Merge commit 'v3.4.2' into android-tegra-nv-3.4
[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 *new_cgrp,
65                                 struct cgroup_taskset *set)
66 {
67         struct task_struct *task = cgroup_taskset_first(set);
68
69         if (current != task && !capable(CAP_SYS_ADMIN))
70                 return -EPERM;
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 /*
130  * called under devcgroup_mutex
131  */
132 static void dev_whitelist_rm(struct dev_cgroup *dev_cgroup,
133                         struct dev_whitelist_item *wh)
134 {
135         struct dev_whitelist_item *walk, *tmp;
136
137         list_for_each_entry_safe(walk, tmp, &dev_cgroup->whitelist, list) {
138                 if (walk->type == DEV_ALL)
139                         goto remove;
140                 if (walk->type != wh->type)
141                         continue;
142                 if (walk->major != ~0 && walk->major != wh->major)
143                         continue;
144                 if (walk->minor != ~0 && walk->minor != wh->minor)
145                         continue;
146
147 remove:
148                 walk->access &= ~wh->access;
149                 if (!walk->access) {
150                         list_del_rcu(&walk->list);
151                         kfree_rcu(walk, rcu);
152                 }
153         }
154 }
155
156 /*
157  * called from kernel/cgroup.c with cgroup_lock() held.
158  */
159 static struct cgroup_subsys_state *devcgroup_create(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 *cgroup)
198 {
199         struct dev_cgroup *dev_cgroup;
200         struct dev_whitelist_item *wh, *tmp;
201
202         dev_cgroup = cgroup_to_devcgroup(cgroup);
203         list_for_each_entry_safe(wh, tmp, &dev_cgroup->whitelist, list) {
204                 list_del(&wh->list);
205                 kfree(wh);
206         }
207         kfree(dev_cgroup);
208 }
209
210 #define DEVCG_ALLOW 1
211 #define DEVCG_DENY 2
212 #define DEVCG_LIST 3
213
214 #define MAJMINLEN 13
215 #define ACCLEN 4
216
217 static void set_access(char *acc, short access)
218 {
219         int idx = 0;
220         memset(acc, 0, ACCLEN);
221         if (access & ACC_READ)
222                 acc[idx++] = 'r';
223         if (access & ACC_WRITE)
224                 acc[idx++] = 'w';
225         if (access & ACC_MKNOD)
226                 acc[idx++] = 'm';
227 }
228
229 static char type_to_char(short type)
230 {
231         if (type == DEV_ALL)
232                 return 'a';
233         if (type == DEV_CHAR)
234                 return 'c';
235         if (type == DEV_BLOCK)
236                 return 'b';
237         return 'X';
238 }
239
240 static void set_majmin(char *str, unsigned m)
241 {
242         if (m == ~0)
243                 strcpy(str, "*");
244         else
245                 sprintf(str, "%u", m);
246 }
247
248 static int devcgroup_seq_read(struct cgroup *cgroup, struct cftype *cft,
249                                 struct seq_file *m)
250 {
251         struct dev_cgroup *devcgroup = cgroup_to_devcgroup(cgroup);
252         struct dev_whitelist_item *wh;
253         char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN];
254
255         rcu_read_lock();
256         list_for_each_entry_rcu(wh, &devcgroup->whitelist, list) {
257                 set_access(acc, wh->access);
258                 set_majmin(maj, wh->major);
259                 set_majmin(min, wh->minor);
260                 seq_printf(m, "%c %s:%s %s\n", type_to_char(wh->type),
261                            maj, min, acc);
262         }
263         rcu_read_unlock();
264
265         return 0;
266 }
267
268 /*
269  * may_access_whitelist:
270  * does the access granted to dev_cgroup c contain the access
271  * requested in whitelist item refwh.
272  * return 1 if yes, 0 if no.
