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> |
5a0e3ad6 | 13 | #include <linux/slab.h> |
47c59803 | 14 | #include <linux/rcupdate.h> |
b4046f00 | 15 | #include <linux/mutex.h> |
08ce5f16 SH |
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 /* this represents all devices */ | |
25 | ||
b4046f00 LZ |
26 | static DEFINE_MUTEX(devcgroup_mutex); |
27 | ||
08ce5f16 SH |
28 | /* |
29 | * whitelist locking rules: | |
b4046f00 | 30 | * hold devcgroup_mutex for update/read. |
47c59803 | 31 | * hold rcu_read_lock() for read. |
08ce5f16 SH |
32 | */ |
33 | ||
34 | struct dev_whitelist_item { | |
35 | u32 major, minor; | |
36 | short type; | |
37 | short access; | |
38 | struct list_head list; | |
4efd1a1b | 39 | struct rcu_head rcu; |
08ce5f16 SH |
40 | }; |
41 | ||
42 | struct dev_cgroup { | |
43 | struct cgroup_subsys_state css; | |
44 | struct list_head whitelist; | |
08ce5f16 SH |
45 | }; |
46 | ||
b66862f7 PE |
47 | static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s) |
48 | { | |
49 | return container_of(s, struct dev_cgroup, css); | |
50 | } | |
51 | ||
08ce5f16 SH |
52 | static inline struct dev_cgroup *cgroup_to_devcgroup(struct cgroup *cgroup) |
53 | { | |
b66862f7 | 54 | return css_to_devcgroup(cgroup_subsys_state(cgroup, devices_subsys_id)); |
08ce5f16 SH |
55 | } |
56 | ||
f92523e3 PM |
57 | static 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 | ||
08ce5f16 SH |
62 | struct cgroup_subsys devices_subsys; |
63 | ||
761b3ef5 LZ |
64 | static int devcgroup_can_attach(struct cgroup *new_cgrp, |
65 | struct cgroup_taskset *set) | |
08ce5f16 | 66 | { |
2f7ee569 | 67 | struct task_struct *task = cgroup_taskset_first(set); |
08ce5f16 | 68 | |
2f7ee569 TH |
69 | if (current != task && !capable(CAP_SYS_ADMIN)) |
70 | return -EPERM; | |
08ce5f16 SH |
71 | return 0; |
72 | } | |
73 | ||
74 | /* | |
b4046f00 | 75 | * called under devcgroup_mutex |
08ce5f16 SH |
76 | */ |
77 | static 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) { | |
2cdc7241 | 82 | new = kmemdup(wh, sizeof(*wh), GFP_KERNEL); |
08ce5f16 SH |
83 | if (!new) |
84 | goto free_and_exit; | |
08ce5f16 SH |
85 | list_add_tail(&new->list, dest); |
86 | } | |
87 | ||
88 | return 0; | |
89 | ||
90 | free_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 | /* Stupid prototype - don't bother combining existing entries */ | |
99 | /* | |
b4046f00 | 100 | * called under devcgroup_mutex |
08ce5f16 SH |
101 | */ |
102 | static int dev_whitelist_add(struct dev_cgroup *dev_cgroup, | |
103 | struct dev_whitelist_item *wh) | |
104 | { | |
d1ee2971 | 105 | struct dev_whitelist_item *whcopy, *walk; |
08ce5f16 | 106 | |
2cdc7241 | 107 | whcopy = kmemdup(wh, sizeof(*wh), GFP_KERNEL); |
08ce5f16 SH |
108 | if (!whcopy) |
109 | return -ENOMEM; | |
110 | ||
d1ee2971 PE |
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) | |
4efd1a1b | 125 | list_add_tail_rcu(&whcopy->list, &dev_cgroup->whitelist); |
08ce5f16 SH |
126 | return 0; |
127 | } | |
128 | ||
129 | /* | |
b4046f00 | 130 | * called under devcgroup_mutex |
08ce5f16 SH |
131 | */ |
132 | static void dev_whitelist_rm(struct dev_cgroup *dev_cgroup, | |
133 | struct dev_whitelist_item *wh) | |
134 | { | |
135 | struct dev_whitelist_item *walk, *tmp; | |
136 | ||
08ce5f16 SH |
137 | list_for_each_entry_safe(walk, tmp, &dev_cgroup->whitelist, list) { |
