| 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 | struct 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 |
| 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 | |
| 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 | const 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 | |
| 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, \ |
| 72 | } |
| 73 | static 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 | #endif /* CONFIG_SYSCTL */ |
| 92 | |
| 93 | bool setup_userns_sysctls(struct user_namespace *ns) |
| 94 | { |
| 95 | #ifdef CONFIG_SYSCTL |
| 96 | struct ctl_table *tbl; |
| 97 | |
| 98 | BUILD_BUG_ON(ARRAY_SIZE(user_table) != UCOUNT_COUNTS); |
| 99 | setup_sysctl_set(&ns->set, &set_root, set_is_seen); |
| 100 | tbl = kmemdup(user_table, sizeof(user_table), GFP_KERNEL); |
| 101 | if (tbl) { |
| 102 | int i; |
| 103 | for (i = 0; i < UCOUNT_COUNTS; i++) { |
| 104 | tbl[i].data = &ns->ucount_max[i]; |
| 105 | } |
| 106 | ns->sysctls = __register_sysctl_table(&ns->set, "user", tbl, |
| 107 | ARRAY_SIZE(user_table)); |
| 108 | } |
| 109 | if (!ns->sysctls) { |
| 110 | kfree(tbl); |
| 111 | retire_sysctl_set(&ns->set); |
| 112 | return false; |
| 113 | } |
| 114 | #endif |
| 115 | return true; |
| 116 | } |
| 117 | |
| 118 | void retire_userns_sysctls(struct user_namespace *ns) |
| 119 | { |
| 120 | #ifdef CONFIG_SYSCTL |
| 121 | const struct ctl_table *tbl; |
| 122 | |
| 123 | tbl = ns->sysctls->ctl_table_arg; |
| 124 | unregister_sysctl_table(ns->sysctls); |
| 125 | retire_sysctl_set(&ns->set); |
| 126 | kfree(tbl); |
| 127 | #endif |
| 128 | } |
| 129 | |
| 130 | static struct ucounts *find_ucounts(struct user_namespace *ns, kuid_t uid, struct hlist_head *hashent) |
| 131 | { |
| 132 | struct ucounts *ucounts; |
| 133 | |
| 134 | hlist_for_each_entry(ucounts, hashent, node) { |
| 135 | if (uid_eq(ucounts->uid, uid) && (ucounts->ns == ns)) |
| 136 | return ucounts; |
| 137 | } |
| 138 | return NULL; |
| 139 | } |
| 140 | |
| 141 | static void hlist_add_ucounts(struct ucounts *ucounts) |
| 142 | { |
| 143 | struct hlist_head *hashent = ucounts_hashentry(ucounts->ns, ucounts->uid); |
| 144 | spin_lock_irq(&ucounts_lock); |
| 145 | hlist_add_head(&ucounts->node, hashent); |
| 146 | spin_unlock_irq(&ucounts_lock); |
| 147 | } |
| 148 | |
| 149 | static inline bool get_ucounts_or_wrap(struct ucounts *ucounts) |
| 150 | { |
| 151 | /* Returns true on a successful get, false if the count wraps. */ |
| 152 | return !atomic_add_negative(1, &ucounts->count); |
| 153 | } |
| 154 | |
| 155 | struct ucounts *get_ucounts(struct ucounts *ucounts) |
| 156 | { |
| 157 | if (!get_ucounts_or_wrap(ucounts)) { |
| 158 | put_ucounts(ucounts); |
| 159 | ucounts = NULL; |
| 160 | } |
| 161 | return ucounts; |
| 162 | } |
| 163 | |
| 164 | struct ucounts *alloc_ucounts(struct user_namespace *ns, kuid_t uid) |
| 165 | { |
| 166 | struct hlist_head *hashent = ucounts_hashentry(ns, uid); |
| 167 | struct ucounts *ucounts, *new; |
| 168 | bool wrapped; |
| 169 | |
| 170 | spin_lock_irq(&ucounts_lock); |
| 171 | ucounts = find_ucounts(ns, uid, hashent); |
| 172 | if (!ucounts) { |
| 173 | spin_unlock_irq(&ucounts_lock); |
| 174 | |
| 175 | new = kzalloc(sizeof(*new), GFP_KERNEL); |
| 176 | if (!new) |
| 177 | return NULL; |
| 178 | |
