SMACK: smack_file_lock can use the struct path
[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                 bool threadgroup)
67 {
68         if (current != task && !capable(CAP_SYS_ADMIN))
69                         return -EPERM;
70
71         return 0;
72 }
73
74 /*
75  * called under devcgroup_mutex
76  */
77 static int dev_whitelist_copy(struct list_head *dest, struct list_head *orig)
78 {
79         struct dev_whitelist_item *wh, *tmp, *new;
80
81         list_for_each_entry(wh, orig, list) {
82                 new = kmemdup(wh, sizeof(*wh), GFP_KERNEL);
83                 if (!new)
84                         goto free_and_exit;
85                 list_add_tail(&new->list, dest);
86         }
87
88         return 0;
89
90 free_and_exit:
91         list_for_each_entry_safe(wh, tmp, dest, list) {
92                 list_del(&wh->list);
93                 kfree(wh);
94         }
95         return -ENOMEM;
96 }
97
98 /* Stupid prototype - don't bother combining existing entries */
99 /*
100  * called under devcgroup_mutex
101  */
102 static int dev_whitelist_add(struct dev_cgroup *dev_cgroup,
103                         struct dev_whitelist_item *wh)
104 {
105         struct dev_whitelist_item *whcopy, *walk;
106
107         whcopy = kmemdup(wh, sizeof(*wh), GFP_KERNEL);
108         if (!whcopy)
109                 return -ENOMEM;
110
111         list_for_each_entry(walk, &dev_cgroup->whitelist, list) {
112                 if (walk->type != wh->type)
113                         continue;
114                 if (walk->major != wh->major)
115                         continue;
116                 if (walk->minor != wh->minor)
117                         continue;
118
119                 walk->access |= wh->access;
120                 kfree(whcopy);
121                 whcopy = NULL;
122         }
123
124         if (whcopy != NULL)
125                 list_add_tail_rcu(&whcopy->list, &dev_cgroup->whitelist);
126         return 0;
127 }
128
129 static void whitelist_item_free(struct rcu_head *rcu)
130 {
131         struct dev_whitelist_item *item;
132
133         item = container_of(rcu, struct dev_whitelist_item, rcu);
134         kfree(item);
135 }
136
137 /*
138  * called under devcgroup_mutex
139  */
140 static 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         list_for_each_entry_safe(walk, tmp, &dev_cgroup->whitelist, list) {
146                 if (walk->type == DEV_ALL)
147                         goto remove;
148                 if (walk->type != wh->type)
149                         continue;
150                 if (walk->major != ~0 && walk->major != wh->major)
151                         continue;
152                 if (walk->minor != ~0 && walk->minor != wh->minor)
153                         continue;
154
155 remove:
156                 walk->access &= ~wh->access;
157                 if (!walk->access) {
158                         list_del_rcu(&walk->list);
159                         call_rcu(&walk->rcu, whitelist_item_free);
160                 }
161         }
162 }
163
164 /*
165  * called from kernel/cgroup.c with cgroup_lock() held.
