1dbec2846SEric W. Biederman /* 2dbec2846SEric W. Biederman * This program is free software; you can redistribute it and/or 3dbec2846SEric W. Biederman * modify it under the terms of the GNU General Public License as 4dbec2846SEric W. Biederman * published by the Free Software Foundation, version 2 of the 5dbec2846SEric W. Biederman * License. 6dbec2846SEric W. Biederman */ 7dbec2846SEric W. Biederman 8dbec2846SEric W. Biederman #include <linux/stat.h> 9dbec2846SEric W. Biederman #include <linux/sysctl.h> 10dbec2846SEric W. Biederman #include <linux/slab.h> 11f6b2db1aSEric W. Biederman #include <linux/hash.h> 12dbec2846SEric W. Biederman #include <linux/user_namespace.h> 13dbec2846SEric W. Biederman 14f6b2db1aSEric W. Biederman #define UCOUNTS_HASHTABLE_BITS 10 15f6b2db1aSEric W. Biederman static struct hlist_head ucounts_hashtable[(1 << UCOUNTS_HASHTABLE_BITS)]; 16f6b2db1aSEric W. Biederman static DEFINE_SPINLOCK(ucounts_lock); 17f6b2db1aSEric W. Biederman 18f6b2db1aSEric W. Biederman #define ucounts_hashfn(ns, uid) \ 19f6b2db1aSEric W. Biederman hash_long((unsigned long)__kuid_val(uid) + (unsigned long)(ns), \ 20f6b2db1aSEric W. Biederman UCOUNTS_HASHTABLE_BITS) 21f6b2db1aSEric W. Biederman #define ucounts_hashentry(ns, uid) \ 22f6b2db1aSEric W. Biederman (ucounts_hashtable + ucounts_hashfn(ns, uid)) 23f6b2db1aSEric W. Biederman 24f6b2db1aSEric W. Biederman 25dbec2846SEric W. Biederman #ifdef CONFIG_SYSCTL 26dbec2846SEric W. Biederman static struct ctl_table_set * 27dbec2846SEric W. Biederman set_lookup(struct ctl_table_root *root) 28dbec2846SEric W. Biederman { 29dbec2846SEric W. Biederman return ¤t_user_ns()->set; 30dbec2846SEric W. Biederman } 31dbec2846SEric W. Biederman 32dbec2846SEric W. Biederman static int set_is_seen(struct ctl_table_set *set) 33dbec2846SEric W. Biederman { 34dbec2846SEric W. Biederman return ¤t_user_ns()->set == set; 35dbec2846SEric W. Biederman } 36dbec2846SEric W. Biederman 37dbec2846SEric W. Biederman static int set_permissions(struct ctl_table_header *head, 38dbec2846SEric W. Biederman struct ctl_table *table) 39dbec2846SEric W. Biederman { 40dbec2846SEric W. Biederman struct user_namespace *user_ns = 41dbec2846SEric W. Biederman container_of(head->set, struct user_namespace, set); 42dbec2846SEric W. Biederman int mode; 43dbec2846SEric W. Biederman 44dbec2846SEric W. Biederman /* Allow users with CAP_SYS_RESOURCE unrestrained access */ 45dbec2846SEric W. Biederman if (ns_capable(user_ns, CAP_SYS_RESOURCE)) 46dbec2846SEric W. Biederman mode = (table->mode & S_IRWXU) >> 6; 47dbec2846SEric W. Biederman else 48dbec2846SEric W. Biederman /* Allow all others at most read-only access */ 49dbec2846SEric W. Biederman mode = table->mode & S_IROTH; 50dbec2846SEric W. Biederman return (mode << 6) | (mode << 3) | mode; 51dbec2846SEric W. Biederman } 52dbec2846SEric W. Biederman 53dbec2846SEric W. Biederman static struct ctl_table_root set_root = { 54dbec2846SEric W. Biederman .lookup = set_lookup, 