blob: b08d20c66c2e17e0fa8333984df8eb4a82595e0b [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
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070028/*
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070029 * exception list locking rules:
Li Zefanb4046f02009-04-02 16:57:32 -070030 * hold devcgroup_mutex for update/read.
Lai Jiangshan47c59802008-10-18 20:28:07 -070031 * hold rcu_read_lock() for read.
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070032 */
33
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070034struct dev_exception_item {
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070035 u32 major, minor;
36 short type;
37 short access;
38 struct list_head list;
Pavel Emelyanov4efd1a12008-07-25 01:47:07 -070039 struct rcu_head rcu;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070040};
41
42struct dev_cgroup {
43 struct cgroup_subsys_state css;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070044 struct list_head exceptions;
Aristeu Rozanski5b7aa7d2012-10-25 13:37:38 -070045 enum {
46 DEVCG_DEFAULT_ALLOW,
47 DEVCG_DEFAULT_DENY,
48 } behavior;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070049};
50
Pavel Emelyanovb66862f2008-06-05 22:46:24 -070051static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s)
52{
53 return container_of(s, struct dev_cgroup, css);
54}
55
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070056static inline struct dev_cgroup *cgroup_to_devcgroup(struct cgroup *cgroup)
57{
Pavel Emelyanovb66862f2008-06-05 22:46:24 -070058 return css_to_devcgroup(cgroup_subsys_state(cgroup, devices_subsys_id));
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070059}
60
Paul Menagef92523e2008-07-25 01:47:03 -070061static inline struct dev_cgroup *task_devcgroup(struct task_struct *task)
62{
63 return css_to_devcgroup(task_subsys_state(task, devices_subsys_id));
64}
65
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070066struct cgroup_subsys devices_subsys;
67
Li Zefan761b3ef2012-01-31 13:47:36 +080068static int devcgroup_can_attach(struct cgroup *new_cgrp,
69 struct cgroup_taskset *set)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070070{
Tejun Heo2f7ee562011-12-12 18:12:21 -080071 struct task_struct *task = cgroup_taskset_first(set);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070072
Tejun Heo2f7ee562011-12-12 18:12:21 -080073 if (current != task && !capable(CAP_SYS_ADMIN))
74 return -EPERM;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070075 return 0;
76}
77
78/*
Li Zefanb4046f02009-04-02 16:57:32 -070079 * called under devcgroup_mutex
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070080 */
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070081static int dev_exceptions_copy(struct list_head *dest, struct list_head *orig)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070082{
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070083 struct dev_exception_item *ex, *tmp, *new;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070084
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070085 list_for_each_entry(ex, orig, list) {
86 new = kmemdup(ex, sizeof(*ex), GFP_KERNEL);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070087 if (!new)
88 goto free_and_exit;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070089 list_add_tail(&new->list, dest);
90 }
91
92 return 0;
93
94free_and_exit:
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -070095 list_for_each_entry_safe(ex, tmp, dest, list) {
96 list_del(&ex->list);
97 kfree(ex);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -070098 }
99 return -ENOMEM;
100}
101
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700102/*
Li Zefanb4046f02009-04-02 16:57:32 -0700103 * called under devcgroup_mutex
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700104 */
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700105static int dev_exception_add(struct dev_cgroup *dev_cgroup,
106 struct dev_exception_item *ex)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700107{
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700108 struct dev_exception_item *excopy, *walk;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700109
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700110 excopy = kmemdup(ex, sizeof(*ex), GFP_KERNEL);
111 if (!excopy)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700112 return -ENOMEM;
113
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700114 list_for_each_entry(walk, &dev_cgroup->exceptions, list) {
115 if (walk->type != ex->type)
Pavel Emelyanovd1ee2972008-06-05 22:46:28 -0700116 continue;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700117 if (walk->major != ex->major)
Pavel Emelyanovd1ee2972008-06-05 22:46:28 -0700118 continue;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700119 if (walk->minor != ex->minor)
Pavel Emelyanovd1ee2972008-06-05 22:46:28 -0700120 continue;
121
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700122 walk->access |= ex->access;
123 kfree(excopy);
124 excopy = NULL;
Pavel Emelyanovd1ee2972008-06-05 22:46:28 -0700125 }
126
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700127 if (excopy != NULL)
128 list_add_tail_rcu(&excopy->list, &dev_cgroup->exceptions);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700129 return 0;
130}
131
132/*
Li Zefanb4046f02009-04-02 16:57:32 -0700133 * called under devcgroup_mutex
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700134 */
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700135static void dev_exception_rm(struct dev_cgroup *dev_cgroup,
136 struct dev_exception_item *ex)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700137{
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700138 struct dev_exception_item *walk, *tmp;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700139
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700140 list_for_each_entry_safe(walk, tmp, &dev_cgroup->exceptions, list) {