166  */
167 static struct cgroup_subsys_state *devcgroup_create(struct cgroup_subsys *ss,
168                                                 struct cgroup *cgroup)
169 {
170         struct dev_cgroup *dev_cgroup, *parent_dev_cgroup;
171         struct cgroup *parent_cgroup;
172         int ret;
173
174         dev_cgroup = kzalloc(sizeof(*dev_cgroup), GFP_KERNEL);
175         if (!dev_cgroup)
176                 return ERR_PTR(-ENOMEM);
177         INIT_LIST_HEAD(&dev_cgroup->whitelist);
178         parent_cgroup = cgroup->parent;
179
180         if (parent_cgroup == NULL) {
181                 struct dev_whitelist_item *wh;
182                 wh = kmalloc(sizeof(*wh), GFP_KERNEL);
183                 if (!wh) {
184                         kfree(dev_cgroup);
185                         return ERR_PTR(-ENOMEM);
186                 }
187                 wh->minor = wh->major = ~0;
188                 wh->type = DEV_ALL;
189                 wh->access = ACC_MASK;
190                 list_add(&wh->list, &dev_cgroup->whitelist);
191         } else {
192                 parent_dev_cgroup = cgroup_to_devcgroup(parent_cgroup);
193                 mutex_lock(&devcgroup_mutex);
194                 ret = dev_whitelist_copy(&dev_cgroup->whitelist,
195                                 &parent_dev_cgroup->whitelist);
196                 mutex_unlock(&devcgroup_mutex);
197                 if (ret) {
198                         kfree(dev_cgroup);
199                         return ERR_PTR(ret);
200                 }
201         }
202
203         return &dev_cgroup->css;
204 }
205
206 static void devcgroup_destroy(struct cgroup_subsys *ss,
207                         struct cgroup *cgroup)
208 {
209         struct dev_cgroup *dev_cgroup;
210         struct dev_whitelist_item *wh, *tmp;
211
212         dev_cgroup = cgroup_to_devcgroup(cgroup);
213         list_for_each_entry_safe(wh, tmp, &dev_cgroup->whitelist, list) {
214                 list_del(&wh->list);
215                 kfree(wh);
216         }
217         kfree(dev_cgroup);
218 }
219
220 #define DEVCG_ALLOW 1
221 #define DEVCG_DENY 2
222 #define DEVCG_LIST 3
223
224 #define MAJMINLEN 13
225 #define ACCLEN 4
226
227 static void set_access(char *acc, short access)
228 {
229         int idx = 0;
230         memset(acc, 0, ACCLEN);
231         if (access & ACC_READ)
232                 acc[idx++] = 'r';
233         if (access & ACC_WRITE)
234                 acc[idx++] = 'w';
235         if (access & ACC_MKNOD)
236                 acc[idx++] = 'm';
237 }
238
239 static char type_to_char(short type)
240 {
241         if (type == DEV_ALL)
242                 return 'a';
243         if (type == DEV_CHAR)
244                 return 'c';
245         if (type == DEV_BLOCK)
246                 return 'b';
247         return 'X';
248 }
249
250 static void set_majmin(char *str, unsigned m)
251 {
252         if (m == ~0)
253                 strcpy(str, "*");
254         else
255                 sprintf(str, "%u", m);
256 }
257
258 static int devcgroup_seq_read(struct cgroup *cgroup, struct cftype *cft,
259                                 struct seq_file *m)
260 {
261         struct dev_cgroup *devcgroup = cgroup_to_devcgroup(cgroup);
262         struct dev_whitelist_item *wh;
263         char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN];
264
265         rcu_read_lock();
266         list_for_each_entry_rcu(wh, &devcgroup->whitelist, list) {
267                 set_access(acc, wh->access);
268                 set_majmin(maj, wh->major);
269                 set_majmin(min, wh->minor);
270                 seq_printf(m, "%c %s:%s %s\n", type_to_char(wh->type),
271                            maj, min, acc);
272         }
273         rcu_read_unlock();
274
275         return 0;
276 }
277
278 /*
279  * may_access_whitelist:
280  * does the access granted to dev_cgroup c contain the access
281  * requested in whitelist item refwh.
282  * return 1 if yes, 0 if no.
