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b886d83c | 1 | // SPDX-License-Identifier: GPL-2.0-only |
dbec2846 EB |
2 | |
3 | #include <linux/stat.h> | |
4 | #include <linux/sysctl.h> | |
5 | #include <linux/slab.h> | |
5b825c3a | 6 | #include <linux/cred.h> |
f6b2db1a | 7 | #include <linux/hash.h> |
514c6032 | 8 | #include <linux/kmemleak.h> |
dbec2846 EB |
9 | #include <linux/user_namespace.h> |
10 | ||
905ae01c AG |
11 | struct ucounts init_ucounts = { |
12 | .ns = &init_user_ns, | |
13 | .uid = GLOBAL_ROOT_UID, | |
b6c33652 | 14 | .count = ATOMIC_INIT(1), |
905ae01c AG |
15 | }; |
16 | ||
f6b2db1a EB |
17 | #define UCOUNTS_HASHTABLE_BITS 10 |
18 | static struct hlist_head ucounts_hashtable[(1 << UCOUNTS_HASHTABLE_BITS)]; | |
19 | static DEFINE_SPINLOCK(ucounts_lock); | |
20 | ||
21 | #define ucounts_hashfn(ns, uid) \ | |
22 | hash_long((unsigned long)__kuid_val(uid) + (unsigned long)(ns), \ | |
23 | UCOUNTS_HASHTABLE_BITS) | |
24 | #define ucounts_hashentry(ns, uid) \ | |
25 | (ucounts_hashtable + ucounts_hashfn(ns, uid)) | |
26 | ||
27 | ||
dbec2846 EB |
28 | #ifdef CONFIG_SYSCTL |
29 | static struct ctl_table_set * | |
30 | set_lookup(struct ctl_table_root *root) | |
31 | { | |
32 | return ¤t_user_ns()->set; | |
33 | } | |
34 | ||
35 | static int set_is_seen(struct ctl_table_set *set) | |
36 | { | |
37 | return ¤t_user_ns()->set == set; | |
38 | } | |
39 | ||
40 | static int set_permissions(struct ctl_table_header *head, | |
41 | struct ctl_table *table) | |
42 | { | |
43 | struct user_namespace *user_ns = | |
44 | container_of(head->set, struct user_namespace, set); | |
45 | int mode; | |
46 | ||
47 | /* Allow users with CAP_SYS_RESOURCE unrestrained access */ | |
48 | if (ns_capable(user_ns, CAP_SYS_RESOURCE)) | |
49 | mode = (table->mode & S_IRWXU) >> 6; | |
50 | else | |
51 | /* Allow all others at most read-only access */ | |
52 | mode = table->mode & S_IROTH; | |
53 | return (mode << 6) | (mode << 3) | mode; | |
54 | } | |
55 | ||
56 | static struct ctl_table_root set_root = { | |
57 | .lookup = set_lookup, | |
58 | .permissions = set_permissions, | |
59 | }; | |
60 | ||
1cce1eea | 61 | #define UCOUNT_ENTRY(name) \ |
25f9c081 EB |
62 | { \ |
63 | .procname = name, \ | |
64 | .maxlen = sizeof(int), \ | |
65 | .mode = 0644, \ | |
66 | .proc_handler = proc_dointvec_minmax, \ | |
eec4844f MC |
67 | .extra1 = SYSCTL_ZERO, \ |
68 | .extra2 = SYSCTL_INT_MAX, \ | |
25f9c081 | 69 | } |
f6b2db1a | 70 | static struct ctl_table user_table[] = { |
25f9c081 | 71 | UCOUNT_ENTRY("max_user_namespaces"), |
f333c700 | 72 | UCOUNT_ENTRY("max_pid_namespaces"), |
f7af3d1c | 73 | UCOUNT_ENTRY("max_uts_namespaces"), |
aba35661 | 74 | UCOUNT_ENTRY("max_ipc_namespaces"), |
70328660 | 75 | UCOUNT_ENTRY("max_net_namespaces"), |
537f7ccb | 76 | UCOUNT_ENTRY("max_mnt_namespaces"), |