141 if (walk->type != ex->type)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700142 continue;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700143 if (walk->major != ex->major)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700144 continue;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700145 if (walk->minor != ex->minor)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700146 continue;
147
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700148 walk->access &= ~ex->access;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700149 if (!walk->access) {
Pavel Emelyanov4efd1a12008-07-25 01:47:07 -0700150 list_del_rcu(&walk->list);
Lai Jiangshan6034f7e2011-03-15 18:07:57 +0800151 kfree_rcu(walk, rcu);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700152 }
153 }
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700154}
155
Aristeu Rozanski868539a2012-10-04 17:15:15 -0700156/**
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700157 * dev_exception_clean - frees all entries of the exception list
158 * @dev_cgroup: dev_cgroup with the exception list to be cleaned
Aristeu Rozanski868539a2012-10-04 17:15:15 -0700159 *
160 * called under devcgroup_mutex
161 */
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700162static void dev_exception_clean(struct dev_cgroup *dev_cgroup)
Aristeu Rozanski868539a2012-10-04 17:15:15 -0700163{
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700164 struct dev_exception_item *ex, *tmp;
Aristeu Rozanski868539a2012-10-04 17:15:15 -0700165
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700166 list_for_each_entry_safe(ex, tmp, &dev_cgroup->exceptions, list) {
Tejun Heo201e72a2012-11-06 09:17:37 -0800167 list_del_rcu(&ex->list);
168 kfree_rcu(ex, rcu);
Aristeu Rozanski868539a2012-10-04 17:15:15 -0700169 }
170}
171
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700172/*
173 * called from kernel/cgroup.c with cgroup_lock() held.
174 */
Li Zefan761b3ef2012-01-31 13:47:36 +0800175static struct cgroup_subsys_state *devcgroup_create(struct cgroup *cgroup)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700176{
177 struct dev_cgroup *dev_cgroup, *parent_dev_cgroup;
178 struct cgroup *parent_cgroup;
179 int ret;
180
181 dev_cgroup = kzalloc(sizeof(*dev_cgroup), GFP_KERNEL);
182 if (!dev_cgroup)
183 return ERR_PTR(-ENOMEM);
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700184 INIT_LIST_HEAD(&dev_cgroup->exceptions);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700185 parent_cgroup = cgroup->parent;
186
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700187 if (parent_cgroup == NULL)
Aristeu Rozanski5b7aa7d2012-10-25 13:37:38 -0700188 dev_cgroup->behavior = DEVCG_DEFAULT_ALLOW;
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700189 else {
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700190 parent_dev_cgroup = cgroup_to_devcgroup(parent_cgroup);
Li Zefanb4046f02009-04-02 16:57:32 -0700191 mutex_lock(&devcgroup_mutex);
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700192 ret = dev_exceptions_copy(&dev_cgroup->exceptions,
193 &parent_dev_cgroup->exceptions);
Aristeu Rozanski5b7aa7d2012-10-25 13:37:38 -0700194 dev_cgroup->behavior = parent_dev_cgroup->behavior;
Li Zefanb4046f02009-04-02 16:57:32 -0700195 mutex_unlock(&devcgroup_mutex);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700196 if (ret) {
197 kfree(dev_cgroup);
198 return ERR_PTR(ret);
199 }
200 }
201
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700202 return &dev_cgroup->css;
203}
204
Li Zefan761b3ef2012-01-31 13:47:36 +0800205static void devcgroup_destroy(struct cgroup *cgroup)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700206{
207 struct dev_cgroup *dev_cgroup;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700208
209 dev_cgroup = cgroup_to_devcgroup(cgroup);
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700210 dev_exception_clean(dev_cgroup);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700211 kfree(dev_cgroup);
212}
213
214#define DEVCG_ALLOW 1
215#define DEVCG_DENY 2
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700216#define DEVCG_LIST 3
217
Li Zefan17d213f2008-07-13 12:14:02 -0700218#define MAJMINLEN 13
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700219#define ACCLEN 4
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700220
221static void set_access(char *acc, short access)
222{
223 int idx = 0;
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700224 memset(acc, 0, ACCLEN);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700225 if (access & ACC_READ)
226 acc[idx++] = 'r';
227 if (access & ACC_WRITE)
228 acc[idx++] = 'w';
229 if (access & ACC_MKNOD)
230 acc[idx++] = 'm';
231}
232
233static char type_to_char(short type)
234{
235 if (type == DEV_ALL)
236 return 'a';
237 if (type == DEV_CHAR)
238 return 'c';
239 if (type == DEV_BLOCK)
240 return 'b';
241 return 'X';
242}
243
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700244static void set_majmin(char *str, unsigned m)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700245{
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700246 if (m == ~0)
Li Zefan7759fc92008-07-25 01:47:08 -0700247 strcpy(str, "*");
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700248 else
Li Zefan7759fc92008-07-25 01:47:08 -0700249 sprintf(str, "%u", m);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700250}
251
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700252static int devcgroup_seq_read(struct cgroup *cgroup, struct cftype *cft,
253 struct seq_file *m)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700254{
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700255 struct dev_cgroup *devcgroup = cgroup_to_devcgroup(cgroup);
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700256 struct dev_exception_item *ex;
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700257 char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN];
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700258
Pavel Emelyanov4efd1a12008-07-25 01:47:07 -0700259 rcu_read_lock();
