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 | |
db9aeca9 AR |
85 | list_for_each_entry(ex, orig, list) { |
86 | new = kmemdup(ex, sizeof(*ex), GFP_KERNEL); | |
08ce5f16 SH |
87 | if (!new) |
88 | goto free_and_exit; | |
08ce5f16 SH |
89 | list_add_tail(&new->list, dest); |
90 | } | |
91 | ||
92 | return 0; | |
93 | ||
94 | free_and_exit: | |
db9aeca9 AR |
95 | list_for_each_entry_safe(ex, tmp, dest, list) { |
96 | list_del(&ex->list); | |
97 | kfree(ex); | |
08ce5f16 SH |
98 | } |
99 | return -ENOMEM; | |
100 | } | |
101 | ||
08ce5f16 | 102 | /* |
b4046f00 | 103 | * called under devcgroup_mutex |
08ce5f16 | 104 | */ |
db9aeca9 AR |
105 | static int dev_exception_add(struct dev_cgroup *dev_cgroup, |
106 | struct dev_exception_item *ex) | |
08ce5f16 | 107 | { |
db9aeca9 | 108 | struct dev_exception_item *excopy, *walk; |
08ce5f16 | 109 | |
db9aeca9 AR |
110 | excopy = kmemdup(ex, sizeof(*ex), GFP_KERNEL); |
111 | if (!excopy) | |
08ce5f16 SH |
112 | return -ENOMEM; |
113 | ||
db9aeca9 AR |
114 | list_for_each_entry(walk, &dev_cgroup->exceptions, list) { |
115 | if (walk->type != ex->type) | |
d1ee2971 | 116 | continue; |
db9aeca9 | 117 | if (walk->major != ex->major) |
d1ee2971 | 118 | continue; |
db9aeca9 | 119 | if (walk->minor != ex->minor) |
d1ee2971 PE |
120 | continue; |
121 | ||
db9aeca9 AR |
122 | walk->access |= ex->access; |
123 | kfree(excopy); | |
124 | excopy = NULL; | |
d1ee2971 PE |
125 | } |
126 | ||
db9aeca9 AR |
127 | if (excopy != NULL) |
128 | list_add_tail_rcu(&excopy->list, &dev_cgroup->exceptions); | |
08ce5f16 SH |
129 | return 0; |
130 | } | |
131 | ||
132 | /* | |
b4046f00 | 133 | * called under devcgroup_mutex |
08ce5f16 | 134 | */ |
db9aeca9 AR |
135 | static void dev_exception_rm(struct dev_cgroup *dev_cgroup, |
136 | struct dev_exception_item *ex) | |
08ce5f16 | 137 | { |
db9aeca9 | 138 | struct dev_exception_item *walk, *tmp; |
08ce5f16 | 139 | |
db9aeca9 AR |
140 | list_for_each_entry_safe(walk, tmp, &dev_cgroup->exceptions, list) { |
141 | if (walk->type != ex->type) | |
08ce5f16 | 142 | continue; |
db9aeca9 | 143 | if (walk->major != ex->major) |
08ce5f16 | 144 | continue; |
db9aeca9 | 145 | if (walk->minor != ex->minor) |
08ce5f16 SH |
146 | continue; |
147 | ||
db9aeca9 | 148 | walk->access &= ~ex->access; |
08ce5f16 | 149 | if (!walk->access) { |
4efd1a1b | 150 | list_del_rcu(&walk->list); |
6034f7e6 | 151 | kfree_rcu(walk, rcu); |
08ce5f16 SH |
152 | } |
153 | } | |
08ce5f16 SH |
154 | } |
155 | ||
868539a3 | 156 | /** |
db9aeca9 AR |
157 | * dev_exception_clean - frees all entries of the exception list |
158 | * @dev_cgroup: dev_cgroup with the exception list to be cleaned | |
868539a3 AR |
159 | * |
160 | * called under devcgroup_mutex | |
161 | */ | |
db9aeca9 | 162 | static void dev_exception_clean(struct dev_cgroup *dev_cgroup) |
868539a3 | 163 | { |
db9aeca9 | 164 | struct dev_exception_item *ex, *tmp; |
868539a3 | 165 | |