d08311dd | 77 | UCOUNT_ENTRY("max_cgroup_namespaces"), |
eeec26d5 | 78 | UCOUNT_ENTRY("max_time_namespaces"), |
1cce1eea NB |
79 | #ifdef CONFIG_INOTIFY_USER |
80 | UCOUNT_ENTRY("max_inotify_instances"), | |
81 | UCOUNT_ENTRY("max_inotify_watches"), | |
5b8fea65 AG |
82 | #endif |
83 | #ifdef CONFIG_FANOTIFY | |
84 | UCOUNT_ENTRY("max_fanotify_groups"), | |
85 | UCOUNT_ENTRY("max_fanotify_marks"), | |
1cce1eea | 86 | #endif |
d6469690 | 87 | { }, |
6e52a9f0 | 88 | { }, |
21d1c5e3 | 89 | { }, |
d7c9e99a | 90 | { }, |
dbec2846 EB |
91 | { } |
92 | }; | |
93 | #endif /* CONFIG_SYSCTL */ | |
94 | ||
95 | bool setup_userns_sysctls(struct user_namespace *ns) | |
96 | { | |
97 | #ifdef CONFIG_SYSCTL | |
98 | struct ctl_table *tbl; | |
0f538e3e JK |
99 | |
100 | BUILD_BUG_ON(ARRAY_SIZE(user_table) != UCOUNT_COUNTS + 1); | |
dbec2846 | 101 | setup_sysctl_set(&ns->set, &set_root, set_is_seen); |
f6b2db1a | 102 | tbl = kmemdup(user_table, sizeof(user_table), GFP_KERNEL); |
dbec2846 | 103 | if (tbl) { |
25f9c081 EB |
104 | int i; |
105 | for (i = 0; i < UCOUNT_COUNTS; i++) { | |
106 | tbl[i].data = &ns->ucount_max[i]; | |
107 | } | |
f6b2db1a | 108 | ns->sysctls = __register_sysctl_table(&ns->set, "user", tbl); |
dbec2846 EB |
109 | } |
110 | if (!ns->sysctls) { | |
111 | kfree(tbl); | |
112 | retire_sysctl_set(&ns->set); | |
113 | return false; | |
114 | } | |
115 | #endif | |
116 | return true; | |
117 | } | |
118 | ||
119 | void retire_userns_sysctls(struct user_namespace *ns) | |
120 | { | |
121 | #ifdef CONFIG_SYSCTL | |
122 | struct ctl_table *tbl; | |
123 | ||
124 | tbl = ns->sysctls->ctl_table_arg; | |
125 | unregister_sysctl_table(ns->sysctls); | |
126 | retire_sysctl_set(&ns->set); | |
127 | kfree(tbl); | |
128 | #endif | |
129 | } | |
130 | ||
f6b2db1a EB |
131 | static struct ucounts *find_ucounts(struct user_namespace *ns, kuid_t uid, struct hlist_head *hashent) |
132 | { | |
133 | struct ucounts *ucounts; | |
134 | ||
135 | hlist_for_each_entry(ucounts, hashent, node) { | |
136 | if (uid_eq(ucounts->uid, uid) && (ucounts->ns == ns)) | |
137 | return ucounts; | |
138 | } | |
139 | return NULL; | |
140 | } | |
141 | ||
905ae01c AG |
142 | static void hlist_add_ucounts(struct ucounts *ucounts) |
143 | { | |
144 | struct hlist_head *hashent = ucounts_hashentry(ucounts->ns, ucounts->uid); | |
145 | spin_lock_irq(&ucounts_lock); | |
146 | hlist_add_head(&ucounts->node, hashent); | |
147 | spin_unlock_irq(&ucounts_lock); | |
148 | } | |
149 | ||
b6c33652 AG |
150 | struct ucounts *get_ucounts(struct ucounts *ucounts) |
151 | { | |
152 | if (ucounts && atomic_add_negative(1, &ucounts->count)) { | |
153 | put_ucounts(ucounts); | |
154 | ucounts = NULL; | |
155 | } | |
156 | return ucounts; | |
157 | } | |
158 | ||
905ae01c | 159 | struct ucounts *alloc_ucounts(struct user_namespace *ns, kuid_t uid) |
f6b2db1a EB |
160 | { |
