Commit | Line | Data |
---|---|---|
08ce5f16 | 1 | /* |
47c59803 | 2 | * device_cgroup.c - device cgroup subsystem |
08ce5f16 SH |
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> |
47c59803 | 13 | #include <linux/rcupdate.h> |
08ce5f16 SH |
14 | |
15 | #define ACC_MKNOD 1 | |
16 | #define ACC_READ 2 | |
17 | #define ACC_WRITE 4 | |
18 | #define ACC_MASK (ACC_MKNOD | ACC_READ | ACC_WRITE) | |
19 | ||
20 | #define DEV_BLOCK 1 | |
21 | #define DEV_CHAR 2 | |
22 | #define DEV_ALL 4 /* this represents all devices */ | |
23 | ||
24 | /* | |
25 | * whitelist locking rules: | |
47c59803 LJ |
26 | * hold cgroup_lock() for update/read. |
27 | * hold rcu_read_lock() for read. | |
08ce5f16 SH |
28 | */ |
29 | ||
30 | struct dev_whitelist_item { | |
31 | u32 major, minor; | |
32 | short type; | |
33 | short access; | |
34 | struct list_head list; | |
4efd1a1b | 35 | struct rcu_head rcu; |
08ce5f16 SH |
36 | }; |
37 | ||
38 | struct dev_cgroup { | |
39 | struct cgroup_subsys_state css; | |
40 | struct list_head whitelist; | |
08ce5f16 SH |
41 | }; |
42 | ||
b66862f7 PE |
43 | static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s) |
44 | { | |
45 | return container_of(s, struct dev_cgroup, css); | |
46 | } | |
47 | ||
08ce5f16 SH |
48 | static inline struct dev_cgroup *cgroup_to_devcgroup(struct cgroup *cgroup) |
49 | { | |
b66862f7 | 50 | return css_to_devcgroup(cgroup_subsys_state(cgroup, devices_subsys_id)); |
08ce5f16 SH |
51 | } |
52 | ||
f92523e3 PM |
53 | static inline struct dev_cgroup *task_devcgroup(struct task_struct *task) |
54 | { | |
55 | return css_to_devcgroup(task_subsys_state(task, devices_subsys_id)); | |
56 | } | |
57 | ||
08ce5f16 SH |
58 | struct cgroup_subsys devices_subsys; |
59 | ||
60 | static int devcgroup_can_attach(struct cgroup_subsys *ss, | |
61 | struct cgroup *new_cgroup, struct task_struct *task) | |
62 | { | |
63 | if (current != task && !capable(CAP_SYS_ADMIN)) | |
64 | return -EPERM; | |
65 | ||
66 | return 0; | |
67 | } | |
68 | ||
69 | /* | |
70 | * called under cgroup_lock() | |
71 | */ | |
72 | static int dev_whitelist_copy(struct list_head *dest, struct list_head *orig) | |
73 | { | |
74 | struct dev_whitelist_item *wh, *tmp, *new; | |
75 | ||
76 | list_for_each_entry(wh, orig, list) { | |
2cdc7241 | 77 | new = kmemdup(wh, sizeof(*wh), GFP_KERNEL); |
08ce5f16 SH |
78 | if (!new) |
79 | goto free_and_exit; | |
08ce5f16 SH |
80 | list_add_tail(&new->list, dest); |
81 | } | |
82 | ||
83 | return 0; | |
84 | ||
85 | free_and_exit: | |
86 | list_for_each_entry_safe(wh, tmp, dest, list) { | |
87 | list_del(&wh->list); | |
88 | kfree(wh); | |
89 | } | |
90 | return -ENOMEM; | |
91 | } | |
92 | ||
93 | /* Stupid prototype - don't bother combining existing entries */ | |
94 | /* | |
95 | * called under cgroup_lock() | |
08ce5f16 SH |
96 | */ |
97 | static int dev_whitelist_add(struct dev_cgroup *dev_cgroup, | |
98 | struct dev_whitelist_item *wh) | |
99 | { | |
