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