db9aeca9 | 166 | list_for_each_entry_safe(ex, tmp, &dev_cgroup->exceptions, list) { |
201e72ac TH |
167 | list_del_rcu(&ex->list); |
168 | kfree_rcu(ex, rcu); | |
868539a3 AR |
169 | } |
170 | } | |
171 | ||
08ce5f16 SH |
172 | /* |
173 | * called from kernel/cgroup.c with cgroup_lock() held. | |
174 | */ | |
761b3ef5 | 175 | static struct cgroup_subsys_state *devcgroup_create(struct cgroup *cgroup) |
08ce5f16 SH |
176 | { |
177 | struct dev_cgroup *dev_cgroup, *parent_dev_cgroup; | |
178 | struct cgroup *parent_cgroup; | |
179 | int ret; | |
180 | ||
181 | dev_cgroup = kzalloc(sizeof(*dev_cgroup), GFP_KERNEL); | |
182 | if (!dev_cgroup) | |
183 | return ERR_PTR(-ENOMEM); | |
db9aeca9 | 184 | INIT_LIST_HEAD(&dev_cgroup->exceptions); |
08ce5f16 SH |
185 | parent_cgroup = cgroup->parent; |
186 | ||
ad676077 | 187 | if (parent_cgroup == NULL) |
5b7aa7d5 | 188 | dev_cgroup->behavior = DEVCG_DEFAULT_ALLOW; |
ad676077 | 189 | else { |
08ce5f16 | 190 | parent_dev_cgroup = cgroup_to_devcgroup(parent_cgroup); |
b4046f00 | 191 | mutex_lock(&devcgroup_mutex); |
db9aeca9 AR |
192 | ret = dev_exceptions_copy(&dev_cgroup->exceptions, |
193 | &parent_dev_cgroup->exceptions); | |
5b7aa7d5 | 194 | dev_cgroup->behavior = parent_dev_cgroup->behavior; |
b4046f00 | 195 | mutex_unlock(&devcgroup_mutex); |
08ce5f16 SH |
196 | if (ret) { |
197 | kfree(dev_cgroup); | |
198 | return ERR_PTR(ret); | |
199 | } | |
200 | } | |
201 | ||
08ce5f16 SH |
202 | return &dev_cgroup->css; |
203 | } | |
204 | ||
761b3ef5 | 205 | static void devcgroup_destroy(struct cgroup *cgroup) |
08ce5f16 SH |
206 | { |
207 | struct dev_cgroup *dev_cgroup; | |
08ce5f16 SH |
208 | |
209 | dev_cgroup = cgroup_to_devcgroup(cgroup); | |
db9aeca9 | 210 | dev_exception_clean(dev_cgroup); |
08ce5f16 SH |
211 | kfree(dev_cgroup); |
212 | } | |
213 | ||
214 | #define DEVCG_ALLOW 1 | |
215 | #define DEVCG_DENY 2 | |
29486df3 SH |
216 | #define DEVCG_LIST 3 |
217 | ||
17d213f8 | 218 | #define MAJMINLEN 13 |
29486df3 | 219 | #define ACCLEN 4 |
08ce5f16 SH |
220 | |
221 | static void set_access(char *acc, short access) | |
222 | { | |
223 | int idx = 0; | |
29486df3 | 224 | memset(acc, 0, ACCLEN); |
08ce5f16 SH |
225 | if (access & ACC_READ) |
226 | acc[idx++] = 'r'; | |
227 | if (access & ACC_WRITE) | |
228 | acc[idx++] = 'w'; | |
229 | if (access & ACC_MKNOD) | |
230 | acc[idx++] = 'm'; | |
231 | } | |
232 | ||
233 | static char type_to_char(short type) | |
234 | { | |
235 | if (type == DEV_ALL) | |
236 | return 'a'; | |
237 | if (type == DEV_CHAR) | |
238 | return 'c'; | |
239 | if (type == DEV_BLOCK) | |
240 | return 'b'; | |
241 | return 'X'; | |
242 | } | |
243 | ||
29486df3 | 244 | static void set_majmin(char *str, unsigned m) |
08ce5f16 | 245 | { |
08ce5f16 | 246 | if (m == ~0) |
7759fc9d | 247 | strcpy(str, "*"); |
08ce5f16 | 248 | else |
7759fc9d | 249 | sprintf(str, "%u", m); |
08ce5f16 SH |
250 | } |
251 | ||
29486df3 SH |
