Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / security / device_cgroup.c
blob4450fbeec411beed1ac7870b8820fdb850b736bf
1 /*
2 * device_cgroup.c - device cgroup subsystem
4 * Copyright 2007 IBM Corp
5 */
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>
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)
22 #define DEV_BLOCK 1
23 #define DEV_CHAR 2
24 #define DEV_ALL 4 /* this represents all devices */
26 static DEFINE_MUTEX(devcgroup_mutex);
29 * whitelist locking rules:
30 * hold devcgroup_mutex for update/read.
31 * hold rcu_read_lock() for read.
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;
42 struct dev_cgroup {
43 struct cgroup_subsys_state css;
44 struct list_head whitelist;
47 static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s)
49 return container_of(s, struct dev_cgroup, css);
52 static inline struct dev_cgroup *cgroup_to_devcgroup(struct cgroup *cgroup)
54 return css_to_devcgroup(cgroup_subsys_state(cgroup, devices_subsys_id));
57 static inline struct dev_cgroup *task_devcgroup(struct task_struct *task)
59 return css_to_devcgroup(task_subsys_state(task, devices_subsys_id));
62 struct cgroup_subsys devices_subsys;
64 static int devcgroup_can_attach(struct cgroup_subsys *ss,
65 struct cgroup *new_cgroup, struct task_struct *task)
67 if (current != task && !capable(CAP_SYS_ADMIN))
68 return -EPERM;
70 return 0;
74 * called under devcgroup_mutex
76 static int dev_whitelist_copy(struct list_head *dest, struct list_head *orig)
78 struct dev_whitelist_item *wh, *tmp, *new;
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);
87 return 0;
89 free_and_exit:
90 list_for_each_entry_safe(wh, tmp, dest, list) {
91 list_del(&wh->list);
92 kfree(wh);
94 return -ENOMEM;
97 /* Stupid prototype - don't bother combining existing entries */
99 * called under devcgroup_mutex
101 static int dev_whitelist_add(struct dev_cgroup *dev_cgroup,
102 struct dev_whitelist_item *wh)
104 struct dev_whitelist_item *whcopy, *walk;
106 whcopy = kmemdup(wh, sizeof(*wh), GFP_KERNEL);
107 if (!whcopy)
108 return -ENOMEM;
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;
118 walk->access |= wh->access;
119 kfree(whcopy);
120 whcopy = NULL;
123 if (whcopy != NULL)
124 list_add_tail_rcu(&whcopy->list, &dev_cgroup->whitelist);
125 return 0;
129 * called under devcgroup_mutex
131 static void dev_whitelist_rm(struct dev_cgroup *dev_cgroup,
132 struct dev_whitelist_item *wh)
134 struct dev_whitelist_item *walk, *tmp;
136 list_for_each_entry_safe(walk, tmp, &dev_cgroup->whitelist, list) {
137 if (walk->type == DEV_ALL)
138 goto remove;
139 if (walk->type != wh->type)
140 continue;
141 if (walk->major != ~0 && walk->major != wh->major)
142 continue;
143 if (walk->minor != ~0 && walk->minor != wh->minor)
144 continue;
146 remove:
147 walk->access &= ~wh->access;
148 if (!walk->access) {
149 list_del_rcu(&walk->list);
150 kfree_rcu(walk, rcu);
156 * called from kernel/cgroup.c with cgroup_lock() held.
