blob: 7f88bcde7c61a42d355e81ead4719f86bab27630 [file] [log] [blame]
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -07001/*
Lai Jiangshan47c59802008-10-18 20:28:07 -07002 * device_cgroup.c - device cgroup subsystem
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -07003 *
4 * Copyright 2007 IBM Corp
5 */
6
7#include <linux/device_cgroup.h>
8#include <linux/cgroup.h>
9#include <linux/ctype.h>
10#include <linux/list.h>
11#include <linux/uaccess.h>
Serge E. Hallyn29486df2008-04-29 01:00:14 -070012#include <linux/seq_file.h>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090013#include <linux/slab.h>
Lai Jiangshan47c59802008-10-18 20:28:07 -070014#include <linux/rcupdate.h>
Li Zefanb4046f02009-04-02 16:57:32 -070015#include <linux/mutex.h>
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070016
17#define ACC_MKNOD 1
18#define ACC_READ 2
19#define ACC_WRITE 4
20#define ACC_MASK (ACC_MKNOD | ACC_READ | ACC_WRITE)
21
22#define DEV_BLOCK 1
23#define DEV_CHAR 2
24#define DEV_ALL 4 /* this represents all devices */
25
Li Zefanb4046f02009-04-02 16:57:32 -070026static DEFINE_MUTEX(devcgroup_mutex);
27
Aristeu Rozanskic39a2a32013-02-15 11:55:45 -050028enum devcg_behavior {
29 DEVCG_DEFAULT_NONE,
30 DEVCG_DEFAULT_ALLOW,
31 DEVCG_DEFAULT_DENY,
32};
33
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070034/*
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070035 * exception list locking rules:
Li Zefanb4046f02009-04-02 16:57:32 -070036 * hold devcgroup_mutex for update/read.
Lai Jiangshan47c59802008-10-18 20:28:07 -070037 * hold rcu_read_lock() for read.
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070038 */
39
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070040struct dev_exception_item {
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070041 u32 major, minor;
42 short type;
43 short access;
44 struct list_head list;
Pavel Emelyanov4efd1a12008-07-25 01:47:07 -070045 struct rcu_head rcu;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070046};
47
48struct dev_cgroup {
49 struct cgroup_subsys_state css;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070050 struct list_head exceptions;
Aristeu Rozanskic39a2a32013-02-15 11:55:45 -050051 enum devcg_behavior behavior;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070052};
53
Pavel Emelyanovb66862f2008-06-05 22:46:24 -070054static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s)
55{
Tejun Heoa7c6d552013-08-08 20:11:23 -040056 return s ? container_of(s, struct dev_cgroup, css) : NULL;
Pavel Emelyanovb66862f2008-06-05 22:46:24 -070057}
58
Paul Menagef92523e2008-07-25 01:47:03 -070059static inline struct dev_cgroup *task_devcgroup(struct task_struct *task)
60{
Tejun Heo073219e2014-02-08 10:36:58 -050061 return css_to_devcgroup(task_css(task, devices_cgrp_id));
Paul Menagef92523e2008-07-25 01:47:03 -070062}
63
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070064/*
Li Zefanb4046f02009-04-02 16:57:32 -070065 * called under devcgroup_mutex
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070066 */
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070067static int dev_exceptions_copy(struct list_head *dest, struct list_head *orig)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070068{
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070069 struct dev_exception_item *ex, *tmp, *new;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070070
Tejun Heo4b1c7842012-11-06 09:16:53 -080071 lockdep_assert_held(&devcgroup_mutex);
72
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070073 list_for_each_entry(ex, orig, list) {
74 new = kmemdup(ex, sizeof(*ex), GFP_KERNEL);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070075 if (!new)
76 goto free_and_exit;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070077 list_add_tail(&new->list, dest);
78 }
79
80 return 0;
81
82free_and_exit:
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070083 list_for_each_entry_safe(ex, tmp, dest, list) {
84 list_del(&ex->list);
85 kfree(ex);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070086 }
87 return -ENOMEM;
88}
89
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070090/*
Li Zefanb4046f02009-04-02 16:57:32 -070091 * called under devcgroup_mutex
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070092 */
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070093static int dev_exception_add(struct dev_cgroup *dev_cgroup,
94 struct dev_exception_item *ex)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070095{