| 179 | new->ns = ns; |
| 180 | new->uid = uid; |
| 181 | atomic_set(&new->count, 1); |
| 182 | |
| 183 | spin_lock_irq(&ucounts_lock); |
| 184 | ucounts = find_ucounts(ns, uid, hashent); |
| 185 | if (ucounts) { |
| 186 | kfree(new); |
| 187 | } else { |
| 188 | hlist_add_head(&new->node, hashent); |
| 189 | get_user_ns(new->ns); |
| 190 | spin_unlock_irq(&ucounts_lock); |
| 191 | return new; |
| 192 | } |
| 193 | } |
| 194 | wrapped = !get_ucounts_or_wrap(ucounts); |
| 195 | spin_unlock_irq(&ucounts_lock); |
| 196 | if (wrapped) { |
| 197 | put_ucounts(ucounts); |
| 198 | return NULL; |
| 199 | } |
| 200 | return ucounts; |
| 201 | } |
| 202 | |
| 203 | void put_ucounts(struct ucounts *ucounts) |
| 204 | { |
| 205 | unsigned long flags; |
| 206 | |
| 207 | if (atomic_dec_and_lock_irqsave(&ucounts->count, &ucounts_lock, flags)) { |
| 208 | hlist_del_init(&ucounts->node); |
| 209 | spin_unlock_irqrestore(&ucounts_lock, flags); |
| 210 | put_user_ns(ucounts->ns); |
| 211 | kfree(ucounts); |
| 212 | } |
| 213 | } |
| 214 | |
| 215 | static inline bool atomic_long_inc_below(atomic_long_t *v, int u) |
| 216 | { |
| 217 | long c, old; |
| 218 | c = atomic_long_read(v); |
| 219 | for (;;) { |
| 220 | if (unlikely(c >= u)) |
| 221 | return false; |
| 222 | old = atomic_long_cmpxchg(v, c, c+1); |
| 223 | if (likely(old == c)) |
| 224 | return true; |
| 225 | c = old; |
| 226 | } |
| 227 | } |
| 228 | |
| 229 | struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid, |
| 230 | enum ucount_type type) |
| 231 | { |
| 232 | struct ucounts *ucounts, *iter, *bad; |
| 233 | struct user_namespace *tns; |
| 234 | ucounts = alloc_ucounts(ns, uid); |
| 235 | for (iter = ucounts; iter; iter = tns->ucounts) { |
| 236 | long max; |
| 237 | tns = iter->ns; |
| 238 | max = READ_ONCE(tns->ucount_max[type]); |
| 239 | if (!atomic_long_inc_below(&iter->ucount[type], max)) |
| 240 | goto fail; |
| 241 | } |
| 242 | return ucounts; |
| 243 | fail: |
| 244 | bad = iter; |
| 245 | for (iter = ucounts; iter != bad; iter = iter->ns->ucounts) |
| 246 | atomic_long_dec(&iter->ucount[type]); |
| 247 | |
| 248 | put_ucounts(ucounts); |
| 249 | return NULL; |
| 250 | } |
| 251 | |
| 252 | void dec_ucount(struct ucounts *ucounts, enum ucount_type type) |
| 253 | { |
| 254 | struct ucounts *iter; |
| 255 | for (iter = ucounts; iter; iter = iter->ns->ucounts) { |
| 256 | long dec = atomic_long_dec_if_positive(&iter->ucount[type]); |
| 257 | WARN_ON_ONCE(dec < 0); |
| 258 | } |
| 259 | put_ucounts(ucounts); |
| 260 | } |
| 261 | |
| 262 | long inc_rlimit_ucounts(struct ucounts *ucounts, enum rlimit_type type, long v) |
| 263 | { |
| 264 | struct ucounts *iter; |
| 265 | long max = LONG_MAX; |
| 266 | long ret = 0; |
| 267 | |
| 268 | for (iter = ucounts; iter; iter = iter->ns->ucounts) { |
| 269 | long new = atomic_long_add_return(v, &iter->rlimit[type]); |
| 270 | if (new < 0 || new > max) |
| 271 | ret = LONG_MAX; |
| 272 | else if (iter == ucounts) |
| 273 | ret = new; |
| 274 | max = get_userns_rlimit_max(iter->ns, type); |
| 275 | } |
| 276 | return ret; |
| 277 | } |
| 278 | |
| 279 | bool dec_rlimit_ucounts(struct ucounts *ucounts, enum rlimit_type type, long v) |
| 280 | { |
| 281 | struct ucounts *iter; |
| 282 | long new = -1; /* Silence compiler warning */ |
