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; |
bd2953eb AR |
52 | /* temporary list for pending propagation operations */ |
53 | struct list_head propagate_pending; | |
08ce5f16 SH |
54 | }; |
55 | ||
b66862f7 PE |
56 | static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s) |
57 | { | |
58 | return container_of(s, struct dev_cgroup, css); | |
59 | } | |
60 | ||
08ce5f16 SH |
61 | static inline struct dev_cgroup *cgroup_to_devcgroup(struct cgroup *cgroup) |
62 | { | |
b66862f7 | 63 | return css_to_devcgroup(cgroup_subsys_state(cgroup, devices_subsys_id)); |
08ce5f16 SH |
64 | } |
65 | ||
f92523e3 PM |
66 | static inline struct dev_cgroup *task_devcgroup(struct task_struct *task) |
67 | { | |
68 | return css_to_devcgroup(task_subsys_state(task, devices_subsys_id)); | |
69 | } | |
70 | ||
08ce5f16 SH |
71 | struct cgroup_subsys devices_subsys; |
72 | ||
761b3ef5 LZ |
73 | static int devcgroup_can_attach(struct cgroup *new_cgrp, |
74 | struct cgroup_taskset *set) | |
08ce5f16 | 75 | { |
2f7ee569 | 76 | struct task_struct *task = cgroup_taskset_first(set); |
08ce5f16 | 77 | |
2f7ee569 TH |
78 | if (current != task && !capable(CAP_SYS_ADMIN)) |
79 | return -EPERM; | |
08ce5f16 SH |
80 | return 0; |
81 | } | |
82 | ||
83 | /* | |
b4046f00 | 84 | * called under devcgroup_mutex |
08ce5f16 | 85 | */ |
db9aeca9 | 86 | static int dev_exceptions_copy(struct list_head *dest, struct list_head *orig) |
08ce5f16 | 87 | { |
db9aeca9 | 88 | struct dev_exception_item *ex, *tmp, *new; |
08ce5f16 | 89 | |
4b1c7840 TH |
90 | lockdep_assert_held(&devcgroup_mutex); |
91 | ||
db9aeca9 AR |
92 | list_for_each_entry(ex, orig, list) { |
93 | new = kmemdup(ex, sizeof(*ex), GFP_KERNEL); | |
08ce5f16 SH |
94 | if (!new) |
95 | goto free_and_exit; | |
08ce5f16 SH |
96 | list_add_tail(&new->list, dest); |
97 | } | |
98 | ||
99 | return 0; | |
100 | ||
101 | free_and_exit: | |
db9aeca9 AR |
102 | list_for_each_entry_safe(ex, tmp, dest, list) { |
103 | list_del(&ex->list); | |
104 | kfree(ex); | |
08ce5f16 SH |
105 | } |
106 | return -ENOMEM; | |
107 | } | |
108 | ||
08ce5f16 | 109 | /* |
b4046f00 | 110 | * called under devcgroup_mutex |
08ce5f16 | 111 | */ |
db9aeca9 AR |
112 | static int dev_exception_add(struct dev_cgroup *dev_cgroup, |
113 | struct dev_exception_item *ex) | |
08ce5f16 | 114 | { |
db9aeca9 | 115 | struct dev_exception_item *excopy, *walk; |
08ce5f16 | 116 | |
4b1c7840 TH |
117 | lockdep_assert_held(&devcgroup_mutex); |
118 | ||
db9aeca9 AR |
119 | excopy = kmemdup(ex, sizeof(*ex), GFP_KERNEL); |
120 | if (!excopy) | |
08ce5f16 SH |
121 | return -ENOMEM; |
122 | ||
db9aeca9 AR |
123 | list_for_each_entry(walk, &dev_cgroup->exceptions, list) { |
124 | if (walk->type != ex->type) | |
d1ee2971 | 125 | continue; |
db9aeca9 | 126 | if (walk->major != ex->major) |
d1ee2971 | 127 | continue; |
db9aeca9 | 128 | if (walk->minor != ex->minor) |
d1ee2971 PE |
129 | continue; |
130 | ||
db9aeca9 AR |
131 | walk->access |= ex->access; |
132 | kfree(excopy); | |
133 | excopy = NULL; | |
d1ee2971 PE |
134 | } |
135 | ||
db9aeca9 AR |
136 | if (excopy != NULL) |
137 | list_add_tail_rcu(&excopy->list, &dev_cgroup->exceptions); | |
08ce5f16 SH |
138 | return 0; |
139 | } | |
140 | ||
141 | /* | |
b4046f00 | 142 | * called under devcgroup_mutex |
08ce5f16 | 143 | */ |
db9aeca9 AR |
144 | static void dev_exception_rm(struct dev_cgroup *dev_cgroup, |
145 | struct dev_exception_item *ex) | |
08ce5f16 | 146 | { |
db9aeca9 | 147 | struct dev_exception_item *walk, *tmp; |
