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Commit | Line | Data |
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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
08ce5f16 | 2 | /* |
47c59803 | 3 | * device_cgroup.c - device cgroup subsystem |
08ce5f16 SH |
4 | * |
5 | * Copyright 2007 IBM Corp | |
6 | */ | |
7 | ||
8 | #include <linux/device_cgroup.h> | |
9 | #include <linux/cgroup.h> | |
10 | #include <linux/ctype.h> | |
11 | #include <linux/list.h> | |
12 | #include <linux/uaccess.h> | |
29486df3 | 13 | #include <linux/seq_file.h> |
5a0e3ad6 | 14 | #include <linux/slab.h> |
47c59803 | 15 | #include <linux/rcupdate.h> |
b4046f00 | 16 | #include <linux/mutex.h> |
08ce5f16 | 17 | |
b4046f00 LZ |
18 | static DEFINE_MUTEX(devcgroup_mutex); |
19 | ||
c39a2a30 AR |
20 | enum devcg_behavior { |
21 | DEVCG_DEFAULT_NONE, | |
22 | DEVCG_DEFAULT_ALLOW, | |
23 | DEVCG_DEFAULT_DENY, | |
24 | }; | |
25 | ||
08ce5f16 | 26 | /* |
db9aeca9 | 27 | * exception list locking rules: |
b4046f00 | 28 | * hold devcgroup_mutex for update/read. |
47c59803 | 29 | * hold rcu_read_lock() for read. |
08ce5f16 SH |
30 | */ |
31 | ||
db9aeca9 | 32 | struct dev_exception_item { |
08ce5f16 SH |
33 | u32 major, minor; |
34 | short type; | |
35 | short access; | |
36 | struct list_head list; | |
4efd1a1b | 37 | struct rcu_head rcu; |
08ce5f16 SH |
38 | }; |
39 | ||
40 | struct dev_cgroup { | |
41 | struct cgroup_subsys_state css; | |
db9aeca9 | 42 | struct list_head exceptions; |
c39a2a30 | 43 | enum devcg_behavior behavior; |
08ce5f16 SH |
44 | }; |
45 | ||
b66862f7 PE |
46 | static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s) |
47 | { | |
a7c6d554 | 48 | return s ? container_of(s, struct dev_cgroup, css) : NULL; |
b66862f7 PE |
49 | } |
50 | ||
f92523e3 PM |
51 | static inline struct dev_cgroup *task_devcgroup(struct task_struct *task) |
52 | { | |
073219e9 | 53 | return css_to_devcgroup(task_css(task, devices_cgrp_id)); |
f92523e3 PM |
54 | } |
55 | ||
08ce5f16 | 56 | /* |
b4046f00 | 57 | * called under devcgroup_mutex |
08ce5f16 | 58 | */ |
db9aeca9 | 59 | static int dev_exceptions_copy(struct list_head *dest, struct list_head *orig) |
08ce5f16 | 60 | { |
db9aeca9 | 61 | struct dev_exception_item *ex, *tmp, *new; |
08ce5f16 | 62 | |
4b1c7840 TH |
63 | lockdep_assert_held(&devcgroup_mutex); |
64 | ||
db9aeca9 AR |
65 | list_for_each_entry(ex, orig, list) { |
66 | new = kmemdup(ex, sizeof(*ex), GFP_KERNEL); | |
08ce5f16 SH |
67 | if (!new) |
68 | goto free_and_exit; | |
08ce5f16 SH |
69 | list_add_tail(&new->list, dest); |
70 | } | |
71 | ||
72 | return 0; | |
73 | ||
74 | free_and_exit: | |
db9aeca9 AR |
75 | list_for_each_entry_safe(ex, tmp, dest, list) { |
76 | list_del(&ex->list); | |
77 | kfree(ex); | |
08ce5f16 SH |
78 | } |
79 | return -ENOMEM; | |
80 | } | |
81 | ||
08ce5f16 | 82 | /* |
b4046f00 | 83 | * called under devcgroup_mutex |
08ce5f16 | 84 | */ |
db9aeca9 AR |
85 | static int dev_exception_add(struct dev_cgroup *dev_cgroup, |
86 | struct dev_exception_item *ex) | |
08ce5f16 | 87 | { |
db9aeca9 | 88 | struct dev_exception_item *excopy, *walk; |
08ce5f16 | 89 | |
4b1c7840 TH |
90 | lockdep_assert_held(&devcgroup_mutex); |
91 | ||
db9aeca9 AR |
92 | excopy = kmemdup(ex, sizeof(*ex), GFP_KERNEL); |
93 | if (!excopy) | |
08ce5f16 SH |
94 | return -ENOMEM; |
95 | ||
db9aeca9 AR |
96 | list_for_each_entry(walk, &dev_cgroup->exceptions, list) { |
97 | if (walk->type != ex->type) | |
d1ee2971 | 98 | continue; |
db9aeca9 | 99 | if (walk->major != ex->major) |
d1ee2971 | 100 | continue; |
db9aeca9 | 101 | if (walk->minor != ex->minor) |
d1ee2971 PE |
102 | continue; |
103 | ||
db9aeca9 AR |
104 | walk->access |= ex->access; |
105 | kfree(excopy); | |
106 | excopy = NULL; | |
d1ee2971 PE |
107 | } |
108 | ||
db9aeca9 AR |
109 | if (excopy != NULL) |
110 | list_add_tail_rcu(&excopy->list, &dev_cgroup->exceptions); | |
08ce5f16 SH |
111 | return 0; |
112 | } | |
113 | ||
114 | /* | |
