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8#include <linux/device_cgroup.h>
9#include <linux/cgroup.h>
10#include <linux/ctype.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#ifdef CONFIG_CGROUP_DEVICE
19
20static DEFINE_MUTEX(devcgroup_mutex);
21
22enum devcg_behavior {
23 DEVCG_DEFAULT_NONE,
24 DEVCG_DEFAULT_ALLOW,
25 DEVCG_DEFAULT_DENY,
26};
27
28
29
30
31
32
33
34struct dev_exception_item {
35 u32 major, minor;
36 short type;
37 short access;
38 struct list_head list;
39 struct rcu_head rcu;
40};
41
42struct dev_cgroup {
43 struct cgroup_subsys_state css;
44 struct list_head exceptions;
45 enum devcg_behavior behavior;
46};
47
48static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s)
49{
50 return s ? container_of(s, struct dev_cgroup, css) : NULL;
51}
52
53static inline struct dev_cgroup *task_devcgroup(struct task_struct *task)
54{
55 return css_to_devcgroup(task_css(task, devices_cgrp_id));
56}
57
58
59
60
61static int dev_exceptions_copy(struct list_head *dest, struct list_head *orig)
62{
63 struct dev_exception_item *ex, *tmp, *new;
64
65 lockdep_assert_held(&devcgroup_mutex);
66
67 list_for_each_entry(ex, orig, list) {
68 new = kmemdup(ex, sizeof(*ex), GFP_KERNEL);
69 if (!new)
70 goto free_and_exit;
71 list_add_tail(&new->list, dest);
72 }
73
74 return 0;
75
76free_and_exit:
77 list_for_each_entry_safe(ex, tmp, dest, list) {
78 list_del(&ex->list);
79 kfree(ex);
80 }
81 return -ENOMEM;
82}
83
84
85
86
87static int dev_exception_add(struct dev_cgroup *dev_cgroup,
88 struct dev_exception_item *ex)
89{
90 struct dev_exception_item *excopy, *walk;
91
92 lockdep_assert_held(&devcgroup_mutex);
93
94 excopy = kmemdup(ex, sizeof(*ex), GFP_KERNEL);
95 if (!excopy)
96 return -ENOMEM;
97
98 list_for_each_entry(walk, &dev_cgroup->exceptions, list) {
99 if (walk->type != ex->type)
100 continue;
101 if (walk->major != ex->major)
102 continue;
103 if (walk->minor != ex->minor)
104 continue;
105
106 walk->access |= ex->access;
107 kfree(excopy);
108 excopy = NULL;
109 }
110
111 if (excopy != NULL)
112 list_add_tail_rcu(&excopy->list, &dev_cgroup->exceptions);
113 return 0;
114}
115
116
117
118
119static void dev_exception_rm(struct dev_cgroup *dev_cgroup,
120 struct dev_exception_item *ex)
121{
122 struct dev_exception_item *walk, *tmp;
123
124 lockdep_assert_held(&devcgroup_mutex);
125
126 list_for_each_entry_safe(walk, tmp, &dev_cgroup->exceptions, list) {
127 if (walk->type != ex->type)
128 continue;
129 if (walk->major != ex->major)
130 continue;
131 if (walk->minor != ex->minor)
132 continue;
133
134 walk->access &= ~ex->access;
135 if (!walk->access) {
136 list_del_rcu(&walk->list);
137 kfree_rcu(walk, rcu);
138 }
139 }
140}
141
142static void __dev_exception_clean(struct dev_cgroup *dev_cgroup)
143{
144 struct dev_exception_item *ex, *tmp;
145
146 list_for_each_entry_safe(ex, tmp, &dev_cgroup->exceptions, list) {
147 list_del_rcu(&ex->list);
148 kfree_rcu(ex, rcu);
149 }
150}
151
152
153
154
155
156
157
158static void dev_exception_clean(struct dev_cgroup *dev_cgroup)
159{
160 lockdep_assert_held(&devcgroup_mutex);
161
162 __dev_exception_clean(dev_cgroup);
163}
164
165static inline bool is_devcg_online(const struct dev_cgroup *devcg)
166{
167 return (devcg->behavior != DEVCG_DEFAULT_NONE);
168}
169