252 | static int devcgroup_seq_read(struct cgroup *cgroup, struct cftype *cft, |
253 | struct seq_file *m) | |
08ce5f16 | 254 | { |
29486df3 | 255 | struct dev_cgroup *devcgroup = cgroup_to_devcgroup(cgroup); |
db9aeca9 | 256 | struct dev_exception_item *ex; |
29486df3 | 257 | char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN]; |
08ce5f16 | 258 | |
4efd1a1b | 259 | rcu_read_lock(); |
ad676077 AR |
260 | /* |
261 | * To preserve the compatibility: | |
262 | * - Only show the "all devices" when the default policy is to allow | |
263 | * - List the exceptions in case the default policy is to deny | |
264 | * This way, the file remains as a "whitelist of devices" | |
265 | */ | |
5b7aa7d5 | 266 | if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) { |
ad676077 AR |
267 | set_access(acc, ACC_MASK); |
268 | set_majmin(maj, ~0); | |
269 | set_majmin(min, ~0); | |
270 | seq_printf(m, "%c %s:%s %s\n", type_to_char(DEV_ALL), | |
29486df3 | 271 | maj, min, acc); |
ad676077 | 272 | } else { |
db9aeca9 AR |
273 | list_for_each_entry_rcu(ex, &devcgroup->exceptions, list) { |
274 | set_access(acc, ex->access); | |
275 | set_majmin(maj, ex->major); | |
276 | set_majmin(min, ex->minor); | |
277 | seq_printf(m, "%c %s:%s %s\n", type_to_char(ex->type), | |
ad676077 AR |
278 | maj, min, acc); |
279 | } | |
08ce5f16 | 280 | } |
4efd1a1b | 281 | rcu_read_unlock(); |
08ce5f16 | 282 | |
29486df3 | 283 | return 0; |
08ce5f16 SH |
284 | } |
285 | ||
ad676077 | 286 | /** |
db9aeca9 AR |
287 | * may_access - verifies if a new exception is part of what is allowed |
288 | * by a dev cgroup based on the default policy + | |
289 | * exceptions. This is used to make sure a child cgroup | |
290 | * won't have more privileges than its parent or to | |
291 | * verify if a certain access is allowed. | |
ad676077 | 292 | * @dev_cgroup: dev cgroup to be tested against |
db9aeca9 | 293 | * @refex: new exception |
08ce5f16 | 294 | */ |
db9aeca9 AR |
295 | static int may_access(struct dev_cgroup *dev_cgroup, |
296 | struct dev_exception_item *refex) | |
08ce5f16 | 297 | { |
db9aeca9 | 298 | struct dev_exception_item *ex; |
ad676077 | 299 | bool match = false; |
08ce5f16 | 300 | |
201e72ac | 301 | list_for_each_entry_rcu(ex, &dev_cgroup->exceptions, list) { |
db9aeca9 | 302 | if ((refex->type & DEV_BLOCK) && !(ex->type & DEV_BLOCK)) |
08ce5f16 | 303 | continue; |
db9aeca9 | 304 | if ((refex->type & DEV_CHAR) && !(ex->type & DEV_CHAR)) |
08ce5f16 | 305 | continue; |
db9aeca9 | 306 | if (ex->major != ~0 && ex->major != refex->major) |
08ce5f16 | 307 | continue; |
db9aeca9 | 308 | if (ex->minor != ~0 && ex->minor != refex->minor) |
08ce5f16 | 309 | continue; |
db9aeca9 | 310 | if (refex->access & (~ex->access)) |
08ce5f16 | 311 | continue; |
ad676077 AR |
312 | match = true; |
313 | break; | |
08ce5f16 | 314 | } |
ad676077 AR |
315 | |
316 | /* | |
db9aeca9 | 317 | * In two cases we'll consider this new exception valid: |
