Commit | Line | Data |
---|---|---|
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 | ||
aef2feda | 8 | #include <linux/bpf-cgroup.h> |
08ce5f16 SH |
9 | #include <linux/device_cgroup.h> |
10 | #include <linux/cgroup.h> | |
11 | #include <linux/ctype.h> | |
12 | #include <linux/list.h> | |
13 | #include <linux/uaccess.h> | |
29486df3 | 14 | #include <linux/seq_file.h> |
5a0e3ad6 | 15 | #include <linux/slab.h> |
47c59803 | 16 | #include <linux/rcupdate.h> |
b4046f00 | 17 | #include <linux/mutex.h> |
08ce5f16 | 18 | |
eec8fd02 OU |
19 | #ifdef CONFIG_CGROUP_DEVICE |
20 | ||
b4046f00 LZ |
21 | static DEFINE_MUTEX(devcgroup_mutex); |
22 | ||
c39a2a30 AR |
23 | enum devcg_behavior { |
24 | DEVCG_DEFAULT_NONE, | |
25 | DEVCG_DEFAULT_ALLOW, | |
26 | DEVCG_DEFAULT_DENY, | |
27 | }; | |
28 | ||
08ce5f16 | 29 | /* |
db9aeca9 | 30 | * exception list locking rules: |
b4046f00 | 31 | * hold devcgroup_mutex for update/read. |
47c59803 | 32 | * hold rcu_read_lock() for read. |
08ce5f16 SH |
33 | */ |
34 | ||
db9aeca9 | 35 | struct dev_exception_item { |
08ce5f16 SH |
36 | u32 major, minor; |
37 | short type; | |
38 | short access; | |
39 | struct list_head list; | |
4efd1a1b | 40 | struct rcu_head rcu; |
08ce5f16 SH |
41 | }; |
42 | ||
43 | struct dev_cgroup { | |
44 | struct cgroup_subsys_state css; | |
db9aeca9 | 45 | struct list_head exceptions; |
c39a2a30 | 46 | enum devcg_behavior behavior; |
08ce5f16 SH |
47 | }; |
48 | ||
b66862f7 PE |
49 | static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s) |
50 | { | |
a7c6d554 | 51 | return s ? container_of(s, struct dev_cgroup, css) : NULL; |
b66862f7 PE |
52 | } |
53 | ||
f92523e3 PM |
54 | static inline struct dev_cgroup *task_devcgroup(struct task_struct *task) |
55 | { | |
073219e9 | 56 | return css_to_devcgroup(task_css(task, devices_cgrp_id)); |
f92523e3 PM |
57 | } |
58 | ||
08ce5f16 | 59 | /* |
b4046f00 | 60 | * called under devcgroup_mutex |
08ce5f16 | 61 | */ |
db9aeca9 | 62 | static int dev_exceptions_copy(struct list_head *dest, struct list_head *orig) |
08ce5f16 | 63 | { |
db9aeca9 | 64 | struct dev_exception_item *ex, *tmp, *new; |
08ce5f16 | 65 | |
4b1c7840 TH |
66 | lockdep_assert_held(&devcgroup_mutex); |
67 | ||
db9aeca9 AR |
68 | list_for_each_entry(ex, orig, list) { |
69 | new = kmemdup(ex, sizeof(*ex), GFP_KERNEL); | |
08ce5f16 SH |
70 | if (!new) |
71 | goto free_and_exit; | |
08ce5f16 SH |
72 | list_add_tail(&new->list, dest); |
73 | } | |
74 | ||
75 | return 0; | |
76 | ||
77 | free_and_exit: | |
db9aeca9 AR |
78 | list_for_each_entry_safe(ex, tmp, dest, list) { |
79 | list_del(&ex->list); | |
80 | kfree(ex); | |
08ce5f16 SH |
81 | } |
82 | return -ENOMEM; | |
83 | } | |
84 | ||
e68bfbd3 WW |
85 | static void dev_exceptions_move(struct list_head *dest, struct list_head *orig) |
86 | { | |
87 | struct dev_exception_item *ex, *tmp; | |
88 | ||
89 | lockdep_assert_held(&devcgroup_mutex); | |
90 | ||
91 | list_for_each_entry_safe(ex, tmp, orig, list) { | |
92 | list_move_tail(&ex->list, dest); | |
93 | } | |
94 | } | |
95 | ||
08ce5f16 | 96 | /* |
b4046f00 | 97 | * called under devcgroup_mutex |
08ce5f16 | 98 | */ |
db9aeca9 AR |
99 | static int dev_exception_add(struct dev_cgroup *dev_cgroup, |
100 | struct dev_exception_item *ex) | |
08ce5f16 | 101 | { |
db9aeca9 | 102 | struct dev_exception_item *excopy, *walk; |
08ce5f16 | 103 | |
4b1c7840 TH |
104 | lockdep_assert_held(&devcgroup_mutex); |
105 | ||
db9aeca9 AR |
106 | excopy = kmemdup(ex, sizeof(*ex), GFP_KERNEL); |
107 | if (!excopy) | |
08ce5f16 SH |
108 | return -ENOMEM; |
109 | ||
db9aeca9 AR |
110 | list_for_each_entry(walk, &dev_cgroup->exceptions, list) { |
111 | if (walk->type != ex->type) | |
d1ee2971 | 112 | continue; |
db9aeca9 | 113 | if (walk->major != ex->major) |
d1ee2971 | 114 | continue; |
db9aeca9 | 115 | if (walk->minor != ex->minor) |
d1ee2971 PE |
116 | continue; |
117 | ||
db9aeca9 AR |
118 | walk->access |= ex->access; |
119 | kfree(excopy); | |
120 | excopy = NULL; | |
d1ee2971 PE |
121 | } |
122 | ||
db9aeca9 AR |
123 | if (excopy != NULL) |
124 | list_add_tail_rcu(&excopy->list, &dev_cgroup->exceptions); | |
08ce5f16 SH |
125 | return 0; |
126 | } | |
127 | ||
128 | /* | |
