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Greg Kroah-Hartmanb2441312017-11-01 15:07:57 +01001// SPDX-License-Identifier: GPL-2.0
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -07002/*
Lai Jiangshan47c59802008-10-18 20:28:07 -07003 * device_cgroup.c - device cgroup subsystem
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -07004 *
5 * Copyright 2007 IBM Corp
6 */
7
8#include <linux/device_cgroup.h>
9#include <linux/cgroup.h>
10#include <linux/ctype.h>
11#include <linux/list.h>
12#include <linux/uaccess.h>
Serge E. Hallyn29486df2008-04-29 01:00:14 -070013#include <linux/seq_file.h>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090014#include <linux/slab.h>
Lai Jiangshan47c59802008-10-18 20:28:07 -070015#include <linux/rcupdate.h>
Li Zefanb4046f02009-04-02 16:57:32 -070016#include <linux/mutex.h>
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070017
Li Zefanb4046f02009-04-02 16:57:32 -070018static DEFINE_MUTEX(devcgroup_mutex);
19
Aristeu Rozanskic39a2a32013-02-15 11:55:45 -050020enum devcg_behavior {
21 DEVCG_DEFAULT_NONE,
22 DEVCG_DEFAULT_ALLOW,
23 DEVCG_DEFAULT_DENY,
24};
25
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070026/*
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070027 * exception list locking rules:
Li Zefanb4046f02009-04-02 16:57:32 -070028 * hold devcgroup_mutex for update/read.
Lai Jiangshan47c59802008-10-18 20:28:07 -070029 * hold rcu_read_lock() for read.
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070030 */
31
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070032struct dev_exception_item {
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070033 u32 major, minor;
34 short type;
35 short access;
36 struct list_head list;
Pavel Emelyanov4efd1a12008-07-25 01:47:07 -070037 struct rcu_head rcu;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070038};
39
40struct dev_cgroup {
41 struct cgroup_subsys_state css;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070042 struct list_head exceptions;
Aristeu Rozanskic39a2a32013-02-15 11:55:45 -050043 enum devcg_behavior behavior;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070044};
45
Pavel Emelyanovb66862f2008-06-05 22:46:24 -070046static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s)
47{
Tejun Heoa7c6d552013-08-08 20:11:23 -040048 return s ? container_of(s, struct dev_cgroup, css) : NULL;
Pavel Emelyanovb66862f2008-06-05 22:46:24 -070049}
50
Paul Menagef92523e2008-07-25 01:47:03 -070051static inline struct dev_cgroup *task_devcgroup(struct task_struct *task)
52{
Tejun Heo073219e2014-02-08 10:36:58 -050053 return css_to_devcgroup(task_css(task, devices_cgrp_id));
Paul Menagef92523e2008-07-25 01:47:03 -070054}
55
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070056/*
Li Zefanb4046f02009-04-02 16:57:32 -070057 * called under devcgroup_mutex
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070058 */
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070059static int dev_exceptions_copy(struct list_head *dest, struct list_head *orig)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070060{
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070061 struct dev_exception_item *ex, *tmp, *new;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070062
Tejun Heo4b1c7842012-11-06 09:16:53 -080063 lockdep_assert_held(&devcgroup_mutex);
64
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070065 list_for_each_entry(ex, orig, list) {
66 new = kmemdup(ex, sizeof(*ex), GFP_KERNEL);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070067 if (!new)
68 goto free_and_exit;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070069 list_add_tail(&new->list, dest);
70 }
71
72 return 0;
73
74free_and_exit:
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070075 list_for_each_entry_safe(ex, tmp, dest, list) {
76 list_del(&ex->list);
77 kfree(ex);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070078 }
79 return -ENOMEM;
80}
81
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070082/*
Li Zefanb4046f02009-04-02 16:57:32 -070083 * called under devcgroup_mutex
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070084 */
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070085static int dev_exception_add(struct dev_cgroup *dev_cgroup,
86 struct dev_exception_item *ex)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070087{
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070088 struct dev_exception_item *excopy, *walk;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070089
Tejun Heo4b1c7842012-11-06 09:16:53 -080090 lockdep_assert_held(&devcgroup_mutex);
91
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070092 excopy = kmemdup(ex, sizeof(*ex), GFP_KERNEL);
93 if (!excopy)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070094 return -ENOMEM;
95
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070096 list_for_each_entry(walk, &dev_cgroup->exceptions, list) {
97 if (walk->type != ex->type)
Pavel Emelyanovd1ee2972008-06-05 22:46:28 -070098 continue;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070099 if (walk->major != ex->major)
