Eric W. Biederman | dbec284 | 2016-07-30 13:58:49 -0500 | [diff] [blame] | 1 | /* |
| 2 | * This program is free software; you can redistribute it and/or |
| 3 | * modify it under the terms of the GNU General Public License as |
| 4 | * published by the Free Software Foundation, version 2 of the |
| 5 | * License. |
| 6 | */ |
| 7 | |
| 8 | #include <linux/stat.h> |
| 9 | #include <linux/sysctl.h> |
| 10 | #include <linux/slab.h> |
Eric W. Biederman | f6b2db1 | 2016-08-08 13:54:50 -0500 | [diff] [blame^] | 11 | #include <linux/hash.h> |
Eric W. Biederman | dbec284 | 2016-07-30 13:58:49 -0500 | [diff] [blame] | 12 | #include <linux/user_namespace.h> |
| 13 | |
Eric W. Biederman | f6b2db1 | 2016-08-08 13:54:50 -0500 | [diff] [blame^] | 14 | #define UCOUNTS_HASHTABLE_BITS 10 |
| 15 | static struct hlist_head ucounts_hashtable[(1 << UCOUNTS_HASHTABLE_BITS)]; |
| 16 | static 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 | |
Eric W. Biederman | dbec284 | 2016-07-30 13:58:49 -0500 | [diff] [blame] | 25 | #ifdef CONFIG_SYSCTL |
| 26 | static struct ctl_table_set * |
| 27 | set_lookup(struct ctl_table_root *root) |
| 28 | { |
| 29 | return ¤t_user_ns()->set; |
| 30 | } |
| 31 | |
| 32 | static int set_is_seen(struct ctl_table_set *set) |
| 33 | { |
| 34 | return ¤t_user_ns()->set == set; |
| 35 | } |
| 36 | |
| 37 | static 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 | /* Allow users with CAP_SYS_RESOURCE unrestrained access */ |
| 45 | if (ns_capable(user_ns, CAP_SYS_RESOURCE)) |
| 46 | mode = (table->mode & S_IRWXU) >> 6; |
| 47 | else |
| 48 | /* Allow all others at most read-only access */ |
| 49 | mode = table->mode & S_IROTH; |
| 50 | return (mode << 6) | (mode << 3) | mode; |
| 51 | } |
| 52 | |
| 53 | static struct ctl_table_root set_root = { |
| 54 | .lookup = set_lookup, |
| 55 | .permissions = set_permissions, |
| 56 | }; |
| 57 | |
Eric W. Biederman | b376c3e | 2016-08-08 13:41:24 -0500 | [diff] [blame] | 58 | static int zero = 0; |
| 59 | static int int_max = INT_MAX; |
Eric W. Biederman | f6b2db1 | 2016-08-08 13:54:50 -0500 | [diff] [blame^] | 60 | static struct ctl_table user_table[] = { |
Eric W. Biederman | b376c3e | 2016-08-08 13:41:24 -0500 | [diff] [blame] | 61 | { |
| 62 | .procname = "max_user_namespaces", |
| 63 | .data = &init_user_ns.max_user_namespaces, |
| 64 | .maxlen = sizeof(init_user_ns.max_user_namespaces), |
| 65 | .mode = 0644, |
| 66 | .proc_handler = proc_dointvec_minmax, |
| 67 | .extra1 = &zero, |
| 68 | .extra2 = &int_max, |
| 69 | }, |
Eric W. Biederman | dbec284 | 2016-07-30 13:58:49 -0500 | [diff] [blame] | 70 | { } |
| 71 | }; |
| 72 | #endif /* CONFIG_SYSCTL */ |
| 73 | |
| 74 | bool setup_userns_sysctls(struct user_namespace *ns) |
| 75 | { |
| 76 | #ifdef CONFIG_SYSCTL |
| 77 | struct ctl_table *tbl; |
| 78 | setup_sysctl_set(&ns->set, &set_root, set_is_seen); |
Eric W. Biederman | f6b2db1 | 2016-08-08 13:54:50 -0500 | [diff] [blame^] | 79 | tbl = kmemdup(user_table, sizeof(user_table), GFP_KERNEL); |
Eric W. Biederman | dbec284 | 2016-07-30 13:58:49 -0500 | [diff] [blame] | 80 | if (tbl) { |
Eric W. Biederman | b376c3e | 2016-08-08 13:41:24 -0500 | [diff] [blame] | 81 | tbl[0].data = &ns->max_user_namespaces; |