158 static struct cgroup_subsys_state *devcgroup_create(struct cgroup_subsys *ss,
159 struct cgroup *cgroup)
161 struct dev_cgroup *dev_cgroup, *parent_dev_cgroup;
162 struct cgroup *parent_cgroup;
163 int ret;
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;
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);
178 wh->minor = wh->major = ~0;
179 wh->type = DEV_ALL;
180 wh->access = ACC_MASK;
181 list_add(&wh->list, &dev_cgroup->whitelist);
182 } else {
183 parent_dev_cgroup = cgroup_to_devcgroup(parent_cgroup);
184 mutex_lock(&devcgroup_mutex);
185 ret = dev_whitelist_copy(&dev_cgroup->whitelist,
186 &parent_dev_cgroup->whitelist);
187 mutex_unlock(&devcgroup_mutex);
188 if (ret) {
189 kfree(dev_cgroup);
190 return ERR_PTR(ret);
194 return &dev_cgroup->css;
197 static void devcgroup_destroy(struct cgroup_subsys *ss,
198 struct cgroup *cgroup)
200 struct dev_cgroup *dev_cgroup;
201 struct dev_whitelist_item *wh, *tmp;
203 dev_cgroup = cgroup_to_devcgroup(cgroup);
204 list_for_each_entry_safe(wh, tmp, &dev_cgroup->whitelist, list) {
205 list_del(&wh->list);
206 kfree(wh);
208 kfree(dev_cgroup);
211 #define DEVCG_ALLOW 1
212 #define DEVCG_DENY 2
213 #define DEVCG_LIST 3
215 #define MAJMINLEN 13
216 #define ACCLEN 4
218 static void set_access(char *acc, short access)
220 int idx = 0;
221 memset(acc, 0, ACCLEN);
222 if (access & ACC_READ)
223 acc[idx++] = 'r';
224 if (access & ACC_WRITE)
225 acc[idx++] = 'w';
226 if (access & ACC_MKNOD)
227 acc[idx++] = 'm';
230 static char type_to_char(short type)
232 if (type == DEV_ALL)
233 return 'a';
234 if (type == DEV_CHAR)
235 return 'c';
236 if (type == DEV_BLOCK)
237 return 'b';
238 return 'X';
241 static void set_majmin(char *str, unsigned m)
243 if (m == ~0)
244 strcpy(str, "*");
245 else
246 sprintf(str, "%u", m);
249 static int devcgroup_seq_read(struct cgroup *cgroup, struct cftype *cft,
250 struct seq_file *m)
252 struct dev_cgroup *devcgroup = cgroup_to_devcgroup(cgroup);
253 struct dev_whitelist_item *wh;
254 char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN];
256 rcu_read_lock();
257 list_for_each_entry_rcu(wh, &devcgroup->whitelist, list) {
258 set_access(acc, wh->access);
259 set_majmin(maj, wh->major);
260 set_majmin(min, wh->minor);
261 seq_printf(m, "%c %s:%s %s\n", type_to_char(wh->type),
262 maj, min, acc);
264 rcu_read_unlock();
266 return 0;
270 * may_access_whitelist:
271 * does the access granted to dev_cgroup c contain the access
272 * requested in whitelist item refwh.
273 * return 1 if yes, 0 if no.
274 * call with devcgroup_mutex held
276 static int may_access_whitelist(struct dev_cgroup *c,
277 struct dev_whitelist_item *refwh)
279 struct dev_whitelist_item *whitem;
281 list_for_each_entry(whitem, &c->whitelist, list) {
282 if (whitem->type & DEV_ALL)
283 return 1;
284 if ((refwh->type & DEV_BLOCK) && !(whitem->type & DEV_BLOCK))
285 continue;
286 if ((refwh->type & DEV_CHAR) && !(whitem->type & DEV_CHAR))
287 continue;
288 if (whitem->major != ~0 && whitem->major != refwh->major)
289 continue;
290 if (whitem->minor != ~0 && whitem->minor != refwh->minor)
291 continue;
292 if (refwh->access & (~whitem->access))
293 continue;
294 return 1;
296 return 0;
300 * parent_has_perm:
301 * when adding a new allow rule to a device whitelist, the rule
302 * must be allowed in the parent device
304 static int parent_has_perm(struct dev_cgroup *childcg,
305 struct dev_whitelist_item *wh)
307 struct cgroup *pcg = childcg->css.cgroup->parent;
308 struct dev_cgroup *parent;
310 if (!pcg)
311 return 1;
312 parent = cgroup_to_devcgroup(pcg);
313 return may_access_whitelist(parent, wh);
317 * Modify the whitelist using allow/deny rules.
318 * CAP_SYS_ADMIN is needed for this. It's at least separate from CAP_MKNOD
319 * so we can give a container CAP_MKNOD to let it create devices but not
320 * modify the whitelist.
321 * It seems likely we'll want to add a CAP_CONTAINER capability to allow
322 * us to also grant CAP_SYS_ADMIN to containers without giving away the
323 * device whitelist controls, but for now we'll stick with CAP_SYS_ADMIN
325 * Taking rules away is always allowed (given CAP_SYS_ADMIN). Granting
326 * new access is only allowed if you're in the top-level cgroup, or your
327 * parent cgroup has the access you're asking for.