08ce5f16 | 148 | |
4b1c7840 TH |
149 | lockdep_assert_held(&devcgroup_mutex); |
150 | ||
db9aeca9 AR |
151 | list_for_each_entry_safe(walk, tmp, &dev_cgroup->exceptions, list) { |
152 | if (walk->type != ex->type) | |
08ce5f16 | 153 | continue; |
db9aeca9 | 154 | if (walk->major != ex->major) |
08ce5f16 | 155 | continue; |
db9aeca9 | 156 | if (walk->minor != ex->minor) |
08ce5f16 SH |
157 | continue; |
158 | ||
db9aeca9 | 159 | walk->access &= ~ex->access; |
08ce5f16 | 160 | if (!walk->access) { |
4efd1a1b | 161 | list_del_rcu(&walk->list); |
6034f7e6 | 162 | kfree_rcu(walk, rcu); |
08ce5f16 SH |
163 | } |
164 | } | |
08ce5f16 SH |
165 | } |
166 | ||
53eb8c82 JS |
167 | static void __dev_exception_clean(struct dev_cgroup *dev_cgroup) |
168 | { | |
169 | struct dev_exception_item *ex, *tmp; | |
170 | ||
171 | list_for_each_entry_safe(ex, tmp, &dev_cgroup->exceptions, list) { | |
172 | list_del_rcu(&ex->list); | |
173 | kfree_rcu(ex, rcu); | |
174 | } | |
175 | } | |
176 | ||
868539a3 | 177 | /** |
db9aeca9 AR |
178 | * dev_exception_clean - frees all entries of the exception list |
179 | * @dev_cgroup: dev_cgroup with the exception list to be cleaned | |
868539a3 AR |
180 | * |
181 | * called under devcgroup_mutex | |
182 | */ | |
db9aeca9 | 183 | static void dev_exception_clean(struct dev_cgroup *dev_cgroup) |
868539a3 | 184 | { |
4b1c7840 TH |
185 | lockdep_assert_held(&devcgroup_mutex); |
186 | ||
53eb8c82 | 187 | __dev_exception_clean(dev_cgroup); |
868539a3 AR |
188 | } |
189 | ||
bd2953eb AR |
190 | static inline bool is_devcg_online(const struct dev_cgroup *devcg) |
191 | { | |
192 | return (devcg->behavior != DEVCG_DEFAULT_NONE); | |
193 | } | |
194 | ||
1909554c AR |
195 | /** |
196 | * devcgroup_online - initializes devcgroup's behavior and exceptions based on | |
197 | * parent's | |
198 | * @cgroup: cgroup getting online | |
199 | * returns 0 in case of success, error code otherwise | |
200 | */ | |
201 | static int devcgroup_online(struct cgroup *cgroup) | |
202 | { | |
203 | struct dev_cgroup *dev_cgroup, *parent_dev_cgroup = NULL; | |
204 | int ret = 0; | |
205 | ||
206 | mutex_lock(&devcgroup_mutex); | |
207 | dev_cgroup = cgroup_to_devcgroup(cgroup); | |
208 | if (cgroup->parent) | |
209 | parent_dev_cgroup = cgroup_to_devcgroup(cgroup->parent); | |
210 | ||
211 | if (parent_dev_cgroup == NULL) | |
212 | dev_cgroup->behavior = DEVCG_DEFAULT_ALLOW; | |
213 | else { | |
214 | ret = dev_exceptions_copy(&dev_cgroup->exceptions, | |
215 | &parent_dev_cgroup->exceptions); | |
216 | if (!ret) | |
217 | dev_cgroup->behavior = parent_dev_cgroup->behavior; | |
218 | } | |
219 | mutex_unlock(&devcgroup_mutex); | |
220 | ||
221 | return ret; | |
222 | } | |
223 | ||
224 | static void devcgroup_offline(struct cgroup *cgroup) | |
225 | { | |
226 | struct dev_cgroup *dev_cgroup = cgroup_to_devcgroup(cgroup); | |
227 | ||
228 | mutex_lock(&devcgroup_mutex); | |
229 | dev_cgroup->behavior = DEVCG_DEFAULT_NONE; | |
230 | mutex_unlock(&devcgroup_mutex); | |
231 | } | |
232 | ||
08ce5f16 SH |
233 | /* |
234 | * called from kernel/cgroup.c with cgroup_lock() held. | |
235 | */ | |
92fb9748 | 236 | static struct cgroup_subsys_state *devcgroup_css_alloc(struct cgroup *cgroup) |
08ce5f16 | 237 | { |
1909554c | 238 | struct dev_cgroup *dev_cgroup; |
08ce5f16 SH |
239 | |
240 | dev_cgroup = kzalloc(sizeof(*dev_cgroup), GFP_KERNEL); | |
241 | if (!dev_cgroup) | |
242 | return ERR_PTR(-ENOMEM); | |