Pavel Emelyanovd1ee2972008-06-05 22:46:28 -0700100 continue;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700101 if (walk->minor != ex->minor)
Pavel Emelyanovd1ee2972008-06-05 22:46:28 -0700102 continue;
103
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700104 walk->access |= ex->access;
105 kfree(excopy);
106 excopy = NULL;
Pavel Emelyanovd1ee2972008-06-05 22:46:28 -0700107 }
108
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700109 if (excopy != NULL)
110 list_add_tail_rcu(&excopy->list, &dev_cgroup->exceptions);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700111 return 0;
112}
113
114/*
Li Zefanb4046f02009-04-02 16:57:32 -0700115 * called under devcgroup_mutex
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700116 */
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700117static void dev_exception_rm(struct dev_cgroup *dev_cgroup,
118 struct dev_exception_item *ex)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700119{
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700120 struct dev_exception_item *walk, *tmp;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700121
Tejun Heo4b1c7842012-11-06 09:16:53 -0800122 lockdep_assert_held(&devcgroup_mutex);
123
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700124 list_for_each_entry_safe(walk, tmp, &dev_cgroup->exceptions, list) {
125 if (walk->type != ex->type)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700126 continue;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700127 if (walk->major != ex->major)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700128 continue;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700129 if (walk->minor != ex->minor)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700130 continue;
131
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700132 walk->access &= ~ex->access;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700133 if (!walk->access) {
Pavel Emelyanov4efd1a12008-07-25 01:47:07 -0700134 list_del_rcu(&walk->list);
Lai Jiangshan6034f7e2011-03-15 18:07:57 +0800135 kfree_rcu(walk, rcu);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700136 }
137 }
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700138}
139
Jerry Snitselaar53eb8c82013-02-21 16:41:31 -0800140static void __dev_exception_clean(struct dev_cgroup *dev_cgroup)
141{
142 struct dev_exception_item *ex, *tmp;
143
144 list_for_each_entry_safe(ex, tmp, &dev_cgroup->exceptions, list) {
145 list_del_rcu(&ex->list);
146 kfree_rcu(ex, rcu);
147 }
148}
149
Aristeu Rozanski868539a2012-10-04 17:15:15 -0700150/**
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700151 * dev_exception_clean - frees all entries of the exception list
152 * @dev_cgroup: dev_cgroup with the exception list to be cleaned
Aristeu Rozanski868539a2012-10-04 17:15:15 -0700153 *
154 * called under devcgroup_mutex
155 */
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700156static void dev_exception_clean(struct dev_cgroup *dev_cgroup)
Aristeu Rozanski868539a2012-10-04 17:15:15 -0700157{
Tejun Heo4b1c7842012-11-06 09:16:53 -0800158 lockdep_assert_held(&devcgroup_mutex);
159
Jerry Snitselaar53eb8c82013-02-21 16:41:31 -0800160 __dev_exception_clean(dev_cgroup);
Aristeu Rozanski868539a2012-10-04 17:15:15 -0700161}
162
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500163static inline bool is_devcg_online(const struct dev_cgroup *devcg)
164{
165 return (devcg->behavior != DEVCG_DEFAULT_NONE);
166}
167
Aristeu Rozanski1909554c2013-02-15 11:55:46 -0500168/**
169 * devcgroup_online - initializes devcgroup's behavior and exceptions based on
170 * parent's
Tejun Heoeb954192013-08-08 20:11:23 -0400171 * @css: css getting online
Aristeu Rozanski1909554c2013-02-15 11:55:46 -0500172 * returns 0 in case of success, error code otherwise
173 */
Tejun Heoeb954192013-08-08 20:11:23 -0400174static int devcgroup_online(struct cgroup_subsys_state *css)
Aristeu Rozanski1909554c2013-02-15 11:55:46 -0500175{
Tejun Heoeb954192013-08-08 20:11:23 -0400176 struct dev_cgroup *dev_cgroup = css_to_devcgroup(css);
Tejun Heo5c9d5352014-05-16 13:22:48 -0400177 struct dev_cgroup *parent_dev_cgroup = css_to_devcgroup(css->parent);
Aristeu Rozanski1909554c2013-02-15 11:55:46 -0500178 int ret = 0;
179
180 mutex_lock(&devcgroup_mutex);
Aristeu Rozanski1909554c2013-02-15 11:55:46 -0500181
182 if (parent_dev_cgroup == NULL)
183 dev_cgroup->behavior = DEVCG_DEFAULT_ALLOW;
184 else {
185 ret = dev_exceptions_copy(&dev_cgroup->exceptions,
186 &parent_dev_cgroup->exceptions);
187 if (!ret)
188 dev_cgroup->behavior = parent_dev_cgroup->behavior;
189 }
190 mutex_unlock(&devcgroup_mutex);
191
192 return ret;
193}
194
Tejun Heoeb954192013-08-08 20:11:23 -0400195static void devcgroup_offline(struct cgroup_subsys_state *css)
Aristeu Rozanski1909554c2013-02-15 11:55:46 -0500196{
Tejun Heoeb954192013-08-08 20:11:23 -0400197 struct dev_cgroup *dev_cgroup = css_to_devcgroup(css);
Aristeu Rozanski1909554c2013-02-15 11:55:46 -0500198
199 mutex_lock(&devcgroup_mutex);
200 dev_cgroup->behavior = DEVCG_DEFAULT_NONE;
201 mutex_unlock(&devcgroup_mutex);
202}
203
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700204/*
205 * called from kernel/cgroup.c with cgroup_lock() held.