ad676077 | 318 | * - the dev cgroup has its default policy to allow + exception list: |
db9aeca9 | 319 | * the new exception should *not* match any of the exceptions |
5b7aa7d5 | 320 | * (behavior == DEVCG_DEFAULT_ALLOW, !match) |
ad676077 | 321 | * - the dev cgroup has its default policy to deny + exception list: |
db9aeca9 | 322 | * the new exception *should* match the exceptions |
5b7aa7d5 | 323 | * (behavior == DEVCG_DEFAULT_DENY, match) |
ad676077 | 324 | */ |
5b7aa7d5 | 325 | if ((dev_cgroup->behavior == DEVCG_DEFAULT_DENY) == match) |
ad676077 | 326 | return 1; |
08ce5f16 SH |
327 | return 0; |
328 | } | |
329 | ||
330 | /* | |
331 | * parent_has_perm: | |
db9aeca9 | 332 | * when adding a new allow rule to a device exception list, the rule |
08ce5f16 SH |
333 | * must be allowed in the parent device |
334 | */ | |
f92523e3 | 335 | static int parent_has_perm(struct dev_cgroup *childcg, |
db9aeca9 | 336 | struct dev_exception_item *ex) |
08ce5f16 | 337 | { |
f92523e3 | 338 | struct cgroup *pcg = childcg->css.cgroup->parent; |
08ce5f16 | 339 | struct dev_cgroup *parent; |
08ce5f16 SH |
340 | |
341 | if (!pcg) | |
342 | return 1; | |
343 | parent = cgroup_to_devcgroup(pcg); | |
db9aeca9 | 344 | return may_access(parent, ex); |
08ce5f16 SH |
345 | } |
346 | ||
4cef7299 AR |
347 | /** |
348 | * may_allow_all - checks if it's possible to change the behavior to | |
349 | * allow based on parent's rules. | |
350 | * @parent: device cgroup's parent | |
351 | * returns: != 0 in case it's allowed, 0 otherwise | |
352 | */ | |
353 | static inline int may_allow_all(struct dev_cgroup *parent) | |
354 | { | |
64e10477 AR |
355 | if (!parent) |
356 | return 1; | |
4cef7299 AR |
357 | return parent->behavior == DEVCG_DEFAULT_ALLOW; |
358 | } | |
359 | ||
08ce5f16 | 360 | /* |
db9aeca9 | 361 | * Modify the exception list using allow/deny rules. |
08ce5f16 SH |
362 | * CAP_SYS_ADMIN is needed for this. It's at least separate from CAP_MKNOD |
363 | * so we can give a container CAP_MKNOD to let it create devices but not | |
db9aeca9 | 364 | * modify the exception list. |
08ce5f16 SH |
365 | * It seems likely we'll want to add a CAP_CONTAINER capability to allow |
366 | * us to also grant CAP_SYS_ADMIN to containers without giving away the | |
db9aeca9 | 367 | * device exception list controls, but for now we'll stick with CAP_SYS_ADMIN |
08ce5f16 SH |
368 | * |
369 | * Taking rules away is always allowed (given CAP_SYS_ADMIN). Granting | |
370 | * new access is only allowed if you're in the top-level cgroup, or your | |
371 | * parent cgroup has the access you're asking for. | |
372 | */ | |
f92523e3 PM |
373 | static int devcgroup_update_access(struct dev_cgroup *devcgroup, |
374 | int filetype, const char *buffer) | |
08ce5f16 | 375 | { |
f92523e3 | 376 | const char *b; |
26fd8405 AR |
377 | char temp[12]; /* 11 + 1 characters needed for a u32 */ |
378 | int count, rc; | |
