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 { }, 93 { }, 94 { } 95 }; 96 #endif /* CONFIG_SYSCTL */ 97 98 bool setup_userns_sysctls(struct user_namespace *ns) 99 { 100 #ifdef CONFIG_SYSCTL 101 struct ctl_table *tbl; 102 103 BUILD_BUG_ON(ARRAY_SIZE(user_table) != UCOUNT_COUNTS + 1); 104 setup_sysctl_set(&ns->set, &set_root, set_is_seen); 105 tbl = kmemdup(user_table, sizeof(user_table), GFP_KERNEL); 106 if (tbl) { 107 int i; 108 for (i = 0; i < UCOUNT_COUNTS; i++) { 109 tbl[i].data = &ns->ucount_max[i]; 110 } 111 ns->sysctls = __register_sysctl_table(&ns->set, "user", tbl); 112 } 113 if (!ns->sysctls) { 114 kfree(tbl); 115 retire_sysctl_set(&ns->set); 116 return false; 117 } 118 #endif 119 return true; 120 } 121 122 void retire_userns_sysctls(struct user_namespace *ns) 123 { 124 #ifdef CONFIG_SYSCTL 125 struct ctl_table *tbl; 126 127 tbl = ns->sysctls->ctl_table_arg; 128 unregister_sysctl_table(ns->sysctls); 129 retire_sysctl_set(&ns->set); 130 kfree(tbl); 131 #endif 132 } 133 134 static struct ucounts *find_ucounts(struct user_namespace *ns, kuid_t uid, struct hlist_head *hashent) 135 { 136 struct ucounts *ucounts; 137 138 hlist_for_each_entry(ucounts, hashent, node) { 139 if (uid_eq(ucounts->uid, uid) && (ucounts->ns == ns)) 140 return ucounts; 141 } 142 return NULL; 143 } 144 145 static void hlist_add_ucounts(struct ucounts *ucounts) 146 { 147 struct hlist_head *hashent = ucounts_hashentry(ucounts->ns, ucounts->uid); 148 spin_lock_irq(&ucounts_lock); 149 hlist_add_head(&ucounts->node, hashent); 150 spin_unlock_irq(&ucounts_lock); 151 } 152 153 struct ucounts *get_ucounts(struct ucounts *ucounts) 154 { 155 if (ucounts && atomic_add_negative(1, &ucounts->count)) { 156 put_ucounts(ucounts); 157 ucounts = NULL; 158 } 159 return ucounts; 160 } 161 162 struct ucounts *alloc_ucounts(struct user_namespace *ns, kuid_t uid) 163 { 164 struct hlist_head *hashent = ucounts_hashentry(ns, uid); 165 struct ucounts *ucounts, *new; 166 long overflow; 167 168 spin_lock_irq(&ucounts_lock); 169 ucounts = find_ucounts(ns, uid, hashent); 170 if (!ucounts) { 171 spin_unlock_irq(&ucounts_lock); 172 173 new = kzalloc(sizeof(*new), GFP_KERNEL); 174 if (!new) 175 return NULL; 176 177 new->ns = ns; 178 new->uid = uid; 179 atomic_set(&new->count, 1); 180 181 spin_lock_irq(&ucounts_lock); 182 ucounts = find_ucounts(ns, uid, hashent); 183 if (ucounts) { 184 kfree(new); 185 } else { 186 hlist_add_head(&new->node, hashent); 187 spin_unlock_irq(&ucounts_lock); 188 return new; 189 } 190 } 191 overflow = atomic_add_negative(1, &ucounts->count); 192 spin_unlock_irq(&ucounts_lock); 193 if (overflow) { 194 put_ucounts(ucounts); 195 return NULL; 196 } 197 return ucounts; 198 } 199 200 void put_ucounts(struct ucounts *ucounts) 201 { 202 unsigned long flags; 203 204 if (atomic_dec_and_lock_irqsave(&ucounts->count, &ucounts_lock, flags)) { 205 hlist_del_init(&ucounts->node); 206 spin_unlock_irqrestore(&ucounts_lock, flags); 207 kfree(ucounts); 208 } 209 } 210 211 static inline bool atomic_long_inc_below(atomic_long_t *v, int u) 