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dbec2846 EB |
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/stat.h> | |
9 | #include <linux/sysctl.h> | |
10 | #include <linux/slab.h> | |
f6b2db1a | 11 | #include <linux/hash.h> |
dbec2846 EB |
12 | #include <linux/user_namespace.h> |
13 | ||
f6b2db1a EB |
14 | #define UCOUNTS_HASHTABLE_BITS 10 |
15 | static struct hlist_head ucounts_hashtable[(1 << UCOUNTS_HASHTABLE_BITS)]; | |
16 | static DEFINE_SPINLOCK(ucounts_lock); | |
17 | ||
18 | #define ucounts_hashfn(ns, uid) \ | |
19 | hash_long((unsigned long)__kuid_val(uid) + (unsigned long)(ns), \ | |
20 | UCOUNTS_HASHTABLE_BITS) | |
21 | #define ucounts_hashentry(ns, uid) \ | |
22 | (ucounts_hashtable + ucounts_hashfn(ns, uid)) | |
23 | ||
24 | ||
dbec2846 EB |
25 | #ifdef CONFIG_SYSCTL |
26 | static struct ctl_table_set * | |
27 | set_lookup(struct ctl_table_root *root) | |
28 | { | |
29 | return ¤t_user_ns()->set; | |
30 | } | |
31 | ||
32 | static int set_is_seen(struct ctl_table_set *set) | |
33 | { | |
34 | return ¤t_user_ns()->set == set; | |
35 | } | |
36 | ||
37 | static int set_permissions(struct ctl_table_header *head, | |
38 | struct ctl_table *table) | |
39 | { | |
40 | struct user_namespace *user_ns = | |
41 | container_of(head->set, struct user_namespace, set); | |
42 | int mode; | |
43 | ||
44 | /* Allow users with CAP_SYS_RESOURCE unrestrained access */ | |
45 | if (ns_capable(user_ns, CAP_SYS_RESOURCE)) | |
46 | mode = (table->mode & S_IRWXU) >> 6; | |
47 | else | |
48 | /* Allow all others at most read-only access */ | |
49 | mode = table->mode & S_IROTH; | |
50 | return (mode << 6) | (mode << 3) | mode; | |
51 | } | |
52 | ||
53 | static struct ctl_table_root set_root = { | |
54 | .lookup = set_lookup, | |
55 | .permissions = set_permissions, | |
56 | }; | |
57 | ||
b376c3e1 EB |
58 | static int zero = 0; |
59 | static int int_max = INT_MAX; | |
25f9c081 EB |
60 | #define UCOUNT_ENTRY(name) \ |
61 | { \ | |
62 | .procname = name, \ | |
63 | .maxlen = sizeof(int), \ | |
64 | .mode = 0644, \ | |
65 | .proc_handler = proc_dointvec_minmax, \ | |
66 | .extra1 = &zero, \ | |
67 | .extra2 = &int_max, \ | |
68 | } | |
f6b2db1a | 69 | static struct ctl_table user_table[] = { |
25f9c081 | 70 | UCOUNT_ENTRY("max_user_namespaces"), |
f333c700 | 71 | UCOUNT_ENTRY("max_pid_namespaces"), |
f7af3d1c | 72 | UCOUNT_ENTRY("max_uts_namespaces"), |
aba35661 | 73 | UCOUNT_ENTRY("max_ipc_namespaces"), |
70328660 | 74 | UCOUNT_ENTRY("max_net_namespaces"), |
537f7ccb | 75 | UCOUNT_ENTRY("max_mnt_namespaces"), |
d08311dd | 76 | UCOUNT_ENTRY("max_cgroup_namespaces"), |
dbec2846 EB |
77 | { } |
78 | }; | |
79 | #endif /* CONFIG_SYSCTL */ | |
80 | ||
81 | bool setup_userns_sysctls(struct user_namespace *ns) | |
82 | { | |
83 | #ifdef CONFIG_SYSCTL | |
84 | struct ctl_table *tbl; | |
85 | setup_sysctl_set(&ns->set, &set_root, set_is_seen); | |
f6b2db1a | 86 | tbl = kmemdup(user_table, sizeof(user_table), GFP_KERNEL); |
dbec2846 | 87 | if (tbl) { |
25f9c081 EB |
88 | int i; |
89 | for (i = 0; i < UCOUNT_COUNTS; i++) { | |
90 | tbl[i].data = &ns->ucount_max[i]; | |
91 | } | |
f6b2db1a | 92 | ns->sysctls = __register_sysctl_table(&ns->set, "user", tbl); |
dbec2846 EB |
93 | } |
94 | if (!ns->sysctls) { | |
95 | kfree(tbl); | |
96 | retire_sysctl_set(&ns->set); | |
97 | return false; | |
98 | } | |
99 | #endif | |
100 | return true; | |
101 | } | |
102 | ||
103 | void retire_userns_sysctls(struct user_namespace *ns) | |
104 | { | |
105 | #ifdef CONFIG_SYSCTL | |
106 | struct ctl_table *tbl; | |
107 | ||
108 | tbl = ns->sysctls->ctl_table_arg; | |
109 | unregister_sysctl_table(ns->sysctls); | |
110 | retire_sysctl_set(&ns->set); | |
111 | kfree(tbl); | |
112 | #endif | |
113 | } | |
114 | ||
f6b2db1a EB |
115 | static struct ucounts *find_ucounts(struct user_namespace *ns, kuid_t uid, struct hlist_head *hashent) |
116 | { | |
117 | struct ucounts *ucounts; | |
