#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/fs_struct.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/reboot.h>
#include <linux/delay.h>
#include <linux/proc_fs.h>
#include <asm/uaccess.h>
#include <linux/sysrq.h>
#include <linux/timer.h>
#include <linux/time.h>
#include <linux/lglock.h>
#include <linux/init.h>
#include <linux/idr.h>
#include <linux/namei.h>
#include <linux/bitops.h>
#include <linux/mnt_namespace.h>
#include <linux/path.h>
#include <linux/dcache.h>
#include <linux/spinlock.h>
#include <linux/completion.h>
#include <linux/sched.h>
#include <linux/seq_file.h>
#include <linux/file.h>
#include <linux/kprobes.h>
#include <linux/kallsyms.h>
#include <linux/nsproxy.h>
#include "mount.h"

#define VERSION_STR "0.0.1"

#ifndef CONFIG_X86_64
#error "This code does not support your architecture"
#endif

MODULE_AUTHOR("Sapan Bhatia <sapanb@cs.princeton.edu>");
MODULE_DESCRIPTION("Hack to enable mount namespace switching via setns. Based on a patch by Eric Biederman.");
MODULE_LICENSE("GPL");
MODULE_VERSION(VERSION_STR);

struct proc_dir_entry *proc_entry;

static void *mntns_get(struct task_struct *task)
{
       struct mnt_namespace *ns;
       rcu_read_lock();
       ns = task->nsproxy->mnt_ns;
       atomic_inc(&ns->count);
       rcu_read_unlock();
       return ns;
}

void (*put_mnt_ns2)(struct mnt_namespace *ns);

static void mntns_put(void *ns)
{
       (*put_mnt_ns2)(ns);
}

static int mntns_install(struct nsproxy *nsproxy, void *ns)
{
       struct fs_struct *fs = current->fs;
       struct mnt_namespace *mnt_ns = ns;
       struct path root;

       if (fs->users != 1)
               return -EINVAL;

       atomic_inc(&mnt_ns->count);
       (*put_mnt_ns2)(nsproxy->mnt_ns);
       nsproxy->mnt_ns = mnt_ns;

       root.mnt    = &mnt_ns->root->mnt;
       root.dentry = mnt_ns->root->mnt.mnt_root;
       path_get(&root);
       while(d_mountpoint(root.dentry) && follow_down(&root))
               ;

       path_get(&root);
       path_get(&root);
       path_put(&fs->root);
       path_put(&fs->pwd);
       fs->root = root;
       fs->pwd  = root;
       path_put(&root);

       return 0;
}

const struct proc_ns_operations mntns_operations = {
       .name           = "mnt_ns",
       .get            = mntns_get,
       .put            = mntns_put,
       .install        = mntns_install,
};

void (*free_nsproxy2)(struct nsproxy *ns);

struct nsproxy * (*create_new_namespaces)(unsigned long flags,
			struct task_struct *tsk, struct fs_struct *new_fs);

void (*switch_task_namespaces2)(struct task_struct *p, struct nsproxy *new);

static int setns(struct task_struct *reftask) {
        const struct proc_ns_operations *ops;
        struct task_struct *tsk = current;
        struct nsproxy *new_nsproxy;
        int err;

        if (!capable(CAP_SYS_ADMIN))
            return -EPERM;

        err = -EINVAL;
        ops = &mntns_operations;

        new_nsproxy = (*create_new_namespaces)(0, tsk, tsk->fs);
        if (IS_ERR(new_nsproxy)) {
            err = PTR_ERR(new_nsproxy);
            goto out;
        }

        err = ops->install(new_nsproxy, reftask->nsproxy->mnt_ns);
        if (err) {
            (*free_nsproxy2)(new_nsproxy);
            goto out;
        }
        (*switch_task_namespaces2)(tsk, new_nsproxy);
        return 0;
out:
        return err;

}

static void __exit lxcsu_exit(void)
{
	remove_proc_entry("lxcsu",NULL);
	printk("Procprotect: Stopped lxcsu.\n");
}

int lxcsu_write(struct file *file, const char *buffer, unsigned long count, void *data) {
	char pidname[PATH_MAX];
    int pid;
    struct pid *p;
    char **s;
    struct task_struct *task;

	if (current->nsproxy->mnt_ns!=init_task.nsproxy->mnt_ns)
		return -EPERM;

	if (copy_from_user(pidname, buffer, count)) {
		return -EFAULT;
	}
	if (count && (pidname[count-1]==10 || pidname[count-1]==13)) {
		pidname[count-1]='\0';
	}
	else
		pidname[count]='\0';

    pid = simple_strtol(pidname,s,10);
    p = find_vpid(pid);
    task = get_pid_task(p,PIDTYPE_PID);
    if (task) {
        setns(task);
    }
    else {
        printk(KERN_CRIT "Task %d not found",pid);
    }

	return count;
}


static int __init lxcsu_init(void)
{
		int ret=0;
        printk("Mntsu: starting lxcsu version %s.\n",
	       VERSION_STR);

        free_nsproxy2 = kallsyms_lookup_name("free_nsproxy");
        printk(KERN_CRIT "free_nsproxy = %x",free_nsproxy2);

        switch_task_namespaces2 = kallsyms_lookup_name("switch_task_namespaces");
        printk(KERN_CRIT "switch_task_namespaces = %x",switch_task_namespaces2);

        create_new_namespaces = kallsyms_lookup_name("create_new_namespaces");
        printk(KERN_CRIT "create_new_namespaces = %x",create_new_namespaces);

        put_mnt_ns2 = kallsyms_lookup_name("put_mnt_ns");
        printk(KERN_CRIT "Put mnt ns = %x",put_mnt_ns2);

        proc_entry = create_proc_entry("lxcsu", 0644, NULL);
	    proc_entry->write_proc = lxcsu_write;
        return ret;
}

module_init(lxcsu_init);
module_exit(lxcsu_exit);