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700260 /*
261 * To preserve the compatibility:
262 * - Only show the "all devices" when the default policy is to allow
263 * - List the exceptions in case the default policy is to deny
264 * This way, the file remains as a "whitelist of devices"
265 */
Aristeu Rozanski5b7aa7d2012-10-25 13:37:38 -0700266 if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) {
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700267 set_access(acc, ACC_MASK);
268 set_majmin(maj, ~0);
269 set_majmin(min, ~0);
270 seq_printf(m, "%c %s:%s %s\n", type_to_char(DEV_ALL),
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700271 maj, min, acc);
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700272 } else {
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700273 list_for_each_entry_rcu(ex, &devcgroup->exceptions, list) {
274 set_access(acc, ex->access);
275 set_majmin(maj, ex->major);
276 set_majmin(min, ex->minor);
277 seq_printf(m, "%c %s:%s %s\n", type_to_char(ex->type),
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700278 maj, min, acc);
279 }
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700280 }
Pavel Emelyanov4efd1a12008-07-25 01:47:07 -0700281 rcu_read_unlock();
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700282
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700283 return 0;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700284}
285
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700286/**
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700287 * may_access - verifies if a new exception is part of what is allowed
288 * by a dev cgroup based on the default policy +
289 * exceptions. This is used to make sure a child cgroup
290 * won't have more privileges than its parent or to
291 * verify if a certain access is allowed.
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700292 * @dev_cgroup: dev cgroup to be tested against
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700293 * @refex: new exception
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700294 */
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700295static int may_access(struct dev_cgroup *dev_cgroup,
296 struct dev_exception_item *refex)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700297{
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700298 struct dev_exception_item *ex;
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700299 bool match = false;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700300
Tejun Heo201e72a2012-11-06 09:17:37 -0800301 list_for_each_entry_rcu(ex, &dev_cgroup->exceptions, list) {
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700302 if ((refex->type & DEV_BLOCK) && !(ex->type & DEV_BLOCK))
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700303 continue;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700304 if ((refex->type & DEV_CHAR) && !(ex->type & DEV_CHAR))
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700305 continue;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700306 if (ex->major != ~0 && ex->major != refex->major)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700307 continue;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700308 if (ex->minor != ~0 && ex->minor != refex->minor)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700309 continue;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700310 if (refex->access & (~ex->access))
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700311 continue;
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700312 match = true;
313 break;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700314 }
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700315
316 /*
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700317 * In two cases we'll consider this new exception valid:
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700318 * - the dev cgroup has its default policy to allow + exception list:
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700319 * the new exception should *not* match any of the exceptions
Aristeu Rozanski5b7aa7d2012-10-25 13:37:38 -0700320 * (behavior == DEVCG_DEFAULT_ALLOW, !match)
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700321 * - the dev cgroup has its default policy to deny + exception list:
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700322 * the new exception *should* match the exceptions
Aristeu Rozanski5b7aa7d2012-10-25 13:37:38 -0700323 * (behavior == DEVCG_DEFAULT_DENY, match)
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700324 */
Aristeu Rozanski5b7aa7d2012-10-25 13:37:38 -0700325 if ((dev_cgroup->behavior == DEVCG_DEFAULT_DENY) == match)
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700326 return 1;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700327 return 0;
328}
329
330/*
331 * parent_has_perm:
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700332 * when adding a new allow rule to a device exception list, the rule
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700333 * must be allowed in the parent device
334 */
Paul Menagef92523e2008-07-25 01:47:03 -0700335static int parent_has_perm(struct dev_cgroup *childcg,
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700336 struct dev_exception_item *ex)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700337{
Paul Menagef92523e2008-07-25 01:47:03 -0700338 struct cgroup *pcg = childcg->css.cgroup->parent;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700339 struct dev_cgroup *parent;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700340
341 if (!pcg)
342 return 1;
343 parent = cgroup_to_devcgroup(pcg);
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700344 return may_access(parent, ex);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700345}
346
Aristeu Rozanski4cef7292012-10-25 13:37:45 -0700347/**
348 * may_allow_all - checks if it's possible to change the behavior to
349 * allow based on parent's rules.
