security/min_addr.c

   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  */
  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  */
  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 (!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
  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);