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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; | |
1cce1eea | 60 | #define UCOUNT_ENTRY(name) \ |
25f9c081 EB |
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"), |
1cce1eea NB |
77 | #ifdef CONFIG_INOTIFY_USER |
78 | UCOUNT_ENTRY("max_inotify_instances"), | |
79 | UCOUNT_ENTRY("max_inotify_watches"), | |
80 | #endif | |
dbec2846 EB |
81 | { } |
82 | }; | |
83 | #endif /* CONFIG_SYSCTL */ | |
84 | ||
85 | bool setup_userns_sysctls(struct user_namespace *ns) | |
86 | { | |
87 | #ifdef CONFIG_SYSCTL | |
88 | struct ctl_table *tbl; | |
89 | setup_sysctl_set(&ns->set, &set_root, set_is_seen); | |
f6b2db1a | 90 | tbl = kmemdup(user_table, sizeof(user_table), GFP_KERNEL); |
dbec2846 | 91 | if (tbl) { |
25f9c081 EB |
92 | int i; |
93 | for (i = 0; i < UCOUNT_COUNTS; i++) { | |
94 | tbl[i].data = &ns->ucount_max[i]; | |
95 | } | |
f6b2db1a | 96 | ns->sysctls = __register_sysctl_table(&ns->set, "user", tbl); |
dbec2846 EB |
97 | } |
98 | if (!ns->sysctls) { | |
99 | kfree(tbl); | |
100 | retire_sysctl_set(&ns->set); | |
101 | return false; | |
102 | } | |
103 | #endif | |
104 | return true; | |
105 | } | |
106 | ||
107 | void retire_userns_sysctls(struct user_namespace *ns) | |
108 | { | |
109 | #ifdef CONFIG_SYSCTL | |
110 | struct ctl_table *tbl; | |
111 | ||
112 | tbl = ns->sysctls->ctl_table_arg; | |
113 | unregister_sysctl_table(ns->sysctls); | |
114 | retire_sysctl_set(&ns->set); | |
115 | kfree(tbl); | |
116 | #endif | |
117 | } | |
118 | ||
f6b2db1a EB |
119 | static struct ucounts *find_ucounts(struct user_namespace *ns, kuid_t uid, struct hlist_head *hashent) |
120 | { | |
121 | struct ucounts *ucounts; | |
122 | ||
123 | hlist_for_each_entry(ucounts, hashent, node) { | |
124 | if (uid_eq(ucounts->uid, uid) && (ucounts->ns == ns)) | |
125 | return ucounts; | |
126 | } | |
127 | return NULL; | |
128 | } | |
129 | ||
130 | static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid) | |
131 | { | |
132 | struct hlist_head *hashent = ucounts_hashentry(ns, uid); | |
133 | struct ucounts *ucounts, *new; | |
134 | ||
880a3854 | 135 | spin_lock_irq(&ucounts_lock); |
f6b2db1a EB |
136 | ucounts = find_ucounts(ns, uid, hashent); |
137 | if (!ucounts) { | |
880a3854 | 138 | spin_unlock_irq(&ucounts_lock); |
f6b2db1a EB |
139 | |
140 | new = kzalloc(sizeof(*new), GFP_KERNEL); | |
141 | if (!new) | |
142 | return NULL; | |
143 | ||
144 | new->ns = ns; | |
145 | new->uid = uid; | |
146 | atomic_set(&new->count, 0); | |
147 | ||
880a3854 | 148 | spin_lock_irq(&ucounts_lock); |
f6b2db1a EB |
149 | ucounts = find_ucounts(ns, uid, hashent); |
150 | if (ucounts) { | |
151 | kfree(new); | |
152 | } else { | |
153 | hlist_add_head(&new->node, hashent); | |
154 | ucounts = new; | |
155 | } | |
156 | } | |
157 | if (!atomic_add_unless(&ucounts->count, 1, INT_MAX)) | |
158 | ucounts = NULL; | |
880a3854 | 159 | spin_unlock_irq(&ucounts_lock); |
