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Source at commit b13e7eb172b6f08e5fc22da162bdde5fcde201b5 created 11 years 11 months ago. By Maarten ter Huurne, fbcon: Add 6x10 font | |
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1 | /* |
2 | * device_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> |
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 /* this represents all devices */ |
25 | |
26 | static DEFINE_MUTEX(devcgroup_mutex); |
27 | |
28 | /* |
29 | * whitelist locking rules: |
30 | * hold devcgroup_mutex for update/read. |
31 | * hold rcu_read_lock() for read. |
32 | */ |
33 | |
34 | struct 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 | |
42 | struct dev_cgroup { |
43 | struct cgroup_subsys_state css; |
44 | struct list_head whitelist; |
45 | }; |
46 | |
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 | |
52 | static 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 | |
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 | |
62 | struct cgroup_subsys devices_subsys; |
63 | |
64 | static int devcgroup_can_attach(struct cgroup_subsys *ss, |
65 | struct cgroup *new_cgrp, struct cgroup_taskset *set) |
66 | { |
67 | struct task_struct *task = cgroup_taskset_first(set); |
68 | |
69 | if (current != task && !capable(CAP_SYS_ADMIN)) |
70 | return -EPERM; |
71 | return 0; |
72 | } |
73 | |
74 | /* |
75 | * called under devcgroup_mutex |
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) { |
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 | |
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 | /* |
100 | * called under devcgroup_mutex |
101 | */ |
102 | static 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 | |
129 | /* |
130 | * called under devcgroup_mutex |
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 | |
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) { |
150 | list_del_rcu(&walk->list); |
151 | kfree_rcu(walk, rcu); |
152 | } |
153 | } |
154 | } |
155 | |
156 | /* |
157 | * called from kernel/cgroup.c with cgroup_lock() held. |
158 | */ |
159 | static struct cgroup_subsys_state *devcgroup_create(struct cgroup_subsys *ss, |
160 | struct cgroup *cgroup) |
161 | { |
162 | struct dev_cgroup *dev_cgroup, *parent_dev_cgroup; |
163 | struct cgroup *parent_cgroup; |
164 | int ret; |
165 | |
166 | dev_cgroup = kzalloc(sizeof(*dev_cgroup), GFP_KERNEL); |
167 | if (!dev_cgroup) |
168 | return ERR_PTR(-ENOMEM); |
169 | INIT_LIST_HEAD(&dev_cgroup->whitelist); |
170 | parent_cgroup = cgroup->parent; |
171 | |
172 | if (parent_cgroup == NULL) { |
173 | struct dev_whitelist_item *wh; |
174 | wh = kmalloc(sizeof(*wh), GFP_KERNEL); |
175 | if (!wh) { |
176 | kfree(dev_cgroup); |
177 | return ERR_PTR(-ENOMEM); |
178 | } |
179 | wh->minor = wh->major = ~0; |
180 | wh->type = DEV_ALL; |
181 | wh->access = ACC_MASK; |
182 | list_add(&wh->list, &dev_cgroup->whitelist); |
183 | } else { |
184 | parent_dev_cgroup = cgroup_to_devcgroup(parent_cgroup); |
185 | mutex_lock(&devcgroup_mutex); |
186 | ret = dev_whitelist_copy(&dev_cgroup->whitelist, |
187 | &parent_dev_cgroup->whitelist); |
188 | mutex_unlock(&devcgroup_mutex); |
189 | if (ret) { |
190 | kfree(dev_cgroup); |
191 | return ERR_PTR(ret); |
192 | } |
193 | } |
194 | |