d1ee2971 | 100 | struct dev_whitelist_item *whcopy, *walk; |
08ce5f16 | 101 | |
2cdc7241 | 102 | whcopy = kmemdup(wh, sizeof(*wh), GFP_KERNEL); |
08ce5f16 SH |
103 | if (!whcopy) |
104 | return -ENOMEM; | |
105 | ||
d1ee2971 PE |
106 | list_for_each_entry(walk, &dev_cgroup->whitelist, list) { |
107 | if (walk->type != wh->type) | |
108 | continue; | |
109 | if (walk->major != wh->major) | |
110 | continue; | |
111 | if (walk->minor != wh->minor) | |
112 | continue; | |
113 | ||
114 | walk->access |= wh->access; | |
115 | kfree(whcopy); | |
116 | whcopy = NULL; | |
117 | } | |
118 | ||
119 | if (whcopy != NULL) | |
4efd1a1b | 120 | list_add_tail_rcu(&whcopy->list, &dev_cgroup->whitelist); |
08ce5f16 SH |
121 | return 0; |
122 | } | |
123 | ||
4efd1a1b PE |
124 | static void whitelist_item_free(struct rcu_head *rcu) |
125 | { | |
126 | struct dev_whitelist_item *item; | |
127 | ||
128 | item = container_of(rcu, struct dev_whitelist_item, rcu); | |
129 | kfree(item); | |
130 | } | |
131 | ||
08ce5f16 SH |
132 | /* |
133 | * called under cgroup_lock() | |
08ce5f16 SH |
134 | */ |
135 | static void dev_whitelist_rm(struct dev_cgroup *dev_cgroup, | |
136 | struct dev_whitelist_item *wh) | |
137 | { | |
138 | struct dev_whitelist_item *walk, *tmp; | |
139 | ||
08ce5f16 SH |
140 | list_for_each_entry_safe(walk, tmp, &dev_cgroup->whitelist, list) { |
141 | if (walk->type == DEV_ALL) | |
142 | goto remove; | |
143 | if (walk->type != wh->type) | |
144 | continue; | |
145 | if (walk->major != ~0 && walk->major != wh->major) | |
146 | continue; | |
147 | if (walk->minor != ~0 && walk->minor != wh->minor) | |
148 | continue; | |
149 | ||
150 | remove: | |
151 | walk->access &= ~wh->access; | |
152 | if (!walk->access) { | |
4efd1a1b PE |
153 | list_del_rcu(&walk->list); |
154 | call_rcu(&walk->rcu, whitelist_item_free); | |
08ce5f16 SH |
155 | } |
156 | } | |
08ce5f16 SH |
157 | } |
158 | ||
159 | /* | |
160 | * called from kernel/cgroup.c with cgroup_lock() held. | |
161 | */ | |
162 | static struct cgroup_subsys_state *devcgroup_create(struct cgroup_subsys *ss, | |
163 | struct cgroup *cgroup) | |
164 | { | |
165 | struct dev_cgroup *dev_cgroup, *parent_dev_cgroup; | |
166 | struct cgroup *parent_cgroup; | |
167 | int ret; | |
168 | ||
169 | dev_cgroup = kzalloc(sizeof(*dev_cgroup), GFP_KERNEL); | |
170 | if (!dev_cgroup) | |
171 | return ERR_PTR(-ENOMEM); | |
172 | INIT_LIST_HEAD(&dev_cgroup->whitelist); | |
173 | parent_cgroup = cgroup->parent; | |
174 | ||
175 | if (parent_cgroup == NULL) { | |
176 | struct dev_whitelist_item *wh; | |
177 | wh = kmalloc(sizeof(*wh), GFP_KERNEL); | |
178 | if (!wh) { | |
179 | kfree(dev_cgroup); | |
180 | return ERR_PTR(-ENOMEM); | |
181 | } | |
182 | wh->minor = wh->major = ~0; | |
183 | wh->type = DEV_ALL; | |
7759fc9d | 184 | wh->access = ACC_MASK; |
08ce5f16 SH |
185 | list_add(&wh->list, &dev_cgroup->whitelist); |
186 | } else { | |
187 | parent_dev_cgroup = cgroup_to_devcgroup(parent_cgroup); | |
