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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"), |
dbec2846 EB |
72 | { } |
73 | }; | |
74 | #endif /* CONFIG_SYSCTL */ | |
75 | ||
76 | bool setup_userns_sysctls(struct user_namespace *ns) | |
77 | { | |
78 | #ifdef CONFIG_SYSCTL | |
79 | struct ctl_table *tbl; | |
80 | setup_sysctl_set(&ns->set, &set_root, set_is_seen); | |
f6b2db1a | 81 | tbl = kmemdup(user_table, sizeof(user_table), GFP_KERNEL); |
dbec2846 | 82 | if (tbl) { |
25f9c081 EB |
83 | int i; |
84 | for (i = 0; i < UCOUNT_COUNTS; i++) { | |
85 | tbl[i].data = &ns->ucount_max[i]; | |
86 | } | |
f6b2db1a | 87 | ns->sysctls = __register_sysctl_table(&ns->set, "user", tbl); |
dbec2846 EB |
88 | } |
89 | if (!ns->sysctls) { | |
90 | kfree(tbl); | |
91 | retire_sysctl_set(&ns->set); | |
92 | return false; | |
93 | } | |
94 | #endif | |
95 | return true; | |
96 | } | |
97 | ||
98 | void retire_userns_sysctls(struct user_namespace *ns) | |
99 | { | |
100 | #ifdef CONFIG_SYSCTL | |
101 | struct ctl_table *tbl; | |
102 | ||
103 | tbl = ns->sysctls->ctl_table_arg; | |
104 | unregister_sysctl_table(ns->sysctls); | |
105 | retire_sysctl_set(&ns->set); | |
106 | kfree(tbl); | |
107 | #endif | |
108 | } | |
109 | ||
f6b2db1a EB |
110 | static struct ucounts *find_ucounts(struct user_namespace *ns, kuid_t uid, struct hlist_head *hashent) |
111 | { | |
112 | struct ucounts *ucounts; | |
113 | ||
114 | hlist_for_each_entry(ucounts, hashent, node) { | |
115 | if (uid_eq(ucounts->uid, uid) && (ucounts->ns == ns)) | |
116 | return ucounts; | |
117 | } | |
118 | return NULL; | |
119 | } | |
120 | ||
121 | static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid) | |
122 | { | |
123 | struct hlist_head *hashent = ucounts_hashentry(ns, uid); | |
124 | struct ucounts *ucounts, *new; | |
125 | ||
126 | spin_lock(&ucounts_lock); | |
127 | ucounts = find_ucounts(ns, uid, hashent); | |
128 | if (!ucounts) { | |
129 | spin_unlock(&ucounts_lock); | |
130 | ||
131 | new = kzalloc(sizeof(*new), GFP_KERNEL); | |
132 | if (!new) | |
133 | return NULL; | |
134 | ||
135 | new->ns = ns; | |
136 | new->uid = uid; | |
137 | atomic_set(&new->count, 0); | |
138 | ||
139 | spin_lock(&ucounts_lock); | |
140 | ucounts = find_ucounts(ns, uid, hashent); | |
141 | if (ucounts) { | |
142 | kfree(new); | |
143 | } else { | |
144 | hlist_add_head(&new->node, hashent); | |
145 | ucounts = new; | |
146 | } | |
147 | } | |
148 | if (!atomic_add_unless(&ucounts->count, 1, INT_MAX)) | |
149 | ucounts = NULL; | |
150 | spin_unlock(&ucounts_lock); | |
151 | return ucounts; | |
152 | } | |
153 | ||
154 | static void put_ucounts(struct ucounts *ucounts) | |
155 | { | |
156 | if (atomic_dec_and_test(&ucounts->count)) { | |
157 | spin_lock(&ucounts_lock); | |
158 | hlist_del_init(&ucounts->node); | |
159 | spin_unlock(&ucounts_lock); | |
160 | ||
161 | kfree(ucounts); | |
162 | } | |
163 | } | |
164 | ||
b376c3e1 EB |
165 | static inline bool atomic_inc_below(atomic_t *v, int u) |
166 | { | |
167 | int c, old; | |
168 | c = atomic_read(v); | |
169 | for (;;) { | |
170 | if (unlikely(c >= u)) | |
171 | return false; | |
172 | old = atomic_cmpxchg(v, c, c+1); | |
173 | if (likely(old == c)) | |
174 | return true; | |
175 | c = old; | |
176 | } | |
177 | } | |
178 | ||
25f9c081 EB |
179 | struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid, |
180 | enum ucount_type type) | |
b376c3e1 | 181 | { |
f6b2db1a EB |
182 | struct ucounts *ucounts, *iter, *bad; |
183 | struct user_namespace *tns; | |
184 | ucounts = get_ucounts(ns, uid); | |
185 | for (iter = ucounts; iter; iter = tns->ucounts) { | |
186 | int max; | |
187 | tns = iter->ns; | |
25f9c081 EB |
188 | max = READ_ONCE(tns->ucount_max[type]); |
189 | if (!atomic_inc_below(&iter->ucount[type], max)) | |
b376c3e1 EB |
190 | goto fail; |
191 | } | |
f6b2db1a | 192 | return ucounts; |
b376c3e1 | 193 | fail: |
f6b2db1a EB |
194 | bad = iter; |
195 | for (iter = ucounts; iter != bad; iter = iter->ns->ucounts) | |
25f9c081 | 196 | atomic_dec(&iter->ucount[type]); |
b376c3e1 | 197 | |
f6b2db1a EB |
198 | put_ucounts(ucounts); |
199 | return NULL; | |
b376c3e1 EB |
200 | } |
201 | ||
25f9c081 | 202 | void dec_ucount(struct ucounts *ucounts, enum ucount_type type) |
b376c3e1 | 203 | { |
f6b2db1a EB |
204 | struct ucounts *iter; |
205 | for (iter = ucounts; iter; iter = iter->ns->ucounts) { | |
25f9c081 | 206 | int dec = atomic_dec_if_positive(&iter->ucount[type]); |
b376c3e1 EB |
207 | WARN_ON_ONCE(dec < 0); |
208 | } | |
f6b2db1a | 209 | put_ucounts(ucounts); |
b376c3e1 EB |
210 | } |
211 | ||
dbec2846 EB |
212 | static __init int user_namespace_sysctl_init(void) |
213 | { | |
214 | #ifdef CONFIG_SYSCTL | |
f6b2db1a | 215 | static struct ctl_table_header *user_header; |
dbec2846 EB |
216 | static struct ctl_table empty[1]; |
217 | /* | |
f6b2db1a | 218 | * It is necessary to register the user directory in the |
dbec2846 EB |
219 | * default set so that registrations in the child sets work |
220 | * properly. | |
221 | */ | |
f6b2db1a EB |
222 | user_header = register_sysctl("user", empty); |
223 | BUG_ON(!user_header); | |
dbec2846 EB |
224 | BUG_ON(!setup_userns_sysctls(&init_user_ns)); |
225 | #endif | |
226 | return 0; | |
227 | } | |
228 | subsys_initcall(user_namespace_sysctl_init); | |
229 | ||
230 |