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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 | ||
f153c224 SS |
61 | static long ue_zero = 0; |
62 | static long ue_int_max = INT_MAX; | |
63 | ||
64 | #define UCOUNT_ENTRY(name) \ | |
65 | { \ | |
66 | .procname = name, \ | |
67 | .maxlen = sizeof(long), \ | |
68 | .mode = 0644, \ | |
69 | .proc_handler = proc_doulongvec_minmax, \ | |
70 | .extra1 = &ue_zero, \ | |
71 | .extra2 = &ue_int_max, \ | |
25f9c081 | 72 | } |
f6b2db1a | 73 | static struct ctl_table user_table[] = { |
25f9c081 | 74 | UCOUNT_ENTRY("max_user_namespaces"), |
f333c700 | 75 | UCOUNT_ENTRY("max_pid_namespaces"), |
f7af3d1c | 76 | UCOUNT_ENTRY("max_uts_namespaces"), |
aba35661 | 77 | UCOUNT_ENTRY("max_ipc_namespaces"), |
70328660 | 78 | UCOUNT_ENTRY("max_net_namespaces"), |
537f7ccb | 79 | UCOUNT_ENTRY("max_mnt_namespaces"), |
d08311dd | 80 | UCOUNT_ENTRY("max_cgroup_namespaces"), |
eeec26d5 | 81 | UCOUNT_ENTRY("max_time_namespaces"), |
1cce1eea NB |
82 | #ifdef CONFIG_INOTIFY_USER |
83 | UCOUNT_ENTRY("max_inotify_instances"), | |
84 | UCOUNT_ENTRY("max_inotify_watches"), | |
5b8fea65 AG |
85 | #endif |
86 | #ifdef CONFIG_FANOTIFY | |
87 | UCOUNT_ENTRY("max_fanotify_groups"), | |
88 | UCOUNT_ENTRY("max_fanotify_marks"), | |
1cce1eea | 89 | #endif |
d6469690 | 90 | { }, |
6e52a9f0 | 91 | { }, |
21d1c5e3 | 92 | { }, |
d7c9e99a | 93 | { }, |
dbec2846 EB |
94 | { } |
95 | }; | |
96 | #endif /* CONFIG_SYSCTL */ | |
97 | ||
98 | bool setup_userns_sysctls(struct user_namespace *ns) | |
99 | { | |
100 | #ifdef CONFIG_SYSCTL | |
101 | struct ctl_table *tbl; | |
0f538e3e JK |
102 | |
103 | BUILD_BUG_ON(ARRAY_SIZE(user_table) != UCOUNT_COUNTS + 1); | |
dbec2846 | 104 | setup_sysctl_set(&ns->set, &set_root, set_is_seen); |
f6b2db1a | 105 | tbl = kmemdup(user_table, sizeof(user_table), GFP_KERNEL); |
dbec2846 | 106 | if (tbl) { |
25f9c081 EB |
107 | int i; |
108 | for (i = 0; i < UCOUNT_COUNTS; i++) { | |
109 | tbl[i].data = &ns->ucount_max[i]; | |
110 | } | |
f6b2db1a | 111 | ns->sysctls = __register_sysctl_table(&ns->set, "user", tbl); |
dbec2846 EB |
112 | } |
113 | if (!ns->sysctls) { | |
114 | kfree(tbl); | |
115 | retire_sysctl_set(&ns->set); | |
116 | return false; | |
117 | } | |
118 | #endif | |
119 | return true; | |
120 | } | |
121 | ||
122 | void retire_userns_sysctls(struct user_namespace *ns) | |
123 | { | |
124 | #ifdef CONFIG_SYSCTL | |
125 | struct ctl_table *tbl; | |
126 | ||
127 | tbl = ns->sysctls->ctl_table_arg; | |
128 | unregister_sysctl_table(ns->sysctls); | |
129 | retire_sysctl_set(&ns->set); | |
130 | kfree(tbl); | |
131 | #endif | |
132 | } | |
133 | ||
f6b2db1a EB |
134 | static struct ucounts *find_ucounts(struct user_namespace *ns, kuid_t uid, struct hlist_head *hashent) |
135 | { | |
136 | struct ucounts *ucounts; | |
137 | ||
138 | hlist_for_each_entry(ucounts, hashent, node) { | |