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070096 struct dev_exception_item *excopy, *walk;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070097
Tejun Heo4b1c7842012-11-06 09:16:53 -080098 lockdep_assert_held(&devcgroup_mutex);
99
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700100 excopy = kmemdup(ex, sizeof(*ex), GFP_KERNEL);
101 if (!excopy)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700102 return -ENOMEM;
103
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700104 list_for_each_entry(walk, &dev_cgroup->exceptions, list) {
105 if (walk->type != ex->type)
Pavel Emelyanovd1ee2972008-06-05 22:46:28 -0700106 continue;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700107 if (walk->major != ex->major)
Pavel Emelyanovd1ee2972008-06-05 22:46:28 -0700108 continue;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700109 if (walk->minor != ex->minor)
Pavel Emelyanovd1ee2972008-06-05 22:46:28 -0700110 continue;
111
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700112 walk->access |= ex->access;
113 kfree(excopy);
114 excopy = NULL;
Pavel Emelyanovd1ee2972008-06-05 22:46:28 -0700115 }
116
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700117 if (excopy != NULL)
118 list_add_tail_rcu(&excopy->list, &dev_cgroup->exceptions);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700119 return 0;
120}
121
122/*
Li Zefanb4046f02009-04-02 16:57:32 -0700123 * called under devcgroup_mutex
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700124 */
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700125static void dev_exception_rm(struct dev_cgroup *dev_cgroup,
126 struct dev_exception_item *ex)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700127{
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700128 struct dev_exception_item *walk, *tmp;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700129
Tejun Heo4b1c7842012-11-06 09:16:53 -0800130 lockdep_assert_held(&devcgroup_mutex);
131
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700132 list_for_each_entry_safe(walk, tmp, &dev_cgroup->exceptions, list) {
133 if (walk->type != ex->type)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700134 continue;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700135 if (walk->major != ex->major)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700136 continue;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700137 if (walk->minor != ex->minor)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700138 continue;
139
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700140 walk->access &= ~ex->access;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700141 if (!walk->access) {
Pavel Emelyanov4efd1a12008-07-25 01:47:07 -0700142 list_del_rcu(&walk->list);
Lai Jiangshan6034f7e2011-03-15 18:07:57 +0800143 kfree_rcu(walk, rcu);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700144 }
145 }
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700146}
147
Jerry Snitselaar53eb8c82013-02-21 16:41:31 -0800148static void __dev_exception_clean(struct dev_cgroup *dev_cgroup)
149{
150 struct dev_exception_item *ex, *tmp;
151
152 list_for_each_entry_safe(ex, tmp, &dev_cgroup->exceptions, list) {
153 list_del_rcu(&ex->list);
154 kfree_rcu(ex, rcu);
155 }
156}
157
Aristeu Rozanski868539a2012-10-04 17:15:15 -0700158/**
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700159 * dev_exception_clean - frees all entries of the exception list
160 * @dev_cgroup: dev_cgroup with the exception list to be cleaned
Aristeu Rozanski868539a2012-10-04 17:15:15 -0700161 *
162 * called under devcgroup_mutex
163 */
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700164static void dev_exception_clean(struct dev_cgroup *dev_cgroup)
Aristeu Rozanski868539a2012-10-04 17:15:15 -0700165{
Tejun Heo4b1c7842012-11-06 09:16:53 -0800166 lockdep_assert_held(&devcgroup_mutex);
167
Jerry Snitselaar53eb8c82013-02-21 16:41:31 -0800168 __dev_exception_clean(dev_cgroup);
Aristeu Rozanski868539a2012-10-04 17:15:15 -0700169}
170
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500171static inline bool is_devcg_online(const struct dev_cgroup *devcg)
172{
173 return (devcg->behavior != DEVCG_DEFAULT_NONE);
174}
175
Aristeu Rozanski1909554c2013-02-15 11:55:46 -0500176/**
177 * devcgroup_online - initializes devcgroup's behavior and exceptions based on
178 * parent's
Tejun Heoeb954192013-08-08 20:11:23 -0400179 * @css: css getting online
Aristeu Rozanski1909554c2013-02-15 11:55:46 -0500180 * returns 0 in case of success, error code otherwise