b4046f00 | 129 | * called under devcgroup_mutex |
08ce5f16 | 130 | */ |
db9aeca9 AR |
131 | static void dev_exception_rm(struct dev_cgroup *dev_cgroup, |
132 | struct dev_exception_item *ex) | |
08ce5f16 | 133 | { |
db9aeca9 | 134 | struct dev_exception_item *walk, *tmp; |
08ce5f16 | 135 | |
4b1c7840 TH |
136 | lockdep_assert_held(&devcgroup_mutex); |
137 | ||
db9aeca9 AR |
138 | list_for_each_entry_safe(walk, tmp, &dev_cgroup->exceptions, list) { |
139 | if (walk->type != ex->type) | |
08ce5f16 | 140 | continue; |
db9aeca9 | 141 | if (walk->major != ex->major) |
08ce5f16 | 142 | continue; |
db9aeca9 | 143 | if (walk->minor != ex->minor) |
08ce5f16 SH |
144 | continue; |
145 | ||
db9aeca9 | 146 | walk->access &= ~ex->access; |
08ce5f16 | 147 | if (!walk->access) { |
4efd1a1b | 148 | list_del_rcu(&walk->list); |
6034f7e6 | 149 | kfree_rcu(walk, rcu); |
08ce5f16 SH |
150 | } |
151 | } | |
08ce5f16 SH |
152 | } |
153 | ||
53eb8c82 JS |
154 | static void __dev_exception_clean(struct dev_cgroup *dev_cgroup) |
155 | { | |
156 | struct dev_exception_item *ex, *tmp; | |
157 | ||
158 | list_for_each_entry_safe(ex, tmp, &dev_cgroup->exceptions, list) { | |
159 | list_del_rcu(&ex->list); | |
160 | kfree_rcu(ex, rcu); | |
161 | } | |
162 | } | |
163 | ||
868539a3 | 164 | /** |
db9aeca9 AR |
165 | * dev_exception_clean - frees all entries of the exception list |
166 | * @dev_cgroup: dev_cgroup with the exception list to be cleaned | |
868539a3 AR |
167 | * |
168 | * called under devcgroup_mutex | |
169 | */ | |
db9aeca9 | 170 | static void dev_exception_clean(struct dev_cgroup *dev_cgroup) |
868539a3 | 171 | { |
4b1c7840 TH |
172 | lockdep_assert_held(&devcgroup_mutex); |
173 | ||
53eb8c82 | 174 | __dev_exception_clean(dev_cgroup); |
868539a3 AR |
175 | } |
176 | ||
bd2953eb AR |
177 | static inline bool is_devcg_online(const struct dev_cgroup *devcg) |
178 | { | |
179 | return (devcg->behavior != DEVCG_DEFAULT_NONE); | |
180 | } | |
181 | ||
1909554c AR |
182 | /** |
183 | * devcgroup_online - initializes devcgroup's behavior and exceptions based on | |
184 | * parent's | |
eb95419b | 185 | * @css: css getting online |
1909554c AR |
186 | * returns 0 in case of success, error code otherwise |
187 | */ | |
eb95419b | 188 | static int devcgroup_online(struct cgroup_subsys_state *css) |
1909554c | 189 | { |
eb95419b | 190 | struct dev_cgroup *dev_cgroup = css_to_devcgroup(css); |
5c9d535b | 191 | struct dev_cgroup *parent_dev_cgroup = css_to_devcgroup(css->parent); |
1909554c AR |
192 | int ret = 0; |
193 | ||
194 | mutex_lock(&devcgroup_mutex); | |
1909554c AR |
195 | |
196 | if (parent_dev_cgroup == NULL) | |
197 | dev_cgroup->behavior = DEVCG_DEFAULT_ALLOW; | |
198 | else { | |
199 | ret = dev_exceptions_copy(&dev_cgroup->exceptions, | |
200 | &parent_dev_cgroup->exceptions); | |
201 | if (!ret) | |
202 | dev_cgroup->behavior = parent_dev_cgroup->behavior; | |
203 | } | |
204 | mutex_unlock(&devcgroup_mutex); | |
205 | ||
206 | return ret; | |
207 | } | |
208 | ||
eb95419b | 209 | static void devcgroup_offline(struct cgroup_subsys_state *css) |
1909554c | 210 | { |
eb95419b | 211 | struct dev_cgroup *dev_cgroup = css_to_devcgroup(css); |
1909554c AR |
212 | |
213 | mutex_lock(&devcgroup_mutex); | |
214 | dev_cgroup->behavior = DEVCG_DEFAULT_NONE; | |
215 | mutex_unlock(&devcgroup_mutex); | |
216 | } | |
217 | ||
08ce5f16 | 218 | /* |
f89f8e16 | 219 | * called from kernel/cgroup/cgroup.c with cgroup_lock() held. |
08ce5f16 | 220 | */ |
eb95419b TH |
221 | static struct cgroup_subsys_state * |
222 | devcgroup_css_alloc(struct cgroup_subsys_state *parent_css) | |
08ce5f16 | 223 | { |
1909554c | 224 | struct dev_cgroup *dev_cgroup; |
08ce5f16 SH |
225 | |
226 | dev_cgroup = kzalloc(sizeof(*dev_cgroup), GFP_KERNEL); | |
227 | if (!dev_cgroup) | |
228 | return ERR_PTR(-ENOMEM); | |
db9aeca9 | 229 | INIT_LIST_HEAD(&dev_cgroup->exceptions); |
1909554c | 230 | dev_cgroup->behavior = DEVCG_DEFAULT_NONE; |
08ce5f16 | 231 | |
08ce5f16 SH |
232 | return &dev_cgroup->css; |
233 | } | |
234 | ||
eb95419b | 235 | static void devcgroup_css_free(struct cgroup_subsys_state *css) |
08ce5f16 | 236 | { |
eb95419b | 237 | struct dev_cgroup *dev_cgroup = css_to_devcgroup(css); |
