/*
   * 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
  ", 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
  ", 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
  ", 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)

  {

  	INIT_DELAYED_WORK(&up->work, cleanup_user_struct);
  	schedule_delayed_work(&up->work, msecs_to_jiffies(1000));

  	spin_unlock_irqrestore(&uidhash_lock, flags);

  }

  #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);