350 * @parent: device cgroup's parent
351 * returns: != 0 in case it's allowed, 0 otherwise
352 */
353static inline int may_allow_all(struct dev_cgroup *parent)
354{
Aristeu Rozanski64e10472012-11-06 07:25:04 -0800355 if (!parent)
356 return 1;
Aristeu Rozanski4cef7292012-10-25 13:37:45 -0700357 return parent->behavior == DEVCG_DEFAULT_ALLOW;
358}
359
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700360/*
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700361 * Modify the exception list using allow/deny rules.
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700362 * CAP_SYS_ADMIN is needed for this. It's at least separate from CAP_MKNOD
363 * so we can give a container CAP_MKNOD to let it create devices but not
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700364 * modify the exception list.
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700365 * It seems likely we'll want to add a CAP_CONTAINER capability to allow
366 * us to also grant CAP_SYS_ADMIN to containers without giving away the
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700367 * device exception list controls, but for now we'll stick with CAP_SYS_ADMIN
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700368 *
369 * Taking rules away is always allowed (given CAP_SYS_ADMIN). Granting
370 * new access is only allowed if you're in the top-level cgroup, or your
371 * parent cgroup has the access you're asking for.
372 */
Paul Menagef92523e2008-07-25 01:47:03 -0700373static int devcgroup_update_access(struct dev_cgroup *devcgroup,
374 int filetype, const char *buffer)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700375{
Paul Menagef92523e2008-07-25 01:47:03 -0700376 const char *b;
Aristeu Rozanski26fd8402012-10-25 13:37:41 -0700377 char temp[12]; /* 11 + 1 characters needed for a u32 */
378 int count, rc;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700379 struct dev_exception_item ex;
Aristeu Rozanski4cef7292012-10-25 13:37:45 -0700380 struct cgroup *p = devcgroup->css.cgroup;
Aristeu Rozanski64e10472012-11-06 07:25:04 -0800381 struct dev_cgroup *parent = NULL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700382
383 if (!capable(CAP_SYS_ADMIN))
384 return -EPERM;
385
Aristeu Rozanski64e10472012-11-06 07:25:04 -0800386 if (p->parent)
387 parent = cgroup_to_devcgroup(p->parent);
388
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700389 memset(&ex, 0, sizeof(ex));
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700390 b = buffer;
391
392 switch (*b) {
393 case 'a':
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700394 switch (filetype) {
395 case DEVCG_ALLOW:
Aristeu Rozanski4cef7292012-10-25 13:37:45 -0700396 if (!may_allow_all(parent))
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700397 return -EPERM;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700398 dev_exception_clean(devcgroup);
Aristeu Rozanski64e10472012-11-06 07:25:04 -0800399 devcgroup->behavior = DEVCG_DEFAULT_ALLOW;
400 if (!parent)
401 break;
402
Aristeu Rozanski4cef7292012-10-25 13:37:45 -0700403 rc = dev_exceptions_copy(&devcgroup->exceptions,
404 &parent->exceptions);
405 if (rc)
406 return rc;
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700407 break;
408 case DEVCG_DENY:
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700409 dev_exception_clean(devcgroup);
Aristeu Rozanski5b7aa7d2012-10-25 13:37:38 -0700410 devcgroup->behavior = DEVCG_DEFAULT_DENY;
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700411 break;
412 default:
413 return -EINVAL;
414 }
415 return 0;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700416 case 'b':
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700417 ex.type = DEV_BLOCK;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700418 break;
419 case 'c':
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700420 ex.type = DEV_CHAR;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700421 break;
422 default:
Paul Menagef92523e2008-07-25 01:47:03 -0700423 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700424 }
425 b++;
Paul Menagef92523e2008-07-25 01:47:03 -0700426 if (!isspace(*b))
427 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700428 b++;
429 if (*b == '*') {
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700430 ex.major = ~0;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700431 b++;
432 } else if (isdigit(*b)) {
Aristeu Rozanski26fd8402012-10-25 13:37:41 -0700433 memset(temp, 0, sizeof(temp));
