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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 | ||
08ce5f16 | 28 | /* |
db9aeca9 | 29 | * exception list locking rules: |
b4046f00 | 30 | * hold devcgroup_mutex for update/read. |
47c59803 | 31 | * hold rcu_read_lock() for read. |
08ce5f16 SH |
32 | */ |
33 | ||
db9aeca9 | 34 | struct dev_exception_item { |
08ce5f16 SH |
35 | u32 major, minor; |
36 | short type; | |
37 | short access; | |
38 | struct list_head list; | |
4efd1a1b | 39 | struct rcu_head rcu; |
08ce5f16 SH |
40 | }; |
41 | ||
42 | struct dev_cgroup { | |
43 | struct cgroup_subsys_state css; | |
db9aeca9 | 44 | struct list_head exceptions; |
5b7aa7d5 AR |
45 | enum { |
46 | DEVCG_DEFAULT_ALLOW, | |
47 | DEVCG_DEFAULT_DENY, | |
48 | } behavior; | |
08ce5f16 SH |
49 | }; |
50 | ||
b66862f7 PE |
51 | static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s) |
52 | { | |
53 | return container_of(s, struct dev_cgroup, css); | |
54 | } | |
55 | ||
08ce5f16 SH |
56 | static inline struct dev_cgroup *cgroup_to_devcgroup(struct cgroup *cgroup) |
57 | { | |
b66862f7 | 58 | return css_to_devcgroup(cgroup_subsys_state(cgroup, devices_subsys_id)); |
08ce5f16 SH |
59 | } |
60 | ||
f92523e3 PM |
61 | static inline struct dev_cgroup *task_devcgroup(struct task_struct *task) |
62 | { | |
63 | return css_to_devcgroup(task_subsys_state(task, devices_subsys_id)); | |
64 | } | |
65 | ||
08ce5f16 SH |
66 | struct cgroup_subsys devices_subsys; |
67 | ||
761b3ef5 LZ |
68 | static int devcgroup_can_attach(struct cgroup *new_cgrp, |
69 | struct cgroup_taskset *set) | |
08ce5f16 | 70 | { |
2f7ee569 | 71 | struct task_struct *task = cgroup_taskset_first(set); |
08ce5f16 | 72 | |
2f7ee569 TH |
73 | if (current != task && !capable(CAP_SYS_ADMIN)) |
74 | return -EPERM; | |
08ce5f16 SH |
75 | return 0; |
76 | } | |
77 | ||
78 | /* | |
b4046f00 | 79 | * called under devcgroup_mutex |
08ce5f16 | 80 | */ |
db9aeca9 | 81 | static int dev_exceptions_copy(struct list_head *dest, struct list_head *orig) |
08ce5f16 | 82 | { |
db9aeca9 | 83 | struct dev_exception_item *ex, *tmp, *new; |
08ce5f16 | 84 | |
4b1c7840 TH |
85 | lockdep_assert_held(&devcgroup_mutex); |
86 | ||
db9aeca9 AR |
87 | list_for_each_entry(ex, orig, list) { |
88 | new = kmemdup(ex, sizeof(*ex), GFP_KERNEL); | |
08ce5f16 SH |
89 | if (!new) |
90 | goto free_and_exit; | |
08ce5f16 SH |
91 | list_add_tail(&new->list, dest); |
92 | } | |
93 | ||
94 | return 0; | |
95 | ||
96 | free_and_exit: | |
db9aeca9 AR |
97 | list_for_each_entry_safe(ex, tmp, dest, list) { |
98 | list_del(&ex->list); | |
99 | kfree(ex); | |
08ce5f16 SH |
100 | } |
101 | return -ENOMEM; | |
102 | } | |
103 | ||
08ce5f16 | 104 | /* |
b4046f00 | 105 | * called under devcgroup_mutex |
08ce5f16 | 106 | */ |
db9aeca9 AR |
107 | static int dev_exception_add(struct dev_cgroup *dev_cgroup, |
108 | struct dev_exception_item *ex) | |
