Commit | Line | Data |
---|---|---|
08ce5f16 | 1 | /* |
47c59803 | 2 | * device_cgroup.c - device cgroup subsystem |
08ce5f16 SH |
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> | |
29486df3 | 12 | #include <linux/seq_file.h> |
5a0e3ad6 | 13 | #include <linux/slab.h> |
47c59803 | 14 | #include <linux/rcupdate.h> |
b4046f00 | 15 | #include <linux/mutex.h> |
08ce5f16 SH |
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 | ||
b4046f00 LZ |
26 | static DEFINE_MUTEX(devcgroup_mutex); |
27 | ||
c39a2a30 AR |
28 | enum devcg_behavior { |
29 | DEVCG_DEFAULT_NONE, | |
30 | DEVCG_DEFAULT_ALLOW, | |
31 | DEVCG_DEFAULT_DENY, | |
32 | }; | |
33 | ||
08ce5f16 | 34 | /* |
db9aeca9 | 35 | * exception list locking rules: |
b4046f00 | 36 | * hold devcgroup_mutex for update/read. |
47c59803 | 37 | * hold rcu_read_lock() for read. |
08ce5f16 SH |
38 | */ |
39 | ||
db9aeca9 | 40 | struct dev_exception_item { |
08ce5f16 SH |
41 | u32 major, minor; |
42 | short type; | |
43 | short access; | |
44 | struct list_head list; | |
4efd1a1b | 45 | struct rcu_head rcu; |
08ce5f16 SH |
46 | }; |
47 | ||
48 | struct dev_cgroup { | |
49 | struct cgroup_subsys_state css; | |
db9aeca9 | 50 | struct list_head exceptions; |
c39a2a30 | 51 | enum devcg_behavior behavior; |
08ce5f16 SH |
52 | }; |
53 | ||
b66862f7 PE |
54 | static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s) |
55 | { | |
56 | return container_of(s, struct dev_cgroup, css); | |
57 | } | |
58 | ||
08ce5f16 SH |
59 | static inline struct dev_cgroup *cgroup_to_devcgroup(struct cgroup *cgroup) |
60 | { | |
b66862f7 | 61 | return css_to_devcgroup(cgroup_subsys_state(cgroup, devices_subsys_id)); |
08ce5f16 SH |
62 | } |
63 | ||
f92523e3 PM |
64 | static inline struct dev_cgroup *task_devcgroup(struct task_struct *task) |
65 | { | |
66 | return css_to_devcgroup(task_subsys_state(task, devices_subsys_id)); | |
67 | } | |
68 | ||
08ce5f16 SH |
69 | struct cgroup_subsys devices_subsys; |
70 | ||
761b3ef5 LZ |
71 | static int devcgroup_can_attach(struct cgroup *new_cgrp, |
72 | struct cgroup_taskset *set) | |
08ce5f16 | 73 | { |
2f7ee569 | 74 | struct task_struct *task = cgroup_taskset_first(set); |
08ce5f16 | 75 | |
2f7ee569 TH |
76 | if (current != task && !capable(CAP_SYS_ADMIN)) |
77 | return -EPERM; | |
08ce5f16 SH |
78 | return 0; |
79 | } | |
80 | ||
81 | /* | |
b4046f00 | 82 | * called under devcgroup_mutex |
08ce5f16 | 83 | */ |
db9aeca9 | 84 | static int dev_exceptions_copy(struct list_head *dest, struct list_head *orig) |
08ce5f16 | 85 | { |
db9aeca9 | 86 | struct dev_exception_item *ex, *tmp, *new; |
08ce5f16 | 87 | |
4b1c7840 TH |
88 | lockdep_assert_held(&devcgroup_mutex); |
89 | ||
db9aeca9 AR |
90 | list_for_each_entry(ex, orig, list) { |
91 | new = kmemdup(ex, sizeof(*ex), GFP_KERNEL); | |
08ce5f16 SH |
92 | if (!new) |
93 | goto free_and_exit; | |
08ce5f16 SH |
94 | list_add_tail(&new->list, dest); |
95 | } | |
96 | ||
97 | return 0; | |
98 | ||
99 | free_and_exit: | |
db9aeca9 AR |
100 | list_for_each_entry_safe(ex, tmp, dest, list) { |
101 | list_del(&ex->list); | |
102 | kfree(ex); | |
08ce5f16 SH |
103 | } |
104 | return -ENOMEM; | |
105 | } | |
106 | ||
08ce5f16 | 107 | /* |
b4046f00 | 108 | * called under devcgroup_mutex |
08ce5f16 | 109 | */ |
db9aeca9 AR |
110 | static int dev_exception_add(struct dev_cgroup *dev_cgroup, |
111 | struct dev_exception_item *ex) | |
08ce5f16 | 112 | { |
db9aeca9 | 113 | struct dev_exception_item *excopy, *walk; |
08ce5f16 | 114 | |
4b1c7840 TH |
