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/*
* The "user cache".
*
* (C) Copyright 1991-2000 Linus Torvalds
*
* We have a per-user structure to keep track of how many
* processes, files etc the user has claimed, in order to be
* able to have per-user limits for system resources.
*/
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/bitops.h>
#include <linux/key.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/user_namespace.h>
#include "cred-internals.h"
struct user_namespace init_user_ns = {
.kref = {
.refcount = ATOMIC_INIT(2),
},
.creator = &root_user,
};
EXPORT_SYMBOL_GPL(init_user_ns);
/*
* UID task count cache, to get fast user lookup in "alloc_uid"
* when changing user ID's (ie setuid() and friends).
*/
#define UIDHASH_MASK (UIDHASH_SZ - 1)
#define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK)
#define uidhashentry(ns, uid) ((ns)->uidhash_table + __uidhashfn((uid)))
static struct kmem_cache *uid_cachep;
/*
* The uidhash_lock is mostly taken from process context, but it is
* occasionally also taken from softirq/tasklet context, when
* task-structs get RCU-freed. Hence all locking must be softirq-safe.
* But free_uid() is also called with local interrupts disabled, and running
* local_bh_enable() with local interrupts disabled is an error - we'll run
* softirq callbacks, and they can unconditionally enable interrupts, and
* the caller of free_uid() didn't expect that..
*/
static DEFINE_SPINLOCK(uidhash_lock);
/* root_user.__count is 2, 1 for init task cred, 1 for init_user_ns->creator */
struct user_struct root_user = {
.__count = ATOMIC_INIT(2),
.processes = ATOMIC_INIT(1),
.files = ATOMIC_INIT(0),
.sigpending = ATOMIC_INIT(0),
.locked_shm = 0,
.user_ns = &init_user_ns,
#ifdef CONFIG_USER_SCHED
.tg = &init_task_group,
#endif
};
/*
* These routines must be called with the uidhash spinlock held!
*/
static void uid_hash_insert(struct user_struct *up, struct hlist_head *hashent)
{
hlist_add_head(&up->uidhash_node, hashent);
}
static void uid_hash_remove(struct user_struct *up)
{
hlist_del_init(&up->uidhash_node);
put_user_ns(up->user_ns);
}
#ifdef CONFIG_USER_SCHED
static void sched_destroy_user(struct user_struct *up)
{
sched_destroy_group(up->tg);
}
static int sched_create_user(struct user_struct *up)
{
int rc = 0;
up->tg = sched_create_group(&root_task_group);
if (IS_ERR(up->tg))
rc = -ENOMEM;
set_tg_uid(up);
return rc;
}
#else /* CONFIG_USER_SCHED */
static void sched_destroy_user(struct user_struct *up) { }
static int sched_create_user(struct user_struct *up) { return 0; }
#endif /* CONFIG_USER_SCHED */
#if defined(CONFIG_USER_SCHED) && defined(CONFIG_SYSFS)
static struct user_struct *uid_hash_find(uid_t uid, struct hlist_head *hashent)
{
struct user_struct *user;
struct hlist_node *h;
hlist_for_each_entry(user, h, hashent, uidhash_node) {
if (user->uid == uid) {
/* possibly resurrect an "almost deleted" object */
if (atomic_inc_return(&user->__count) == 1)
cancel_delayed_work(&user->work);
return user;
}
}
return NULL;
}
static struct kset *uids_kset; /* represents the /sys/kernel/uids/ directory */
static DEFINE_MUTEX(uids_mutex);
static inline void uids_mutex_lock(void)
{
mutex_lock(&uids_mutex);
}
static inline void uids_mutex_unlock(void)
{
mutex_unlock(&uids_mutex);
}
/* uid directory attributes */
#ifdef CONFIG_FAIR_GROUP_SCHED
static ssize_t cpu_shares_show(struct kobject *kobj,
struct kobj_attribute *attr,
char *buf)
{
struct user_struct *up = container_of(kobj, struct user_struct, kobj);
return sprintf(buf, "%lu\n", sched_group_shares(up->tg));
}
static ssize_t cpu_shares_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t size)
{
struct user_struct *up = container_of(kobj, struct user_struct, kobj);
unsigned long shares;
int rc;
sscanf(buf, "%lu", &shares);
rc = sched_group_set_shares(up->tg, shares);
return (rc ? rc : size);
}
static struct kobj_attribute cpu_share_attr =