55dbec2846SEric W. Biederman .permissions = set_permissions, 56dbec2846SEric W. Biederman }; 57dbec2846SEric W. Biederman 58b376c3e1SEric W. Biederman static int zero = 0; 59b376c3e1SEric W. Biederman static int int_max = INT_MAX; 6025f9c081SEric W. Biederman #define UCOUNT_ENTRY(name) \ 6125f9c081SEric W. Biederman { \ 6225f9c081SEric W. Biederman .procname = name, \ 6325f9c081SEric W. Biederman .maxlen = sizeof(int), \ 6425f9c081SEric W. Biederman .mode = 0644, \ 6525f9c081SEric W. Biederman .proc_handler = proc_dointvec_minmax, \ 6625f9c081SEric W. Biederman .extra1 = &zero, \ 6725f9c081SEric W. Biederman .extra2 = &int_max, \ 6825f9c081SEric W. Biederman } 69f6b2db1aSEric W. Biederman static struct ctl_table user_table[] = { 7025f9c081SEric W. Biederman UCOUNT_ENTRY("max_user_namespaces"), 71*f333c700SEric W. Biederman UCOUNT_ENTRY("max_pid_namespaces"), 72dbec2846SEric W. Biederman { } 73dbec2846SEric W. Biederman }; 74dbec2846SEric W. Biederman #endif /* CONFIG_SYSCTL */ 75dbec2846SEric W. Biederman 76dbec2846SEric W. Biederman bool setup_userns_sysctls(struct user_namespace *ns) 77dbec2846SEric W. Biederman { 78dbec2846SEric W. Biederman #ifdef CONFIG_SYSCTL 79dbec2846SEric W. Biederman struct ctl_table *tbl; 80dbec2846SEric W. Biederman setup_sysctl_set(&ns->set, &set_root, set_is_seen); 81f6b2db1aSEric W. Biederman tbl = kmemdup(user_table, sizeof(user_table), GFP_KERNEL); 82dbec2846SEric W. Biederman if (tbl) { 8325f9c081SEric W. Biederman int i; 8425f9c081SEric W. Biederman for (i = 0; i < UCOUNT_COUNTS; i++) { 8525f9c081SEric W. Biederman tbl[i].data = &ns->ucount_max[i]; 8625f9c081SEric W. Biederman } 87f6b2db1aSEric W. Biederman ns->sysctls = __register_sysctl_table(&ns->set, "user", tbl); 88dbec2846SEric W. Biederman } 89dbec2846SEric W. Biederman if (!ns->sysctls) { 90dbec2846SEric W. Biederman kfree(tbl); 91dbec2846SEric W. Biederman retire_sysctl_set(&ns->set); 92dbec2846SEric W. Biederman return false; 93dbec2846SEric W. Biederman } 94dbec2846SEric W. Biederman #endif 95dbec2846SEric W. Biederman return true; 96dbec2846SEric W. Biederman } 97dbec2846SEric W. Biederman 98dbec2846SEric W. Biederman void retire_userns_sysctls(struct user_namespace *ns) 99dbec2846SEric W. Biederman { 100dbec2846SEric W. Biederman #ifdef CONFIG_SYSCTL 101dbec2846SEric W. Biederman struct ctl_table *tbl; 102dbec2846SEric W. Biederman 103dbec2846SEric W. Biederman tbl = ns->sysctls->ctl_table_arg; 104dbec2846SEric W. Biederman unregister_sysctl_table(ns->sysctls); 105dbec2846SEric W. Biederman retire_sysctl_set(&ns->set); 106dbec2846SEric W. Biederman kfree(tbl); 107dbec2846SEric W. Biederman #endif 108dbec2846SEric W. Biederman } 109dbec2846SEric W. Biederman 110f6b2db1aSEric W. Biederman static struct ucounts *find_ucounts(struct user_namespace *ns, kuid_t uid, struct hlist_head *hashent) 111f6b2db1aSEric W. Biederman { 112f6b2db1aSEric W. Biederman struct ucounts *ucounts; 113f6b2db1aSEric W. Biederman 114f6b2db1aSEric