181 */
Tejun Heoeb954192013-08-08 20:11:23 -0400182static int devcgroup_online(struct cgroup_subsys_state *css)
Aristeu Rozanski1909554c2013-02-15 11:55:46 -0500183{
Tejun Heoeb954192013-08-08 20:11:23 -0400184 struct dev_cgroup *dev_cgroup = css_to_devcgroup(css);
185 struct dev_cgroup *parent_dev_cgroup = css_to_devcgroup(css_parent(css));
Aristeu Rozanski1909554c2013-02-15 11:55:46 -0500186 int ret = 0;
187
188 mutex_lock(&devcgroup_mutex);
Aristeu Rozanski1909554c2013-02-15 11:55:46 -0500189
190 if (parent_dev_cgroup == NULL)
191 dev_cgroup->behavior = DEVCG_DEFAULT_ALLOW;
192 else {
193 ret = dev_exceptions_copy(&dev_cgroup->exceptions,
194 &parent_dev_cgroup->exceptions);
195 if (!ret)
196 dev_cgroup->behavior = parent_dev_cgroup->behavior;
197 }
198 mutex_unlock(&devcgroup_mutex);
199
200 return ret;
201}
202
Tejun Heoeb954192013-08-08 20:11:23 -0400203static void devcgroup_offline(struct cgroup_subsys_state *css)
Aristeu Rozanski1909554c2013-02-15 11:55:46 -0500204{
Tejun Heoeb954192013-08-08 20:11:23 -0400205 struct dev_cgroup *dev_cgroup = css_to_devcgroup(css);
Aristeu Rozanski1909554c2013-02-15 11:55:46 -0500206
207 mutex_lock(&devcgroup_mutex);
208 dev_cgroup->behavior = DEVCG_DEFAULT_NONE;
209 mutex_unlock(&devcgroup_mutex);
210}
211
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700212/*
213 * called from kernel/cgroup.c with cgroup_lock() held.
214 */
Tejun Heoeb954192013-08-08 20:11:23 -0400215static struct cgroup_subsys_state *
216devcgroup_css_alloc(struct cgroup_subsys_state *parent_css)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700217{
Aristeu Rozanski1909554c2013-02-15 11:55:46 -0500218 struct dev_cgroup *dev_cgroup;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700219
220 dev_cgroup = kzalloc(sizeof(*dev_cgroup), GFP_KERNEL);
221 if (!dev_cgroup)
222 return ERR_PTR(-ENOMEM);
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700223 INIT_LIST_HEAD(&dev_cgroup->exceptions);
Aristeu Rozanski1909554c2013-02-15 11:55:46 -0500224 dev_cgroup->behavior = DEVCG_DEFAULT_NONE;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700225
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700226 return &dev_cgroup->css;
227}
228
Tejun Heoeb954192013-08-08 20:11:23 -0400229static void devcgroup_css_free(struct cgroup_subsys_state *css)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700230{
Tejun Heoeb954192013-08-08 20:11:23 -0400231 struct dev_cgroup *dev_cgroup = css_to_devcgroup(css);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700232
Jerry Snitselaar53eb8c82013-02-21 16:41:31 -0800233 __dev_exception_clean(dev_cgroup);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700234 kfree(dev_cgroup);
235}
236
237#define DEVCG_ALLOW 1
238#define DEVCG_DENY 2
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700239#define DEVCG_LIST 3
240
Li Zefan17d213f2008-07-13 12:14:02 -0700241#define MAJMINLEN 13
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700242#define ACCLEN 4
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700243
244static void set_access(char *acc, short access)
245{
246 int idx = 0;
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700247 memset(acc, 0, ACCLEN);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700248 if (access & ACC_READ)
249 acc[idx++] = 'r';
250 if (access & ACC_WRITE)
251 acc[idx++] = 'w';
252 if (access & ACC_MKNOD)
253 acc[idx++] = 'm';
254}
255
256static char type_to_char(short type)
257{
258 if (type == DEV_ALL)
259 return 'a';
260 if (type == DEV_CHAR)
261 return 'c';
262 if (type == DEV_BLOCK)
263 return 'b';
264 return 'X';
265}
266
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700267static void set_majmin(char *str, unsigned m)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700268{
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700269 if (m == ~0)
Li Zefan7759fc92008-07-25 01:47:08 -0700270 strcpy(str, "*");
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700271 else
Li Zefan7759fc92008-07-25 01:47:08 -0700272 sprintf(str, "%u", m);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700273}
274
Tejun Heo2da8ca82013-12-05 12:28:04 -0500275static int devcgroup_seq_show(struct seq_file *m, void *v)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700276{
Tejun Heo2da8ca82013-12-05 12:28:04 -0500277 struct dev_cgroup *devcgroup = css_to_devcgroup(seq_css(m));
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700278 struct dev_exception_item *ex;
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700279 char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN];