db9aeca9 | 243 | INIT_LIST_HEAD(&dev_cgroup->exceptions); |
bd2953eb | 244 | INIT_LIST_HEAD(&dev_cgroup->propagate_pending); |
1909554c | 245 | dev_cgroup->behavior = DEVCG_DEFAULT_NONE; |
08ce5f16 | 246 | |
08ce5f16 SH |
247 | return &dev_cgroup->css; |
248 | } | |
249 | ||
92fb9748 | 250 | static void devcgroup_css_free(struct cgroup *cgroup) |
08ce5f16 SH |
251 | { |
252 | struct dev_cgroup *dev_cgroup; | |
08ce5f16 SH |
253 | |
254 | dev_cgroup = cgroup_to_devcgroup(cgroup); | |
53eb8c82 | 255 | __dev_exception_clean(dev_cgroup); |
08ce5f16 SH |
256 | kfree(dev_cgroup); |
257 | } | |
258 | ||
259 | #define DEVCG_ALLOW 1 | |
260 | #define DEVCG_DENY 2 | |
29486df3 SH |
261 | #define DEVCG_LIST 3 |
262 | ||
17d213f8 | 263 | #define MAJMINLEN 13 |
29486df3 | 264 | #define ACCLEN 4 |
08ce5f16 SH |
265 | |
266 | static void set_access(char *acc, short access) | |
267 | { | |
268 | int idx = 0; | |
29486df3 | 269 | memset(acc, 0, ACCLEN); |
08ce5f16 SH |
270 | if (access & ACC_READ) |
271 | acc[idx++] = 'r'; | |
272 | if (access & ACC_WRITE) | |
273 | acc[idx++] = 'w'; | |
274 | if (access & ACC_MKNOD) | |
275 | acc[idx++] = 'm'; | |
276 | } | |
277 | ||
278 | static char type_to_char(short type) | |
279 | { | |
280 | if (type == DEV_ALL) | |
281 | return 'a'; | |
282 | if (type == DEV_CHAR) | |
283 | return 'c'; | |
284 | if (type == DEV_BLOCK) | |
285 | return 'b'; | |
286 | return 'X'; | |
287 | } | |
288 | ||
29486df3 | 289 | static void set_majmin(char *str, unsigned m) |
08ce5f16 | 290 | { |
08ce5f16 | 291 | if (m == ~0) |
7759fc9d | 292 | strcpy(str, "*"); |
08ce5f16 | 293 | else |
7759fc9d | 294 | sprintf(str, "%u", m); |
08ce5f16 SH |
295 | } |
296 | ||
29486df3 SH |
297 | static int devcgroup_seq_read(struct cgroup *cgroup, struct cftype *cft, |
298 | struct seq_file *m) | |
08ce5f16 | 299 | { |
29486df3 | 300 | struct dev_cgroup *devcgroup = cgroup_to_devcgroup(cgroup); |
db9aeca9 | 301 | struct dev_exception_item *ex; |
29486df3 | 302 | char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN]; |
08ce5f16 | 303 | |
4efd1a1b | 304 | rcu_read_lock(); |
ad676077 AR |
305 | /* |
306 | * To preserve the compatibility: | |
307 | * - Only show the "all devices" when the default policy is to allow | |
308 | * - List the exceptions in case the default policy is to deny | |
309 | * This way, the file remains as a "whitelist of devices" | |
310 | */ | |
5b7aa7d5 | 311 | if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) { |
ad676077 AR |
312 | set_access(acc, ACC_MASK); |
313 | set_majmin(maj, ~0); | |
314 | set_majmin(min, ~0); | |
315 | seq_printf(m, "%c %s:%s %s\n", type_to_char(DEV_ALL), | |
29486df3 | 316 | maj, min, acc); |
ad676077 | 317 | } else { |
db9aeca9 AR |
318 | list_for_each_entry_rcu(ex, &devcgroup->exceptions, list) { |
319 | set_access(acc, ex->access); | |
320 | set_majmin(maj, ex->major); | |
321 | set_majmin(min, ex->minor); | |
322 | seq_printf(m, "%c %s:%s %s\n", type_to_char(ex->type), | |
ad676077 AR |
323 | maj, min, acc); |
324 | } | |
08ce5f16 | 325 | } |
4efd1a1b | 326 | rcu_read_unlock(); |
08ce5f16 | 327 | |
29486df3 | 328 | return 0; |
08ce5f16 SH |
329 | } |
330 | ||
ad676077 | 331 | /** |
db9aeca9 AR |
332 | * may_access - verifies if a new exception is part of what is allowed |
333 | * by a dev cgroup based on the default policy + | |
334 | * exceptions. This is used to make sure a child cgroup | |
335 | * won't have more privileges than its parent or to | |
336 | * verify if a certain access is allowed. | |
