// SPDX-License-Identifier: GPL-2.0#include <linux/init.h>#include <linux/mm.h>#include <linux/security.h>#include <linux/sysctl.h>#include <linux/minmax.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	mmap_min_addr = umax(dac_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(const 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 const struct ctl_table min_addr_sysctl_table[] = {	{		.procname	= "mmap_min_addr",		.data		= &dac_mmap_min_addr,		.maxlen		= sizeof(unsigned long),		.mode		= 0644,		.proc_handler	= mmap_min_addr_handler,	},}; static int __init mmap_min_addr_init(void){	register_sysctl_init("vm", min_addr_sysctl_table);	update_mmap_min_addr(); 	return 0;}pure_initcall(mmap_min_addr_init);