08ce5f16 | 238 | |
53eb8c82 | 239 | __dev_exception_clean(dev_cgroup); |
08ce5f16 SH |
240 | kfree(dev_cgroup); |
241 | } | |
242 | ||
243 | #define DEVCG_ALLOW 1 | |
244 | #define DEVCG_DENY 2 | |
29486df3 SH |
245 | #define DEVCG_LIST 3 |
246 | ||
17d213f8 | 247 | #define MAJMINLEN 13 |
29486df3 | 248 | #define ACCLEN 4 |
08ce5f16 SH |
249 | |
250 | static void set_access(char *acc, short access) | |
251 | { | |
252 | int idx = 0; | |
29486df3 | 253 | memset(acc, 0, ACCLEN); |
67e306fd | 254 | if (access & DEVCG_ACC_READ) |
08ce5f16 | 255 | acc[idx++] = 'r'; |
67e306fd | 256 | if (access & DEVCG_ACC_WRITE) |
08ce5f16 | 257 | acc[idx++] = 'w'; |
67e306fd | 258 | if (access & DEVCG_ACC_MKNOD) |
08ce5f16 SH |
259 | acc[idx++] = 'm'; |
260 | } | |
261 | ||
262 | static char type_to_char(short type) | |
263 | { | |
67e306fd | 264 | if (type == DEVCG_DEV_ALL) |
08ce5f16 | 265 | return 'a'; |
67e306fd | 266 | if (type == DEVCG_DEV_CHAR) |
08ce5f16 | 267 | return 'c'; |
67e306fd | 268 | if (type == DEVCG_DEV_BLOCK) |
08ce5f16 SH |
269 | return 'b'; |
270 | return 'X'; | |
271 | } | |
272 | ||
29486df3 | 273 | static void set_majmin(char *str, unsigned m) |
08ce5f16 | 274 | { |
08ce5f16 | 275 | if (m == ~0) |
7759fc9d | 276 | strcpy(str, "*"); |
08ce5f16 | 277 | else |
7759fc9d | 278 | sprintf(str, "%u", m); |
08ce5f16 SH |
279 | } |
280 | ||
2da8ca82 | 281 | static int devcgroup_seq_show(struct seq_file *m, void *v) |
08ce5f16 | 282 | { |
2da8ca82 | 283 | struct dev_cgroup *devcgroup = css_to_devcgroup(seq_css(m)); |
db9aeca9 | 284 | struct dev_exception_item *ex; |
29486df3 | 285 | char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN]; |
08ce5f16 | 286 | |
4efd1a1b | 287 | rcu_read_lock(); |
ad676077 AR |
288 | /* |
289 | * To preserve the compatibility: | |
290 | * - Only show the "all devices" when the default policy is to allow | |
291 | * - List the exceptions in case the default policy is to deny | |
292 | * This way, the file remains as a "whitelist of devices" | |
293 | */ | |
5b7aa7d5 | 294 | if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) { |
67e306fd | 295 | set_access(acc, DEVCG_ACC_MASK); |
ad676077 AR |
296 | set_majmin(maj, ~0); |
297 | set_majmin(min, ~0); | |
67e306fd | 298 | seq_printf(m, "%c %s:%s %s\n", type_to_char(DEVCG_DEV_ALL), |
29486df3 | 299 | maj, min, acc); |
ad676077 | 300 | } else { |
db9aeca9 AR |
301 | list_for_each_entry_rcu(ex, &devcgroup->exceptions, list) { |
302 | set_access(acc, ex->access); | |
303 | set_majmin(maj, ex->major); | |
304 | set_majmin(min, ex->minor); | |
305 | seq_printf(m, "%c %s:%s %s\n", type_to_char(ex->type), | |
ad676077 AR |
306 | maj, min, acc); |
307 | } | |
08ce5f16 | 308 | } |
4efd1a1b | 309 | rcu_read_unlock(); |
08ce5f16 | 310 | |
29486df3 | 311 | return 0; |
08ce5f16 SH |
312 | } |
313 | ||
ad676077 | 314 | /** |
f5f3cf6f | 315 | * match_exception - iterates the exception list trying to find a complete match |
79d71974 | 316 | * @exceptions: list of exceptions |
67e306fd | 317 | * @type: device type (DEVCG_DEV_BLOCK or DEVCG_DEV_CHAR) |
79d71974 AR |
318 | * @major: device file major number, ~0 to match all |
319 | * @minor: device file minor number, ~0 to match all | |
67e306fd | 320 | * @access: permission mask (DEVCG_ACC_READ, DEVCG_ACC_WRITE, DEVCG_ACC_MKNOD) |
79d71974 | 321 | * |
f5f3cf6f AR |
322 | * It is considered a complete match if an exception is found that will |
323 | * contain the entire range of provided parameters. | |
324 | * | |
325 | * Return: true in case it matches an exception completely | |
08ce5f16 | 326 | */ |
79d71974 AR |
327 | static bool match_exception(struct list_head *exceptions, short type, |
328 | u32 major, u32 minor, short access) | |
08ce5f16 | 329 | { |
db9aeca9 | 330 | struct dev_exception_item *ex; |
08ce5f16 | 331 | |
79d71974 | 332 | list_for_each_entry_rcu(ex, exceptions, list) { |
67e306fd | 333 | if ((type & DEVCG_DEV_BLOCK) && !(ex->type & DEVCG_DEV_BLOCK)) |
79d71974 | 334 | continue; |
67e306fd | 335 | if ((type & DEVCG_DEV_CHAR) && !(ex->type & DEVCG_DEV_CHAR)) |
79d71974 AR |
336 | continue; |
337 | if (ex->major != ~0 && ex->major != major) | |
338 | continue; | |