ad676077 | 337 | * @dev_cgroup: dev cgroup to be tested against |
db9aeca9 | 338 | * @refex: new exception |
c39a2a30 | 339 | * @behavior: behavior of the exception |
08ce5f16 | 340 | */ |
26898fdf | 341 | static bool may_access(struct dev_cgroup *dev_cgroup, |
c39a2a30 AR |
342 | struct dev_exception_item *refex, |
343 | enum devcg_behavior behavior) | |
08ce5f16 | 344 | { |
db9aeca9 | 345 | struct dev_exception_item *ex; |
ad676077 | 346 | bool match = false; |
08ce5f16 | 347 | |
4b1c7840 TH |
348 | rcu_lockdep_assert(rcu_read_lock_held() || |
349 | lockdep_is_held(&devcgroup_mutex), | |
350 | "device_cgroup::may_access() called without proper synchronization"); | |
351 | ||
201e72ac | 352 | list_for_each_entry_rcu(ex, &dev_cgroup->exceptions, list) { |
db9aeca9 | 353 | if ((refex->type & DEV_BLOCK) && !(ex->type & DEV_BLOCK)) |
08ce5f16 | 354 | continue; |
db9aeca9 | 355 | if ((refex->type & DEV_CHAR) && !(ex->type & DEV_CHAR)) |
08ce5f16 | 356 | continue; |
db9aeca9 | 357 | if (ex->major != ~0 && ex->major != refex->major) |
08ce5f16 | 358 | continue; |
db9aeca9 | 359 | if (ex->minor != ~0 && ex->minor != refex->minor) |
08ce5f16 | 360 | continue; |
db9aeca9 | 361 | if (refex->access & (~ex->access)) |
08ce5f16 | 362 | continue; |
ad676077 AR |
363 | match = true; |
364 | break; | |
08ce5f16 | 365 | } |
ad676077 | 366 | |
c39a2a30 AR |
367 | if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) { |
368 | if (behavior == DEVCG_DEFAULT_ALLOW) { | |
369 | /* the exception will deny access to certain devices */ | |
370 | return true; | |
371 | } else { | |
372 | /* the exception will allow access to certain devices */ | |
373 | if (match) | |
374 | /* | |
375 | * a new exception allowing access shouldn't | |
376 | * match an parent's exception | |
377 | */ | |
378 | return false; | |
26898fdf | 379 | return true; |
c39a2a30 | 380 | } |
26898fdf | 381 | } else { |
c39a2a30 AR |
382 | /* only behavior == DEVCG_DEFAULT_DENY allowed here */ |
383 | if (match) | |
384 | /* parent has an exception that matches the proposed */ | |
26898fdf | 385 | return true; |
c39a2a30 AR |
386 | else |
387 | return false; | |
26898fdf AR |
388 | } |
389 | return false; | |
08ce5f16 SH |
390 | } |
391 | ||
392 | /* | |
393 | * parent_has_perm: | |
db9aeca9 | 394 | * when adding a new allow rule to a device exception list, the rule |
08ce5f16 SH |
395 | * must be allowed in the parent device |
396 | */ | |
f92523e3 | 397 | static int parent_has_perm(struct dev_cgroup *childcg, |
db9aeca9 | 398 | struct dev_exception_item *ex) |
08ce5f16 | 399 | { |
f92523e3 | 400 | struct cgroup *pcg = childcg->css.cgroup->parent; |
08ce5f16 | 401 | struct dev_cgroup *parent; |
08ce5f16 SH |
402 | |
403 | if (!pcg) | |
404 | return 1; | |
405 | parent = cgroup_to_devcgroup(pcg); | |
c39a2a30 | 406 | return may_access(parent, ex, childcg->behavior); |
08ce5f16 SH |
407 | } |
408 | ||
4cef7299 AR |
409 | /** |
410 | * may_allow_all - checks if it's possible to change the behavior to | |
411 | * allow based on parent's rules. | |
412 | * @parent: device cgroup's parent | |
413 | * returns: != 0 in case it's allowed, 0 otherwise | |
414 | */ | |
415 | static inline int may_allow_all(struct dev_cgroup *parent) | |
416 | { | |
64e10477 AR |
417 | if (!parent) |
418 | return 1; | |
4cef7299 AR |
419 | return parent->behavior == DEVCG_DEFAULT_ALLOW; |
420 | } | |
421 | ||
bd2953eb AR |
422 | /** |
423 | * revalidate_active_exceptions - walks through the active exception list and | |