b4046f00 | 115 | * called under devcgroup_mutex |
08ce5f16 | 116 | */ |
db9aeca9 AR |
117 | static void dev_exception_rm(struct dev_cgroup *dev_cgroup, |
118 | struct dev_exception_item *ex) | |
08ce5f16 | 119 | { |
db9aeca9 | 120 | struct dev_exception_item *walk, *tmp; |
08ce5f16 | 121 | |
4b1c7840 TH |
122 | lockdep_assert_held(&devcgroup_mutex); |
123 | ||
db9aeca9 AR |
124 | list_for_each_entry_safe(walk, tmp, &dev_cgroup->exceptions, list) { |
125 | if (walk->type != ex->type) | |
08ce5f16 | 126 | continue; |
db9aeca9 | 127 | if (walk->major != ex->major) |
08ce5f16 | 128 | continue; |
db9aeca9 | 129 | if (walk->minor != ex->minor) |
08ce5f16 SH |
130 | continue; |
131 | ||
db9aeca9 | 132 | walk->access &= ~ex->access; |
08ce5f16 | 133 | if (!walk->access) { |
4efd1a1b | 134 | list_del_rcu(&walk->list); |
6034f7e6 | 135 | kfree_rcu(walk, rcu); |
08ce5f16 SH |
136 | } |
137 | } | |
08ce5f16 SH |
138 | } |
139 | ||
53eb8c82 JS |
140 | static void __dev_exception_clean(struct dev_cgroup *dev_cgroup) |
141 | { | |
142 | struct dev_exception_item *ex, *tmp; | |
143 | ||
144 | list_for_each_entry_safe(ex, tmp, &dev_cgroup->exceptions, list) { | |
145 | list_del_rcu(&ex->list); | |
146 | kfree_rcu(ex, rcu); | |
147 | } | |
148 | } | |
149 | ||
868539a3 | 150 | /** |
db9aeca9 AR |
151 | * dev_exception_clean - frees all entries of the exception list |
152 | * @dev_cgroup: dev_cgroup with the exception list to be cleaned | |
868539a3 AR |
153 | * |
154 | * called under devcgroup_mutex | |
155 | */ | |
db9aeca9 | 156 | static void dev_exception_clean(struct dev_cgroup *dev_cgroup) |
868539a3 | 157 | { |
4b1c7840 TH |
158 | lockdep_assert_held(&devcgroup_mutex); |
159 | ||
53eb8c82 | 160 | __dev_exception_clean(dev_cgroup); |
868539a3 AR |
161 | } |
162 | ||
bd2953eb AR |
163 | static inline bool is_devcg_online(const struct dev_cgroup *devcg) |
164 | { | |
165 | return (devcg->behavior != DEVCG_DEFAULT_NONE); | |
166 | } | |
167 | ||
1909554c AR |
168 | /** |
169 | * devcgroup_online - initializes devcgroup's behavior and exceptions based on | |
170 | * parent's | |
eb95419b | 171 | * @css: css getting online |
1909554c AR |
172 | * returns 0 in case of success, error code otherwise |
173 | */ | |
eb95419b | 174 | static int devcgroup_online(struct cgroup_subsys_state *css) |
1909554c | 175 | { |
eb95419b | 176 | struct dev_cgroup *dev_cgroup = css_to_devcgroup(css); |
5c9d535b | 177 | struct dev_cgroup *parent_dev_cgroup = css_to_devcgroup(css->parent); |
1909554c AR |
178 | int ret = 0; |
179 | ||
180 | mutex_lock(&devcgroup_mutex); | |
1909554c AR |
181 | |
182 | if (parent_dev_cgroup == NULL) | |
183 | dev_cgroup->behavior = DEVCG_DEFAULT_ALLOW; | |
184 | else { | |
185 | ret = dev_exceptions_copy(&dev_cgroup->exceptions, | |
186 | &parent_dev_cgroup->exceptions); | |
187 | if (!ret) | |
188 | dev_cgroup->behavior = parent_dev_cgroup->behavior; | |
189 | } | |
190 | mutex_unlock(&devcgroup_mutex); | |
191 | ||
192 | return ret; | |
193 | } | |
194 | ||
eb95419b | 195 | static void devcgroup_offline(struct cgroup_subsys_state *css) |
1909554c | 196 | { |
eb95419b | 197 | struct dev_cgroup *dev_cgroup = css_to_devcgroup(css); |
1909554c AR |
198 | |
199 | mutex_lock(&devcgroup_mutex); | |
200 | dev_cgroup->behavior = DEVCG_DEFAULT_NONE; | |
201 | mutex_unlock(&devcgroup_mutex); | |
202 | } | |
203 | ||
08ce5f16 SH |
204 | /* |
205 | * called from kernel/cgroup.c with cgroup_lock() held. | |
206 | */ | |
eb95419b TH |
207 | static struct cgroup_subsys_state * |
208 | devcgroup_css_alloc(struct cgroup_subsys_state *parent_css) | |
08ce5f16 | 209 | { |
1909554c | 210 | struct dev_cgroup *dev_cgroup; |
08ce5f16 SH |
211 | |
212 | dev_cgroup = kzalloc(sizeof(*dev_cgroup), GFP_KERNEL); | |
213 | if (!dev_cgroup) | |
214 | return ERR_PTR(-ENOMEM); | |
db9aeca9 | 215 | INIT_LIST_HEAD(&dev_cgroup->exceptions); |
1909554c | 216 | dev_cgroup->behavior = DEVCG_DEFAULT_NONE; |
08ce5f16 | 217 | |
08ce5f16 SH |
218 | return &dev_cgroup->css; |