339 | if (ex->minor != ~0 && ex->minor != minor) | |
340 | continue; | |
341 | /* provided access cannot have more than the exception rule */ | |
342 | if (access & (~ex->access)) | |
343 | continue; | |
344 | return true; | |
345 | } | |
346 | return false; | |
347 | } | |
348 | ||
349 | /** | |
f5f3cf6f | 350 | * match_exception_partial - iterates the exception list trying to find a partial match |
79d71974 | 351 | * @exceptions: list of exceptions |
67e306fd | 352 | * @type: device type (DEVCG_DEV_BLOCK or DEVCG_DEV_CHAR) |
79d71974 AR |
353 | * @major: device file major number, ~0 to match all |
354 | * @minor: device file minor number, ~0 to match all | |
67e306fd | 355 | * @access: permission mask (DEVCG_ACC_READ, DEVCG_ACC_WRITE, DEVCG_ACC_MKNOD) |
79d71974 | 356 | * |
f5f3cf6f AR |
357 | * It is considered a partial match if an exception's range is found to |
358 | * contain *any* of the devices specified by provided parameters. This is | |
359 | * used to make sure no extra access is being granted that is forbidden by | |
360 | * any of the exception list. | |
361 | * | |
362 | * Return: true in case the provided range mat matches an exception completely | |
79d71974 AR |
363 | */ |
364 | static bool match_exception_partial(struct list_head *exceptions, short type, | |
365 | u32 major, u32 minor, short access) | |
366 | { | |
367 | struct dev_exception_item *ex; | |
4b1c7840 | 368 | |
bc62d68e AG |
369 | list_for_each_entry_rcu(ex, exceptions, list, |
370 | lockdep_is_held(&devcgroup_mutex)) { | |
67e306fd | 371 | if ((type & DEVCG_DEV_BLOCK) && !(ex->type & DEVCG_DEV_BLOCK)) |
08ce5f16 | 372 | continue; |
67e306fd | 373 | if ((type & DEVCG_DEV_CHAR) && !(ex->type & DEVCG_DEV_CHAR)) |
08ce5f16 | 374 | continue; |
79d71974 AR |
375 | /* |
376 | * We must be sure that both the exception and the provided | |
377 | * range aren't masking all devices | |
378 | */ | |
379 | if (ex->major != ~0 && major != ~0 && ex->major != major) | |
08ce5f16 | 380 | continue; |
79d71974 | 381 | if (ex->minor != ~0 && minor != ~0 && ex->minor != minor) |
08ce5f16 | 382 | continue; |
79d71974 AR |
383 | /* |
384 | * In order to make sure the provided range isn't matching | |
385 | * an exception, all its access bits shouldn't match the | |
386 | * exception's access bits | |
387 | */ | |
388 | if (!(access & ex->access)) | |
08ce5f16 | 389 | continue; |
79d71974 | 390 | return true; |
08ce5f16 | 391 | } |
79d71974 AR |
392 | return false; |
393 | } | |
394 | ||
395 | /** | |
f5f3cf6f | 396 | * verify_new_ex - verifies if a new exception is allowed by parent cgroup's permissions |
79d71974 AR |
397 | * @dev_cgroup: dev cgroup to be tested against |
398 | * @refex: new exception | |
399 | * @behavior: behavior of the exception's dev_cgroup | |
f5f3cf6f AR |
400 | * |
401 | * This is used to make sure a child cgroup won't have more privileges | |
402 | * than its parent | |
79d71974 AR |
403 | */ |
404 | static bool verify_new_ex(struct dev_cgroup *dev_cgroup, | |
405 | struct dev_exception_item *refex, | |
406 | enum devcg_behavior behavior) | |
407 | { | |
408 | bool match = false; | |
409 | ||
f78f5b90 | 410 | RCU_LOCKDEP_WARN(!rcu_read_lock_held() && |
dc3a04d5 | 411 | !lockdep_is_held(&devcgroup_mutex), |
f78f5b90 | 412 | "device_cgroup:verify_new_ex called without proper synchronization"); |
ad676077 | 413 | |
c39a2a30 AR |
414 | if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) { |
415 | if (behavior == DEVCG_DEFAULT_ALLOW) { | |
79d71974 AR |
416 | /* |
417 | * new exception in the child doesn't matter, only | |
418 | * adding extra restrictions | |
419 | */ | |
c39a2a30 AR |
420 | return true; |
421 | } else { | |
79d71974 AR |
422 | /* |
423 | * new exception in the child will add more devices | |
4432b507 | 424 | * that can be accessed, so it can't match any of |
79d71974 AR |
425 | * parent's exceptions, even slightly |
426 | */ | |
427 | match = match_exception_partial(&dev_cgroup->exceptions, | |
428 | refex->type, | |
429 | refex->major, | |
430 | refex->minor, | |
431 | refex->access); | |
432 | ||
c39a2a30 | 433 | if (match) |
c39a2a30 | 434 | return false; |
26898fdf | 435 | return true; |
c39a2a30 | 436 | } |