424 | * revalidates the exceptions based on parent's | |
425 | * behavior and exceptions. The exceptions that | |
426 | * are no longer valid will be removed. | |
427 | * Called with devcgroup_mutex held. | |
428 | * @devcg: cgroup which exceptions will be checked | |
429 | * | |
430 | * This is one of the three key functions for hierarchy implementation. | |
431 | * This function is responsible for re-evaluating all the cgroup's active | |
432 | * exceptions due to a parent's exception change. | |
433 | * Refer to Documentation/cgroups/devices.txt for more details. | |
434 | */ | |
435 | static void revalidate_active_exceptions(struct dev_cgroup *devcg) | |
436 | { | |
437 | struct dev_exception_item *ex; | |
438 | struct list_head *this, *tmp; | |
439 | ||
440 | list_for_each_safe(this, tmp, &devcg->exceptions) { | |
441 | ex = container_of(this, struct dev_exception_item, list); | |
442 | if (!parent_has_perm(devcg, ex)) | |
443 | dev_exception_rm(devcg, ex); | |
444 | } | |
445 | } | |
446 | ||
447 | /** | |
448 | * get_online_devcg - walks the cgroup tree and fills a list with the online | |
449 | * groups | |
450 | * @root: cgroup used as starting point | |
451 | * @online: list that will be filled with online groups | |
452 | * | |
453 | * Must be called with devcgroup_mutex held. Grabs RCU lock. | |
454 | * Because devcgroup_mutex is held, no devcg will become online or offline | |
455 | * during the tree walk (see devcgroup_online, devcgroup_offline) | |
456 | * A separated list is needed because propagate_behavior() and | |
457 | * propagate_exception() need to allocate memory and can block. | |
458 | */ | |
459 | static void get_online_devcg(struct cgroup *root, struct list_head *online) | |
460 | { | |
461 | struct cgroup *pos; | |
462 | struct dev_cgroup *devcg; | |
463 | ||
464 | lockdep_assert_held(&devcgroup_mutex); | |
465 | ||
466 | rcu_read_lock(); | |
467 | cgroup_for_each_descendant_pre(pos, root) { | |
468 | devcg = cgroup_to_devcgroup(pos); | |
469 | if (is_devcg_online(devcg)) | |
470 | list_add_tail(&devcg->propagate_pending, online); | |
471 | } | |
472 | rcu_read_unlock(); | |
473 | } | |
474 | ||
475 | /** | |
476 | * propagate_exception - propagates a new exception to the children | |
477 | * @devcg_root: device cgroup that added a new exception | |
478 | * @ex: new exception to be propagated | |
479 | * | |
480 | * returns: 0 in case of success, != 0 in case of error | |
481 | */ | |
482 | static int propagate_exception(struct dev_cgroup *devcg_root, | |
483 | struct dev_exception_item *ex) | |
484 | { | |
485 | struct cgroup *root = devcg_root->css.cgroup; | |
486 | struct dev_cgroup *devcg, *parent, *tmp; | |
487 | int rc = 0; | |
488 | LIST_HEAD(pending); | |
489 | ||
490 | get_online_devcg(root, &pending); | |
491 | ||
492 | list_for_each_entry_safe(devcg, tmp, &pending, propagate_pending) { | |
493 | parent = cgroup_to_devcgroup(devcg->css.cgroup->parent); | |
494 | ||
495 | /* | |
496 | * in case both root's behavior and devcg is allow, a new | |
497 | * restriction means adding to the exception list | |
498 | */ | |
499 | if (devcg_root->behavior == DEVCG_DEFAULT_ALLOW && | |
500 | devcg->behavior == DEVCG_DEFAULT_ALLOW) { | |
501 | rc = dev_exception_add(devcg, ex); | |
502 | if (rc) | |
503 | break; | |
504 | } else { | |
505 | /* | |
506 | * in the other possible cases: | |
507 | * root's behavior: allow, devcg's: deny | |