206 */
Tejun Heoeb954192013-08-08 20:11:23 -0400207static struct cgroup_subsys_state *
208devcgroup_css_alloc(struct cgroup_subsys_state *parent_css)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700209{
Aristeu Rozanski1909554c2013-02-15 11:55:46 -0500210 struct dev_cgroup *dev_cgroup;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700211
212 dev_cgroup = kzalloc(sizeof(*dev_cgroup), GFP_KERNEL);
213 if (!dev_cgroup)
214 return ERR_PTR(-ENOMEM);
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700215 INIT_LIST_HEAD(&dev_cgroup->exceptions);
Aristeu Rozanski1909554c2013-02-15 11:55:46 -0500216 dev_cgroup->behavior = DEVCG_DEFAULT_NONE;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700217
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700218 return &dev_cgroup->css;
219}
220
Tejun Heoeb954192013-08-08 20:11:23 -0400221static void devcgroup_css_free(struct cgroup_subsys_state *css)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700222{
Tejun Heoeb954192013-08-08 20:11:23 -0400223 struct dev_cgroup *dev_cgroup = css_to_devcgroup(css);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700224
Jerry Snitselaar53eb8c82013-02-21 16:41:31 -0800225 __dev_exception_clean(dev_cgroup);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700226 kfree(dev_cgroup);
227}
228
229#define DEVCG_ALLOW 1
230#define DEVCG_DENY 2
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700231#define DEVCG_LIST 3
232
Li Zefan17d213f2008-07-13 12:14:02 -0700233#define MAJMINLEN 13
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700234#define ACCLEN 4
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700235
236static void set_access(char *acc, short access)
237{
238 int idx = 0;
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700239 memset(acc, 0, ACCLEN);
Roman Gushchin67e306f2017-11-05 08:15:30 -0500240 if (access & DEVCG_ACC_READ)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700241 acc[idx++] = 'r';
Roman Gushchin67e306f2017-11-05 08:15:30 -0500242 if (access & DEVCG_ACC_WRITE)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700243 acc[idx++] = 'w';
Roman Gushchin67e306f2017-11-05 08:15:30 -0500244 if (access & DEVCG_ACC_MKNOD)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700245 acc[idx++] = 'm';
246}
247
248static char type_to_char(short type)
249{
Roman Gushchin67e306f2017-11-05 08:15:30 -0500250 if (type == DEVCG_DEV_ALL)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700251 return 'a';
Roman Gushchin67e306f2017-11-05 08:15:30 -0500252 if (type == DEVCG_DEV_CHAR)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700253 return 'c';
Roman Gushchin67e306f2017-11-05 08:15:30 -0500254 if (type == DEVCG_DEV_BLOCK)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700255 return 'b';
256 return 'X';
257}
258
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700259static void set_majmin(char *str, unsigned m)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700260{
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700261 if (m == ~0)
Li Zefan7759fc92008-07-25 01:47:08 -0700262 strcpy(str, "*");
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700263 else
Li Zefan7759fc92008-07-25 01:47:08 -0700264 sprintf(str, "%u", m);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700265}
266
Tejun Heo2da8ca82013-12-05 12:28:04 -0500267static int devcgroup_seq_show(struct seq_file *m, void *v)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700268{
Tejun Heo2da8ca82013-12-05 12:28:04 -0500269 struct dev_cgroup *devcgroup = css_to_devcgroup(seq_css(m));
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700270 struct dev_exception_item *ex;
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700271 char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN];
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700272
Pavel Emelyanov4efd1a12008-07-25 01:47:07 -0700273 rcu_read_lock();
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700274 /*
275 * To preserve the compatibility:
276 * - Only show the "all devices" when the default policy is to allow
277 * - List the exceptions in case the default policy is to deny
278 * This way, the file remains as a "whitelist of devices"
279 */
Aristeu Rozanski5b7aa7d2012-10-25 13:37:38 -0700280 if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) {
Roman Gushchin67e306f2017-11-05 08:15:30 -0500281 set_access(acc, DEVCG_ACC_MASK);
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700282 set_majmin(maj, ~0);
283 set_majmin(min, ~0);
Roman Gushchin67e306f2017-11-05 08:15:30 -0500284 seq_printf(m, "%c %s:%s %s\n", type_to_char(DEVCG_DEV_ALL),
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700285 maj, min, acc);
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700286 } else {
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700287 list_for_each_entry_rcu(ex, &devcgroup->exceptions, list) {
288 set_access(acc, ex->access);
289 set_majmin(maj, ex->major);
290 set_majmin(min, ex->minor);
291 seq_printf(m, "%c %s:%s %s\n", type_to_char(ex->type),
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700292 maj, min, acc);
293 }
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700294 }
Pavel Emelyanov4efd1a12008-07-25 01:47:07 -0700295 rcu_read_unlock();
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700296
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700297 return 0;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700298}
299
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700300/**
Aristeu Rozanskif5f3cf6f2014-04-24 15:33:21 -0400301 * match_exception - iterates the exception list trying to find a complete match
Aristeu Rozanski79d71972014-04-21 12:13:03 -0400302 * @exceptions: list of exceptions
Roman Gushchin67e306f2017-11-05 08:15:30 -0500303 * @type: device type (DEVCG_DEV_BLOCK or DEVCG_DEV_CHAR)
Aristeu Rozanski79d71972014-04-21 12:13:03 -0400304 * @major: device file major number, ~0 to match all
305 * @minor: device file minor number, ~0 to match all
Roman Gushchin67e306f2017-11-05 08:15:30 -0500306 * @access: permission mask (DEVCG_ACC_READ, DEVCG_ACC_WRITE, DEVCG_ACC_MKNOD)
Aristeu Rozanski79d71972014-04-21 12:13:03 -0400307 *
Aristeu Rozanskif5f3cf6f2014-04-24 15:33:21 -0400308 * It is considered a complete match if an exception is found that will
309 * contain the entire range of provided parameters.
