user_namespace.c
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/*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation, version 2 of the
* License.
*/
#include <linux/module.h>
#include <linux/nsproxy.h>
#include <linux/slab.h>
#include <linux/user_namespace.h>
#include <linux/cred.h>
/*
* Create a new user namespace, deriving the creator from the user in the
* passed credentials, and replacing that user with the new root user for the
* new namespace.
*
* This is called by copy_creds(), which will finish setting the target task's
* credentials.
*/
int create_user_ns(struct cred *new)
{
struct user_namespace *ns;
struct user_struct *root_user;
int n;
ns = kmalloc(sizeof(struct user_namespace), GFP_KERNEL);
if (!ns)
return -ENOMEM;
kref_init(&ns->kref);
for (n = 0; n < UIDHASH_SZ; ++n)
INIT_HLIST_HEAD(ns->uidhash_table + n);
/* Alloc new root user. */
root_user = alloc_uid(ns, 0);
if (!root_user) {
kfree(ns);
return -ENOMEM;
}
/* set the new root user in the credentials under preparation */
ns->creator = new->user;
new->user = root_user;
new->uid = new->euid = new->suid = new->fsuid = 0;
new->gid = new->egid = new->sgid = new->fsgid = 0;
put_group_info(new->group_info);
new->group_info = get_group_info(&init_groups);
#ifdef CONFIG_KEYS
key_put(new->request_key_auth);
new->request_key_auth = NULL;
#endif
/* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */
/* alloc_uid() incremented the userns refcount. Just set it to 1 */
kref_set(&ns->kref, 1);
return 0;
}
/*
* Deferred destructor for a user namespace. This is required because
* free_user_ns() may be called with uidhash_lock held, but we need to call
* back to free_uid() which will want to take the lock again.
*/
static void free_user_ns_work(struct work_struct *work)
{
struct user_namespace *ns =
container_of(work, struct user_namespace, destroyer);
free_uid(ns->creator);
kfree(ns);
}
void free_user_ns(struct kref *kref)
{
struct user_namespace *ns =
container_of(kref, struct user_namespace, kref);
INIT_WORK(&ns->destroyer, free_user_ns_work);
schedule_work(&ns->destroyer);
}
EXPORT_SYMBOL(free_user_ns);