161 | struct hlist_head *hashent = ucounts_hashentry(ns, uid); | |
162 | struct ucounts *ucounts, *new; | |
163 | ||
880a3854 | 164 | spin_lock_irq(&ucounts_lock); |
f6b2db1a EB |
165 | ucounts = find_ucounts(ns, uid, hashent); |
166 | if (!ucounts) { | |
880a3854 | 167 | spin_unlock_irq(&ucounts_lock); |
f6b2db1a EB |
168 | |
169 | new = kzalloc(sizeof(*new), GFP_KERNEL); | |
170 | if (!new) | |
171 | return NULL; | |
172 | ||
173 | new->ns = ns; | |
174 | new->uid = uid; | |
b6c33652 | 175 | atomic_set(&new->count, 1); |
f6b2db1a | 176 | |
880a3854 | 177 | spin_lock_irq(&ucounts_lock); |
f6b2db1a EB |
178 | ucounts = find_ucounts(ns, uid, hashent); |
179 | if (ucounts) { | |
180 | kfree(new); | |
181 | } else { | |
182 | hlist_add_head(&new->node, hashent); | |
b6c33652 AG |
183 | spin_unlock_irq(&ucounts_lock); |
184 | return new; | |
f6b2db1a EB |
185 | } |
186 | } | |
880a3854 | 187 | spin_unlock_irq(&ucounts_lock); |
b6c33652 | 188 | ucounts = get_ucounts(ucounts); |
f6b2db1a EB |
189 | return ucounts; |
190 | } | |
191 | ||
905ae01c | 192 | void put_ucounts(struct ucounts *ucounts) |
f6b2db1a | 193 | { |
880a3854 NB |
194 | unsigned long flags; |
195 | ||
b6c33652 AG |
196 | if (atomic_dec_and_test(&ucounts->count)) { |
197 | spin_lock_irqsave(&ucounts_lock, flags); | |
f6b2db1a | 198 | hlist_del_init(&ucounts->node); |
b6c33652 AG |
199 | spin_unlock_irqrestore(&ucounts_lock, flags); |
200 | kfree(ucounts); | |
201 | } | |
f6b2db1a EB |
202 | } |
203 | ||
f9c82a4e | 204 | static inline bool atomic_long_inc_below(atomic_long_t *v, int u) |
b376c3e1 | 205 | { |
f9c82a4e AG |
206 | long c, old; |
207 | c = atomic_long_read(v); | |
b376c3e1 EB |
208 | for (;;) { |
209 | if (unlikely(c >= u)) | |
210 | return false; | |
f9c82a4e | 211 | old = atomic_long_cmpxchg(v, c, c+1); |
b376c3e1 EB |
212 | if (likely(old == c)) |
213 | return true; | |
214 | c = old; | |
215 | } | |
216 | } | |
217 | ||
25f9c081 EB |
218 | struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid, |
219 | enum ucount_type type) | |
b376c3e1 | 220 | { |
f6b2db1a EB |
221 | struct ucounts *ucounts, *iter, *bad; |
222 | struct user_namespace *tns; | |
905ae01c | 223 | ucounts = alloc_ucounts(ns, uid); |
f6b2db1a | 224 | for (iter = ucounts; iter; iter = tns->ucounts) { |
f9c82a4e | 225 | long max; |
f6b2db1a | 226 | tns = iter->ns; |
25f9c081 | 227 | max = READ_ONCE(tns->ucount_max[type]); |
f9c82a4e | 228 | if (!atomic_long_inc_below(&iter->ucount[type], max)) |
b376c3e1 EB |
229 | goto fail; |
230 | } | |
f6b2db1a | 231 | return ucounts; |
b376c3e1 | 232 | fail: |
f6b2db1a EB |
233 | bad = iter; |
234 | for (iter = ucounts; iter != bad; iter = iter->ns->ucounts) | |
f9c82a4e | 235 | atomic_long_dec(&iter->ucount[type]); |
b376c3e1 | 236 | |
f6b2db1a EB |
237 | put_ucounts(ucounts); |
238 | return NULL; | |
b376c3e1 EB |
239 | } |
