
39 struct list_head list;
40 struct rcu_head rcu;
41 };
42
43 struct dev_cgroup {
44 struct cgroup_subsys_state css;
45 struct list_head exceptions;
46 enum devcg_behavior behavior;
47 };
48
css_to_devcgroup(struct cgroup_subsys_state * s)49 static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s)
50 {
51 return s ? container_of(s, struct dev_cgroup, css) : NULL;
52 }
53
task_devcgroup(struct task_struct * task)54 static inline struct dev_cgroup *task_devcgroup(struct task_struct *task)
55 {
56 return css_to_devcgroup(task_css(task, devices_cgrp_id));
57 }
58
59 /*
60 * called under devcgroup_mutex
61 */
dev_exceptions_copy(struct list_head * dest,struct list_head * orig)62 static int dev_exceptions_copy(struct list_head *dest, struct list_head *orig)
63 {
64 struct dev_exception_item *ex, *tmp, *new;
65
66 lockdep_assert_held(&devcgroup_mutex);
67
68 list_for_each_entry(ex, orig, list) {
69 new = kmemdup(ex, sizeof(*ex), GFP_KERNEL);
70 if (!new)
71 goto free_and_exit;
72 list_add_tail(&new->list, dest);
73 }
74
75 return 0;
76
77 free_and_exit:
78 list_for_each_entry_safe(ex, tmp, dest, list) {
79 list_del(&ex->list);
80 kfree(ex);
81 }
82 return -ENOMEM;
83 }
84
dev_exceptions_move(struct list_head * dest,struct list_head * orig)85 static void dev_exceptions_move(struct list_head *dest, struct list_head *orig)
86 {
87 struct dev_exception_item *ex, *tmp;
88
89 lockdep_assert_held(&devcgroup_mutex);
90
91 list_for_each_entry_safe(ex, tmp, orig, list) {
92 list_move_tail(&ex->list, dest);
93 }
94 }
95
96 /*
97 * called under devcgroup_mutex
98 */
dev_exception_add(struct dev_cgroup * dev_cgroup,struct dev_exception_item * ex)99 static int dev_exception_add(struct dev_cgroup *dev_cgroup,
100 struct dev_exception_item *ex)
101 {
102 struct dev_exception_item *excopy, *walk;
103
104 lockdep_assert_held(&devcgroup_mutex);
105
106 excopy = kmemdup(ex, sizeof(*ex), GFP_KERNEL);
107 if (!excopy)
108 return -ENOMEM;
109
110 list_for_each_entry(walk, &dev_cgroup->exceptions, list) {
111 if (walk->type != ex->type)
112 continue;
113 if (walk->major != ex->major)
114 continue;
115 if (walk->minor != ex->minor)
116 continue;
117
118 walk->access |= ex->access;
119 kfree(excopy);
120 excopy = NULL;
121 }
122
123 if (excopy != NULL)
124 list_add_tail_rcu(&excopy->list, &dev_cgroup->exceptions);
125 return 0;
126 }
127
128 /*
129 * called under devcgroup_mutex
130 */
dev_exception_rm(struct dev_cgroup * dev_cgroup,struct dev_exception_item * ex)131 static void dev_exception_rm(struct dev_cgroup *dev_cgroup,
132 struct dev_exception_item *ex)
133 {
134 struct dev_exception_item *walk, *tmp;
135
136 lockdep_assert_held(&devcgroup_mutex);
137
138 list_for_each_entry_safe(walk, tmp, &dev_cgroup->exceptions, list) {
139 if (walk->type != ex->type)
140 continue;
141 if (walk->major != ex->major)
142 continue;
143 if (walk->minor != ex->minor)
144 continue;
145
146 walk->access &= ~ex->access;
147 if (!walk->access) {
148 list_del_rcu(&walk->list);
149 kfree_rcu(walk, rcu);
150 }
151 }
152 }
153