508 | * root's behavior: deny, devcg's: deny | |
509 | * the exception will be removed | |
510 | */ | |
511 | dev_exception_rm(devcg, ex); | |
512 | } | |
513 | revalidate_active_exceptions(devcg); | |
514 | ||
515 | list_del_init(&devcg->propagate_pending); | |
516 | } | |
517 | return rc; | |
518 | } | |
519 | ||
520 | static inline bool has_children(struct dev_cgroup *devcgroup) | |
521 | { | |
522 | struct cgroup *cgrp = devcgroup->css.cgroup; | |
523 | ||
524 | return !list_empty(&cgrp->children); | |
525 | } | |
526 | ||
08ce5f16 | 527 | /* |
db9aeca9 | 528 | * Modify the exception list using allow/deny rules. |
08ce5f16 SH |
529 | * CAP_SYS_ADMIN is needed for this. It's at least separate from CAP_MKNOD |
530 | * so we can give a container CAP_MKNOD to let it create devices but not | |
db9aeca9 | 531 | * modify the exception list. |
08ce5f16 SH |
532 | * It seems likely we'll want to add a CAP_CONTAINER capability to allow |
533 | * us to also grant CAP_SYS_ADMIN to containers without giving away the | |
db9aeca9 | 534 | * device exception list controls, but for now we'll stick with CAP_SYS_ADMIN |
08ce5f16 SH |
535 | * |
536 | * Taking rules away is always allowed (given CAP_SYS_ADMIN). Granting | |
537 | * new access is only allowed if you're in the top-level cgroup, or your | |
538 | * parent cgroup has the access you're asking for. | |
539 | */ | |
f92523e3 PM |
540 | static int devcgroup_update_access(struct dev_cgroup *devcgroup, |
541 | int filetype, const char *buffer) | |
08ce5f16 | 542 | { |
f92523e3 | 543 | const char *b; |
26fd8405 | 544 | char temp[12]; /* 11 + 1 characters needed for a u32 */ |
c39a2a30 | 545 | int count, rc = 0; |
db9aeca9 | 546 | struct dev_exception_item ex; |
4cef7299 | 547 | struct cgroup *p = devcgroup->css.cgroup; |
64e10477 | 548 | struct dev_cgroup *parent = NULL; |
08ce5f16 SH |
549 | |
550 | if (!capable(CAP_SYS_ADMIN)) | |
551 | return -EPERM; | |
552 | ||
64e10477 AR |
553 | if (p->parent) |
554 | parent = cgroup_to_devcgroup(p->parent); | |
555 | ||
db9aeca9 | 556 | memset(&ex, 0, sizeof(ex)); |
08ce5f16 SH |
557 | b = buffer; |
558 | ||
559 | switch (*b) { | |
560 | case 'a': | |
ad676077 AR |
561 | switch (filetype) { |
562 | case DEVCG_ALLOW: | |
bd2953eb AR |
563 | if (has_children(devcgroup)) |
564 | return -EINVAL; | |
565 | ||
4cef7299 | 566 | if (!may_allow_all(parent)) |
ad676077 | 567 | return -EPERM; |
db9aeca9 | 568 | dev_exception_clean(devcgroup); |
64e10477 AR |
569 | devcgroup->behavior = DEVCG_DEFAULT_ALLOW; |
570 | if (!parent) | |
571 | break; | |
572 | ||
4cef7299 AR |
573 | rc = dev_exceptions_copy(&devcgroup->exceptions, |
574 | &parent->exceptions); | |
575 | if (rc) | |
576 | return rc; | |
ad676077 AR |
577 | break; |
578 | case DEVCG_DENY: | |
bd2953eb AR |
579 | if (has_children(devcgroup)) |
580 | return -EINVAL; | |
581 | ||
db9aeca9 | 582 | dev_exception_clean(devcgroup); |
5b7aa7d5 | 583 | devcgroup->behavior = DEVCG_DEFAULT_DENY; |
ad676077 AR |
584 | break; |
585 | default: | |
586 | return -EINVAL; | |
587 | } | |
588 | return 0; | |
08ce5f16 | 589 | case 'b': |
db9aeca9 | 590 | ex.type = DEV_BLOCK; |
08ce5f16 SH |
591 | break; |
592 | case 'c': | |
db9aeca9 | 593 | ex.type = DEV_CHAR; |
08ce5f16 SH |
594 | break; |
595 | default: | |
f92523e3 | 596 | return -EINVAL; |
08ce5f16 SH |
597 | } |
598 | b++; | |
f92523e3 PM |
599 | if (!isspace(*b)) |
600 | return -EINVAL; | |
08ce5f16 SH |
601 | b++; |
602 | if (*b == '*') { | |
db9aeca9 | 603 | ex.major = ~0; |