240 | ||
25f9c081 | 241 | void dec_ucount(struct ucounts *ucounts, enum ucount_type type) |
b376c3e1 | 242 | { |
f6b2db1a EB |
243 | struct ucounts *iter; |
244 | for (iter = ucounts; iter; iter = iter->ns->ucounts) { | |
f9c82a4e | 245 | long dec = atomic_long_dec_if_positive(&iter->ucount[type]); |
b376c3e1 EB |
246 | WARN_ON_ONCE(dec < 0); |
247 | } | |
f6b2db1a | 248 | put_ucounts(ucounts); |
b376c3e1 EB |
249 | } |
250 | ||
21d1c5e3 AG |
251 | long inc_rlimit_ucounts(struct ucounts *ucounts, enum ucount_type type, long v) |
252 | { | |
253 | struct ucounts *iter; | |
254 | long ret = 0; | |
255 | ||
256 | for (iter = ucounts; iter; iter = iter->ns->ucounts) { | |
257 | long max = READ_ONCE(iter->ns->ucount_max[type]); | |
258 | long new = atomic_long_add_return(v, &iter->ucount[type]); | |
259 | if (new < 0 || new > max) | |
260 | ret = LONG_MAX; | |
261 | else if (iter == ucounts) | |
262 | ret = new; | |
263 | } | |
264 | return ret; | |
265 | } | |
266 | ||
267 | bool dec_rlimit_ucounts(struct ucounts *ucounts, enum ucount_type type, long v) | |
268 | { | |
269 | struct ucounts *iter; | |
f928ef68 | 270 | long new = -1; /* Silence compiler warning */ |
21d1c5e3 AG |
271 | for (iter = ucounts; iter; iter = iter->ns->ucounts) { |
272 | long dec = atomic_long_add_return(-v, &iter->ucount[type]); | |
273 | WARN_ON_ONCE(dec < 0); | |
274 | if (iter == ucounts) | |
275 | new = dec; | |
276 | } | |
277 | return (new == 0); | |
278 | } | |
279 | ||
280 | bool is_ucounts_overlimit(struct ucounts *ucounts, enum ucount_type type, unsigned long max) | |
281 | { | |
282 | struct ucounts *iter; | |
283 | if (get_ucounts_value(ucounts, type) > max) | |
284 | return true; | |
285 | for (iter = ucounts; iter; iter = iter->ns->ucounts) { | |
286 | max = READ_ONCE(iter->ns->ucount_max[type]); | |
287 | if (get_ucounts_value(iter, type) > max) | |
288 | return true; | |
289 | } | |
290 | return false; | |
291 | } | |
292 | ||
dbec2846 EB |
293 | static __init int user_namespace_sysctl_init(void) |
294 | { | |
295 | #ifdef CONFIG_SYSCTL | |
f6b2db1a | 296 | static struct ctl_table_header *user_header; |
dbec2846 EB |
297 | static struct ctl_table empty[1]; |
298 | /* | |
f6b2db1a | 299 | * It is necessary to register the user directory in the |
dbec2846 EB |
300 | * default set so that registrations in the child sets work |
301 | * properly. | |
302 | */ | |
f6b2db1a | 303 | user_header = register_sysctl("user", empty); |
ed5bd7dc | 304 | kmemleak_ignore(user_header); |
f6b2db1a | 305 | BUG_ON(!user_header); |
dbec2846 EB |
306 | BUG_ON(!setup_userns_sysctls(&init_user_ns)); |
307 | #endif | |
905ae01c | 308 | hlist_add_ucounts(&init_ucounts); |
21d1c5e3 | 309 | inc_rlimit_ucounts(&init_ucounts, UCOUNT_RLIMIT_NPROC, 1); |
dbec2846 EB |
310 | return 0; |
311 | } | |
312 | subsys_initcall(user_namespace_sysctl_init); |