__dev_exception_clean(struct dev_cgroup * dev_cgroup)154 static void __dev_exception_clean(struct dev_cgroup *dev_cgroup)
155 {
156 struct dev_exception_item *ex, *tmp;
157
158 list_for_each_entry_safe(ex, tmp, &dev_cgroup->exceptions, list) {
159 list_del_rcu(&ex->list);
160 kfree_rcu(ex, rcu);
161 }
162 }
163
164 /**
165 * dev_exception_clean - frees all entries of the exception list
166 * @dev_cgroup: dev_cgroup with the exception list to be cleaned
167 *
168 * called under devcgroup_mutex
169 */
dev_exception_clean(struct dev_cgroup * dev_cgroup)170 static void dev_exception_clean(struct dev_cgroup *dev_cgroup)
171 {
172 lockdep_assert_held(&devcgroup_mutex);
173
174 __dev_exception_clean(dev_cgroup);
175 }
176
is_devcg_online(const struct dev_cgroup * devcg)177 static inline bool is_devcg_online(const struct dev_cgroup *devcg)
178 {
179 return (devcg->behavior != DEVCG_DEFAULT_NONE);
180 }
181
182 /**
183 * devcgroup_online - initializes devcgroup's behavior and exceptions based on
184 * parent's
185 * @css: css getting online
186 * returns 0 in case of success, error code otherwise
187 */
devcgroup_online(struct cgroup_subsys_state * css)188 static int devcgroup_online(struct cgroup_subsys_state *css)
189 {
190 struct dev_cgroup *dev_cgroup = css_to_devcgroup(css);
191 struct dev_cgroup *parent_dev_cgroup = css_to_devcgroup(css->parent);
192 int ret = 0;
193
194 mutex_lock(&devcgroup_mutex);
195
196 if (parent_dev_cgroup == NULL)
197 dev_cgroup->behavior = DEVCG_DEFAULT_ALLOW;
198 else {
199 ret = dev_exceptions_copy(&dev_cgroup->exceptions,
200 &parent_dev_cgroup->exceptions);
201 if (!ret)
202 dev_cgroup->behavior = parent_dev_cgroup->behavior;
203 }
204 mutex_unlock(&devcgroup_mutex);
205
206 return ret;
207 }
208
devcgroup_offline(struct cgroup_subsys_state * css)209 static void devcgroup_offline(struct cgroup_subsys_state *css)
210 {
211 struct dev_cgroup *dev_cgroup = css_to_devcgroup(css);
212
213 mutex_lock(&devcgroup_mutex);
214 dev_cgroup->behavior = DEVCG_DEFAULT_NONE;
215 mutex_unlock(&devcgroup_mutex);
216 }
217
218 /*
219 * called from kernel/cgroup/cgroup.c with cgroup_lock() held.
220 */
221 static struct cgroup_subsys_state *
devcgroup_css_alloc(struct cgroup_subsys_state * parent_css)222 devcgroup_css_alloc(struct cgroup_subsys_state *parent_css)
223 {
224 struct dev_cgroup *dev_cgroup;
225
226 dev_cgroup = kzalloc(sizeof(*dev_cgroup), GFP_KERNEL);
227 if (!dev_cgroup)
228 return ERR_PTR(-ENOMEM);
229 INIT_LIST_HEAD(&dev_cgroup->exceptions);
230 dev_cgroup->behavior = DEVCG_DEFAULT_NONE;
231
232 return &dev_cgroup->css;
233 }
234
devcgroup_css_free(struct cgroup_subsys_state * css)235 static void devcgroup_css_free(struct cgroup_subsys_state *css)
236 {
237 struct dev_cgroup *dev_cgroup = css_to_devcgroup(css);
238
239 __dev_exception_clean(dev_cgroup);
240 kfree(dev_cgroup);
241 }
242
243 #define DEVCG_ALLOW 1
244 #define DEVCG_DENY 2
245 #define DEVCG_LIST 3
246
seq_putaccess(struct seq_file * m,short access)247 static void seq_putaccess(struct seq_file *m, short access)
248 {
249 if (access & DEVCG_ACC_READ)