273  * call with devcgroup_mutex held
274  */
275 static int may_access_whitelist(struct dev_cgroup *c,
276                                        struct dev_whitelist_item *refwh)
277 {
278         struct dev_whitelist_item *whitem;
279
280         list_for_each_entry(whitem, &c->whitelist, list) {
281                 if (whitem->type & DEV_ALL)
282                         return 1;
283                 if ((refwh->type & DEV_BLOCK) && !(whitem->type & DEV_BLOCK))
284                         continue;
285                 if ((refwh->type & DEV_CHAR) && !(whitem->type & DEV_CHAR))
286                         continue;
287                 if (whitem->major != ~0 && whitem->major != refwh->major)
288                         continue;
289                 if (whitem->minor != ~0 && whitem->minor != refwh->minor)
290                         continue;
291                 if (refwh->access & (~whitem->access))
292                         continue;
293                 return 1;
294         }
295         return 0;
296 }
297
298 /*
299  * parent_has_perm:
300  * when adding a new allow rule to a device whitelist, the rule
301  * must be allowed in the parent device
302  */
303 static int parent_has_perm(struct dev_cgroup *childcg,
304                                   struct dev_whitelist_item *wh)
305 {
306         struct cgroup *pcg = childcg->css.cgroup->parent;
307         struct dev_cgroup *parent;
308
309         if (!pcg)
310                 return 1;
311         parent = cgroup_to_devcgroup(pcg);
312         return may_access_whitelist(parent, wh);
313 }
314
315 /*
316  * Modify the whitelist using allow/deny rules.
317  * CAP_SYS_ADMIN is needed for this.  It's at least separate from CAP_MKNOD
318  * so we can give a container CAP_MKNOD to let it create devices but not
319  * modify the whitelist.
320  * It seems likely we'll want to add a CAP_CONTAINER capability to allow
321  * us to also grant CAP_SYS_ADMIN to containers without giving away the
322  * device whitelist controls, but for now we'll stick with CAP_SYS_ADMIN
323  *
324  * Taking rules away is always allowed (given CAP_SYS_ADMIN).  Granting
325  * new access is only allowed if you're in the top-level cgroup, or your
326  * parent cgroup has the access you're asking for.
327  */
328 static int devcgroup_update_access(struct dev_cgroup *devcgroup,
329                                    int filetype, const char *buffer)
330 {
331         const char *b;
332         char *endp;
333         int count;
334         struct dev_whitelist_item wh;
335
336         if (!capable(CAP_SYS_ADMIN))
337                 return -EPERM;
338
339         memset(&wh, 0, sizeof(wh));
340         b = buffer;
341
342         switch (*b) {
343         case 'a':
344                 wh.type = DEV_ALL;
345                 wh.access = ACC_MASK;
346                 wh.major = ~0;
347                 wh.minor = ~0;
348                 goto handle;
349         case 'b':
350                 wh.type = DEV_BLOCK;
351                 break;
352         case 'c':
353                 wh.type = DEV_CHAR;
354                 break;
355         default:
356                 return -EINVAL;
357         }
358         b++;
359         if (!isspace(*b))
360                 return -EINVAL;
361         b++;
362         if (*b == '*') {
363                 wh.major = ~0;
364                 b++;
365         } else if (isdigit(*b)) {
366                 wh.major = simple_strtoul(b, &endp, 10);
367                 b = endp;
368         } else {
369                 return -EINVAL;
370         }
371         if (*b != ':')
372                 return -EINVAL;
373         b++;
374
375         /* read minor */
376         if (*b == '*') {
377                 wh.minor = ~0;
378                 b++;
379         } else if (isdigit(*b)) {
380                 wh.minor = simple_strtoul(b, &endp, 10);
381                 b = endp;
382         } else {
383                 return -EINVAL;
384         }
385         if (!isspace(*b))
386                 return -EINVAL;
387         for (b++, count = 0; count < 3; count++, b++) {
388                 switch (*b) {
389                 case 'r':
390                         wh.access |= ACC_READ;
391                         break;
392                 case 'w':
393                         wh.access |= ACC_WRITE;
394                         break;
395                 case 'm':
396                         wh.access |= ACC_MKNOD;
397                         break;
398                 case '\n':
399                 case '\0':
400                         count = 3;
