378 lines
9.1 KiB
C
378 lines
9.1 KiB
C
// 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,
|
|
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 + 1);
|
|
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
|
|
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);
|