/* * 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);} 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_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 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, "%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);} /* 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);	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; 	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){	/* restore back the count */	atomic_inc(&up->__count);	spin_unlock_irqrestore(&uidhash_lock, flags); 	INIT_WORK(&up->work, cleanup_user_struct);	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 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); }#elseint 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);