26898fdf | 437 | } else { |
79d71974 AR |
438 | /* |
439 | * Only behavior == DEVCG_DEFAULT_DENY allowed here, therefore | |
440 | * the new exception will add access to more devices and must | |
441 | * be contained completely in an parent's exception to be | |
442 | * allowed | |
443 | */ | |
444 | match = match_exception(&dev_cgroup->exceptions, refex->type, | |
445 | refex->major, refex->minor, | |
446 | refex->access); | |
447 | ||
c39a2a30 AR |
448 | if (match) |
449 | /* parent has an exception that matches the proposed */ | |
26898fdf | 450 | return true; |
c39a2a30 AR |
451 | else |
452 | return false; | |
26898fdf AR |
453 | } |
454 | return false; | |
08ce5f16 SH |
455 | } |
456 | ||
457 | /* | |
458 | * parent_has_perm: | |
db9aeca9 | 459 | * when adding a new allow rule to a device exception list, the rule |
08ce5f16 SH |
460 | * must be allowed in the parent device |
461 | */ | |
f92523e3 | 462 | static int parent_has_perm(struct dev_cgroup *childcg, |
db9aeca9 | 463 | struct dev_exception_item *ex) |
08ce5f16 | 464 | { |
5c9d535b | 465 | struct dev_cgroup *parent = css_to_devcgroup(childcg->css.parent); |
08ce5f16 | 466 | |
63876986 | 467 | if (!parent) |
08ce5f16 | 468 | return 1; |
79d71974 | 469 | return verify_new_ex(parent, ex, childcg->behavior); |
08ce5f16 SH |
470 | } |
471 | ||
d2c2b11c AR |
472 | /** |
473 | * parent_allows_removal - verify if it's ok to remove an exception | |
474 | * @childcg: child cgroup from where the exception will be removed | |
475 | * @ex: exception being removed | |
476 | * | |
477 | * When removing an exception in cgroups with default ALLOW policy, it must | |
478 | * be checked if removing it will give the child cgroup more access than the | |
479 | * parent. | |
480 | * | |
481 | * Return: true if it's ok to remove exception, false otherwise | |
482 | */ | |
483 | static bool parent_allows_removal(struct dev_cgroup *childcg, | |
484 | struct dev_exception_item *ex) | |
485 | { | |
5c9d535b | 486 | struct dev_cgroup *parent = css_to_devcgroup(childcg->css.parent); |
d2c2b11c AR |
487 | |
488 | if (!parent) | |
489 | return true; | |
490 | ||
491 | /* It's always allowed to remove access to devices */ | |
492 | if (childcg->behavior == DEVCG_DEFAULT_DENY) | |
493 | return true; | |
494 | ||
495 | /* | |
496 | * Make sure you're not removing part or a whole exception existing in | |
497 | * the parent cgroup | |
498 | */ | |
499 | return !match_exception_partial(&parent->exceptions, ex->type, | |
500 | ex->major, ex->minor, ex->access); | |
501 | } | |
502 | ||
4cef7299 AR |
503 | /** |
504 | * may_allow_all - checks if it's possible to change the behavior to | |
505 | * allow based on parent's rules. | |
506 | * @parent: device cgroup's parent | |
507 | * returns: != 0 in case it's allowed, 0 otherwise | |
508 | */ | |
509 | static inline int may_allow_all(struct dev_cgroup *parent) | |
510 | { | |
64e10477 AR |
511 | if (!parent) |
512 | return 1; | |
4cef7299 AR |
513 | return parent->behavior == DEVCG_DEFAULT_ALLOW; |
514 | } | |
515 | ||
bd2953eb AR |
516 | /** |
517 | * revalidate_active_exceptions - walks through the active exception list and | |
518 | * revalidates the exceptions based on parent's | |
519 | * behavior and exceptions. The exceptions that | |
520 | * are no longer valid will be removed. | |
521 | * Called with devcgroup_mutex held. | |
522 | * @devcg: cgroup which exceptions will be checked | |
523 | * | |
524 | * This is one of the three key functions for hierarchy implementation. | |
525 | * This function is responsible for re-evaluating all the cgroup's active | |
526 | * exceptions due to a parent's exception change. | |
da82c92f | 527 | * Refer to Documentation/admin-guide/cgroup-v1/devices.rst for more details. |
bd2953eb AR |
528 | */ |
529 | static void revalidate_active_exceptions(struct dev_cgroup *devcg) | |
530 | { | |
531 | struct dev_exception_item *ex; | |
532 | struct list_head *this, *tmp; | |
533 | ||
534 | list_for_each_safe(this, tmp, &devcg->exceptions) { | |
535 | ex = container_of(this, struct dev_exception_item, list); | |
536 | if (!parent_has_perm(devcg, ex)) | |
537 | dev_exception_rm(devcg, ex); | |
538 | } | |
539 | } | |
540 | ||
