Loading...
1// SPDX-License-Identifier: GPL-2.0-only
2
3#include <linux/stat.h>
4#include <linux/sysctl.h>
5#include <linux/slab.h>
6#include <linux/cred.h>
7#include <linux/hash.h>
8#include <linux/kmemleak.h>
9#include <linux/user_namespace.h>
10
11#define UCOUNTS_HASHTABLE_BITS 10
12static struct hlist_head ucounts_hashtable[(1 << UCOUNTS_HASHTABLE_BITS)];
13static DEFINE_SPINLOCK(ucounts_lock);
14
15#define ucounts_hashfn(ns, uid) \
16 hash_long((unsigned long)__kuid_val(uid) + (unsigned long)(ns), \
17 UCOUNTS_HASHTABLE_BITS)
18#define ucounts_hashentry(ns, uid) \
19 (ucounts_hashtable + ucounts_hashfn(ns, uid))
20
21
22#ifdef CONFIG_SYSCTL
23static struct ctl_table_set *
24set_lookup(struct ctl_table_root *root)
25{
26 return ¤t_user_ns()->set;
27}
28
29static int set_is_seen(struct ctl_table_set *set)
30{
31 return ¤t_user_ns()->set == set;
32}
33
34static int set_permissions(struct ctl_table_header *head,
35 struct ctl_table *table)
36{
37 struct user_namespace *user_ns =
38 container_of(head->set, struct user_namespace, set);
39 int mode;
40
41 /* Allow users with CAP_SYS_RESOURCE unrestrained access */
42 if (ns_capable(user_ns, CAP_SYS_RESOURCE))
43 mode = (table->mode & S_IRWXU) >> 6;
44 else
45 /* Allow all others at most read-only access */
46 mode = table->mode & S_IROTH;
47 return (mode << 6) | (mode << 3) | mode;
48}
49
50static struct ctl_table_root set_root = {
51 .lookup = set_lookup,
52 .permissions = set_permissions,
53};
54
55#define UCOUNT_ENTRY(name) \
56 { \
57 .procname = name, \
58 .maxlen = sizeof(int), \
59 .mode = 0644, \
60 .proc_handler = proc_dointvec_minmax, \
61 .extra1 = SYSCTL_ZERO, \
62 .extra2 = SYSCTL_INT_MAX, \
63 }
64static struct ctl_table user_table[] = {
65 UCOUNT_ENTRY("max_user_namespaces"),
66 UCOUNT_ENTRY("max_pid_namespaces"),
67 UCOUNT_ENTRY("max_uts_namespaces"),
68 UCOUNT_ENTRY("max_ipc_namespaces"),
69 UCOUNT_ENTRY("max_net_namespaces"),
70 UCOUNT_ENTRY("max_mnt_namespaces"),
71 UCOUNT_ENTRY("max_cgroup_namespaces"),
72#ifdef CONFIG_INOTIFY_USER
73 UCOUNT_ENTRY("max_inotify_instances"),
74 UCOUNT_ENTRY("max_inotify_watches"),
75#endif
76 { }
77};
78#endif /* CONFIG_SYSCTL */
79
80bool setup_userns_sysctls(struct user_namespace *ns)
81{
82#ifdef CONFIG_SYSCTL
83 struct ctl_table *tbl;
84 setup_sysctl_set(&ns->set, &set_root, set_is_seen);
85 tbl = kmemdup(user_table, sizeof(user_table), GFP_KERNEL);
86 if (tbl) {
87 int i;
88 for (i = 0; i < UCOUNT_COUNTS; i++) {
89 tbl[i].data = &ns->ucount_max[i];
90 }
91 ns->sysctls = __register_sysctl_table(&ns->set, "user", tbl);
92 }
93 if (!ns->sysctls) {
94 kfree(tbl);
95 retire_sysctl_set(&ns->set);
96 return false;
97 }
98#endif
99 return true;
100}
101
102void retire_userns_sysctls(struct user_namespace *ns)
103{
104#ifdef CONFIG_SYSCTL
105 struct ctl_table *tbl;
106
107 tbl = ns->sysctls->ctl_table_arg;
108 unregister_sysctl_table(ns->sysctls);
109 retire_sysctl_set(&ns->set);
110 kfree(tbl);
111#endif
112}
113
114static struct ucounts *find_ucounts(struct user_namespace *ns, kuid_t uid, struct hlist_head *hashent)
115{
116 struct ucounts *ucounts;
117
118 hlist_for_each_entry(ucounts, hashent, node) {
119 if (uid_eq(ucounts->uid, uid) && (ucounts->ns == ns))
120 return ucounts;
121 }
122 return NULL;
123}
124
125static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid)
126{
127 struct hlist_head *hashent = ucounts_hashentry(ns, uid);
128 struct ucounts *ucounts, *new;
129
130 spin_lock_irq(&ucounts_lock);
131 ucounts = find_ucounts(ns, uid, hashent);
132 if (!ucounts) {
133 spin_unlock_irq(&ucounts_lock);
134
135 new = kzalloc(sizeof(*new), GFP_KERNEL);
136 if (!new)
137 return NULL;
138
139 new->ns = ns;
