projects/linux·blob v3.0 · refs

546 lines · 11.6 KiB

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