434 for (count = 0; count < sizeof(temp) - 1; count++) {
435 temp[count] = *b;
436 b++;
437 if (!isdigit(*b))
438 break;
439 }
440 rc = kstrtou32(temp, 10, &ex.major);
441 if (rc)
442 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700443 } else {
Paul Menagef92523e2008-07-25 01:47:03 -0700444 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700445 }
Paul Menagef92523e2008-07-25 01:47:03 -0700446 if (*b != ':')
447 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700448 b++;
449
450 /* read minor */
451 if (*b == '*') {
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700452 ex.minor = ~0;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700453 b++;
454 } else if (isdigit(*b)) {
Aristeu Rozanski26fd8402012-10-25 13:37:41 -0700455 memset(temp, 0, sizeof(temp));
456 for (count = 0; count < sizeof(temp) - 1; count++) {
457 temp[count] = *b;
458 b++;
459 if (!isdigit(*b))
460 break;
461 }
462 rc = kstrtou32(temp, 10, &ex.minor);
463 if (rc)
464 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700465 } else {
Paul Menagef92523e2008-07-25 01:47:03 -0700466 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700467 }
Paul Menagef92523e2008-07-25 01:47:03 -0700468 if (!isspace(*b))
469 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700470 for (b++, count = 0; count < 3; count++, b++) {
471 switch (*b) {
472 case 'r':
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700473 ex.access |= ACC_READ;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700474 break;
475 case 'w':
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700476 ex.access |= ACC_WRITE;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700477 break;
478 case 'm':
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700479 ex.access |= ACC_MKNOD;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700480 break;
481 case '\n':
482 case '\0':
483 count = 3;
484 break;
485 default:
Paul Menagef92523e2008-07-25 01:47:03 -0700486 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700487 }
488 }
489
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700490 switch (filetype) {
491 case DEVCG_ALLOW:
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700492 if (!parent_has_perm(devcgroup, &ex))
Paul Menagef92523e2008-07-25 01:47:03 -0700493 return -EPERM;
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700494 /*
495 * If the default policy is to allow by default, try to remove
496 * an matching exception instead. And be silent about it: we
497 * don't want to break compatibility
498 */
Aristeu Rozanski5b7aa7d2012-10-25 13:37:38 -0700499 if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) {
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700500 dev_exception_rm(devcgroup, &ex);
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700501 return 0;
502 }
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700503 return dev_exception_add(devcgroup, &ex);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700504 case DEVCG_DENY:
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700505 /*
506 * If the default policy is to deny by default, try to remove
507 * an matching exception instead. And be silent about it: we
508 * don't want to break compatibility
509 */
Aristeu Rozanski5b7aa7d2012-10-25 13:37:38 -0700510 if (devcgroup->behavior == DEVCG_DEFAULT_DENY) {
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700511 dev_exception_rm(devcgroup, &ex);
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700512 return 0;
513 }
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700514 return dev_exception_add(devcgroup, &ex);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700515 default:
Paul Menagef92523e2008-07-25 01:47:03 -0700516 return -EINVAL;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700517 }
Paul Menagef92523e2008-07-25 01:47:03 -0700518 return 0;
519}
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700520
Paul Menagef92523e2008-07-25 01:47:03 -0700521static int devcgroup_access_write(struct cgroup *cgrp, struct cftype *cft,
522 const char *buffer)
523{
524 int retval;
Li Zefanb4046f02009-04-02 16:57:32 -0700525
526 mutex_lock(&devcgroup_mutex);
Paul Menagef92523e2008-07-25 01:47:03 -0700527 retval = devcgroup_update_access(cgroup_to_devcgroup(cgrp),
528 cft->private, buffer);
Li Zefanb4046f02009-04-02 16:57:32 -0700529 mutex_unlock(&devcgroup_mutex);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700530 return retval;
531}
532
533static struct cftype dev_cgroup_files[] = {
534 {
535 .name = "allow",