195 | return &dev_cgroup->css; |
196 | } |
197 | |
198 | static void devcgroup_destroy(struct cgroup_subsys *ss, |
199 | struct cgroup *cgroup) |
200 | { |
201 | struct dev_cgroup *dev_cgroup; |
202 | struct dev_whitelist_item *wh, *tmp; |
203 | |
204 | dev_cgroup = cgroup_to_devcgroup(cgroup); |
205 | list_for_each_entry_safe(wh, tmp, &dev_cgroup->whitelist, list) { |
206 | list_del(&wh->list); |
207 | kfree(wh); |
208 | } |
209 | kfree(dev_cgroup); |
210 | } |
211 | |
212 | #define DEVCG_ALLOW 1 |
213 | #define DEVCG_DENY 2 |
214 | #define DEVCG_LIST 3 |
215 | |
216 | #define MAJMINLEN 13 |
217 | #define ACCLEN 4 |
218 | |
219 | static void set_access(char *acc, short access) |
220 | { |
221 | int idx = 0; |
222 | memset(acc, 0, ACCLEN); |
223 | if (access & ACC_READ) |
224 | acc[idx++] = 'r'; |
225 | if (access & ACC_WRITE) |
226 | acc[idx++] = 'w'; |
227 | if (access & ACC_MKNOD) |
228 | acc[idx++] = 'm'; |
229 | } |
230 | |
231 | static char type_to_char(short type) |
232 | { |
233 | if (type == DEV_ALL) |
234 | return 'a'; |
235 | if (type == DEV_CHAR) |
236 | return 'c'; |
237 | if (type == DEV_BLOCK) |
238 | return 'b'; |
239 | return 'X'; |
240 | } |
241 | |
242 | static void set_majmin(char *str, unsigned m) |
243 | { |
244 | if (m == ~0) |
245 | strcpy(str, "*"); |
246 | else |
247 | sprintf(str, "%u", m); |
248 | } |
249 | |
250 | static int devcgroup_seq_read(struct cgroup *cgroup, struct cftype *cft, |
251 | struct seq_file *m) |
252 | { |
253 | struct dev_cgroup *devcgroup = cgroup_to_devcgroup(cgroup); |
254 | struct dev_whitelist_item *wh; |
255 | char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN]; |
256 | |
257 | rcu_read_lock(); |
258 | list_for_each_entry_rcu(wh, &devcgroup->whitelist, list) { |
259 | set_access(acc, wh->access); |
260 | set_majmin(maj, wh->major); |
261 | set_majmin(min, wh->minor); |
262 | seq_printf(m, "%c %s:%s %s\n", type_to_char(wh->type), |
263 | maj, min, acc); |
264 | } |
265 | rcu_read_unlock(); |
266 | |
267 | return 0; |
268 | } |
269 | |
270 | /* |
271 | * may_access_whitelist: |
272 | * does the access granted to dev_cgroup c contain the access |
273 | * requested in whitelist item refwh. |
274 | * return 1 if yes, 0 if no. |
275 | * call with devcgroup_mutex held |
276 | */ |
277 | static int may_access_whitelist(struct dev_cgroup *c, |
278 | struct dev_whitelist_item *refwh) |
279 | { |
280 | struct dev_whitelist_item *whitem; |
281 | |
282 | list_for_each_entry(whitem, &c->whitelist, list) { |
283 | if (whitem->type & DEV_ALL) |
284 | return 1; |
285 | if ((refwh->type & DEV_BLOCK) && !(whitem->type & DEV_BLOCK)) |
286 | continue; |
287 | if ((refwh->type & DEV_CHAR) && !(whitem->type & DEV_CHAR)) |
288 | continue; |
289 | if (whitem->major != ~0 && whitem->major != refwh->major) |
290 | continue; |
291 | if (whitem->minor != ~0 && whitem->minor != refwh->minor) |
292 | continue; |
293 | if (refwh->access & (~whitem->access)) |
294 | continue; |
295 | return 1; |
296 | } |
297 | return 0; |
298 | } |
299 | |
300 | /* |
301 | * parent_has_perm: |
302 | * when adding a new allow rule to a device whitelist, the rule |
303 | * must be allowed in the parent device |
304 | */ |
305 | static int parent_has_perm(struct dev_cgroup *childcg, |