219 | } | |
220 | ||
eb95419b | 221 | static void devcgroup_css_free(struct cgroup_subsys_state *css) |
08ce5f16 | 222 | { |
eb95419b | 223 | struct dev_cgroup *dev_cgroup = css_to_devcgroup(css); |
08ce5f16 | 224 | |
53eb8c82 | 225 | __dev_exception_clean(dev_cgroup); |
08ce5f16 SH |
226 | kfree(dev_cgroup); |
227 | } | |
228 | ||
229 | #define DEVCG_ALLOW 1 | |
230 | #define DEVCG_DENY 2 | |
29486df3 SH |
231 | #define DEVCG_LIST 3 |
232 | ||
17d213f8 | 233 | #define MAJMINLEN 13 |
29486df3 | 234 | #define ACCLEN 4 |
08ce5f16 SH |
235 | |
236 | static void set_access(char *acc, short access) | |
237 | { | |
238 | int idx = 0; | |
29486df3 | 239 | memset(acc, 0, ACCLEN); |
67e306fd | 240 | if (access & DEVCG_ACC_READ) |
08ce5f16 | 241 | acc[idx++] = 'r'; |
67e306fd | 242 | if (access & DEVCG_ACC_WRITE) |
08ce5f16 | 243 | acc[idx++] = 'w'; |
67e306fd | 244 | if (access & DEVCG_ACC_MKNOD) |
08ce5f16 SH |
245 | acc[idx++] = 'm'; |
246 | } | |
247 | ||
248 | static char type_to_char(short type) | |
249 | { | |
67e306fd | 250 | if (type == DEVCG_DEV_ALL) |
08ce5f16 | 251 | return 'a'; |
67e306fd | 252 | if (type == DEVCG_DEV_CHAR) |
08ce5f16 | 253 | return 'c'; |
67e306fd | 254 | if (type == DEVCG_DEV_BLOCK) |
08ce5f16 SH |
255 | return 'b'; |
256 | return 'X'; | |
257 | } | |
258 | ||
29486df3 | 259 | static void set_majmin(char *str, unsigned m) |
08ce5f16 | 260 | { |
08ce5f16 | 261 | if (m == ~0) |
7759fc9d | 262 | strcpy(str, "*"); |
08ce5f16 | 263 | else |
7759fc9d | 264 | sprintf(str, "%u", m); |
08ce5f16 SH |
265 | } |
266 | ||
2da8ca82 | 267 | static int devcgroup_seq_show(struct seq_file *m, void *v) |
08ce5f16 | 268 | { |
2da8ca82 | 269 | struct dev_cgroup *devcgroup = css_to_devcgroup(seq_css(m)); |
db9aeca9 | 270 | struct dev_exception_item *ex; |
29486df3 | 271 | char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN]; |
08ce5f16 | 272 | |
4efd1a1b | 273 | rcu_read_lock(); |
ad676077 AR |
274 | /* |
275 | * To preserve the compatibility: | |
276 | * - Only show the "all devices" when the default policy is to allow | |
277 | * - List the exceptions in case the default policy is to deny | |
278 | * This way, the file remains as a "whitelist of devices" | |
279 | */ | |
5b7aa7d5 | 280 | if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) { |
67e306fd | 281 | set_access(acc, DEVCG_ACC_MASK); |
ad676077 AR |
282 | set_majmin(maj, ~0); |
283 | set_majmin(min, ~0); | |
67e306fd | 284 | seq_printf(m, "%c %s:%s %s\n", type_to_char(DEVCG_DEV_ALL), |
29486df3 | 285 | maj, min, acc); |
ad676077 | 286 | } else { |
db9aeca9 AR |
287 | list_for_each_entry_rcu(ex, &devcgroup->exceptions, list) { |
288 | set_access(acc, ex->access); | |
289 | set_majmin(maj, ex->major); | |
290 | set_majmin(min, ex->minor); | |
291 | seq_printf(m, "%c %s:%s %s\n", type_to_char(ex->type), | |
ad676077 AR |
292 | maj, min, acc); |
293 | } | |
08ce5f16 | 294 | } |
4efd1a1b | 295 | rcu_read_unlock(); |
08ce5f16 | 296 | |
29486df3 | 297 | return 0; |
08ce5f16 SH |
298 | } |
299 | ||
ad676077 | 300 | /** |
f5f3cf6f | 301 | * match_exception - iterates the exception list trying to find a complete match |
79d71974 | 302 | * @exceptions: list of exceptions |
67e306fd | 303 | * @type: device type (DEVCG_DEV_BLOCK or DEVCG_DEV_CHAR) |
79d71974 AR |
304 | * @major: device file major number, ~0 to match all |
305 | * @minor: device file minor number, ~0 to match all | |
67e306fd | 306 | * @access: permission mask (DEVCG_ACC_READ, DEVCG_ACC_WRITE, DEVCG_ACC_MKNOD) |
79d71974 | 307 | * |
f5f3cf6f AR |
308 | * It is considered a complete match if an exception is found that will |
309 | * contain the entire range of provided parameters. | |
310 | * | |
311 | * Return: true in case it matches an exception completely | |
08ce5f16 | 312 | */ |
79d71974 AR |
313 | static bool match_exception(struct list_head *exceptions, short type, |
314 | u32 major, u32 minor, short access) | |
08ce5f16 | 315 | { |
db9aeca9 | 316 | struct dev_exception_item *ex; |