Paul Menagef92523e2008-07-25 01:47:03 -0700536 .write_string = devcgroup_access_write,
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700537 .private = DEVCG_ALLOW,
538 },
539 {
540 .name = "deny",
Paul Menagef92523e2008-07-25 01:47:03 -0700541 .write_string = devcgroup_access_write,
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700542 .private = DEVCG_DENY,
543 },
Serge E. Hallyn29486df2008-04-29 01:00:14 -0700544 {
545 .name = "list",
546 .read_seq_string = devcgroup_seq_read,
547 .private = DEVCG_LIST,
548 },
Tejun Heo4baf6e32012-04-01 12:09:55 -0700549 { } /* terminate */
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700550};
551
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700552struct cgroup_subsys devices_subsys = {
553 .name = "devices",
554 .can_attach = devcgroup_can_attach,
555 .create = devcgroup_create,
Justin P. Mattockc5b60b52010-04-21 00:02:11 -0700556 .destroy = devcgroup_destroy,
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700557 .subsys_id = devices_subsys_id,
Tejun Heo4baf6e32012-04-01 12:09:55 -0700558 .base_cftypes = dev_cgroup_files,
Tejun Heo8c7f6ed2012-09-13 12:20:58 -0700559
560 /*
561 * While devices cgroup has the rudimentary hierarchy support which
562 * checks the parent's restriction, it doesn't properly propagates
563 * config changes in ancestors to their descendents. A child
564 * should only be allowed to add more restrictions to the parent's
565 * configuration. Fix it and remove the following.
566 */
567 .broken_hierarchy = true,
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700568};
569
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700570/**
571 * __devcgroup_check_permission - checks if an inode operation is permitted
572 * @dev_cgroup: the dev cgroup to be tested against
573 * @type: device type
574 * @major: device major number
575 * @minor: device minor number
576 * @access: combination of ACC_WRITE, ACC_READ and ACC_MKNOD
577 *
578 * returns 0 on success, -EPERM case the operation is not permitted
579 */
Jiri Slaby8c9506d2012-10-25 13:37:34 -0700580static int __devcgroup_check_permission(short type, u32 major, u32 minor,
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700581 short access)
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700582{
Jiri Slaby8c9506d2012-10-25 13:37:34 -0700583 struct dev_cgroup *dev_cgroup;
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700584 struct dev_exception_item ex;
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700585 int rc;
586
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700587 memset(&ex, 0, sizeof(ex));
588 ex.type = type;
589 ex.major = major;
590 ex.minor = minor;
591 ex.access = access;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700592
Pavel Emelyanov4efd1a12008-07-25 01:47:07 -0700593 rcu_read_lock();
Jiri Slaby8c9506d2012-10-25 13:37:34 -0700594 dev_cgroup = task_devcgroup(current);
Aristeu Rozanskidb9aeca2012-10-04 17:15:20 -0700595 rc = may_access(dev_cgroup, &ex);
Pavel Emelyanov4efd1a12008-07-25 01:47:07 -0700596 rcu_read_unlock();
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700597
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700598 if (!rc)
599 return -EPERM;
600
601 return 0;
602}
603
604int __devcgroup_inode_permission(struct inode *inode, int mask)
605{
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700606 short type, access = 0;
607
608 if (S_ISBLK(inode->i_mode))
609 type = DEV_BLOCK;
610 if (S_ISCHR(inode->i_mode))
611 type = DEV_CHAR;
612 if (mask & MAY_WRITE)
613 access |= ACC_WRITE;
614 if (mask & MAY_READ)
615 access |= ACC_READ;
616
Jiri Slaby8c9506d2012-10-25 13:37:34 -0700617 return __devcgroup_check_permission(type, imajor(inode), iminor(inode),
618 access);
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700619}
620
621int devcgroup_inode_mknod(int mode, dev_t dev)
622{
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700623 short type;
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700624
Serge E. Hallyn0b82ac32009-01-07 18:07:46 -0800625 if (!S_ISBLK(mode) && !S_ISCHR(mode))
626 return 0;
627
Aristeu Rozanskiad676072012-10-04 17:15:17 -0700628 if (S_ISBLK(mode))
629 type = DEV_BLOCK;
630 else
631 type = DEV_CHAR;
Li Zefan36fd71d2008-09-02 14:35:52 -0700632
Jiri Slaby8c9506d2012-10-25 13:37:34 -0700633 return __devcgroup_check_permission(type, MAJOR(dev), MINOR(dev),
634 ACC_MKNOD);
Li Zefan36fd71d2008-09-02 14:35:52 -0700635
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700636}