310 *
311 * Return: true in case it matches an exception completely
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700312 */
Aristeu Rozanski79d71972014-04-21 12:13:03 -0400313static bool match_exception(struct list_head *exceptions, short type,
314 u32 major, u32 minor, short access)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700315{
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700316 struct dev_exception_item *ex;
Aristeu Rozanski79d71972014-04-21 12:13:03 -0400317
318 list_for_each_entry_rcu(ex, exceptions, list) {
Roman Gushchin67e306f2017-11-05 08:15:30 -0500319 if ((type & DEVCG_DEV_BLOCK) && !(ex->type & DEVCG_DEV_BLOCK))
Aristeu Rozanski79d71972014-04-21 12:13:03 -0400320 continue;
Roman Gushchin67e306f2017-11-05 08:15:30 -0500321 if ((type & DEVCG_DEV_CHAR) && !(ex->type & DEVCG_DEV_CHAR))
Aristeu Rozanski79d71972014-04-21 12:13:03 -0400322 continue;
323 if (ex->major != ~0 && ex->major != major)
324 continue;
325 if (ex->minor != ~0 && ex->minor != minor)
326 continue;
327 /* provided access cannot have more than the exception rule */
328 if (access & (~ex->access))
329 continue;
330 return true;
331 }
332 return false;
333}
334
335/**
Aristeu Rozanskif5f3cf6f2014-04-24 15:33:21 -0400336 * match_exception_partial - iterates the exception list trying to find a partial match
Aristeu Rozanski79d71972014-04-21 12:13:03 -0400337 * @exceptions: list of exceptions
Roman Gushchin67e306f2017-11-05 08:15:30 -0500338 * @type: device type (DEVCG_DEV_BLOCK or DEVCG_DEV_CHAR)
Aristeu Rozanski79d71972014-04-21 12:13:03 -0400339 * @major: device file major number, ~0 to match all
340 * @minor: device file minor number, ~0 to match all
Roman Gushchin67e306f2017-11-05 08:15:30 -0500341 * @access: permission mask (DEVCG_ACC_READ, DEVCG_ACC_WRITE, DEVCG_ACC_MKNOD)
Aristeu Rozanski79d71972014-04-21 12:13:03 -0400342 *
Aristeu Rozanskif5f3cf6f2014-04-24 15:33:21 -0400343 * It is considered a partial match if an exception's range is found to
344 * contain *any* of the devices specified by provided parameters. This is
345 * used to make sure no extra access is being granted that is forbidden by
346 * any of the exception list.
347 *
348 * Return: true in case the provided range mat matches an exception completely
Aristeu Rozanski79d71972014-04-21 12:13:03 -0400349 */
350static bool match_exception_partial(struct list_head *exceptions, short type,
351 u32 major, u32 minor, short access)
352{
353 struct dev_exception_item *ex;
354
355 list_for_each_entry_rcu(ex, exceptions, list) {
Roman Gushchin67e306f2017-11-05 08:15:30 -0500356 if ((type & DEVCG_DEV_BLOCK) && !(ex->type & DEVCG_DEV_BLOCK))
Aristeu Rozanski79d71972014-04-21 12:13:03 -0400357 continue;
Roman Gushchin67e306f2017-11-05 08:15:30 -0500358 if ((type & DEVCG_DEV_CHAR) && !(ex->type & DEVCG_DEV_CHAR))
Aristeu Rozanski79d71972014-04-21 12:13:03 -0400359 continue;
360 /*
361 * We must be sure that both the exception and the provided
362 * range aren't masking all devices
363 */
364 if (ex->major != ~0 && major != ~0 && ex->major != major)
365 continue;
366 if (ex->minor != ~0 && minor != ~0 && ex->minor != minor)
367 continue;
368 /*
369 * In order to make sure the provided range isn't matching
370 * an exception, all its access bits shouldn't match the
371 * exception's access bits
372 */
373 if (!(access & ex->access))
374 continue;
375 return true;
376 }
377 return false;
378}
379
380/**
Aristeu Rozanskif5f3cf6f2014-04-24 15:33:21 -0400381 * verify_new_ex - verifies if a new exception is allowed by parent cgroup's permissions
Aristeu Rozanski79d71972014-04-21 12:13:03 -0400382 * @dev_cgroup: dev cgroup to be tested against
383 * @refex: new exception
384 * @behavior: behavior of the exception's dev_cgroup
Aristeu Rozanskif5f3cf6f2014-04-24 15:33:21 -0400385 *
386 * This is used to make sure a child cgroup won't have more privileges
387 * than its parent
Aristeu Rozanski79d71972014-04-21 12:13:03 -0400388 */
389static bool verify_new_ex(struct dev_cgroup *dev_cgroup,
390 struct dev_exception_item *refex,
391 enum devcg_behavior behavior)
392{
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700393 bool match = false;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700394
Paul E. McKenneyf78f5b92015-06-18 15:50:02 -0700395 RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&