db9aeca9 | 379 | struct dev_exception_item ex; |
4cef7299 | 380 | struct cgroup *p = devcgroup->css.cgroup; |
64e10477 | 381 | struct dev_cgroup *parent = NULL; |
08ce5f16 SH |
382 | |
383 | if (!capable(CAP_SYS_ADMIN)) | |
384 | return -EPERM; | |
385 | ||
64e10477 AR |
386 | if (p->parent) |
387 | parent = cgroup_to_devcgroup(p->parent); | |
388 | ||
db9aeca9 | 389 | memset(&ex, 0, sizeof(ex)); |
08ce5f16 SH |
390 | b = buffer; |
391 | ||
392 | switch (*b) { | |
393 | case 'a': | |
ad676077 AR |
394 | switch (filetype) { |
395 | case DEVCG_ALLOW: | |
4cef7299 | 396 | if (!may_allow_all(parent)) |
ad676077 | 397 | return -EPERM; |
db9aeca9 | 398 | dev_exception_clean(devcgroup); |
64e10477 AR |
399 | devcgroup->behavior = DEVCG_DEFAULT_ALLOW; |
400 | if (!parent) | |
401 | break; | |
402 | ||
4cef7299 AR |
403 | rc = dev_exceptions_copy(&devcgroup->exceptions, |
404 | &parent->exceptions); | |
405 | if (rc) | |
406 | return rc; | |
ad676077 AR |
407 | break; |
408 | case DEVCG_DENY: | |
db9aeca9 | 409 | dev_exception_clean(devcgroup); |
5b7aa7d5 | 410 | devcgroup->behavior = DEVCG_DEFAULT_DENY; |
ad676077 AR |
411 | break; |
412 | default: | |
413 | return -EINVAL; | |
414 | } | |
415 | return 0; | |
08ce5f16 | 416 | case 'b': |
db9aeca9 | 417 | ex.type = DEV_BLOCK; |
08ce5f16 SH |
418 | break; |
419 | case 'c': | |
db9aeca9 | 420 | ex.type = DEV_CHAR; |
08ce5f16 SH |
421 | break; |
422 | default: | |
f92523e3 | 423 | return -EINVAL; |
08ce5f16 SH |
424 | } |
425 | b++; | |
f92523e3 PM |
426 | if (!isspace(*b)) |
427 | return -EINVAL; | |
08ce5f16 SH |
428 | b++; |
429 | if (*b == '*') { | |
db9aeca9 | 430 | ex.major = ~0; |
08ce5f16 SH |
431 | b++; |
432 | } else if (isdigit(*b)) { | |
26fd8405 AR |
433 | memset(temp, 0, sizeof(temp)); |
434 | for (count = 0; count < sizeof(temp) - 1; count++) { | |
435 | temp[count] = *b; | |
436 | b++; | |
437 | if (!isdigit(*b)) | |
438 | break; | |
439 | } | |
440 | rc = kstrtou32(temp, 10, &ex.major); | |
441 | if (rc) | |
442 | return -EINVAL; | |
08ce5f16 | 443 | } else { |
f92523e3 | 444 | return -EINVAL; |
08ce5f16 | 445 | } |
f92523e3 PM |
446 | if (*b != ':') |
447 | return -EINVAL; | |
08ce5f16 SH |
448 | b++; |
449 | ||
450 | /* read minor */ | |
451 | if (*b == '*') { | |
db9aeca9 | 452 | ex.minor = ~0; |
08ce5f16 SH |
453 | b++; |
454 | } else if (isdigit(*b)) { | |
26fd8405 AR |
455 | memset(temp, 0, sizeof(temp)); |
456 | for (count = 0; count < sizeof(temp) - 1; count++) { | |
457 | temp[count] = *b; | |
458 | b++; | |
459 | if (!isdigit(*b)) | |
460 | break; | |
461 | } | |
462 | rc = kstrtou32(temp, 10, &ex.minor); | |
463 | if (rc) | |
464 | return -EINVAL; | |
08ce5f16 | 465 | } else { |
f92523e3 | 466 | return -EINVAL; |
08ce5f16 | 467 | } |
f92523e3 PM |
468 | if (!isspace(*b)) |
469 | return -EINVAL; | |
08ce5f16 SH |
470 | for (b++, count = 0; count < 3; count++, b++) { |
471 | switch (*b) { | |
472 | case 'r': | |
