Commit | Line | Data |
---|---|---|
08ce5f16 SH |
1 | /* |
2 | * dev_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> | |
29486df3 | 12 | #include <linux/seq_file.h> |
08ce5f16 SH |
13 | |
14 | #define ACC_MKNOD 1 | |
15 | #define ACC_READ 2 | |
16 | #define ACC_WRITE 4 | |
17 | #define ACC_MASK (ACC_MKNOD | ACC_READ | ACC_WRITE) | |
18 | ||
19 | #define DEV_BLOCK 1 | |
20 | #define DEV_CHAR 2 | |
21 | #define DEV_ALL 4 /* this represents all devices */ | |
22 | ||
23 | /* | |
24 | * whitelist locking rules: | |
25 | * cgroup_lock() cannot be taken under dev_cgroup->lock. | |
26 | * dev_cgroup->lock can be taken with or without cgroup_lock(). | |
27 | * | |
28 | * modifications always require cgroup_lock | |
29 | * modifications to a list which is visible require the | |
30 | * dev_cgroup->lock *and* cgroup_lock() | |
31 | * walking the list requires dev_cgroup->lock or cgroup_lock(). | |
32 | * | |
33 | * reasoning: dev_whitelist_copy() needs to kmalloc, so needs | |
34 | * a mutex, which the cgroup_lock() is. Since modifying | |
35 | * a visible list requires both locks, either lock can be | |
36 | * taken for walking the list. | |
37 | */ | |
38 | ||
39 | struct dev_whitelist_item { | |
40 | u32 major, minor; | |
41 | short type; | |
42 | short access; | |
43 | struct list_head list; | |
44 | }; | |
45 | ||
46 | struct dev_cgroup { | |
47 | struct cgroup_subsys_state css; | |
48 | struct list_head whitelist; | |
49 | spinlock_t lock; | |
50 | }; | |
51 | ||
b66862f7 PE |
52 | static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s) |
53 | { | |
54 | return container_of(s, struct dev_cgroup, css); | |
55 | } | |
56 | ||
08ce5f16 SH |
57 | static inline struct dev_cgroup *cgroup_to_devcgroup(struct cgroup *cgroup) |
58 | { | |
b66862f7 | 59 | return css_to_devcgroup(cgroup_subsys_state(cgroup, devices_subsys_id)); |
08ce5f16 SH |
60 | } |
61 | ||
62 | struct cgroup_subsys devices_subsys; | |
63 | ||
64 | static int devcgroup_can_attach(struct cgroup_subsys *ss, | |
65 | struct cgroup *new_cgroup, struct task_struct *task) | |
66 | { | |
67 | if (current != task && !capable(CAP_SYS_ADMIN)) | |
68 | return -EPERM; | |
69 | ||
70 | return 0; | |
71 | } | |
72 | ||
73 | /* | |
74 | * called under cgroup_lock() | |
75 | */ | |
76 | static int dev_whitelist_copy(struct list_head *dest, struct list_head *orig) | |
77 | { | |
78 | struct dev_whitelist_item *wh, *tmp, *new; | |
79 | ||
80 | list_for_each_entry(wh, orig, list) { | |
81 | new = kmalloc(sizeof(*wh), GFP_KERNEL); | |
82 | if (!new) | |
83 | goto free_and_exit; | |
84 | new->major = wh->major; | |
85 | new->minor = wh->minor; | |
86 | new->type = wh->type; | |
87 | new->access = wh->access; | |
88 | list_add_tail(&new->list, dest); | |
89 | } | |
90 | ||
91 | return 0; | |
92 | ||
93 | free_and_exit: | |
94 | list_for_each_entry_safe(wh, tmp, dest, list) { | |
95 | list_del(&wh->list); | |
96 | kfree(wh); | |
97 | } | |
98 | return -ENOMEM; | |
99 | } | |
100 | ||
101 | /* Stupid prototype - don't bother combining existing entries */ | |