Paul E. McKenneydc3a04d2015-09-02 17:11:22 -0700396 !lockdep_is_held(&devcgroup_mutex),
Paul E. McKenneyf78f5b92015-06-18 15:50:02 -0700397 "device_cgroup:verify_new_ex called without proper synchronization");
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700398
Aristeu Rozanskic39a2a32013-02-15 11:55:45 -0500399 if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) {
400 if (behavior == DEVCG_DEFAULT_ALLOW) {
Aristeu Rozanski79d71972014-04-21 12:13:03 -0400401 /*
402 * new exception in the child doesn't matter, only
403 * adding extra restrictions
404 */
Aristeu Rozanski26898fd2013-02-15 11:55:44 -0500405 return true;
Aristeu Rozanskic39a2a32013-02-15 11:55:45 -0500406 } else {
Aristeu Rozanski79d71972014-04-21 12:13:03 -0400407 /*
408 * new exception in the child will add more devices
409 * that can be acessed, so it can't match any of
410 * parent's exceptions, even slightly
411 */
412 match = match_exception_partial(&dev_cgroup->exceptions,
413 refex->type,
414 refex->major,
415 refex->minor,
416 refex->access);
417
Aristeu Rozanskic39a2a32013-02-15 11:55:45 -0500418 if (match)
Aristeu Rozanskic39a2a32013-02-15 11:55:45 -0500419 return false;
420 return true;
421 }
Aristeu Rozanski26898fd2013-02-15 11:55:44 -0500422 } else {
Aristeu Rozanski79d71972014-04-21 12:13:03 -0400423 /*
424 * Only behavior == DEVCG_DEFAULT_DENY allowed here, therefore
425 * the new exception will add access to more devices and must
426 * be contained completely in an parent's exception to be
427 * allowed
428 */
429 match = match_exception(&dev_cgroup->exceptions, refex->type,
430 refex->major, refex->minor,
431 refex->access);
432
Aristeu Rozanskic39a2a32013-02-15 11:55:45 -0500433 if (match)
434 /* parent has an exception that matches the proposed */
Aristeu Rozanski26898fd2013-02-15 11:55:44 -0500435 return true;
Aristeu Rozanskic39a2a32013-02-15 11:55:45 -0500436 else
437 return false;
Aristeu Rozanski26898fd2013-02-15 11:55:44 -0500438 }
439 return false;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700440}
441
442/*
443 * parent_has_perm:
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700444 * when adding a new allow rule to a device exception list, the rule
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700445 * must be allowed in the parent device
446 */
Paul Menagef92523e2008-07-25 01:47:03 -0700447static int parent_has_perm(struct dev_cgroup *childcg,
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700448 struct dev_exception_item *ex)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700449{
Tejun Heo5c9d5352014-05-16 13:22:48 -0400450 struct dev_cgroup *parent = css_to_devcgroup(childcg->css.parent);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700451
Tejun Heo63876982013-08-08 20:11:23 -0400452 if (!parent)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700453 return 1;
Aristeu Rozanski79d71972014-04-21 12:13:03 -0400454 return verify_new_ex(parent, ex, childcg->behavior);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700455}
456
Aristeu Rozanski4cef7292012-10-25 13:37:45 -0700457/**
Aristeu Rozanskid2c2b112014-05-05 11:18:59 -0400458 * parent_allows_removal - verify if it's ok to remove an exception
459 * @childcg: child cgroup from where the exception will be removed
460 * @ex: exception being removed
461 *
462 * When removing an exception in cgroups with default ALLOW policy, it must
463 * be checked if removing it will give the child cgroup more access than the
464 * parent.
465 *
466 * Return: true if it's ok to remove exception, false otherwise
467 */
468static bool parent_allows_removal(struct dev_cgroup *childcg,
469 struct dev_exception_item *ex)
470{
Tejun Heo5c9d5352014-05-16 13:22:48 -0400471 struct dev_cgroup *parent = css_to_devcgroup(childcg->css.parent);
Aristeu Rozanskid2c2b112014-05-05 11:18:59 -0400472
473 if (!parent)
474 return true;
475
476 /* It's always allowed to remove access to devices */
477 if (childcg->behavior == DEVCG_DEFAULT_DENY)
478 return true;
479
480 /*
481 * Make sure you're not removing part or a whole exception existing in
482 * the parent cgroup
483 */
484 return !match_exception_partial(&parent->exceptions, ex->type,
485 ex->major, ex->minor, ex->access);
486}
487
488/**
Aristeu Rozanski4cef7292012-10-25 13:37:45 -0700489 * may_allow_all - checks if it's possible to change the behavior to
490 * allow based on parent's rules.
