blob: ddd92cec78ed81c44bcfc4d9c530662a179381f2 [file] [log] [blame]
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -07001/*
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>
Serge E. Hallyn29486df2008-04-29 01:00:14 -070012#include <linux/seq_file.h>
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070013
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
39struct dev_whitelist_item {
40 u32 major, minor;
41 short type;
42 short access;
43 struct list_head list;
44};
45
46struct dev_cgroup {
47 struct cgroup_subsys_state css;
48 struct list_head whitelist;
49 spinlock_t lock;
50};
51
Pavel Emelyanovb66862f2008-06-05 22:46:24 -070052static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s)
53{
54 return container_of(s, struct dev_cgroup, css);
55}
56
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070057static inline struct dev_cgroup *cgroup_to_devcgroup(struct cgroup *cgroup)
58{
Pavel Emelyanovb66862f2008-06-05 22:46:24 -070059 return css_to_devcgroup(cgroup_subsys_state(cgroup, devices_subsys_id));
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070060}
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 cgroup_lock()
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 = 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
93free_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 */
106static int dev_whitelist_add(struct dev_cgroup *dev_cgroup,
107 struct dev_whitelist_item *wh)
108{
Pavel Emelyanovd1ee2972008-06-05 22:46:28 -0700109 struct dev_whitelist_item *whcopy, *walk;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700110
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);
Pavel Emelyanovd1ee2972008-06-05 22:46:28 -0700117 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);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700132 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 */
140static 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
156remove:
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 */
169static 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
207static 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
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700223#define DEVCG_LIST 3
224
Li Zefan17d213f2008-07-13 12:14:02 -0700225#define MAJMINLEN 13
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700226#define ACCLEN 4
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700227
228static void set_access(char *acc, short access)
229{
230 int idx = 0;
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700231 memset(acc, 0, ACCLEN);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700232 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
240static 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
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700251static void set_majmin(char *str, unsigned m)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700252{
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700253 memset(str, 0, MAJMINLEN);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700254 if (m == ~0)
255 sprintf(str, "*");
256 else
Li Zefan17d213f2008-07-13 12:14:02 -0700257 snprintf(str, MAJMINLEN, "%u", m);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700258}
259
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700260static int devcgroup_seq_read(struct cgroup *cgroup, struct cftype *cft,
261 struct seq_file *m)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700262{
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700263 struct dev_cgroup *devcgroup = cgroup_to_devcgroup(cgroup);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700264 struct dev_whitelist_item *wh;
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700265 char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN];
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700266
267 spin_lock(&devcgroup->lock);
268 list_for_each_entry(wh, &devcgroup->whitelist, list) {
269 set_access(acc, wh->access);
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700270 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);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700274 }
275 spin_unlock(&devcgroup->lock);
276
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700277 return 0;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700278}
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 */
287static 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;
Li Zefanec229e82008-07-13 12:14:04 -0700303 if (refwh->access & (~whitem->access))
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700304 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 */
315static 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 */
344static 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;
Li Zefand823f6b2008-07-04 10:00:07 -0700385 wh.major = ~0;
386 wh.minor = ~0;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700387 goto handle;