db9aeca9 | 473 | ex.access |= ACC_READ; |
08ce5f16 SH |
474 | break; |
475 | case 'w': | |
db9aeca9 | 476 | ex.access |= ACC_WRITE; |
08ce5f16 SH |
477 | break; |
478 | case 'm': | |
db9aeca9 | 479 | ex.access |= ACC_MKNOD; |
08ce5f16 SH |
480 | break; |
481 | case '\n': | |
482 | case '\0': | |
483 | count = 3; | |
484 | break; | |
485 | default: | |
f92523e3 | 486 | return -EINVAL; |
08ce5f16 SH |
487 | } |
488 | } | |
489 | ||
08ce5f16 SH |
490 | switch (filetype) { |
491 | case DEVCG_ALLOW: | |
db9aeca9 | 492 | if (!parent_has_perm(devcgroup, &ex)) |
f92523e3 | 493 | return -EPERM; |
ad676077 AR |
494 | /* |
495 | * If the default policy is to allow by default, try to remove | |
496 | * an matching exception instead. And be silent about it: we | |
497 | * don't want to break compatibility | |
498 | */ | |
5b7aa7d5 | 499 | if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) { |
db9aeca9 | 500 | dev_exception_rm(devcgroup, &ex); |
ad676077 AR |
501 | return 0; |
502 | } | |
db9aeca9 | 503 | return dev_exception_add(devcgroup, &ex); |
08ce5f16 | 504 | case DEVCG_DENY: |
ad676077 AR |
505 | /* |
506 | * If the default policy is to deny by default, try to remove | |
507 | * an matching exception instead. And be silent about it: we | |
508 | * don't want to break compatibility | |
509 | */ | |
5b7aa7d5 | 510 | if (devcgroup->behavior == DEVCG_DEFAULT_DENY) { |
db9aeca9 | 511 | dev_exception_rm(devcgroup, &ex); |
ad676077 AR |
512 | return 0; |
513 | } | |
db9aeca9 | 514 | return dev_exception_add(devcgroup, &ex); |
08ce5f16 | 515 | default: |
f92523e3 | 516 | return -EINVAL; |
08ce5f16 | 517 | } |
f92523e3 PM |
518 | return 0; |
519 | } | |
08ce5f16 | 520 | |
f92523e3 PM |
521 | static int devcgroup_access_write(struct cgroup *cgrp, struct cftype *cft, |
522 | const char *buffer) | |
523 | { | |
524 | int retval; | |
b4046f00 LZ |
525 | |
526 | mutex_lock(&devcgroup_mutex); | |
f92523e3 PM |
527 | retval = devcgroup_update_access(cgroup_to_devcgroup(cgrp), |
528 | cft->private, buffer); | |
b4046f00 | 529 | mutex_unlock(&devcgroup_mutex); |
08ce5f16 SH |
530 | return retval; |
531 | } | |
532 | ||
533 | static struct cftype dev_cgroup_files[] = { | |
534 | { | |
535 | .name = "allow", | |
f92523e3 | 536 | .write_string = devcgroup_access_write, |
08ce5f16 SH |
537 | .private = DEVCG_ALLOW, |
538 | }, | |
539 | { | |
540 | .name = "deny", | |
f92523e3 | 541 | .write_string = devcgroup_access_write, |
08ce5f16 SH |
542 | .private = DEVCG_DENY, |
543 | }, | |
29486df3 SH |
544 | { |
545 | .name = "list", | |
546 | .read_seq_string = devcgroup_seq_read, | |
547 | .private = DEVCG_LIST, | |
548 | }, | |
4baf6e33 | 549 | { } /* terminate */ |
08ce5f16 SH |
550 | }; |
551 | ||
08ce5f16 SH |
552 | struct cgroup_subsys devices_subsys = { |
553 | .name = "devices", | |
554 | .can_attach = devcgroup_can_attach, | |
555 | .create = devcgroup_create, | |
