// SPDX-License-Identifier: GPL-2.0-only
#include <linux/stat.h>
#include <linux/sysctl.h>
#include <linux/slab.h>
#include <linux/cred.h>
#include <linux/hash.h>
#include <linux/kmemleak.h>
#include <linux/user_namespace.h>
struct ucounts init_ucounts = {
.ns = &init_user_ns,
.uid = GLOBAL_ROOT_UID,
.count = ATOMIC_INIT(1),
};
#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,
const 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 long ue_zero = 0;
static long ue_int_max = INT_MAX;
#define UCOUNT_ENTRY(name) \
{ \
.procname = name, \
.maxlen = sizeof(long), \
.mode = 0644, \
.proc_handler = proc_doulongvec_minmax, \
.extra1 = &ue_zero, \
.extra2 = &ue_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"),
UCOUNT_ENTRY("max_time_namespaces"),
#ifdef CONFIG_INOTIFY_USER
UCOUNT_ENTRY("max_inotify_instances"),
UCOUNT_ENTRY("max_inotify_watches"),
#endif
#ifdef CONFIG_FANOTIFY
UCOUNT_ENTRY("max_fanotify_groups"),
UCOUNT_ENTRY("max_fanotify_marks"),
#endif
};
#endif /* CONFIG_SYSCTL */
bool setup_userns_sysctls(struct user_namespace *ns)
{
#ifdef CONFIG_SYSCTL
struct ctl_table *tbl;
BUILD_BUG_ON(ARRAY_SIZE(user_table) != UCOUNT_COUNTS);
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,
ARRAY_SIZE(user_table));
}
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
const 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 void hlist_add_ucounts(struct ucounts *ucounts)
{
struct hlist_head *hashent = ucounts_hashentry(ucounts->ns, ucounts->uid);
spin_lock_irq(&ucounts_lock);
hlist_add_head(&ucounts->node, hashent);
spin_unlock_irq(&ucounts_lock);
}
static inline bool get_ucounts_or_wrap(struct ucounts *ucounts)
{
/* Returns true on a successful get, false if the count wraps. */
return !atomic_add_negative(1, &ucounts->count);
}
struct ucounts *get_ucounts(struct ucounts *ucounts)
{
if (!get_ucounts_or_wrap(ucounts)) {
put_ucounts(ucounts);
ucounts = NULL;
}
return ucounts;
}
struct ucounts *alloc_ucounts(struct user_namespace *ns, kuid_t uid)
{
struct hlist_head *hashent = ucounts_hashentry(ns, uid);
struct ucounts *ucounts, *new;
bool wrapped;
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, 1);
spin_lock_irq(&ucounts_lock);
ucounts = find_ucounts(ns, uid, hashent);
if (ucounts) {
kfree(new);
} else {
hlist_add_head(&new->node, hashent);
get_user_ns(new->ns);
spin_unlock_irq(&ucounts_lock);
return new;
}
}
wrapped = !get_ucounts_or_wrap(ucounts);
spin_unlock_irq(&ucounts_lock);
if (wrapped) {
put_ucounts(ucounts);
return NULL;
}
return ucounts;
}
void put_ucounts(struct ucounts *ucounts)
{
unsigned long flags;
if (atomic_dec_and_lock_irqsave(&ucounts->count, &ucounts_lock, flags)) {
hlist_del_init(&ucounts->node);
spin_unlock_irqrestore(&ucounts_lock, flags);
put_user_ns(ucounts->ns);
kfree(ucounts);
}
}
static inline bool atomic_long_inc_below(atomic_long_t *v, int u)
{
long c, old;
c = atomic_long_read(v);
for (;;) {
if (unlikely(c >= u))
return false;
old = atomic_long_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 = alloc_ucounts(ns, uid);
for (iter = ucounts; iter; iter = tns->ucounts) {
long max;