102 | /* | |
103 | * called under cgroup_lock() | |
104 | * since the list is visible to other tasks, we need the spinlock also | |
105 | */ | |
106 | static int dev_whitelist_add(struct dev_cgroup *dev_cgroup, | |
107 | struct dev_whitelist_item *wh) | |
108 | { | |
d1ee2971 | 109 | struct dev_whitelist_item *whcopy, *walk; |
08ce5f16 SH |
110 | |
111 | whcopy = kmalloc(sizeof(*whcopy), GFP_KERNEL); | |
112 | if (!whcopy) | |
113 | return -ENOMEM; | |
114 | ||
115 | memcpy(whcopy, wh, sizeof(*whcopy)); | |
116 | spin_lock(&dev_cgroup->lock); | |
d1ee2971 PE |
117 | list_for_each_entry(walk, &dev_cgroup->whitelist, list) { |
118 | if (walk->type != wh->type) | |
119 | continue; | |
120 | if (walk->major != wh->major) | |
121 | continue; | |
122 | if (walk->minor != wh->minor) | |
123 | continue; | |
124 | ||
125 | walk->access |= wh->access; | |
126 | kfree(whcopy); | |
127 | whcopy = NULL; | |
128 | } | |
129 | ||
130 | if (whcopy != NULL) | |
131 | list_add_tail(&whcopy->list, &dev_cgroup->whitelist); | |
08ce5f16 SH |
132 | spin_unlock(&dev_cgroup->lock); |
133 | return 0; | |
134 | } | |
135 | ||
136 | /* | |
137 | * called under cgroup_lock() | |
138 | * since the list is visible to other tasks, we need the spinlock also | |
139 | */ | |
140 | static 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 | spin_lock(&dev_cgroup->lock); | |
146 | list_for_each_entry_safe(walk, tmp, &dev_cgroup->whitelist, list) { | |
147 | if (walk->type == DEV_ALL) | |
148 | goto remove; | |
149 | if (walk->type != wh->type) | |
150 | continue; | |
151 | if (walk->major != ~0 && walk->major != wh->major) | |
152 | continue; | |
153 | if (walk->minor != ~0 && walk->minor != wh->minor) | |
154 | continue; | |
155 | ||
156 | remove: | |
157 | walk->access &= ~wh->access; | |
158 | if (!walk->access) { | |
159 | list_del(&walk->list); | |
160 | kfree(walk); | |
161 | } | |
162 | } | |
163 | spin_unlock(&dev_cgroup->lock); | |
164 | } | |
165 | ||
166 | /* | |
167 | * called from kernel/cgroup.c with cgroup_lock() held. | |
168 | */ | |
169 | static struct cgroup_subsys_state *devcgroup_create(struct cgroup_subsys *ss, | |
170 | struct cgroup *cgroup) | |
171 | { | |
172 | struct dev_cgroup *dev_cgroup, *parent_dev_cgroup; | |
173 | struct cgroup *parent_cgroup; | |
174 | int ret; | |
175 | ||
176 | dev_cgroup = kzalloc(sizeof(*dev_cgroup), GFP_KERNEL); | |
177 | if (!dev_cgroup) | |
178 | return ERR_PTR(-ENOMEM); | |
179 | INIT_LIST_HEAD(&dev_cgroup->whitelist); | |
180 | parent_cgroup = cgroup->parent; | |
181 | ||
182 | if (parent_cgroup == NULL) { | |
183 | struct dev_whitelist_item *wh; | |
184 | wh = kmalloc(sizeof(*wh), GFP_KERNEL); | |
185 | if (!wh) { | |
186 | kfree(dev_cgroup); | |
187 | return ERR_PTR(-ENOMEM); | |
188 | } | |
189 | wh->minor = wh->major = ~0; | |
190 | wh->type = DEV_ALL; | |
191 | wh->access = ACC_MKNOD | ACC_READ | ACC_WRITE; | |
192 | list_add(&wh->list, &dev_cgroup->whitelist); | |
193 | } else { | |
194 | parent_dev_cgroup = cgroup_to_devcgroup(parent_cgroup); | |
195 | ret = dev_whitelist_copy(&dev_cgroup->whitelist, | |