401                         break;
402                 default:
403                         return -EINVAL;
404                 }
405         }
406
407 handle:
408         switch (filetype) {
409         case DEVCG_ALLOW:
410                 if (!parent_has_perm(devcgroup, &wh))
411                         return -EPERM;
412                 return dev_whitelist_add(devcgroup, &wh);
413         case DEVCG_DENY:
414                 dev_whitelist_rm(devcgroup, &wh);
415                 break;
416         default:
417                 return -EINVAL;
418         }
419         return 0;
420 }
421
422 static int devcgroup_access_write(struct cgroup *cgrp, struct cftype *cft,
423                                   const char *buffer)
424 {
425         int retval;
426
427         mutex_lock(&devcgroup_mutex);
428         retval = devcgroup_update_access(cgroup_to_devcgroup(cgrp),
429                                          cft->private, buffer);
430         mutex_unlock(&devcgroup_mutex);
431         return retval;
432 }
433
434 static struct cftype dev_cgroup_files[] = {
435         {
436                 .name = "allow",
437                 .write_string  = devcgroup_access_write,
438                 .private = DEVCG_ALLOW,
439         },
440         {
441                 .name = "deny",
442                 .write_string = devcgroup_access_write,
443                 .private = DEVCG_DENY,
444         },
445         {
446                 .name = "list",
447                 .read_seq_string = devcgroup_seq_read,
448                 .private = DEVCG_LIST,
449         },
450 };
451
452 static int devcgroup_populate(struct cgroup_subsys *ss,
453                                 struct cgroup *cgroup)
454 {
455         return cgroup_add_files(cgroup, ss, dev_cgroup_files,
456                                         ARRAY_SIZE(dev_cgroup_files));
457 }
458
459 struct cgroup_subsys devices_subsys = {
460         .name = "devices",
461         .can_attach = devcgroup_can_attach,
462         .create = devcgroup_create,
463         .destroy = devcgroup_destroy,
464         .populate = devcgroup_populate,
465         .subsys_id = devices_subsys_id,
466 };
467
468 int __devcgroup_inode_permission(struct inode *inode, int mask)
469 {
470         struct dev_cgroup *dev_cgroup;
471         struct dev_whitelist_item *wh;
472
473         rcu_read_lock();
474
475         dev_cgroup = task_devcgroup(current);
476
477         list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) {
478                 if (wh->type & DEV_ALL)
479                         goto found;
480                 if ((wh->type & DEV_BLOCK) && !S_ISBLK(inode->i_mode))
481                         continue;
482                 if ((wh->type & DEV_CHAR) && !S_ISCHR(inode->i_mode))
483                         continue;
484                 if (wh->major != ~0 && wh->major != imajor(inode))
485                         continue;
486                 if (wh->minor != ~0 && wh->minor != iminor(inode))
487                         continue;
488
489                 if ((mask & MAY_WRITE) && !(wh->access & ACC_WRITE))
490                         continue;
491                 if ((mask & MAY_READ) && !(wh->access & ACC_READ))
492                         continue;
493 found:
494                 rcu_read_unlock();
495                 return 0;
496         }
497
498         rcu_read_unlock();
499
500         return -EPERM;
501 }
502
503 int devcgroup_inode_mknod(int mode, dev_t dev)
504 {
505         struct dev_cgroup *dev_cgroup;
506         struct dev_whitelist_item *wh;
507
508         if (!S_ISBLK(mode) && !S_ISCHR(mode))
509                 return 0;
510
511         rcu_read_lock();
512
513         dev_cgroup = task_devcgroup(current);
514
515         list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) {
516                 if (wh->type & DEV_ALL)
517                         goto found;
518                 if ((wh->type & DEV_BLOCK) && !S_ISBLK(mode))
519                         continue;
520                 if ((wh->type & DEV_CHAR) && !S_ISCHR(mode))
521                         continue;
522                 if (wh->major != ~0 && wh->major != MAJOR(dev))
523                         continue;
524                 if (wh->minor != ~0 && wh->minor != MINOR(dev))
525                         continue;
526
527                 if (!(wh->access & ACC_MKNOD))
528                         continue;
529 found:
530                 rcu_read_unlock();
531                 return 0;
532         }
533
534         rcu_read_unlock();
535
536         return -EPERM;
537 }