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700280
Pavel Emelyanov4efd1a12008-07-25 01:47:07 -0700281 rcu_read_lock();
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700282 /*
283 * To preserve the compatibility:
284 * - Only show the "all devices" when the default policy is to allow
285 * - List the exceptions in case the default policy is to deny
286 * This way, the file remains as a "whitelist of devices"
287 */
Aristeu Rozanski5b7aa7d2012-10-25 13:37:38 -0700288 if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) {
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700289 set_access(acc, ACC_MASK);
290 set_majmin(maj, ~0);
291 set_majmin(min, ~0);
292 seq_printf(m, "%c %s:%s %s\n", type_to_char(DEV_ALL),
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700293 maj, min, acc);
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700294 } else {
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700295 list_for_each_entry_rcu(ex, &devcgroup->exceptions, list) {
296 set_access(acc, ex->access);
297 set_majmin(maj, ex->major);
298 set_majmin(min, ex->minor);
299 seq_printf(m, "%c %s:%s %s\n", type_to_char(ex->type),
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700300 maj, min, acc);
301 }
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700302 }
Pavel Emelyanov4efd1a12008-07-25 01:47:07 -0700303 rcu_read_unlock();
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700304
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700305 return 0;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700306}
307
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700308/**
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700309 * may_access - verifies if a new exception is part of what is allowed
310 * by a dev cgroup based on the default policy +
311 * exceptions. This is used to make sure a child cgroup
312 * won't have more privileges than its parent or to
313 * verify if a certain access is allowed.
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700314 * @dev_cgroup: dev cgroup to be tested against
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700315 * @refex: new exception
Aristeu Rozanskic39a2a32013-02-15 11:55:45 -0500316 * @behavior: behavior of the exception
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700317 */
Aristeu Rozanski26898fd2013-02-15 11:55:44 -0500318static bool may_access(struct dev_cgroup *dev_cgroup,
Aristeu Rozanskic39a2a32013-02-15 11:55:45 -0500319 struct dev_exception_item *refex,
320 enum devcg_behavior behavior)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700321{
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700322 struct dev_exception_item *ex;
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700323 bool match = false;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700324
Tejun Heo4b1c7842012-11-06 09:16:53 -0800325 rcu_lockdep_assert(rcu_read_lock_held() ||
326 lockdep_is_held(&devcgroup_mutex),
327 "device_cgroup::may_access() called without proper synchronization");
328
Tejun Heo201e72a2012-11-06 09:17:37 -0800329 list_for_each_entry_rcu(ex, &dev_cgroup->exceptions, list) {
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700330 if ((refex->type & DEV_BLOCK) && !(ex->type & DEV_BLOCK))
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700331 continue;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700332 if ((refex->type & DEV_CHAR) && !(ex->type & DEV_CHAR))
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700333 continue;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700334 if (ex->major != ~0 && ex->major != refex->major)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700335 continue;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700336 if (ex->minor != ~0 && ex->minor != refex->minor)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700337 continue;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700338 if (refex->access & (~ex->access))
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700339 continue;
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700340 match = true;
341 break;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700342 }
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700343
Aristeu Rozanskic39a2a32013-02-15 11:55:45 -0500344 if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) {
345 if (behavior == DEVCG_DEFAULT_ALLOW) {
346 /* the exception will deny access to certain devices */