306 | struct dev_whitelist_item *wh) |
307 | { |
308 | struct cgroup *pcg = childcg->css.cgroup->parent; |
309 | struct dev_cgroup *parent; |
310 | |
311 | if (!pcg) |
312 | return 1; |
313 | parent = cgroup_to_devcgroup(pcg); |
314 | return may_access_whitelist(parent, wh); |
315 | } |
316 | |
317 | /* |
318 | * Modify the whitelist using allow/deny rules. |
319 | * CAP_SYS_ADMIN is needed for this. It's at least separate from CAP_MKNOD |
320 | * so we can give a container CAP_MKNOD to let it create devices but not |
321 | * modify the whitelist. |
322 | * It seems likely we'll want to add a CAP_CONTAINER capability to allow |
323 | * us to also grant CAP_SYS_ADMIN to containers without giving away the |
324 | * device whitelist controls, but for now we'll stick with CAP_SYS_ADMIN |
325 | * |
326 | * Taking rules away is always allowed (given CAP_SYS_ADMIN). Granting |
327 | * new access is only allowed if you're in the top-level cgroup, or your |
328 | * parent cgroup has the access you're asking for. |
329 | */ |
330 | static int devcgroup_update_access(struct dev_cgroup *devcgroup, |
331 | int filetype, const char *buffer) |
332 | { |
333 | const char *b; |
334 | char *endp; |
335 | int count; |
336 | struct dev_whitelist_item wh; |
337 | |
338 | if (!capable(CAP_SYS_ADMIN)) |
339 | return -EPERM; |
340 | |
341 | memset(&wh, 0, sizeof(wh)); |
342 | b = buffer; |
343 | |
344 | switch (*b) { |
345 | case 'a': |
346 | wh.type = DEV_ALL; |
347 | wh.access = ACC_MASK; |
348 | wh.major = ~0; |
349 | wh.minor = ~0; |
350 | goto handle; |
351 | case 'b': |
352 | wh.type = DEV_BLOCK; |
353 | break; |
354 | case 'c': |
355 | wh.type = DEV_CHAR; |
356 | break; |
357 | default: |
358 | return -EINVAL; |
359 | } |
360 | b++; |
361 | if (!isspace(*b)) |
362 | return -EINVAL; |
363 | b++; |
364 | if (*b == '*') { |
365 | wh.major = ~0; |
366 | b++; |
367 | } else if (isdigit(*b)) { |
368 | wh.major = simple_strtoul(b, &endp, 10); |
369 | b = endp; |
370 | } else { |
371 | return -EINVAL; |
372 | } |
373 | if (*b != ':') |
374 | return -EINVAL; |
375 | b++; |
376 | |
377 | /* read minor */ |
378 | if (*b == '*') { |
379 | wh.minor = ~0; |
380 | b++; |
381 | } else if (isdigit(*b)) { |
382 | wh.minor = simple_strtoul(b, &endp, 10); |
383 | b = endp; |
384 | } else { |
385 | return -EINVAL; |
386 | } |
387 | if (!isspace(*b)) |
388 | return -EINVAL; |
389 | for (b++, count = 0; count < 3; count++, b++) { |
390 | switch (*b) { |
391 | case 'r': |
392 | wh.access |= ACC_READ; |
393 | break; |
394 | case 'w': |
395 | wh.access |= ACC_WRITE; |
396 | break; |
397 | case 'm': |
398 | wh.access |= ACC_MKNOD; |
399 | break; |
400 | case '\n': |
401 | case '\0': |
402 | count = 3; |
403 | break; |
404 | default: |
405 | return -EINVAL; |
406 | } |
407 | } |
408 | |
409 | handle: |
410 | switch (filetype) { |
411 | case DEVCG_ALLOW: |
412 | if (!parent_has_perm(devcgroup, &wh)) |
413 | return -EPERM; |
414 | return dev_whitelist_add(devcgroup, &wh); |
415 | case DEVCG_DENY: |
416 | dev_whitelist_rm(devcgroup, &wh); |
417 | break; |
418 | default: |
419 | return -EINVAL; |
420 | } |
421 | return 0; |
422 | } |
423 | |
424 | static int devcgroup_access_write(struct cgroup *cgrp, struct cftype *cft, |