139 | if (uid_eq(ucounts->uid, uid) && (ucounts->ns == ns)) | |
140 | return ucounts; | |
141 | } | |
142 | return NULL; | |
143 | } | |
144 | ||
905ae01c AG |
145 | static void hlist_add_ucounts(struct ucounts *ucounts) |
146 | { | |
147 | struct hlist_head *hashent = ucounts_hashentry(ucounts->ns, ucounts->uid); | |
148 | spin_lock_irq(&ucounts_lock); | |
149 | hlist_add_head(&ucounts->node, hashent); | |
150 | spin_unlock_irq(&ucounts_lock); | |
151 | } | |
152 | ||
b6c33652 AG |
153 | struct ucounts *get_ucounts(struct ucounts *ucounts) |
154 | { | |
155 | if (ucounts && atomic_add_negative(1, &ucounts->count)) { | |
156 | put_ucounts(ucounts); | |
157 | ucounts = NULL; | |
158 | } | |
159 | return ucounts; | |
160 | } | |
161 | ||
905ae01c | 162 | struct ucounts *alloc_ucounts(struct user_namespace *ns, kuid_t uid) |
f6b2db1a EB |
163 | { |
164 | struct hlist_head *hashent = ucounts_hashentry(ns, uid); | |
165 | struct ucounts *ucounts, *new; | |
345daff2 | 166 | long overflow; |
f6b2db1a | 167 | |
880a3854 | 168 | spin_lock_irq(&ucounts_lock); |
f6b2db1a EB |
169 | ucounts = find_ucounts(ns, uid, hashent); |
170 | if (!ucounts) { | |
880a3854 | 171 | spin_unlock_irq(&ucounts_lock); |
f6b2db1a EB |
172 | |
173 | new = kzalloc(sizeof(*new), GFP_KERNEL); | |
174 | if (!new) | |
175 | return NULL; | |
176 | ||
177 | new->ns = ns; | |
178 | new->uid = uid; | |
b6c33652 | 179 | atomic_set(&new->count, 1); |
f6b2db1a | 180 | |
880a3854 | 181 | spin_lock_irq(&ucounts_lock); |
f6b2db1a EB |
182 | ucounts = find_ucounts(ns, uid, hashent); |
183 | if (ucounts) { | |
184 | kfree(new); | |
185 | } else { | |
186 | hlist_add_head(&new->node, hashent); | |
5b9d8d2c | 187 | get_user_ns(new->ns); |
b6c33652 AG |
188 | spin_unlock_irq(&ucounts_lock); |
189 | return new; | |
f6b2db1a EB |
190 | } |
191 | } | |
345daff2 | 192 | overflow = atomic_add_negative(1, &ucounts->count); |
880a3854 | 193 | spin_unlock_irq(&ucounts_lock); |
345daff2 AG |
194 | if (overflow) { |
195 | put_ucounts(ucounts); | |
196 | return NULL; | |
197 | } | |
f6b2db1a EB |
198 | return ucounts; |
199 | } | |
200 | ||
905ae01c | 201 | void put_ucounts(struct ucounts *ucounts) |
f6b2db1a | 202 | { |
880a3854 NB |
203 | unsigned long flags; |
204 | ||
345daff2 | 205 | if (atomic_dec_and_lock_irqsave(&ucounts->count, &ucounts_lock, flags)) { |
f6b2db1a | 206 | hlist_del_init(&ucounts->node); |
b6c33652 | 207 | spin_unlock_irqrestore(&ucounts_lock, flags); |
5b9d8d2c | 208 | put_user_ns(ucounts->ns); |
b6c33652 AG |
209 | kfree(ucounts); |
210 | } | |
f6b2db1a EB |
211 | } |
212 | ||
f9c82a4e | 213 | static inline bool atomic_long_inc_below(atomic_long_t *v, int u) |
b376c3e1 | 214 | { |
f9c82a4e AG |
215 | long c, old; |
216 | c = atomic_long_read(v); | |
b376c3e1 EB |
217 | for (;;) { |
218 | if (unlikely(c >= u)) | |
219 | return false; | |
f9c82a4e | 220 | old = atomic_long_cmpxchg(v, c, c+1); |
b376c3e1 EB |