115 | lockdep_assert_held(&devcgroup_mutex); |
116 | ||
db9aeca9 AR |
117 | excopy = kmemdup(ex, sizeof(*ex), GFP_KERNEL); |
118 | if (!excopy) | |
08ce5f16 SH |
119 | return -ENOMEM; |
120 | ||
db9aeca9 AR |
121 | list_for_each_entry(walk, &dev_cgroup->exceptions, list) { |
122 | if (walk->type != ex->type) | |
d1ee2971 | 123 | continue; |
db9aeca9 | 124 | if (walk->major != ex->major) |
d1ee2971 | 125 | continue; |
db9aeca9 | 126 | if (walk->minor != ex->minor) |
d1ee2971 PE |
127 | continue; |
128 | ||
db9aeca9 AR |
129 | walk->access |= ex->access; |
130 | kfree(excopy); | |
131 | excopy = NULL; | |
d1ee2971 PE |
132 | } |
133 | ||
db9aeca9 AR |
134 | if (excopy != NULL) |
135 | list_add_tail_rcu(&excopy->list, &dev_cgroup->exceptions); | |
08ce5f16 SH |
136 | return 0; |
137 | } | |
138 | ||
139 | /* | |
b4046f00 | 140 | * called under devcgroup_mutex |
08ce5f16 | 141 | */ |
db9aeca9 AR |
142 | static void dev_exception_rm(struct dev_cgroup *dev_cgroup, |
143 | struct dev_exception_item *ex) | |
08ce5f16 | 144 | { |
db9aeca9 | 145 | struct dev_exception_item *walk, *tmp; |
08ce5f16 | 146 | |
4b1c7840 TH |
147 | lockdep_assert_held(&devcgroup_mutex); |
148 | ||
db9aeca9 AR |
149 | list_for_each_entry_safe(walk, tmp, &dev_cgroup->exceptions, list) { |
150 | if (walk->type != ex->type) | |
08ce5f16 | 151 | continue; |
db9aeca9 | 152 | if (walk->major != ex->major) |
08ce5f16 | 153 | continue; |
db9aeca9 | 154 | if (walk->minor != ex->minor) |
08ce5f16 SH |
155 | continue; |
156 | ||
db9aeca9 | 157 | walk->access &= ~ex->access; |
08ce5f16 | 158 | if (!walk->access) { |
4efd1a1b | 159 | list_del_rcu(&walk->list); |
6034f7e6 | 160 | kfree_rcu(walk, rcu); |
08ce5f16 SH |
161 | } |
162 | } | |
08ce5f16 SH |
163 | } |
164 | ||
53eb8c82 JS |
165 | static void __dev_exception_clean(struct dev_cgroup *dev_cgroup) |
166 | { | |
167 | struct dev_exception_item *ex, *tmp; | |
168 | ||
169 | list_for_each_entry_safe(ex, tmp, &dev_cgroup->exceptions, list) { | |
170 | list_del_rcu(&ex->list); | |
171 | kfree_rcu(ex, rcu); | |
172 | } | |
173 | } | |
174 | ||
868539a3 | 175 | /** |
db9aeca9 AR |
176 | * dev_exception_clean - frees all entries of the exception list |
177 | * @dev_cgroup: dev_cgroup with the exception list to be cleaned | |
868539a3 AR |
178 | * |
179 | * called under devcgroup_mutex | |
180 | */ | |
db9aeca9 | 181 | static void dev_exception_clean(struct dev_cgroup *dev_cgroup) |
868539a3 | 182 | { |
4b1c7840 TH |
183 | lockdep_assert_held(&devcgroup_mutex); |
184 | ||
53eb8c82 | 185 | __dev_exception_clean(dev_cgroup); |
868539a3 AR |
186 | } |
187 | ||
bd2953eb AR |
188 | static inline bool is_devcg_online(const struct dev_cgroup *devcg) |
189 | { | |
190 | return (devcg->behavior != DEVCG_DEFAULT_NONE); | |
191 | } | |
192 | ||
1909554c AR |
193 | /** |
194 | * devcgroup_online - initializes devcgroup's behavior and exceptions based on | |
195 | * parent's | |
196 | * @cgroup: cgroup getting online | |
197 | * returns 0 in case of success, error code otherwise | |
198 | */ | |
199 | static int devcgroup_online(struct cgroup *cgroup) | |
200 | { | |
201 | struct dev_cgroup *dev_cgroup, *parent_dev_cgroup = NULL; | |
202 | int ret = 0; | |
203 | ||
204 | mutex_lock(&devcgroup_mutex); | |
205 | dev_cgroup = cgroup_to_devcgroup(cgroup); | |
206 | if (cgroup->parent) | |
207 | parent_dev_cgroup = cgroup_to_devcgroup(cgroup->parent); | |
208 | ||
209 | if (parent_dev_cgroup == NULL) | |
210 | dev_cgroup->behavior = DEVCG_DEFAULT_ALLOW; | |
211 | else { | |