08ce5f16 SH |
604 | b++; |
605 | } else if (isdigit(*b)) { | |
26fd8405 AR |
606 | memset(temp, 0, sizeof(temp)); |
607 | for (count = 0; count < sizeof(temp) - 1; count++) { | |
608 | temp[count] = *b; | |
609 | b++; | |
610 | if (!isdigit(*b)) | |
611 | break; | |
612 | } | |
613 | rc = kstrtou32(temp, 10, &ex.major); | |
614 | if (rc) | |
615 | return -EINVAL; | |
08ce5f16 | 616 | } else { |
f92523e3 | 617 | return -EINVAL; |
08ce5f16 | 618 | } |
f92523e3 PM |
619 | if (*b != ':') |
620 | return -EINVAL; | |
08ce5f16 SH |
621 | b++; |
622 | ||
623 | /* read minor */ | |
624 | if (*b == '*') { | |
db9aeca9 | 625 | ex.minor = ~0; |
08ce5f16 SH |
626 | b++; |
627 | } else if (isdigit(*b)) { | |
26fd8405 AR |
628 | memset(temp, 0, sizeof(temp)); |
629 | for (count = 0; count < sizeof(temp) - 1; count++) { | |
630 | temp[count] = *b; | |
631 | b++; | |
632 | if (!isdigit(*b)) | |
633 | break; | |
634 | } | |
635 | rc = kstrtou32(temp, 10, &ex.minor); | |
636 | if (rc) | |
637 | return -EINVAL; | |
08ce5f16 | 638 | } else { |
f92523e3 | 639 | return -EINVAL; |
08ce5f16 | 640 | } |
f92523e3 PM |
641 | if (!isspace(*b)) |
642 | return -EINVAL; | |
08ce5f16 SH |
643 | for (b++, count = 0; count < 3; count++, b++) { |
644 | switch (*b) { | |
645 | case 'r': | |
db9aeca9 | 646 | ex.access |= ACC_READ; |
08ce5f16 SH |
647 | break; |
648 | case 'w': | |
db9aeca9 | 649 | ex.access |= ACC_WRITE; |
08ce5f16 SH |
650 | break; |
651 | case 'm': | |
db9aeca9 | 652 | ex.access |= ACC_MKNOD; |
08ce5f16 SH |
653 | break; |
654 | case '\n': | |
655 | case '\0': | |
656 | count = 3; | |
657 | break; | |
658 | default: | |
f92523e3 | 659 | return -EINVAL; |
08ce5f16 SH |
660 | } |
661 | } | |
662 | ||
08ce5f16 SH |
663 | switch (filetype) { |
664 | case DEVCG_ALLOW: | |
db9aeca9 | 665 | if (!parent_has_perm(devcgroup, &ex)) |
f92523e3 | 666 | return -EPERM; |
ad676077 AR |
667 | /* |
668 | * If the default policy is to allow by default, try to remove | |
669 | * an matching exception instead. And be silent about it: we | |
670 | * don't want to break compatibility | |
671 | */ | |
5b7aa7d5 | 672 | if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) { |
db9aeca9 | 673 | dev_exception_rm(devcgroup, &ex); |
ad676077 AR |
674 | return 0; |
675 | } | |
bd2953eb AR |
676 | rc = dev_exception_add(devcgroup, &ex); |
677 | break; | |
08ce5f16 | 678 | case DEVCG_DENY: |
ad676077 AR |
679 | /* |
680 | * If the default policy is to deny by default, try to remove | |
681 | * an matching exception instead. And be silent about it: we | |
682 | * don't want to break compatibility | |
683 | */ | |
bd2953eb | 684 | if (devcgroup->behavior == DEVCG_DEFAULT_DENY) |
db9aeca9 | 685 | dev_exception_rm(devcgroup, &ex); |
bd2953eb AR |
686 | else |
687 | rc = dev_exception_add(devcgroup, &ex); | |
688 | ||
689 | if (rc) | |
690 | break; | |
691 | /* we only propagate new restrictions */ | |
692 | rc = propagate_exception(devcgroup, &ex); | |
693 | break; | |
08ce5f16 | 694 | default: |
bd2953eb | 695 | rc = -EINVAL; |
08ce5f16 | 696 | } |
bd2953eb | 697 | return rc; |
f92523e3 | 698 | } |
08ce5f16 | 699 | |
f92523e3 PM |
700 | static int devcgroup_access_write(struct cgroup *cgrp, struct cftype *cft, |
701 | const char *buffer) | |
702 | { | |
703 | int retval; | |
b4046f00 LZ |
704 | |
705 | mutex_lock(&devcgroup_mutex); | |
f92523e3 PM |
706 | retval = devcgroup_update_access(cgroup_to_devcgroup(cgrp), |
707 | cft->private, buffer); | |