08ce5f16 | 109 | { |
db9aeca9 | 110 | struct dev_exception_item *excopy, *walk; |
08ce5f16 | 111 | |
4b1c7840 TH |
112 | lockdep_assert_held(&devcgroup_mutex); |
113 | ||
db9aeca9 AR |
114 | excopy = kmemdup(ex, sizeof(*ex), GFP_KERNEL); |
115 | if (!excopy) | |
08ce5f16 SH |
116 | return -ENOMEM; |
117 | ||
db9aeca9 AR |
118 | list_for_each_entry(walk, &dev_cgroup->exceptions, list) { |
119 | if (walk->type != ex->type) | |
d1ee2971 | 120 | continue; |
db9aeca9 | 121 | if (walk->major != ex->major) |
d1ee2971 | 122 | continue; |
db9aeca9 | 123 | if (walk->minor != ex->minor) |
d1ee2971 PE |
124 | continue; |
125 | ||
db9aeca9 AR |
126 | walk->access |= ex->access; |
127 | kfree(excopy); | |
128 | excopy = NULL; | |
d1ee2971 PE |
129 | } |
130 | ||
db9aeca9 AR |
131 | if (excopy != NULL) |
132 | list_add_tail_rcu(&excopy->list, &dev_cgroup->exceptions); | |
08ce5f16 SH |
133 | return 0; |
134 | } | |
135 | ||
136 | /* | |
b4046f00 | 137 | * called under devcgroup_mutex |
08ce5f16 | 138 | */ |
db9aeca9 AR |
139 | static void dev_exception_rm(struct dev_cgroup *dev_cgroup, |
140 | struct dev_exception_item *ex) | |
08ce5f16 | 141 | { |
db9aeca9 | 142 | struct dev_exception_item *walk, *tmp; |
08ce5f16 | 143 | |
4b1c7840 TH |
144 | lockdep_assert_held(&devcgroup_mutex); |
145 | ||
db9aeca9 AR |
146 | list_for_each_entry_safe(walk, tmp, &dev_cgroup->exceptions, list) { |
147 | if (walk->type != ex->type) | |
08ce5f16 | 148 | continue; |
db9aeca9 | 149 | if (walk->major != ex->major) |
08ce5f16 | 150 | continue; |
db9aeca9 | 151 | if (walk->minor != ex->minor) |
08ce5f16 SH |
152 | continue; |
153 | ||
db9aeca9 | 154 | walk->access &= ~ex->access; |
08ce5f16 | 155 | if (!walk->access) { |
4efd1a1b | 156 | list_del_rcu(&walk->list); |
6034f7e6 | 157 | kfree_rcu(walk, rcu); |
08ce5f16 SH |
158 | } |
159 | } | |
08ce5f16 SH |
160 | } |
161 | ||
53eb8c82 JS |
162 | static void __dev_exception_clean(struct dev_cgroup *dev_cgroup) |
163 | { | |
164 | struct dev_exception_item *ex, *tmp; | |
165 | ||
166 | list_for_each_entry_safe(ex, tmp, &dev_cgroup->exceptions, list) { | |
167 | list_del_rcu(&ex->list); | |
168 | kfree_rcu(ex, rcu); | |
169 | } | |
170 | } | |
171 | ||
868539a3 | 172 | /** |
db9aeca9 AR |
173 | * dev_exception_clean - frees all entries of the exception list |
174 | * @dev_cgroup: dev_cgroup with the exception list to be cleaned | |
868539a3 AR |
175 | * |
176 | * called under devcgroup_mutex | |
177 | */ | |
db9aeca9 | 178 | static void dev_exception_clean(struct dev_cgroup *dev_cgroup) |
868539a3 | 179 | { |
4b1c7840 TH |
180 | lockdep_assert_held(&devcgroup_mutex); |
181 | ||
53eb8c82 | 182 | __dev_exception_clean(dev_cgroup); |
868539a3 AR |
183 | } |
184 | ||
08ce5f16 SH |
185 | /* |
186 | * called from kernel/cgroup.c with cgroup_lock() held. | |
187 | */ | |
92fb9748 | 188 | static struct cgroup_subsys_state *devcgroup_css_alloc(struct cgroup *cgroup) |
