| 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/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> |
| 15 | |
| 16 | static struct kmem_cache *user_ns_cachep __read_mostly; |
| 17 | |
| 18 | /* |
| 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 |
| 21 | * new namespace. |
| 22 | * |
| 23 | * This is called by copy_creds(), which will finish setting the target task's |
| 24 | * credentials. |
| 25 | */ |
| 26 | int create_user_ns(struct cred *new) |
| 27 | { |
| 28 | struct user_namespace *ns, *parent_ns = new->user_ns; |
| 29 | struct user_struct *root_user; |
| 30 | kuid_t owner = make_kuid(new->user_ns, new->euid); |
| 31 | kgid_t group = make_kgid(new->user_ns, new->egid); |
| 32 | |
| 33 | /* The creator needs a mapping in the parent user namespace |
| 34 | * or else we won't be able to reasonably tell userspace who |
| 35 | * created a user_namespace. |
| 36 | */ |
| 37 | if (!kuid_has_mapping(parent_ns, owner) || |
| 38 | !kgid_has_mapping(parent_ns, group)) |
| 39 | return -EPERM; |
| 40 | |
| 41 | ns = kmem_cache_alloc(user_ns_cachep, GFP_KERNEL); |
| 42 | if (!ns) |
| 43 | return -ENOMEM; |
| 44 | |
| 45 | kref_init(&ns->kref); |
| 46 | |
| 47 | /* Alloc new root user. */ |
| 48 | root_user = alloc_uid(make_kuid(ns, 0)); |
| 49 | if (!root_user) { |
| 50 | kmem_cache_free(user_ns_cachep, ns); |
| 51 | return -ENOMEM; |
| 52 | } |
| 53 | |
| 54 | /* set the new root user in the credentials under preparation */ |
| 55 | ns->parent = parent_ns; |
| 56 | ns->owner = owner; |
| 57 | ns->group = group; |
| 58 | free_uid(new->user); |
| 59 | new->user = root_user; |
| 60 | new->uid = new->euid = new->suid = new->fsuid = 0; |
| 61 | new->gid = new->egid = new->sgid = new->fsgid = 0; |
| 62 | put_group_info(new->group_info); |
| 63 | new->group_info = get_group_info(&init_groups); |
| 64 | /* Start with the same capabilities as init but useless for doing |
| 65 | * anything as the capabilities are bound to the new user namespace. |
| 66 | */ |
| 67 | new->securebits = SECUREBITS_DEFAULT; |
| 68 | new->cap_inheritable = CAP_EMPTY_SET; |
| 69 | new->cap_permitted = CAP_FULL_SET; |
| 70 | new->cap_effective = CAP_FULL_SET; |
| 71 | new->cap_bset = CAP_FULL_SET; |
| 72 | #ifdef CONFIG_KEYS |
| 73 | key_put(new->request_key_auth); |
| 74 | new->request_key_auth = NULL; |
| 75 | #endif |
| 76 | /* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */ |
| 77 | |
| 78 | /* Leave the new->user_ns reference with the new user namespace. */ |
| 79 | /* Leave the reference to our user_ns with the new cred. */ |
| 80 | new->user_ns = ns; |
| 81 | |
| 82 | return 0; |
| 83 | } |
| 84 | |
| 85 | void free_user_ns(struct kref *kref) |
| 86 | { |
| 87 | struct user_namespace *parent, *ns = |
| 88 | container_of(kref, struct user_namespace, kref); |
| 89 | |
| 90 | parent = ns->parent; |
| 91 | kmem_cache_free(user_ns_cachep, ns); |
| 92 | put_user_ns(parent); |
| 93 | } |
| 94 | EXPORT_SYMBOL(free_user_ns); |
| 95 | |
| 96 | uid_t user_ns_map_uid(struct user_namespace *to, const struct cred *cred, uid_t uid) |
| 97 | { |
| 98 | struct user_namespace *tmp; |
| 99 | |
| 100 | if (likely(to == cred->user_ns)) |
| 101 | return uid; |
| 102 | |
| 103 | /* Is cred->user the creator of the target user_ns |
| 104 | * or the creator of one of it's parents? |
| 105 | */ |
| 106 | for ( tmp = to; tmp != &init_user_ns; tmp = tmp->parent ) { |
| 107 | if (uid_eq(cred->user->uid, tmp->owner)) { |
| 108 | return (uid_t)0; |
| 109 | } |
| 110 | } |
| 111 | |
| 112 | /* No useful relationship so no mapping */ |
| 113 | return overflowuid; |
| 114 | } |
| 115 | |
| 116 | gid_t user_ns_map_gid(struct user_namespace *to, const struct cred *cred, gid_t gid) |
| 117 | { |
| 118 | struct user_namespace *tmp; |
| 119 | |
| 120 | if (likely(to == cred->user_ns)) |
| 121 | return gid; |
| 122 | |
| 123 | /* Is cred->user the creator of the target user_ns |
| 124 | * or the creator of one of it's parents? |
| 125 | */ |
| 126 | for ( tmp = to; tmp != &init_user_ns; tmp = tmp->parent ) { |
| 127 | if (uid_eq(cred->user->uid, tmp->owner)) { |
| 128 | return (gid_t)0; |
| 129 | } |
| 130 | } |
| 131 | |
| 132 | /* No useful relationship so no mapping */ |
| 133 | return overflowgid; |
| 134 | } |
| 135 | |
| 136 | static __init int user_namespaces_init(void) |
| 137 | { |
| 138 | user_ns_cachep = KMEM_CACHE(user_namespace, SLAB_PANIC); |
| 139 | return 0; |
| 140 | } |
| 141 | module_init(user_namespaces_init); |