LXR linux/security/min

   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*/
   8unsigned long mmap_min_addr;
   9/* amount of vm to protect from userspace using CAP_SYS_RAWIO (DAC) */
  10unsigned 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 */
  16static 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 */
  32int mmap_min_addr_handler(struct ctl_table *table, int write,
  33                          void __user *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 int __init init_mmap_min_addr(void)
  48{
  49        update_mmap_min_addr();
  50
  51        return 0;
  52}
  53pure_initcall(init_mmap_min_addr);
  54