bluetooth: Properly clone LSM attributes to newly created child connections
[linux-2.6.git] / security / device_cgroup.c
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_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  */
76 static 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
89 free_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  */
101 static 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
128 /*
129  * called under devcgroup_mutex
130  */
131 static void dev_whitelist_rm(struct dev_cgroup *dev_cgroup,
132                         struct dev_whitelist_item *wh)
133 {
134         struct dev_whitelist_item *walk, *tmp;
135
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;
145
146 remove:
147                 walk->access &= ~wh->access;
148                 if (!walk->access) {
149                         list_del_rcu(&walk->list);
150                         kfree_rcu(walk, rcu);
151                 }
152         }
153 }
154
155 /*
156  * called from kernel/cgroup.c with cgroup_lock() held.
157  */
158 static struct cgroup_subsys_state *devcgroup_create(struct cgroup_subsys *ss,
159                                                 struct cgroup *cgroup)
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;
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);
191                 }
192         }
193
194         return &dev_cgroup->css;
195 }
196
197 static void devcgroup_destroy(struct cgroup_subsys *ss,
198                         struct cgroup *cgroup)
199 {
200         struct dev_cgroup *dev_cgroup;
201         struct dev_whitelist_item *wh, *tmp;
202
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);
207         }
208         kfree(dev_cgroup);
209 }
210
211 #define DEVCG_ALLOW 1
212 #define DEVCG_DENY 2
213 #define DEVCG_LIST 3
214
215 #define MAJMINLEN 13
216 #define ACCLEN 4
217
218 static void set_access(char *acc, short access)
219 {
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';
228 }
229
230 static char type_to_char(short type)
231 {
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';
239 }
240
241 static void set_majmin(char *str, unsigned m)
242 {
243         if (m == ~0)
244                 strcpy(str, "*");
245         else
246                 sprintf(str, "%u", m);
247 }
248
249 static int devcgroup_seq_read(struct cgroup *cgroup, struct cftype *cft,
250                                 struct seq_file *m)
251 {
252         struct dev_cgroup *devcgroup = cgroup_to_devcgroup(cgroup);
253         struct dev_whitelist_item *wh;
254         char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN];
255
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);
263         }
264         rcu_read_unlock();
265
266         return 0;
267 }
268
269 /*
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
275  */
276 static int may_access_whitelist(struct dev_cgroup *c,
277                                        struct dev_whitelist_item *refwh)
278 {
279         struct dev_whitelist_item *whitem;
280
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;
295         }
296         return 0;
297 }
298
299 /*
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
303  */
304 static int parent_has_perm(struct dev_cgroup *childcg,
305                                   struct dev_whitelist_item *wh)
306 {
307         struct cgroup *pcg = childcg->css.cgroup->parent;
308         struct dev_cgroup *parent;
309
310         if (!pcg)
311                 return 1;
312         parent = cgroup_to_devcgroup(pcg);
313         return may_access_whitelist(parent, wh);
314 }
315
316 /*
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
324  *
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.
328  */
329 static int devcgroup_update_access(struct dev_cgroup *devcgroup,
330                                    int filetype, const char *buffer)
331 {
332         const char *b;
333         char *endp;
334         int count;
335         struct dev_whitelist_item wh;
336
337         if (!capable(CAP_SYS_ADMIN))
338                 return -EPERM;
339
340         memset(&wh, 0, sizeof(wh));
341         b = buffer;
342
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;
358         }
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;
371         }
372         if (*b != ':')
373                 return -EINVAL;
374         b++;
375
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;
385         }
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;
405                 }
406         }
407
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;
419         }
420         return 0;
421 }
422
423 static int devcgroup_access_write(struct cgroup *cgrp, struct cftype *cft,
424                                   const char *buffer)
425 {
426         int retval;
427
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;
433 }
434
435 static struct cftype dev_cgroup_files[] = {
436         {
437                 .name = "allow",
438                 .write_string  = devcgroup_access_write,
439                 .private = DEVCG_ALLOW,
440         },
441         {
442                 .name = "deny",
443                 .write_string = devcgroup_access_write,
444                 .private = DEVCG_DENY,
445         },
446         {
447                 .name = "list",
448                 .read_seq_string = devcgroup_seq_read,
449                 .private = DEVCG_LIST,
450         },
451 };
452
453 static int devcgroup_populate(struct cgroup_subsys *ss,
454                                 struct cgroup *cgroup)
455 {
456         return cgroup_add_files(cgroup, ss, dev_cgroup_files,
457                                         ARRAY_SIZE(dev_cgroup_files));
458 }
459
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,
467 };
468
469 int __devcgroup_inode_permission(struct inode *inode, int mask)
470 {
471         struct dev_cgroup *dev_cgroup;
472         struct dev_whitelist_item *wh;
473
474         rcu_read_lock();
475
476         dev_cgroup = task_devcgroup(current);
477
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;
489
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;
497         }
498
499         rcu_read_unlock();
500
501         return -EPERM;
502 }
503
504 int devcgroup_inode_mknod(int mode, dev_t dev)
505 {
506         struct dev_cgroup *dev_cgroup;
507         struct dev_whitelist_item *wh;
508
509         if (!S_ISBLK(mode) && !S_ISCHR(mode))
510                 return 0;
511
512         rcu_read_lock();
513
514         dev_cgroup = task_devcgroup(current);
515
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;
527
528                 if (!(wh->access & ACC_MKNOD))
529                         continue;
530 found:
531                 rcu_read_unlock();
532                 return 0;
533         }
534
535         rcu_read_unlock();
536
537         return -EPERM;
538 }