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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 | ||
f6b2db1a EB |
11 | #define UCOUNTS_HASHTABLE_BITS 10 |
12 | static struct hlist_head ucounts_hashtable[(1 << UCOUNTS_HASHTABLE_BITS)]; | |
13 | static 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 | ||
dbec2846 EB |
22 | #ifdef CONFIG_SYSCTL |
23 | static struct ctl_table_set * | |
24 | set_lookup(struct ctl_table_root *root) | |
25 | { | |
26 | return ¤t_user_ns()->set; | |
27 | } | |
28 | ||
29 | static int set_is_seen(struct ctl_table_set *set) | |
30 | { | |
31 | return ¤t_user_ns()->set == set; | |
32 | } | |
33 | ||
34 | static 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 | ||
50 | static struct ctl_table_root set_root = { | |
51 | .lookup = set_lookup, | |
52 | .permissions = set_permissions, | |
53 | }; | |
54 | ||
b376c3e1 EB |
55 | static int zero = 0; |
56 | static int int_max = INT_MAX; | |
1cce1eea | 57 | #define UCOUNT_ENTRY(name) \ |
25f9c081 EB |
58 | { \ |
59 | .procname = name, \ | |
60 | .maxlen = sizeof(int), \ | |
61 | .mode = 0644, \ | |
62 | .proc_handler = proc_dointvec_minmax, \ | |
63 | .extra1 = &zero, \ | |
64 | .extra2 = &int_max, \ | |
65 | } | |
f6b2db1a | 66 | static struct ctl_table user_table[] = { |
25f9c081 | 67 | UCOUNT_ENTRY("max_user_namespaces"), |
f333c700 | 68 | UCOUNT_ENTRY("max_pid_namespaces"), |
f7af3d1c | 69 | UCOUNT_ENTRY("max_uts_namespaces"), |
aba35661 | 70 | UCOUNT_ENTRY("max_ipc_namespaces"), |
70328660 | 71 | UCOUNT_ENTRY("max_net_namespaces"), |
537f7ccb | 72 | UCOUNT_ENTRY("max_mnt_namespaces"), |
d08311dd | 73 | UCOUNT_ENTRY("max_cgroup_namespaces"), |
1cce1eea NB |
74 | #ifdef CONFIG_INOTIFY_USER |
75 | UCOUNT_ENTRY("max_inotify_instances"), | |
76 | UCOUNT_ENTRY("max_inotify_watches"), | |
77 | #endif | |
dbec2846 EB |
78 | { } |
79 | }; | |
80 | #endif /* CONFIG_SYSCTL */ | |
81 | ||
82 | bool setup_userns_sysctls(struct user_namespace *ns) | |
83 | { | |
84 | #ifdef CONFIG_SYSCTL | |
85 | struct ctl_table *tbl; | |
86 | setup_sysctl_set(&ns->set, &set_root, set_is_seen); | |
f6b2db1a | 87 | tbl = kmemdup(user_table, sizeof(user_table), GFP_KERNEL); |
dbec2846 | 88 | if (tbl) { |
25f9c081 EB |
89 | int i; |
90 | for (i = 0; i < UCOUNT_COUNTS; i++) { | |
91 | tbl[i].data = &ns->ucount_max[i]; | |
92 | } | |
f6b2db1a | 93 | ns->sysctls = __register_sysctl_table(&ns->set, "user", tbl); |
dbec2846 EB |
94 | } |
95 | if (!ns->sysctls) { | |
96 | kfree(tbl); | |
97 | retire_sysctl_set(&ns->set); | |
98 | return false; | |
99 | } | |
100 | #endif | |
101 | return true; | |
102 | } | |
103 | ||
104 | void retire_userns_sysctls(struct user_namespace *ns) | |
105 | { | |
106 | #ifdef CONFIG_SYSCTL | |
107 | struct ctl_table *tbl; | |
108 | ||
109 | tbl = ns->sysctls->ctl_table_arg; | |
110 | unregister_sysctl_table(ns->sysctls); | |
111 | retire_sysctl_set(&ns->set); | |
112 | kfree(tbl); | |
113 | #endif | |
114 | } | |
115 | ||
f6b2db1a EB |
116 | static struct ucounts *find_ucounts(struct user_namespace *ns, kuid_t uid, struct hlist_head *hashent) |
117 | { | |
118 | struct ucounts *ucounts; | |
119 | ||
120 | hlist_for_each_entry(ucounts, hashent, node) { | |
121 | if (uid_eq(ucounts->uid, uid) && (ucounts->ns == ns)) | |
122 | return ucounts; | |
123 | } | |
124 | return NULL; | |
125 | } | |
126 | ||
127 | static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid) | |
128 | { | |
129 | struct hlist_head *hashent = ucounts_hashentry(ns, uid); | |
130 | struct ucounts *ucounts, *new; | |
131 | ||
880a3854 | 132 | spin_lock_irq(&ucounts_lock); |
f6b2db1a EB |
133 | ucounts = find_ucounts(ns, uid, hashent); |
134 | if (!ucounts) { | |
880a3854 | 135 | spin_unlock_irq(&ucounts_lock); |