138 | if (walk->type == DEV_ALL) | |
139 | goto remove; | |
140 | if (walk->type != wh->type) | |
141 | continue; | |
142 | if (walk->major != ~0 && walk->major != wh->major) | |
143 | continue; | |
144 | if (walk->minor != ~0 && walk->minor != wh->minor) | |
145 | continue; | |
146 | ||
147 | remove: | |
148 | walk->access &= ~wh->access; | |
149 | if (!walk->access) { | |
4efd1a1b | 150 | list_del_rcu(&walk->list); |
6034f7e6 | 151 | kfree_rcu(walk, rcu); |
08ce5f16 SH |
152 | } |
153 | } | |
08ce5f16 SH |
154 | } |
155 | ||
156 | /* | |
157 | * called from kernel/cgroup.c with cgroup_lock() held. | |
158 | */ | |
761b3ef5 | 159 | static struct cgroup_subsys_state *devcgroup_create(struct cgroup *cgroup) |
08ce5f16 SH |
160 | { |
161 | struct dev_cgroup *dev_cgroup, *parent_dev_cgroup; | |
162 | struct cgroup *parent_cgroup; | |
163 | int ret; | |
164 | ||
165 | dev_cgroup = kzalloc(sizeof(*dev_cgroup), GFP_KERNEL); | |
166 | if (!dev_cgroup) | |
167 | return ERR_PTR(-ENOMEM); | |
168 | INIT_LIST_HEAD(&dev_cgroup->whitelist); | |
169 | parent_cgroup = cgroup->parent; | |
170 | ||
171 | if (parent_cgroup == NULL) { | |
172 | struct dev_whitelist_item *wh; | |
173 | wh = kmalloc(sizeof(*wh), GFP_KERNEL); | |
174 | if (!wh) { | |
175 | kfree(dev_cgroup); | |
176 | return ERR_PTR(-ENOMEM); | |
177 | } | |
178 | wh->minor = wh->major = ~0; | |
179 | wh->type = DEV_ALL; | |
7759fc9d | 180 | wh->access = ACC_MASK; |
08ce5f16 SH |
181 | list_add(&wh->list, &dev_cgroup->whitelist); |
182 | } else { | |
183 | parent_dev_cgroup = cgroup_to_devcgroup(parent_cgroup); | |
b4046f00 | 184 | mutex_lock(&devcgroup_mutex); |
08ce5f16 SH |
185 | ret = dev_whitelist_copy(&dev_cgroup->whitelist, |
186 | &parent_dev_cgroup->whitelist); | |
b4046f00 | 187 | mutex_unlock(&devcgroup_mutex); |
08ce5f16 SH |
188 | if (ret) { |
189 | kfree(dev_cgroup); | |
190 | return ERR_PTR(ret); | |
191 | } | |
192 | } | |
193 | ||
08ce5f16 SH |
194 | return &dev_cgroup->css; |
195 | } | |
196 | ||
761b3ef5 | 197 | static void devcgroup_destroy(struct cgroup *cgroup) |
08ce5f16 SH |
198 | { |
199 | struct dev_cgroup *dev_cgroup; | |
200 | struct dev_whitelist_item *wh, *tmp; | |
201 | ||
202 | dev_cgroup = cgroup_to_devcgroup(cgroup); | |
203 | list_for_each_entry_safe(wh, tmp, &dev_cgroup->whitelist, list) { | |
204 | list_del(&wh->list); | |
205 | kfree(wh); | |
206 | } | |
207 | kfree(dev_cgroup); | |
208 | } | |
209 | ||
210 | #define DEVCG_ALLOW 1 | |
211 | #define DEVCG_DENY 2 | |
29486df3 SH |
212 | #define DEVCG_LIST 3 |
213 | ||
17d213f8 | 214 | #define MAJMINLEN 13 |
29486df3 | 215 | #define ACCLEN 4 |
08ce5f16 SH |
216 | |
217 | static void set_access(char *acc, short access) | |
218 | { | |
219 | int idx = 0; | |
29486df3 | 220 | memset(acc, 0, ACCLEN); |
08ce5f16 SH |
221 | if (access & ACC_READ) |
222 | acc[idx++] = 'r'; | |
223 | if (access & ACC_WRITE) | |
224 | acc[idx++] = 'w'; | |
225 | if (access & ACC_MKNOD) | |
226 | acc[idx++] = 'm'; | |
227 | } | |
228 | ||
229 | static char type_to_char(short type) | |
230 | { | |
231 | if (type == DEV_ALL) | |
232 | return 'a'; | |
233 | if (type == DEV_CHAR) | |
234 | return 'c'; | |
235 | if (type == DEV_BLOCK) | |
236 | return 'b'; | |
237 | return 'X'; | |
238 | } | |
239 | ||
29486df3 | 240 | static void set_majmin(char *str, unsigned m) |