08ce5f16 SH |
189 | { |
190 | struct dev_cgroup *dev_cgroup, *parent_dev_cgroup; | |
191 | struct cgroup *parent_cgroup; | |
192 | int ret; | |
193 | ||
194 | dev_cgroup = kzalloc(sizeof(*dev_cgroup), GFP_KERNEL); | |
195 | if (!dev_cgroup) | |
196 | return ERR_PTR(-ENOMEM); | |
db9aeca9 | 197 | INIT_LIST_HEAD(&dev_cgroup->exceptions); |
08ce5f16 SH |
198 | parent_cgroup = cgroup->parent; |
199 | ||
ad676077 | 200 | if (parent_cgroup == NULL) |
5b7aa7d5 | 201 | dev_cgroup->behavior = DEVCG_DEFAULT_ALLOW; |
ad676077 | 202 | else { |
08ce5f16 | 203 | parent_dev_cgroup = cgroup_to_devcgroup(parent_cgroup); |
b4046f00 | 204 | mutex_lock(&devcgroup_mutex); |
db9aeca9 AR |
205 | ret = dev_exceptions_copy(&dev_cgroup->exceptions, |
206 | &parent_dev_cgroup->exceptions); | |
5b7aa7d5 | 207 | dev_cgroup->behavior = parent_dev_cgroup->behavior; |
b4046f00 | 208 | mutex_unlock(&devcgroup_mutex); |
08ce5f16 SH |
209 | if (ret) { |
210 | kfree(dev_cgroup); | |
211 | return ERR_PTR(ret); | |
212 | } | |
213 | } | |
214 | ||
08ce5f16 SH |
215 | return &dev_cgroup->css; |
216 | } | |
217 | ||
92fb9748 | 218 | static void devcgroup_css_free(struct cgroup *cgroup) |
08ce5f16 SH |
219 | { |
220 | struct dev_cgroup *dev_cgroup; | |
08ce5f16 SH |
221 | |
222 | dev_cgroup = cgroup_to_devcgroup(cgroup); | |
53eb8c82 | 223 | __dev_exception_clean(dev_cgroup); |
08ce5f16 SH |
224 | kfree(dev_cgroup); |
225 | } | |
226 | ||
227 | #define DEVCG_ALLOW 1 | |
228 | #define DEVCG_DENY 2 | |
29486df3 SH |
229 | #define DEVCG_LIST 3 |
230 | ||
17d213f8 | 231 | #define MAJMINLEN 13 |
29486df3 | 232 | #define ACCLEN 4 |
08ce5f16 SH |
233 | |
234 | static void set_access(char *acc, short access) | |
235 | { | |
236 | int idx = 0; | |
29486df3 | 237 | memset(acc, 0, ACCLEN); |
08ce5f16 SH |
238 | if (access & ACC_READ) |
239 | acc[idx++] = 'r'; | |
240 | if (access & ACC_WRITE) | |
241 | acc[idx++] = 'w'; | |
242 | if (access & ACC_MKNOD) | |
243 | acc[idx++] = 'm'; | |
244 | } | |
245 | ||
246 | static char type_to_char(short type) | |
247 | { | |
248 | if (type == DEV_ALL) | |
249 | return 'a'; | |
250 | if (type == DEV_CHAR) | |
251 | return 'c'; | |
252 | if (type == DEV_BLOCK) | |
253 | return 'b'; | |
254 | return 'X'; | |
255 | } | |
256 | ||
29486df3 | 257 | static void set_majmin(char *str, unsigned m) |
08ce5f16 | 258 | { |
08ce5f16 | 259 | if (m == ~0) |
7759fc9d | 260 | strcpy(str, "*"); |
08ce5f16 | 261 | else |
7759fc9d | 262 | sprintf(str, "%u", m); |
08ce5f16 SH |
263 | } |
264 | ||
29486df3 SH |
265 | static int devcgroup_seq_read(struct cgroup *cgroup, struct cftype *cft, |
266 | struct seq_file *m) | |
08ce5f16 | 267 | { |
29486df3 | 268 | struct dev_cgroup *devcgroup = cgroup_to_devcgroup(cgroup); |
db9aeca9 | 269 | struct dev_exception_item *ex; |
29486df3 | 270 | char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN]; |