250 seq_putc(m, 'r');
251 if (access & DEVCG_ACC_WRITE)
252 seq_putc(m, 'w');
253 if (access & DEVCG_ACC_MKNOD)
254 seq_putc(m, 'm');
255 }
256
seq_puttype(struct seq_file * m,short type)257 static void seq_puttype(struct seq_file *m, short type)
258 {
259 if (type == DEVCG_DEV_ALL)
260 seq_putc(m, 'a');
261 else if (type == DEVCG_DEV_CHAR)
262 seq_putc(m, 'c');
263 else if (type == DEVCG_DEV_BLOCK)
264 seq_putc(m, 'b');
265 else
266 seq_putc(m, 'X');
267 }
268
seq_putversion(struct seq_file * m,unsigned int version)269 static void seq_putversion(struct seq_file *m, unsigned int version)
270 {
271 if (version == ~0)
272 seq_putc(m, '*');
273 else
274 seq_printf(m, "%u", version);
275 }
276
devcgroup_seq_show(struct seq_file * m,void * v)277 static int devcgroup_seq_show(struct seq_file *m, void *v)
278 {
279 struct dev_cgroup *devcgroup = css_to_devcgroup(seq_css(m));
280 struct dev_exception_item *ex;
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 seq_puts(m, "a *:* rwm\n");
291 } else {
292 list_for_each_entry_rcu(ex, &devcgroup->exceptions, list) {
293 seq_puttype(m, ex->type);
294 seq_putc(m, ' ');
295 seq_putversion(m, ex->major);
296 seq_putc(m, ':');
297 seq_putversion(m, ex->minor);
298 seq_putc(m, ' ');
299 seq_putaccess(m, ex->access);
300 seq_putc(m, '\n');
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 (DEVCG_DEV_BLOCK or DEVCG_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 (DEVCG_ACC_READ, DEVCG_ACC_WRITE, DEVCG_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 */
match_exception(struct list_head * exceptions,short type,u32 major,u32 minor,short access)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 & DEVCG_DEV_BLOCK) && !(ex->type & DEVCG_DEV_BLOCK))
328 continue;
329 if ((type & DEVCG_DEV_CHAR) && !(ex->type & DEVCG_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 (DEVCG_DEV_BLOCK or DEVCG_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 (DEVCG_ACC_READ, DEVCG_ACC_WRITE, DEVCG_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 */
match_exception_partial(struct list_head * exceptions,short type,u32 major,u32 minor,short access)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 lockdep_is_held(&devcgroup_mutex)) {
365 if ((type & DEVCG_DEV_BLOCK) && !(ex->type & DEVCG_DEV_BLOCK))
366 continue;
367 if ((type & DEVCG_DEV_CHAR) && !(ex->type & DEVCG_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 */
verify_new_ex(struct dev_cgroup * dev_cgroup,struct dev_exception_item * refex,enum devcg_behavior behavior)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 accessed, 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 */
parent_has_perm(struct dev_cgroup * childcg,struct dev_exception_item * ex)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 */
parent_allows_removal(struct dev_cgroup * childcg,struct dev_exception_item * ex)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 */
may_allow_all(struct dev_cgroup * parent)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/admin-guide/cgroup-v1/devices.rst for more details.
