1 // SPDX-License-Identifier: GPL-2.0
2 /* Lock down the kernel
4 * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public Licence
9 * as published by the Free Software Foundation; either version
10 * 2 of the Licence, or (at your option) any later version.
13 #include <linux/security.h>
14 #include <linux/export.h>
15 #include <linux/lsm_hooks.h>
17 static enum lockdown_reason kernel_locked_down;
19 static const char *const lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = {
20 [LOCKDOWN_NONE] = "none",
21 [LOCKDOWN_MODULE_SIGNATURE] = "unsigned module loading",
22 [LOCKDOWN_DEV_MEM] = "/dev/mem,kmem,port",
23 [LOCKDOWN_KEXEC] = "kexec of unsigned images",
24 [LOCKDOWN_HIBERNATION] = "hibernation",
25 [LOCKDOWN_PCI_ACCESS] = "direct PCI access",
26 [LOCKDOWN_IOPORT] = "raw io port access",
27 [LOCKDOWN_MSR] = "raw MSR access",
28 [LOCKDOWN_ACPI_TABLES] = "modifying ACPI tables",
29 [LOCKDOWN_PCMCIA_CIS] = "direct PCMCIA CIS storage",
30 [LOCKDOWN_TIOCSSERIAL] = "reconfiguration of serial port IO",
31 [LOCKDOWN_MODULE_PARAMETERS] = "unsafe module parameters",
32 [LOCKDOWN_MMIOTRACE] = "unsafe mmio",
33 [LOCKDOWN_DEBUGFS] = "debugfs access",
34 [LOCKDOWN_INTEGRITY_MAX] = "integrity",
35 [LOCKDOWN_KCORE] = "/proc/kcore access",
36 [LOCKDOWN_KPROBES] = "use of kprobes",
37 [LOCKDOWN_BPF_READ] = "use of bpf to read kernel RAM",
38 [LOCKDOWN_PERF] = "unsafe use of perf",
39 [LOCKDOWN_TRACEFS] = "use of tracefs",
40 [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality",
43 static const enum lockdown_reason lockdown_levels[] = {LOCKDOWN_NONE,
44 LOCKDOWN_INTEGRITY_MAX,
45 LOCKDOWN_CONFIDENTIALITY_MAX};
48 * Put the kernel into lock-down mode.
50 static int lock_kernel_down(const char *where, enum lockdown_reason level)
52 if (kernel_locked_down >= level)
55 kernel_locked_down = level;
56 pr_notice("Kernel is locked down from %s; see man kernel_lockdown.7\n",
61 static int __init lockdown_param(char *level)
66 if (strcmp(level, "integrity") == 0)
67 lock_kernel_down("command line", LOCKDOWN_INTEGRITY_MAX);
68 else if (strcmp(level, "confidentiality") == 0)
69 lock_kernel_down("command line", LOCKDOWN_CONFIDENTIALITY_MAX);
76 early_param("lockdown", lockdown_param);
79 * lockdown_is_locked_down - Find out if the kernel is locked down
80 * @what: Tag to use in notice generated if lockdown is in effect
82 static int lockdown_is_locked_down(enum lockdown_reason what)
84 if (WARN(what >= LOCKDOWN_CONFIDENTIALITY_MAX,
85 "Invalid lockdown reason"))
88 if (kernel_locked_down >= what) {
89 if (lockdown_reasons[what])
90 pr_notice("Lockdown: %s: %s is restricted; see man kernel_lockdown.7\n",
91 current->comm, lockdown_reasons[what]);
98 static struct security_hook_list lockdown_hooks[] __lsm_ro_after_init = {
99 LSM_HOOK_INIT(locked_down, lockdown_is_locked_down),
102 static int __init lockdown_lsm_init(void)
104 #if defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_INTEGRITY)
105 lock_kernel_down("Kernel configuration", LOCKDOWN_INTEGRITY_MAX);
106 #elif defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_CONFIDENTIALITY)
107 lock_kernel_down("Kernel configuration", LOCKDOWN_CONFIDENTIALITY_MAX);
109 security_add_hooks(lockdown_hooks, ARRAY_SIZE(lockdown_hooks),
114 static ssize_t lockdown_read(struct file *filp, char __user *buf, size_t count,
120 for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) {
121 enum lockdown_reason level = lockdown_levels[i];
123 if (lockdown_reasons[level]) {
124 const char *label = lockdown_reasons[level];
126 if (kernel_locked_down == level)
127 offset += sprintf(temp+offset, "[%s] ", label);
129 offset += sprintf(temp+offset, "%s ", label);
133 /* Convert the last space to a newline if needed. */
135 temp[offset-1] = '\n';
137 return simple_read_from_buffer(buf, count, ppos, temp, strlen(temp));
140 static ssize_t lockdown_write(struct file *file, const char __user *buf,
141 size_t n, loff_t *ppos)
144 int i, len, err = -EINVAL;
146 state = memdup_user_nul(buf, n);
148 return PTR_ERR(state);
151 if (len && state[len-1] == '\n') {
156 for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) {
157 enum lockdown_reason level = lockdown_levels[i];
158 const char *label = lockdown_reasons[level];
160 if (label && !strcmp(state, label))
161 err = lock_kernel_down("securityfs", level);
165 return err ? err : n;
168 static const struct file_operations lockdown_ops = {
169 .read = lockdown_read,
170 .write = lockdown_write,
173 static int __init lockdown_secfs_init(void)
175 struct dentry *dentry;
177 dentry = securityfs_create_file("lockdown", 0600, NULL, NULL,
179 return PTR_ERR_OR_ZERO(dentry);
182 core_initcall(lockdown_secfs_init);
184 #ifdef CONFIG_SECURITY_LOCKDOWN_LSM_EARLY
185 DEFINE_EARLY_LSM(lockdown) = {
187 DEFINE_LSM(lockdown) = {
190 .init = lockdown_lsm_init,