f6b2db1a EB |
160 | return ucounts; |
161 | } | |
162 | ||
163 | static void put_ucounts(struct ucounts *ucounts) | |
164 | { | |
880a3854 NB |
165 | unsigned long flags; |
166 | ||
f6b2db1a | 167 | if (atomic_dec_and_test(&ucounts->count)) { |
880a3854 | 168 | spin_lock_irqsave(&ucounts_lock, flags); |
f6b2db1a | 169 | hlist_del_init(&ucounts->node); |
880a3854 | 170 | spin_unlock_irqrestore(&ucounts_lock, flags); |
f6b2db1a EB |
171 | |
172 | kfree(ucounts); | |
173 | } | |
174 | } | |
175 | ||
b376c3e1 EB |
176 | static inline bool atomic_inc_below(atomic_t *v, int u) |
177 | { | |
178 | int c, old; | |
179 | c = atomic_read(v); | |
180 | for (;;) { | |
181 | if (unlikely(c >= u)) | |
182 | return false; | |
183 | old = atomic_cmpxchg(v, c, c+1); | |
184 | if (likely(old == c)) | |
185 | return true; | |
186 | c = old; | |
187 | } | |
188 | } | |
189 | ||
25f9c081 EB |
190 | struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid, |
191 | enum ucount_type type) | |
b376c3e1 | 192 | { |
f6b2db1a EB |
193 | struct ucounts *ucounts, *iter, *bad; |
194 | struct user_namespace *tns; | |
195 | ucounts = get_ucounts(ns, uid); | |
196 | for (iter = ucounts; iter; iter = tns->ucounts) { | |
197 | int max; | |
198 | tns = iter->ns; | |
25f9c081 EB |
199 | max = READ_ONCE(tns->ucount_max[type]); |
200 | if (!atomic_inc_below(&iter->ucount[type], max)) | |
b376c3e1 EB |
201 | goto fail; |
202 | } | |
f6b2db1a | 203 | return ucounts; |
b376c3e1 | 204 | fail: |
f6b2db1a EB |
205 | bad = iter; |
206 | for (iter = ucounts; iter != bad; iter = iter->ns->ucounts) | |
25f9c081 | 207 | atomic_dec(&iter->ucount[type]); |
b376c3e1 | 208 | |
f6b2db1a EB |
209 | put_ucounts(ucounts); |
210 | return NULL; | |
b376c3e1 EB |
211 | } |
212 | ||
25f9c081 | 213 | void dec_ucount(struct ucounts *ucounts, enum ucount_type type) |
b376c3e1 | 214 | { |
f6b2db1a EB |
215 | struct ucounts *iter; |
216 | for (iter = ucounts; iter; iter = iter->ns->ucounts) { | |
25f9c081 | 217 | int dec = atomic_dec_if_positive(&iter->ucount[type]); |
b376c3e1 EB |
218 | WARN_ON_ONCE(dec < 0); |
219 | } | |
f6b2db1a | 220 | put_ucounts(ucounts); |
b376c3e1 EB |
221 | } |
222 | ||
dbec2846 EB |
223 | static __init int user_namespace_sysctl_init(void) |
224 | { | |
225 | #ifdef CONFIG_SYSCTL | |
f6b2db1a | 226 | static struct ctl_table_header *user_header; |
dbec2846 EB |
227 | static struct ctl_table empty[1]; |
228 | /* | |
f6b2db1a | 229 | * It is necessary to register the user directory in the |
dbec2846 EB |
230 | * default set so that registrations in the child sets work |
231 | * properly. | |
232 | */ | |
f6b2db1a | 233 | user_header = register_sysctl("user", empty); |
ed5bd7dc | 234 | kmemleak_ignore(user_header); |
f6b2db1a | 235 | BUG_ON(!user_header); |
dbec2846 EB |
236 | BUG_ON(!setup_userns_sysctls(&init_user_ns)); |
237 | #endif | |
238 | return 0; | |
239 | } | |
240 | subsys_initcall(user_namespace_sysctl_init); |