__ATTR(cpu_share, 0644, cpu_shares_show, cpu_shares_store);
#endif
#ifdef CONFIG_RT_GROUP_SCHED
static ssize_t cpu_rt_runtime_show(struct kobject *kobj,
struct kobj_attribute *attr,
char *buf)
{
struct user_struct *up = container_of(kobj, struct user_struct, kobj);
return sprintf(buf, "%ld\n", sched_group_rt_runtime(up->tg));
}
static ssize_t cpu_rt_runtime_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t size)
{
struct user_struct *up = container_of(kobj, struct user_struct, kobj);
unsigned long rt_runtime;
int rc;
sscanf(buf, "%ld", &rt_runtime);
rc = sched_group_set_rt_runtime(up->tg, rt_runtime);
return (rc ? rc : size);
}
static struct kobj_attribute cpu_rt_runtime_attr =
__ATTR(cpu_rt_runtime, 0644, cpu_rt_runtime_show, cpu_rt_runtime_store);
static ssize_t cpu_rt_period_show(struct kobject *kobj,
struct kobj_attribute *attr,
char *buf)
{
struct user_struct *up = container_of(kobj, struct user_struct, kobj);
return sprintf(buf, "%lu\n", sched_group_rt_period(up->tg));
}
static ssize_t cpu_rt_period_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t size)
{
struct user_struct *up = container_of(kobj, struct user_struct, kobj);
unsigned long rt_period;
int rc;
sscanf(buf, "%lu", &rt_period);
rc = sched_group_set_rt_period(up->tg, rt_period);
return (rc ? rc : size);
}
static struct kobj_attribute cpu_rt_period_attr =
__ATTR(cpu_rt_period, 0644, cpu_rt_period_show, cpu_rt_period_store);
#endif
/* default attributes per uid directory */
static struct attribute *uids_attributes[] = {
#ifdef CONFIG_FAIR_GROUP_SCHED
&cpu_share_attr.attr,
#endif
#ifdef CONFIG_RT_GROUP_SCHED
&cpu_rt_runtime_attr.attr,
&cpu_rt_period_attr.attr,
#endif
NULL
};
/* the lifetime of user_struct is not managed by the core (now) */
static void uids_release(struct kobject *kobj)
{
return;
}
static struct kobj_type uids_ktype = {
.sysfs_ops = &kobj_sysfs_ops,
.default_attrs = uids_attributes,
.release = uids_release,
};
/*
* Create /sys/kernel/uids/<uid>/cpu_share file for this user
* We do not create this file for users in a user namespace (until
* sysfs tagging is implemented).
*
* See Documentation/scheduler/sched-design-CFS.txt for ramifications.
*/
static int uids_user_create(struct user_struct *up)
{
struct kobject *kobj = &up->kobj;
int error;
memset(kobj, 0, sizeof(struct kobject));
if (up->user_ns != &init_user_ns)
return 0;
kobj->kset = uids_kset;
error = kobject_init_and_add(kobj, &uids_ktype, NULL, "%d", up->uid);
if (error) {
kobject_put(kobj);
goto done;
}
kobject_uevent(kobj, KOBJ_ADD);
done:
return error;
}
/* create these entries in sysfs:
* "/sys/kernel/uids" directory
* "/sys/kernel/uids/0" directory (for root user)
* "/sys/kernel/uids/0/cpu_share" file (for root user)
*/
int __init uids_sysfs_init(void)
{
uids_kset = kset_create_and_add("uids", NULL, kernel_kobj);
if (!uids_kset)
return -ENOMEM;
return uids_user_create(&root_user);
}
/* delayed work function to remove sysfs directory for a user and free up
* corresponding structures.
*/
static void cleanup_user_struct(struct work_struct *w)
{
struct user_struct *up = container_of(w, struct user_struct, work.work);
unsigned long flags;
int remove_user = 0;
/* Make uid_hash_remove() + sysfs_remove_file() + kobject_del()
* atomic.
*/
uids_mutex_lock();
spin_lock_irqsave(&uidhash_lock, flags);
if (atomic_read(&up->__count) == 0) {
uid_hash_remove(up);
remove_user = 1;
}
spin_unlock_irqrestore(&uidhash_lock, flags);
if (!remove_user)
goto done;
if (up->user_ns == &init_user_ns) {
kobject_uevent(&up->kobj, KOBJ_REMOVE);
kobject_del(&up->kobj);
kobject_put(&up->kobj);
}
sched_destroy_user(up);
key_put(up->uid_keyring);
key_put(up->session_keyring);
kmem_cache_free(uid_cachep, up);
done:
uids_mutex_unlock();
}
/* IRQs are disabled and uidhash_lock is held upon function entry.
* IRQ state (as stored in flags) is restored and uidhash_lock released
* upon function exit.