196 | &parent_dev_cgroup->whitelist); | |
197 | if (ret) { | |
198 | kfree(dev_cgroup); | |
199 | return ERR_PTR(ret); | |
200 | } | |
201 | } | |
202 | ||
203 | spin_lock_init(&dev_cgroup->lock); | |
204 | return &dev_cgroup->css; | |
205 | } | |
206 | ||
207 | static void devcgroup_destroy(struct cgroup_subsys *ss, | |
208 | struct cgroup *cgroup) | |
209 | { | |
210 | struct dev_cgroup *dev_cgroup; | |
211 | struct dev_whitelist_item *wh, *tmp; | |
212 | ||
213 | dev_cgroup = cgroup_to_devcgroup(cgroup); | |
214 | list_for_each_entry_safe(wh, tmp, &dev_cgroup->whitelist, list) { | |
215 | list_del(&wh->list); | |
216 | kfree(wh); | |
217 | } | |
218 | kfree(dev_cgroup); | |
219 | } | |
220 | ||
221 | #define DEVCG_ALLOW 1 | |
222 | #define DEVCG_DENY 2 | |
29486df3 SH |
223 | #define DEVCG_LIST 3 |
224 | ||
225 | #define MAJMINLEN 10 | |
226 | #define ACCLEN 4 | |
08ce5f16 SH |
227 | |
228 | static void set_access(char *acc, short access) | |
229 | { | |
230 | int idx = 0; | |
29486df3 | 231 | memset(acc, 0, ACCLEN); |
08ce5f16 SH |
232 | if (access & ACC_READ) |
233 | acc[idx++] = 'r'; | |
234 | if (access & ACC_WRITE) | |
235 | acc[idx++] = 'w'; | |
236 | if (access & ACC_MKNOD) | |
237 | acc[idx++] = 'm'; | |
238 | } | |
239 | ||
240 | static char type_to_char(short type) | |
241 | { | |
242 | if (type == DEV_ALL) | |
243 | return 'a'; | |
244 | if (type == DEV_CHAR) | |
245 | return 'c'; | |
246 | if (type == DEV_BLOCK) | |
247 | return 'b'; | |
248 | return 'X'; | |
249 | } | |
250 | ||
29486df3 | 251 | static void set_majmin(char *str, unsigned m) |
08ce5f16 | 252 | { |
29486df3 | 253 | memset(str, 0, MAJMINLEN); |
08ce5f16 SH |
254 | if (m == ~0) |
255 | sprintf(str, "*"); | |
256 | else | |
29486df3 | 257 | snprintf(str, MAJMINLEN, "%d", m); |
08ce5f16 SH |
258 | } |
259 | ||
29486df3 SH |
260 | static int devcgroup_seq_read(struct cgroup *cgroup, struct cftype *cft, |
261 | struct seq_file *m) | |
08ce5f16 | 262 | { |
29486df3 | 263 | struct dev_cgroup *devcgroup = cgroup_to_devcgroup(cgroup); |
08ce5f16 | 264 | struct dev_whitelist_item *wh; |
29486df3 | 265 | char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN]; |
08ce5f16 SH |
266 | |
267 | spin_lock(&devcgroup->lock); | |
268 | list_for_each_entry(wh, &devcgroup->whitelist, list) { | |
269 | set_access(acc, wh->access); | |
29486df3 SH |
270 | set_majmin(maj, wh->major); |
271 | set_majmin(min, wh->minor); | |
272 | seq_printf(m, "%c %s:%s %s\n", type_to_char(wh->type), | |
273 | maj, min, acc); | |
08ce5f16 SH |
274 | } |
275 | spin_unlock(&devcgroup->lock); | |
276 | ||
29486df3 | 277 | return 0; |
08ce5f16 SH |
278 | } |
279 | ||
280 | /* | |
281 | * may_access_whitelist: | |
282 | * does the access granted to dev_cgroup c contain the access | |
283 | * requested in whitelist item refwh. | |
284 | * return 1 if yes, 0 if no. | |
285 | * call with c->lock held | |
286 | */ | |
287 | static int may_access_whitelist(struct dev_cgroup *c, | |
288 | struct dev_whitelist_item *refwh) | |
289 | { | |