283  * call with devcgroup_mutex held
284  */
285 static int may_access_whitelist(struct dev_cgroup *c,
286                                        struct dev_whitelist_item *refwh)
287 {
288         struct dev_whitelist_item *whitem;
289
290         list_for_each_entry(whitem, &c->whitelist, list) {
291                 if (whitem->type & DEV_ALL)
292                         return 1;
293                 if ((refwh->type & DEV_BLOCK) && !(whitem->type & DEV_BLOCK))
294                         continue;
295                 if ((refwh->type & DEV_CHAR) && !(whitem->type & DEV_CHAR))
296                         continue;
297                 if (whitem->major != ~0 && whitem->major != refwh->major)
298                         continue;
299                 if (whitem->minor != ~0 && whitem->minor != refwh->minor)
300                         continue;
301                 if (refwh->access & (~whitem->access))
302                         continue;
303                 return 1;
304         }
305         return 0;
306 }
307
308 /*
309  * parent_has_perm:
310  * when adding a new allow rule to a device whitelist, the rule
311  * must be allowed in the parent device
312  */
313 static int parent_has_perm(struct dev_cgroup *childcg,
314                                   struct dev_whitelist_item *wh)
315 {
316         struct cgroup *pcg = childcg->css.cgroup->parent;
317         struct dev_cgroup *parent;
318
319         if (!pcg)
320                 return 1;
321         parent = cgroup_to_devcgroup(pcg);
322         return may_access_whitelist(parent, wh);
323 }
324
325 /*
326  * Modify the whitelist using allow/deny rules.
327  * CAP_SYS_ADMIN is needed for this.  It's at least separate from CAP_MKNOD
328  * so we can give a container CAP_MKNOD to let it create devices but not
329  * modify the whitelist.
330  * It seems likely we'll want to add a CAP_CONTAINER capability to allow
331  * us to also grant CAP_SYS_ADMIN to containers without giving away the
332  * device whitelist controls, but for now we'll stick with CAP_SYS_ADMIN
333  *
334  * Taking rules away is always allowed (given CAP_SYS_ADMIN).  Granting
335  * new access is only allowed if you're in the top-level cgroup, or your
336  * parent cgroup has the access you're asking for.
337  */
338 static int devcgroup_update_access(struct dev_cgroup *devcgroup,
339                                    int filetype, const char *buffer)
340 {
341         const char *b;
342         char *endp;
343         int count;
344         struct dev_whitelist_item wh;
345
346         if (!capable(CAP_SYS_ADMIN))
347                 return -EPERM;
348
349         memset(&wh, 0, sizeof(wh));
350         b = buffer;
351
352         switch (*b) {
353         case 'a':
354                 wh.type = DEV_ALL;
355                 wh.access = ACC_MASK;
356                 wh.major = ~0;
357                 wh.minor = ~0;
358                 goto handle;
359         case 'b':
360                 wh.type = DEV_BLOCK;
361                 break;
362         case 'c':
363                 wh.type = DEV_CHAR;
364                 break;
365         default:
366                 return -EINVAL;
367         }
368         b++;
369         if (!isspace(*b))
370                 return -EINVAL;
371         b++;
372         if (*b == '*') {
373                 wh.major = ~0;
374                 b++;
375         } else if (isdigit(*b)) {
376                 wh.major = simple_strtoul(b, &endp, 10);
377                 b = endp;
378         } else {
379                 return -EINVAL;
380         }
381         if (*b != ':')
382                 return -EINVAL;
383         b++;
384
385         /* read minor */
386         if (*b == '*') {
387                 wh.minor = ~0;
388                 b++;
389         } else if (isdigit(*b)) {
390                 wh.minor = simple_strtoul(b, &endp, 10);
391                 b = endp;
392         } else {
393                 return -EINVAL;
394         }
395         if (!isspace(*b))
396                 return -EINVAL;
397         for (b++, count = 0; count < 3; count++, b++) {
398                 switch (*b) {
399                 case 'r':
400                         wh.access |= ACC_READ;
401                         break;
402                 case 'w':
403                         wh.access |= ACC_WRITE;
404                         break;
405                 case 'm':
406                         wh.access |= ACC_MKNOD;
407                         break;
408                 case '\n':
409                 case '\0':
410                         count = 3;
411                         break;
412                 default:
413                         return -EINVAL;
