When I execute insmod for the kernel module object file of the following C code, the entire system hangs. The module replaces the reference to original chroot system call with a new one in the sys_call_table. The syscall_table address is correct as per System.map(which returns 2 values for sys_call_table, surprisingly). I am on a VM running CentOS 6.6 with kernel version 2.6.32-504. #include <linux/init.h> #include <linux/module.h> #include <linux/kernel.h> #include <linux/errno.h> #include <linux/types.h> #include <linux/unistd.h> #include <asm/cacheflush.h> #include <asm/page.h> #include <asm/current.h> #include <linux/sched.h> #include <linux/kallsyms.h> unsigned long *syscall_table = (unsigned long *)0xffffffff81600560; asmlinkage int (*original_chroot)(const char __user *); asmlinkage int new_chroot(const char __user *filename){ printk(KERN_ALERT "CHROOT HIJACKED"); return (*original_chroot)(filename); } static int init(void) { printk(KERN_ALERT "\nHIJACK INIT\n"); original_chroot = (void *)syscall_table[__NR_chroot]; syscall_table[__NR_chroot] = new_chroot; return 0; } static void exit(void) { syscall_table[__NR_chroot] = original_chroot; printk(KERN_ALERT "MODULE EXIT\n"); } module_init(init); module_exit(exit);