484 lines
11 KiB
C
484 lines
11 KiB
C
/*
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* The "user cache".
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*
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* (C) Copyright 1991-2000 Linus Torvalds
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*
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* We have a per-user structure to keep track of how many
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* processes, files etc the user has claimed, in order to be
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* able to have per-user limits for system resources.
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*/
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#include <linux/init.h>
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include <linux/bitops.h>
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#include <linux/key.h>
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#include <linux/interrupt.h>
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#include <linux/module.h>
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#include <linux/user_namespace.h>
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struct user_namespace init_user_ns = {
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.kref = {
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.refcount = ATOMIC_INIT(2),
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},
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.root_user = &root_user,
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};
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EXPORT_SYMBOL_GPL(init_user_ns);
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/*
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* UID task count cache, to get fast user lookup in "alloc_uid"
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* when changing user ID's (ie setuid() and friends).
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*/
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#define UIDHASH_MASK (UIDHASH_SZ - 1)
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#define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK)
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#define uidhashentry(ns, uid) ((ns)->uidhash_table + __uidhashfn((uid)))
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static struct kmem_cache *uid_cachep;
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/*
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* The uidhash_lock is mostly taken from process context, but it is
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* occasionally also taken from softirq/tasklet context, when
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* task-structs get RCU-freed. Hence all locking must be softirq-safe.
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* But free_uid() is also called with local interrupts disabled, and running
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* local_bh_enable() with local interrupts disabled is an error - we'll run
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* softirq callbacks, and they can unconditionally enable interrupts, and
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* the caller of free_uid() didn't expect that..
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*/
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static DEFINE_SPINLOCK(uidhash_lock);
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struct user_struct root_user = {
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.__count = ATOMIC_INIT(1),
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.processes = ATOMIC_INIT(1),
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.files = ATOMIC_INIT(0),
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.sigpending = ATOMIC_INIT(0),
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.locked_shm = 0,
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#ifdef CONFIG_KEYS
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.uid_keyring = &root_user_keyring,
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.session_keyring = &root_session_keyring,
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#endif
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#ifdef CONFIG_FAIR_USER_SCHED
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.tg = &init_task_group,
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#endif
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};
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/*
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* These routines must be called with the uidhash spinlock held!
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*/
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static void uid_hash_insert(struct user_struct *up, struct hlist_head *hashent)
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{
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hlist_add_head(&up->uidhash_node, hashent);
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}
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static void uid_hash_remove(struct user_struct *up)
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{
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hlist_del_init(&up->uidhash_node);
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}
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static struct user_struct *uid_hash_find(uid_t uid, struct hlist_head *hashent)
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{
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struct user_struct *user;
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struct hlist_node *h;
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hlist_for_each_entry(user, h, hashent, uidhash_node) {
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if (user->uid == uid) {
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atomic_inc(&user->__count);
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return user;
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}
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}
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return NULL;
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}
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#ifdef CONFIG_FAIR_USER_SCHED
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static void sched_destroy_user(struct user_struct *up)
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{
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sched_destroy_group(up->tg);
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}
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static int sched_create_user(struct user_struct *up)
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{
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int rc = 0;
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up->tg = sched_create_group();
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if (IS_ERR(up->tg))
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rc = -ENOMEM;
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return rc;
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}
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static void sched_switch_user(struct task_struct *p)
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{
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sched_move_task(p);
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}
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#else /* CONFIG_FAIR_USER_SCHED */
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static void sched_destroy_user(struct user_struct *up) { }
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static int sched_create_user(struct user_struct *up) { return 0; }
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static void sched_switch_user(struct task_struct *p) { }
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#endif /* CONFIG_FAIR_USER_SCHED */
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#if defined(CONFIG_FAIR_USER_SCHED) && defined(CONFIG_SYSFS)
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static struct kset *uids_kset; /* represents the /sys/kernel/uids/ directory */
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static DEFINE_MUTEX(uids_mutex);
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static inline void uids_mutex_lock(void)
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{
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mutex_lock(&uids_mutex);
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}
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static inline void uids_mutex_unlock(void)
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{
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mutex_unlock(&uids_mutex);
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}
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/* uid directory attributes */
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static ssize_t cpu_shares_show(struct kobject *kobj,
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struct kobj_attribute *attr,
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char *buf)
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{
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struct user_struct *up = container_of(kobj, struct user_struct, kobj);
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return sprintf(buf, "%lu\n", sched_group_shares(up->tg));
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}
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static ssize_t cpu_shares_store(struct kobject *kobj,
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struct kobj_attribute *attr,
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const char *buf, size_t size)
