1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/init.h>
3 #include <linux/mm.h>
4 #include <linux/security.h>
5 #include <linux/sysctl.h>
6
7 /* amount of vm to protect from userspace access by both DAC and the LSM*/
8 unsigned long mmap_min_addr;
9 /* amount of vm to protect from userspace using CAP_SYS_RAWIO (DAC) */
10 unsigned long dac_mmap_min_addr = CONFIG_DEFAULT_MMAP_MIN_ADDR;
11 /* amount of vm to protect from userspace using the LSM = CONFIG_LSM_MMAP_MIN_ADDR */
12
13 /*
14 * Update mmap_min_addr = max(dac_mmap_min_addr, CONFIG_LSM_MMAP_MIN_ADDR)
15 */
update_mmap_min_addr(void)16 static void update_mmap_min_addr(void)
17 {
18 #ifdef CONFIG_LSM_MMAP_MIN_ADDR
19 if (dac_mmap_min_addr > CONFIG_LSM_MMAP_MIN_ADDR)
20 mmap_min_addr = dac_mmap_min_addr;
21 else
22 mmap_min_addr = CONFIG_LSM_MMAP_MIN_ADDR;
23 #else
24 mmap_min_addr = dac_mmap_min_addr;
25 #endif
26 }
27
28 /*
29 * sysctl handler which just sets dac_mmap_min_addr = the new value and then
30 * calls update_mmap_min_addr() so non MAP_FIXED hints get rounded properly
31 */
mmap_min_addr_handler(const struct ctl_table * table,int write,void * buffer,size_t * lenp,loff_t * ppos)32 int mmap_min_addr_handler(const struct ctl_table *table, int write,
33 void *buffer, size_t *lenp, loff_t *ppos)
34 {
35 int ret;
36
37 if (write && !capable(CAP_SYS_RAWIO))
38 return -EPERM;
39
40 ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
41
42 update_mmap_min_addr();
43
44 return ret;
45 }
46
47 static const struct ctl_table min_addr_sysctl_table[] = {
48 {
49 .procname = "mmap_min_addr",
50 .data = &dac_mmap_min_addr,
51 .maxlen = sizeof(unsigned long),
52 .mode = 0644,
53 .proc_handler = mmap_min_addr_handler,
54 },
55 };
56
init_mmap_min_addr(void)57 static int __init init_mmap_min_addr(void)
58 {
59 register_sysctl_init("vm", min_addr_sysctl_table);
60 update_mmap_min_addr();
61
62 return 0;
63 }
64 pure_initcall(init_mmap_min_addr);
65