290 | struct dev_whitelist_item *whitem; | |
291 | ||
292 | list_for_each_entry(whitem, &c->whitelist, list) { | |
293 | if (whitem->type & DEV_ALL) | |
294 | return 1; | |
295 | if ((refwh->type & DEV_BLOCK) && !(whitem->type & DEV_BLOCK)) | |
296 | continue; | |
297 | if ((refwh->type & DEV_CHAR) && !(whitem->type & DEV_CHAR)) | |
298 | continue; | |
299 | if (whitem->major != ~0 && whitem->major != refwh->major) | |
300 | continue; | |
301 | if (whitem->minor != ~0 && whitem->minor != refwh->minor) | |
302 | continue; | |
303 | if (refwh->access & (~(whitem->access | ACC_MASK))) | |
304 | continue; | |
305 | return 1; | |
306 | } | |
307 | return 0; | |
308 | } | |
309 | ||
310 | /* | |
311 | * parent_has_perm: | |
312 | * when adding a new allow rule to a device whitelist, the rule | |
313 | * must be allowed in the parent device | |
314 | */ | |
315 | static int parent_has_perm(struct cgroup *childcg, | |
316 | struct dev_whitelist_item *wh) | |
317 | { | |
318 | struct cgroup *pcg = childcg->parent; | |
319 | struct dev_cgroup *parent; | |
320 | int ret; | |
321 | ||
322 | if (!pcg) | |
323 | return 1; | |
324 | parent = cgroup_to_devcgroup(pcg); | |
325 | spin_lock(&parent->lock); | |
326 | ret = may_access_whitelist(parent, wh); | |
327 | spin_unlock(&parent->lock); | |
328 | return ret; | |
329 | } | |
330 | ||
331 | /* | |
332 | * Modify the whitelist using allow/deny rules. | |
333 | * CAP_SYS_ADMIN is needed for this. It's at least separate from CAP_MKNOD | |
334 | * so we can give a container CAP_MKNOD to let it create devices but not | |
335 | * modify the whitelist. | |
336 | * It seems likely we'll want to add a CAP_CONTAINER capability to allow | |
337 | * us to also grant CAP_SYS_ADMIN to containers without giving away the | |
338 | * device whitelist controls, but for now we'll stick with CAP_SYS_ADMIN | |
339 | * | |
340 | * Taking rules away is always allowed (given CAP_SYS_ADMIN). Granting | |
341 | * new access is only allowed if you're in the top-level cgroup, or your | |
342 | * parent cgroup has the access you're asking for. | |
343 | */ | |
344 | static ssize_t devcgroup_access_write(struct cgroup *cgroup, struct cftype *cft, | |
345 | struct file *file, const char __user *userbuf, | |
346 | size_t nbytes, loff_t *ppos) | |
347 | { | |
348 | struct cgroup *cur_cgroup; | |
349 | struct dev_cgroup *devcgroup, *cur_devcgroup; | |
350 | int filetype = cft->private; | |
351 | char *buffer, *b; | |
352 | int retval = 0, count; | |
353 | struct dev_whitelist_item wh; | |
354 | ||
355 | if (!capable(CAP_SYS_ADMIN)) | |
356 | return -EPERM; | |
357 | ||
358 | devcgroup = cgroup_to_devcgroup(cgroup); | |
359 | cur_cgroup = task_cgroup(current, devices_subsys.subsys_id); | |
360 | cur_devcgroup = cgroup_to_devcgroup(cur_cgroup); | |
361 | ||
362 | buffer = kmalloc(nbytes+1, GFP_KERNEL); | |
363 | if (!buffer) | |
364 | return -ENOMEM; | |
365 | ||
366 | if (copy_from_user(buffer, userbuf, nbytes)) { | |
367 | retval = -EFAULT; | |
368 | goto out1; | |
369 | } | |
370 | buffer[nbytes] = 0; /* nul-terminate */ | |