c5b60b5e | 556 | .destroy = devcgroup_destroy, |
08ce5f16 | 557 | .subsys_id = devices_subsys_id, |
4baf6e33 | 558 | .base_cftypes = dev_cgroup_files, |
8c7f6edb TH |
559 | |
560 | /* | |
561 | * While devices cgroup has the rudimentary hierarchy support which | |
562 | * checks the parent's restriction, it doesn't properly propagates | |
563 | * config changes in ancestors to their descendents. A child | |
564 | * should only be allowed to add more restrictions to the parent's | |
565 | * configuration. Fix it and remove the following. | |
566 | */ | |
567 | .broken_hierarchy = true, | |
08ce5f16 SH |
568 | }; |
569 | ||
ad676077 AR |
570 | /** |
571 | * __devcgroup_check_permission - checks if an inode operation is permitted | |
572 | * @dev_cgroup: the dev cgroup to be tested against | |
573 | * @type: device type | |
574 | * @major: device major number | |
575 | * @minor: device minor number | |
576 | * @access: combination of ACC_WRITE, ACC_READ and ACC_MKNOD | |
577 | * | |
578 | * returns 0 on success, -EPERM case the operation is not permitted | |
579 | */ | |
8c9506d1 | 580 | static int __devcgroup_check_permission(short type, u32 major, u32 minor, |
ad676077 | 581 | short access) |
08ce5f16 | 582 | { |
8c9506d1 | 583 | struct dev_cgroup *dev_cgroup; |
db9aeca9 | 584 | struct dev_exception_item ex; |
ad676077 | 585 | int rc; |
36fd71d2 | 586 | |
db9aeca9 AR |
587 | memset(&ex, 0, sizeof(ex)); |
588 | ex.type = type; | |
589 | ex.major = major; | |
590 | ex.minor = minor; | |
591 | ex.access = access; | |
36fd71d2 | 592 | |
ad676077 | 593 | rcu_read_lock(); |
8c9506d1 | 594 | dev_cgroup = task_devcgroup(current); |
db9aeca9 | 595 | rc = may_access(dev_cgroup, &ex); |
ad676077 | 596 | rcu_read_unlock(); |
cd500819 | 597 | |
ad676077 AR |
598 | if (!rc) |
599 | return -EPERM; | |
36fd71d2 | 600 | |
ad676077 AR |
601 | return 0; |
602 | } | |
08ce5f16 | 603 | |
ad676077 AR |
604 | int __devcgroup_inode_permission(struct inode *inode, int mask) |
605 | { | |
ad676077 AR |
606 | short type, access = 0; |
607 | ||
608 | if (S_ISBLK(inode->i_mode)) | |
609 | type = DEV_BLOCK; | |
610 | if (S_ISCHR(inode->i_mode)) | |
611 | type = DEV_CHAR; | |
612 | if (mask & MAY_WRITE) | |
613 | access |= ACC_WRITE; | |
614 | if (mask & MAY_READ) | |
615 | access |= ACC_READ; | |
616 | ||
8c9506d1 JS |
617 | return __devcgroup_check_permission(type, imajor(inode), iminor(inode), |
618 | access); | |
08ce5f16 SH |
619 | } |
620 | ||
621 | int devcgroup_inode_mknod(int mode, dev_t dev) | |
622 | { | |
ad676077 | 623 | short type; |
08ce5f16 | 624 | |
0b82ac37 SH |
625 | if (!S_ISBLK(mode) && !S_ISCHR(mode)) |
626 | return 0; | |
627 | ||
ad676077 AR |
628 | if (S_ISBLK(mode)) |
629 | type = DEV_BLOCK; | |
630 | else | |
631 | type = DEV_CHAR; | |
36fd71d2 | 632 | |
8c9506d1 JS |
633 | return __devcgroup_check_permission(type, MAJOR(dev), MINOR(dev), |
634 | ACC_MKNOD); | |
36fd71d2 | 635 | |
08ce5f16 | 636 | } |