| /* |
| * This program is free software; you can redistribute it and/or |
| * modify it under the terms of the GNU General Public License as |
| * published by the Free Software Foundation, version 2 of the |
| * License. |
| */ |
| |
| #include <linux/stat.h> |
| #include <linux/sysctl.h> |
| #include <linux/slab.h> |
| #include <linux/hash.h> |
| #include <linux/user_namespace.h> |
| |
| #define UCOUNTS_HASHTABLE_BITS 10 |
| static struct hlist_head ucounts_hashtable[(1 << UCOUNTS_HASHTABLE_BITS)]; |
| static DEFINE_SPINLOCK(ucounts_lock); |
| |
| #define ucounts_hashfn(ns, uid) \ |
| hash_long((unsigned long)__kuid_val(uid) + (unsigned long)(ns), \ |
| UCOUNTS_HASHTABLE_BITS) |
| #define ucounts_hashentry(ns, uid) \ |
| (ucounts_hashtable + ucounts_hashfn(ns, uid)) |
| |
| |
| #ifdef CONFIG_SYSCTL |
| static struct ctl_table_set * |
| set_lookup(struct ctl_table_root *root) |
| { |
| return ¤t_user_ns()->set; |
| } |
| |
| static int set_is_seen(struct ctl_table_set *set) |
| { |
| return ¤t_user_ns()->set == set; |
| } |
| |
| static int set_permissions(struct ctl_table_header *head, |
| struct ctl_table *table) |
| { |
| struct user_namespace *user_ns = |
| container_of(head->set, struct user_namespace, set); |
| int mode; |
| |
| /* Allow users with CAP_SYS_RESOURCE unrestrained access */ |
| if (ns_capable(user_ns, CAP_SYS_RESOURCE)) |
| mode = (table->mode & S_IRWXU) >> 6; |
| else |
| /* Allow all others at most read-only access */ |
| mode = table->mode & S_IROTH; |
| return (mode << 6) | (mode << 3) | mode; |
| } |
| |
| static struct ctl_table_root set_root = { |
| .lookup = set_lookup, |
| .permissions = set_permissions, |
| }; |
| |
| static int zero = 0; |
| static int int_max = INT_MAX; |
| #define UCOUNT_ENTRY(name) \ |
| { \ |
| .procname = name, \ |
| .maxlen = sizeof(int), \ |
| .mode = 0644, \ |
| .proc_handler = proc_dointvec_minmax, \ |
| .extra1 = &zero, \ |
| .extra2 = &int_max, \ |
| } |
| static struct ctl_table user_table[] = { |
| UCOUNT_ENTRY("max_user_namespaces"), |
| UCOUNT_ENTRY("max_pid_namespaces"), |
| UCOUNT_ENTRY("max_uts_namespaces"), |
| UCOUNT_ENTRY("max_ipc_namespaces"), |
| UCOUNT_ENTRY("max_net_namespaces"), |
| UCOUNT_ENTRY("max_mnt_namespaces"), |
| UCOUNT_ENTRY("max_cgroup_namespaces"), |
| { } |
| }; |
| #endif /* CONFIG_SYSCTL */ |
| |
| bool setup_userns_sysctls(struct user_namespace *ns) |
| { |
| #ifdef CONFIG_SYSCTL |
| struct ctl_table *tbl; |
| setup_sysctl_set(&ns->set, &set_root, set_is_seen); |
| tbl = kmemdup(user_table, sizeof(user_table), GFP_KERNEL); |
| if (tbl) { |
| int i; |
| for (i = 0; i < UCOUNT_COUNTS; i++) { |
| tbl[i].data = &ns->ucount_max[i]; |
| } |
| ns->sysctls = __register_sysctl_table(&ns->set, "user", tbl); |
| } |
| if (!ns->sysctls) { |
| kfree(tbl); |
| retire_sysctl_set(&ns->set); |
| return false; |
| } |
| #endif |
| return true; |
| } |
| |
| void retire_userns_sysctls(struct user_namespace *ns) |
| { |
| #ifdef CONFIG_SYSCTL |
| struct ctl_table *tbl; |
| |
| tbl = ns->sysctls->ctl_table_arg; |
| unregister_sysctl_table(ns->sysctls); |
| retire_sysctl_set(&ns->set); |
| kfree(tbl); |
| #endif |
| } |
| |