170
171
172
173
174
175
176static int devcgroup_online(struct cgroup_subsys_state *css)
177{
178 struct dev_cgroup *dev_cgroup = css_to_devcgroup(css);
179 struct dev_cgroup *parent_dev_cgroup = css_to_devcgroup(css->parent);
180 int ret = 0;
181
182 mutex_lock(&devcgroup_mutex);
183
184 if (parent_dev_cgroup == NULL)
185 dev_cgroup->behavior = DEVCG_DEFAULT_ALLOW;
186 else {
187 ret = dev_exceptions_copy(&dev_cgroup->exceptions,
188 &parent_dev_cgroup->exceptions);
189 if (!ret)
190 dev_cgroup->behavior = parent_dev_cgroup->behavior;
191 }
192 mutex_unlock(&devcgroup_mutex);
193
194 return ret;
195}
196
197static void devcgroup_offline(struct cgroup_subsys_state *css)
198{
199 struct dev_cgroup *dev_cgroup = css_to_devcgroup(css);
200
201 mutex_lock(&devcgroup_mutex);
202 dev_cgroup->behavior = DEVCG_DEFAULT_NONE;
203 mutex_unlock(&devcgroup_mutex);
204}
205
206
207
208
209static struct cgroup_subsys_state *
210devcgroup_css_alloc(struct cgroup_subsys_state *parent_css)
211{
212 struct dev_cgroup *dev_cgroup;
213
214 dev_cgroup = kzalloc(sizeof(*dev_cgroup), GFP_KERNEL);
215 if (!dev_cgroup)
216 return ERR_PTR(-ENOMEM);
217 INIT_LIST_HEAD(&dev_cgroup->exceptions);
218 dev_cgroup->behavior = DEVCG_DEFAULT_NONE;
219
220 return &dev_cgroup->css;
221}
222
223static void devcgroup_css_free(struct cgroup_subsys_state *css)
224{
225 struct dev_cgroup *dev_cgroup = css_to_devcgroup(css);
226
227 __dev_exception_clean(dev_cgroup);
228 kfree(dev_cgroup);
229}
230
231#define DEVCG_ALLOW 1
232#define DEVCG_DENY 2
233#define DEVCG_LIST 3
234
235#define MAJMINLEN 13
236#define ACCLEN 4
237
238static void set_access(char *acc, short access)
239{
240 int idx = 0;
241 memset(acc, 0, ACCLEN);
242 if (access & DEVCG_ACC_READ)
243 acc[idx++] = 'r';
244 if (access & DEVCG_ACC_WRITE)
245 acc[idx++] = 'w';
246 if (access & DEVCG_ACC_MKNOD)
247 acc[idx++] = 'm';
248}
249
250static char type_to_char(short type)
251{
252 if (type == DEVCG_DEV_ALL)
253 return 'a';
254 if (type == DEVCG_DEV_CHAR)
255 return 'c';
256 if (type == DEVCG_DEV_BLOCK)
257 return 'b';
258 return 'X';
259}
260
261static void set_majmin(char *str, unsigned m)
262{
263 if (m == ~0)
264 strcpy(str, "*");
265 else
266 sprintf(str, "%u", m);
267}
268
269static int devcgroup_seq_show(struct seq_file *m, void *v)
270{
271 struct dev_cgroup *devcgroup = css_to_devcgroup(seq_css(m));
272 struct dev_exception_item *ex;
273 char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN];
274
275 rcu_read_lock();
276
277
278
279
280
281
282 if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) {
283 set_access(acc, DEVCG_ACC_MASK);
284 set_majmin(maj, ~0);
285 set_majmin(min, ~0);
286 seq_printf(m, "%c %s:%s %s\n", type_to_char(DEVCG_DEV_ALL),
287 maj, min, acc);
288 } else {
289 list_for_each_entry_rcu(ex, &devcgroup->exceptions, list) {
290 set_access(acc, ex->access);
291 set_majmin(maj, ex->major);
292 set_majmin(min, ex->minor);
293 seq_printf(m, "%c %s:%s %s\n", type_to_char(ex->type),
294 maj, min, acc);
295 }
296 }
297 rcu_read_unlock();
298
299 return 0;
300}
301
302
303
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311
312
313
314
315static bool match_exception(struct list_head *exceptions, short type,
316 u32 major, u32 minor, short access)
317{
318 struct dev_exception_item *ex;