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{
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struct user_struct *up = container_of(kobj, struct user_struct, kobj);
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unsigned long shares;
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int rc;
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sscanf(buf, "%lu", &shares);
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rc = sched_group_set_shares(up->tg, shares);
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return (rc ? rc : size);
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}
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static struct kobj_attribute cpu_share_attr =
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__ATTR(cpu_share, 0644, cpu_shares_show, cpu_shares_store);
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/* default attributes per uid directory */
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static struct attribute *uids_attributes[] = {
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&cpu_share_attr.attr,
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NULL
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};
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/* the lifetime of user_struct is not managed by the core (now) */
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static void uids_release(struct kobject *kobj)
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{
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return;
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}
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static struct kobj_type uids_ktype = {
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.sysfs_ops = &kobj_sysfs_ops,
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.default_attrs = uids_attributes,
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.release = uids_release,
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};
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/* create /sys/kernel/uids/<uid>/cpu_share file for this user */
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static int uids_user_create(struct user_struct *up)
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{
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struct kobject *kobj = &up->kobj;
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int error;
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memset(kobj, 0, sizeof(struct kobject));
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kobj->kset = uids_kset;
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error = kobject_init_and_add(kobj, &uids_ktype, NULL, "%d", up->uid);
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if (error) {
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kobject_put(kobj);
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goto done;
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}
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kobject_uevent(kobj, KOBJ_ADD);
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done:
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return error;
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}
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/* create these entries in sysfs:
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* "/sys/kernel/uids" directory
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* "/sys/kernel/uids/0" directory (for root user)
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* "/sys/kernel/uids/0/cpu_share" file (for root user)
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*/
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int __init uids_sysfs_init(void)
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{
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uids_kset = kset_create_and_add("uids", NULL, kernel_kobj);
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if (!uids_kset)
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return -ENOMEM;
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return uids_user_create(&root_user);
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}
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/* work function to remove sysfs directory for a user and free up
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* corresponding structures.
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*/
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static void remove_user_sysfs_dir(struct work_struct *w)
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{
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struct user_struct *up = container_of(w, struct user_struct, work);
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unsigned long flags;
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int remove_user = 0;
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/* Make uid_hash_remove() + sysfs_remove_file() + kobject_del()
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* atomic.
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*/
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uids_mutex_lock();
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local_irq_save(flags);
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if (atomic_dec_and_lock(&up->__count, &uidhash_lock)) {
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uid_hash_remove(up);
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remove_user = 1;
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spin_unlock_irqrestore(&uidhash_lock, flags);
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} else {
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local_irq_restore(flags);
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}
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if (!remove_user)
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goto done;
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kobject_uevent(&up->kobj, KOBJ_REMOVE);
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kobject_del(&up->kobj);
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kobject_put(&up->kobj);
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sched_destroy_user(up);
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key_put(up->uid_keyring);
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key_put(up->session_keyring);
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kmem_cache_free(uid_cachep, up);
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done:
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uids_mutex_unlock();
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}
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/* IRQs are disabled and uidhash_lock is held upon function entry.
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* IRQ state (as stored in flags) is restored and uidhash_lock released
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* upon function exit.
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*/
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static inline void free_user(struct user_struct *up, unsigned long flags)
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{
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/* restore back the count */
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atomic_inc(&up->__count);
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spin_unlock_irqrestore(&uidhash_lock, flags);
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INIT_WORK(&up->work, remove_user_sysfs_dir);
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schedule_work(&up->work);
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}
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#else /* CONFIG_FAIR_USER_SCHED && CONFIG_SYSFS */
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int uids_sysfs_init(void) { return 0; }
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static inline int uids_user_create(struct user_struct *up) { return 0; }
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static inline void uids_mutex_lock(void) { }
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static inline void uids_mutex_unlock(void) { }
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/* IRQs are disabled and uidhash_lock is held upon function entry.
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* IRQ state (as stored in flags) is restored and uidhash_lock released
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* upon function exit.
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*/
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static inline void free_user(struct user_struct *up, unsigned long flags)
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{
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uid_hash_remove(up);
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spin_unlock_irqrestore(&uidhash_lock, flags);
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sched_destroy_user(up);
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key_put(up->uid_keyring);
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key_put(up->session_keyring);
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kmem_cache_free(uid_cachep, up);
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}
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#endif
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/*
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* Locate the user_struct for the passed UID. If found, take a ref on it. The
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* caller must undo that ref with free_uid().
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*
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* If the user_struct could not be found, return NULL.