08ce5f16 | 271 | |
4efd1a1b | 272 | rcu_read_lock(); |
ad676077 AR |
273 | /* |
274 | * To preserve the compatibility: | |
275 | * - Only show the "all devices" when the default policy is to allow | |
276 | * - List the exceptions in case the default policy is to deny | |
277 | * This way, the file remains as a "whitelist of devices" | |
278 | */ | |
5b7aa7d5 | 279 | if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) { |
ad676077 AR |
280 | set_access(acc, ACC_MASK); |
281 | set_majmin(maj, ~0); | |
282 | set_majmin(min, ~0); | |
283 | seq_printf(m, "%c %s:%s %s\n", type_to_char(DEV_ALL), | |
29486df3 | 284 | maj, min, acc); |
ad676077 | 285 | } else { |
db9aeca9 AR |
286 | list_for_each_entry_rcu(ex, &devcgroup->exceptions, list) { |
287 | set_access(acc, ex->access); | |
288 | set_majmin(maj, ex->major); | |
289 | set_majmin(min, ex->minor); | |
290 | seq_printf(m, "%c %s:%s %s\n", type_to_char(ex->type), | |
ad676077 AR |
291 | maj, min, acc); |
292 | } | |
08ce5f16 | 293 | } |
4efd1a1b | 294 | rcu_read_unlock(); |
08ce5f16 | 295 | |
29486df3 | 296 | return 0; |
08ce5f16 SH |
297 | } |
298 | ||
ad676077 | 299 | /** |
db9aeca9 AR |
300 | * may_access - verifies if a new exception is part of what is allowed |
301 | * by a dev cgroup based on the default policy + | |
302 | * exceptions. This is used to make sure a child cgroup | |
303 | * won't have more privileges than its parent or to | |
304 | * verify if a certain access is allowed. | |
ad676077 | 305 | * @dev_cgroup: dev cgroup to be tested against |
db9aeca9 | 306 | * @refex: new exception |
08ce5f16 | 307 | */ |
26898fdf AR |
308 | static bool may_access(struct dev_cgroup *dev_cgroup, |
309 | struct dev_exception_item *refex) | |
08ce5f16 | 310 | { |
db9aeca9 | 311 | struct dev_exception_item *ex; |
ad676077 | 312 | bool match = false; |
08ce5f16 | 313 | |
4b1c7840 TH |
314 | rcu_lockdep_assert(rcu_read_lock_held() || |
315 | lockdep_is_held(&devcgroup_mutex), | |
316 | "device_cgroup::may_access() called without proper synchronization"); | |
317 | ||
201e72ac | 318 | list_for_each_entry_rcu(ex, &dev_cgroup->exceptions, list) { |
db9aeca9 | 319 | if ((refex->type & DEV_BLOCK) && !(ex->type & DEV_BLOCK)) |
08ce5f16 | 320 | continue; |
db9aeca9 | 321 | if ((refex->type & DEV_CHAR) && !(ex->type & DEV_CHAR)) |
08ce5f16 | 322 | continue; |
db9aeca9 | 323 | if (ex->major != ~0 && ex->major != refex->major) |
08ce5f16 | 324 | continue; |
db9aeca9 | 325 | if (ex->minor != ~0 && ex->minor != refex->minor) |
08ce5f16 | 326 | continue; |
db9aeca9 | 327 | if (refex->access & (~ex->access)) |
08ce5f16 | 328 | continue; |
ad676077 AR |
329 | match = true; |
330 | break; | |
08ce5f16 | 331 | } |
ad676077 AR |
332 | |
333 | /* | |
db9aeca9 | 334 | * In two cases we'll consider this new exception valid: |
ad676077 | 335 | * - the dev cgroup has its default policy to deny + exception list: |