319
320 list_for_each_entry_rcu(ex, exceptions, list) {
321 if ((type & DEVCG_DEV_BLOCK) && !(ex->type & DEVCG_DEV_BLOCK))
322 continue;
323 if ((type & DEVCG_DEV_CHAR) && !(ex->type & DEVCG_DEV_CHAR))
324 continue;
325 if (ex->major != ~0 && ex->major != major)
326 continue;
327 if (ex->minor != ~0 && ex->minor != minor)
328 continue;
329
330 if (access & (~ex->access))
331 continue;
332 return true;
333 }
334 return false;
335}
336
337
338
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349
350
351
352static bool match_exception_partial(struct list_head *exceptions, short type,
353 u32 major, u32 minor, short access)
354{
355 struct dev_exception_item *ex;
356
357 list_for_each_entry_rcu(ex, exceptions, list,
358 lockdep_is_held(&devcgroup_mutex)) {
359 if ((type & DEVCG_DEV_BLOCK) && !(ex->type & DEVCG_DEV_BLOCK))
360 continue;
361 if ((type & DEVCG_DEV_CHAR) && !(ex->type & DEVCG_DEV_CHAR))
362 continue;
363
364
365
366
367 if (ex->major != ~0 && major != ~0 && ex->major != major)
368 continue;
369 if (ex->minor != ~0 && minor != ~0 && ex->minor != minor)
370 continue;
371
372
373
374
375
376 if (!(access & ex->access))
377 continue;
378 return true;
379 }
380 return false;
381}
382
383
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385
386
387
388
389
390
391
392static bool verify_new_ex(struct dev_cgroup *dev_cgroup,
393 struct dev_exception_item *refex,
394 enum devcg_behavior behavior)
395{
396 bool match = false;
397
398 RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&
399 !lockdep_is_held(&devcgroup_mutex),
400 "device_cgroup:verify_new_ex called without proper synchronization");
401
402 if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) {
403 if (behavior == DEVCG_DEFAULT_ALLOW) {
404
405
406
407
408 return true;
409 } else {
410
411
412
413
414
415 match = match_exception_partial(&dev_cgroup->exceptions,
416 refex->type,
417 refex->major,
418 refex->minor,
419 refex->access);
420
421 if (match)
422 return false;
423 return true;
424 }
425 } else {
426
427
428
429
430
431
432 match = match_exception(&dev_cgroup->exceptions, refex->type,
433 refex->major, refex->minor,
434 refex->access);
435
436 if (match)
437
438 return true;
439 else
440 return false;
441 }
442 return false;
443}
444
445
446
447
448
449
450static int parent_has_perm(struct dev_cgroup *childcg,
451 struct dev_exception_item *ex)
452{
453 struct dev_cgroup *parent = css_to_devcgroup(childcg->css.parent);
454
455 if (!parent)
456 return 1;
457 return verify_new_ex(parent, ex, childcg->behavior);
458}
459
460
461
462
463
464
465
466
467
468
469
470
471static bool parent_allows_removal(struct dev_cgroup *childcg,
472 struct dev_exception_item *ex)
473{
474 struct dev_cgroup *parent = css_to_devcgroup(childcg->css.parent);
475
476 if (!parent)
477 return true;
478
479
480 if (childcg->behavior == DEVCG_DEFAULT_DENY)
481 return true;
482
483
484
485
486
487 return !match_exception_partial(&parent->exceptions, ex->type,
488 ex->major, ex->minor, ex->access);
489}
490
491
492
493
494
495
496
497static inline int may_allow_all(struct dev_cgroup *parent)
498{
499 if (!parent)
500 return 1;
501 return parent->behavior == DEVCG_DEFAULT_ALLOW;
502}
503
504
505
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510