221 | if (likely(old == c)) |
222 | return true; | |
223 | c = old; | |
224 | } | |
225 | } | |
226 | ||
25f9c081 EB |
227 | struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid, |
228 | enum ucount_type type) | |
b376c3e1 | 229 | { |
f6b2db1a EB |
230 | struct ucounts *ucounts, *iter, *bad; |
231 | struct user_namespace *tns; | |
905ae01c | 232 | ucounts = alloc_ucounts(ns, uid); |
f6b2db1a | 233 | for (iter = ucounts; iter; iter = tns->ucounts) { |
f9c82a4e | 234 | long max; |
f6b2db1a | 235 | tns = iter->ns; |
25f9c081 | 236 | max = READ_ONCE(tns->ucount_max[type]); |
f9c82a4e | 237 | if (!atomic_long_inc_below(&iter->ucount[type], max)) |
b376c3e1 EB |
238 | goto fail; |
239 | } | |
f6b2db1a | 240 | return ucounts; |
b376c3e1 | 241 | fail: |
f6b2db1a EB |
242 | bad = iter; |
243 | for (iter = ucounts; iter != bad; iter = iter->ns->ucounts) | |
f9c82a4e | 244 | atomic_long_dec(&iter->ucount[type]); |
b376c3e1 | 245 | |
f6b2db1a EB |
246 | put_ucounts(ucounts); |
247 | return NULL; | |
b376c3e1 EB |
248 | } |
249 | ||
25f9c081 | 250 | void dec_ucount(struct ucounts *ucounts, enum ucount_type type) |
b376c3e1 | 251 | { |
f6b2db1a EB |
252 | struct ucounts *iter; |
253 | for (iter = ucounts; iter; iter = iter->ns->ucounts) { | |
f9c82a4e | 254 | long dec = atomic_long_dec_if_positive(&iter->ucount[type]); |
b376c3e1 EB |
255 | WARN_ON_ONCE(dec < 0); |
256 | } | |
f6b2db1a | 257 | put_ucounts(ucounts); |
b376c3e1 EB |
258 | } |
259 | ||
21d1c5e3 AG |
260 | long inc_rlimit_ucounts(struct ucounts *ucounts, enum ucount_type type, long v) |
261 | { | |
262 | struct ucounts *iter; | |
a65858ce | 263 | long max = LONG_MAX; |
21d1c5e3 AG |
264 | long ret = 0; |
265 | ||
266 | for (iter = ucounts; iter; iter = iter->ns->ucounts) { | |
21d1c5e3 AG |
267 | long new = atomic_long_add_return(v, &iter->ucount[type]); |
268 | if (new < 0 || new > max) | |
269 | ret = LONG_MAX; | |
270 | else if (iter == ucounts) | |
271 | ret = new; | |
a65858ce | 272 | max = READ_ONCE(iter->ns->ucount_max[type]); |
21d1c5e3 AG |
273 | } |
274 | return ret; | |
275 | } | |
276 | ||
277 | bool dec_rlimit_ucounts(struct ucounts *ucounts, enum ucount_type type, long v) | |
278 | { | |
279 | struct ucounts *iter; | |
f928ef68 | 280 | long new = -1; /* Silence compiler warning */ |
21d1c5e3 AG |
281 | for (iter = ucounts; iter; iter = iter->ns->ucounts) { |
282 | long dec = atomic_long_add_return(-v, &iter->ucount[type]); | |
283 | WARN_ON_ONCE(dec < 0); | |
284 | if (iter == ucounts) | |
285 | new = dec; | |
286 | } | |
287 | return (new == 0); | |
288 | } | |
289 | ||
15bc01ef EB |
290 | static void do_dec_rlimit_put_ucounts(struct ucounts *ucounts, |
291 | struct ucounts *last, enum ucount_type type) | |
292 | { | |
293 | struct ucounts *iter, *next; | |
294 | for (iter = ucounts; iter != last; iter = next) { | |
295 | long dec = atomic_long_add_return(-1, &iter->ucount[type]); | |