| 82 | |
Eric W. Biederman | f6b2db1 | 2016-08-08 13:54:50 -0500 | [diff] [blame^] | 83 | ns->sysctls = __register_sysctl_table(&ns->set, "user", tbl); |
Eric W. Biederman | dbec284 | 2016-07-30 13:58:49 -0500 | [diff] [blame] | 84 | } |
| 85 | if (!ns->sysctls) { |
| 86 | kfree(tbl); |
| 87 | retire_sysctl_set(&ns->set); |
| 88 | return false; |
| 89 | } |
| 90 | #endif |
| 91 | return true; |
| 92 | } |
| 93 | |
| 94 | void retire_userns_sysctls(struct user_namespace *ns) |
| 95 | { |
| 96 | #ifdef CONFIG_SYSCTL |
| 97 | struct ctl_table *tbl; |
| 98 | |
| 99 | tbl = ns->sysctls->ctl_table_arg; |
| 100 | unregister_sysctl_table(ns->sysctls); |
| 101 | retire_sysctl_set(&ns->set); |
| 102 | kfree(tbl); |
| 103 | #endif |
| 104 | } |
| 105 | |
Eric W. Biederman | f6b2db1 | 2016-08-08 13:54:50 -0500 | [diff] [blame^] | 106 | static struct ucounts *find_ucounts(struct user_namespace *ns, kuid_t uid, struct hlist_head *hashent) |
| 107 | { |
| 108 | struct ucounts *ucounts; |
| 109 | |
| 110 | hlist_for_each_entry(ucounts, hashent, node) { |
| 111 | if (uid_eq(ucounts->uid, uid) && (ucounts->ns == ns)) |
| 112 | return ucounts; |
| 113 | } |
| 114 | return NULL; |
| 115 | } |
| 116 | |
| 117 | static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid) |
| 118 | { |
| 119 | struct hlist_head *hashent = ucounts_hashentry(ns, uid); |
| 120 | struct ucounts *ucounts, *new; |
| 121 | |
| 122 | spin_lock(&ucounts_lock); |
| 123 | ucounts = find_ucounts(ns, uid, hashent); |
| 124 | if (!ucounts) { |
| 125 | spin_unlock(&ucounts_lock); |
| 126 | |
| 127 | new = kzalloc(sizeof(*new), GFP_KERNEL); |
| 128 | if (!new) |
| 129 | return NULL; |
| 130 | |
| 131 | new->ns = ns; |
| 132 | new->uid = uid; |
| 133 | atomic_set(&new->count, 0); |
| 134 | |
| 135 | spin_lock(&ucounts_lock); |
| 136 | ucounts = find_ucounts(ns, uid, hashent); |
| 137 | if (ucounts) { |
| 138 | kfree(new); |
| 139 | } else { |
| 140 | hlist_add_head(&new->node, hashent); |
| 141 | ucounts = new; |
| 142 | } |
| 143 | } |
| 144 | if (!atomic_add_unless(&ucounts->count, 1, INT_MAX)) |
| 145 | ucounts = NULL; |
| 146 | spin_unlock(&ucounts_lock); |
| 147 | return ucounts; |
| 148 | } |
| 149 | |
| 150 | static void put_ucounts(struct ucounts *ucounts) |
| 151 | { |
| 152 | if (atomic_dec_and_test(&ucounts->count)) { |
| 153 | spin_lock(&ucounts_lock); |
| 154 | hlist_del_init(&ucounts->node); |
| 155 | spin_unlock(&ucounts_lock); |
| 156 | |
| 157 | kfree(ucounts); |
| 158 | } |
| 159 | } |
| 160 | |
Eric W. Biederman | b376c3e | 2016-08-08 13:41:24 -0500 | [diff] [blame] | 161 | static inline bool atomic_inc_below(atomic_t *v, int u) |
| 162 | { |
| 163 | int c, old; |
| 164 | c = atomic_read(v); |
| 165 | for (;;) { |
| 166 | if (unlikely(c >= u)) |
| 167 | return false; |
| 168 | old = atomic_cmpxchg(v, c, c+1); |
| 169 | if (likely(old == c)) |
| 170 | return true; |
| 171 | c = old; |
| 172 | } |
| 173 | } |
| 174 | |
Eric W. Biederman | f6b2db1 | 2016-08-08 13:54:50 -0500 | [diff] [blame^] | 175 | struct ucounts *inc_user_namespaces(struct user_namespace *ns, kuid_t uid) |
Eric W. Biederman | b376c3e | 2016-08-08 13:41:24 -0500 | [diff] [blame] | 176 | { |