W. Biederman hlist_for_each_entry(ucounts, hashent, node) { 115f6b2db1aSEric W. Biederman if (uid_eq(ucounts->uid, uid) && (ucounts->ns == ns)) 116f6b2db1aSEric W. Biederman return ucounts; 117f6b2db1aSEric W. Biederman } 118f6b2db1aSEric W. Biederman return NULL; 119f6b2db1aSEric W. Biederman } 120f6b2db1aSEric W. Biederman 121f6b2db1aSEric W. Biederman static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid) 122f6b2db1aSEric W. Biederman { 123f6b2db1aSEric W. Biederman struct hlist_head *hashent = ucounts_hashentry(ns, uid); 124f6b2db1aSEric W. Biederman struct ucounts *ucounts, *new; 125f6b2db1aSEric W. Biederman 126f6b2db1aSEric W. Biederman spin_lock(&ucounts_lock); 127f6b2db1aSEric W. Biederman ucounts = find_ucounts(ns, uid, hashent); 128f6b2db1aSEric W. Biederman if (!ucounts) { 129f6b2db1aSEric W. Biederman spin_unlock(&ucounts_lock); 130f6b2db1aSEric W. Biederman 131f6b2db1aSEric W. Biederman new = kzalloc(sizeof(*new), GFP_KERNEL); 132f6b2db1aSEric W. Biederman if (!new) 133f6b2db1aSEric W. Biederman return NULL; 134f6b2db1aSEric W. Biederman 135f6b2db1aSEric W. Biederman new->ns = ns; 136f6b2db1aSEric W. Biederman new->uid = uid; 137f6b2db1aSEric W. Biederman atomic_set(&new->count, 0); 138f6b2db1aSEric W. Biederman 139f6b2db1aSEric W. Biederman spin_lock(&ucounts_lock); 140f6b2db1aSEric W. Biederman ucounts = find_ucounts(ns, uid, hashent); 141f6b2db1aSEric W. Biederman if (ucounts) { 142f6b2db1aSEric W. Biederman kfree(new); 143f6b2db1aSEric W. Biederman } else { 144f6b2db1aSEric W. Biederman hlist_add_head(&new->node, hashent); 145f6b2db1aSEric W. Biederman ucounts = new; 146f6b2db1aSEric W. Biederman } 147f6b2db1aSEric W. Biederman } 148f6b2db1aSEric W. Biederman if (!atomic_add_unless(&ucounts->count, 1, INT_MAX)) 149f6b2db1aSEric W. Biederman ucounts = NULL; 150f6b2db1aSEric W. Biederman spin_unlock(&ucounts_lock); 151f6b2db1aSEric W. Biederman return ucounts; 152f6b2db1aSEric W. Biederman } 153f6b2db1aSEric W. Biederman 154f6b2db1aSEric W. Biederman static void put_ucounts(struct ucounts *ucounts) 155f6b2db1aSEric W. Biederman { 156f6b2db1aSEric W. Biederman if (atomic_dec_and_test(&ucounts->count)) { 157f6b2db1aSEric W. Biederman spin_lock(&ucounts_lock); 158f6b2db1aSEric W. Biederman hlist_del_init(&ucounts->node); 159f6b2db1aSEric W. Biederman spin_unlock(&ucounts_lock); 160f6b2db1aSEric W. Biederman 161f6b2db1aSEric W. Biederman kfree(ucounts); 162f6b2db1aSEric W. Biederman } 163f6b2db1aSEric W. Biederman } 164f6b2db1aSEric W. Biederman 165b376c3e1SEric W. Biederman static inline bool atomic_inc_below(atomic_t *v, int u) 166b376c3e1SEric W. Biederman { 167b376c3e1SEric W. Biederman int c, old; 168b376c3e1SEric W. Biederman c = atomic_read(v); 169b376c3e1SEric W. Biederman for (;;) { 170b376c3e1SEric W. Biederman if (unlikely(c >= u)) 171b376c3e1SEric W. Biederman return false; 172b376c3e1SEric W. Biederman old = atomic_cmpxchg(v, c, c+1); 173b376c3e1SEric W. Biederman if (likely(old == c)) 