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(struct ctl_table * table,int write,void * buffer,size_t * lenp,loff_t * ppos)32 int mmap_min_addr_handler(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 
init_mmap_min_addr(void)47 static int __init init_mmap_min_addr(void)
48 {
49 	update_mmap_min_addr();
50 
51 	return 0;
52 }
53 pure_initcall(init_mmap_min_addr);
54