212 | ret = dev_exceptions_copy(&dev_cgroup->exceptions, | |
213 | &parent_dev_cgroup->exceptions); | |
214 | if (!ret) | |
215 | dev_cgroup->behavior = parent_dev_cgroup->behavior; | |
216 | } | |
217 | mutex_unlock(&devcgroup_mutex); | |
218 | ||
219 | return ret; | |
220 | } | |
221 | ||
222 | static void devcgroup_offline(struct cgroup *cgroup) | |
223 | { | |
224 | struct dev_cgroup *dev_cgroup = cgroup_to_devcgroup(cgroup); | |
225 | ||
226 | mutex_lock(&devcgroup_mutex); | |
227 | dev_cgroup->behavior = DEVCG_DEFAULT_NONE; | |
228 | mutex_unlock(&devcgroup_mutex); | |
229 | } | |
230 | ||
08ce5f16 SH |
231 | /* |
232 | * called from kernel/cgroup.c with cgroup_lock() held. | |
233 | */ | |
92fb9748 | 234 | static struct cgroup_subsys_state *devcgroup_css_alloc(struct cgroup *cgroup) |
08ce5f16 | 235 | { |
1909554c | 236 | struct dev_cgroup *dev_cgroup; |
08ce5f16 SH |
237 | |
238 | dev_cgroup = kzalloc(sizeof(*dev_cgroup), GFP_KERNEL); | |
239 | if (!dev_cgroup) | |
240 | return ERR_PTR(-ENOMEM); | |
db9aeca9 | 241 | INIT_LIST_HEAD(&dev_cgroup->exceptions); |
1909554c | 242 | dev_cgroup->behavior = DEVCG_DEFAULT_NONE; |
08ce5f16 | 243 | |
08ce5f16 SH |
244 | return &dev_cgroup->css; |
245 | } | |
246 | ||
92fb9748 | 247 | static void devcgroup_css_free(struct cgroup *cgroup) |
08ce5f16 SH |
248 | { |
249 | struct dev_cgroup *dev_cgroup; | |
08ce5f16 SH |
250 | |
251 | dev_cgroup = cgroup_to_devcgroup(cgroup); | |
53eb8c82 | 252 | __dev_exception_clean(dev_cgroup); |
08ce5f16 SH |
253 | kfree(dev_cgroup); |
254 | } | |
255 | ||
256 | #define DEVCG_ALLOW 1 | |
257 | #define DEVCG_DENY 2 | |
29486df3 SH |
258 | #define DEVCG_LIST 3 |
259 | ||
17d213f8 | 260 | #define MAJMINLEN 13 |
29486df3 | 261 | #define ACCLEN 4 |
08ce5f16 SH |
262 | |
263 | static void set_access(char *acc, short access) | |
264 | { | |
265 | int idx = 0; | |
29486df3 | 266 | memset(acc, 0, ACCLEN); |
08ce5f16 SH |
267 | if (access & ACC_READ) |
268 | acc[idx++] = 'r'; | |
269 | if (access & ACC_WRITE) | |
270 | acc[idx++] = 'w'; | |
271 | if (access & ACC_MKNOD) | |
272 | acc[idx++] = 'm'; | |
273 | } | |
274 | ||
275 | static char type_to_char(short type) | |
276 | { | |
277 | if (type == DEV_ALL) | |
278 | return 'a'; | |
279 | if (type == DEV_CHAR) | |
280 | return 'c'; | |
281 | if (type == DEV_BLOCK) | |
282 | return 'b'; | |
283 | return 'X'; | |
284 | } | |
285 | ||
29486df3 | 286 | static void set_majmin(char *str, unsigned m) |
08ce5f16 | 287 | { |
08ce5f16 | 288 | if (m == ~0) |
7759fc9d | 289 | strcpy(str, "*"); |
08ce5f16 | 290 | else |
7759fc9d | 291 | sprintf(str, "%u", m); |
08ce5f16 SH |
292 | } |
293 | ||
29486df3 SH |
294 | static int devcgroup_seq_read(struct cgroup *cgroup, struct cftype *cft, |
295 | struct seq_file *m) | |
08ce5f16 | 296 | { |
29486df3 | 297 | struct dev_cgroup *devcgroup = cgroup_to_devcgroup(cgroup); |
db9aeca9 | 298 | struct dev_exception_item *ex; |
29486df3 | 299 | char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN]; |
08ce5f16 | 300 | |
4efd1a1b | 301 | rcu_read_lock(); |
ad676077 AR |
302 | /* |
303 | * To preserve the compatibility: | |
304 | * - Only show the "all devices" when the default policy is to allow | |
305 | * - List the exceptions in case the default policy is to deny | |
306 | * This way, the file remains as a "whitelist of devices" | |
307 | */ | |
5b7aa7d5 | 308 | if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) { |
ad676077 AR |
309 | set_access(acc, ACC_MASK); |
310 | set_majmin(maj, ~0); | |
311 | set_majmin(min, ~0); | |
