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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
25
26static DEFINE_MUTEX(devcgroup_mutex);
27
28
29
30
31
32
33
34struct dev_whitelist_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 whitelist;
45};
46
47static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s)
48{
49 return container_of(s, struct dev_cgroup, css);
50}
51
52static inline struct dev_cgroup *cgroup_to_devcgroup(struct cgroup *cgroup)
53{
54 return css_to_devcgroup(cgroup_subsys_state(cgroup, devices_subsys_id));
55}
56
57static inline struct dev_cgroup *task_devcgroup(struct task_struct *task)
58{
59 return css_to_devcgroup(task_subsys_state(task, devices_subsys_id));
60}
61
62struct cgroup_subsys devices_subsys;
63
64static int devcgroup_can_attach(struct cgroup_subsys *ss,
65 struct cgroup *new_cgroup, struct task_struct *task,
66 bool threadgroup)
67{
68 if (current != task && !capable(CAP_SYS_ADMIN))
69 return -EPERM;
70
71 return 0;
72}
73
74
75
76
77static int dev_whitelist_copy(struct list_head *dest, struct list_head *orig)
78{
79 struct dev_whitelist_item *wh, *tmp, *new;
80
81 list_for_each_entry(wh, orig, list) {
82 new = kmemdup(wh, sizeof(*wh), GFP_KERNEL);
83 if (!new)
84 goto free_and_exit;
85 list_add_tail(&new->list, dest);
86 }
87
88 return 0;
89
90free_and_exit:
91 list_for_each_entry_safe(wh, tmp, dest, list) {
92 list_del(&wh->list);
93 kfree(wh);
94 }
95 return -ENOMEM;
96}
97
98
99
100
101
102static int dev_whitelist_add(struct dev_cgroup *dev_cgroup,
103 struct dev_whitelist_item *wh)
104{
105 struct dev_whitelist_item *whcopy, *walk;
106
107 whcopy = kmemdup(wh, sizeof(*wh), GFP_KERNEL);
108 if (!whcopy)
109 return -ENOMEM;
110
111 list_for_each_entry(walk, &dev_cgroup->whitelist, list) {
112 if (walk->type != wh->type)
113 continue;
114 if (walk->major != wh->major)
115 continue;
116 if (walk->minor != wh->minor)
117 continue;
118
119 walk->access |= wh->access;
120 kfree(whcopy);
121 whcopy = NULL;
122 }
123
124 if (whcopy != NULL)
125 list_add_tail_rcu(&whcopy->list, &dev_cgroup->whitelist);
126 return 0;
127}
128
129static void whitelist_item_free(struct rcu_head *rcu)
130{
131 struct dev_whitelist_item *item;
132
133 item = container_of(rcu, struct dev_whitelist_item, rcu);
134 kfree(item);
135}
136
137
138
139
140static void dev_whitelist_rm(struct dev_cgroup *dev_cgroup,
141 struct dev_whitelist_item *wh)
142{
143 struct dev_whitelist_item *walk, *tmp;
144
145 list_for_each_entry_safe(walk, tmp, &dev_cgroup->whitelist, list) {
146 if (walk->type == DEV_ALL)
147 goto remove;
148 if (walk->type != wh->type)
149 continue;
150 if (walk->major != ~0 && walk->major != wh->major)
151 continue;
152 if (walk->minor != ~0 && walk->minor != wh->minor)
153 continue;
154
155remove:
156 walk->access &= ~wh->access;
157 if (!walk->access) {
158 list_del_rcu(&walk->list);
159 call_rcu(&walk->rcu, whitelist_item_free);
160 }
161 }
162}
163
164
165
166
167static struct cgroup_subsys_state *devcgroup_create(struct cgroup_subsys *ss,
168 struct cgroup *cgroup)
169{
170 struct dev_cgroup *dev_cgroup, *parent_dev_cgroup;
171 struct cgroup *parent_cgroup;
172 int ret;
173
174 dev_cgroup = kzalloc(sizeof(*dev_cgroup), GFP_KERNEL);
175 if (!dev_cgroup)
176 return ERR_PTR(-ENOMEM);
177 INIT_LIST_HEAD(&dev_cgroup->whitelist);
178 parent_cgroup = cgroup->parent;
179
180 if (parent_cgroup == NULL) {
181 struct dev_whitelist_item *wh;
182 wh = kmalloc(sizeof(*wh), GFP_KERNEL);
183 if (!wh) {
184 kfree(dev_cgroup);
185 return ERR_PTR(-ENOMEM);
186 }
187 wh->minor = wh->major = ~0;
188 wh->type = DEV_ALL;
189 wh->access = ACC_MASK;
190 list_add(&wh->list, &dev_cgroup->whitelist);
191 } else {
192 parent_dev_cgroup = cgroup_to_devcgroup(parent_cgroup);
193 mutex_lock(&devcgroup_mutex);