| static struct ucounts *find_ucounts(struct user_namespace *ns, kuid_t uid, struct hlist_head *hashent) |
| { |
| struct ucounts *ucounts; |
| |
| hlist_for_each_entry(ucounts, hashent, node) { |
| if (uid_eq(ucounts->uid, uid) && (ucounts->ns == ns)) |
| return ucounts; |
| } |
| return NULL; |
| } |
| |
| static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid) |
| { |
| struct hlist_head *hashent = ucounts_hashentry(ns, uid); |
| struct ucounts *ucounts, *new; |
| |
| spin_lock_irq(&ucounts_lock); |
| ucounts = find_ucounts(ns, uid, hashent); |
| if (!ucounts) { |
| spin_unlock_irq(&ucounts_lock); |
| |
| new = kzalloc(sizeof(*new), GFP_KERNEL); |
| if (!new) |
| return NULL; |
| |
| new->ns = ns; |
| new->uid = uid; |
| atomic_set(&new->count, 0); |
| |
| spin_lock_irq(&ucounts_lock); |
| ucounts = find_ucounts(ns, uid, hashent); |
| if (ucounts) { |
| kfree(new); |
| } else { |
| hlist_add_head(&new->node, hashent); |
| ucounts = new; |
| } |
| } |
| if (!atomic_add_unless(&ucounts->count, 1, INT_MAX)) |
| ucounts = NULL; |
| spin_unlock_irq(&ucounts_lock); |
| return ucounts; |
| } |
| |
| static void put_ucounts(struct ucounts *ucounts) |
| { |
| unsigned long flags; |
| |
| if (atomic_dec_and_test(&ucounts->count)) { |
| spin_lock_irqsave(&ucounts_lock, flags); |
| hlist_del_init(&ucounts->node); |
| spin_unlock_irqrestore(&ucounts_lock, flags); |
| |
| kfree(ucounts); |
| } |
| } |
| |
| static inline bool atomic_inc_below(atomic_t *v, int u) |
| { |
| int c, old; |
| c = atomic_read(v); |
| for (;;) { |
| if (unlikely(c >= u)) |
| return false; |
| old = atomic_cmpxchg(v, c, c+1); |
| if (likely(old == c)) |
| return true; |
| c = old; |
| } |
| } |
| |
| struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid, |
| enum ucount_type type) |
| { |
| struct ucounts *ucounts, *iter, *bad; |
| struct user_namespace *tns; |
| ucounts = get_ucounts(ns, uid); |
| for (iter = ucounts; iter; iter = tns->ucounts) { |
| int max; |
| tns = iter->ns; |
| max = READ_ONCE(tns->ucount_max[type]); |
| if (!atomic_inc_below(&iter->ucount[type], max)) |
| goto fail; |
| } |
| return ucounts; |
| fail: |
| bad = iter; |
| for (iter = ucounts; iter != bad; iter = iter->ns->ucounts) |
| atomic_dec(&iter->ucount[type]); |
| |
| put_ucounts(ucounts); |
| return NULL; |
| } |
| |
| void dec_ucount(struct ucounts *ucounts, enum ucount_type type) |
| { |
| struct ucounts *iter; |
| for (iter = ucounts; iter; iter = iter->ns->ucounts) { |
| int dec = atomic_dec_if_positive(&iter->ucount[type]); |
| WARN_ON_ONCE(dec < 0); |
| } |
| put_ucounts(ucounts); |
| } |
| |
| static __init int user_namespace_sysctl_init(void) |
| { |
| #ifdef CONFIG_SYSCTL |
| static struct ctl_table_header *user_header; |
| static struct ctl_table empty[1]; |
| /* |
| * It is necessary to register the user directory in the |
| * default set so that registrations in the child sets work |
| * properly. |
| */ |
| user_header = register_sysctl("user", empty); |
| kmemleak_ignore(user_header); |
| BUG_ON(!user_header); |
| BUG_ON(!setup_userns_sysctls(&init_user_ns)); |
| #endif |
| return 0; |
| } |
| subsys_initcall(user_namespace_sysctl_init); |