312 | seq_printf(m, "%c %s:%s %s\n", type_to_char(DEV_ALL), | |
29486df3 | 313 | maj, min, acc); |
ad676077 | 314 | } else { |
db9aeca9 AR |
315 | list_for_each_entry_rcu(ex, &devcgroup->exceptions, list) { |
316 | set_access(acc, ex->access); | |
317 | set_majmin(maj, ex->major); | |
318 | set_majmin(min, ex->minor); | |
319 | seq_printf(m, "%c %s:%s %s\n", type_to_char(ex->type), | |
ad676077 AR |
320 | maj, min, acc); |
321 | } | |
08ce5f16 | 322 | } |
4efd1a1b | 323 | rcu_read_unlock(); |
08ce5f16 | 324 | |
29486df3 | 325 | return 0; |
08ce5f16 SH |
326 | } |
327 | ||
ad676077 | 328 | /** |
db9aeca9 AR |
329 | * may_access - verifies if a new exception is part of what is allowed |
330 | * by a dev cgroup based on the default policy + | |
331 | * exceptions. This is used to make sure a child cgroup | |
332 | * won't have more privileges than its parent or to | |
333 | * verify if a certain access is allowed. | |
ad676077 | 334 | * @dev_cgroup: dev cgroup to be tested against |
db9aeca9 | 335 | * @refex: new exception |
c39a2a30 | 336 | * @behavior: behavior of the exception |
08ce5f16 | 337 | */ |
26898fdf | 338 | static bool may_access(struct dev_cgroup *dev_cgroup, |
c39a2a30 AR |
339 | struct dev_exception_item *refex, |
340 | enum devcg_behavior behavior) | |
08ce5f16 | 341 | { |
db9aeca9 | 342 | struct dev_exception_item *ex; |
ad676077 | 343 | bool match = false; |
08ce5f16 | 344 | |
4b1c7840 TH |
345 | rcu_lockdep_assert(rcu_read_lock_held() || |
346 | lockdep_is_held(&devcgroup_mutex), | |
347 | "device_cgroup::may_access() called without proper synchronization"); | |
348 | ||
201e72ac | 349 | list_for_each_entry_rcu(ex, &dev_cgroup->exceptions, list) { |
db9aeca9 | 350 | if ((refex->type & DEV_BLOCK) && !(ex->type & DEV_BLOCK)) |
08ce5f16 | 351 | continue; |
db9aeca9 | 352 | if ((refex->type & DEV_CHAR) && !(ex->type & DEV_CHAR)) |
08ce5f16 | 353 | continue; |
db9aeca9 | 354 | if (ex->major != ~0 && ex->major != refex->major) |
08ce5f16 | 355 | continue; |
db9aeca9 | 356 | if (ex->minor != ~0 && ex->minor != refex->minor) |
08ce5f16 | 357 | continue; |
db9aeca9 | 358 | if (refex->access & (~ex->access)) |
08ce5f16 | 359 | continue; |
ad676077 AR |
360 | match = true; |
361 | break; | |
08ce5f16 | 362 | } |
ad676077 | 363 | |
c39a2a30 AR |
364 | if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) { |
365 | if (behavior == DEVCG_DEFAULT_ALLOW) { | |
366 | /* the exception will deny access to certain devices */ | |
367 | return true; | |
368 | } else { | |
369 | /* the exception will allow access to certain devices */ | |
370 | if (match) | |
371 | /* | |
372 | * a new exception allowing access shouldn't | |
373 | * match an parent's exception | |
374 | */ | |
375 | return false; | |
26898fdf | 376 | return true; |
c39a2a30 | 377 | } |
26898fdf | 378 | } else { |
c39a2a30 AR |
379 | /* only behavior == DEVCG_DEFAULT_DENY allowed here */ |
380 | if (match) | |
381 | /* parent has an exception that matches the proposed */ | |
26898fdf | 382 | return true; |
c39a2a30 AR |
383 | else |
384 | return false; | |
26898fdf AR |
385 | } |
386 | return false; | |
08ce5f16 SH |
387 | } |
388 | ||
389 | /* | |
390 | * parent_has_perm: | |
db9aeca9 | 391 | * when adding a new allow rule to a device exception list, the rule |
08ce5f16 SH |
392 | * must be allowed in the parent device |
393 | */ | |
f92523e3 | 394 | static int parent_has_perm(struct dev_cgroup *childcg, |
db9aeca9 | 395 | struct dev_exception_item *ex) |
08ce5f16 | 396 | { |