08ce5f16 | 241 | { |
08ce5f16 | 242 | if (m == ~0) |
7759fc9d | 243 | strcpy(str, "*"); |
08ce5f16 | 244 | else |
7759fc9d | 245 | sprintf(str, "%u", m); |
08ce5f16 SH |
246 | } |
247 | ||
29486df3 SH |
248 | static int devcgroup_seq_read(struct cgroup *cgroup, struct cftype *cft, |
249 | struct seq_file *m) | |
08ce5f16 | 250 | { |
29486df3 | 251 | struct dev_cgroup *devcgroup = cgroup_to_devcgroup(cgroup); |
08ce5f16 | 252 | struct dev_whitelist_item *wh; |
29486df3 | 253 | char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN]; |
08ce5f16 | 254 | |
4efd1a1b PE |
255 | rcu_read_lock(); |
256 | list_for_each_entry_rcu(wh, &devcgroup->whitelist, list) { | |
08ce5f16 | 257 | set_access(acc, wh->access); |
29486df3 SH |
258 | set_majmin(maj, wh->major); |
259 | set_majmin(min, wh->minor); | |
260 | seq_printf(m, "%c %s:%s %s\n", type_to_char(wh->type), | |
261 | maj, min, acc); | |
08ce5f16 | 262 | } |
4efd1a1b | 263 | rcu_read_unlock(); |
08ce5f16 | 264 | |
29486df3 | 265 | return 0; |
08ce5f16 SH |
266 | } |
267 | ||
268 | /* | |
269 | * may_access_whitelist: | |
270 | * does the access granted to dev_cgroup c contain the access | |
271 | * requested in whitelist item refwh. | |
272 | * return 1 if yes, 0 if no. | |
b4046f00 | 273 | * call with devcgroup_mutex held |
08ce5f16 SH |
274 | */ |
275 | static int may_access_whitelist(struct dev_cgroup *c, | |
276 | struct dev_whitelist_item *refwh) | |
277 | { | |
278 | struct dev_whitelist_item *whitem; | |
279 | ||
280 | list_for_each_entry(whitem, &c->whitelist, list) { | |
281 | if (whitem->type & DEV_ALL) | |
282 | return 1; | |
283 | if ((refwh->type & DEV_BLOCK) && !(whitem->type & DEV_BLOCK)) | |
284 | continue; | |
285 | if ((refwh->type & DEV_CHAR) && !(whitem->type & DEV_CHAR)) | |
286 | continue; | |
287 | if (whitem->major != ~0 && whitem->major != refwh->major) | |
288 | continue; | |
289 | if (whitem->minor != ~0 && whitem->minor != refwh->minor) | |
290 | continue; | |
ec229e83 | 291 | if (refwh->access & (~whitem->access)) |
08ce5f16 SH |
292 | continue; |
293 | return 1; | |
294 | } | |
295 | return 0; | |
296 | } | |
297 | ||
298 | /* | |
299 | * parent_has_perm: | |
300 | * when adding a new allow rule to a device whitelist, the rule | |
301 | * must be allowed in the parent device | |
302 | */ | |
f92523e3 | 303 | static int parent_has_perm(struct dev_cgroup *childcg, |
08ce5f16 SH |
304 | struct dev_whitelist_item *wh) |
305 | { | |
f92523e3 | 306 | struct cgroup *pcg = childcg->css.cgroup->parent; |
08ce5f16 | 307 | struct dev_cgroup *parent; |
08ce5f16 SH |
308 | |
309 | if (!pcg) | |
310 | return 1; | |
311 | parent = cgroup_to_devcgroup(pcg); | |
47c59803 | 312 | return may_access_whitelist(parent, wh); |
08ce5f16 SH |
313 | } |
314 | ||
315 | /* | |
316 | * Modify the whitelist using allow/deny rules. | |
317 | * CAP_SYS_ADMIN is needed for this. It's at least separate from CAP_MKNOD | |
318 | * so we can give a container CAP_MKNOD to let it create devices but not | |
319 | * modify the whitelist. | |
320 | * It seems likely we'll want to add a CAP_CONTAINER capability to allow | |
321 | * us to also grant CAP_SYS_ADMIN to containers without giving away the | |
322 | * device whitelist controls, but for now we'll stick with CAP_SYS_ADMIN | |
323 | * | |
324 | * Taking rules away is always allowed (given CAP_SYS_ADMIN). Granting | |