188 | ret = dev_whitelist_copy(&dev_cgroup->whitelist, | |
189 | &parent_dev_cgroup->whitelist); | |
190 | if (ret) { | |
191 | kfree(dev_cgroup); | |
192 | return ERR_PTR(ret); | |
193 | } | |
194 | } | |
195 | ||
08ce5f16 SH |
196 | return &dev_cgroup->css; |
197 | } | |
198 | ||
199 | static void devcgroup_destroy(struct cgroup_subsys *ss, | |
200 | struct cgroup *cgroup) | |
201 | { | |
202 | struct dev_cgroup *dev_cgroup; | |
203 | struct dev_whitelist_item *wh, *tmp; | |
204 | ||
205 | dev_cgroup = cgroup_to_devcgroup(cgroup); | |
206 | list_for_each_entry_safe(wh, tmp, &dev_cgroup->whitelist, list) { | |
207 | list_del(&wh->list); | |
208 | kfree(wh); | |
209 | } | |
210 | kfree(dev_cgroup); | |
211 | } | |
212 | ||
213 | #define DEVCG_ALLOW 1 | |
214 | #define DEVCG_DENY 2 | |
29486df3 SH |
215 | #define DEVCG_LIST 3 |
216 | ||
17d213f8 | 217 | #define MAJMINLEN 13 |
29486df3 | 218 | #define ACCLEN 4 |
08ce5f16 SH |
219 | |
220 | static void set_access(char *acc, short access) | |
221 | { | |
222 | int idx = 0; | |
29486df3 | 223 | memset(acc, 0, ACCLEN); |
08ce5f16 SH |
224 | if (access & ACC_READ) |
225 | acc[idx++] = 'r'; | |
226 | if (access & ACC_WRITE) | |
227 | acc[idx++] = 'w'; | |
228 | if (access & ACC_MKNOD) | |
229 | acc[idx++] = 'm'; | |
230 | } | |
231 | ||
232 | static char type_to_char(short type) | |
233 | { | |
234 | if (type == DEV_ALL) | |
235 | return 'a'; | |
236 | if (type == DEV_CHAR) | |
237 | return 'c'; | |
238 | if (type == DEV_BLOCK) | |
239 | return 'b'; | |
240 | return 'X'; | |
241 | } | |
242 | ||
29486df3 | 243 | static void set_majmin(char *str, unsigned m) |
08ce5f16 | 244 | { |
08ce5f16 | 245 | if (m == ~0) |
7759fc9d | 246 | strcpy(str, "*"); |
08ce5f16 | 247 | else |
7759fc9d | 248 | sprintf(str, "%u", m); |
08ce5f16 SH |
249 | } |
250 | ||
29486df3 SH |
251 | static int devcgroup_seq_read(struct cgroup *cgroup, struct cftype *cft, |
252 | struct seq_file *m) | |
08ce5f16 | 253 | { |
29486df3 | 254 | struct dev_cgroup *devcgroup = cgroup_to_devcgroup(cgroup); |
08ce5f16 | 255 | struct dev_whitelist_item *wh; |
29486df3 | 256 | char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN]; |
08ce5f16 | 257 | |
4efd1a1b PE |
258 | rcu_read_lock(); |
259 | list_for_each_entry_rcu(wh, &devcgroup->whitelist, list) { | |
08ce5f16 | 260 | set_access(acc, wh->access); |
29486df3 SH |
261 | set_majmin(maj, wh->major); |
262 | set_majmin(min, wh->minor); | |
263 | seq_printf(m, "%c %s:%s %s\n", type_to_char(wh->type), | |
264 | maj, min, acc); | |
08ce5f16 | 265 | } |
4efd1a1b | 266 | rcu_read_unlock(); |
08ce5f16 | 267 | |
29486df3 | 268 | return 0; |
08ce5f16 SH |
269 | } |
270 | ||
271 | /* | |
272 | * may_access_whitelist: | |
273 | * does the access granted to dev_cgroup c contain the access | |
274 | * requested in whitelist item refwh. | |
275 | * return 1 if yes, 0 if no. | |
276 | * call with c->lock held | |
277 | */ | |