08ce5f16 | 317 | |
79d71974 | 318 | list_for_each_entry_rcu(ex, exceptions, list) { |
67e306fd | 319 | if ((type & DEVCG_DEV_BLOCK) && !(ex->type & DEVCG_DEV_BLOCK)) |
79d71974 | 320 | continue; |
67e306fd | 321 | if ((type & DEVCG_DEV_CHAR) && !(ex->type & DEVCG_DEV_CHAR)) |
79d71974 AR |
322 | continue; |
323 | if (ex->major != ~0 && ex->major != major) | |
324 | continue; | |
325 | if (ex->minor != ~0 && ex->minor != minor) | |
326 | continue; | |
327 | /* provided access cannot have more than the exception rule */ | |
328 | if (access & (~ex->access)) | |
329 | continue; | |
330 | return true; | |
331 | } | |
332 | return false; | |
333 | } | |
334 | ||
335 | /** | |
f5f3cf6f | 336 | * match_exception_partial - iterates the exception list trying to find a partial match |
79d71974 | 337 | * @exceptions: list of exceptions |
67e306fd | 338 | * @type: device type (DEVCG_DEV_BLOCK or DEVCG_DEV_CHAR) |
79d71974 AR |
339 | * @major: device file major number, ~0 to match all |
340 | * @minor: device file minor number, ~0 to match all | |
67e306fd | 341 | * @access: permission mask (DEVCG_ACC_READ, DEVCG_ACC_WRITE, DEVCG_ACC_MKNOD) |
79d71974 | 342 | * |
f5f3cf6f AR |
343 | * It is considered a partial match if an exception's range is found to |
344 | * contain *any* of the devices specified by provided parameters. This is | |
345 | * used to make sure no extra access is being granted that is forbidden by | |
346 | * any of the exception list. | |
347 | * | |
348 | * Return: true in case the provided range mat matches an exception completely | |
79d71974 AR |
349 | */ |
350 | static bool match_exception_partial(struct list_head *exceptions, short type, | |
351 | u32 major, u32 minor, short access) | |
352 | { | |
353 | struct dev_exception_item *ex; | |
4b1c7840 | 354 | |
79d71974 | 355 | list_for_each_entry_rcu(ex, exceptions, list) { |
67e306fd | 356 | if ((type & DEVCG_DEV_BLOCK) && !(ex->type & DEVCG_DEV_BLOCK)) |
08ce5f16 | 357 | continue; |
67e306fd | 358 | if ((type & DEVCG_DEV_CHAR) && !(ex->type & DEVCG_DEV_CHAR)) |
08ce5f16 | 359 | continue; |
79d71974 AR |
360 | /* |
361 | * We must be sure that both the exception and the provided | |
362 | * range aren't masking all devices | |
363 | */ | |
364 | if (ex->major != ~0 && major != ~0 && ex->major != major) | |
08ce5f16 | 365 | continue; |
79d71974 | 366 | if (ex->minor != ~0 && minor != ~0 && ex->minor != minor) |
08ce5f16 | 367 | continue; |
79d71974 AR |
368 | /* |
369 | * In order to make sure the provided range isn't matching | |
370 | * an exception, all its access bits shouldn't match the | |
371 | * exception's access bits | |
372 | */ | |
373 | if (!(access & ex->access)) | |
08ce5f16 | 374 | continue; |
79d71974 | 375 | return true; |
08ce5f16 | 376 | } |
79d71974 AR |
377 | return false; |
378 | } | |
379 | ||
380 | /** | |
f5f3cf6f | 381 | * verify_new_ex - verifies if a new exception is allowed by parent cgroup's permissions |
79d71974 AR |
382 | * @dev_cgroup: dev cgroup to be tested against |
383 | * @refex: new exception | |
384 | * @behavior: behavior of the exception's dev_cgroup | |
f5f3cf6f AR |
385 | * |
386 | * This is used to make sure a child cgroup won't have more privileges | |
387 | * than its parent | |
79d71974 AR |
388 | */ |
389 | static bool verify_new_ex(struct dev_cgroup *dev_cgroup, | |
390 | struct dev_exception_item *refex, | |
391 | enum devcg_behavior behavior) | |
392 | { | |
393 | bool match = false; | |
394 | ||
f78f5b90 | 395 | RCU_LOCKDEP_WARN(!rcu_read_lock_held() && |
dc3a04d5 | 396 | !lockdep_is_held(&devcgroup_mutex), |
f78f5b90 | 397 | "device_cgroup:verify_new_ex called without proper synchronization"); |
ad676077 | 398 | |
c39a2a30 AR |
399 | if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) { |
400 | if (behavior == DEVCG_DEFAULT_ALLOW) { | |
79d71974 AR |
401 | /* |
402 | * new exception in the child doesn't matter, only | |
403 | * adding extra restrictions | |