388 case 'b':
389 wh.type = DEV_BLOCK;
390 break;
391 case 'c':
392 wh.type = DEV_CHAR;
393 break;
394 default:
395 retval = -EINVAL;
396 goto out2;
397 }
398 b++;
399 if (!isspace(*b)) {
400 retval = -EINVAL;
401 goto out2;
402 }
403 b++;
404 if (*b == '*') {
405 wh.major = ~0;
406 b++;
407 } else if (isdigit(*b)) {
408 wh.major = 0;
409 while (isdigit(*b)) {
410 wh.major = wh.major*10+(*b-'0');
411 b++;
412 }
413 } else {
414 retval = -EINVAL;
415 goto out2;
416 }
417 if (*b != ':') {
418 retval = -EINVAL;
419 goto out2;
420 }
421 b++;
422
423 /* read minor */
424 if (*b == '*') {
425 wh.minor = ~0;
426 b++;
427 } else if (isdigit(*b)) {
428 wh.minor = 0;
429 while (isdigit(*b)) {
430 wh.minor = wh.minor*10+(*b-'0');
431 b++;
432 }
433 } else {
434 retval = -EINVAL;
435 goto out2;
436 }
437 if (!isspace(*b)) {
438 retval = -EINVAL;
439 goto out2;
440 }
441 for (b++, count = 0; count < 3; count++, b++) {
442 switch (*b) {
443 case 'r':
444 wh.access |= ACC_READ;
445 break;
446 case 'w':
447 wh.access |= ACC_WRITE;
448 break;
449 case 'm':
450 wh.access |= ACC_MKNOD;
451 break;
452 case '\n':
453 case '\0':
454 count = 3;
455 break;
456 default:
457 retval = -EINVAL;
458 goto out2;
459 }
460 }
461
462handle:
463 retval = 0;
464 switch (filetype) {
465 case DEVCG_ALLOW:
466 if (!parent_has_perm(cgroup, &wh))
467 retval = -EPERM;
468 else
469 retval = dev_whitelist_add(devcgroup, &wh);
470 break;
471 case DEVCG_DENY:
472 dev_whitelist_rm(devcgroup, &wh);
473 break;
474 default:
475 retval = -EINVAL;
476 goto out2;
477 }
478
479 if (retval == 0)
480 retval = nbytes;
481
482out2:
483 cgroup_unlock();
484out1:
485 kfree(buffer);
486 return retval;
487}
488
489static struct cftype dev_cgroup_files[] = {
490 {
491 .name = "allow",
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700492 .write = devcgroup_access_write,
493 .private = DEVCG_ALLOW,
494 },
495 {
496 .name = "deny",
497 .write = devcgroup_access_write,
498 .private = DEVCG_DENY,
499 },
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700500 {
501 .name = "list",
502 .read_seq_string = devcgroup_seq_read,
503 .private = DEVCG_LIST,
504 },
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700505};
506
507static int devcgroup_populate(struct cgroup_subsys *ss,
508 struct cgroup *cgroup)
509{
510 return cgroup_add_files(cgroup, ss, dev_cgroup_files,
511 ARRAY_SIZE(dev_cgroup_files));
512}
513
514struct cgroup_subsys devices_subsys = {
515 .name = "devices",
516 .can_attach = devcgroup_can_attach,
517 .create = devcgroup_create,
518 .destroy = devcgroup_destroy,
519 .populate = devcgroup_populate,
520 .subsys_id = devices_subsys_id,
521};
522
523int devcgroup_inode_permission(struct inode *inode, int mask)
524{
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700525 struct dev_cgroup *dev_cgroup;
526 struct dev_whitelist_item *wh;
527
528 dev_t device = inode->i_rdev;
529 if (!device)
530 return 0;
531 if (!S_ISBLK(inode->i_mode) && !S_ISCHR(inode->i_mode))
532 return 0;
Pavel Emelyanovcc9cb212008-06-05 22:46:26 -0700533 dev_cgroup = css_to_devcgroup(task_subsys_state(current,
534 devices_subsys_id));
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700535 if (!dev_cgroup)
536 return 0;
537
538 spin_lock(&dev_cgroup->lock);
539 list_for_each_entry(wh, &dev_cgroup->whitelist, list) {
540 if (wh->type & DEV_ALL)
541 goto acc_check;
542 if ((wh->type & DEV_BLOCK) && !S_ISBLK(inode->i_mode))
543 continue;
544 if ((wh->type & DEV_CHAR) && !S_ISCHR(inode->i_mode))
545 continue;
546 if (wh->major != ~0 && wh->major != imajor(inode))
547 continue;
548 if (wh->minor != ~0 && wh->minor != iminor(inode))
549 continue;
550acc_check:
551 if ((mask & MAY_WRITE) && !(wh->access & ACC_WRITE))
552 continue;
553 if ((mask & MAY_READ) && !(wh->access & ACC_READ))
554 continue;
555 spin_unlock(&dev_cgroup->lock);
556 return 0;
557 }
558 spin_unlock(&dev_cgroup->lock);
559
560 return -EPERM;
561}
562
563int devcgroup_inode_mknod(int mode, dev_t dev)
564{
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700565 struct dev_cgroup *dev_cgroup;
566 struct dev_whitelist_item *wh;
567
Pavel Emelyanovcc9cb212008-06-05 22:46:26 -0700568 dev_cgroup = css_to_devcgroup(task_subsys_state(current,
569 devices_subsys_id));
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700570 if (!dev_cgroup)
571 return 0;
572
573 spin_lock(&dev_cgroup->lock);
574 list_for_each_entry(wh, &dev_cgroup->whitelist, list) {
575 if (wh->type & DEV_ALL)
576 goto acc_check;
577 if ((wh->type & DEV_BLOCK) && !S_ISBLK(mode))
578 continue;
579 if ((wh->type & DEV_CHAR) && !S_ISCHR(mode))
580 continue;
581 if (wh->major != ~0 && wh->major != MAJOR(dev))
582 continue;
583 if (wh->minor != ~0 && wh->minor != MINOR(dev))
584 continue;
585acc_check:
586 if (!(wh->access & ACC_MKNOD))
587 continue;
588 spin_unlock(&dev_cgroup->lock);
589 return 0;
590 }
591 spin_unlock(&dev_cgroup->lock);
592 return -EPERM;
593}