Aristeu Rozanski26898fd2013-02-15 11:55:44 -0500347 return true;
Aristeu Rozanskic39a2a32013-02-15 11:55:45 -0500348 } else {
349 /* the exception will allow access to certain devices */
350 if (match)
351 /*
352 * a new exception allowing access shouldn't
353 * match an parent's exception
354 */
355 return false;
356 return true;
357 }
Aristeu Rozanski26898fd2013-02-15 11:55:44 -0500358 } else {
Aristeu Rozanskic39a2a32013-02-15 11:55:45 -0500359 /* only behavior == DEVCG_DEFAULT_DENY allowed here */
360 if (match)
361 /* parent has an exception that matches the proposed */
Aristeu Rozanski26898fd2013-02-15 11:55:44 -0500362 return true;
Aristeu Rozanskic39a2a32013-02-15 11:55:45 -0500363 else
364 return false;
Aristeu Rozanski26898fd2013-02-15 11:55:44 -0500365 }
366 return false;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700367}
368
369/*
370 * parent_has_perm:
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700371 * when adding a new allow rule to a device exception list, the rule
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700372 * must be allowed in the parent device
373 */
Paul Menagef92523e2008-07-25 01:47:03 -0700374static int parent_has_perm(struct dev_cgroup *childcg,
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700375 struct dev_exception_item *ex)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700376{
Tejun Heo63876982013-08-08 20:11:23 -0400377 struct dev_cgroup *parent = css_to_devcgroup(css_parent(&childcg->css));
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700378
Tejun Heo63876982013-08-08 20:11:23 -0400379 if (!parent)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700380 return 1;
Aristeu Rozanskic39a2a32013-02-15 11:55:45 -0500381 return may_access(parent, ex, childcg->behavior);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700382}
383
Aristeu Rozanski4cef7292012-10-25 13:37:45 -0700384/**
385 * may_allow_all - checks if it's possible to change the behavior to
386 * allow based on parent's rules.
387 * @parent: device cgroup's parent
388 * returns: != 0 in case it's allowed, 0 otherwise
389 */
390static inline int may_allow_all(struct dev_cgroup *parent)
391{
Aristeu Rozanski64e10472012-11-06 07:25:04 -0800392 if (!parent)
393 return 1;
Aristeu Rozanski4cef7292012-10-25 13:37:45 -0700394 return parent->behavior == DEVCG_DEFAULT_ALLOW;
395}
396
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500397/**
398 * revalidate_active_exceptions - walks through the active exception list and
399 * revalidates the exceptions based on parent's
400 * behavior and exceptions. The exceptions that
401 * are no longer valid will be removed.
402 * Called with devcgroup_mutex held.
403 * @devcg: cgroup which exceptions will be checked
404 *
405 * This is one of the three key functions for hierarchy implementation.
406 * This function is responsible for re-evaluating all the cgroup's active
407 * exceptions due to a parent's exception change.
408 * Refer to Documentation/cgroups/devices.txt for more details.
409 */
410static void revalidate_active_exceptions(struct dev_cgroup *devcg)
411{
412 struct dev_exception_item *ex;
413 struct list_head *this, *tmp;
414
415 list_for_each_safe(this, tmp, &devcg->exceptions) {
416 ex = container_of(this, struct dev_exception_item, list);
417 if (!parent_has_perm(devcg, ex))
418 dev_exception_rm(devcg, ex);
419 }
420}
421
422/**
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500423 * propagate_exception - propagates a new exception to the children
424 * @devcg_root: device cgroup that added a new exception
425 * @ex: new exception to be propagated
426 *
427 * returns: 0 in case of success, != 0 in case of error
428 */
429static int propagate_exception(struct dev_cgroup *devcg_root,
430 struct dev_exception_item *ex)
431{
Tejun Heo492eb212013-08-08 20:11:25 -0400432 struct cgroup_subsys_state *pos;
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500433 int rc = 0;
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500434
Tejun Heod591fb52013-05-24 10:55:38 +0900435 rcu_read_lock();
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500436
Tejun Heo492eb212013-08-08 20:11:25 -0400437 css_for_each_descendant_pre(pos, &devcg_root->css) {
438 struct dev_cgroup *devcg = css_to_devcgroup(pos);
Tejun Heod591fb52013-05-24 10:55:38 +0900439
440 /*
441 * Because devcgroup_mutex is held, no devcg will become
442 * online or offline during the tree walk (see on/offline
443 * methods), and online ones are safe to access outside RCU
444 * read lock without bumping refcnt.