404 | */ | |
c39a2a30 AR |
405 | return true; |
406 | } else { | |
79d71974 AR |
407 | /* |
408 | * new exception in the child will add more devices | |
409 | * that can be acessed, so it can't match any of | |
410 | * parent's exceptions, even slightly | |
411 | */ | |
412 | match = match_exception_partial(&dev_cgroup->exceptions, | |
413 | refex->type, | |
414 | refex->major, | |
415 | refex->minor, | |
416 | refex->access); | |
417 | ||
c39a2a30 | 418 | if (match) |
c39a2a30 | 419 | return false; |
26898fdf | 420 | return true; |
c39a2a30 | 421 | } |
26898fdf | 422 | } else { |
79d71974 AR |
423 | /* |
424 | * Only behavior == DEVCG_DEFAULT_DENY allowed here, therefore | |
425 | * the new exception will add access to more devices and must | |
426 | * be contained completely in an parent's exception to be | |
427 | * allowed | |
428 | */ | |
429 | match = match_exception(&dev_cgroup->exceptions, refex->type, | |
430 | refex->major, refex->minor, | |
431 | refex->access); | |
432 | ||
c39a2a30 AR |
433 | if (match) |
434 | /* parent has an exception that matches the proposed */ | |
26898fdf | 435 | return true; |
c39a2a30 AR |
436 | else |
437 | return false; | |
26898fdf AR |
438 | } |
439 | return false; | |
08ce5f16 SH |
440 | } |
441 | ||
442 | /* | |
443 | * parent_has_perm: | |
db9aeca9 | 444 | * when adding a new allow rule to a device exception list, the rule |
08ce5f16 SH |
445 | * must be allowed in the parent device |
446 | */ | |
f92523e3 | 447 | static int parent_has_perm(struct dev_cgroup *childcg, |
db9aeca9 | 448 | struct dev_exception_item *ex) |
08ce5f16 | 449 | { |
5c9d535b | 450 | struct dev_cgroup *parent = css_to_devcgroup(childcg->css.parent); |
08ce5f16 | 451 | |
63876986 | 452 | if (!parent) |
08ce5f16 | 453 | return 1; |
79d71974 | 454 | return verify_new_ex(parent, ex, childcg->behavior); |
08ce5f16 SH |
455 | } |
456 | ||
d2c2b11c AR |
457 | /** |
458 | * parent_allows_removal - verify if it's ok to remove an exception | |
459 | * @childcg: child cgroup from where the exception will be removed | |
460 | * @ex: exception being removed | |
461 | * | |
462 | * When removing an exception in cgroups with default ALLOW policy, it must | |
463 | * be checked if removing it will give the child cgroup more access than the | |
464 | * parent. | |
465 | * | |
466 | * Return: true if it's ok to remove exception, false otherwise | |
467 | */ | |
468 | static bool parent_allows_removal(struct dev_cgroup *childcg, | |
469 | struct dev_exception_item *ex) | |
470 | { | |
5c9d535b | 471 | struct dev_cgroup *parent = css_to_devcgroup(childcg->css.parent); |
d2c2b11c AR |
472 | |
473 | if (!parent) | |
474 | return true; | |
475 | ||
476 | /* It's always allowed to remove access to devices */ | |
477 | if (childcg->behavior == DEVCG_DEFAULT_DENY) | |
478 | return true; | |
479 | ||
480 | /* | |
481 | * Make sure you're not removing part or a whole exception existing in | |
482 | * the parent cgroup | |
483 | */ | |
484 | return !match_exception_partial(&parent->exceptions, ex->type, | |
485 | ex->major, ex->minor, ex->access); | |
486 | } | |
487 | ||
4cef7299 AR |
488 | /** |
489 | * may_allow_all - checks if it's possible to change the behavior to | |
490 | * allow based on parent's rules. | |
491 | * @parent: device cgroup's parent | |
492 | * returns: != 0 in case it's allowed, 0 otherwise | |
493 | */ | |
494 | static inline int may_allow_all(struct dev_cgroup *parent) | |
495 | { | |
64e10477 AR |
496 | if (!parent) |
497 | return 1; | |
4cef7299 AR |
498 | return parent->behavior == DEVCG_DEFAULT_ALLOW; |
499 | } | |
500 | ||
bd2953eb AR |
501 | /** |
502 | * revalidate_active_exceptions - walks through the active exception list and | |
503 | * revalidates the exceptions based on parent's | |
504 | * behavior and exceptions. The exceptions that | |
505 | * are no longer valid will be removed. | |
506 | * Called with devcgroup_mutex held. | |
507 | * @devcg: cgroup which exceptions will be checked | |
