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
8 #include <linux/export.h>
9 #include <linux/nsproxy.h>
10 #include <linux/slab.h>
11 #include <linux/user_namespace.h>
12 #include <linux/highuid.h>
13 #include <linux/cred.h>
14 #include <linux/securebits.h>
16 static struct kmem_cache *user_ns_cachep __read_mostly;
19 * Create a new user namespace, deriving the creator from the user in the
20 * passed credentials, and replacing that user with the new root user for the
23 * This is called by copy_creds(), which will finish setting the target task's
26 int create_user_ns(struct cred *new)
28 struct user_namespace *ns, *parent_ns = new->user_ns;
29 struct user_struct *root_user;
32 ns = kmem_cache_alloc(user_ns_cachep, GFP_KERNEL);
38 for (n = 0; n < UIDHASH_SZ; ++n)
39 INIT_HLIST_HEAD(ns->uidhash_table + n);
41 /* Alloc new root user. */
42 root_user = alloc_uid(ns, 0);
44 kmem_cache_free(user_ns_cachep, ns);
48 /* set the new root user in the credentials under preparation */
49 ns->parent = parent_ns;
50 ns->creator = new->user;
51 new->user = root_user;
52 new->uid = new->euid = new->suid = new->fsuid = 0;
53 new->gid = new->egid = new->sgid = new->fsgid = 0;
54 put_group_info(new->group_info);
55 new->group_info = get_group_info(&init_groups);
56 /* Start with the same capabilities as init but useless for doing
57 * anything as the capabilities are bound to the new user namespace.
59 new->securebits = SECUREBITS_DEFAULT;
60 new->cap_inheritable = CAP_EMPTY_SET;
61 new->cap_permitted = CAP_FULL_SET;
62 new->cap_effective = CAP_FULL_SET;
63 new->cap_bset = CAP_FULL_SET;
65 key_put(new->request_key_auth);
66 new->request_key_auth = NULL;
68 /* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */
70 /* Leave the reference to our user_ns with the new cred */
77 * Deferred destructor for a user namespace. This is required because
78 * free_user_ns() may be called with uidhash_lock held, but we need to call
79 * back to free_uid() which will want to take the lock again.
81 static void free_user_ns_work(struct work_struct *work)
83 struct user_namespace *parent, *ns =
84 container_of(work, struct user_namespace, destroyer);
86 free_uid(ns->creator);
87 kmem_cache_free(user_ns_cachep, ns);
91 void free_user_ns(struct kref *kref)
93 struct user_namespace *ns =
94 container_of(kref, struct user_namespace, kref);
96 INIT_WORK(&ns->destroyer, free_user_ns_work);
97 schedule_work(&ns->destroyer);
99 EXPORT_SYMBOL(free_user_ns);
101 uid_t user_ns_map_uid(struct user_namespace *to, const struct cred *cred, uid_t uid)
103 struct user_namespace *tmp;
105 if (likely(to == cred->user_ns))
109 /* Is cred->user the creator of the target user_ns
110 * or the creator of one of it's parents?
112 for ( tmp = to; tmp != &init_user_ns; tmp = tmp->parent ) {
113 if (cred->user == tmp->creator) {
118 /* No useful relationship so no mapping */
122 gid_t user_ns_map_gid(struct user_namespace *to, const struct cred *cred, gid_t gid)
124 struct user_namespace *tmp;
126 if (likely(to == cred->user_ns))
129 /* Is cred->user the creator of the target user_ns
130 * or the creator of one of it's parents?
132 for ( tmp = to; tmp != &init_user_ns; tmp = tmp->parent ) {
133 if (cred->user == tmp->creator) {
138 /* No useful relationship so no mapping */
142 static __init int user_namespaces_init(void)
144 user_ns_cachep = KMEM_CACHE(user_namespace, SLAB_PANIC);
147 module_init(user_namespaces_init);