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*/
7 unsigned long mmap_min_addr;
8 /* amount of vm to protect from userspace using CAP_SYS_RAWIO (DAC) */
9 unsigned 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 */
update_mmap_min_addr(void)15 static 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 */
mmap_min_addr_handler(struct ctl_table * table,int write,void __user * buffer,size_t * lenp,loff_t * ppos)31 int 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
init_mmap_min_addr(void)46 static int __init init_mmap_min_addr(void)
47 {
48 update_mmap_min_addr();
49
50 return 0;
51 }
52 pure_initcall(init_mmap_min_addr);
53