1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
|
// SPDX-License-Identifier: GPL-2.0-only
/*
* Module and Firmware Pinning Security Module
*
* Copyright 2011-2016 Google Inc.
*
* Author: Kees Cook <keescook@chromium.org>
*/
#define pr_fmt(fmt) "LoadPin: " fmt
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/kernel_read_file.h>
#include <linux/lsm_hooks.h>
#include <linux/mount.h>
#include <linux/blkdev.h>
#include <linux/path.h>
#include <linux/sched.h> /* current */
#include <linux/string_helpers.h>
static void report_load(const char *origin, struct file *file, char *operation)
{
char *cmdline, *pathname;
pathname = kstrdup_quotable_file(file, GFP_KERNEL);
cmdline = kstrdup_quotable_cmdline(current, GFP_KERNEL);
pr_notice("%s %s obj=%s%s%s pid=%d cmdline=%s%s%s\n",
origin, operation,
(pathname && pathname[0] != '<') ? "\"" : "",
pathname,
(pathname && pathname[0] != '<') ? "\"" : "",
task_pid_nr(current),
cmdline ? "\"" : "", cmdline, cmdline ? "\"" : "");
kfree(cmdline);
kfree(pathname);
}
static int enforce = IS_ENABLED(CONFIG_SECURITY_LOADPIN_ENFORCE);
static char *exclude_read_files[READING_MAX_ID];
static int ignore_read_file_id[READING_MAX_ID] __ro_after_init;
static struct super_block *pinned_root;
static DEFINE_SPINLOCK(pinned_root_spinlock);
#ifdef CONFIG_SYSCTL
static struct ctl_path loadpin_sysctl_path[] = {
{ .procname = "kernel", },
{ .procname = "loadpin", },
{ }
};
static struct ctl_table loadpin_sysctl_table[] = {
{
.procname = "enforce",
.data = &enforce,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_ONE,
},
{ }
};
/*
* This must be called after early kernel init, since then the rootdev
* is available.
*/
static void check_pinning_enforcement(struct super_block *mnt_sb)
{
bool ro = false;
/*
* If load pinning is not enforced via a read-only block
* device, allow sysctl to change modes for testing.
*/
if (mnt_sb->s_bdev) {
char bdev[BDEVNAME_SIZE];
ro = bdev_read_only(mnt_sb->s_bdev);
bdevname(mnt_sb->s_bdev, bdev);
pr_info("%s (%u:%u): %s\n", bdev,
MAJOR(mnt_sb->s_bdev->bd_dev),
MINOR(mnt_sb->s_bdev->bd_dev),
ro ? "read-only" : "writable");
} else
pr_info("mnt_sb lacks block device, treating as: writable\n");
if (!ro) {
if (!register_sysctl_paths(loadpin_sysctl_path,
loadpin_sysctl_table))
pr_notice("sysctl registration failed!\n");
else
pr_info("enforcement can be disabled.\n");
} else
pr_info("load pinning engaged.\n");
}
#else
static void check_pinning_enforcement(struct super_block *mnt_sb)
{
pr_info("load pinning engaged.\n");
}
#endif
static void loadpin_sb_free_security(struct super_block *mnt_sb)
{
/*
* When unmounting the filesystem we were using for load
* pinning, we acknowledge the superblock release, but make sure
* no other modules or firmware can be loaded.
*/
if (!IS_ERR_OR_NULL(pinned_root) && mnt_sb == pinned_root) {
pinned_root = ERR_PTR(-EIO);
pr_info("umount pinned fs: refusing further loads\n");
}
}
static int loadpin_read_file(struct file *file, enum kernel_read_file_id id)
{
struct super_block *load_root;
const char *origin = kernel_read_file_id_str(id);
/* If the file id is excluded, ignore the pinning. */
if ((unsigned int)id < ARRAY_SIZE(ignore_read_file_id) &&
ignore_read_file_id[id]) {
report_load(origin, file, "pinning-excluded");
return 0;
}
/* This handles the older init_module API that has a NULL file. */
if (!file) {
if (!enforce) {
report_load(origin, NULL, "old-api-pinning-ignored");
return 0;
}
report_load(origin, NULL, "old-api-denied");
return -EPERM;
}
load_root = file->f_path.mnt->mnt_sb;
/* First loaded module/firmware defines the root for all others. */
spin_lock(&pinned_root_spinlock);
/*
* pinned_root is only NULL at startup. Otherwise, it is either
* a valid reference, or an ERR_PTR.
*/
if (!pinned_root) {
pinned_root = load_root;
/*
* Unlock now since it's only pinned_root we care about.
* In the worst case, we will (correctly) report pinning
* failures before we have announced that pinning is
* enforcing. This would be purely cosmetic.
*/
spin_unlock(&pinned_root_spinlock);
check_pinning_enforcement(pinned_root);
report_load(origin, file, "pinned");
} else {
spin_unlock(&pinned_root_spinlock);
}
if (IS_ERR_OR_NULL(pinned_root) || load_root != pinned_root) {
if (unlikely(!enforce)) {
report_load(origin, file, "pinning-ignored");
return 0;
}
report_load(origin, file, "denied");
return -EPERM;
}
return 0;
}
static int loadpin_load_data(enum kernel_load_data_id id)
{
return loadpin_read_file(NULL, (enum kernel_read_file_id) id);
}
static struct security_hook_list loadpin_hooks[] __lsm_ro_after_init = {
LSM_HOOK_INIT(sb_free_security, loadpin_sb_free_security),
LSM_HOOK_INIT(kernel_read_file, loadpin_read_file),
LSM_HOOK_INIT(kernel_load_data, loadpin_load_data),
};
static void __init parse_exclude(void)
{
int i, j;
char *cur;
/*
* Make sure all the arrays stay within expected sizes. This
* is slightly weird because kernel_read_file_str[] includes
* READING_MAX_ID, which isn't actually meaningful here.
*/
BUILD_BUG_ON(ARRAY_SIZE(exclude_read_files) !=
ARRAY_SIZE(ignore_read_file_id));
BUILD_BUG_ON(ARRAY_SIZE(kernel_read_file_str) <
ARRAY_SIZE(ignore_read_file_id));
for (i = 0; i < ARRAY_SIZE(exclude_read_files); i++) {
cur = exclude_read_files[i];
if (!cur)
break;
if (*cur == '\0')
continue;
for (j = 0; j < ARRAY_SIZE(ignore_read_file_id); j++) {
if (strcmp(cur, kernel_read_file_str[j]) == 0) {
pr_info("excluding: %s\n",
kernel_read_file_str[j]);
ignore_read_file_id[j] = 1;
/*
* Can not break, because one read_file_str
* may map to more than on read_file_id.
*/
}
}
}
}
static int __init loadpin_init(void)
{
pr_info("ready to pin (currently %senforcing)\n",
enforce ? "" : "not ");
parse_exclude();
security_add_hooks(loadpin_hooks, ARRAY_SIZE(loadpin_hooks), "loadpin");
return 0;
}
DEFINE_LSM(loadpin) = {
.name = "loadpin",
.init = loadpin_init,
};
/* Should not be mutable after boot, so not listed in sysfs (perm == 0). */
module_param(enforce, int, 0);
MODULE_PARM_DESC(enforce, "Enforce module/firmware pinning");
module_param_array_named(exclude, exclude_read_files, charp, NULL, 0);
MODULE_PARM_DESC(exclude, "Exclude pinning specific read file types");
|