*/
static void free_user(struct user_struct *up, unsigned long flags)
{
spin_unlock_irqrestore(&uidhash_lock, flags);
INIT_DELAYED_WORK(&up->work, cleanup_user_struct);
schedule_delayed_work(&up->work, msecs_to_jiffies(1000));
}
#else /* CONFIG_USER_SCHED && CONFIG_SYSFS */
static struct user_struct *uid_hash_find(uid_t uid, struct hlist_head *hashent)
{
struct user_struct *user;
struct hlist_node *h;
hlist_for_each_entry(user, h, hashent, uidhash_node) {
if (user->uid == uid) {
atomic_inc(&user->__count);
return user;
}
}
return NULL;
}
int uids_sysfs_init(void) { return 0; }
static inline int uids_user_create(struct user_struct *up) { return 0; }
static inline void uids_mutex_lock(void) { }
static inline void uids_mutex_unlock(void) { }
/* IRQs are disabled and uidhash_lock is held upon function entry.
* IRQ state (as stored in flags) is restored and uidhash_lock released
* upon function exit.
*/
static void free_user(struct user_struct *up, unsigned long flags)
{
uid_hash_remove(up);
spin_unlock_irqrestore(&uidhash_lock, flags);
sched_destroy_user(up);
key_put(up->uid_keyring);
key_put(up->session_keyring);
kmem_cache_free(uid_cachep, up);
}
#endif
#if defined(CONFIG_RT_GROUP_SCHED) && defined(CONFIG_USER_SCHED)
/*
* We need to check if a setuid can take place. This function should be called
* before successfully completing the setuid.
*/
int task_can_switch_user(struct user_struct *up, struct task_struct *tsk)
{
return sched_rt_can_attach(up->tg, tsk);
}
#else
int task_can_switch_user(struct user_struct *up, struct task_struct *tsk)
{
return 1;
}
#endif
/*
* Locate the user_struct for the passed UID. If found, take a ref on it. The
* caller must undo that ref with free_uid().
*
* If the user_struct could not be found, return NULL.
*/
struct user_struct *find_user(uid_t uid)
{
struct user_struct *ret;
unsigned long flags;
struct user_namespace *ns = current_user_ns();
spin_lock_irqsave(&uidhash_lock, flags);
ret = uid_hash_find(uid, uidhashentry(ns, uid));
spin_unlock_irqrestore(&uidhash_lock, flags);
return ret;
}
void free_uid(struct user_struct *up)
{
unsigned long flags;
if (!up)
return;
local_irq_save(flags);
if (atomic_dec_and_lock(&up->__count, &uidhash_lock))
free_user(up, flags);
else
local_irq_restore(flags);
}
struct user_struct *alloc_uid(struct user_namespace *ns, uid_t uid)
{
struct hlist_head *hashent = uidhashentry(ns, uid);
struct user_struct *up, *new;
/* Make uid_hash_find() + uids_user_create() + uid_hash_insert()
* atomic.
*/
uids_mutex_lock();
spin_lock_irq(&uidhash_lock);
up = uid_hash_find(uid, hashent);
spin_unlock_irq(&uidhash_lock);
if (!up) {
new = kmem_cache_zalloc(uid_cachep, GFP_KERNEL);
if (!new)
goto out_unlock;
new->uid = uid;
atomic_set(&new->__count, 1);
if (sched_create_user(new) < 0)
goto out_free_user;
new->user_ns = get_user_ns(ns);
if (uids_user_create(new))
goto out_destoy_sched;
/*
* Before adding this, check whether we raced
* on adding the same user already..
*/
spin_lock_irq(&uidhash_lock);
up = uid_hash_find(uid, hashent);
if (up) {
/* This case is not possible when CONFIG_USER_SCHED
* is defined, since we serialize alloc_uid() using
* uids_mutex. Hence no need to call
* sched_destroy_user() or remove_user_sysfs_dir().
*/
key_put(new->uid_keyring);
key_put(new->session_keyring);
kmem_cache_free(uid_cachep, new);
} else {
uid_hash_insert(new, hashent);
up = new;
}
spin_unlock_irq(&uidhash_lock);
}
uids_mutex_unlock();
return up;
out_destoy_sched:
sched_destroy_user(new);
put_user_ns(new->user_ns);
out_free_user:
kmem_cache_free(uid_cachep, new);
out_unlock:
uids_mutex_unlock();
return NULL;
}
static int __init uid_cache_init(void)
{
int n;
uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct),
0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
for(n = 0; n < UIDHASH_SZ; ++n)
INIT_HLIST_HEAD(init_user_ns.uidhash_table + n);
/* Insert the root user immediately (init already runs as root) */
spin_lock_irq(&uidhash_lock);
uid_hash_insert(&root_user, uidhashentry(&init_user_ns, 0));
spin_unlock_irq(&uidhash_lock);
return 0;
}
module_init(uid_cache_init);
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