/* * 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>struct user_namespace init_user_ns = {	.kref = {		.refcount	= ATOMIC_INIT(2),	},	.root_user = &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);struct user_struct root_user = {	.__count	= ATOMIC_INIT(1),	.processes	= ATOMIC_INIT(1),	.files		= ATOMIC_INIT(0),	.sigpending	= ATOMIC_INIT(0),	.locked_shm     = 0,#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);}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;}#ifdef CONFIG_USER_SCHEDstatic 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;	return rc;}static void sched_switch_user(struct task_struct *p){	sched_move_task(p);}#else	/* CONFIG_USER_SCHED */static void sched_destroy_user(struct user_struct *up) { }static int sched_create_user(struct user_struct *up) { return 0; }static void sched_switch_user(struct task_struct *p) { }#endif	/* CONFIG_USER_SCHED */#if defined(CONFIG_USER_SCHED) && defined(CONFIG_SYSFS)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_SCHEDstatic 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_SCHEDstatic 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, "%lu\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, "%lu", &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 */static int uids_user_create(struct user_struct *up){	struct kobject *kobj = &up->kobj;	int error;	memset(kobj, 0, sizeof(struct kobject));	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);}/* work function to remove sysfs directory for a user and free up * corresponding structures. */static void remove_user_sysfs_dir(struct work_struct *w){	struct user_struct *up = container_of(w, struct user_struct, work);	unsigned long flags;	int remove_user = 0;	/* Make uid_hash_remove() + sysfs_remove_file() + kobject_del()	 * atomic.	 */	uids_mutex_lock();	local_irq_save(flags);	if (atomic_dec_and_lock(&up->__count, &uidhash_lock)) {		uid_hash_remove(up);		remove_user = 1;		spin_unlock_irqrestore(&uidhash_lock, flags);	} else {		local_irq_restore(flags);	}	if (!remove_user)		goto done;	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 inline void free_user(struct user_struct *up, unsigned long flags){	/* restore back the count */	atomic_inc(&up->__count);	spin_unlock_irqrestore(&uidhash_lock, flags);	INIT_WORK(&up->work, remove_user_sysfs_dir);	schedule_work(&up->work);}#else	/* CONFIG_USER_SCHED && CONFIG_SYSFS */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 inline 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/* * 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->nsproxy->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;		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);out_free_user:	kmem_cache_free(uid_cachep, new);out_unlock:	uids_mutex_unlock();	return NULL;}void switch_uid(struct user_struct *new_user){	struct user_struct *old_user;	/* What if a process setreuid()'s and this brings the	 * new uid over his NPROC rlimit?  We can check this now	 * cheaply with the new uid cache, so if it matters	 * we should be checking for it.  -DaveM	 */	old_user = current->user;	atomic_inc(&new_user->processes);	atomic_dec(&old_user->processes);	switch_uid_keyring(new_user);	current->user = new_user;	sched_switch_user(current);	/*	 * We need to synchronize with __sigqueue_alloc()	 * doing a get_uid(p->user).. If that saw the old	 * user value, we need to wait until it has exited	 * its critical region before we can free the old	 * structure.	 */	smp_mb();	spin_unlock_wait(&current->sighand->siglock);	free_uid(old_user);	suid_keys(current);}#ifdef CONFIG_USER_NSvoid release_uids(struct user_namespace *ns){	int i;	unsigned long flags;	struct hlist_head *head;	struct hlist_node *nd;	spin_lock_irqsave(&uidhash_lock, flags);	/*	 * collapse the chains so that the user_struct-s will	 * be still alive, but not in hashes. subsequent free_uid()	 * will free them.	 */	for (i = 0; i < UIDHASH_SZ; i++) {		head = ns->uidhash_table + i;		while (!hlist_empty(head)) {			nd = head->first;			hlist_del_init(nd);		}	}	spin_unlock_irqrestore(&uidhash_lock, flags);	free_uid(ns->root_user);}#endifstatic 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);