278 | static int may_access_whitelist(struct dev_cgroup *c, | |
279 | struct dev_whitelist_item *refwh) | |
280 | { | |
281 | struct dev_whitelist_item *whitem; | |
282 | ||
283 | list_for_each_entry(whitem, &c->whitelist, list) { | |
284 | if (whitem->type & DEV_ALL) | |
285 | return 1; | |
286 | if ((refwh->type & DEV_BLOCK) && !(whitem->type & DEV_BLOCK)) | |
287 | continue; | |
288 | if ((refwh->type & DEV_CHAR) && !(whitem->type & DEV_CHAR)) | |
289 | continue; | |
290 | if (whitem->major != ~0 && whitem->major != refwh->major) | |
291 | continue; | |
292 | if (whitem->minor != ~0 && whitem->minor != refwh->minor) | |
293 | continue; | |
ec229e83 | 294 | if (refwh->access & (~whitem->access)) |
08ce5f16 SH |
295 | continue; |
296 | return 1; | |
297 | } | |
298 | return 0; | |
299 | } | |
300 | ||
301 | /* | |
302 | * parent_has_perm: | |
303 | * when adding a new allow rule to a device whitelist, the rule | |
304 | * must be allowed in the parent device | |
305 | */ | |
f92523e3 | 306 | static int parent_has_perm(struct dev_cgroup *childcg, |
08ce5f16 SH |
307 | struct dev_whitelist_item *wh) |
308 | { | |
f92523e3 | 309 | struct cgroup *pcg = childcg->css.cgroup->parent; |
08ce5f16 | 310 | struct dev_cgroup *parent; |
08ce5f16 SH |
311 | |
312 | if (!pcg) | |
313 | return 1; | |
314 | parent = cgroup_to_devcgroup(pcg); | |
47c59803 | 315 | return may_access_whitelist(parent, wh); |
08ce5f16 SH |
316 | } |
317 | ||
318 | /* | |
319 | * Modify the whitelist using allow/deny rules. | |
320 | * CAP_SYS_ADMIN is needed for this. It's at least separate from CAP_MKNOD | |
321 | * so we can give a container CAP_MKNOD to let it create devices but not | |
322 | * modify the whitelist. | |
323 | * It seems likely we'll want to add a CAP_CONTAINER capability to allow | |
324 | * us to also grant CAP_SYS_ADMIN to containers without giving away the | |
325 | * device whitelist controls, but for now we'll stick with CAP_SYS_ADMIN | |
326 | * | |
327 | * Taking rules away is always allowed (given CAP_SYS_ADMIN). Granting | |
328 | * new access is only allowed if you're in the top-level cgroup, or your | |
329 | * parent cgroup has the access you're asking for. | |
330 | */ | |
f92523e3 PM |
331 | static int devcgroup_update_access(struct dev_cgroup *devcgroup, |
332 | int filetype, const char *buffer) | |
08ce5f16 | 333 | { |
f92523e3 | 334 | const char *b; |
7759fc9d | 335 | char *endp; |
c012a54a | 336 | int count; |
08ce5f16 SH |
337 | struct dev_whitelist_item wh; |
338 | ||
339 | if (!capable(CAP_SYS_ADMIN)) | |
340 | return -EPERM; | |
341 | ||
08ce5f16 SH |
342 | memset(&wh, 0, sizeof(wh)); |
343 | b = buffer; | |
344 | ||
345 | switch (*b) { | |
346 | case 'a': | |
347 | wh.type = DEV_ALL; | |
348 | wh.access = ACC_MASK; | |
d823f6bf LZ |
349 | wh.major = ~0; |
350 | wh.minor = ~0; | |
08ce5f16 SH |
351 | goto handle; |
352 | case 'b': | |
353 | wh.type = DEV_BLOCK; | |
354 | break; | |
355 | case 'c': | |