522 */
revalidate_active_exceptions(struct dev_cgroup * devcg)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 */
propagate_exception(struct dev_cgroup * devcg_root,struct dev_exception_item * ex)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 return rc;
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 */
devcgroup_update_access(struct dev_cgroup * devcgroup,int filetype,char * buffer)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 struct dev_cgroup tmp_devcgrp;
613
614 if (!capable(CAP_SYS_ADMIN))
615 return -EPERM;
616
617 memset(&ex, 0, sizeof(ex));
618 memset(&tmp_devcgrp, 0, sizeof(tmp_devcgrp));
619 b = buffer;
620
621 switch (*b) {
622 case 'a':
623 switch (filetype) {
624 case DEVCG_ALLOW:
625 if (css_has_online_children(&devcgroup->css))
626 return -EINVAL;
627
628 if (!may_allow_all(parent))
629 return -EPERM;
630 if (!parent) {
631 devcgroup->behavior = DEVCG_DEFAULT_ALLOW;
632 dev_exception_clean(devcgroup);
633 break;
634 }
635
636 INIT_LIST_HEAD(&tmp_devcgrp.exceptions);
637 rc = dev_exceptions_copy(&tmp_devcgrp.exceptions,
638 &devcgroup->exceptions);
639 if (rc)
640 return rc;
641 dev_exception_clean(devcgroup);
642 rc = dev_exceptions_copy(&devcgroup->exceptions,
643 &parent->exceptions);
644 if (rc) {
645 dev_exceptions_move(&devcgroup->exceptions,
646 &tmp_devcgrp.exceptions);
647 return rc;
648 }
649 devcgroup->behavior = DEVCG_DEFAULT_ALLOW;
650 dev_exception_clean(&tmp_devcgrp);
651 break;
652 case DEVCG_DENY:
653 if (css_has_online_children(&devcgroup->css))
654 return -EINVAL;
655
656 dev_exception_clean(devcgroup);
657 devcgroup->behavior = DEVCG_DEFAULT_DENY;
658 break;
659 default:
660 return -EINVAL;
661 }
662 return 0;
663 case 'b':
664 ex.type = DEVCG_DEV_BLOCK;
665 break;
666 case 'c':
667 ex.type = DEVCG_DEV_CHAR;
668 break;
669 default:
670 return -EINVAL;
671 }
672 b++;
673 if (!isspace(*b))
674 return -EINVAL;
675 b++;
676 if (*b == '*') {
677 ex.major = ~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.major);
688 if (rc)
689 return -EINVAL;
690 } else {
691 return -EINVAL;
692 }
693 if (*b != ':')
694 return -EINVAL;
695 b++;
696
697 /* read minor */
698 if (*b == '*') {
699 ex.minor = ~0;
700 b++;
701 } else if (isdigit(*b)) {
702 memset(temp, 0, sizeof(temp));
703 for (count = 0; count < sizeof(temp) - 1; count++) {
704 temp[count] = *b;
705 b++;
706 if (!isdigit(*b))
707 break;
708 }
709 rc = kstrtou32(temp, 10, &ex.minor);
710 if (rc)
711 return -EINVAL;
712 } else {
713 return -EINVAL;
714 }
715 if (!isspace(*b))
716 return -EINVAL;
717 for (b++, count = 0; count < 3; count++, b++) {
718 switch (*b) {
719 case 'r':
720 ex.access |= DEVCG_ACC_READ;
721 break;
722 case 'w':
723 ex.access |= DEVCG_ACC_WRITE;
724 break;
725 case 'm':
726 ex.access |= DEVCG_ACC_MKNOD;
727 break;
728 case '\n':
729 case '\0':
730 count = 3;
731 break;
732 default:
733 return -EINVAL;
734 }
735 }
736
737 switch (filetype) {
738 case DEVCG_ALLOW:
739 /*
740 * If the default policy is to allow by default, try to remove
741 * an matching exception instead. And be silent about it: we
742 * don't want to break compatibility
743 */
744 if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) {
745 /* Check if the parent allows removing it first */
746 if (!parent_allows_removal(devcgroup, &ex))
747 return -EPERM;
748 dev_exception_rm(devcgroup, &ex);
749 break;
750 }
751
752 if (!parent_has_perm(devcgroup, &ex))
753 return -EPERM;