212 { 213 long c, old; 214 c = atomic_long_read(v); 215 for (;;) { 216 if (unlikely(c >= u)) 217 return false; 218 old = atomic_long_cmpxchg(v, c, c+1); 219 if (likely(old == c)) 220 return true; 221 c = old; 222 } 223 } 224 225 struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid, 226 enum ucount_type type) 227 { 228 struct ucounts *ucounts, *iter, *bad; 229 struct user_namespace *tns; 230 ucounts = alloc_ucounts(ns, uid); 231 for (iter = ucounts; iter; iter = tns->ucounts) { 232 long max; 233 tns = iter->ns; 234 max = READ_ONCE(tns->ucount_max[type]); 235 if (!atomic_long_inc_below(&iter->ucount[type], max)) 236 goto fail; 237 } 238 return ucounts; 239 fail: 240 bad = iter; 241 for (iter = ucounts; iter != bad; iter = iter->ns->ucounts) 242 atomic_long_dec(&iter->ucount[type]); 243 244 put_ucounts(ucounts); 245 return NULL; 246 } 247 248 void dec_ucount(struct ucounts *ucounts, enum ucount_type type) 249 { 250 struct ucounts *iter; 251 for (iter = ucounts; iter; iter = iter->ns->ucounts) { 252 long dec = atomic_long_dec_if_positive(&iter->ucount[type]); 253 WARN_ON_ONCE(dec < 0); 254 } 255 put_ucounts(ucounts); 256 } 257 258 long inc_rlimit_ucounts(struct ucounts *ucounts, enum ucount_type type, long v) 259 { 260 struct ucounts *iter; 261 long ret = 0; 262 263 for (iter = ucounts; iter; iter = iter->ns->ucounts) { 264 long max = READ_ONCE(iter->ns->ucount_max[type]); 265 long new = atomic_long_add_return(v, &iter->ucount[type]); 266 if (new < 0 || new > max) 267 ret = LONG_MAX; 268 else if (iter == ucounts) 269 ret = new; 270 } 271 return ret; 272 } 273 274 bool dec_rlimit_ucounts(struct ucounts *ucounts, enum ucount_type type, long v) 275 { 276 struct ucounts *iter; 277 long new = -1; /* Silence compiler warning */ 278 for (iter = ucounts; iter; iter = iter->ns->ucounts) { 279 long dec = atomic_long_add_return(-v, &iter->ucount[type]); 280 WARN_ON_ONCE(dec < 0); 281 if (iter == ucounts) 282 new = dec; 283 } 284 return (new == 0); 285 } 286 287 bool is_ucounts_overlimit(struct ucounts *ucounts, enum ucount_type type, unsigned long max) 288 { 289 struct ucounts *iter; 290 if (get_ucounts_value(ucounts, type) > max) 291 return true; 292 for (iter = ucounts; iter; iter = iter->ns->ucounts) { 293 max = READ_ONCE(iter->ns->ucount_max[type]); 294 if (get_ucounts_value(iter, type) > max) 295 return true; 296 } 297 return false; 298 } 299 300 static __init int user_namespace_sysctl_init(void) 301 { 302 #ifdef CONFIG_SYSCTL 303 static struct ctl_table_header *user_header; 304 static struct ctl_table empty[1]; 305 /* 306 * It is necessary to register the user directory in the 307 * default set so that registrations in the child sets work 308 * properly. 309 */ 310 user_header = register_sysctl("user", empty); 311 kmemleak_ignore(user_header); 312 BUG_ON(!user_header); 313 BUG_ON(!setup_userns_sysctls(&init_user_ns)); 314 #endif 315 hlist_add_ucounts(&init_ucounts); 316 inc_rlimit_ucounts(&init_ucounts, UCOUNT_RLIMIT_NPROC, 1); 317 return 0; 318 } 319 subsys_initcall(user_namespace_sysctl_init); 320