140 new->uid = uid;
141 new->count = 0;
142
143 spin_lock_irq(&ucounts_lock);
144 ucounts = find_ucounts(ns, uid, hashent);
145 if (ucounts) {
146 kfree(new);
147 } else {
148 hlist_add_head(&new->node, hashent);
149 ucounts = new;
150 }
151 }
152 if (ucounts->count == INT_MAX)
153 ucounts = NULL;
154 else
155 ucounts->count += 1;
156 spin_unlock_irq(&ucounts_lock);
157 return ucounts;
158}
159
160static void put_ucounts(struct ucounts *ucounts)
161{
162 unsigned long flags;
163
164 spin_lock_irqsave(&ucounts_lock, flags);
165 ucounts->count -= 1;
166 if (!ucounts->count)
167 hlist_del_init(&ucounts->node);
168 else
169 ucounts = NULL;
170 spin_unlock_irqrestore(&ucounts_lock, flags);
171
172 kfree(ucounts);
173}
174
175static inline bool atomic_inc_below(atomic_t *v, int u)
176{
177 int c, old;
178 c = atomic_read(v);
179 for (;;) {
180 if (unlikely(c >= u))
181 return false;
182 old = atomic_cmpxchg(v, c, c+1);
183 if (likely(old == c))
184 return true;
185 c = old;
186 }
187}
188
189struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid,
190 enum ucount_type type)
191{
192 struct ucounts *ucounts, *iter, *bad;
193 struct user_namespace *tns;
194 ucounts = get_ucounts(ns, uid);
195 for (iter = ucounts; iter; iter = tns->ucounts) {
196 int max;
197 tns = iter->ns;
198 max = READ_ONCE(tns->ucount_max[type]);
199 if (!atomic_inc_below(&iter->ucount[type], max))
200 goto fail;
201 }
202 return ucounts;
203fail:
204 bad = iter;
205 for (iter = ucounts; iter != bad; iter = iter->ns->ucounts)
206 atomic_dec(&iter->ucount[type]);
207
208 put_ucounts(ucounts);
209 return NULL;
210}
211
212void dec_ucount(struct ucounts *ucounts, enum ucount_type type)
213{
214 struct ucounts *iter;
215 for (iter = ucounts; iter; iter = iter->ns->ucounts) {
216 int dec = atomic_dec_if_positive(&iter->ucount[type]);
217 WARN_ON_ONCE(dec < 0);
218 }
219 put_ucounts(ucounts);
220}
221
222static __init int user_namespace_sysctl_init(void)
223{
224#ifdef CONFIG_SYSCTL
225 static struct ctl_table_header *user_header;
226 static struct ctl_table empty[1];
227 /*
228 * It is necessary to register the user directory in the
229 * default set so that registrations in the child sets work
230 * properly.
231 */
232 user_header = register_sysctl("user", empty);
233 kmemleak_ignore(user_header);
234 BUG_ON(!user_header);
235 BUG_ON(!setup_userns_sysctls(&init_user_ns));
236#endif
237 return 0;
238}
239subsys_initcall(user_namespace_sysctl_init);
1// SPDX-License-Identifier: GPL-2.0-only
2
3#include <linux/stat.h>
4#include <linux/sysctl.h>
5#include <linux/slab.h>
6#include <linux/cred.h>
7#include <linux/hash.h>
8#include <linux/kmemleak.h>
9#include <linux/user_namespace.h>
10
11struct ucounts init_ucounts = {
12 .ns = &init_user_ns,
13 .uid = GLOBAL_ROOT_UID,
14 .count = ATOMIC_INIT(1),
15};
16
17#define UCOUNTS_HASHTABLE_BITS 10
18static struct hlist_head ucounts_hashtable[(1 << UCOUNTS_HASHTABLE_BITS)];
19static 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
28#ifdef CONFIG_SYSCTL
29static struct ctl_table_set *
30set_lookup(struct ctl_table_root *root)
31{
32 return ¤t_user_ns()->set;
33}
34
35static int set_is_seen(struct ctl_table_set *set)
36{
37 return ¤t_user_ns()->set == set;
38}
39
40static 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
56static struct ctl_table_root set_root = {
57 .lookup = set_lookup,
58 .permissions = set_permissions,
59};
60
61static long ue_zero = 0;
62static 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, \
72 }
73static struct ctl_table user_table[] = {
74 UCOUNT_ENTRY("max_user_namespaces"),
75 UCOUNT_ENTRY("max_pid_namespaces"),
76 UCOUNT_ENTRY("max_uts_namespaces"),
77 UCOUNT_ENTRY("max_ipc_namespaces"),
