Root/security/min_addr.c

1#include <linux/init.h>
2#include <linux/mm.h>
3#include <linux/security.h>
4#include <linux/sysctl.h>
5
6/* amount of vm to protect from userspace access by both DAC and the LSM*/
7unsigned long mmap_min_addr;
8/* amount of vm to protect from userspace using CAP_SYS_RAWIO (DAC) */
9unsigned long dac_mmap_min_addr = CONFIG_DEFAULT_MMAP_MIN_ADDR;
10/* amount of vm to protect from userspace using the LSM = CONFIG_LSM_MMAP_MIN_ADDR */
11
12/*
13 * Update mmap_min_addr = max(dac_mmap_min_addr, CONFIG_LSM_MMAP_MIN_ADDR)
14 */
15static void update_mmap_min_addr(void)
16{
17#ifdef CONFIG_LSM_MMAP_MIN_ADDR
18    if (dac_mmap_min_addr > CONFIG_LSM_MMAP_MIN_ADDR)
19        mmap_min_addr = dac_mmap_min_addr;
20    else
21        mmap_min_addr = CONFIG_LSM_MMAP_MIN_ADDR;
22#else
23    mmap_min_addr = dac_mmap_min_addr;
24#endif
25}
26
27/*
28 * sysctl handler which just sets dac_mmap_min_addr = the new value and then
29 * calls update_mmap_min_addr() so non MAP_FIXED hints get rounded properly
30 */
31int mmap_min_addr_handler(struct ctl_table *table, int write,
32              void __user *buffer, size_t *lenp, loff_t *ppos)
33{
34    int ret;
35
36    if (write && !capable(CAP_SYS_RAWIO))
37        return -EPERM;
38
39    ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
40
41    update_mmap_min_addr();
42
43    return ret;
44}
45
46static int __init init_mmap_min_addr(void)
47{
48    update_mmap_min_addr();
49
50    return 0;
51}
52pure_initcall(init_mmap_min_addr);
53

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