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/*
* securelevel.c - support for generic kernel lockdown
*
* Copyright Nebula, Inc <matthew.garrett@nebula.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
*/
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/security.h>
#include <linux/uaccess.h>
static int securelevel;
static DEFINE_SPINLOCK(securelevel_lock);
#define MAX_SECURELEVEL 1
int get_securelevel(void)
{
return securelevel;
}
EXPORT_SYMBOL(get_securelevel);
int set_securelevel(int new_securelevel)
{
int ret = 0;
spin_lock(&securelevel_lock);
if ((securelevel == -1) || (new_securelevel < securelevel) ||
(new_securelevel > MAX_SECURELEVEL)) {
ret = -EINVAL;
goto out;
}
securelevel = new_securelevel;
out:
spin_unlock(&securelevel_lock);
return ret;
}
EXPORT_SYMBOL(set_securelevel);
static ssize_t securelevel_read(struct file *filp, char __user *buf,
size_t count, loff_t *ppos)
{
char tmpbuf[12];
ssize_t length;
length = scnprintf(tmpbuf, sizeof(tmpbuf), "%d", securelevel);
return simple_read_from_buffer(buf, count, ppos, tmpbuf, length);
}
static ssize_t securelevel_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
char *page = NULL;
ssize_t length;
int new_securelevel;
length = -ENOMEM;
if (count >= PAGE_SIZE)
goto out;
length = -EINVAL;
if (*ppos != 0)
goto out;
length = -ENOMEM;
page = (char *)get_zeroed_page(GFP_KERNEL);
if (!page)
goto out;
length = -EFAULT;
if (copy_from_user(page, buf, count))
goto out;
length = -EINVAL;
if (sscanf(page, "%d", &new_securelevel) != 1)
goto out;
length = set_securelevel(new_securelevel);
if (length)
goto out;
length = count;
out:
free_page((unsigned long) page);
return length;
}
static const struct file_operations securelevel_fops = {
.read = securelevel_read,
.write = securelevel_write,
.llseek = generic_file_llseek,
};
static __init int setup_securelevel(void)
{
struct dentry *securelevel_file;
securelevel_file = securityfs_create_file("securelevel",
S_IWUSR | S_IRUGO,
NULL, NULL,
&securelevel_fops);
if (IS_ERR(securelevel_file))
return PTR_ERR(securelevel_file);
return 0;
}
late_initcall(setup_securelevel);
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