b4046f00 | 708 | mutex_unlock(&devcgroup_mutex); |
08ce5f16 SH |
709 | return retval; |
710 | } | |
711 | ||
712 | static struct cftype dev_cgroup_files[] = { | |
713 | { | |
714 | .name = "allow", | |
f92523e3 | 715 | .write_string = devcgroup_access_write, |
08ce5f16 SH |
716 | .private = DEVCG_ALLOW, |
717 | }, | |
718 | { | |
719 | .name = "deny", | |
f92523e3 | 720 | .write_string = devcgroup_access_write, |
08ce5f16 SH |
721 | .private = DEVCG_DENY, |
722 | }, | |
29486df3 SH |
723 | { |
724 | .name = "list", | |
725 | .read_seq_string = devcgroup_seq_read, | |
726 | .private = DEVCG_LIST, | |
727 | }, | |
4baf6e33 | 728 | { } /* terminate */ |
08ce5f16 SH |
729 | }; |
730 | ||
08ce5f16 SH |
731 | struct cgroup_subsys devices_subsys = { |
732 | .name = "devices", | |
733 | .can_attach = devcgroup_can_attach, | |
92fb9748 TH |
734 | .css_alloc = devcgroup_css_alloc, |
735 | .css_free = devcgroup_css_free, | |
1909554c AR |
736 | .css_online = devcgroup_online, |
737 | .css_offline = devcgroup_offline, | |
08ce5f16 | 738 | .subsys_id = devices_subsys_id, |
4baf6e33 | 739 | .base_cftypes = dev_cgroup_files, |
08ce5f16 SH |
740 | }; |
741 | ||
ad676077 AR |
742 | /** |
743 | * __devcgroup_check_permission - checks if an inode operation is permitted | |
744 | * @dev_cgroup: the dev cgroup to be tested against | |
745 | * @type: device type | |
746 | * @major: device major number | |
747 | * @minor: device minor number | |
748 | * @access: combination of ACC_WRITE, ACC_READ and ACC_MKNOD | |
749 | * | |
750 | * returns 0 on success, -EPERM case the operation is not permitted | |
751 | */ | |
8c9506d1 | 752 | static int __devcgroup_check_permission(short type, u32 major, u32 minor, |
ad676077 | 753 | short access) |
08ce5f16 | 754 | { |
8c9506d1 | 755 | struct dev_cgroup *dev_cgroup; |
db9aeca9 | 756 | struct dev_exception_item ex; |
ad676077 | 757 | int rc; |
36fd71d2 | 758 | |
db9aeca9 AR |
759 | memset(&ex, 0, sizeof(ex)); |
760 | ex.type = type; | |
761 | ex.major = major; | |
762 | ex.minor = minor; | |
763 | ex.access = access; | |
36fd71d2 | 764 | |
ad676077 | 765 | rcu_read_lock(); |
8c9506d1 | 766 | dev_cgroup = task_devcgroup(current); |
c39a2a30 | 767 | rc = may_access(dev_cgroup, &ex, dev_cgroup->behavior); |
ad676077 | 768 | rcu_read_unlock(); |
cd500819 | 769 | |
ad676077 AR |
770 | if (!rc) |
771 | return -EPERM; | |
36fd71d2 | 772 | |
ad676077 AR |
773 | return 0; |
774 | } | |
08ce5f16 | 775 | |
ad676077 AR |
776 | int __devcgroup_inode_permission(struct inode *inode, int mask) |
777 | { | |
ad676077 AR |
778 | short type, access = 0; |
779 | ||
780 | if (S_ISBLK(inode->i_mode)) | |
781 | type = DEV_BLOCK; | |
782 | if (S_ISCHR(inode->i_mode)) | |
783 | type = DEV_CHAR; | |
784 | if (mask & MAY_WRITE) | |
785 | access |= ACC_WRITE; | |
786 | if (mask & MAY_READ) | |
787 | access |= ACC_READ; | |
788 | ||
8c9506d1 JS |
789 | return __devcgroup_check_permission(type, imajor(inode), iminor(inode), |
790 | access); | |
08ce5f16 SH |
791 | } |
792 | ||
793 | int devcgroup_inode_mknod(int mode, dev_t dev) | |
794 | { | |
ad676077 | 795 | short type; |
08ce5f16 | 796 | |
0b82ac37 SH |
797 | if (!S_ISBLK(mode) && !S_ISCHR(mode)) |
798 | return 0; | |
799 | ||
ad676077 AR |
800 | if (S_ISBLK(mode)) |
801 | type = DEV_BLOCK; | |
802 | else | |
803 | type = DEV_CHAR; | |
36fd71d2 | 804 | |
8c9506d1 JS |
805 | return __devcgroup_check_permission(type, MAJOR(dev), MINOR(dev), |
806 | ACC_MKNOD); | |
36fd71d2 | 807 | |
08ce5f16 | 808 | } |