Eric W. Biederman | f6b2db1 | 2016-08-08 13:54:50 -0500 | [diff] [blame^] | 177 | struct ucounts *ucounts, *iter, *bad; |
| 178 | struct user_namespace *tns; |
| 179 | ucounts = get_ucounts(ns, uid); |
| 180 | for (iter = ucounts; iter; iter = tns->ucounts) { |
| 181 | int max; |
| 182 | tns = iter->ns; |
| 183 | max = READ_ONCE(tns->max_user_namespaces); |
| 184 | if (!atomic_inc_below(&iter->user_namespaces, max)) |
Eric W. Biederman | b376c3e | 2016-08-08 13:41:24 -0500 | [diff] [blame] | 185 | goto fail; |
| 186 | } |
Eric W. Biederman | f6b2db1 | 2016-08-08 13:54:50 -0500 | [diff] [blame^] | 187 | return ucounts; |
Eric W. Biederman | b376c3e | 2016-08-08 13:41:24 -0500 | [diff] [blame] | 188 | fail: |
Eric W. Biederman | f6b2db1 | 2016-08-08 13:54:50 -0500 | [diff] [blame^] | 189 | bad = iter; |
| 190 | for (iter = ucounts; iter != bad; iter = iter->ns->ucounts) |
| 191 | atomic_dec(&iter->user_namespaces); |
Eric W. Biederman | b376c3e | 2016-08-08 13:41:24 -0500 | [diff] [blame] | 192 | |
Eric W. Biederman | f6b2db1 | 2016-08-08 13:54:50 -0500 | [diff] [blame^] | 193 | put_ucounts(ucounts); |
| 194 | return NULL; |
Eric W. Biederman | b376c3e | 2016-08-08 13:41:24 -0500 | [diff] [blame] | 195 | } |
| 196 | |
Eric W. Biederman | f6b2db1 | 2016-08-08 13:54:50 -0500 | [diff] [blame^] | 197 | void dec_user_namespaces(struct ucounts *ucounts) |
Eric W. Biederman | b376c3e | 2016-08-08 13:41:24 -0500 | [diff] [blame] | 198 | { |
Eric W. Biederman | f6b2db1 | 2016-08-08 13:54:50 -0500 | [diff] [blame^] | 199 | struct ucounts *iter; |
| 200 | for (iter = ucounts; iter; iter = iter->ns->ucounts) { |
| 201 | int dec = atomic_dec_if_positive(&iter->user_namespaces); |
Eric W. Biederman | b376c3e | 2016-08-08 13:41:24 -0500 | [diff] [blame] | 202 | WARN_ON_ONCE(dec < 0); |
| 203 | } |
Eric W. Biederman | f6b2db1 | 2016-08-08 13:54:50 -0500 | [diff] [blame^] | 204 | put_ucounts(ucounts); |
Eric W. Biederman | b376c3e | 2016-08-08 13:41:24 -0500 | [diff] [blame] | 205 | } |
| 206 | |
Eric W. Biederman | f6b2db1 | 2016-08-08 13:54:50 -0500 | [diff] [blame^] | 207 | |
Eric W. Biederman | dbec284 | 2016-07-30 13:58:49 -0500 | [diff] [blame] | 208 | static __init int user_namespace_sysctl_init(void) |
| 209 | { |
| 210 | #ifdef CONFIG_SYSCTL |
Eric W. Biederman | f6b2db1 | 2016-08-08 13:54:50 -0500 | [diff] [blame^] | 211 | static struct ctl_table_header *user_header; |
Eric W. Biederman | dbec284 | 2016-07-30 13:58:49 -0500 | [diff] [blame] | 212 | static struct ctl_table empty[1]; |
| 213 | /* |
Eric W. Biederman | f6b2db1 | 2016-08-08 13:54:50 -0500 | [diff] [blame^] | 214 | * It is necessary to register the user directory in the |
Eric W. Biederman | dbec284 | 2016-07-30 13:58:49 -0500 | [diff] [blame] | 215 | * default set so that registrations in the child sets work |
| 216 | * properly. |
| 217 | */ |
Eric W. Biederman | f6b2db1 | 2016-08-08 13:54:50 -0500 | [diff] [blame^] | 218 | user_header = register_sysctl("user", empty); |
| 219 | BUG_ON(!user_header); |
Eric W. Biederman | dbec284 | 2016-07-30 13:58:49 -0500 | [diff] [blame] | 220 | BUG_ON(!setup_userns_sysctls(&init_user_ns)); |
| 221 | #endif |
| 222 | return 0; |
| 223 | } |
| 224 | subsys_initcall(user_namespace_sysctl_init); |
| 225 | |
| 226 | |