f92523e3 | 397 | struct cgroup *pcg = childcg->css.cgroup->parent; |
08ce5f16 | 398 | struct dev_cgroup *parent; |
08ce5f16 SH |
399 | |
400 | if (!pcg) | |
401 | return 1; | |
402 | parent = cgroup_to_devcgroup(pcg); | |
c39a2a30 | 403 | return may_access(parent, ex, childcg->behavior); |
08ce5f16 SH |
404 | } |
405 | ||
4cef7299 AR |
406 | /** |
407 | * may_allow_all - checks if it's possible to change the behavior to | |
408 | * allow based on parent's rules. | |
409 | * @parent: device cgroup's parent | |
410 | * returns: != 0 in case it's allowed, 0 otherwise | |
411 | */ | |
412 | static inline int may_allow_all(struct dev_cgroup *parent) | |
413 | { | |
64e10477 AR |
414 | if (!parent) |
415 | return 1; | |
4cef7299 AR |
416 | return parent->behavior == DEVCG_DEFAULT_ALLOW; |
417 | } | |
418 | ||
bd2953eb AR |
419 | /** |
420 | * revalidate_active_exceptions - walks through the active exception list and | |
421 | * revalidates the exceptions based on parent's | |
422 | * behavior and exceptions. The exceptions that | |
423 | * are no longer valid will be removed. | |
424 | * Called with devcgroup_mutex held. | |
425 | * @devcg: cgroup which exceptions will be checked | |
426 | * | |
427 | * This is one of the three key functions for hierarchy implementation. | |
428 | * This function is responsible for re-evaluating all the cgroup's active | |
429 | * exceptions due to a parent's exception change. | |
430 | * Refer to Documentation/cgroups/devices.txt for more details. | |
431 | */ | |
432 | static void revalidate_active_exceptions(struct dev_cgroup *devcg) | |
433 | { | |
434 | struct dev_exception_item *ex; | |
435 | struct list_head *this, *tmp; | |
436 | ||
437 | list_for_each_safe(this, tmp, &devcg->exceptions) { | |
438 | ex = container_of(this, struct dev_exception_item, list); | |
439 | if (!parent_has_perm(devcg, ex)) | |
440 | dev_exception_rm(devcg, ex); | |
441 | } | |
442 | } | |
443 | ||
bd2953eb AR |
444 | /** |
445 | * propagate_exception - propagates a new exception to the children | |
446 | * @devcg_root: device cgroup that added a new exception | |
447 | * @ex: new exception to be propagated | |
448 | * | |
449 | * returns: 0 in case of success, != 0 in case of error | |
450 | */ | |
451 | static int propagate_exception(struct dev_cgroup *devcg_root, | |
452 | struct dev_exception_item *ex) | |
453 | { | |
d591fb56 | 454 | struct cgroup *root = devcg_root->css.cgroup, *pos; |
bd2953eb | 455 | int rc = 0; |
bd2953eb | 456 | |
d591fb56 | 457 | rcu_read_lock(); |
bd2953eb | 458 | |
d591fb56 TH |
459 | cgroup_for_each_descendant_pre(pos, root) { |
460 | struct dev_cgroup *devcg = cgroup_to_devcgroup(pos); | |
461 | ||
462 | /* | |
463 | * Because devcgroup_mutex is held, no devcg will become | |
464 | * online or offline during the tree walk (see on/offline | |
465 | * methods), and online ones are safe to access outside RCU | |
466 | * read lock without bumping refcnt. | |
467 | */ | |
468 | if (!is_devcg_online(devcg)) | |
469 | continue; | |
470 | ||
471 | rcu_read_unlock(); | |
bd2953eb AR |
472 | |
473 | /* | |
474 | * in case both root's behavior and devcg is allow, a new | |
475 | * restriction means adding to the exception list | |
476 | */ | |
477 | if (devcg_root->behavior == DEVCG_DEFAULT_ALLOW && | |
478 | devcg->behavior == DEVCG_DEFAULT_ALLOW) { | |
479 | rc = dev_exception_add(devcg, ex); | |
480 | if (rc) | |
481 | break; | |
482 | } else { | |
483 | /* | |
484 | * in the other possible cases: | |