bd2953eb AR |
541 | /** |
542 | * propagate_exception - propagates a new exception to the children | |
543 | * @devcg_root: device cgroup that added a new exception | |
544 | * @ex: new exception to be propagated | |
545 | * | |
546 | * returns: 0 in case of success, != 0 in case of error | |
547 | */ | |
548 | static int propagate_exception(struct dev_cgroup *devcg_root, | |
549 | struct dev_exception_item *ex) | |
550 | { | |
492eb21b | 551 | struct cgroup_subsys_state *pos; |
bd2953eb | 552 | int rc = 0; |
bd2953eb | 553 | |
d591fb56 | 554 | rcu_read_lock(); |
bd2953eb | 555 | |
492eb21b TH |
556 | css_for_each_descendant_pre(pos, &devcg_root->css) { |
557 | struct dev_cgroup *devcg = css_to_devcgroup(pos); | |
d591fb56 TH |
558 | |
559 | /* | |
560 | * Because devcgroup_mutex is held, no devcg will become | |
561 | * online or offline during the tree walk (see on/offline | |
562 | * methods), and online ones are safe to access outside RCU | |
563 | * read lock without bumping refcnt. | |
564 | */ | |
bd8815a6 | 565 | if (pos == &devcg_root->css || !is_devcg_online(devcg)) |
d591fb56 TH |
566 | continue; |
567 | ||
568 | rcu_read_unlock(); | |
bd2953eb AR |
569 | |
570 | /* | |
571 | * in case both root's behavior and devcg is allow, a new | |
572 | * restriction means adding to the exception list | |
573 | */ | |
574 | if (devcg_root->behavior == DEVCG_DEFAULT_ALLOW && | |
575 | devcg->behavior == DEVCG_DEFAULT_ALLOW) { | |
576 | rc = dev_exception_add(devcg, ex); | |
577 | if (rc) | |
0fcc4c8c | 578 | return rc; |
bd2953eb AR |
579 | } else { |
580 | /* | |
581 | * in the other possible cases: | |
582 | * root's behavior: allow, devcg's: deny | |
583 | * root's behavior: deny, devcg's: deny | |
584 | * the exception will be removed | |
585 | */ | |
586 | dev_exception_rm(devcg, ex); | |
587 | } | |
588 | revalidate_active_exceptions(devcg); | |
589 | ||
d591fb56 | 590 | rcu_read_lock(); |
bd2953eb | 591 | } |
d591fb56 TH |
592 | |
593 | rcu_read_unlock(); | |
bd2953eb AR |
594 | return rc; |
595 | } | |
596 | ||
08ce5f16 | 597 | /* |
db9aeca9 | 598 | * Modify the exception list using allow/deny rules. |
08ce5f16 SH |
599 | * CAP_SYS_ADMIN is needed for this. It's at least separate from CAP_MKNOD |
600 | * so we can give a container CAP_MKNOD to let it create devices but not | |
db9aeca9 | 601 | * modify the exception list. |
08ce5f16 SH |
602 | * It seems likely we'll want to add a CAP_CONTAINER capability to allow |
603 | * us to also grant CAP_SYS_ADMIN to containers without giving away the | |
db9aeca9 | 604 | * device exception list controls, but for now we'll stick with CAP_SYS_ADMIN |
08ce5f16 SH |
605 | * |
606 | * Taking rules away is always allowed (given CAP_SYS_ADMIN). Granting | |
607 | * new access is only allowed if you're in the top-level cgroup, or your | |
608 | * parent cgroup has the access you're asking for. | |
609 | */ | |
f92523e3 | 610 | static int devcgroup_update_access(struct dev_cgroup *devcgroup, |
4d3bb511 | 611 | int filetype, char *buffer) |
08ce5f16 | 612 | { |
f92523e3 | 613 | const char *b; |
26fd8405 | 614 | char temp[12]; /* 11 + 1 characters needed for a u32 */ |
c39a2a30 | 615 | int count, rc = 0; |
db9aeca9 | 616 | struct dev_exception_item ex; |
5c9d535b | 617 | struct dev_cgroup *parent = css_to_devcgroup(devcgroup->css.parent); |
e68bfbd3 | 618 | struct dev_cgroup tmp_devcgrp; |
08ce5f16 SH |
619 | |
620 | if (!capable(CAP_SYS_ADMIN)) | |
621 | return -EPERM; | |
622 | ||
db9aeca9 | 623 | memset(&ex, 0, sizeof(ex)); |
e68bfbd3 | 624 | memset(&tmp_devcgrp, 0, sizeof(tmp_devcgrp)); |
08ce5f16 SH |
625 | b = buffer; |
626 | ||
627 | switch (*b) { | |
628 | case 'a': | |
ad676077 AR |
629 | switch (filetype) { |
630 | case DEVCG_ALLOW: | |
7a3bb24f | 631 | if (css_has_online_children(&devcgroup->css)) |
bd2953eb AR |
632 | return -EINVAL; |
633 | ||
4cef7299 | 634 | if (!may_allow_all(parent)) |
ad676077 | 635 | return -EPERM; |
e68bfbd3 WW |
636 | if (!parent) { |
637 | devcgroup->behavior = DEVCG_DEFAULT_ALLOW; | |
638 | dev_exception_clean(devcgroup); | |
64e10477 | 639 | break; |
e68bfbd3 | 640 | } |
64e10477 | 641 | |
e68bfbd3 WW |
642 | INIT_LIST_HEAD(&tmp_devcgrp.exceptions); |
