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8#include <linux/stat.h>
9#include <linux/sysctl.h>
10#include <linux/slab.h>
11#include <linux/hash.h>
12#include <linux/user_namespace.h>
13
14#define UCOUNTS_HASHTABLE_BITS 10
15static struct hlist_head ucounts_hashtable[(1 << UCOUNTS_HASHTABLE_BITS)];
16static 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
25#ifdef CONFIG_SYSCTL
26static struct ctl_table_set *
27set_lookup(struct ctl_table_root *root)
28{
29 return ¤t_user_ns()->set;
30}
31
32static int set_is_seen(struct ctl_table_set *set)
33{
34 return ¤t_user_ns()->set == set;
35}
36
37static 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
45 if (ns_capable(user_ns, CAP_SYS_RESOURCE))
46 mode = (table->mode & S_IRWXU) >> 6;
47 else
48
49 mode = table->mode & S_IROTH;
50 return (mode << 6) | (mode << 3) | mode;
51}
52
53static struct ctl_table_root set_root = {
54 .lookup = set_lookup,
55 .permissions = set_permissions,
56};
57
58static int zero = 0;
59static int int_max = INT_MAX;
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 }
69static struct ctl_table user_table[] = {
70 UCOUNT_ENTRY("max_user_namespaces"),
71 UCOUNT_ENTRY("max_pid_namespaces"),
72 UCOUNT_ENTRY("max_uts_namespaces"),
73 UCOUNT_ENTRY("max_ipc_namespaces"),
74 UCOUNT_ENTRY("max_net_namespaces"),
75 UCOUNT_ENTRY("max_mnt_namespaces"),
76 UCOUNT_ENTRY("max_cgroup_namespaces"),
77 { }
78};
79#endif
80
81bool setup_userns_sysctls(struct user_namespace *ns)
82{
83#ifdef CONFIG_SYSCTL
84 struct ctl_table *tbl;
85 setup_sysctl_set(&ns->set, &set_root, set_is_seen);
86 tbl = kmemdup(user_table, sizeof(user_table), GFP_KERNEL);
87 if (tbl) {
88 int i;
89 for (i = 0; i < UCOUNT_COUNTS; i++) {
90 tbl[i].data = &ns->ucount_max[i];
91 }
92 ns->sysctls = __register_sysctl_table(&ns->set, "user", tbl);
93 }
94 if (!ns->sysctls) {
95 kfree(tbl);
96 retire_sysctl_set(&ns->set);
97 return false;
98 }
99#endif
100 return true;
101}
102
103void retire_userns_sysctls(struct user_namespace *ns)
104{
105#ifdef CONFIG_SYSCTL
106 struct ctl_table *tbl;
107
108 tbl = ns->sysctls->ctl_table_arg;
109 unregister_sysctl_table(ns->sysctls);
110 retire_sysctl_set(&ns->set);
111 kfree(tbl);
112#endif
113}
114
115static struct ucounts *find_ucounts(struct user_namespace *ns, kuid_t uid, struct hlist_head *hashent)
116{
117 struct ucounts *ucounts;
118
119 hlist_for_each_entry(ucounts, hashent, node) {
120 if (uid_eq(ucounts->uid, uid) && (ucounts->ns == ns))
121 return ucounts;
122 }
123 return NULL;
124}
125
126static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid)
127{
128 struct hlist_head *hashent = ucounts_hashentry(ns, uid);
129 struct ucounts *ucounts, *new;
130
131 spin_lock(&ucounts_lock);
132 ucounts = find_ucounts(ns, uid, hashent);
133 if (!ucounts) {
134 spin_unlock(&ucounts_lock);
135
136 new = kzalloc(sizeof(*new), GFP_KERNEL);
137 if (!new)
138 return NULL;
139
140 new->ns = ns;
141 new->uid = uid;
142 atomic_set(&new->count, 0);
143
144 spin_lock(&ucounts_lock);
145 ucounts = find_ucounts(ns, uid, hashent);
146 if (ucounts) {
147 kfree(new);
148 } else {
149 hlist_add_head(&new->node, hashent);
150 ucounts = new;
151 }
152 }
153 if (!atomic_add_unless(&ucounts->count, 1, INT_MAX))
154 ucounts = NULL;
155 spin_unlock(&ucounts_lock);
156 return ucounts;
157}
158
159static void put_ucounts(struct ucounts *ucounts)
160{
161 if (atomic_dec_and_test(&ucounts->count)) {
162 spin_lock(&ucounts_lock);
163 hlist_del_init(&ucounts->node);
164 spin_unlock(&ucounts_lock);
165
166 kfree(ucounts);
167 }
168}
169
170static inline bool atomic_inc_below(atomic_t *v, int u)
171{
172 int c, old;
173 c = atomic_read(v);
174 for (;;) {
175 if (unlikely(c >= u))
176 return false;
177 old = atomic_cmpxchg(v, c, c+1);
178 if (likely(old == c))
179 return true;
180 c = old;
181 }
182}
183
184struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid,
185 enum ucount_type type)
186{
187 struct ucounts *ucounts, *iter, *bad;
188 struct user_namespace *tns;
189 ucounts = get_ucounts(ns, uid);
190 for (iter = ucounts; iter; iter = tns->ucounts) {
191 int max;
192 tns = iter->ns;
193 max = READ_ONCE(tns->ucount_max[type]);
194 if (!atomic_inc_below(&iter->ucount[type], max))
195 goto fail;
196 }
197 return ucounts;
198fail:
199 bad = iter;
200 for (iter = ucounts; iter != bad; iter = iter->ns->ucounts)
201 atomic_dec(&iter->ucount[type]);
202
203 put_ucounts(ucounts);
204 return NULL;
205}
206
207void dec_ucount(struct ucounts *ucounts, enum ucount_type type)
208{
209 struct ucounts *iter;
210 for (iter = ucounts; iter; iter = iter->ns->ucounts) {
211 int dec = atomic_dec_if_positive(&iter->ucount[type]);
212 WARN_ON_ONCE(dec < 0);
213 }
214 put_ucounts(ucounts);
215}
216
217static __init int user_namespace_sysctl_init(void)
218{
219#ifdef CONFIG_SYSCTL
220 static struct ctl_table_header *user_header;
221 static struct ctl_table empty[1];
222
223
224
225
226
227 user_header = register_sysctl("user", empty);
228 BUG_ON(!user_header);
229 BUG_ON(!setup_userns_sysctls(&init_user_ns));
230#endif
231 return 0;
232}
233subsys_initcall(user_namespace_sysctl_init);
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