174b376c3e1SEric W. Biederman return true; 175b376c3e1SEric W. Biederman c = old; 176b376c3e1SEric W. Biederman } 177b376c3e1SEric W. Biederman } 178b376c3e1SEric W. Biederman 17925f9c081SEric W. Biederman struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid, 18025f9c081SEric W. Biederman enum ucount_type type) 181b376c3e1SEric W. Biederman { 182f6b2db1aSEric W. Biederman struct ucounts *ucounts, *iter, *bad; 183f6b2db1aSEric W. Biederman struct user_namespace *tns; 184f6b2db1aSEric W. Biederman ucounts = get_ucounts(ns, uid); 185f6b2db1aSEric W. Biederman for (iter = ucounts; iter; iter = tns->ucounts) { 186f6b2db1aSEric W. Biederman int max; 187f6b2db1aSEric W. Biederman tns = iter->ns; 18825f9c081SEric W. Biederman max = READ_ONCE(tns->ucount_max[type]); 18925f9c081SEric W. Biederman if (!atomic_inc_below(&iter->ucount[type], max)) 190b376c3e1SEric W. Biederman goto fail; 191b376c3e1SEric W. Biederman } 192f6b2db1aSEric W. Biederman return ucounts; 193b376c3e1SEric W. Biederman fail: 194f6b2db1aSEric W. Biederman bad = iter; 195f6b2db1aSEric W. Biederman for (iter = ucounts; iter != bad; iter = iter->ns->ucounts) 19625f9c081SEric W. Biederman atomic_dec(&iter->ucount[type]); 197b376c3e1SEric W. Biederman 198f6b2db1aSEric W. Biederman put_ucounts(ucounts); 199f6b2db1aSEric W. Biederman return NULL; 200b376c3e1SEric W. Biederman } 201b376c3e1SEric W. Biederman 20225f9c081SEric W. Biederman void dec_ucount(struct ucounts *ucounts, enum ucount_type type) 203b376c3e1SEric W. Biederman { 204f6b2db1aSEric W. Biederman struct ucounts *iter; 205f6b2db1aSEric W. Biederman for (iter = ucounts; iter; iter = iter->ns->ucounts) { 20625f9c081SEric W. Biederman int dec = atomic_dec_if_positive(&iter->ucount[type]); 207b376c3e1SEric W. Biederman WARN_ON_ONCE(dec < 0); 208b376c3e1SEric W. Biederman } 209f6b2db1aSEric W. Biederman put_ucounts(ucounts); 210b376c3e1SEric W. Biederman } 211b376c3e1SEric W. Biederman 212dbec2846SEric W. Biederman static __init int user_namespace_sysctl_init(void) 213dbec2846SEric W. Biederman { 214dbec2846SEric W. Biederman #ifdef CONFIG_SYSCTL 215f6b2db1aSEric W. Biederman static struct ctl_table_header *user_header; 216dbec2846SEric W. Biederman static struct ctl_table empty[1]; 217dbec2846SEric W. Biederman /* 218f6b2db1aSEric W. Biederman * It is necessary to register the user directory in the 219dbec2846SEric W. Biederman * default set so that registrations in the child sets work 220dbec2846SEric W. Biederman * properly. 221dbec2846SEric W. Biederman */ 222f6b2db1aSEric W. Biederman user_header = register_sysctl("user", empty); 223f6b2db1aSEric W. Biederman BUG_ON(!user_header); 224dbec2846SEric W. Biederman BUG_ON(!setup_userns_sysctls(&init_user_ns)); 225dbec2846SEric W. Biederman #endif 226dbec2846SEric W. Biederman return 0; 227dbec2846SEric W. Biederman } 228dbec2846SEric W. Biederman subsys_initcall(user_namespace_sysctl_init); 229dbec2846SEric W. Biederman 230dbec2846SEric W. Biederman 231