356 | wh.type = DEV_CHAR; | |
357 | break; | |
358 | default: | |
f92523e3 | 359 | return -EINVAL; |
08ce5f16 SH |
360 | } |
361 | b++; | |
f92523e3 PM |
362 | if (!isspace(*b)) |
363 | return -EINVAL; | |
08ce5f16 SH |
364 | b++; |
365 | if (*b == '*') { | |
366 | wh.major = ~0; | |
367 | b++; | |
368 | } else if (isdigit(*b)) { | |
7759fc9d LZ |
369 | wh.major = simple_strtoul(b, &endp, 10); |
370 | b = endp; | |
08ce5f16 | 371 | } else { |
f92523e3 | 372 | return -EINVAL; |
08ce5f16 | 373 | } |
f92523e3 PM |
374 | if (*b != ':') |
375 | return -EINVAL; | |
08ce5f16 SH |
376 | b++; |
377 | ||
378 | /* read minor */ | |
379 | if (*b == '*') { | |
380 | wh.minor = ~0; | |
381 | b++; | |
382 | } else if (isdigit(*b)) { | |
7759fc9d LZ |
383 | wh.minor = simple_strtoul(b, &endp, 10); |
384 | b = endp; | |
08ce5f16 | 385 | } else { |
f92523e3 | 386 | return -EINVAL; |
08ce5f16 | 387 | } |
f92523e3 PM |
388 | if (!isspace(*b)) |
389 | return -EINVAL; | |
08ce5f16 SH |
390 | for (b++, count = 0; count < 3; count++, b++) { |
391 | switch (*b) { | |
392 | case 'r': | |
393 | wh.access |= ACC_READ; | |
394 | break; | |
395 | case 'w': | |
396 | wh.access |= ACC_WRITE; | |
397 | break; | |
398 | case 'm': | |
399 | wh.access |= ACC_MKNOD; | |
400 | break; | |
401 | case '\n': | |
402 | case '\0': | |
403 | count = 3; | |
404 | break; | |
405 | default: | |
f92523e3 | 406 | return -EINVAL; |
08ce5f16 SH |
407 | } |
408 | } | |
409 | ||
410 | handle: | |
08ce5f16 SH |
411 | switch (filetype) { |
412 | case DEVCG_ALLOW: | |
f92523e3 PM |
413 | if (!parent_has_perm(devcgroup, &wh)) |
414 | return -EPERM; | |
415 | return dev_whitelist_add(devcgroup, &wh); | |
08ce5f16 SH |
416 | case DEVCG_DENY: |
417 | dev_whitelist_rm(devcgroup, &wh); | |
418 | break; | |
419 | default: | |
f92523e3 | 420 | return -EINVAL; |
08ce5f16 | 421 | } |
f92523e3 PM |
422 | return 0; |
423 | } | |
08ce5f16 | 424 | |
f92523e3 PM |
425 | static int devcgroup_access_write(struct cgroup *cgrp, struct cftype *cft, |
426 | const char *buffer) | |
427 | { | |
428 | int retval; | |
429 | if (!cgroup_lock_live_group(cgrp)) | |
430 | return -ENODEV; | |
431 | retval = devcgroup_update_access(cgroup_to_devcgroup(cgrp), | |
432 | cft->private, buffer); | |
08ce5f16 | 433 | cgroup_unlock(); |
08ce5f16 SH |
434 | return retval; |
435 | } | |
436 | ||
437 | static struct cftype dev_cgroup_files[] = { | |
438 | { | |
439 | .name = "allow", | |
f92523e3 | 440 | .write_string = devcgroup_access_write, |
08ce5f16 SH |
441 | .private = DEVCG_ALLOW, |
442 | }, | |
443 | { | |
444 | .name = "deny", | |
f92523e3 | 445 | .write_string = devcgroup_access_write, |
08ce5f16 SH |
446 | .private = DEVCG_DENY, |
447 | }, | |
29486df3 SH |
448 | { |
449 | .name = "list", | |
450 | .read_seq_string = devcgroup_seq_read, | |
451 | .private = DEVCG_LIST, | |
452 | }, | |
08ce5f16 SH |
453 | }; |
454 | ||
455 | static int devcgroup_populate(struct cgroup_subsys *ss, | |