414                 }
415         }
416
417 handle:
418         switch (filetype) {
419         case DEVCG_ALLOW:
420                 if (!parent_has_perm(devcgroup, &wh))
421                         return -EPERM;
422                 return dev_whitelist_add(devcgroup, &wh);
423         case DEVCG_DENY:
424                 dev_whitelist_rm(devcgroup, &wh);
425                 break;
426         default:
427                 return -EINVAL;
428         }
429         return 0;
430 }
431
432 static int devcgroup_access_write(struct cgroup *cgrp, struct cftype *cft,
433                                   const char *buffer)
434 {
435         int retval;
436
437         mutex_lock(&devcgroup_mutex);
438         retval = devcgroup_update_access(cgroup_to_devcgroup(cgrp),
439                                          cft->private, buffer);
440         mutex_unlock(&devcgroup_mutex);
441         return retval;
442 }
443
444 static struct cftype dev_cgroup_files[] = {
445         {
446                 .name = "allow",
447                 .write_string  = devcgroup_access_write,
448                 .private = DEVCG_ALLOW,
449         },
450         {
451                 .name = "deny",
452                 .write_string = devcgroup_access_write,
453                 .private = DEVCG_DENY,
454         },
455         {
456                 .name = "list",
457                 .read_seq_string = devcgroup_seq_read,
458                 .private = DEVCG_LIST,
459         },
460 };
461
462 static int devcgroup_populate(struct cgroup_subsys *ss,
463                                 struct cgroup *cgroup)
464 {
465         return cgroup_add_files(cgroup, ss, dev_cgroup_files,
466                                         ARRAY_SIZE(dev_cgroup_files));
467 }
468
469 struct cgroup_subsys devices_subsys = {
470         .name = "devices",
471         .can_attach = devcgroup_can_attach,
472         .create = devcgroup_create,
473         .destroy = devcgroup_destroy,
474         .populate = devcgroup_populate,
475         .subsys_id = devices_subsys_id,
476 };
477
478 int devcgroup_inode_permission(struct inode *inode, int mask)
479 {
480         struct dev_cgroup *dev_cgroup;
481         struct dev_whitelist_item *wh;
482
483         dev_t device = inode->i_rdev;
484         if (!device)
485                 return 0;
486         if (!S_ISBLK(inode->i_mode) && !S_ISCHR(inode->i_mode))
487                 return 0;
488
489         rcu_read_lock();
490
491         dev_cgroup = task_devcgroup(current);
492
493         list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) {
494                 if (wh->type & DEV_ALL)
495                         goto found;
496                 if ((wh->type & DEV_BLOCK) && !S_ISBLK(inode->i_mode))
497                         continue;
498                 if ((wh->type & DEV_CHAR) && !S_ISCHR(inode->i_mode))
499                         continue;
500                 if (wh->major != ~0 && wh->major != imajor(inode))
501                         continue;
502                 if (wh->minor != ~0 && wh->minor != iminor(inode))
503                         continue;
504
505                 if ((mask & MAY_WRITE) && !(wh->access & ACC_WRITE))
506                         continue;
507                 if ((mask & MAY_READ) && !(wh->access & ACC_READ))
508                         continue;
509 found:
510                 rcu_read_unlock();
511                 return 0;
512         }
513
514         rcu_read_unlock();
515
516         return -EPERM;
517 }
518
519 int devcgroup_inode_mknod(int mode, dev_t dev)
520 {
521         struct dev_cgroup *dev_cgroup;
522         struct dev_whitelist_item *wh;
523
524         if (!S_ISBLK(mode) && !S_ISCHR(mode))
525                 return 0;
526
527         rcu_read_lock();
528
529         dev_cgroup = task_devcgroup(current);
530
531         list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) {
532                 if (wh->type & DEV_ALL)
533                         goto found;
534                 if ((wh->type & DEV_BLOCK) && !S_ISBLK(mode))
535                         continue;
536                 if ((wh->type & DEV_CHAR) && !S_ISCHR(mode))
537                         continue;
538                 if (wh->major != ~0 && wh->major != MAJOR(dev))
539                         continue;
540                 if (wh->minor != ~0 && wh->minor != MINOR(dev))
541                         continue;
542
543                 if (!(wh->access & ACC_MKNOD))
544                         continue;
545 found:
546                 rcu_read_unlock();
547                 return 0;
548         }
549
550         rcu_read_unlock();
551
552         return -EPERM;
553 }