491 * @parent: device cgroup's parent
492 * returns: != 0 in case it's allowed, 0 otherwise
493 */
494static inline int may_allow_all(struct dev_cgroup *parent)
495{
Aristeu Rozanski64e10472012-11-06 07:25:04 -0800496 if (!parent)
497 return 1;
Aristeu Rozanski4cef7292012-10-25 13:37:45 -0700498 return parent->behavior == DEVCG_DEFAULT_ALLOW;
499}
500
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500501/**
502 * revalidate_active_exceptions - walks through the active exception list and
503 * revalidates the exceptions based on parent's
504 * behavior and exceptions. The exceptions that
505 * are no longer valid will be removed.
506 * Called with devcgroup_mutex held.
507 * @devcg: cgroup which exceptions will be checked
508 *
509 * This is one of the three key functions for hierarchy implementation.
510 * This function is responsible for re-evaluating all the cgroup's active
511 * exceptions due to a parent's exception change.
512 * Refer to Documentation/cgroups/devices.txt for more details.
513 */
514static void revalidate_active_exceptions(struct dev_cgroup *devcg)
515{
516 struct dev_exception_item *ex;
517 struct list_head *this, *tmp;
518
519 list_for_each_safe(this, tmp, &devcg->exceptions) {
520 ex = container_of(this, struct dev_exception_item, list);
521 if (!parent_has_perm(devcg, ex))
522 dev_exception_rm(devcg, ex);
523 }
524}
525
526/**
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500527 * propagate_exception - propagates a new exception to the children
528 * @devcg_root: device cgroup that added a new exception
529 * @ex: new exception to be propagated
530 *
531 * returns: 0 in case of success, != 0 in case of error
532 */
533static int propagate_exception(struct dev_cgroup *devcg_root,
534 struct dev_exception_item *ex)
535{
Tejun Heo492eb212013-08-08 20:11:25 -0400536 struct cgroup_subsys_state *pos;
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500537 int rc = 0;
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500538
Tejun Heod591fb52013-05-24 10:55:38 +0900539 rcu_read_lock();
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500540
Tejun Heo492eb212013-08-08 20:11:25 -0400541 css_for_each_descendant_pre(pos, &devcg_root->css) {
542 struct dev_cgroup *devcg = css_to_devcgroup(pos);
Tejun Heod591fb52013-05-24 10:55:38 +0900543
544 /*
545 * Because devcgroup_mutex is held, no devcg will become
546 * online or offline during the tree walk (see on/offline
547 * methods), and online ones are safe to access outside RCU
548 * read lock without bumping refcnt.
549 */
Tejun Heobd8815a2013-08-08 20:11:27 -0400550 if (pos == &devcg_root->css || !is_devcg_online(devcg))
Tejun Heod591fb52013-05-24 10:55:38 +0900551 continue;
552
553 rcu_read_unlock();
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500554
555 /*
556 * in case both root's behavior and devcg is allow, a new
557 * restriction means adding to the exception list
558 */
559 if (devcg_root->behavior == DEVCG_DEFAULT_ALLOW &&
560 devcg->behavior == DEVCG_DEFAULT_ALLOW) {
561 rc = dev_exception_add(devcg, ex);
562 if (rc)
563 break;
564 } else {
565 /*
566 * in the other possible cases:
567 * root's behavior: allow, devcg's: deny
568 * root's behavior: deny, devcg's: deny
569 * the exception will be removed
570 */
571 dev_exception_rm(devcg, ex);
572 }
573 revalidate_active_exceptions(devcg);
574
Tejun Heod591fb52013-05-24 10:55:38 +0900575 rcu_read_lock();
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500576 }
Tejun Heod591fb52013-05-24 10:55:38 +0900577
578 rcu_read_unlock();
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500579 return rc;
580}
581
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700582/*
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700583 * Modify the exception list using allow/deny rules.
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700584 * CAP_SYS_ADMIN is needed for this. It's at least separate from CAP_MKNOD
585 * so we can give a container CAP_MKNOD to let it create devices but not
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700586 * modify the exception list.
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700587 * It seems likely we'll want to add a CAP_CONTAINER capability to allow
588 * us to also grant CAP_SYS_ADMIN to containers without giving away the
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700589 * device exception list controls, but for now we'll stick with CAP_SYS_ADMIN
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700590 *
591 * Taking rules away is always allowed (given CAP_SYS_ADMIN). Granting
592 * new access is only allowed if you're in the top-level cgroup, or your
593 * parent cgroup has the access you're asking for.