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*/
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struct user_struct *find_user(uid_t uid)
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{
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struct user_struct *ret;
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unsigned long flags;
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struct user_namespace *ns = current->nsproxy->user_ns;
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spin_lock_irqsave(&uidhash_lock, flags);
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ret = uid_hash_find(uid, uidhashentry(ns, uid));
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spin_unlock_irqrestore(&uidhash_lock, flags);
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return ret;
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}
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void free_uid(struct user_struct *up)
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{
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unsigned long flags;
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if (!up)
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return;
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local_irq_save(flags);
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if (atomic_dec_and_lock(&up->__count, &uidhash_lock))
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free_user(up, flags);
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else
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local_irq_restore(flags);
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}
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struct user_struct * alloc_uid(struct user_namespace *ns, uid_t uid)
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{
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struct hlist_head *hashent = uidhashentry(ns, uid);
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struct user_struct *up, *new;
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/* Make uid_hash_find() + uids_user_create() + uid_hash_insert()
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* atomic.
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*/
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uids_mutex_lock();
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spin_lock_irq(&uidhash_lock);
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up = uid_hash_find(uid, hashent);
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spin_unlock_irq(&uidhash_lock);
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if (!up) {
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new = kmem_cache_alloc(uid_cachep, GFP_KERNEL);
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if (!new)
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goto out_unlock;
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new->uid = uid;
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atomic_set(&new->__count, 1);
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atomic_set(&new->processes, 0);
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atomic_set(&new->files, 0);
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atomic_set(&new->sigpending, 0);
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#ifdef CONFIG_INOTIFY_USER
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atomic_set(&new->inotify_watches, 0);
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atomic_set(&new->inotify_devs, 0);
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#endif
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#ifdef CONFIG_POSIX_MQUEUE
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new->mq_bytes = 0;
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#endif
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new->locked_shm = 0;
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if (alloc_uid_keyring(new, current) < 0)
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goto out_free_user;
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if (sched_create_user(new) < 0)
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goto out_put_keys;
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if (uids_user_create(new))
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goto out_destoy_sched;
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/*
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* Before adding this, check whether we raced
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* on adding the same user already..
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*/
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spin_lock_irq(&uidhash_lock);
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up = uid_hash_find(uid, hashent);
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if (up) {
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/* This case is not possible when CONFIG_FAIR_USER_SCHED
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* is defined, since we serialize alloc_uid() using
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* uids_mutex. Hence no need to call
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* sched_destroy_user() or remove_user_sysfs_dir().
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*/
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key_put(new->uid_keyring);
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key_put(new->session_keyring);
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kmem_cache_free(uid_cachep, new);
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} else {
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uid_hash_insert(new, hashent);
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up = new;
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}
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spin_unlock_irq(&uidhash_lock);
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}
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uids_mutex_unlock();
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return up;
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out_destoy_sched:
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sched_destroy_user(new);
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out_put_keys:
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key_put(new->uid_keyring);
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key_put(new->session_keyring);
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out_free_user:
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kmem_cache_free(uid_cachep, new);
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out_unlock:
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uids_mutex_unlock();
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return NULL;
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}
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void switch_uid(struct user_struct *new_user)
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{
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struct user_struct *old_user;
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/* What if a process setreuid()'s and this brings the
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* new uid over his NPROC rlimit? We can check this now
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* cheaply with the new uid cache, so if it matters
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* we should be checking for it. -DaveM
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*/
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old_user = current->user;
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atomic_inc(&new_user->processes);
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atomic_dec(&old_user->processes);
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switch_uid_keyring(new_user);
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current->user = new_user;
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sched_switch_user(current);
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/*
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* We need to synchronize with __sigqueue_alloc()
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* doing a get_uid(p->user).. If that saw the old
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* user value, we need to wait until it has exited
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* its critical region before we can free the old
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* structure.
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*/
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smp_mb();
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spin_unlock_wait(¤t->sighand->siglock);
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free_uid(old_user);
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suid_keys(current);
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}
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#ifdef CONFIG_USER_NS
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void release_uids(struct user_namespace *ns)
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{
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int i;
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unsigned long flags;
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struct hlist_head *head;
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struct hlist_node *nd;
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spin_lock_irqsave(&uidhash_lock, flags);
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/*
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* collapse the chains so that the user_struct-s will
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* be still alive, but not in hashes. subsequent free_uid()
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* will free them.
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*/
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for (i = 0; i < UIDHASH_SZ; i++) {
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head = ns->uidhash_table + i;
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while (!hlist_empty(head)) {
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nd = head->first;
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hlist_del_init(nd);
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}
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}
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spin_unlock_irqrestore(&uidhash_lock, flags);
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free_uid(ns->root_user);
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}
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#endif
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static int __init uid_cache_init(void)
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{
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int n;
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uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct),
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0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
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for(n = 0; n < UIDHASH_SZ; ++n)
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INIT_HLIST_HEAD(init_user_ns.uidhash_table + n);
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/* Insert the root user immediately (init already runs as root) */
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spin_lock_irq(&uidhash_lock);
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uid_hash_insert(&root_user, uidhashentry(&init_user_ns, 0));
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spin_unlock_irq(&uidhash_lock);
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return 0;
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}
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module_init(uid_cache_init);
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