329 static int devcgroup_update_access(struct dev_cgroup *devcgroup,
330 int filetype, const char *buffer)
332 const char *b;
333 char *endp;
334 int count;
335 struct dev_whitelist_item wh;
337 if (!capable(CAP_SYS_ADMIN))
338 return -EPERM;
340 memset(&wh, 0, sizeof(wh));
341 b = buffer;
343 switch (*b) {
344 case 'a':
345 wh.type = DEV_ALL;
346 wh.access = ACC_MASK;
347 wh.major = ~0;
348 wh.minor = ~0;
349 goto handle;
350 case 'b':
351 wh.type = DEV_BLOCK;
352 break;
353 case 'c':
354 wh.type = DEV_CHAR;
355 break;
356 default:
357 return -EINVAL;
359 b++;
360 if (!isspace(*b))
361 return -EINVAL;
362 b++;
363 if (*b == '*') {
364 wh.major = ~0;
365 b++;
366 } else if (isdigit(*b)) {
367 wh.major = simple_strtoul(b, &endp, 10);
368 b = endp;
369 } else {
370 return -EINVAL;
372 if (*b != ':')
373 return -EINVAL;
374 b++;
376 /* read minor */
377 if (*b == '*') {
378 wh.minor = ~0;
379 b++;
380 } else if (isdigit(*b)) {
381 wh.minor = simple_strtoul(b, &endp, 10);
382 b = endp;
383 } else {
384 return -EINVAL;
386 if (!isspace(*b))
387 return -EINVAL;
388 for (b++, count = 0; count < 3; count++, b++) {
389 switch (*b) {
390 case 'r':
391 wh.access |= ACC_READ;
392 break;
393 case 'w':
394 wh.access |= ACC_WRITE;
395 break;
396 case 'm':
397 wh.access |= ACC_MKNOD;
398 break;
399 case '\n':
400 case '\0':
401 count = 3;
402 break;
403 default:
404 return -EINVAL;
408 handle:
409 switch (filetype) {
410 case DEVCG_ALLOW:
411 if (!parent_has_perm(devcgroup, &wh))
412 return -EPERM;
413 return dev_whitelist_add(devcgroup, &wh);
414 case DEVCG_DENY:
415 dev_whitelist_rm(devcgroup, &wh);
416 break;
417 default:
418 return -EINVAL;
420 return 0;
423 static int devcgroup_access_write(struct cgroup *cgrp, struct cftype *cft,
424 const char *buffer)
426 int retval;
428 mutex_lock(&devcgroup_mutex);
429 retval = devcgroup_update_access(cgroup_to_devcgroup(cgrp),
430 cft->private, buffer);
431 mutex_unlock(&devcgroup_mutex);
432 return retval;
435 static struct cftype dev_cgroup_files[] = {
437 .name = "allow",
438 .write_string = devcgroup_access_write,
439 .private = DEVCG_ALLOW,
442 .name = "deny",
443 .write_string = devcgroup_access_write,
444 .private = DEVCG_DENY,
447 .name = "list",
448 .read_seq_string = devcgroup_seq_read,
449 .private = DEVCG_LIST,
453 static int devcgroup_populate(struct cgroup_subsys *ss,
454 struct cgroup *cgroup)
456 return cgroup_add_files(cgroup, ss, dev_cgroup_files,
457 ARRAY_SIZE(dev_cgroup_files));
460 struct cgroup_subsys devices_subsys = {
461 .name = "devices",
462 .can_attach = devcgroup_can_attach,
463 .create = devcgroup_create,
464 .destroy = devcgroup_destroy,
465 .populate = devcgroup_populate,
466 .subsys_id = devices_subsys_id,
469 int __devcgroup_inode_permission(struct inode *inode, int mask)
471 struct dev_cgroup *dev_cgroup;
472 struct dev_whitelist_item *wh;
474 rcu_read_lock();
476 dev_cgroup = task_devcgroup(current);
478 list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) {
479 if (wh->type & DEV_ALL)
480 goto found;
481 if ((wh->type & DEV_BLOCK) && !S_ISBLK(inode->i_mode))
482 continue;
483 if ((wh->type & DEV_CHAR) && !S_ISCHR(inode->i_mode))
484 continue;
485 if (wh->major != ~0 && wh->major != imajor(inode))
486 continue;
487 if (wh->minor != ~0 && wh->minor != iminor(inode))
488 continue;
490 if ((mask & MAY_WRITE) && !(wh->access & ACC_WRITE))
491 continue;
492 if ((mask & MAY_READ) && !(wh->access & ACC_READ))
493 continue;
494 found:
495 rcu_read_unlock();
496 return 0;
499 rcu_read_unlock();
501 return -EPERM;
504 int devcgroup_inode_mknod(int mode, dev_t dev)
506 struct dev_cgroup *dev_cgroup;
507 struct dev_whitelist_item *wh;
509 if (!S_ISBLK(mode) && !S_ISCHR(mode))
510 return 0;
512 rcu_read_lock();
514 dev_cgroup = task_devcgroup(current);
516 list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) {
517 if (wh->type & DEV_ALL)
518 goto found;
519 if ((wh->type & DEV_BLOCK) && !S_ISBLK(mode))
520 continue;
521 if ((wh->type & DEV_CHAR) && !S_ISCHR(mode))
522 continue;
523 if (wh->major != ~0 && wh->major != MAJOR(dev))
524 continue;
525 if (wh->minor != ~0 && wh->minor != MINOR(dev))
526 continue;
528 if (!(wh->access & ACC_MKNOD))
529 continue;
530 found:
531 rcu_read_unlock();
532 return 0;
535 rcu_read_unlock();
537 return -EPERM;