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513
514
515
516
517static void revalidate_active_exceptions(struct dev_cgroup *devcg)
518{
519 struct dev_exception_item *ex;
520 struct list_head *this, *tmp;
521
522 list_for_each_safe(this, tmp, &devcg->exceptions) {
523 ex = container_of(this, struct dev_exception_item, list);
524 if (!parent_has_perm(devcg, ex))
525 dev_exception_rm(devcg, ex);
526 }
527}
528
529
530
531
532
533
534
535
536static int propagate_exception(struct dev_cgroup *devcg_root,
537 struct dev_exception_item *ex)
538{
539 struct cgroup_subsys_state *pos;
540 int rc = 0;
541
542 rcu_read_lock();
543
544 css_for_each_descendant_pre(pos, &devcg_root->css) {
545 struct dev_cgroup *devcg = css_to_devcgroup(pos);
546
547
548
549
550
551
552
553 if (pos == &devcg_root->css || !is_devcg_online(devcg))
554 continue;
555
556 rcu_read_unlock();
557
558
559
560
561
562 if (devcg_root->behavior == DEVCG_DEFAULT_ALLOW &&
563 devcg->behavior == DEVCG_DEFAULT_ALLOW) {
564 rc = dev_exception_add(devcg, ex);
565 if (rc)
566 return rc;
567 } else {
568
569
570
571
572
573
574 dev_exception_rm(devcg, ex);
575 }
576 revalidate_active_exceptions(devcg);
577
578 rcu_read_lock();
579 }
580
581 rcu_read_unlock();
582 return rc;
583}
584
585
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592
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594
595
596
597
598static int devcgroup_update_access(struct dev_cgroup *devcgroup,
599 int filetype, char *buffer)
600{
601 const char *b;
602 char temp[12];
603 int count, rc = 0;
604 struct dev_exception_item ex;
605 struct dev_cgroup *parent = css_to_devcgroup(devcgroup->css.parent);
606
607 if (!capable(CAP_SYS_ADMIN))
608 return -EPERM;
609
610 memset(&ex, 0, sizeof(ex));
611 b = buffer;
612
613 switch (*b) {
614 case 'a':
615 switch (filetype) {
616 case DEVCG_ALLOW:
617 if (css_has_online_children(&devcgroup->css))
618 return -EINVAL;
619
620 if (!may_allow_all(parent))
621 return -EPERM;
622 dev_exception_clean(devcgroup);
623 devcgroup->behavior = DEVCG_DEFAULT_ALLOW;
624 if (!parent)
625 break;
626
627 rc = dev_exceptions_copy(&devcgroup->exceptions,
628 &parent->exceptions);
629 if (rc)
630 return rc;
631 break;
632 case DEVCG_DENY:
633 if (css_has_online_children(&devcgroup->css))
634 return -EINVAL;
635
636 dev_exception_clean(devcgroup);
637 devcgroup->behavior = DEVCG_DEFAULT_DENY;
638 break;
639 default:
640 return -EINVAL;
641 }
642 return 0;
643 case 'b':
644 ex.type = DEVCG_DEV_BLOCK;
645 break;
646 case 'c':
647 ex.type = DEVCG_DEV_CHAR;
648 break;
649 default:
650 return -EINVAL;
651 }
652 b++;
653 if (!isspace(*b))
654 return -EINVAL;
655 b++;
656 if (*b == '*') {
657 ex.major = ~0;
658 b++;
659 } else if (isdigit(*b)) {
660 memset(temp, 0, sizeof(temp));
661 for (count = 0; count < sizeof(temp) - 1; count++) {
662 temp[count] = *b;
663 b++;
664 if (!isdigit(*b))
665 break;
666 }
667 rc = kstrtou32(temp, 10, &ex.major);
668 if (rc)
669 return -EINVAL;
670 } else {
671 return -EINVAL;
672 }
673 if (*b != ':')
674 return -EINVAL;
675 b++;
676
677
678 if (*b == '*') {
679 ex.minor = ~0;
680 b++;
681 } else if (isdigit(*b)) {
682 memset(temp, 0, sizeof(temp));
683 for (count = 0; count < sizeof(temp) - 1; count++) {
684 temp[count] = *b;
685 b++;
686 if (!isdigit(*b))
