Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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kernel
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linux
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#include <linux/minmax.h>
7
8#include "lsm.h"
9
10/* amount of vm to protect from userspace access by both DAC and the LSM*/
11unsigned long mmap_min_addr;
12/* amount of vm to protect from userspace using CAP_SYS_RAWIO (DAC) */
13unsigned long dac_mmap_min_addr = CONFIG_DEFAULT_MMAP_MIN_ADDR;
14/* amount of vm to protect from userspace using the LSM = CONFIG_LSM_MMAP_MIN_ADDR */
15
16/*
17 * Update mmap_min_addr = max(dac_mmap_min_addr, CONFIG_LSM_MMAP_MIN_ADDR)
18 */
19static void update_mmap_min_addr(void)
20{
21#ifdef CONFIG_LSM_MMAP_MIN_ADDR
22 mmap_min_addr = umax(dac_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 */
32int 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
47static 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
57int __init min_addr_init(void)
58{
59 register_sysctl_init("vm", min_addr_sysctl_table);
60 update_mmap_min_addr();
61
62 return 0;
63}