325 | * new access is only allowed if you're in the top-level cgroup, or your | |
326 | * parent cgroup has the access you're asking for. | |
327 | */ | |
f92523e3 PM |
328 | static int devcgroup_update_access(struct dev_cgroup *devcgroup, |
329 | int filetype, const char *buffer) | |
08ce5f16 | 330 | { |
f92523e3 | 331 | const char *b; |
7759fc9d | 332 | char *endp; |
c012a54a | 333 | int count; |
08ce5f16 SH |
334 | struct dev_whitelist_item wh; |
335 | ||
336 | if (!capable(CAP_SYS_ADMIN)) | |
337 | return -EPERM; | |
338 | ||
08ce5f16 SH |
339 | memset(&wh, 0, sizeof(wh)); |
340 | b = buffer; | |
341 | ||
342 | switch (*b) { | |
343 | case 'a': | |
344 | wh.type = DEV_ALL; | |
345 | wh.access = ACC_MASK; | |
d823f6bf LZ |
346 | wh.major = ~0; |
347 | wh.minor = ~0; | |
08ce5f16 SH |
348 | goto handle; |
349 | case 'b': | |
350 | wh.type = DEV_BLOCK; | |
351 | break; | |
352 | case 'c': | |
353 | wh.type = DEV_CHAR; | |
354 | break; | |
355 | default: | |
f92523e3 | 356 | return -EINVAL; |
08ce5f16 SH |
357 | } |
358 | b++; | |
f92523e3 PM |
359 | if (!isspace(*b)) |
360 | return -EINVAL; | |
08ce5f16 SH |
361 | b++; |
362 | if (*b == '*') { | |
363 | wh.major = ~0; | |
364 | b++; | |
365 | } else if (isdigit(*b)) { | |
7759fc9d LZ |
366 | wh.major = simple_strtoul(b, &endp, 10); |
367 | b = endp; | |
08ce5f16 | 368 | } else { |
f92523e3 | 369 | return -EINVAL; |
08ce5f16 | 370 | } |
f92523e3 PM |
371 | if (*b != ':') |
372 | return -EINVAL; | |
08ce5f16 SH |
373 | b++; |
374 | ||
375 | /* read minor */ | |
376 | if (*b == '*') { | |
377 | wh.minor = ~0; | |
378 | b++; | |
379 | } else if (isdigit(*b)) { | |
7759fc9d LZ |
380 | wh.minor = simple_strtoul(b, &endp, 10); |
381 | b = endp; | |
08ce5f16 | 382 | } else { |
f92523e3 | 383 | return -EINVAL; |
08ce5f16 | 384 | } |
f92523e3 PM |
385 | if (!isspace(*b)) |
386 | return -EINVAL; | |
08ce5f16 SH |
387 | for (b++, count = 0; count < 3; count++, b++) { |
388 | switch (*b) { | |
389 | case 'r': | |
390 | wh.access |= ACC_READ; | |
391 | break; | |
392 | case 'w': | |
393 | wh.access |= ACC_WRITE; | |
394 | break; | |
395 | case 'm': | |
396 | wh.access |= ACC_MKNOD; | |
397 | break; | |
398 | case '\n': | |
399 | case '\0': | |
400 | count = 3; | |
401 | break; | |
402 | default: | |
f92523e3 | 403 | return -EINVAL; |
08ce5f16 SH |
404 | } |
405 | } | |
406 | ||
407 | handle: | |
08ce5f16 SH |
408 | switch (filetype) { |
409 | case DEVCG_ALLOW: | |
f92523e3 PM |
410 | if (!parent_has_perm(devcgroup, &wh)) |
411 | return -EPERM; | |
412 | return dev_whitelist_add(devcgroup, &wh); | |
08ce5f16 SH |
413 | case DEVCG_DENY: |
414 | dev_whitelist_rm(devcgroup, &wh); | |
415 | break; | |
416 | default: | |
f92523e3 | 417 | return -EINVAL; |
08ce5f16 | 418 | } |
f92523e3 PM |
419 | return 0; |
420 | } | |
08ce5f16 | 421 | |
f92523e3 PM |
422 | static int devcgroup_access_write(struct cgroup *cgrp, struct cftype *cft, |
423 | const char *buffer) | |
424 | { | |
425 | int retval; | |
b4046f00 LZ |
426 | |
427 | mutex_lock(&devcgroup_mutex); | |
f92523e3 PM |
428 | retval = devcgroup_update_access(cgroup_to_devcgroup(cgrp), |
429 | cft->private, buffer); | |
b4046f00 | 430 | mutex_unlock(&devcgroup_mutex); |
08ce5f16 SH |
431 | return retval; |
432 | } | |
433 | ||
434 | static struct cftype dev_cgroup_files[] = { | |