594 */
Paul Menagef92523e2008-07-25 01:47:03 -0700595static int devcgroup_update_access(struct dev_cgroup *devcgroup,
Tejun Heo4d3bb512014-03-19 10:23:54 -0400596 int filetype, char *buffer)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700597{
Paul Menagef92523e2008-07-25 01:47:03 -0700598 const char *b;
Aristeu Rozanski26fd8402012-10-25 13:37:41 -0700599 char temp[12]; /* 11 + 1 characters needed for a u32 */
Aristeu Rozanskic39a2a32013-02-15 11:55:45 -0500600 int count, rc = 0;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700601 struct dev_exception_item ex;
Tejun Heo5c9d5352014-05-16 13:22:48 -0400602 struct dev_cgroup *parent = css_to_devcgroup(devcgroup->css.parent);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700603
604 if (!capable(CAP_SYS_ADMIN))
605 return -EPERM;
606
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700607 memset(&ex, 0, sizeof(ex));
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700608 b = buffer;
609
610 switch (*b) {
611 case 'a':
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700612 switch (filetype) {
613 case DEVCG_ALLOW:
Tejun Heo7a3bb242014-05-16 13:22:52 -0400614 if (css_has_online_children(&devcgroup->css))
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500615 return -EINVAL;
616
Aristeu Rozanski4cef7292012-10-25 13:37:45 -0700617 if (!may_allow_all(parent))
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700618 return -EPERM;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700619 dev_exception_clean(devcgroup);
Aristeu Rozanski64e10472012-11-06 07:25:04 -0800620 devcgroup->behavior = DEVCG_DEFAULT_ALLOW;
621 if (!parent)
622 break;
623
Aristeu Rozanski4cef7292012-10-25 13:37:45 -0700624 rc = dev_exceptions_copy(&devcgroup->exceptions,
625 &parent->exceptions);
626 if (rc)
627 return rc;
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700628 break;
629 case DEVCG_DENY:
Tejun Heo7a3bb242014-05-16 13:22:52 -0400630 if (css_has_online_children(&devcgroup->css))
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500631 return -EINVAL;
632
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700633 dev_exception_clean(devcgroup);
Aristeu Rozanski5b7aa7d2012-10-25 13:37:38 -0700634 devcgroup->behavior = DEVCG_DEFAULT_DENY;
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700635 break;
636 default:
637 return -EINVAL;
638 }
639 return 0;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700640 case 'b':
Roman Gushchin67e306f2017-11-05 08:15:30 -0500641 ex.type = DEVCG_DEV_BLOCK;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700642 break;
643 case 'c':
Roman Gushchin67e306f2017-11-05 08:15:30 -0500644 ex.type = DEVCG_DEV_CHAR;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700645 break;
646 default:
Paul Menagef92523e2008-07-25 01:47:03 -0700647 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700648 }
649 b++;
Paul Menagef92523e2008-07-25 01:47:03 -0700650 if (!isspace(*b))
651 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700652 b++;
653 if (*b == '*') {
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700654 ex.major = ~0;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700655 b++;
656 } else if (isdigit(*b)) {
Aristeu Rozanski26fd8402012-10-25 13:37:41 -0700657 memset(temp, 0, sizeof(temp));
658 for (count = 0; count < sizeof(temp) - 1; count++) {
659 temp[count] = *b;
660 b++;
661 if (!isdigit(*b))
662 break;
663 }
664 rc = kstrtou32(temp, 10, &ex.major);
665 if (rc)
666 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700667 } else {
Paul Menagef92523e2008-07-25 01:47:03 -0700668 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700669 }
Paul Menagef92523e2008-07-25 01:47:03 -0700670 if (*b != ':')
671 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700672 b++;
673
674 /* read minor */
675 if (*b == '*') {
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700676 ex.minor = ~0;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700677 b++;
678 } else if (isdigit(*b)) {
Aristeu Rozanski26fd8402012-10-25 13:37:41 -0700679 memset(temp, 0, sizeof(temp));
680 for (count = 0; count < sizeof(temp) - 1; count++) {
681 temp[count] = *b;
682 b++;
683 if (!isdigit(*b))
684 break;
685 }
686 rc = kstrtou32(temp, 10, &ex.minor);
687 if (rc)
688 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700689 } else {
Paul Menagef92523e2008-07-25 01:47:03 -0700690 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700691 }
Paul Menagef92523e2008-07-25 01:47:03 -0700692 if (!isspace(*b))
693 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700694 for (b++, count = 0; count < 3; count++, b++) {
695 switch (*b) {
696 case 'r':
Roman Gushchin67e306f2017-11-05 08:15:30 -0500697 ex.access |= DEVCG_ACC_READ;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700698 break;
699 case 'w':
Roman Gushchin67e306f2017-11-05 08:15:30 -0500700 ex.access |= DEVCG_ACC_WRITE;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700701 break;
702 case 'm':
Roman Gushchin67e306f2017-11-05 08:15:30 -0500703 ex.access |= DEVCG_ACC_MKNOD;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700704 break;
705 case '\n':
706 case '\0':
707 count = 3;
708 break;
709 default:
Paul Menagef92523e2008-07-25 01:47:03 -0700710 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700711 }
712 }
713
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700714 switch (filetype) {
715 case DEVCG_ALLOW:
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700716 /*
717 * If the default policy is to allow by default, try to remove
718 * an matching exception instead. And be silent about it: we
