LXR linux/kernel/user

   1/*
   2 *  This program is free software; you can redistribute it and/or
   3 *  modify it under the terms of the GNU General Public License as
   4 *  published by the Free Software Foundation, version 2 of the
   5 *  License.
   6 */
   7
   8#include <linux/module.h>
   9#include <linux/nsproxy.h>
  10#include <linux/slab.h>
  11#include <linux/user_namespace.h>
  12#include <linux/cred.h>
  13
  14/*
  15 * Create a new user namespace, deriving the creator from the user in the
  16 * passed credentials, and replacing that user with the new root user for the
  17 * new namespace.
  18 *
  19 * This is called by copy_creds(), which will finish setting the target task's
  20 * credentials.
  21 */
  22int create_user_ns(struct cred *new)
  23{
  24        struct user_namespace *ns;
  25        struct user_struct *root_user;
  26        int n;
  27
  28        ns = kmalloc(sizeof(struct user_namespace), GFP_KERNEL);
  29        if (!ns)
  30                return -ENOMEM;
  31
  32        kref_init(&ns->kref);
  33
  34        for (n = 0; n < UIDHASH_SZ; ++n)
  35                INIT_HLIST_HEAD(ns->uidhash_table + n);
  36
  37        /* Alloc new root user.  */
  38        root_user = alloc_uid(ns, 0);
  39        if (!root_user) {
  40                kfree(ns);
  41                return -ENOMEM;
  42        }
  43
  44        /* set the new root user in the credentials under preparation */
  45        ns->creator = new->user;
  46        new->user = root_user;
  47        new->uid = new->euid = new->suid = new->fsuid = 0;
  48        new->gid = new->egid = new->sgid = new->fsgid = 0;
  49        put_group_info(new->group_info);
  50        new->group_info = get_group_info(&init_groups);
  51#ifdef CONFIG_KEYS
  52        key_put(new->request_key_auth);
  53        new->request_key_auth = NULL;
  54#endif
  55        /* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */
  56
  57        /* alloc_uid() incremented the userns refcount.  Just set it to 1 */
  58        kref_set(&ns->kref, 1);
  59
  60        return 0;
  61}
  62
  63/*
  64 * Deferred destructor for a user namespace.  This is required because
  65 * free_user_ns() may be called with uidhash_lock held, but we need to call
  66 * back to free_uid() which will want to take the lock again.
  67 */
  68static void free_user_ns_work(struct work_struct *work)
  69{
  70        struct user_namespace *ns =
  71                container_of(work, struct user_namespace, destroyer);
  72        free_uid(ns->creator);
  73        kfree(ns);
  74}
  75
  76void free_user_ns(struct kref *kref)
  77{
  78        struct user_namespace *ns =
  79                container_of(kref, struct user_namespace, kref);
  80
  81        INIT_WORK(&ns->destroyer, free_user_ns_work);
  82        schedule_work(&ns->destroyer);
  83}
  84EXPORT_SYMBOL(free_user_ns);
  85