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/version.h>
  10#include <linux/nsproxy.h>
  11#include <linux/user_namespace.h>
  12
  13struct user_namespace init_user_ns = {
  14        .kref = {
  15                .refcount       = ATOMIC_INIT(2),
  16        },
  17        .root_user = &root_user,
  18};
  19
  20EXPORT_SYMBOL_GPL(init_user_ns);
  21
  22#ifdef CONFIG_USER_NS
  23
  24/*
  25 * Clone a new ns copying an original user ns, setting refcount to 1
  26 * @old_ns: namespace to clone
  27 * Return NULL on error (failure to kmalloc), new ns otherwise
  28 */
  29static struct user_namespace *clone_user_ns(struct user_namespace *old_ns)
  30{
  31        struct user_namespace *ns;
  32        struct user_struct *new_user;
  33        int n;
  34
  35        ns = kmalloc(sizeof(struct user_namespace), GFP_KERNEL);
  36        if (!ns)
  37                return ERR_PTR(-ENOMEM);
  38
  39        kref_init(&ns->kref);
  40
  41        for (n = 0; n < UIDHASH_SZ; ++n)
  42                INIT_HLIST_HEAD(ns->uidhash_table + n);
  43
  44        /* Insert new root user.  */
  45        ns->root_user = alloc_uid(ns, 0);
  46        if (!ns->root_user) {
  47                kfree(ns);
  48                return ERR_PTR(-ENOMEM);
  49        }
  50
  51        /* Reset current->user with a new one */
  52        new_user = alloc_uid(ns, current->uid);
  53        if (!new_user) {
  54                free_uid(ns->root_user);
  55                kfree(ns);
  56                return ERR_PTR(-ENOMEM);
  57        }
  58
  59        switch_uid(new_user);
  60        return ns;
  61}
  62
  63struct user_namespace * copy_user_ns(int flags, struct user_namespace *old_ns)
  64{
  65        struct user_namespace *new_ns;
  66
  67        BUG_ON(!old_ns);
  68        get_user_ns(old_ns);
  69
  70        if (!(flags & CLONE_NEWUSER))
  71                return old_ns;
  72
  73        new_ns = clone_user_ns(old_ns);
  74
  75        put_user_ns(old_ns);
  76        return new_ns;
  77}
  78
  79void free_user_ns(struct kref *kref)
  80{
  81        struct user_namespace *ns;
  82
  83        ns = container_of(kref, struct user_namespace, kref);
  84        release_uids(ns);
  85        kfree(ns);
  86}
  87
  88#endif /* CONFIG_USER_NS */
  89