485 | * root's behavior: allow, devcg's: deny | |
486 | * root's behavior: deny, devcg's: deny | |
487 | * the exception will be removed | |
488 | */ | |
489 | dev_exception_rm(devcg, ex); | |
490 | } | |
491 | revalidate_active_exceptions(devcg); | |
492 | ||
d591fb56 | 493 | rcu_read_lock(); |
bd2953eb | 494 | } |
d591fb56 TH |
495 | |
496 | rcu_read_unlock(); | |
bd2953eb AR |
497 | return rc; |
498 | } | |
499 | ||
500 | static inline bool has_children(struct dev_cgroup *devcgroup) | |
501 | { | |
502 | struct cgroup *cgrp = devcgroup->css.cgroup; | |
503 | ||
504 | return !list_empty(&cgrp->children); | |
505 | } | |
506 | ||
08ce5f16 | 507 | /* |
db9aeca9 | 508 | * Modify the exception list using allow/deny rules. |
08ce5f16 SH |
509 | * CAP_SYS_ADMIN is needed for this. It's at least separate from CAP_MKNOD |
510 | * so we can give a container CAP_MKNOD to let it create devices but not | |
db9aeca9 | 511 | * modify the exception list. |
08ce5f16 SH |
512 | * It seems likely we'll want to add a CAP_CONTAINER capability to allow |
513 | * us to also grant CAP_SYS_ADMIN to containers without giving away the | |
db9aeca9 | 514 | * device exception list controls, but for now we'll stick with CAP_SYS_ADMIN |
08ce5f16 SH |
515 | * |
516 | * Taking rules away is always allowed (given CAP_SYS_ADMIN). Granting | |
517 | * new access is only allowed if you're in the top-level cgroup, or your | |
518 | * parent cgroup has the access you're asking for. | |
519 | */ | |
f92523e3 PM |
520 | static int devcgroup_update_access(struct dev_cgroup *devcgroup, |
521 | int filetype, const char *buffer) | |
08ce5f16 | 522 | { |
f92523e3 | 523 | const char *b; |
26fd8405 | 524 | char temp[12]; /* 11 + 1 characters needed for a u32 */ |
c39a2a30 | 525 | int count, rc = 0; |
db9aeca9 | 526 | struct dev_exception_item ex; |
4cef7299 | 527 | struct cgroup *p = devcgroup->css.cgroup; |
64e10477 | 528 | struct dev_cgroup *parent = NULL; |
08ce5f16 SH |
529 | |
530 | if (!capable(CAP_SYS_ADMIN)) | |
531 | return -EPERM; | |
532 | ||
64e10477 AR |
533 | if (p->parent) |
534 | parent = cgroup_to_devcgroup(p->parent); | |
535 | ||
db9aeca9 | 536 | memset(&ex, 0, sizeof(ex)); |
08ce5f16 SH |
537 | b = buffer; |
538 | ||
539 | switch (*b) { | |
540 | case 'a': | |
ad676077 AR |
541 | switch (filetype) { |
542 | case DEVCG_ALLOW: | |
bd2953eb AR |
543 | if (has_children(devcgroup)) |
544 | return -EINVAL; | |
545 | ||
4cef7299 | 546 | if (!may_allow_all(parent)) |
ad676077 | 547 | return -EPERM; |
db9aeca9 | 548 | dev_exception_clean(devcgroup); |
64e10477 AR |
549 | devcgroup->behavior = DEVCG_DEFAULT_ALLOW; |
550 | if (!parent) | |
551 | break; | |
552 | ||
4cef7299 AR |
553 | rc = dev_exceptions_copy(&devcgroup->exceptions, |
554 | &parent->exceptions); | |
555 | if (rc) | |
556 | return rc; | |
ad676077 AR |
557 | break; |
558 | case DEVCG_DENY: | |
bd2953eb AR |
559 | if (has_children(devcgroup)) |
560 | return -EINVAL; | |
561 | ||
db9aeca9 | 562 | dev_exception_clean(devcgroup); |
5b7aa7d5 | 563 | devcgroup->behavior = DEVCG_DEFAULT_DENY; |
ad676077 AR |
564 | break; |
565 | default: | |
566 | return -EINVAL; | |
567 | } | |
568 | return 0; | |
08ce5f16 | 569 | case 'b': |
db9aeca9 | 570 | ex.type = DEV_BLOCK; |
08ce5f16 SH |
571 | break; |
572 | case 'c': | |
db9aeca9 | 573 | ex.type = DEV_CHAR; |
08ce5f16 SH |
574 | break; |
575 | default: | |
f92523e3 | 576 | return -EINVAL; |
08ce5f16 SH |
577 | } |
578 | b++; | |
f92523e3 PM |
579 | if (!isspace(*b)) |
580 | return -EINVAL; | |
08ce5f16 SH |