687 break;
688 }
689 rc = kstrtou32(temp, 10, &ex.minor);
690 if (rc)
691 return -EINVAL;
692 } else {
693 return -EINVAL;
694 }
695 if (!isspace(*b))
696 return -EINVAL;
697 for (b++, count = 0; count < 3; count++, b++) {
698 switch (*b) {
699 case 'r':
700 ex.access |= DEVCG_ACC_READ;
701 break;
702 case 'w':
703 ex.access |= DEVCG_ACC_WRITE;
704 break;
705 case 'm':
706 ex.access |= DEVCG_ACC_MKNOD;
707 break;
708 case '\n':
709 case '\0':
710 count = 3;
711 break;
712 default:
713 return -EINVAL;
714 }
715 }
716
717 switch (filetype) {
718 case DEVCG_ALLOW:
719
720
721
722
723
724 if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) {
725
726 if (!parent_allows_removal(devcgroup, &ex))
727 return -EPERM;
728 dev_exception_rm(devcgroup, &ex);
729 break;
730 }
731
732 if (!parent_has_perm(devcgroup, &ex))
733 return -EPERM;
734 rc = dev_exception_add(devcgroup, &ex);
735 break;
736 case DEVCG_DENY:
737
738
739
740
741
742 if (devcgroup->behavior == DEVCG_DEFAULT_DENY)
743 dev_exception_rm(devcgroup, &ex);
744 else
745 rc = dev_exception_add(devcgroup, &ex);
746
747 if (rc)
748 break;
749
750 rc = propagate_exception(devcgroup, &ex);
751 break;
752 default:
753 rc = -EINVAL;
754 }
755 return rc;
756}
757
758static ssize_t devcgroup_access_write(struct kernfs_open_file *of,
759 char *buf, size_t nbytes, loff_t off)
760{
761 int retval;
762
763 mutex_lock(&devcgroup_mutex);
764 retval = devcgroup_update_access(css_to_devcgroup(of_css(of)),
765 of_cft(of)->private, strstrip(buf));
766 mutex_unlock(&devcgroup_mutex);
767 return retval ?: nbytes;
768}
769
770static struct cftype dev_cgroup_files[] = {
771 {
772 .name = "allow",
773 .write = devcgroup_access_write,
774 .private = DEVCG_ALLOW,
775 },
776 {
777 .name = "deny",
778 .write = devcgroup_access_write,
779 .private = DEVCG_DENY,
780 },
781 {
782 .name = "list",
783 .seq_show = devcgroup_seq_show,
784 .private = DEVCG_LIST,
785 },
786 { }
787};
788
789struct cgroup_subsys devices_cgrp_subsys = {
790 .css_alloc = devcgroup_css_alloc,
791 .css_free = devcgroup_css_free,
792 .css_online = devcgroup_online,
793 .css_offline = devcgroup_offline,
794 .legacy_cftypes = dev_cgroup_files,
795};
796
797
798
799
800
801
802
803
804
805
806
807static int devcgroup_legacy_check_permission(short type, u32 major, u32 minor,
808 short access)
809{
810 struct dev_cgroup *dev_cgroup;
811 bool rc;
812
813 rcu_read_lock();
814 dev_cgroup = task_devcgroup(current);
815 if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW)
816
817 rc = !match_exception_partial(&dev_cgroup->exceptions,
818 type, major, minor, access);
819 else
820
821 rc = match_exception(&dev_cgroup->exceptions, type, major,
822 minor, access);
823 rcu_read_unlock();
824
825 if (!rc)
826 return -EPERM;
827
828 return 0;
829}
830
831#endif
832
833#if defined(CONFIG_CGROUP_DEVICE) || defined(CONFIG_CGROUP_BPF)
834
835int devcgroup_check_permission(short type, u32 major, u32 minor, short access)
836{
837 int rc = BPF_CGROUP_RUN_PROG_DEVICE_CGROUP(type, major, minor, access);
838
839 if (rc)
840 return -EPERM;
841
842 #ifdef CONFIG_CGROUP_DEVICE
843 return devcgroup_legacy_check_permission(type, major, minor, access);
844
845 #else
846 return 0;
847
848 #endif
849}
850EXPORT_SYMBOL(devcgroup_check_permission);
851#endif
852