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 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); 53