tns = iter->ns;
max = READ_ONCE(tns->ucount_max[type]);
if (!atomic_long_inc_below(&iter->ucount[type], max))
goto fail;
}
return ucounts;
fail:
bad = iter;
for (iter = ucounts; iter != bad; iter = iter->ns->ucounts)
atomic_long_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) {
long dec = atomic_long_dec_if_positive(&iter->ucount[type]);
WARN_ON_ONCE(dec < 0);
}
put_ucounts(ucounts);
}
long inc_rlimit_ucounts(struct ucounts *ucounts, enum rlimit_type type, long v)
{
struct ucounts *iter;
long max = LONG_MAX;
long ret = 0;
for (iter = ucounts; iter; iter = iter->ns->ucounts) {
long new = atomic_long_add_return(v, &iter->rlimit[type]);
if (new < 0 || new > max)
ret = LONG_MAX;
else if (iter == ucounts)
ret = new;
max = get_userns_rlimit_max(iter->ns, type);
}
return ret;
}
bool dec_rlimit_ucounts(struct ucounts *ucounts, enum rlimit_type type, long v)
{
struct ucounts *iter;
long new = -1; /* Silence compiler warning */
for (iter = ucounts; iter; iter = iter->ns->ucounts) {
long dec = atomic_long_sub_return(v, &iter->rlimit[type]);
WARN_ON_ONCE(dec < 0);
if (iter == ucounts)
new = dec;
}
return (new == 0);
}
static void do_dec_rlimit_put_ucounts(struct ucounts *ucounts,
struct ucounts *last, enum rlimit_type type)
{
struct ucounts *iter, *next;
for (iter = ucounts; iter != last; iter = next) {
long dec = atomic_long_sub_return(1, &iter->rlimit[type]);
WARN_ON_ONCE(dec < 0);
next = iter->ns->ucounts;
if (dec == 0)
put_ucounts(iter);
}
}
void dec_rlimit_put_ucounts(struct ucounts *ucounts, enum rlimit_type type)
{
do_dec_rlimit_put_ucounts(ucounts, NULL, type);
}
long inc_rlimit_get_ucounts(struct ucounts *ucounts, enum rlimit_type type)
{
/* Caller must hold a reference to ucounts */
struct ucounts *iter;
long max = LONG_MAX;
long dec, ret = 0;
for (iter = ucounts; iter; iter = iter->ns->ucounts) {
long new = atomic_long_add_return(1, &iter->rlimit[type]);
if (new < 0 || new > max)
goto unwind;
if (iter == ucounts)
ret = new;
max = get_userns_rlimit_max(iter->ns, type);
/*
* Grab an extra ucount reference for the caller when
* the rlimit count was previously 0.
*/
if (new != 1)
continue;
if (!get_ucounts(iter))
goto dec_unwind;
}
return ret;
dec_unwind:
dec = atomic_long_sub_return(1, &iter->rlimit[type]);
WARN_ON_ONCE(dec < 0);
unwind:
do_dec_rlimit_put_ucounts(ucounts, iter, type);
return 0;
}
bool is_rlimit_overlimit(struct ucounts *ucounts, enum rlimit_type type, unsigned long rlimit)
{
struct ucounts *iter;
long max = rlimit;
if (rlimit > LONG_MAX)
max = LONG_MAX;
for (iter = ucounts; iter; iter = iter->ns->ucounts) {
long val = get_rlimit_value(iter, type);
if (val < 0 || val > max)
return true;
max = get_userns_rlimit_max(iter->ns, type);
}
return false;
}
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_sz("user", empty, 0);
kmemleak_ignore(user_header);
BUG_ON(!user_header);
BUG_ON(!setup_userns_sysctls(&init_user_ns));
#endif
hlist_add_ucounts(&init_ucounts);
inc_rlimit_ucounts(&init_ucounts, UCOUNT_RLIMIT_NPROC, 1);
return 0;
}
subsys_initcall(user_namespace_sysctl_init);
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