// SPDX-License-Identifier: GPL-2.0 #include <linux/init.h> #include <linux/mm.h> #include <linux/security.h> #include <linux/sysctl.h> /* amount of vm to protect from userspace access by both DAC and the LSM*/ unsigned long mmap_min_addr; /* amount of vm to protect from userspace using CAP_SYS_RAWIO (DAC) */ unsigned long dac_mmap_min_addr = CONFIG_DEFAULT_MMAP_MIN_ADDR; /* amount of vm to protect from userspace using the LSM = CONFIG_LSM_MMAP_MIN_ADDR */ /* * Update mmap_min_addr = max(dac_mmap_min_addr, CONFIG_LSM_MMAP_MIN_ADDR) */ static void update_mmap_min_addr(void) { #ifdef CONFIG_LSM_MMAP_MIN_ADDR if (dac_mmap_min_addr > CONFIG_LSM_MMAP_MIN_ADDR) mmap_min_addr = dac_mmap_min_addr; else mmap_min_addr = CONFIG_LSM_MMAP_MIN_ADDR; #else mmap_min_addr = dac_mmap_min_addr; #endif } /* * sysctl handler which just sets dac_mmap_min_addr = the new value and then * calls update_mmap_min_addr() so non MAP_FIXED hints get rounded properly */ int mmap_min_addr_handler(struct ctl_table *table, int write, void *buffer, size_t *lenp, loff_t *ppos) { int ret; if (write && !capable(CAP_SYS_RAWIO)) return -EPERM; ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); update_mmap_min_addr(); return ret; } static int __init init_mmap_min_addr(void) { update_mmap_min_addr(); return 0; } pure_initcall(init_mmap_min_addr);