581 | b++; |
582 | if (*b == '*') { | |
db9aeca9 | 583 | ex.major = ~0; |
08ce5f16 SH |
584 | b++; |
585 | } else if (isdigit(*b)) { | |
26fd8405 AR |
586 | memset(temp, 0, sizeof(temp)); |
587 | for (count = 0; count < sizeof(temp) - 1; count++) { | |
588 | temp[count] = *b; | |
589 | b++; | |
590 | if (!isdigit(*b)) | |
591 | break; | |
592 | } | |
593 | rc = kstrtou32(temp, 10, &ex.major); | |
594 | if (rc) | |
595 | return -EINVAL; | |
08ce5f16 | 596 | } else { |
f92523e3 | 597 | return -EINVAL; |
08ce5f16 | 598 | } |
f92523e3 PM |
599 | if (*b != ':') |
600 | return -EINVAL; | |
08ce5f16 SH |
601 | b++; |
602 | ||
603 | /* read minor */ | |
604 | if (*b == '*') { | |
db9aeca9 | 605 | ex.minor = ~0; |
08ce5f16 SH |
606 | b++; |
607 | } else if (isdigit(*b)) { | |
26fd8405 AR |
608 | memset(temp, 0, sizeof(temp)); |
609 | for (count = 0; count < sizeof(temp) - 1; count++) { | |
610 | temp[count] = *b; | |
611 | b++; | |
612 | if (!isdigit(*b)) | |
613 | break; | |
614 | } | |
615 | rc = kstrtou32(temp, 10, &ex.minor); | |
616 | if (rc) | |
617 | return -EINVAL; | |
08ce5f16 | 618 | } else { |
f92523e3 | 619 | return -EINVAL; |
08ce5f16 | 620 | } |
f92523e3 PM |
621 | if (!isspace(*b)) |
622 | return -EINVAL; | |
08ce5f16 SH |
623 | for (b++, count = 0; count < 3; count++, b++) { |
624 | switch (*b) { | |
625 | case 'r': | |
db9aeca9 | 626 | ex.access |= ACC_READ; |
08ce5f16 SH |
627 | break; |
628 | case 'w': | |
db9aeca9 | 629 | ex.access |= ACC_WRITE; |
08ce5f16 SH |
630 | break; |
631 | case 'm': | |
db9aeca9 | 632 | ex.access |= ACC_MKNOD; |
08ce5f16 SH |
633 | break; |
634 | case '\n': | |
635 | case '\0': | |
636 | count = 3; | |
637 | break; | |
638 | default: | |
f92523e3 | 639 | return -EINVAL; |
08ce5f16 SH |
640 | } |
641 | } | |
642 | ||
08ce5f16 SH |
643 | switch (filetype) { |
644 | case DEVCG_ALLOW: | |
db9aeca9 | 645 | if (!parent_has_perm(devcgroup, &ex)) |
f92523e3 | 646 | return -EPERM; |
ad676077 AR |
647 | /* |
648 | * If the default policy is to allow by default, try to remove | |
649 | * an matching exception instead. And be silent about it: we | |
650 | * don't want to break compatibility | |
651 | */ | |
5b7aa7d5 | 652 | if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) { |
db9aeca9 | 653 | dev_exception_rm(devcgroup, &ex); |
ad676077 AR |
654 | return 0; |
655 | } | |
bd2953eb AR |
656 | rc = dev_exception_add(devcgroup, &ex); |
657 | break; | |
08ce5f16 | 658 | case DEVCG_DENY: |
ad676077 AR |
659 | /* |
660 | * If the default policy is to deny by default, try to remove | |
661 | * an matching exception instead. And be silent about it: we | |
662 | * don't want to break compatibility | |
663 | */ | |
bd2953eb | 664 | if (devcgroup->behavior == DEVCG_DEFAULT_DENY) |
db9aeca9 | 665 | dev_exception_rm(devcgroup, &ex); |
bd2953eb AR |
666 | else |
667 | rc = dev_exception_add(devcgroup, &ex); | |
668 | ||
669 | if (rc) | |
670 | break; | |
671 | /* we only propagate new restrictions */ | |
672 | rc = propagate_exception(devcgroup, &ex); | |
673 | break; | |
08ce5f16 | 674 | default: |
bd2953eb | 675 | rc = -EINVAL; |
08ce5f16 | 676 | } |
bd2953eb | 677 | return rc; |
f92523e3 | 678 | } |
08ce5f16 | 679 | |
f92523e3 PM |
680 | static int devcgroup_access_write(struct cgroup *cgrp, struct cftype *cft, |
681 | const char *buffer) | |
682 | { | |
683 | int retval; | |
b4046f00 LZ |
684 | |
685 | mutex_lock(&devcgroup_mutex); | |
f92523e3 PM |
686 | retval = devcgroup_update_access(cgroup_to_devcgroup(cgrp), |
687 | cft->private, buffer); | |