| 283 | for (iter = ucounts; iter; iter = iter->ns->ucounts) { |
| 284 | long dec = atomic_long_sub_return(v, &iter->rlimit[type]); |
| 285 | WARN_ON_ONCE(dec < 0); |
| 286 | if (iter == ucounts) |
| 287 | new = dec; |
| 288 | } |
| 289 | return (new == 0); |
| 290 | } |
| 291 | |
| 292 | static void do_dec_rlimit_put_ucounts(struct ucounts *ucounts, |
| 293 | struct ucounts *last, enum rlimit_type type) |
| 294 | { |
| 295 | struct ucounts *iter, *next; |
| 296 | for (iter = ucounts; iter != last; iter = next) { |
| 297 | long dec = atomic_long_sub_return(1, &iter->rlimit[type]); |
| 298 | WARN_ON_ONCE(dec < 0); |
| 299 | next = iter->ns->ucounts; |
| 300 | if (dec == 0) |
| 301 | put_ucounts(iter); |
| 302 | } |
| 303 | } |
| 304 | |
| 305 | void dec_rlimit_put_ucounts(struct ucounts *ucounts, enum rlimit_type type) |
| 306 | { |
| 307 | do_dec_rlimit_put_ucounts(ucounts, NULL, type); |
| 308 | } |
| 309 | |
| 310 | long inc_rlimit_get_ucounts(struct ucounts *ucounts, enum rlimit_type type) |
| 311 | { |
| 312 | /* Caller must hold a reference to ucounts */ |
| 313 | struct ucounts *iter; |
| 314 | long max = LONG_MAX; |
| 315 | long dec, ret = 0; |
| 316 | |
| 317 | for (iter = ucounts; iter; iter = iter->ns->ucounts) { |
| 318 | long new = atomic_long_add_return(1, &iter->rlimit[type]); |
| 319 | if (new < 0 || new > max) |
| 320 | goto unwind; |
| 321 | if (iter == ucounts) |
| 322 | ret = new; |
| 323 | max = get_userns_rlimit_max(iter->ns, type); |
| 324 | /* |
| 325 | * Grab an extra ucount reference for the caller when |
| 326 | * the rlimit count was previously 0. |
| 327 | */ |
| 328 | if (new != 1) |
| 329 | continue; |
| 330 | if (!get_ucounts(iter)) |
| 331 | goto dec_unwind; |
| 332 | } |
| 333 | return ret; |
| 334 | dec_unwind: |
| 335 | dec = atomic_long_sub_return(1, &iter->rlimit[type]); |
| 336 | WARN_ON_ONCE(dec < 0); |
| 337 | unwind: |
| 338 | do_dec_rlimit_put_ucounts(ucounts, iter, type); |
| 339 | return 0; |
| 340 | } |
| 341 | |
| 342 | bool is_rlimit_overlimit(struct ucounts *ucounts, enum rlimit_type type, unsigned long rlimit) |
| 343 | { |
| 344 | struct ucounts *iter; |
| 345 | long max = rlimit; |
| 346 | if (rlimit > LONG_MAX) |
| 347 | max = LONG_MAX; |
| 348 | for (iter = ucounts; iter; iter = iter->ns->ucounts) { |
| 349 | long val = get_rlimit_value(iter, type); |
| 350 | if (val < 0 || val > max) |
| 351 | return true; |
| 352 | max = get_userns_rlimit_max(iter->ns, type); |
| 353 | } |
| 354 | return false; |
| 355 | } |
| 356 | |
| 357 | static __init int user_namespace_sysctl_init(void) |
| 358 | { |
| 359 | #ifdef CONFIG_SYSCTL |
| 360 | static struct ctl_table_header *user_header; |
| 361 | static struct ctl_table empty[1]; |
| 362 | /* |
| 363 | * It is necessary to register the user directory in the |
| 364 | * default set so that registrations in the child sets work |
| 365 | * properly. |
| 366 | */ |
| 367 | user_header = register_sysctl_sz("user", empty, 0); |
| 368 | kmemleak_ignore(user_header); |
| 369 | BUG_ON(!user_header); |
| 370 | BUG_ON(!setup_userns_sysctls(&init_user_ns)); |
| 371 | #endif |
| 372 | hlist_add_ucounts(&init_ucounts); |
| 373 | inc_rlimit_ucounts(&init_ucounts, UCOUNT_RLIMIT_NPROC, 1); |
| 374 | return 0; |
| 375 | } |
| 376 | subsys_initcall(user_namespace_sysctl_init); |