db9aeca9 | 336 | * the new exception *should* match the exceptions |
26898fdf AR |
337 | * - the dev cgroup has its default policy to allow + exception list: |
338 | * the new exception should *not* match any of the exceptions | |
ad676077 | 339 | */ |
26898fdf AR |
340 | if (dev_cgroup->behavior == DEVCG_DEFAULT_DENY) { |
341 | if (match) | |
342 | return true; | |
343 | } else { | |
344 | if (!match) | |
345 | return true; | |
346 | } | |
347 | return false; | |
08ce5f16 SH |
348 | } |
349 | ||
350 | /* | |
351 | * parent_has_perm: | |
db9aeca9 | 352 | * when adding a new allow rule to a device exception list, the rule |
08ce5f16 SH |
353 | * must be allowed in the parent device |
354 | */ | |
f92523e3 | 355 | static int parent_has_perm(struct dev_cgroup *childcg, |
db9aeca9 | 356 | struct dev_exception_item *ex) |
08ce5f16 | 357 | { |
f92523e3 | 358 | struct cgroup *pcg = childcg->css.cgroup->parent; |
08ce5f16 | 359 | struct dev_cgroup *parent; |
08ce5f16 SH |
360 | |
361 | if (!pcg) | |
362 | return 1; | |
363 | parent = cgroup_to_devcgroup(pcg); | |
db9aeca9 | 364 | return may_access(parent, ex); |
08ce5f16 SH |
365 | } |
366 | ||
4cef7299 AR |
367 | /** |
368 | * may_allow_all - checks if it's possible to change the behavior to | |
369 | * allow based on parent's rules. | |
370 | * @parent: device cgroup's parent | |
371 | * returns: != 0 in case it's allowed, 0 otherwise | |
372 | */ | |
373 | static inline int may_allow_all(struct dev_cgroup *parent) | |
374 | { | |
64e10477 AR |
375 | if (!parent) |
376 | return 1; | |
4cef7299 AR |
377 | return parent->behavior == DEVCG_DEFAULT_ALLOW; |
378 | } | |
379 | ||
08ce5f16 | 380 | /* |
db9aeca9 | 381 | * Modify the exception list using allow/deny rules. |
08ce5f16 SH |
382 | * CAP_SYS_ADMIN is needed for this. It's at least separate from CAP_MKNOD |
383 | * so we can give a container CAP_MKNOD to let it create devices but not | |
db9aeca9 | 384 | * modify the exception list. |
08ce5f16 SH |
385 | * It seems likely we'll want to add a CAP_CONTAINER capability to allow |
386 | * us to also grant CAP_SYS_ADMIN to containers without giving away the | |
db9aeca9 | 387 | * device exception list controls, but for now we'll stick with CAP_SYS_ADMIN |
08ce5f16 SH |
388 | * |
389 | * Taking rules away is always allowed (given CAP_SYS_ADMIN). Granting | |
390 | * new access is only allowed if you're in the top-level cgroup, or your | |
391 | * parent cgroup has the access you're asking for. | |
392 | */ | |
f92523e3 PM |
393 | static int devcgroup_update_access(struct dev_cgroup *devcgroup, |
394 | int filetype, const char *buffer) | |
08ce5f16 | 395 | { |
f92523e3 | 396 | const char *b; |
26fd8405 AR |
397 | char temp[12]; /* 11 + 1 characters needed for a u32 */ |
398 | int count, rc; | |
db9aeca9 | 399 | struct dev_exception_item ex; |
4cef7299 | 400 | struct cgroup *p = devcgroup->css.cgroup; |