425 | const char *buffer) |
426 | { |
427 | int retval; |
428 | |
429 | mutex_lock(&devcgroup_mutex); |
430 | retval = devcgroup_update_access(cgroup_to_devcgroup(cgrp), |
431 | cft->private, buffer); |
432 | mutex_unlock(&devcgroup_mutex); |
433 | return retval; |
434 | } |
435 | |
436 | static struct cftype dev_cgroup_files[] = { |
437 | { |
438 | .name = "allow", |
439 | .write_string = devcgroup_access_write, |
440 | .private = DEVCG_ALLOW, |
441 | }, |
442 | { |
443 | .name = "deny", |
444 | .write_string = devcgroup_access_write, |
445 | .private = DEVCG_DENY, |
446 | }, |
447 | { |
448 | .name = "list", |
449 | .read_seq_string = devcgroup_seq_read, |
450 | .private = DEVCG_LIST, |
451 | }, |
452 | }; |
453 | |
454 | static int devcgroup_populate(struct cgroup_subsys *ss, |
455 | struct cgroup *cgroup) |
456 | { |
457 | return cgroup_add_files(cgroup, ss, dev_cgroup_files, |
458 | ARRAY_SIZE(dev_cgroup_files)); |
459 | } |
460 | |
461 | struct cgroup_subsys devices_subsys = { |
462 | .name = "devices", |
463 | .can_attach = devcgroup_can_attach, |
464 | .create = devcgroup_create, |
465 | .destroy = devcgroup_destroy, |
466 | .populate = devcgroup_populate, |
467 | .subsys_id = devices_subsys_id, |
468 | }; |
469 | |
470 | int __devcgroup_inode_permission(struct inode *inode, int mask) |
471 | { |
472 | struct dev_cgroup *dev_cgroup; |
473 | struct dev_whitelist_item *wh; |
474 | |
475 | rcu_read_lock(); |
476 | |
477 | dev_cgroup = task_devcgroup(current); |
478 | |
479 | list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) { |
480 | if (wh->type & DEV_ALL) |
481 | goto found; |
482 | if ((wh->type & DEV_BLOCK) && !S_ISBLK(inode->i_mode)) |
483 | continue; |
484 | if ((wh->type & DEV_CHAR) && !S_ISCHR(inode->i_mode)) |
485 | continue; |
486 | if (wh->major != ~0 && wh->major != imajor(inode)) |
487 | continue; |
488 | if (wh->minor != ~0 && wh->minor != iminor(inode)) |
489 | continue; |
490 | |
491 | if ((mask & MAY_WRITE) && !(wh->access & ACC_WRITE)) |
492 | continue; |
493 | if ((mask & MAY_READ) && !(wh->access & ACC_READ)) |
494 | continue; |
495 | found: |
496 | rcu_read_unlock(); |
497 | return 0; |
498 | } |
499 | |
500 | rcu_read_unlock(); |
501 | |
502 | return -EPERM; |
503 | } |
504 | |
505 | int devcgroup_inode_mknod(int mode, dev_t dev) |
506 | { |
507 | struct dev_cgroup *dev_cgroup; |
508 | struct dev_whitelist_item *wh; |
509 | |
510 | if (!S_ISBLK(mode) && !S_ISCHR(mode)) |
511 | return 0; |
512 | |
513 | rcu_read_lock(); |
514 | |
515 | dev_cgroup = task_devcgroup(current); |
516 | |
517 | list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) { |
518 | if (wh->type & DEV_ALL) |
519 | goto found; |
520 | if ((wh->type & DEV_BLOCK) && !S_ISBLK(mode)) |
521 | continue; |
522 | if ((wh->type & DEV_CHAR) && !S_ISCHR(mode)) |
523 | continue; |
524 | if (wh->major != ~0 && wh->major != MAJOR(dev)) |
525 | continue; |
526 | if (wh->minor != ~0 && wh->minor != MINOR(dev)) |
527 | continue; |
528 | |
529 | if (!(wh->access & ACC_MKNOD)) |
530 | continue; |
531 | found: |
532 | rcu_read_unlock(); |
533 | return 0; |
534 | } |
535 | |
536 | rcu_read_unlock(); |
537 | |
538 | return -EPERM; |
539 | } |
540 |
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