445 */
Tejun Heobd8815a2013-08-08 20:11:27 -0400446 if (pos == &devcg_root->css || !is_devcg_online(devcg))
Tejun Heod591fb52013-05-24 10:55:38 +0900447 continue;
448
449 rcu_read_unlock();
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500450
451 /*
452 * in case both root's behavior and devcg is allow, a new
453 * restriction means adding to the exception list
454 */
455 if (devcg_root->behavior == DEVCG_DEFAULT_ALLOW &&
456 devcg->behavior == DEVCG_DEFAULT_ALLOW) {
457 rc = dev_exception_add(devcg, ex);
458 if (rc)
459 break;
460 } else {
461 /*
462 * in the other possible cases:
463 * root's behavior: allow, devcg's: deny
464 * root's behavior: deny, devcg's: deny
465 * the exception will be removed
466 */
467 dev_exception_rm(devcg, ex);
468 }
469 revalidate_active_exceptions(devcg);
470
Tejun Heod591fb52013-05-24 10:55:38 +0900471 rcu_read_lock();
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500472 }
Tejun Heod591fb52013-05-24 10:55:38 +0900473
474 rcu_read_unlock();
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500475 return rc;
476}
477
478static inline bool has_children(struct dev_cgroup *devcgroup)
479{
480 struct cgroup *cgrp = devcgroup->css.cgroup;
481
482 return !list_empty(&cgrp->children);
483}
484
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700485/*
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700486 * Modify the exception list using allow/deny rules.
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700487 * CAP_SYS_ADMIN is needed for this. It's at least separate from CAP_MKNOD
488 * so we can give a container CAP_MKNOD to let it create devices but not
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700489 * modify the exception list.
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700490 * It seems likely we'll want to add a CAP_CONTAINER capability to allow
491 * us to also grant CAP_SYS_ADMIN to containers without giving away the
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700492 * device exception list controls, but for now we'll stick with CAP_SYS_ADMIN
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700493 *
494 * Taking rules away is always allowed (given CAP_SYS_ADMIN). Granting
495 * new access is only allowed if you're in the top-level cgroup, or your
496 * parent cgroup has the access you're asking for.
497 */
Paul Menagef92523e2008-07-25 01:47:03 -0700498static int devcgroup_update_access(struct dev_cgroup *devcgroup,
499 int filetype, const char *buffer)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700500{
Paul Menagef92523e2008-07-25 01:47:03 -0700501 const char *b;
Aristeu Rozanski26fd8402012-10-25 13:37:41 -0700502 char temp[12]; /* 11 + 1 characters needed for a u32 */
Aristeu Rozanskic39a2a32013-02-15 11:55:45 -0500503 int count, rc = 0;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700504 struct dev_exception_item ex;
Tejun Heo63876982013-08-08 20:11:23 -0400505 struct dev_cgroup *parent = css_to_devcgroup(css_parent(&devcgroup->css));
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700506
507 if (!capable(CAP_SYS_ADMIN))
508 return -EPERM;
509
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700510 memset(&ex, 0, sizeof(ex));
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700511 b = buffer;
512
513 switch (*b) {
514 case 'a':
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700515 switch (filetype) {
516 case DEVCG_ALLOW:
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500517 if (has_children(devcgroup))
518 return -EINVAL;
519
Aristeu Rozanski4cef7292012-10-25 13:37:45 -0700520 if (!may_allow_all(parent))
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700521 return -EPERM;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700522 dev_exception_clean(devcgroup);
Aristeu Rozanski64e10472012-11-06 07:25:04 -0800523 devcgroup->behavior = DEVCG_DEFAULT_ALLOW;
524 if (!parent)
525 break;
526
Aristeu Rozanski4cef7292012-10-25 13:37:45 -0700527 rc = dev_exceptions_copy(&devcgroup->exceptions,
528 &parent->exceptions);
529 if (rc)
530 return rc;
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700531 break;
532 case DEVCG_DENY:
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500533 if (has_children(devcgroup))
534 return -EINVAL;
535
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700536 dev_exception_clean(devcgroup);
Aristeu Rozanski5b7aa7d2012-10-25 13:37:38 -0700537 devcgroup->behavior = DEVCG_DEFAULT_DENY;
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700538 break;
539 default:
540 return -EINVAL;
541 }
542 return 0;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700543 case 'b':
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700544 ex.type = DEV_BLOCK;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700545 break;
546 case 'c':