b4046f00 | 688 | mutex_unlock(&devcgroup_mutex); |
08ce5f16 SH |
689 | return retval; |
690 | } | |
691 | ||
692 | static struct cftype dev_cgroup_files[] = { | |
693 | { | |
694 | .name = "allow", | |
f92523e3 | 695 | .write_string = devcgroup_access_write, |
08ce5f16 SH |
696 | .private = DEVCG_ALLOW, |
697 | }, | |
698 | { | |
699 | .name = "deny", | |
f92523e3 | 700 | .write_string = devcgroup_access_write, |
08ce5f16 SH |
701 | .private = DEVCG_DENY, |
702 | }, | |
29486df3 SH |
703 | { |
704 | .name = "list", | |
705 | .read_seq_string = devcgroup_seq_read, | |
706 | .private = DEVCG_LIST, | |
707 | }, | |
4baf6e33 | 708 | { } /* terminate */ |
08ce5f16 SH |
709 | }; |
710 | ||
08ce5f16 SH |
711 | struct cgroup_subsys devices_subsys = { |
712 | .name = "devices", | |
713 | .can_attach = devcgroup_can_attach, | |
92fb9748 TH |
714 | .css_alloc = devcgroup_css_alloc, |
715 | .css_free = devcgroup_css_free, | |
1909554c AR |
716 | .css_online = devcgroup_online, |
717 | .css_offline = devcgroup_offline, | |
08ce5f16 | 718 | .subsys_id = devices_subsys_id, |
4baf6e33 | 719 | .base_cftypes = dev_cgroup_files, |
08ce5f16 SH |
720 | }; |
721 | ||
ad676077 AR |
722 | /** |
723 | * __devcgroup_check_permission - checks if an inode operation is permitted | |
724 | * @dev_cgroup: the dev cgroup to be tested against | |
725 | * @type: device type | |
726 | * @major: device major number | |
727 | * @minor: device minor number | |
728 | * @access: combination of ACC_WRITE, ACC_READ and ACC_MKNOD | |
729 | * | |
730 | * returns 0 on success, -EPERM case the operation is not permitted | |
731 | */ | |
8c9506d1 | 732 | static int __devcgroup_check_permission(short type, u32 major, u32 minor, |
ad676077 | 733 | short access) |
08ce5f16 | 734 | { |
8c9506d1 | 735 | struct dev_cgroup *dev_cgroup; |
db9aeca9 | 736 | struct dev_exception_item ex; |
ad676077 | 737 | int rc; |
36fd71d2 | 738 | |
db9aeca9 AR |
739 | memset(&ex, 0, sizeof(ex)); |
740 | ex.type = type; | |
741 | ex.major = major; | |
742 | ex.minor = minor; | |
743 | ex.access = access; | |
36fd71d2 | 744 | |
ad676077 | 745 | rcu_read_lock(); |
8c9506d1 | 746 | dev_cgroup = task_devcgroup(current); |
c39a2a30 | 747 | rc = may_access(dev_cgroup, &ex, dev_cgroup->behavior); |
ad676077 | 748 | rcu_read_unlock(); |
cd500819 | 749 | |
ad676077 AR |
750 | if (!rc) |
751 | return -EPERM; | |
36fd71d2 | 752 | |
ad676077 AR |
753 | return 0; |
754 | } | |
08ce5f16 | 755 | |
ad676077 AR |
756 | int __devcgroup_inode_permission(struct inode *inode, int mask) |
757 | { | |
ad676077 AR |
758 | short type, access = 0; |
759 | ||
760 | if (S_ISBLK(inode->i_mode)) | |
761 | type = DEV_BLOCK; | |
762 | if (S_ISCHR(inode->i_mode)) | |
763 | type = DEV_CHAR; | |
764 | if (mask & MAY_WRITE) | |
765 | access |= ACC_WRITE; | |
766 | if (mask & MAY_READ) | |
767 | access |= ACC_READ; | |
768 | ||
8c9506d1 JS |
769 | return __devcgroup_check_permission(type, imajor(inode), iminor(inode), |
770 | access); | |
08ce5f16 SH |
771 | } |
772 | ||
773 | int devcgroup_inode_mknod(int mode, dev_t dev) | |
774 | { | |
ad676077 | 775 | short type; |
08ce5f16 | 776 | |
0b82ac37 SH |
777 | if (!S_ISBLK(mode) && !S_ISCHR(mode)) |
778 | return 0; | |
779 | ||
ad676077 AR |
780 | if (S_ISBLK(mode)) |
781 | type = DEV_BLOCK; | |
782 | else | |
783 | type = DEV_CHAR; | |
36fd71d2 | 784 | |
8c9506d1 JS |
785 | return __devcgroup_check_permission(type, MAJOR(dev), MINOR(dev), |
786 | ACC_MKNOD); | |
36fd71d2 | 787 | |
08ce5f16 | 788 | } |