194 ret = dev_whitelist_copy(&dev_cgroup->whitelist,
195 &parent_dev_cgroup->whitelist);
196 mutex_unlock(&devcgroup_mutex);
197 if (ret) {
198 kfree(dev_cgroup);
199 return ERR_PTR(ret);
200 }
201 }
202
203 return &dev_cgroup->css;
204}
205
206static void devcgroup_destroy(struct cgroup_subsys *ss,
207 struct cgroup *cgroup)
208{
209 struct dev_cgroup *dev_cgroup;
210 struct dev_whitelist_item *wh, *tmp;
211
212 dev_cgroup = cgroup_to_devcgroup(cgroup);
213 list_for_each_entry_safe(wh, tmp, &dev_cgroup->whitelist, list) {
214 list_del(&wh->list);
215 kfree(wh);
216 }
217 kfree(dev_cgroup);
218}
219
220#define DEVCG_ALLOW 1
221#define DEVCG_DENY 2
222#define DEVCG_LIST 3
223
224#define MAJMINLEN 13
225#define ACCLEN 4
226
227static void set_access(char *acc, short access)
228{
229 int idx = 0;
230 memset(acc, 0, ACCLEN);
231 if (access & ACC_READ)
232 acc[idx++] = 'r';
233 if (access & ACC_WRITE)
234 acc[idx++] = 'w';
235 if (access & ACC_MKNOD)
236 acc[idx++] = 'm';
237}
238
239static char type_to_char(short type)
240{
241 if (type == DEV_ALL)
242 return 'a';
243 if (type == DEV_CHAR)
244 return 'c';
245 if (type == DEV_BLOCK)
246 return 'b';
247 return 'X';
248}
249
250static void set_majmin(char *str, unsigned m)
251{
252 if (m == ~0)
253 strcpy(str, "*");
254 else
255 sprintf(str, "%u", m);
256}
257
258static int devcgroup_seq_read(struct cgroup *cgroup, struct cftype *cft,
259 struct seq_file *m)
260{
261 struct dev_cgroup *devcgroup = cgroup_to_devcgroup(cgroup);
262 struct dev_whitelist_item *wh;
263 char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN];
264
265 rcu_read_lock();
266 list_for_each_entry_rcu(wh, &devcgroup->whitelist, list) {
267 set_access(acc, wh->access);
268 set_majmin(maj, wh->major);
269 set_majmin(min, wh->minor);
270 seq_printf(m, "%c %s:%s %s\n", type_to_char(wh->type),
271 maj, min, acc);
272 }
273 rcu_read_unlock();
274
275 return 0;
276}
277
278
279
280
281
282
283
284
285static int may_access_whitelist(struct dev_cgroup *c,
286 struct dev_whitelist_item *refwh)
287{
288 struct dev_whitelist_item *whitem;
289
290 list_for_each_entry(whitem, &c->whitelist, list) {
291 if (whitem->type & DEV_ALL)
292 return 1;
293 if ((refwh->type & DEV_BLOCK) && !(whitem->type & DEV_BLOCK))
294 continue;
295 if ((refwh->type & DEV_CHAR) && !(whitem->type & DEV_CHAR))
296 continue;
297 if (whitem->major != ~0 && whitem->major != refwh->major)
298 continue;
299 if (whitem->minor != ~0 && whitem->minor != refwh->minor)
300 continue;
301 if (refwh->access & (~whitem->access))
302 continue;
303 return 1;
304 }
305 return 0;
306}
307
308
309
310
311
312
313static int parent_has_perm(struct dev_cgroup *childcg,
314 struct dev_whitelist_item *wh)
315{
316 struct cgroup *pcg = childcg->css.cgroup->parent;
317 struct dev_cgroup *parent;
318
319 if (!pcg)
320 return 1;
321 parent = cgroup_to_devcgroup(pcg);
322 return may_access_whitelist(parent, wh);
323}
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338static int devcgroup_update_access(struct dev_cgroup *devcgroup,
339 int filetype, const char *buffer)
340{
341 const char *b;
342 char *endp;
343 int count;
344 struct dev_whitelist_item wh;
345
346 if (!capable(CAP_SYS_ADMIN))
347 return -EPERM;
348
349 memset(&wh, 0, sizeof(wh));
350 b = buffer;
351
352 switch (*b) {
353 case 'a':
354 wh.type = DEV_ALL;
355 wh.access = ACC_MASK;
356 wh.major = ~0;
357 wh.minor = ~0;
358 goto handle;
359 case 'b':
360 wh.type = DEV_BLOCK;
361 break;
362 case 'c':
363 wh.type = DEV_CHAR;
364 break;
365 default:
366 return -EINVAL;
367 }
368 b++;
369 if (!isspace(*b))
370 return -EINVAL;
371 b++;
372 if (*b == '*') {
373 wh.major = ~0;
374 b++;
375 } else if (isdigit(*b)) {
376 wh.major = simple_strtoul(b, &endp, 10);
377 b = endp;
378 } else {
379 return -EINVAL;
380 }
381 if (*b != ':')
382 return -EINVAL;
