sysctl security/tomoyo: Don't look at ctl_name
[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/rcupdate.h>
14 #include <linux/mutex.h>
15
16 #define ACC_MKNOD 1
17 #define ACC_READ  2
18 #define ACC_WRITE 4
19 #define ACC_MASK (ACC_MKNOD | ACC_READ | ACC_WRITE)
20
21 #define DEV_BLOCK 1
22 #define DEV_CHAR  2
23 #define DEV_ALL   4  /* this represents all devices */
24
25 static DEFINE_MUTEX(devcgroup_mutex);
26
27 /*
28  * whitelist locking rules:
29  * hold devcgroup_mutex for update/read.
30  * hold rcu_read_lock() for read.
31  */
32
33 struct dev_whitelist_item {
34         u32 major, minor;
35         short type;
36         short access;
37         struct list_head list;
38         struct rcu_head rcu;
39 };
40
41 struct dev_cgroup {
42         struct cgroup_subsys_state css;
43         struct list_head whitelist;
44 };
45
46 static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s)
47 {
48         return container_of(s, struct dev_cgroup, css);
49 }
50
51 static inline struct dev_cgroup *cgroup_to_devcgroup(struct cgroup *cgroup)
52 {
53         return css_to_devcgroup(cgroup_subsys_state(cgroup, devices_subsys_id));
54 }
55
56 static inline struct dev_cgroup *task_devcgroup(struct task_struct *task)
57 {
58         return css_to_devcgroup(task_subsys_state(task, devices_subsys_id));
59 }
60
61 struct cgroup_subsys devices_subsys;
62
63 static int devcgroup_can_attach(struct cgroup_subsys *ss,
64                 struct cgroup *new_cgroup, struct task_struct *task,
65                 bool threadgroup)
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 static 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  */
139 static 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
154 remove:
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  */
166 static 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
205 static 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
226 static 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
238 static 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
249 static void set_majmin(char *str, unsigned m)
250 {
251         if (m == ~0)
252                 strcpy(str, "*");
253         else
254                 sprintf(str, "%u", m);
255 }
256
257 static 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  */
284 static 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  */
312 static 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  */
337 static 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
416 handle:
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
431 static 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
443 static 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
461 static 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
468 struct 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
477 int devcgroup_inode_permission(struct inode *inode, int mask)
478 {
479         struct dev_cgroup *dev_cgroup;
480         struct dev_whitelist_item *wh;
481
482         dev_t device = inode->i_rdev;
483         if (!device)
484                 return 0;
485         if (!S_ISBLK(inode->i_mode) && !S_ISCHR(inode->i_mode))
486                 return 0;
487
488         rcu_read_lock();
489
490         dev_cgroup = task_devcgroup(current);
491
492         list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) {
493                 if (wh->type & DEV_ALL)
494                         goto found;
495                 if ((wh->type & DEV_BLOCK) && !S_ISBLK(inode->i_mode))
496                         continue;
497                 if ((wh->type & DEV_CHAR) && !S_ISCHR(inode->i_mode))
498                         continue;
499                 if (wh->major != ~0 && wh->major != imajor(inode))
500                         continue;
501                 if (wh->minor != ~0 && wh->minor != iminor(inode))
502                         continue;
503
504                 if ((mask & MAY_WRITE) && !(wh->access & ACC_WRITE))
505                         continue;
506                 if ((mask & MAY_READ) && !(wh->access & ACC_READ))
507                         continue;
508 found:
509                 rcu_read_unlock();
510                 return 0;
511         }
512
513         rcu_read_unlock();
514
515         return -EPERM;
516 }
517
518 int devcgroup_inode_mknod(int mode, dev_t dev)
519 {
520         struct dev_cgroup *dev_cgroup;
521         struct dev_whitelist_item *wh;
522
523         if (!S_ISBLK(mode) && !S_ISCHR(mode))
524                 return 0;
525
526         rcu_read_lock();
527
528         dev_cgroup = task_devcgroup(current);
529
530         list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) {
531                 if (wh->type & DEV_ALL)
532                         goto found;
533                 if ((wh->type & DEV_BLOCK) && !S_ISBLK(mode))
534                         continue;
535                 if ((wh->type & DEV_CHAR) && !S_ISCHR(mode))
536                         continue;
537                 if (wh->major != ~0 && wh->major != MAJOR(dev))
538                         continue;
539                 if (wh->minor != ~0 && wh->minor != MINOR(dev))
540                         continue;
541
542                 if (!(wh->access & ACC_MKNOD))
543                         continue;
544 found:
545                 rcu_read_unlock();
546                 return 0;
547         }
548
549         rcu_read_unlock();
550
551         return -EPERM;
552 }