78 UCOUNT_ENTRY("max_net_namespaces"),
79 UCOUNT_ENTRY("max_mnt_namespaces"),
80 UCOUNT_ENTRY("max_cgroup_namespaces"),
81 UCOUNT_ENTRY("max_time_namespaces"),
82#ifdef CONFIG_INOTIFY_USER
83 UCOUNT_ENTRY("max_inotify_instances"),
84 UCOUNT_ENTRY("max_inotify_watches"),
85#endif
86#ifdef CONFIG_FANOTIFY
87 UCOUNT_ENTRY("max_fanotify_groups"),
88 UCOUNT_ENTRY("max_fanotify_marks"),
89#endif
90 { }
91};
92#endif /* CONFIG_SYSCTL */
93
94bool setup_userns_sysctls(struct user_namespace *ns)
95{
96#ifdef CONFIG_SYSCTL
97 struct ctl_table *tbl;
98
99 BUILD_BUG_ON(ARRAY_SIZE(user_table) != UCOUNT_COUNTS + 1);
100 setup_sysctl_set(&ns->set, &set_root, set_is_seen);
101 tbl = kmemdup(user_table, sizeof(user_table), GFP_KERNEL);
102 if (tbl) {
103 int i;
104 for (i = 0; i < UCOUNT_COUNTS; i++) {
105 tbl[i].data = &ns->ucount_max[i];
106 }
107 ns->sysctls = __register_sysctl_table(&ns->set, "user", tbl,
108 ARRAY_SIZE(user_table));
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
119void 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
131static 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
142static 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
150static inline bool get_ucounts_or_wrap(struct ucounts *ucounts)
151{
152 /* Returns true on a successful get, false if the count wraps. */
153 return !atomic_add_negative(1, &ucounts->count);
154}
155
156struct ucounts *get_ucounts(struct ucounts *ucounts)
157{
158 if (!get_ucounts_or_wrap(ucounts)) {
159 put_ucounts(ucounts);
160 ucounts = NULL;
161 }
162 return ucounts;
163}
164
165struct ucounts *alloc_ucounts(struct user_namespace *ns, kuid_t uid)
166{
167 struct hlist_head *hashent = ucounts_hashentry(ns, uid);
168 struct ucounts *ucounts, *new;
169 bool wrapped;
170
171 spin_lock_irq(&ucounts_lock);
172 ucounts = find_ucounts(ns, uid, hashent);
173 if (!ucounts) {
174 spin_unlock_irq(&ucounts_lock);
175
176 new = kzalloc(sizeof(*new), GFP_KERNEL);
177 if (!new)
178 return NULL;
179
180 new->ns = ns;
181 new->uid = uid;
182 atomic_set(&new->count, 1);
183
184 spin_lock_irq(&ucounts_lock);
185 ucounts = find_ucounts(ns, uid, hashent);
186 if (ucounts) {
187 kfree(new);
188 } else {
189 hlist_add_head(&new->node, hashent);
190 get_user_ns(new->ns);
191 spin_unlock_irq(&ucounts_lock);
192 return new;
193 }
194 }
195 wrapped = !get_ucounts_or_wrap(ucounts);
196 spin_unlock_irq(&ucounts_lock);
197 if (wrapped) {
198 put_ucounts(ucounts);
199 return NULL;
200 }
201 return ucounts;
202}
203
204void put_ucounts(struct ucounts *ucounts)
205{
206 unsigned long flags;
207
208 if (atomic_dec_and_lock_irqsave(&ucounts->count, &ucounts_lock, flags)) {
209 hlist_del_init(&ucounts->node);
210 spin_unlock_irqrestore(&ucounts_lock, flags);
211 put_user_ns(ucounts->ns);
212 kfree(ucounts);
213 }
214}
215
216static inline bool atomic_long_inc_below(atomic_long_t *v, int u)
217{
218 long c, old;
219 c = atomic_long_read(v);
220 for (;;) {
221 if (unlikely(c >= u))
222 return false;
223 old = atomic_long_cmpxchg(v, c, c+1);
224 if (likely(old == c))
225 return true;
226 c = old;
227 }
228}
229
230struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid,
231 enum ucount_type type)
232{
233 struct ucounts *ucounts, *iter, *bad;
234 struct user_namespace *tns;
235 ucounts = alloc_ucounts(ns, uid);
236 for (iter = ucounts; iter; iter = tns->ucounts) {
237 long max;
238 tns = iter->ns;
239 max = READ_ONCE(tns->ucount_max[type]);
240 if (!atomic_long_inc_below(&iter->ucount[type], max))
241 goto fail;
242 }
243 return ucounts;
244fail:
245 bad = iter;
246 for (iter = ucounts; iter != bad; iter = iter->ns->ucounts)
247 atomic_long_dec(&iter->ucount[type]);
248