435 | { | |
436 | .name = "allow", | |
f92523e3 | 437 | .write_string = devcgroup_access_write, |
08ce5f16 SH |
438 | .private = DEVCG_ALLOW, |
439 | }, | |
440 | { | |
441 | .name = "deny", | |
f92523e3 | 442 | .write_string = devcgroup_access_write, |
08ce5f16 SH |
443 | .private = DEVCG_DENY, |
444 | }, | |
29486df3 SH |
445 | { |
446 | .name = "list", | |
447 | .read_seq_string = devcgroup_seq_read, | |
448 | .private = DEVCG_LIST, | |
449 | }, | |
4baf6e33 | 450 | { } /* terminate */ |
08ce5f16 SH |
451 | }; |
452 | ||
08ce5f16 SH |
453 | struct cgroup_subsys devices_subsys = { |
454 | .name = "devices", | |
455 | .can_attach = devcgroup_can_attach, | |
456 | .create = devcgroup_create, | |
c5b60b5e | 457 | .destroy = devcgroup_destroy, |
08ce5f16 | 458 | .subsys_id = devices_subsys_id, |
4baf6e33 | 459 | .base_cftypes = dev_cgroup_files, |
08ce5f16 SH |
460 | }; |
461 | ||
482e0cd3 | 462 | int __devcgroup_inode_permission(struct inode *inode, int mask) |
08ce5f16 | 463 | { |
08ce5f16 SH |
464 | struct dev_cgroup *dev_cgroup; |
465 | struct dev_whitelist_item *wh; | |
466 | ||
4efd1a1b | 467 | rcu_read_lock(); |
36fd71d2 LZ |
468 | |
469 | dev_cgroup = task_devcgroup(current); | |
470 | ||
4efd1a1b | 471 | list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) { |
08ce5f16 | 472 | if (wh->type & DEV_ALL) |
cd500819 | 473 | goto found; |
08ce5f16 SH |
474 | if ((wh->type & DEV_BLOCK) && !S_ISBLK(inode->i_mode)) |
475 | continue; | |
476 | if ((wh->type & DEV_CHAR) && !S_ISCHR(inode->i_mode)) | |
477 | continue; | |
478 | if (wh->major != ~0 && wh->major != imajor(inode)) | |
479 | continue; | |
480 | if (wh->minor != ~0 && wh->minor != iminor(inode)) | |
481 | continue; | |
cd500819 | 482 | |
08ce5f16 SH |
483 | if ((mask & MAY_WRITE) && !(wh->access & ACC_WRITE)) |
484 | continue; | |
485 | if ((mask & MAY_READ) && !(wh->access & ACC_READ)) | |
486 | continue; | |
cd500819 | 487 | found: |
4efd1a1b | 488 | rcu_read_unlock(); |
08ce5f16 SH |
489 | return 0; |
490 | } | |
36fd71d2 | 491 | |
4efd1a1b | 492 | rcu_read_unlock(); |
08ce5f16 SH |
493 | |
494 | return -EPERM; | |
495 | } | |
496 | ||
497 | int devcgroup_inode_mknod(int mode, dev_t dev) | |
498 | { | |
08ce5f16 SH |
499 | struct dev_cgroup *dev_cgroup; |
500 | struct dev_whitelist_item *wh; | |
501 | ||
0b82ac37 SH |
502 | if (!S_ISBLK(mode) && !S_ISCHR(mode)) |
503 | return 0; | |
504 | ||
4efd1a1b | 505 | rcu_read_lock(); |
36fd71d2 LZ |
506 | |
507 | dev_cgroup = task_devcgroup(current); | |
508 | ||
116e0575 | 509 | list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) { |
08ce5f16 | 510 | if (wh->type & DEV_ALL) |
cd500819 | 511 | goto found; |
08ce5f16 SH |
512 | if ((wh->type & DEV_BLOCK) && !S_ISBLK(mode)) |
513 | continue; | |
514 | if ((wh->type & DEV_CHAR) && !S_ISCHR(mode)) | |
515 | continue; | |
516 | if (wh->major != ~0 && wh->major != MAJOR(dev)) | |
517 | continue; | |
518 | if (wh->minor != ~0 && wh->minor != MINOR(dev)) | |
519 | continue; | |
cd500819 | 520 | |
08ce5f16 SH |
521 | if (!(wh->access & ACC_MKNOD)) |
522 | continue; | |
cd500819 | 523 | found: |
4efd1a1b | 524 | rcu_read_unlock(); |
08ce5f16 SH |
525 | return 0; |
526 | } | |
36fd71d2 | 527 | |
4efd1a1b | 528 | rcu_read_unlock(); |
36fd71d2 | 529 | |
08ce5f16 SH |
530 | return -EPERM; |
531 | } |