719 * don't want to break compatibility
720 */
Aristeu Rozanski5b7aa7d2012-10-25 13:37:38 -0700721 if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) {
Aristeu Rozanskid2c2b112014-05-05 11:18:59 -0400722 /* Check if the parent allows removing it first */
723 if (!parent_allows_removal(devcgroup, &ex))
724 return -EPERM;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700725 dev_exception_rm(devcgroup, &ex);
Aristeu Rozanskid2c2b112014-05-05 11:18:59 -0400726 break;
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700727 }
Aristeu Rozanskid2c2b112014-05-05 11:18:59 -0400728
729 if (!parent_has_perm(devcgroup, &ex))
730 return -EPERM;
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500731 rc = dev_exception_add(devcgroup, &ex);
732 break;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700733 case DEVCG_DENY:
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700734 /*
735 * If the default policy is to deny by default, try to remove
736 * an matching exception instead. And be silent about it: we
737 * don't want to break compatibility
738 */
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500739 if (devcgroup->behavior == DEVCG_DEFAULT_DENY)
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700740 dev_exception_rm(devcgroup, &ex);
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500741 else
742 rc = dev_exception_add(devcgroup, &ex);
743
744 if (rc)
745 break;
746 /* we only propagate new restrictions */
747 rc = propagate_exception(devcgroup, &ex);
748 break;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700749 default:
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500750 rc = -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700751 }
Aristeu Rozanskibd2953e2013-02-15 11:55:47 -0500752 return rc;
Paul Menagef92523e2008-07-25 01:47:03 -0700753}
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700754
Tejun Heo451af5042014-05-13 12:16:21 -0400755static ssize_t devcgroup_access_write(struct kernfs_open_file *of,
756 char *buf, size_t nbytes, loff_t off)
Paul Menagef92523e2008-07-25 01:47:03 -0700757{
758 int retval;
Li Zefanb4046f02009-04-02 16:57:32 -0700759
760 mutex_lock(&devcgroup_mutex);
Tejun Heo451af5042014-05-13 12:16:21 -0400761 retval = devcgroup_update_access(css_to_devcgroup(of_css(of)),
762 of_cft(of)->private, strstrip(buf));
Li Zefanb4046f02009-04-02 16:57:32 -0700763 mutex_unlock(&devcgroup_mutex);
Tejun Heo451af5042014-05-13 12:16:21 -0400764 return retval ?: nbytes;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700765}
766
767static struct cftype dev_cgroup_files[] = {
768 {
769 .name = "allow",
Tejun Heo451af5042014-05-13 12:16:21 -0400770 .write = devcgroup_access_write,
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700771 .private = DEVCG_ALLOW,
772 },
773 {
774 .name = "deny",
Tejun Heo451af5042014-05-13 12:16:21 -0400775 .write = devcgroup_access_write,
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700776 .private = DEVCG_DENY,
777 },
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700778 {
779 .name = "list",
Tejun Heo2da8ca82013-12-05 12:28:04 -0500780 .seq_show = devcgroup_seq_show,
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700781 .private = DEVCG_LIST,
782 },
Tejun Heo4baf6e32012-04-01 12:09:55 -0700783 { } /* terminate */
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700784};
785
Tejun Heo073219e2014-02-08 10:36:58 -0500786struct cgroup_subsys devices_cgrp_subsys = {
Tejun Heo92fb9742012-11-19 08:13:38 -0800787 .css_alloc = devcgroup_css_alloc,
788 .css_free = devcgroup_css_free,
Aristeu Rozanski1909554c2013-02-15 11:55:46 -0500789 .css_online = devcgroup_online,
790 .css_offline = devcgroup_offline,
Tejun Heo55779642014-07-15 11:05:09 -0400791 .legacy_cftypes = dev_cgroup_files,
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700792};
793
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700794/**
795 * __devcgroup_check_permission - checks if an inode operation is permitted
796 * @dev_cgroup: the dev cgroup to be tested against
797 * @type: device type
798 * @major: device major number
799 * @minor: device minor number
Roman Gushchin67e306f2017-11-05 08:15:30 -0500800 * @access: combination of DEVCG_ACC_WRITE, DEVCG_ACC_READ and DEVCG_ACC_MKNOD
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700801 *
802 * returns 0 on success, -EPERM case the operation is not permitted
803 */
Roman Gushchinecf8fec2017-11-05 08:15:31 -0500804int __devcgroup_check_permission(short type, u32 major, u32 minor,
805 short access)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700806{
Jiri Slaby8c9506d2012-10-25 13:37:34 -0700807 struct dev_cgroup *dev_cgroup;
Aristeu Rozanski79d71972014-04-21 12:13:03 -0400808 bool rc;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700809
Pavel Emelyanov4efd1a12008-07-25 01:47:07 -0700810 rcu_read_lock();
Jiri Slaby8c9506d2012-10-25 13:37:34 -0700811 dev_cgroup = task_devcgroup(current);
Aristeu Rozanski79d71972014-04-21 12:13:03 -0400812 if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW)
813 /* Can't match any of the exceptions, even partially */
814 rc = !match_exception_partial(&dev_cgroup->exceptions,
815 type, major, minor, access);
816 else
817 /* Need to match completely one exception to be allowed */
818 rc = match_exception(&dev_cgroup->exceptions, type, major,
819 minor, access);
Pavel Emelyanov4efd1a12008-07-25 01:47:07 -0700820 rcu_read_unlock();
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700821
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700822 if (!rc)
823 return -EPERM;
824
825 return 0;
826}