508 | * | |
509 | * This is one of the three key functions for hierarchy implementation. | |
510 | * This function is responsible for re-evaluating all the cgroup's active | |
511 | * exceptions due to a parent's exception change. | |
da82c92f | 512 | * Refer to Documentation/admin-guide/cgroup-v1/devices.rst for more details. |
bd2953eb AR |
513 | */ |
514 | static void revalidate_active_exceptions(struct dev_cgroup *devcg) | |
515 | { | |
516 | struct dev_exception_item *ex; | |
517 | struct list_head *this, *tmp; | |
518 | ||
519 | list_for_each_safe(this, tmp, &devcg->exceptions) { | |
520 | ex = container_of(this, struct dev_exception_item, list); | |
521 | if (!parent_has_perm(devcg, ex)) | |
522 | dev_exception_rm(devcg, ex); | |
523 | } | |
524 | } | |
525 | ||
bd2953eb AR |
526 | /** |
527 | * propagate_exception - propagates a new exception to the children | |
528 | * @devcg_root: device cgroup that added a new exception | |
529 | * @ex: new exception to be propagated | |
530 | * | |
531 | * returns: 0 in case of success, != 0 in case of error | |
532 | */ | |
533 | static int propagate_exception(struct dev_cgroup *devcg_root, | |
534 | struct dev_exception_item *ex) | |
535 | { | |
492eb21b | 536 | struct cgroup_subsys_state *pos; |
bd2953eb | 537 | int rc = 0; |
bd2953eb | 538 | |
d591fb56 | 539 | rcu_read_lock(); |
bd2953eb | 540 | |
492eb21b TH |
541 | css_for_each_descendant_pre(pos, &devcg_root->css) { |
542 | struct dev_cgroup *devcg = css_to_devcgroup(pos); | |
d591fb56 TH |
543 | |
544 | /* | |
545 | * Because devcgroup_mutex is held, no devcg will become | |
546 | * online or offline during the tree walk (see on/offline | |
547 | * methods), and online ones are safe to access outside RCU | |
548 | * read lock without bumping refcnt. | |
549 | */ | |
bd8815a6 | 550 | if (pos == &devcg_root->css || !is_devcg_online(devcg)) |
d591fb56 TH |
551 | continue; |
552 | ||
553 | rcu_read_unlock(); | |
bd2953eb AR |
554 | |
555 | /* | |
556 | * in case both root's behavior and devcg is allow, a new | |
557 | * restriction means adding to the exception list | |
558 | */ | |
559 | if (devcg_root->behavior == DEVCG_DEFAULT_ALLOW && | |
560 | devcg->behavior == DEVCG_DEFAULT_ALLOW) { | |
561 | rc = dev_exception_add(devcg, ex); | |
562 | if (rc) | |
0fcc4c8c | 563 | return rc; |
bd2953eb AR |
564 | } else { |
565 | /* | |
566 | * in the other possible cases: | |
567 | * root's behavior: allow, devcg's: deny | |
568 | * root's behavior: deny, devcg's: deny | |
569 | * the exception will be removed | |
570 | */ | |
571 | dev_exception_rm(devcg, ex); | |
572 | } | |
573 | revalidate_active_exceptions(devcg); | |
574 | ||
d591fb56 | 575 | rcu_read_lock(); |
bd2953eb | 576 | } |
d591fb56 TH |
577 | |
578 | rcu_read_unlock(); | |
bd2953eb AR |
579 | return rc; |
580 | } | |
581 | ||
08ce5f16 | 582 | /* |
db9aeca9 | 583 | * Modify the exception list using allow/deny rules. |
08ce5f16 SH |
584 | * CAP_SYS_ADMIN is needed for this. It's at least separate from CAP_MKNOD |
585 | * so we can give a container CAP_MKNOD to let it create devices but not | |
db9aeca9 | 586 | * modify the exception list. |
08ce5f16 SH |
587 | * It seems likely we'll want to add a CAP_CONTAINER capability to allow |
588 | * us to also grant CAP_SYS_ADMIN to containers without giving away the | |
db9aeca9 | 589 | * device exception list controls, but for now we'll stick with CAP_SYS_ADMIN |
08ce5f16 SH |
590 | * |
591 | * Taking rules away is always allowed (given CAP_SYS_ADMIN). Granting | |
592 | * new access is only allowed if you're in the top-level cgroup, or your | |
593 | * parent cgroup has the access you're asking for. | |
594 | */ | |
f92523e3 | 595 | static int devcgroup_update_access(struct dev_cgroup *devcgroup, |
4d3bb511 | 596 | int filetype, char *buffer) |
08ce5f16 | 597 | { |
f92523e3 | 598 | const char *b; |
26fd8405 | 599 | char temp[12]; /* 11 + 1 characters needed for a u32 */ |