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700547 ex.type = DEV_CHAR;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700548 break;
549 default:
Paul Menagef92523e2008-07-25 01:47:03 -0700550 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700551 }
552 b++;
Paul Menagef92523e2008-07-25 01:47:03 -0700553 if (!isspace(*b))
554 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700555 b++;
556 if (*b == '*') {
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700557 ex.major = ~0;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700558 b++;
559 } else if (isdigit(*b)) {
Aristeu Rozanski26fd8402012-10-25 13:37:41 -0700560 memset(temp, 0, sizeof(temp));
561 for (count = 0; count < sizeof(temp) - 1; count++) {
562 temp[count] = *b;
563 b++;
564 if (!isdigit(*b))
565 break;
566 }
567 rc = kstrtou32(temp, 10, &ex.major);
568 if (rc)
569 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700570 } else {
Paul Menagef92523e2008-07-25 01:47:03 -0700571 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700572 }
Paul Menagef92523e2008-07-25 01:47:03 -0700573 if (*b != ':')
574 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700575 b++;
576
577 /* read minor */
578 if (*b == '*') {
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700579 ex.minor = ~0;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700580 b++;
581 } else if (isdigit(*b)) {
Aristeu Rozanski26fd8402012-10-25 13:37:41 -0700582 memset(temp, 0, sizeof(temp));
583 for (count = 0; count < sizeof(temp) - 1; count++) {
584 temp[count] = *b;
585 b++;
586 if (!isdigit(*b))
587 break;
588 }
589 rc = kstrtou32(temp, 10, &ex.minor);
590 if (rc)
591 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700592 } else {
Paul Menagef92523e2008-07-25 01:47:03 -0700593 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700594 }
Paul Menagef92523e2008-07-25 01:47:03 -0700595 if (!isspace(*b))
596 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700597 for (b++, count = 0; count < 3; count++, b++) {
598 switch (*b) {
599 case 'r':
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700600 ex.access |= ACC_READ;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700601 break;
602 case 'w':
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700603 ex.access |= ACC_WRITE;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700604 break;
605 case 'm':
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700606 ex.access |= ACC_MKNOD;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700607 break;
608 case '\n':
609 case '\0':
610 count = 3;
611 break;
612 default:
Paul Menagef92523e2008-07-25 01:47:03 -0700613 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700614 }
615 }
616
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700617 switch (filetype) {
618 case DEVCG_ALLOW:
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700619 if (!parent_has_perm(devcgroup, &ex))
Paul Menagef92523e2008-07-25 01:47:03 -0700620 return -EPERM;
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700621 /*
622 * If the default policy is to allow by default, try to remove
623 * an matching exception instead. And be silent about it: we
624 * don't want to break compatibility
625 */
Aristeu Rozanski5b7aa7d2012-10-25 13:37:38 -0700626 if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) {
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700627 dev_exception_rm(devcgroup, &ex);
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700628 return 0;
629 }
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500630 rc = dev_exception_add(devcgroup, &ex);
631 break;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700632 case DEVCG_DENY:
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700633 /*
634 * If the default policy is to deny by default, try to remove
635 * an matching exception instead. And be silent about it: we
636 * don't want to break compatibility
637 */
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500638 if (devcgroup->behavior == DEVCG_DEFAULT_DENY)
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700639 dev_exception_rm(devcgroup, &ex);
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500640 else
641 rc = dev_exception_add(devcgroup, &ex);
642
643 if (rc)
644 break;
645 /* we only propagate new restrictions */
646 rc = propagate_exception(devcgroup, &ex);
647 break;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700648 default:
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500649 rc = -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700650 }
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500651 return rc;
Paul Menagef92523e2008-07-25 01:47:03 -0700652}
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700653
Tejun Heo182446d2013-08-08 20:11:24 -0400654static int devcgroup_access_write(struct cgroup_subsys_state *css,