754 rc = dev_exception_add(devcgroup, &ex);
755 break;
756 case DEVCG_DENY:
757 /*
758 * If the default policy is to deny by default, try to remove
759 * an matching exception instead. And be silent about it: we
760 * don't want to break compatibility
761 */
762 if (devcgroup->behavior == DEVCG_DEFAULT_DENY)
763 dev_exception_rm(devcgroup, &ex);
764 else
765 rc = dev_exception_add(devcgroup, &ex);
766
767 if (rc)
768 break;
769 /* we only propagate new restrictions */
770 rc = propagate_exception(devcgroup, &ex);
771 break;
772 default:
773 rc = -EINVAL;
774 }
775 return rc;
776 }
777
devcgroup_access_write(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)778 static ssize_t devcgroup_access_write(struct kernfs_open_file *of,
779 char *buf, size_t nbytes, loff_t off)
780 {
781 int retval;
782
783 mutex_lock(&devcgroup_mutex);
784 retval = devcgroup_update_access(css_to_devcgroup(of_css(of)),
785 of_cft(of)->private, strstrip(buf));
786 mutex_unlock(&devcgroup_mutex);
787 return retval ?: nbytes;
788 }
789
790 static struct cftype dev_cgroup_files[] = {
791 {
792 .name = "allow",
793 .write = devcgroup_access_write,
794 .private = DEVCG_ALLOW,
795 },
796 {
797 .name = "deny",
798 .write = devcgroup_access_write,
799 .private = DEVCG_DENY,
800 },
801 {
802 .name = "list",
803 .seq_show = devcgroup_seq_show,
804 .private = DEVCG_LIST,
805 },
806 { } /* terminate */
807 };
808
809 struct cgroup_subsys devices_cgrp_subsys = {
810 .css_alloc = devcgroup_css_alloc,
811 .css_free = devcgroup_css_free,
812 .css_online = devcgroup_online,
813 .css_offline = devcgroup_offline,
814 .legacy_cftypes = dev_cgroup_files,
815 };
816
817 /**
818 * devcgroup_legacy_check_permission - checks if an inode operation is permitted
819 * @type: device type
820 * @major: device major number
821 * @minor: device minor number
822 * @access: combination of DEVCG_ACC_WRITE, DEVCG_ACC_READ and DEVCG_ACC_MKNOD
823 *
824 * returns 0 on success, -EPERM case the operation is not permitted
825 */
devcgroup_legacy_check_permission(short type,u32 major,u32 minor,short access)826 static int devcgroup_legacy_check_permission(short type, u32 major, u32 minor,
827 short access)
828 {
829 struct dev_cgroup *dev_cgroup;
830 bool rc;
831
832 rcu_read_lock();
833 dev_cgroup = task_devcgroup(current);
834 if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW)
835 /* Can't match any of the exceptions, even partially */
836 rc = !match_exception_partial(&dev_cgroup->exceptions,
837 type, major, minor, access);
838 else
839 /* Need to match completely one exception to be allowed */
840 rc = match_exception(&dev_cgroup->exceptions, type, major,
841 minor, access);
842 rcu_read_unlock();
843
844 if (!rc)
845 return -EPERM;
846
847 return 0;
848 }
849
850 #endif /* CONFIG_CGROUP_DEVICE */
851
852 #if defined(CONFIG_CGROUP_DEVICE) || defined(CONFIG_CGROUP_BPF)
853
devcgroup_check_permission(short type,u32 major,u32 minor,short access)854 int devcgroup_check_permission(short type, u32 major, u32 minor, short access)
855 {
856 int rc = BPF_CGROUP_RUN_PROG_DEVICE_CGROUP(type, major, minor, access);
857
858 if (rc)
859 return rc;
860
861 #ifdef CONFIG_CGROUP_DEVICE
862 return devcgroup_legacy_check_permission(type, major, minor, access);
863
864 #else /* CONFIG_CGROUP_DEVICE */
865 return 0;
866
867 #endif /* CONFIG_CGROUP_DEVICE */
868 }
869 EXPORT_SYMBOL(devcgroup_check_permission);
870 #endif /* defined(CONFIG_CGROUP_DEVICE) || defined(CONFIG_CGROUP_BPF) */
871