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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 | ||
15 | static struct kmem_cache *user_ns_cachep __read_mostly; | |
16 | ||
17 | /* | |
18 | * Create a new user namespace, deriving the creator from the user in the | |
19 | * passed credentials, and replacing that user with the new root user for the | |
20 | * new namespace. | |
21 | * | |
22 | * This is called by copy_creds(), which will finish setting the target task's | |
23 | * credentials. | |
24 | */ | |
25 | int create_user_ns(struct cred *new) | |
26 | { | |
27 | struct user_namespace *ns; | |
28 | struct user_struct *root_user; | |
29 | int n; | |
30 | ||
31 | ns = kmem_cache_alloc(user_ns_cachep, GFP_KERNEL); | |
32 | if (!ns) | |
33 | return -ENOMEM; | |
34 | ||
35 | kref_init(&ns->kref); | |
36 | ||
37 | for (n = 0; n < UIDHASH_SZ; ++n) | |
38 | INIT_HLIST_HEAD(ns->uidhash_table + n); | |
39 | ||
40 | /* Alloc new root user. */ | |
41 | root_user = alloc_uid(ns, 0); | |
42 | if (!root_user) { | |
43 | kmem_cache_free(user_ns_cachep, ns); | |
44 | return -ENOMEM; | |
45 | } | |
46 | ||
47 | /* set the new root user in the credentials under preparation */ | |
48 | ns->creator = new->user; | |
49 | new->user = root_user; | |
50 | new->uid = new->euid = new->suid = new->fsuid = 0; | |
51 | new->gid = new->egid = new->sgid = new->fsgid = 0; | |
52 | put_group_info(new->group_info); | |
53 | new->group_info = get_group_info(&init_groups); | |
54 | #ifdef CONFIG_KEYS | |
55 | key_put(new->request_key_auth); | |
56 | new->request_key_auth = NULL; | |
57 | #endif | |
58 | /* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */ | |
59 | ||
60 | /* root_user holds a reference to ns, our reference can be dropped */ | |
61 | put_user_ns(ns); | |
62 | ||
63 | return 0; | |
64 | } | |
65 | ||
66 | /* | |
67 | * Deferred destructor for a user namespace. This is required because | |
68 | * free_user_ns() may be called with uidhash_lock held, but we need to call | |
69 | * back to free_uid() which will want to take the lock again. | |
70 | */ | |
71 | static void free_user_ns_work(struct work_struct *work) | |
72 | { | |
73 | struct user_namespace *ns = | |
74 | container_of(work, struct user_namespace, destroyer); | |
75 | free_uid(ns->creator); | |
76 | kmem_cache_free(user_ns_cachep, ns); | |
77 | } | |
78 | ||
79 | void free_user_ns(struct kref *kref) | |
80 | { | |
81 | struct user_namespace *ns = | |
82 | container_of(kref, struct user_namespace, kref); | |
83 | ||
84 | INIT_WORK(&ns->destroyer, free_user_ns_work); | |
85 | schedule_work(&ns->destroyer); | |
86 | } | |
87 | EXPORT_SYMBOL(free_user_ns); | |
88 | ||
89 | uid_t user_ns_map_uid(struct user_namespace *to, const struct cred *cred, uid_t uid) | |
90 | { | |
91 | struct user_namespace *tmp; | |
92 | ||
93 | if (likely(to == cred->user->user_ns)) | |
94 | return uid; | |
95 | ||
96 | ||
97 | /* Is cred->user the creator of the target user_ns | |
98 | * or the creator of one of it's parents? | |
99 | */ | |
100 | for ( tmp = to; tmp != &init_user_ns; | |
101 | tmp = tmp->creator->user_ns ) { | |
102 | if (cred->user == tmp->creator) { | |
103 | return (uid_t)0; | |
104 | } | |
105 | } | |
106 | ||
107 | /* No useful relationship so no mapping */ | |
108 | return overflowuid; | |
109 | } | |
110 | ||
111 | gid_t user_ns_map_gid(struct user_namespace *to, const struct cred *cred, gid_t gid) | |
112 | { | |
113 | struct user_namespace *tmp; | |
114 | ||
115 | if (likely(to == cred->user->user_ns)) | |
116 | return gid; | |
117 | ||
118 | /* Is cred->user the creator of the target user_ns | |
119 | * or the creator of one of it's parents? | |
120 | */ | |
121 | for ( tmp = to; tmp != &init_user_ns; | |
122 | tmp = tmp->creator->user_ns ) { | |
123 | if (cred->user == tmp->creator) { | |
124 | return (gid_t)0; | |
125 | } | |
126 | } | |
127 | ||
128 | /* No useful relationship so no mapping */ | |
129 | return overflowgid; | |
130 | } | |
131 | ||
132 | static __init int user_namespaces_init(void) | |
133 | { | |
134 | user_ns_cachep = KMEM_CACHE(user_namespace, SLAB_PANIC); | |
135 | return 0; | |
136 | } | |
137 | module_init(user_namespaces_init); |