456 | struct cgroup *cgroup) | |
457 | { | |
458 | return cgroup_add_files(cgroup, ss, dev_cgroup_files, | |
459 | ARRAY_SIZE(dev_cgroup_files)); | |
460 | } | |
461 | ||
462 | struct cgroup_subsys devices_subsys = { | |
463 | .name = "devices", | |
464 | .can_attach = devcgroup_can_attach, | |
465 | .create = devcgroup_create, | |
466 | .destroy = devcgroup_destroy, | |
467 | .populate = devcgroup_populate, | |
468 | .subsys_id = devices_subsys_id, | |
469 | }; | |
470 | ||
471 | int devcgroup_inode_permission(struct inode *inode, int mask) | |
472 | { | |
08ce5f16 SH |
473 | struct dev_cgroup *dev_cgroup; |
474 | struct dev_whitelist_item *wh; | |
475 | ||
476 | dev_t device = inode->i_rdev; | |
477 | if (!device) | |
478 | return 0; | |
479 | if (!S_ISBLK(inode->i_mode) && !S_ISCHR(inode->i_mode)) | |
480 | return 0; | |
08ce5f16 | 481 | |
4efd1a1b | 482 | rcu_read_lock(); |
36fd71d2 LZ |
483 | |
484 | dev_cgroup = task_devcgroup(current); | |
485 | ||
4efd1a1b | 486 | list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) { |
08ce5f16 SH |
487 | if (wh->type & DEV_ALL) |
488 | goto acc_check; | |
489 | if ((wh->type & DEV_BLOCK) && !S_ISBLK(inode->i_mode)) | |
490 | continue; | |
491 | if ((wh->type & DEV_CHAR) && !S_ISCHR(inode->i_mode)) | |
492 | continue; | |
493 | if (wh->major != ~0 && wh->major != imajor(inode)) | |
494 | continue; | |
495 | if (wh->minor != ~0 && wh->minor != iminor(inode)) | |
496 | continue; | |
497 | acc_check: | |
498 | if ((mask & MAY_WRITE) && !(wh->access & ACC_WRITE)) | |
499 | continue; | |
500 | if ((mask & MAY_READ) && !(wh->access & ACC_READ)) | |
501 | continue; | |
4efd1a1b | 502 | rcu_read_unlock(); |
08ce5f16 SH |
503 | return 0; |
504 | } | |
36fd71d2 | 505 | |
4efd1a1b | 506 | rcu_read_unlock(); |
08ce5f16 SH |
507 | |
508 | return -EPERM; | |
509 | } | |
510 | ||
511 | int devcgroup_inode_mknod(int mode, dev_t dev) | |
512 | { | |
08ce5f16 SH |
513 | struct dev_cgroup *dev_cgroup; |
514 | struct dev_whitelist_item *wh; | |
515 | ||
0b82ac37 SH |
516 | if (!S_ISBLK(mode) && !S_ISCHR(mode)) |
517 | return 0; | |
518 | ||
4efd1a1b | 519 | rcu_read_lock(); |
36fd71d2 LZ |
520 | |
521 | dev_cgroup = task_devcgroup(current); | |
522 | ||
116e0575 | 523 | list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) { |
08ce5f16 SH |
524 | if (wh->type & DEV_ALL) |
525 | goto acc_check; | |
526 | if ((wh->type & DEV_BLOCK) && !S_ISBLK(mode)) | |
527 | continue; | |
528 | if ((wh->type & DEV_CHAR) && !S_ISCHR(mode)) | |
529 | continue; | |
530 | if (wh->major != ~0 && wh->major != MAJOR(dev)) | |
531 | continue; | |
532 | if (wh->minor != ~0 && wh->minor != MINOR(dev)) | |
533 | continue; | |
534 | acc_check: | |
535 | if (!(wh->access & ACC_MKNOD)) | |
536 | continue; | |
4efd1a1b | 537 | rcu_read_unlock(); |
08ce5f16 SH |
538 | return 0; |
539 | } | |
36fd71d2 | 540 | |
4efd1a1b | 541 | rcu_read_unlock(); |
36fd71d2 | 542 | |
08ce5f16 SH |
543 | return -EPERM; |
544 | } |