64e10477 | 401 | struct dev_cgroup *parent = NULL; |
08ce5f16 SH |
402 | |
403 | if (!capable(CAP_SYS_ADMIN)) | |
404 | return -EPERM; | |
405 | ||
64e10477 AR |
406 | if (p->parent) |
407 | parent = cgroup_to_devcgroup(p->parent); | |
408 | ||
db9aeca9 | 409 | memset(&ex, 0, sizeof(ex)); |
08ce5f16 SH |
410 | b = buffer; |
411 | ||
412 | switch (*b) { | |
413 | case 'a': | |
ad676077 AR |
414 | switch (filetype) { |
415 | case DEVCG_ALLOW: | |
4cef7299 | 416 | if (!may_allow_all(parent)) |
ad676077 | 417 | return -EPERM; |
db9aeca9 | 418 | dev_exception_clean(devcgroup); |
64e10477 AR |
419 | devcgroup->behavior = DEVCG_DEFAULT_ALLOW; |
420 | if (!parent) | |
421 | break; | |
422 | ||
4cef7299 AR |
423 | rc = dev_exceptions_copy(&devcgroup->exceptions, |
424 | &parent->exceptions); | |
425 | if (rc) | |
426 | return rc; | |
ad676077 AR |
427 | break; |
428 | case DEVCG_DENY: | |
db9aeca9 | 429 | dev_exception_clean(devcgroup); |
5b7aa7d5 | 430 | devcgroup->behavior = DEVCG_DEFAULT_DENY; |
ad676077 AR |
431 | break; |
432 | default: | |
433 | return -EINVAL; | |
434 | } | |
435 | return 0; | |
08ce5f16 | 436 | case 'b': |
db9aeca9 | 437 | ex.type = DEV_BLOCK; |
08ce5f16 SH |
438 | break; |
439 | case 'c': | |
db9aeca9 | 440 | ex.type = DEV_CHAR; |
08ce5f16 SH |
441 | break; |
442 | default: | |
f92523e3 | 443 | return -EINVAL; |
08ce5f16 SH |
444 | } |
445 | b++; | |
f92523e3 PM |
446 | if (!isspace(*b)) |
447 | return -EINVAL; | |
08ce5f16 SH |
448 | b++; |
449 | if (*b == '*') { | |
db9aeca9 | 450 | ex.major = ~0; |
08ce5f16 SH |
451 | b++; |
452 | } else if (isdigit(*b)) { | |
26fd8405 AR |
453 | memset(temp, 0, sizeof(temp)); |
454 | for (count = 0; count < sizeof(temp) - 1; count++) { | |
455 | temp[count] = *b; | |
456 | b++; | |
457 | if (!isdigit(*b)) | |
458 | break; | |
459 | } | |
460 | rc = kstrtou32(temp, 10, &ex.major); | |
461 | if (rc) | |
462 | return -EINVAL; | |
08ce5f16 | 463 | } else { |
f92523e3 | 464 | return -EINVAL; |
08ce5f16 | 465 | } |
f92523e3 PM |
466 | if (*b != ':') |
467 | return -EINVAL; | |
08ce5f16 SH |
468 | b++; |
469 | ||
470 | /* read minor */ | |
471 | if (*b == '*') { | |
db9aeca9 | 472 | ex.minor = ~0; |
08ce5f16 SH |
473 | b++; |
474 | } else if (isdigit(*b)) { | |
26fd8405 AR |
475 | memset(temp, 0, sizeof(temp)); |
476 | for (count = 0; count < sizeof(temp) - 1; count++) { | |
477 | temp[count] = *b; | |
478 | b++; | |
479 | if (!isdigit(*b)) | |
480 | break; | |
481 | } | |
482 | rc = kstrtou32(temp, 10, &ex.minor); | |
483 | if (rc) | |
484 | return -EINVAL; | |
08ce5f16 | 485 | } else { |
f92523e3 | 486 | return -EINVAL; |
08ce5f16 | 487 | } |
f92523e3 PM |
488 | if (!isspace(*b)) |
489 | return -EINVAL; | |
08ce5f16 SH |
490 | for (b++, count = 0; count < 3; count++, b++) { |
491 | switch (*b) { | |
492 | case 'r': | |
db9aeca9 | 493 | ex.access |= ACC_READ; |
08ce5f16 SH |
494 | break; |