371 | ||
372 | cgroup_lock(); | |
373 | if (cgroup_is_removed(cgroup)) { | |
374 | retval = -ENODEV; | |
375 | goto out2; | |
376 | } | |
377 | ||
378 | memset(&wh, 0, sizeof(wh)); | |
379 | b = buffer; | |
380 | ||
381 | switch (*b) { | |
382 | case 'a': | |
383 | wh.type = DEV_ALL; | |
384 | wh.access = ACC_MASK; | |
385 | goto handle; | |
386 | case 'b': | |
387 | wh.type = DEV_BLOCK; | |
388 | break; | |
389 | case 'c': | |
390 | wh.type = DEV_CHAR; | |
391 | break; | |
392 | default: | |
393 | retval = -EINVAL; | |
394 | goto out2; | |
395 | } | |
396 | b++; | |
397 | if (!isspace(*b)) { | |
398 | retval = -EINVAL; | |
399 | goto out2; | |
400 | } | |
401 | b++; | |
402 | if (*b == '*') { | |
403 | wh.major = ~0; | |
404 | b++; | |
405 | } else if (isdigit(*b)) { | |
406 | wh.major = 0; | |
407 | while (isdigit(*b)) { | |
408 | wh.major = wh.major*10+(*b-'0'); | |
409 | b++; | |
410 | } | |
411 | } else { | |
412 | retval = -EINVAL; | |
413 | goto out2; | |
414 | } | |
415 | if (*b != ':') { | |
416 | retval = -EINVAL; | |
417 | goto out2; | |
418 | } | |
419 | b++; | |
420 | ||
421 | /* read minor */ | |
422 | if (*b == '*') { | |
423 | wh.minor = ~0; | |
424 | b++; | |
425 | } else if (isdigit(*b)) { | |
426 | wh.minor = 0; | |
427 | while (isdigit(*b)) { | |
428 | wh.minor = wh.minor*10+(*b-'0'); | |
429 | b++; | |
430 | } | |
431 | } else { | |
432 | retval = -EINVAL; | |
433 | goto out2; | |
434 | } | |
435 | if (!isspace(*b)) { | |
436 | retval = -EINVAL; | |
437 | goto out2; | |
438 | } | |
439 | for (b++, count = 0; count < 3; count++, b++) { | |
440 | switch (*b) { | |
441 | case 'r': | |
442 | wh.access |= ACC_READ; | |
443 | break; | |
444 | case 'w': | |
445 | wh.access |= ACC_WRITE; | |
446 | break; | |
447 | case 'm': | |
448 | wh.access |= ACC_MKNOD; | |
449 | break; | |
450 | case '\n': | |
451 | case '\0': | |
452 | count = 3; | |
453 | break; | |
454 | default: | |
455 | retval = -EINVAL; | |
456 | goto out2; | |
457 | } | |
458 | } | |
459 | ||
460 | handle: | |
461 | retval = 0; | |
462 | switch (filetype) { | |
463 | case DEVCG_ALLOW: | |
464 | if (!parent_has_perm(cgroup, &wh)) | |
465 | retval = -EPERM; | |
466 | else | |
467 | retval = dev_whitelist_add(devcgroup, &wh); | |
468 | break; | |
469 | case DEVCG_DENY: | |
470 | dev_whitelist_rm(devcgroup, &wh); | |
471 | break; | |
472 | default: | |
473 | retval = -EINVAL; | |
474 | goto out2; | |
475 | } | |
476 | ||
477 | if (retval == 0) | |
478 | retval = nbytes; | |
479 | ||
480 | out2: | |
481 | cgroup_unlock(); | |
482 | out1: | |
483 | kfree(buffer); | |
484 | return retval; | |
485 | } | |
486 | ||
487 | static struct cftype dev_cgroup_files[] = { | |
488 | { | |
489 | .name = "allow", | |
08ce5f16 SH |
490 | .write = devcgroup_access_write, |
491 | .private = DEVCG_ALLOW, | |
492 | }, | |
493 | { | |
494 | .name = "deny", | |
495 | .write = devcgroup_access_write, | |
496 | .private = DEVCG_DENY, | |
497 | }, | |
29486df3 SH |
498 | { |
499 | .name = "list", | |
500 | .read_seq_string = devcgroup_seq_read, | |
