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*/ 8 unsigned long mmap_min_addr; 9 /* amount of vm to protect from userspace using CAP_SYS_RAWIO (DAC) */ 10 unsigned 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 */ 16 static 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 */ 32 int 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 47 static int __init init_mmap_min_addr(void) 48 { 49 update_mmap_min_addr(); 50 51 return 0; 52 } 53 pure_initcall(init_mmap_min_addr); 54