linux/security/min_addr.c
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   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*/
   7unsigned long mmap_min_addr;
   8/* amount of vm to protect from userspace using CAP_SYS_RAWIO (DAC) */
   9unsigned 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 */
  15static 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 */
  31int 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
  46static int __init init_mmap_min_addr(void)
  47{
  48        update_mmap_min_addr();
  49
  50        return 0;
  51}
  52pure_initcall(init_mmap_min_addr);
  53
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