c39a2a30 | 600 | int count, rc = 0; |
db9aeca9 | 601 | struct dev_exception_item ex; |
5c9d535b | 602 | struct dev_cgroup *parent = css_to_devcgroup(devcgroup->css.parent); |
08ce5f16 SH |
603 | |
604 | if (!capable(CAP_SYS_ADMIN)) | |
605 | return -EPERM; | |
606 | ||
db9aeca9 | 607 | memset(&ex, 0, sizeof(ex)); |
08ce5f16 SH |
608 | b = buffer; |
609 | ||
610 | switch (*b) { | |
611 | case 'a': | |
ad676077 AR |
612 | switch (filetype) { |
613 | case DEVCG_ALLOW: | |
7a3bb24f | 614 | if (css_has_online_children(&devcgroup->css)) |
bd2953eb AR |
615 | return -EINVAL; |
616 | ||
4cef7299 | 617 | if (!may_allow_all(parent)) |
ad676077 | 618 | return -EPERM; |
db9aeca9 | 619 | dev_exception_clean(devcgroup); |
64e10477 AR |
620 | devcgroup->behavior = DEVCG_DEFAULT_ALLOW; |
621 | if (!parent) | |
622 | break; | |
623 | ||
4cef7299 AR |
624 | rc = dev_exceptions_copy(&devcgroup->exceptions, |
625 | &parent->exceptions); | |
626 | if (rc) | |
627 | return rc; | |
ad676077 AR |
628 | break; |
629 | case DEVCG_DENY: | |
7a3bb24f | 630 | if (css_has_online_children(&devcgroup->css)) |
bd2953eb AR |
631 | return -EINVAL; |
632 | ||
db9aeca9 | 633 | dev_exception_clean(devcgroup); |
5b7aa7d5 | 634 | devcgroup->behavior = DEVCG_DEFAULT_DENY; |
ad676077 AR |
635 | break; |
636 | default: | |
637 | return -EINVAL; | |
638 | } | |
639 | return 0; | |
08ce5f16 | 640 | case 'b': |
67e306fd | 641 | ex.type = DEVCG_DEV_BLOCK; |
08ce5f16 SH |
642 | break; |
643 | case 'c': | |
67e306fd | 644 | ex.type = DEVCG_DEV_CHAR; |
08ce5f16 SH |
645 | break; |
646 | default: | |
f92523e3 | 647 | return -EINVAL; |
08ce5f16 SH |
648 | } |
649 | b++; | |
f92523e3 PM |
650 | if (!isspace(*b)) |
651 | return -EINVAL; | |
08ce5f16 SH |
652 | b++; |
653 | if (*b == '*') { | |
db9aeca9 | 654 | ex.major = ~0; |
08ce5f16 SH |
655 | b++; |
656 | } else if (isdigit(*b)) { | |
26fd8405 AR |
657 | memset(temp, 0, sizeof(temp)); |
658 | for (count = 0; count < sizeof(temp) - 1; count++) { | |
659 | temp[count] = *b; | |
660 | b++; | |
661 | if (!isdigit(*b)) | |
662 | break; | |
663 | } | |
664 | rc = kstrtou32(temp, 10, &ex.major); | |
665 | if (rc) | |
666 | return -EINVAL; | |
08ce5f16 | 667 | } else { |
f92523e3 | 668 | return -EINVAL; |
08ce5f16 | 669 | } |
f92523e3 PM |
670 | if (*b != ':') |
671 | return -EINVAL; | |
08ce5f16 SH |
672 | b++; |
673 | ||
674 | /* read minor */ | |
675 | if (*b == '*') { | |
db9aeca9 | 676 | ex.minor = ~0; |
08ce5f16 SH |
677 | b++; |
678 | } else if (isdigit(*b)) { | |
26fd8405 AR |
679 | memset(temp, 0, sizeof(temp)); |
680 | for (count = 0; count < sizeof(temp) - 1; count++) { | |
681 | temp[count] = *b; | |
682 | b++; | |
683 | if (!isdigit(*b)) | |
684 | break; | |
685 | } | |
686 | rc = kstrtou32(temp, 10, &ex.minor); | |
687 | if (rc) | |
688 | return -EINVAL; | |
08ce5f16 | 689 | } else { |
f92523e3 | 690 | return -EINVAL; |
08ce5f16 | 691 | } |
f92523e3 PM |
692 | if (!isspace(*b)) |
693 | return -EINVAL; | |
08ce5f16 SH |
694 | for (b++, count = 0; count < 3; count++, b++) { |
695 | switch (*b) { | |
696 | case 'r': | |
67e306fd | 697 | ex.access |= DEVCG_ACC_READ; |
08ce5f16 SH |
698 | break; |
699 | case 'w': | |
67e306fd | 700 | ex.access |= DEVCG_ACC_WRITE; |
08ce5f16 SH |
701 | break; |
702 | case 'm': | |
67e306fd | 703 | ex.access |= DEVCG_ACC_MKNOD; |
08ce5f16 SH |
704 | break; |
705 | case '\n': | |
706 | case '\0': | |
707 | count = 3; | |
708 | break; | |
709 | default: | |
f92523e3 | 710 | return -EINVAL; |
08ce5f16 SH |
711 | } |
712 | } | |
713 | ||
08ce5f16 SH |
714 | switch (filetype) { |
715 | case DEVCG_ALLOW: | |
ad676077 AR |
716 | /* |
717 | * If the default policy is to allow by default, try to remove | |
718 | * an matching exception instead. And be silent about it: we | |
719 | * don't want to break compatibility | |
720 | */ | |
5b7aa7d5 | 721 | if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) { |
d2c2b11c AR |
722 | /* Check if the parent allows removing it first */ |