118 | ||
119 | hlist_for_each_entry(ucounts, hashent, node) { | |
120 | if (uid_eq(ucounts->uid, uid) && (ucounts->ns == ns)) | |
121 | return ucounts; | |
122 | } | |
123 | return NULL; | |
124 | } | |
125 | ||
126 | static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid) | |
127 | { | |
128 | struct hlist_head *hashent = ucounts_hashentry(ns, uid); | |
129 | struct ucounts *ucounts, *new; | |
130 | ||
131 | spin_lock(&ucounts_lock); | |
132 | ucounts = find_ucounts(ns, uid, hashent); | |
133 | if (!ucounts) { | |
134 | spin_unlock(&ucounts_lock); | |
135 | ||
136 | new = kzalloc(sizeof(*new), GFP_KERNEL); | |
137 | if (!new) | |
138 | return NULL; | |
139 | ||
140 | new->ns = ns; | |
141 | new->uid = uid; | |
142 | atomic_set(&new->count, 0); | |
143 | ||
144 | spin_lock(&ucounts_lock); | |
145 | ucounts = find_ucounts(ns, uid, hashent); | |
146 | if (ucounts) { | |
147 | kfree(new); | |
148 | } else { | |
149 | hlist_add_head(&new->node, hashent); | |
150 | ucounts = new; | |
151 | } | |
152 | } | |
153 | if (!atomic_add_unless(&ucounts->count, 1, INT_MAX)) | |
154 | ucounts = NULL; | |
155 | spin_unlock(&ucounts_lock); | |
156 | return ucounts; | |
157 | } | |
158 | ||
159 | static void put_ucounts(struct ucounts *ucounts) | |
160 | { | |
161 | if (atomic_dec_and_test(&ucounts->count)) { | |
162 | spin_lock(&ucounts_lock); | |
163 | hlist_del_init(&ucounts->node); | |
164 | spin_unlock(&ucounts_lock); | |
165 | ||
166 | kfree(ucounts); | |
167 | } | |
168 | } | |
169 | ||
b376c3e1 EB |
170 | static inline bool atomic_inc_below(atomic_t *v, int u) |
171 | { | |
172 | int c, old; | |
173 | c = atomic_read(v); | |
174 | for (;;) { | |
175 | if (unlikely(c >= u)) | |
176 | return false; | |
177 | old = atomic_cmpxchg(v, c, c+1); | |
178 | if (likely(old == c)) | |
179 | return true; | |
180 | c = old; | |
181 | } | |
182 | } | |
183 | ||
25f9c081 EB |
184 | struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid, |
185 | enum ucount_type type) | |
b376c3e1 | 186 | { |
f6b2db1a EB |
187 | struct ucounts *ucounts, *iter, *bad; |
188 | struct user_namespace *tns; | |
189 | ucounts = get_ucounts(ns, uid); | |
190 | for (iter = ucounts; iter; iter = tns->ucounts) { | |
191 | int max; | |
192 | tns = iter->ns; | |
25f9c081 EB |
193 | max = READ_ONCE(tns->ucount_max[type]); |
194 | if (!atomic_inc_below(&iter->ucount[type], max)) | |
b376c3e1 EB |
195 | goto fail; |
196 | } | |
f6b2db1a | 197 | return ucounts; |
b376c3e1 | 198 | fail: |
f6b2db1a EB |
199 | bad = iter; |
200 | for (iter = ucounts; iter != bad; iter = iter->ns->ucounts) | |
25f9c081 | 201 | atomic_dec(&iter->ucount[type]); |
b376c3e1 | 202 | |
f6b2db1a EB |
203 | put_ucounts(ucounts); |
204 | return NULL; | |
b376c3e1 EB |
205 | } |
206 | ||
25f9c081 | 207 | void dec_ucount(struct ucounts *ucounts, enum ucount_type type) |
b376c3e1 | 208 | { |
f6b2db1a EB |
209 | struct ucounts *iter; |
210 | for (iter = ucounts; iter; iter = iter->ns->ucounts) { | |
25f9c081 | 211 | int dec = atomic_dec_if_positive(&iter->ucount[type]); |
b376c3e1 EB |
212 | WARN_ON_ONCE(dec < 0); |
213 | } | |
f6b2db1a | 214 | put_ucounts(ucounts); |
b376c3e1 EB |
215 | } |
216 | ||
dbec2846 EB |
217 | static __init int user_namespace_sysctl_init(void) |
218 | { | |
219 | #ifdef CONFIG_SYSCTL | |
f6b2db1a | 220 | static struct ctl_table_header *user_header; |
dbec2846 EB |
221 | static struct ctl_table empty[1]; |
222 | /* | |
f6b2db1a | 223 | * It is necessary to register the user directory in the |
dbec2846 EB |
224 | * default set so that registrations in the child sets work |
225 | * properly. | |
226 | */ | |
f6b2db1a EB |
227 | user_header = register_sysctl("user", empty); |
228 | BUG_ON(!user_header); | |
dbec2846 EB |
229 | BUG_ON(!setup_userns_sysctls(&init_user_ns)); |
230 | #endif | |
231 | return 0; | |
232 | } | |
233 | subsys_initcall(user_namespace_sysctl_init); | |
234 | ||
235 |