249 put_ucounts(ucounts);
250 return NULL;
251}
252
253void dec_ucount(struct ucounts *ucounts, enum ucount_type type)
254{
255 struct ucounts *iter;
256 for (iter = ucounts; iter; iter = iter->ns->ucounts) {
257 long dec = atomic_long_dec_if_positive(&iter->ucount[type]);
258 WARN_ON_ONCE(dec < 0);
259 }
260 put_ucounts(ucounts);
261}
262
263long inc_rlimit_ucounts(struct ucounts *ucounts, enum rlimit_type type, long v)
264{
265 struct ucounts *iter;
266 long max = LONG_MAX;
267 long ret = 0;
268
269 for (iter = ucounts; iter; iter = iter->ns->ucounts) {
270 long new = atomic_long_add_return(v, &iter->rlimit[type]);
271 if (new < 0 || new > max)
272 ret = LONG_MAX;
273 else if (iter == ucounts)
274 ret = new;
275 max = get_userns_rlimit_max(iter->ns, type);
276 }
277 return ret;
278}
279
280bool dec_rlimit_ucounts(struct ucounts *ucounts, enum rlimit_type type, long v)
281{
282 struct ucounts *iter;
283 long new = -1; /* Silence compiler warning */
284 for (iter = ucounts; iter; iter = iter->ns->ucounts) {
285 long dec = atomic_long_sub_return(v, &iter->rlimit[type]);
286 WARN_ON_ONCE(dec < 0);
287 if (iter == ucounts)
288 new = dec;
289 }
290 return (new == 0);
291}
292
293static void do_dec_rlimit_put_ucounts(struct ucounts *ucounts,
294 struct ucounts *last, enum rlimit_type type)
295{
296 struct ucounts *iter, *next;
297 for (iter = ucounts; iter != last; iter = next) {
298 long dec = atomic_long_sub_return(1, &iter->rlimit[type]);
299 WARN_ON_ONCE(dec < 0);
300 next = iter->ns->ucounts;
301 if (dec == 0)
302 put_ucounts(iter);
303 }
304}
305
306void dec_rlimit_put_ucounts(struct ucounts *ucounts, enum rlimit_type type)
307{
308 do_dec_rlimit_put_ucounts(ucounts, NULL, type);
309}
310
311long inc_rlimit_get_ucounts(struct ucounts *ucounts, enum rlimit_type type)
312{
313 /* Caller must hold a reference to ucounts */
314 struct ucounts *iter;
315 long max = LONG_MAX;
316 long dec, ret = 0;
317
318 for (iter = ucounts; iter; iter = iter->ns->ucounts) {
319 long new = atomic_long_add_return(1, &iter->rlimit[type]);
320 if (new < 0 || new > max)
321 goto unwind;
322 if (iter == ucounts)
323 ret = new;
324 max = get_userns_rlimit_max(iter->ns, type);
325 /*
326 * Grab an extra ucount reference for the caller when
327 * the rlimit count was previously 0.
328 */
329 if (new != 1)
330 continue;
331 if (!get_ucounts(iter))
332 goto dec_unwind;
333 }
334 return ret;
335dec_unwind:
336 dec = atomic_long_sub_return(1, &iter->rlimit[type]);
337 WARN_ON_ONCE(dec < 0);
338unwind:
339 do_dec_rlimit_put_ucounts(ucounts, iter, type);
340 return 0;
341}
342
343bool is_rlimit_overlimit(struct ucounts *ucounts, enum rlimit_type type, unsigned long rlimit)
344{
345 struct ucounts *iter;
346 long max = rlimit;
347 if (rlimit > LONG_MAX)
348 max = LONG_MAX;
349 for (iter = ucounts; iter; iter = iter->ns->ucounts) {
350 long val = get_rlimit_value(iter, type);
351 if (val < 0 || val > max)
352 return true;
353 max = get_userns_rlimit_max(iter->ns, type);
354 }
355 return false;
356}
357
358static __init int user_namespace_sysctl_init(void)
359{
360#ifdef CONFIG_SYSCTL
361 static struct ctl_table_header *user_header;
362 static struct ctl_table empty[1];
363 /*
364 * It is necessary to register the user directory in the
365 * default set so that registrations in the child sets work
366 * properly.
367 */
368 user_header = register_sysctl_sz("user", empty, 0);
369 kmemleak_ignore(user_header);
370 BUG_ON(!user_header);
371 BUG_ON(!setup_userns_sysctls(&init_user_ns));
372#endif
373 hlist_add_ucounts(&init_ucounts);
374 inc_rlimit_ucounts(&init_ucounts, UCOUNT_RLIMIT_NPROC, 1);
375 return 0;
376}
377subsys_initcall(user_namespace_sysctl_init);