723 | if (!parent_allows_removal(devcgroup, &ex)) | |
724 | return -EPERM; | |
db9aeca9 | 725 | dev_exception_rm(devcgroup, &ex); |
d2c2b11c | 726 | break; |
ad676077 | 727 | } |
d2c2b11c AR |
728 | |
729 | if (!parent_has_perm(devcgroup, &ex)) | |
730 | return -EPERM; | |
bd2953eb AR |
731 | rc = dev_exception_add(devcgroup, &ex); |
732 | break; | |
08ce5f16 | 733 | case DEVCG_DENY: |
ad676077 AR |
734 | /* |
735 | * If the default policy is to deny by default, try to remove | |
736 | * an matching exception instead. And be silent about it: we | |
737 | * don't want to break compatibility | |
738 | */ | |
bd2953eb | 739 | if (devcgroup->behavior == DEVCG_DEFAULT_DENY) |
db9aeca9 | 740 | dev_exception_rm(devcgroup, &ex); |
bd2953eb AR |
741 | else |
742 | rc = dev_exception_add(devcgroup, &ex); | |
743 | ||
744 | if (rc) | |
745 | break; | |
746 | /* we only propagate new restrictions */ | |
747 | rc = propagate_exception(devcgroup, &ex); | |
748 | break; | |
08ce5f16 | 749 | default: |
bd2953eb | 750 | rc = -EINVAL; |
08ce5f16 | 751 | } |
bd2953eb | 752 | return rc; |
f92523e3 | 753 | } |
08ce5f16 | 754 | |
451af504 TH |
755 | static ssize_t devcgroup_access_write(struct kernfs_open_file *of, |
756 | char *buf, size_t nbytes, loff_t off) | |
f92523e3 PM |
757 | { |
758 | int retval; | |
b4046f00 LZ |
759 | |
760 | mutex_lock(&devcgroup_mutex); | |
451af504 TH |
761 | retval = devcgroup_update_access(css_to_devcgroup(of_css(of)), |
762 | of_cft(of)->private, strstrip(buf)); | |
b4046f00 | 763 | mutex_unlock(&devcgroup_mutex); |
451af504 | 764 | return retval ?: nbytes; |
08ce5f16 SH |
765 | } |
766 | ||
767 | static struct cftype dev_cgroup_files[] = { | |
768 | { | |
769 | .name = "allow", | |
451af504 | 770 | .write = devcgroup_access_write, |
08ce5f16 SH |
771 | .private = DEVCG_ALLOW, |
772 | }, | |
773 | { | |
774 | .name = "deny", | |
451af504 | 775 | .write = devcgroup_access_write, |
08ce5f16 SH |
776 | .private = DEVCG_DENY, |
777 | }, | |
29486df3 SH |
778 | { |
779 | .name = "list", | |
2da8ca82 | 780 | .seq_show = devcgroup_seq_show, |
29486df3 SH |
781 | .private = DEVCG_LIST, |
782 | }, | |
4baf6e33 | 783 | { } /* terminate */ |
08ce5f16 SH |
784 | }; |
785 | ||
073219e9 | 786 | struct cgroup_subsys devices_cgrp_subsys = { |
92fb9748 TH |
787 | .css_alloc = devcgroup_css_alloc, |
788 | .css_free = devcgroup_css_free, | |
1909554c AR |
789 | .css_online = devcgroup_online, |
790 | .css_offline = devcgroup_offline, | |
5577964e | 791 | .legacy_cftypes = dev_cgroup_files, |
08ce5f16 SH |
792 | }; |
793 | ||
ad676077 AR |
794 | /** |
795 | * __devcgroup_check_permission - checks if an inode operation is permitted | |
796 | * @dev_cgroup: the dev cgroup to be tested against | |
797 | * @type: device type | |
798 | * @major: device major number | |
799 | * @minor: device minor number | |
67e306fd | 800 | * @access: combination of DEVCG_ACC_WRITE, DEVCG_ACC_READ and DEVCG_ACC_MKNOD |
ad676077 AR |
801 | * |
802 | * returns 0 on success, -EPERM case the operation is not permitted | |
803 | */ | |
ecf8fecb RG |
804 | int __devcgroup_check_permission(short type, u32 major, u32 minor, |
805 | short access) | |
08ce5f16 | 806 | { |
8c9506d1 | 807 | struct dev_cgroup *dev_cgroup; |
79d71974 | 808 | bool rc; |
36fd71d2 | 809 | |
ad676077 | 810 | rcu_read_lock(); |
8c9506d1 | 811 | dev_cgroup = task_devcgroup(current); |
79d71974 AR |
812 | if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) |
813 | /* Can't match any of the exceptions, even partially */ | |
814 | rc = !match_exception_partial(&dev_cgroup->exceptions, | |
815 | type, major, minor, access); | |
816 | else | |
817 | /* Need to match completely one exception to be allowed */ | |
818 | rc = match_exception(&dev_cgroup->exceptions, type, major, | |
819 | minor, access); | |
ad676077 | 820 | rcu_read_unlock(); |
cd500819 | 821 | |
ad676077 AR |
822 | if (!rc) |
823 | return -EPERM; | |
36fd71d2 | 824 | |
ad676077 AR |
825 | return 0; |
826 | } |