501 | .private = DEVCG_LIST, | |
502 | }, | |
08ce5f16 SH |
503 | }; |
504 | ||
505 | static int devcgroup_populate(struct cgroup_subsys *ss, | |
506 | struct cgroup *cgroup) | |
507 | { | |
508 | return cgroup_add_files(cgroup, ss, dev_cgroup_files, | |
509 | ARRAY_SIZE(dev_cgroup_files)); | |
510 | } | |
511 | ||
512 | struct cgroup_subsys devices_subsys = { | |
513 | .name = "devices", | |
514 | .can_attach = devcgroup_can_attach, | |
515 | .create = devcgroup_create, | |
516 | .destroy = devcgroup_destroy, | |
517 | .populate = devcgroup_populate, | |
518 | .subsys_id = devices_subsys_id, | |
519 | }; | |
520 | ||
521 | int devcgroup_inode_permission(struct inode *inode, int mask) | |
522 | { | |
08ce5f16 SH |
523 | struct dev_cgroup *dev_cgroup; |
524 | struct dev_whitelist_item *wh; | |
525 | ||
526 | dev_t device = inode->i_rdev; | |
527 | if (!device) | |
528 | return 0; | |
529 | if (!S_ISBLK(inode->i_mode) && !S_ISCHR(inode->i_mode)) | |
530 | return 0; | |
cc9cb219 PE |
531 | dev_cgroup = css_to_devcgroup(task_subsys_state(current, |
532 | devices_subsys_id)); | |
08ce5f16 SH |
533 | if (!dev_cgroup) |
534 | return 0; | |
535 | ||
536 | spin_lock(&dev_cgroup->lock); | |
537 | list_for_each_entry(wh, &dev_cgroup->whitelist, list) { | |
538 | if (wh->type & DEV_ALL) | |
539 | goto acc_check; | |
540 | if ((wh->type & DEV_BLOCK) && !S_ISBLK(inode->i_mode)) | |
541 | continue; | |
542 | if ((wh->type & DEV_CHAR) && !S_ISCHR(inode->i_mode)) | |
543 | continue; | |
544 | if (wh->major != ~0 && wh->major != imajor(inode)) | |
545 | continue; | |
546 | if (wh->minor != ~0 && wh->minor != iminor(inode)) | |
547 | continue; | |
548 | acc_check: | |
549 | if ((mask & MAY_WRITE) && !(wh->access & ACC_WRITE)) | |
550 | continue; | |
551 | if ((mask & MAY_READ) && !(wh->access & ACC_READ)) | |
552 | continue; | |
553 | spin_unlock(&dev_cgroup->lock); | |
554 | return 0; | |
555 | } | |
556 | spin_unlock(&dev_cgroup->lock); | |
557 | ||
558 | return -EPERM; | |
559 | } | |
560 | ||
561 | int devcgroup_inode_mknod(int mode, dev_t dev) | |
562 | { | |
08ce5f16 SH |
563 | struct dev_cgroup *dev_cgroup; |
564 | struct dev_whitelist_item *wh; | |
565 | ||
cc9cb219 PE |
566 | dev_cgroup = css_to_devcgroup(task_subsys_state(current, |
567 | devices_subsys_id)); | |
08ce5f16 SH |
568 | if (!dev_cgroup) |
569 | return 0; | |
570 | ||
571 | spin_lock(&dev_cgroup->lock); | |
572 | list_for_each_entry(wh, &dev_cgroup->whitelist, list) { | |
573 | if (wh->type & DEV_ALL) | |
574 | goto acc_check; | |
575 | if ((wh->type & DEV_BLOCK) && !S_ISBLK(mode)) | |
576 | continue; | |
577 | if ((wh->type & DEV_CHAR) && !S_ISCHR(mode)) | |
578 | continue; | |
579 | if (wh->major != ~0 && wh->major != MAJOR(dev)) | |
580 | continue; | |
581 | if (wh->minor != ~0 && wh->minor != MINOR(dev)) | |
582 | continue; | |
583 | acc_check: | |
584 | if (!(wh->access & ACC_MKNOD)) | |
585 | continue; | |
586 | spin_unlock(&dev_cgroup->lock); | |
587 | return 0; | |
588 | } | |
589 | spin_unlock(&dev_cgroup->lock); | |
590 | return -EPERM; | |
591 | } |