643 | rc = dev_exceptions_copy(&tmp_devcgrp.exceptions, | |
644 | &devcgroup->exceptions); | |
645 | if (rc) | |
646 | return rc; | |
647 | dev_exception_clean(devcgroup); | |
4cef7299 AR |
648 | rc = dev_exceptions_copy(&devcgroup->exceptions, |
649 | &parent->exceptions); | |
e68bfbd3 WW |
650 | if (rc) { |
651 | dev_exceptions_move(&devcgroup->exceptions, | |
652 | &tmp_devcgrp.exceptions); | |
4cef7299 | 653 | return rc; |
e68bfbd3 WW |
654 | } |
655 | devcgroup->behavior = DEVCG_DEFAULT_ALLOW; | |
656 | dev_exception_clean(&tmp_devcgrp); | |
ad676077 AR |
657 | break; |
658 | case DEVCG_DENY: | |
7a3bb24f | 659 | if (css_has_online_children(&devcgroup->css)) |
bd2953eb AR |
660 | return -EINVAL; |
661 | ||
db9aeca9 | 662 | dev_exception_clean(devcgroup); |
5b7aa7d5 | 663 | devcgroup->behavior = DEVCG_DEFAULT_DENY; |
ad676077 AR |
664 | break; |
665 | default: | |
666 | return -EINVAL; | |
667 | } | |
668 | return 0; | |
08ce5f16 | 669 | case 'b': |
67e306fd | 670 | ex.type = DEVCG_DEV_BLOCK; |
08ce5f16 SH |
671 | break; |
672 | case 'c': | |
67e306fd | 673 | ex.type = DEVCG_DEV_CHAR; |
08ce5f16 SH |
674 | break; |
675 | default: | |
f92523e3 | 676 | return -EINVAL; |
08ce5f16 SH |
677 | } |
678 | b++; | |
f92523e3 PM |
679 | if (!isspace(*b)) |
680 | return -EINVAL; | |
08ce5f16 SH |
681 | b++; |
682 | if (*b == '*') { | |
db9aeca9 | 683 | ex.major = ~0; |
08ce5f16 SH |
684 | b++; |
685 | } else if (isdigit(*b)) { | |
26fd8405 AR |
686 | memset(temp, 0, sizeof(temp)); |
687 | for (count = 0; count < sizeof(temp) - 1; count++) { | |
688 | temp[count] = *b; | |
689 | b++; | |
690 | if (!isdigit(*b)) | |
691 | break; | |
692 | } | |
693 | rc = kstrtou32(temp, 10, &ex.major); | |
694 | if (rc) | |
695 | return -EINVAL; | |
08ce5f16 | 696 | } else { |
f92523e3 | 697 | return -EINVAL; |
08ce5f16 | 698 | } |
f92523e3 PM |
699 | if (*b != ':') |
700 | return -EINVAL; | |
08ce5f16 SH |
701 | b++; |
702 | ||
703 | /* read minor */ | |
704 | if (*b == '*') { | |
db9aeca9 | 705 | ex.minor = ~0; |
08ce5f16 SH |
706 | b++; |
707 | } else if (isdigit(*b)) { | |
26fd8405 AR |
708 | memset(temp, 0, sizeof(temp)); |
709 | for (count = 0; count < sizeof(temp) - 1; count++) { | |
710 | temp[count] = *b; | |
711 | b++; | |
712 | if (!isdigit(*b)) | |
713 | break; | |
714 | } | |
715 | rc = kstrtou32(temp, 10, &ex.minor); | |
716 | if (rc) | |
717 | return -EINVAL; | |
08ce5f16 | 718 | } else { |
f92523e3 | 719 | return -EINVAL; |
08ce5f16 | 720 | } |
f92523e3 PM |
721 | if (!isspace(*b)) |
722 | return -EINVAL; | |
08ce5f16 SH |
723 | for (b++, count = 0; count < 3; count++, b++) { |
724 | switch (*b) { | |
725 | case 'r': | |
67e306fd | 726 | ex.access |= DEVCG_ACC_READ; |
08ce5f16 SH |
727 | break; |
728 | case 'w': | |
67e306fd | 729 | ex.access |= DEVCG_ACC_WRITE; |
08ce5f16 SH |
730 | break; |
731 | case 'm': | |
67e306fd | 732 | ex.access |= DEVCG_ACC_MKNOD; |
08ce5f16 SH |
733 | break; |
734 | case '\n': | |
735 | case '\0': | |
736 | count = 3; | |
737 | break; | |
738 | default: | |
f92523e3 | 739 | return -EINVAL; |
08ce5f16 SH |
740 | } |
741 | } | |
742 | ||
08ce5f16 SH |
743 | switch (filetype) { |
744 | case DEVCG_ALLOW: | |
ad676077 AR |
745 | /* |
746 | * If the default policy is to allow by default, try to remove | |
747 | * an matching exception instead. And be silent about it: we | |
748 | * don't want to break compatibility | |
749 | */ | |
5b7aa7d5 | 750 | if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) { |
d2c2b11c AR |
751 | /* Check if the parent allows removing it first */ |
752 | if (!parent_allows_removal(devcgroup, &ex)) | |
753 | return -EPERM; | |
db9aeca9 | 754 | dev_exception_rm(devcgroup, &ex); |
d2c2b11c | 755 | break; |
ad676077 | 756 | } |
d2c2b11c AR |
757 | |
758 | if (!parent_has_perm(devcgroup, &ex)) | |
759 | return -EPERM; | |
bd2953eb AR |
760 | rc = dev_exception_add(devcgroup, &ex); |
761 | break; | |
08ce5f16 | 762 | case DEVCG_DENY: |
ad676077 AR |
763 | /* |
764 | * If the default policy is to deny by default, try to remove | |
765 | * an matching exception instead. And be silent about it: we | |
766 | * don't want to break compatibility | |
767 | */ | |