f6b2db1a EB |
136 | |
137 | new = kzalloc(sizeof(*new), GFP_KERNEL); | |
138 | if (!new) | |
139 | return NULL; | |
140 | ||
141 | new->ns = ns; | |
142 | new->uid = uid; | |
040757f7 | 143 | new->count = 0; |
f6b2db1a | 144 | |
880a3854 | 145 | spin_lock_irq(&ucounts_lock); |
f6b2db1a EB |
146 | ucounts = find_ucounts(ns, uid, hashent); |
147 | if (ucounts) { | |
148 | kfree(new); | |
149 | } else { | |
150 | hlist_add_head(&new->node, hashent); | |
151 | ucounts = new; | |
152 | } | |
153 | } | |
040757f7 | 154 | if (ucounts->count == INT_MAX) |
f6b2db1a | 155 | ucounts = NULL; |
040757f7 EB |
156 | else |
157 | ucounts->count += 1; | |
880a3854 | 158 | spin_unlock_irq(&ucounts_lock); |
f6b2db1a EB |
159 | return ucounts; |
160 | } | |
161 | ||
162 | static void put_ucounts(struct ucounts *ucounts) | |
163 | { | |
880a3854 NB |
164 | unsigned long flags; |
165 | ||
040757f7 EB |
166 | spin_lock_irqsave(&ucounts_lock, flags); |
167 | ucounts->count -= 1; | |
168 | if (!ucounts->count) | |
f6b2db1a | 169 | hlist_del_init(&ucounts->node); |
040757f7 EB |
170 | else |
171 | ucounts = NULL; | |
172 | spin_unlock_irqrestore(&ucounts_lock, flags); | |
f6b2db1a | 173 | |
040757f7 | 174 | kfree(ucounts); |
f6b2db1a EB |
175 | } |
176 | ||
b376c3e1 EB |
177 | static inline bool atomic_inc_below(atomic_t *v, int u) |
178 | { | |
179 | int c, old; | |
180 | c = atomic_read(v); | |
181 | for (;;) { | |
182 | if (unlikely(c >= u)) | |
183 | return false; | |
184 | old = atomic_cmpxchg(v, c, c+1); | |
185 | if (likely(old == c)) | |
186 | return true; | |
187 | c = old; | |
188 | } | |
189 | } | |
190 | ||
25f9c081 EB |
191 | struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid, |
192 | enum ucount_type type) | |
b376c3e1 | 193 | { |
f6b2db1a EB |
194 | struct ucounts *ucounts, *iter, *bad; |
195 | struct user_namespace *tns; | |
196 | ucounts = get_ucounts(ns, uid); | |
197 | for (iter = ucounts; iter; iter = tns->ucounts) { | |
198 | int max; | |
199 | tns = iter->ns; | |
25f9c081 EB |
200 | max = READ_ONCE(tns->ucount_max[type]); |
201 | if (!atomic_inc_below(&iter->ucount[type], max)) | |
b376c3e1 EB |
202 | goto fail; |
203 | } | |
f6b2db1a | 204 | return ucounts; |
b376c3e1 | 205 | fail: |
f6b2db1a EB |
206 | bad = iter; |
207 | for (iter = ucounts; iter != bad; iter = iter->ns->ucounts) | |
25f9c081 | 208 | atomic_dec(&iter->ucount[type]); |
b376c3e1 | 209 | |
f6b2db1a EB |
210 | put_ucounts(ucounts); |
211 | return NULL; | |
b376c3e1 EB |
212 | } |
213 | ||
25f9c081 | 214 | void dec_ucount(struct ucounts *ucounts, enum ucount_type type) |
b376c3e1 | 215 | { |
f6b2db1a EB |
216 | struct ucounts *iter; |
217 | for (iter = ucounts; iter; iter = iter->ns->ucounts) { | |
25f9c081 | 218 | int dec = atomic_dec_if_positive(&iter->ucount[type]); |
b376c3e1 EB |
219 | WARN_ON_ONCE(dec < 0); |
220 | } | |
f6b2db1a | 221 | put_ucounts(ucounts); |
b376c3e1 EB |
222 | } |
223 | ||
dbec2846 EB |
224 | static __init int user_namespace_sysctl_init(void) |
225 | { | |
226 | #ifdef CONFIG_SYSCTL | |
f6b2db1a | 227 | static struct ctl_table_header *user_header; |
dbec2846 EB |
228 | static struct ctl_table empty[1]; |
229 | /* | |
f6b2db1a | 230 | * It is necessary to register the user directory in the |
dbec2846 EB |
231 | * default set so that registrations in the child sets work |
232 | * properly. | |
233 | */ | |
f6b2db1a | 234 | user_header = register_sysctl("user", empty); |
ed5bd7dc | 235 | kmemleak_ignore(user_header); |
f6b2db1a | 236 | BUG_ON(!user_header); |
dbec2846 EB |
237 | BUG_ON(!setup_userns_sysctls(&init_user_ns)); |
238 | #endif | |
239 | return 0; | |
240 | } | |
241 | subsys_initcall(user_namespace_sysctl_init); |