383 b++;
384
385
386 if (*b == '*') {
387 wh.minor = ~0;
388 b++;
389 } else if (isdigit(*b)) {
390 wh.minor = simple_strtoul(b, &endp, 10);
391 b = endp;
392 } else {
393 return -EINVAL;
394 }
395 if (!isspace(*b))
396 return -EINVAL;
397 for (b++, count = 0; count < 3; count++, b++) {
398 switch (*b) {
399 case 'r':
400 wh.access |= ACC_READ;
401 break;
402 case 'w':
403 wh.access |= ACC_WRITE;
404 break;
405 case 'm':
406 wh.access |= ACC_MKNOD;
407 break;
408 case '\n':
409 case '\0':
410 count = 3;
411 break;
412 default:
413 return -EINVAL;
414 }
415 }
416
417handle:
418 switch (filetype) {
419 case DEVCG_ALLOW:
420 if (!parent_has_perm(devcgroup, &wh))
421 return -EPERM;
422 return dev_whitelist_add(devcgroup, &wh);
423 case DEVCG_DENY:
424 dev_whitelist_rm(devcgroup, &wh);
425 break;
426 default:
427 return -EINVAL;
428 }
429 return 0;
430}
431
432static int devcgroup_access_write(struct cgroup *cgrp, struct cftype *cft,
433 const char *buffer)
434{
435 int retval;
436
437 mutex_lock(&devcgroup_mutex);
438 retval = devcgroup_update_access(cgroup_to_devcgroup(cgrp),
439 cft->private, buffer);
440 mutex_unlock(&devcgroup_mutex);
441 return retval;
442}
443
444static struct cftype dev_cgroup_files[] = {
445 {
446 .name = "allow",
447 .write_string = devcgroup_access_write,
448 .private = DEVCG_ALLOW,
449 },
450 {
451 .name = "deny",
452 .write_string = devcgroup_access_write,
453 .private = DEVCG_DENY,
454 },
455 {
456 .name = "list",
457 .read_seq_string = devcgroup_seq_read,
458 .private = DEVCG_LIST,
459 },
460};
461
462static int devcgroup_populate(struct cgroup_subsys *ss,
463 struct cgroup *cgroup)
464{
465 return cgroup_add_files(cgroup, ss, dev_cgroup_files,
466 ARRAY_SIZE(dev_cgroup_files));
467}
468
469struct cgroup_subsys devices_subsys = {
470 .name = "devices",
471 .can_attach = devcgroup_can_attach,
472 .create = devcgroup_create,
473 .destroy = devcgroup_destroy,
474 .populate = devcgroup_populate,
475 .subsys_id = devices_subsys_id,
476};
477
478int devcgroup_inode_permission(struct inode *inode, int mask)
479{
480 struct dev_cgroup *dev_cgroup;
481 struct dev_whitelist_item *wh;
482
483 dev_t device = inode->i_rdev;
484 if (!device)
485 return 0;
486 if (!S_ISBLK(inode->i_mode) && !S_ISCHR(inode->i_mode))
487 return 0;
488
489 rcu_read_lock();
490
491 dev_cgroup = task_devcgroup(current);
492
493 list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) {
494 if (wh->type & DEV_ALL)
495 goto found;
496 if ((wh->type & DEV_BLOCK) && !S_ISBLK(inode->i_mode))
497 continue;
498 if ((wh->type & DEV_CHAR) && !S_ISCHR(inode->i_mode))
499 continue;
500 if (wh->major != ~0 && wh->major != imajor(inode))
501 continue;
502 if (wh->minor != ~0 && wh->minor != iminor(inode))
503 continue;
504
505 if ((mask & MAY_WRITE) && !(wh->access & ACC_WRITE))
506 continue;
507 if ((mask & MAY_READ) && !(wh->access & ACC_READ))
508 continue;
509found:
510 rcu_read_unlock();
511 return 0;
512 }
513
514 rcu_read_unlock();
515
516 return -EPERM;
517}
518
519int devcgroup_inode_mknod(int mode, dev_t dev)
520{
521 struct dev_cgroup *dev_cgroup;
522 struct dev_whitelist_item *wh;
523
524 if (!S_ISBLK(mode) && !S_ISCHR(mode))
525 return 0;
526
527 rcu_read_lock();
528
529 dev_cgroup = task_devcgroup(current);
530
531 list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) {
532 if (wh->type & DEV_ALL)
533 goto found;
534 if ((wh->type & DEV_BLOCK) && !S_ISBLK(mode))
535 continue;
536 if ((wh->type & DEV_CHAR) && !S_ISCHR(mode))
537 continue;
538 if (wh->major != ~0 && wh->major != MAJOR(dev))
539 continue;
540 if (wh->minor != ~0 && wh->minor != MINOR(dev))
541 continue;
542
543 if (!(wh->access & ACC_MKNOD))
544 continue;
545found:
546 rcu_read_unlock();
547 return 0;
548 }
549
550 rcu_read_unlock();
551
552 return -EPERM;
553}
554