bd2953eb | 768 | if (devcgroup->behavior == DEVCG_DEFAULT_DENY) |
db9aeca9 | 769 | dev_exception_rm(devcgroup, &ex); |
bd2953eb AR |
770 | else |
771 | rc = dev_exception_add(devcgroup, &ex); | |
772 | ||
773 | if (rc) | |
774 | break; | |
775 | /* we only propagate new restrictions */ | |
776 | rc = propagate_exception(devcgroup, &ex); | |
777 | break; | |
08ce5f16 | 778 | default: |
bd2953eb | 779 | rc = -EINVAL; |
08ce5f16 | 780 | } |
bd2953eb | 781 | return rc; |
f92523e3 | 782 | } |
08ce5f16 | 783 | |
451af504 TH |
784 | static ssize_t devcgroup_access_write(struct kernfs_open_file *of, |
785 | char *buf, size_t nbytes, loff_t off) | |
f92523e3 PM |
786 | { |
787 | int retval; | |
b4046f00 LZ |
788 | |
789 | mutex_lock(&devcgroup_mutex); | |
451af504 TH |
790 | retval = devcgroup_update_access(css_to_devcgroup(of_css(of)), |
791 | of_cft(of)->private, strstrip(buf)); | |
b4046f00 | 792 | mutex_unlock(&devcgroup_mutex); |
451af504 | 793 | return retval ?: nbytes; |
08ce5f16 SH |
794 | } |
795 | ||
796 | static struct cftype dev_cgroup_files[] = { | |
797 | { | |
798 | .name = "allow", | |
451af504 | 799 | .write = devcgroup_access_write, |
08ce5f16 SH |
800 | .private = DEVCG_ALLOW, |
801 | }, | |
802 | { | |
803 | .name = "deny", | |
451af504 | 804 | .write = devcgroup_access_write, |
08ce5f16 SH |
805 | .private = DEVCG_DENY, |
806 | }, | |
29486df3 SH |
807 | { |
808 | .name = "list", | |
2da8ca82 | 809 | .seq_show = devcgroup_seq_show, |
29486df3 SH |
810 | .private = DEVCG_LIST, |
811 | }, | |
4baf6e33 | 812 | { } /* terminate */ |
08ce5f16 SH |
813 | }; |
814 | ||
073219e9 | 815 | struct cgroup_subsys devices_cgrp_subsys = { |
92fb9748 TH |
816 | .css_alloc = devcgroup_css_alloc, |
817 | .css_free = devcgroup_css_free, | |
1909554c AR |
818 | .css_online = devcgroup_online, |
819 | .css_offline = devcgroup_offline, | |
5577964e | 820 | .legacy_cftypes = dev_cgroup_files, |
08ce5f16 SH |
821 | }; |
822 | ||
ad676077 | 823 | /** |
eec8fd02 | 824 | * devcgroup_legacy_check_permission - checks if an inode operation is permitted |
ad676077 AR |
825 | * @type: device type |
826 | * @major: device major number | |
827 | * @minor: device minor number | |
67e306fd | 828 | * @access: combination of DEVCG_ACC_WRITE, DEVCG_ACC_READ and DEVCG_ACC_MKNOD |
ad676077 AR |
829 | * |
830 | * returns 0 on success, -EPERM case the operation is not permitted | |
831 | */ | |
eec8fd02 | 832 | static int devcgroup_legacy_check_permission(short type, u32 major, u32 minor, |
4b7d4d45 | 833 | short access) |
08ce5f16 | 834 | { |
8c9506d1 | 835 | struct dev_cgroup *dev_cgroup; |
79d71974 | 836 | bool rc; |
36fd71d2 | 837 | |
ad676077 | 838 | rcu_read_lock(); |
8c9506d1 | 839 | dev_cgroup = task_devcgroup(current); |
79d71974 AR |
840 | if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) |
841 | /* Can't match any of the exceptions, even partially */ | |
842 | rc = !match_exception_partial(&dev_cgroup->exceptions, | |
843 | type, major, minor, access); | |
844 | else | |
845 | /* Need to match completely one exception to be allowed */ | |
846 | rc = match_exception(&dev_cgroup->exceptions, type, major, | |
847 | minor, access); | |
ad676077 | 848 | rcu_read_unlock(); |
cd500819 | 849 | |
ad676077 AR |
850 | if (!rc) |
851 | return -EPERM; | |
36fd71d2 | 852 | |
ad676077 AR |
853 | return 0; |
854 | } | |
4b7d4d45 | 855 | |
eec8fd02 OU |
856 | #endif /* CONFIG_CGROUP_DEVICE */ |
857 | ||
858 | #if defined(CONFIG_CGROUP_DEVICE) || defined(CONFIG_CGROUP_BPF) | |
859 | ||
4b7d4d45 HK |
860 | int devcgroup_check_permission(short type, u32 major, u32 minor, short access) |
861 | { | |
862 | int rc = BPF_CGROUP_RUN_PROG_DEVICE_CGROUP(type, major, minor, access); | |
863 | ||
864 | if (rc) | |
f10d0596 | 865 | return rc; |
4b7d4d45 | 866 | |
eec8fd02 OU |
867 | #ifdef CONFIG_CGROUP_DEVICE |
868 | return devcgroup_legacy_check_permission(type, major, minor, access); | |
869 | ||
870 | #else /* CONFIG_CGROUP_DEVICE */ | |
871 | return 0; | |
872 | ||
873 | #endif /* CONFIG_CGROUP_DEVICE */ | |
4b7d4d45 HK |
874 | } |
875 | EXPORT_SYMBOL(devcgroup_check_permission); | |
eec8fd02 | 876 | #endif /* defined(CONFIG_CGROUP_DEVICE) || defined(CONFIG_CGROUP_BPF) */ |