655 struct cftype *cft, const char *buffer)
Paul Menagef92523e2008-07-25 01:47:03 -0700656{
657 int retval;
Li Zefanb4046f02009-04-02 16:57:32 -0700658
659 mutex_lock(&devcgroup_mutex);
Tejun Heo182446d2013-08-08 20:11:24 -0400660 retval = devcgroup_update_access(css_to_devcgroup(css),
Paul Menagef92523e2008-07-25 01:47:03 -0700661 cft->private, buffer);
Li Zefanb4046f02009-04-02 16:57:32 -0700662 mutex_unlock(&devcgroup_mutex);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700663 return retval;
664}
665
666static struct cftype dev_cgroup_files[] = {
667 {
668 .name = "allow",
Paul Menagef92523e2008-07-25 01:47:03 -0700669 .write_string = devcgroup_access_write,
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700670 .private = DEVCG_ALLOW,
671 },
672 {
673 .name = "deny",
Paul Menagef92523e2008-07-25 01:47:03 -0700674 .write_string = devcgroup_access_write,
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700675 .private = DEVCG_DENY,
676 },
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700677 {
678 .name = "list",
Tejun Heo2da8ca82013-12-05 12:28:04 -0500679 .seq_show = devcgroup_seq_show,
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700680 .private = DEVCG_LIST,
681 },
Tejun Heo4baf6e32012-04-01 12:09:55 -0700682 { } /* terminate */
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700683};
684
Tejun Heo073219e2014-02-08 10:36:58 -0500685struct cgroup_subsys devices_cgrp_subsys = {
Tejun Heo92fb9742012-11-19 08:13:38 -0800686 .css_alloc = devcgroup_css_alloc,
687 .css_free = devcgroup_css_free,
Aristeu Rozanski1909554c2013-02-15 11:55:46 -0500688 .css_online = devcgroup_online,
689 .css_offline = devcgroup_offline,
Tejun Heo4baf6e32012-04-01 12:09:55 -0700690 .base_cftypes = dev_cgroup_files,
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700691};
692
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700693/**
694 * __devcgroup_check_permission - checks if an inode operation is permitted
695 * @dev_cgroup: the dev cgroup to be tested against
696 * @type: device type
697 * @major: device major number
698 * @minor: device minor number
699 * @access: combination of ACC_WRITE, ACC_READ and ACC_MKNOD
700 *
701 * returns 0 on success, -EPERM case the operation is not permitted
702 */
Jiri Slaby8c9506d2012-10-25 13:37:34 -0700703static int __devcgroup_check_permission(short type, u32 major, u32 minor,
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700704 short access)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700705{
Jiri Slaby8c9506d2012-10-25 13:37:34 -0700706 struct dev_cgroup *dev_cgroup;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700707 struct dev_exception_item ex;
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700708 int rc;
709
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700710 memset(&ex, 0, sizeof(ex));
711 ex.type = type;
712 ex.major = major;
713 ex.minor = minor;
714 ex.access = access;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700715
Pavel Emelyanov4efd1a12008-07-25 01:47:07 -0700716 rcu_read_lock();
Jiri Slaby8c9506d2012-10-25 13:37:34 -0700717 dev_cgroup = task_devcgroup(current);
Aristeu Rozanskic39a2a32013-02-15 11:55:45 -0500718 rc = may_access(dev_cgroup, &ex, dev_cgroup->behavior);
Pavel Emelyanov4efd1a12008-07-25 01:47:07 -0700719 rcu_read_unlock();
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700720
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700721 if (!rc)
722 return -EPERM;
723
724 return 0;
725}
726
727int __devcgroup_inode_permission(struct inode *inode, int mask)
728{
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700729 short type, access = 0;
730
731 if (S_ISBLK(inode->i_mode))
732 type = DEV_BLOCK;
733 if (S_ISCHR(inode->i_mode))
734 type = DEV_CHAR;
735 if (mask & MAY_WRITE)
736 access |= ACC_WRITE;
737 if (mask & MAY_READ)
738 access |= ACC_READ;
739
Jiri Slaby8c9506d2012-10-25 13:37:34 -0700740 return __devcgroup_check_permission(type, imajor(inode), iminor(inode),
741 access);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700742}
743
744int devcgroup_inode_mknod(int mode, dev_t dev)
745{
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700746 short type;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700747
Serge E. Hallyn0b82ac32009-01-07 18:07:46 -0800748 if (!S_ISBLK(mode) && !S_ISCHR(mode))
749 return 0;
750
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700751 if (S_ISBLK(mode))
752 type = DEV_BLOCK;
753 else
754 type = DEV_CHAR;
Li Zefan36fd71d2008-09-02 14:35:52 -0700755
Jiri Slaby8c9506d2012-10-25 13:37:34 -0700756 return __devcgroup_check_permission(type, MAJOR(dev), MINOR(dev),
757 ACC_MKNOD);
Li Zefan36fd71d2008-09-02 14:35:52 -0700758
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700759}