495 | case 'w': | |
db9aeca9 | 496 | ex.access |= ACC_WRITE; |
08ce5f16 SH |
497 | break; |
498 | case 'm': | |
db9aeca9 | 499 | ex.access |= ACC_MKNOD; |
08ce5f16 SH |
500 | break; |
501 | case '\n': | |
502 | case '\0': | |
503 | count = 3; | |
504 | break; | |
505 | default: | |
f92523e3 | 506 | return -EINVAL; |
08ce5f16 SH |
507 | } |
508 | } | |
509 | ||
08ce5f16 SH |
510 | switch (filetype) { |
511 | case DEVCG_ALLOW: | |
db9aeca9 | 512 | if (!parent_has_perm(devcgroup, &ex)) |
f92523e3 | 513 | return -EPERM; |
ad676077 AR |
514 | /* |
515 | * If the default policy is to allow by default, try to remove | |
516 | * an matching exception instead. And be silent about it: we | |
517 | * don't want to break compatibility | |
518 | */ | |
5b7aa7d5 | 519 | if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) { |
db9aeca9 | 520 | dev_exception_rm(devcgroup, &ex); |
ad676077 AR |
521 | return 0; |
522 | } | |
db9aeca9 | 523 | return dev_exception_add(devcgroup, &ex); |
08ce5f16 | 524 | case DEVCG_DENY: |
ad676077 AR |
525 | /* |
526 | * If the default policy is to deny by default, try to remove | |
527 | * an matching exception instead. And be silent about it: we | |
528 | * don't want to break compatibility | |
529 | */ | |
5b7aa7d5 | 530 | if (devcgroup->behavior == DEVCG_DEFAULT_DENY) { |
db9aeca9 | 531 | dev_exception_rm(devcgroup, &ex); |
ad676077 AR |
532 | return 0; |
533 | } | |
db9aeca9 | 534 | return dev_exception_add(devcgroup, &ex); |
08ce5f16 | 535 | default: |
f92523e3 | 536 | return -EINVAL; |
08ce5f16 | 537 | } |
f92523e3 PM |
538 | return 0; |
539 | } | |
08ce5f16 | 540 | |
f92523e3 PM |
541 | static int devcgroup_access_write(struct cgroup *cgrp, struct cftype *cft, |
542 | const char *buffer) | |
543 | { | |
544 | int retval; | |
b4046f00 LZ |
545 | |
546 | mutex_lock(&devcgroup_mutex); | |
f92523e3 PM |
547 | retval = devcgroup_update_access(cgroup_to_devcgroup(cgrp), |
548 | cft->private, buffer); | |
b4046f00 | 549 | mutex_unlock(&devcgroup_mutex); |
08ce5f16 SH |
550 | return retval; |
551 | } | |
552 | ||
553 | static struct cftype dev_cgroup_files[] = { | |
554 | { | |
555 | .name = "allow", | |
f92523e3 | 556 | .write_string = devcgroup_access_write, |
08ce5f16 SH |
557 | .private = DEVCG_ALLOW, |
558 | }, | |
559 | { | |
560 | .name = "deny", | |
f92523e3 | 561 | .write_string = devcgroup_access_write, |
08ce5f16 SH |
562 | .private = DEVCG_DENY, |
563 | }, | |
29486df3 SH |
564 | { |
565 | .name = "list", | |
566 | .read_seq_string = devcgroup_seq_read, | |
567 | .private = DEVCG_LIST, | |
568 | }, | |
4baf6e33 | 569 | { } /* terminate */ |
08ce5f16 SH |
570 | }; |
571 | ||
08ce5f16 SH |
572 | struct cgroup_subsys devices_subsys = { |
573 | .name = "devices", | |
574 | .can_attach = devcgroup_can_attach, | |
92fb9748 TH |
575 | .css_alloc = devcgroup_css_alloc, |
576 | .css_free = devcgroup_css_free, | |