296 | WARN_ON_ONCE(dec < 0); | |
297 | next = iter->ns->ucounts; | |
298 | if (dec == 0) | |
299 | put_ucounts(iter); | |
300 | } | |
301 | } | |
302 | ||
303 | void dec_rlimit_put_ucounts(struct ucounts *ucounts, enum ucount_type type) | |
304 | { | |
305 | do_dec_rlimit_put_ucounts(ucounts, NULL, type); | |
306 | } | |
307 | ||
308 | long inc_rlimit_get_ucounts(struct ucounts *ucounts, enum ucount_type type) | |
309 | { | |
310 | /* Caller must hold a reference to ucounts */ | |
311 | struct ucounts *iter; | |
a65858ce | 312 | long max = LONG_MAX; |
15bc01ef EB |
313 | long dec, ret = 0; |
314 | ||
315 | for (iter = ucounts; iter; iter = iter->ns->ucounts) { | |
15bc01ef EB |
316 | long new = atomic_long_add_return(1, &iter->ucount[type]); |
317 | if (new < 0 || new > max) | |
318 | goto unwind; | |
319 | if (iter == ucounts) | |
320 | ret = new; | |
a65858ce | 321 | max = READ_ONCE(iter->ns->ucount_max[type]); |
15bc01ef EB |
322 | /* |
323 | * Grab an extra ucount reference for the caller when | |
324 | * the rlimit count was previously 0. | |
325 | */ | |
326 | if (new != 1) | |
327 | continue; | |
328 | if (!get_ucounts(iter)) | |
329 | goto dec_unwind; | |
330 | } | |
331 | return ret; | |
332 | dec_unwind: | |
333 | dec = atomic_long_add_return(-1, &iter->ucount[type]); | |
334 | WARN_ON_ONCE(dec < 0); | |
335 | unwind: | |
336 | do_dec_rlimit_put_ucounts(ucounts, iter, type); | |
337 | return 0; | |
338 | } | |
339 | ||
a65858ce | 340 | bool is_ucounts_overlimit(struct ucounts *ucounts, enum ucount_type type, unsigned long rlimit) |
21d1c5e3 AG |
341 | { |
342 | struct ucounts *iter; | |
a65858ce AG |
343 | long max = rlimit; |
344 | if (rlimit > LONG_MAX) | |
345 | max = LONG_MAX; | |
21d1c5e3 | 346 | for (iter = ucounts; iter; iter = iter->ns->ucounts) { |
21d1c5e3 AG |
347 | if (get_ucounts_value(iter, type) > max) |
348 | return true; | |
a65858ce | 349 | max = READ_ONCE(iter->ns->ucount_max[type]); |
21d1c5e3 AG |
350 | } |
351 | return false; | |
352 | } | |
353 | ||
dbec2846 EB |
354 | static __init int user_namespace_sysctl_init(void) |
355 | { | |
356 | #ifdef CONFIG_SYSCTL | |
f6b2db1a | 357 | static struct ctl_table_header *user_header; |
dbec2846 EB |
358 | static struct ctl_table empty[1]; |
359 | /* | |
f6b2db1a | 360 | * It is necessary to register the user directory in the |
dbec2846 EB |
361 | * default set so that registrations in the child sets work |
362 | * properly. | |
363 | */ | |
f6b2db1a | 364 | user_header = register_sysctl("user", empty); |
ed5bd7dc | 365 | kmemleak_ignore(user_header); |
f6b2db1a | 366 | BUG_ON(!user_header); |
dbec2846 EB |
367 | BUG_ON(!setup_userns_sysctls(&init_user_ns)); |
368 | #endif | |
905ae01c | 369 | hlist_add_ucounts(&init_ucounts); |
21d1c5e3 | 370 | inc_rlimit_ucounts(&init_ucounts, UCOUNT_RLIMIT_NPROC, 1); |
dbec2846 EB |
371 | return 0; |
372 | } | |
373 | subsys_initcall(user_namespace_sysctl_init); |