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 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 }; 92 #endif /* CONFIG_SYSCTL */ 93 94 bool 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 } 118 119 void 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 } 130 131 static 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 } 141 142 static 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 } 149 150 static 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 } 155 156 struct 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 } 164 165 struct 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 } 203 204 void 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 } 215 216 static 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 } 229 230 struct 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; 244 fail: 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 } 252 253 void 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 } 262 263 long 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 } 279 280 bool 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 } 292 293 static 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 } 305 306 void dec_rlimit_put_ucounts(struct ucounts *ucounts, enum rlimit_type type) 307 { 308 do_dec_rlimit_put_ucounts(ucounts, NULL, type); 309 } 310 311 long 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; 335 dec_unwind: 336 dec = atomic_long_sub_return(1, &iter->rlimit[type]); 337 WARN_ON_ONCE(dec < 0); 338 unwind: 339 do_dec_rlimit_put_ucounts(ucounts, iter, type); 340 return 0; 341 } 342 343 bool 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 } 357 358 static __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 } 377 subsys_initcall(user_namespace_sysctl_init); 378