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