08ce5f16 | 577 | .subsys_id = devices_subsys_id, |
4baf6e33 | 578 | .base_cftypes = dev_cgroup_files, |
8c7f6edb TH |
579 | |
580 | /* | |
581 | * While devices cgroup has the rudimentary hierarchy support which | |
582 | * checks the parent's restriction, it doesn't properly propagates | |
583 | * config changes in ancestors to their descendents. A child | |
584 | * should only be allowed to add more restrictions to the parent's | |
585 | * configuration. Fix it and remove the following. | |
586 | */ | |
587 | .broken_hierarchy = true, | |
08ce5f16 SH |
588 | }; |
589 | ||
ad676077 AR |
590 | /** |
591 | * __devcgroup_check_permission - checks if an inode operation is permitted | |
592 | * @dev_cgroup: the dev cgroup to be tested against | |
593 | * @type: device type | |
594 | * @major: device major number | |
595 | * @minor: device minor number | |
596 | * @access: combination of ACC_WRITE, ACC_READ and ACC_MKNOD | |
597 | * | |
598 | * returns 0 on success, -EPERM case the operation is not permitted | |
599 | */ | |
8c9506d1 | 600 | static int __devcgroup_check_permission(short type, u32 major, u32 minor, |
ad676077 | 601 | short access) |
08ce5f16 | 602 | { |
8c9506d1 | 603 | struct dev_cgroup *dev_cgroup; |
db9aeca9 | 604 | struct dev_exception_item ex; |
ad676077 | 605 | int rc; |
36fd71d2 | 606 | |
db9aeca9 AR |
607 | memset(&ex, 0, sizeof(ex)); |
608 | ex.type = type; | |
609 | ex.major = major; | |
610 | ex.minor = minor; | |
611 | ex.access = access; | |
36fd71d2 | 612 | |
ad676077 | 613 | rcu_read_lock(); |
8c9506d1 | 614 | dev_cgroup = task_devcgroup(current); |
db9aeca9 | 615 | rc = may_access(dev_cgroup, &ex); |
ad676077 | 616 | rcu_read_unlock(); |
cd500819 | 617 | |
ad676077 AR |
618 | if (!rc) |
619 | return -EPERM; | |
36fd71d2 | 620 | |
ad676077 AR |
621 | return 0; |
622 | } | |
08ce5f16 | 623 | |
ad676077 AR |
624 | int __devcgroup_inode_permission(struct inode *inode, int mask) |
625 | { | |
ad676077 AR |
626 | short type, access = 0; |
627 | ||
628 | if (S_ISBLK(inode->i_mode)) | |
629 | type = DEV_BLOCK; | |
630 | if (S_ISCHR(inode->i_mode)) | |
631 | type = DEV_CHAR; | |
632 | if (mask & MAY_WRITE) | |
633 | access |= ACC_WRITE; | |
634 | if (mask & MAY_READ) | |
635 | access |= ACC_READ; | |
636 | ||
8c9506d1 JS |
637 | return __devcgroup_check_permission(type, imajor(inode), iminor(inode), |
638 | access); | |
08ce5f16 SH |
639 | } |
640 | ||
641 | int devcgroup_inode_mknod(int mode, dev_t dev) | |
642 | { | |
ad676077 | 643 | short type; |
08ce5f16 | 644 | |
0b82ac37 SH |
645 | if (!S_ISBLK(mode) && !S_ISCHR(mode)) |
646 | return 0; | |
647 | ||
ad676077 AR |
648 | if (S_ISBLK(mode)) |
649 | type = DEV_BLOCK; | |
650 | else | |
651 | type = DEV_CHAR; | |
36fd71d2 | 652 | |
8c9506d1 JS |
653 | return __devcgroup_check_permission(type, MAJOR(dev), MINOR(dev), |
654 | ACC_MKNOD); | |
36fd71d2 | 655 | |
08ce5f16 | 656 | } |