/* * 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> /* * 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_KEYS	.uid_keyring	= &root_user_keyring,	.session_keyring = &root_session_keyring,#endif#ifdef CONFIG_FAIR_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_FAIR_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();	if (IS_ERR(up->tg))		rc = -ENOMEM; 	return rc;} static void sched_switch_user(struct task_struct *p){	sched_move_task(p);} #else	/* CONFIG_FAIR_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_FAIR_USER_SCHED */ #if defined(CONFIG_FAIR_USER_SCHED) && defined(CONFIG_SYSFS) static struct kobject uids_kobject; /* represents /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);} /* return cpu shares held by the user */static ssize_t cpu_shares_show(struct kset *kset, char *buffer){	struct user_struct *up = container_of(kset, struct user_struct, kset); 	return sprintf(buffer, "%lu\n", sched_group_shares(up->tg));} /* modify cpu shares held by the user */static ssize_t cpu_shares_store(struct kset *kset, const char *buffer,				size_t size){	struct user_struct *up = container_of(kset, struct user_struct, kset);	unsigned long shares;	int rc; 	sscanf(buffer, "%lu", &shares); 	rc = sched_group_set_shares(up->tg, shares); 	return (rc ? rc : size);} static void user_attr_init(struct subsys_attribute *sa, char *name, int mode){	sa->attr.name = name;	sa->attr.mode = mode;	sa->show = cpu_shares_show;	sa->store = cpu_shares_store;} /* Create "/sys/kernel/uids/<uid>" directory and *  "/sys/kernel/uids/<uid>/cpu_share" file for this user. */static int user_kobject_create(struct user_struct *up){	struct kset *kset = &up->kset;	struct kobject *kobj = &kset->kobj;	int error; 	memset(kset, 0, sizeof(struct kset));	kobj->parent = &uids_kobject;	/* create under /sys/kernel/uids dir */	kobject_set_name(kobj, "%d", up->uid);	kset_init(kset);	user_attr_init(&up->user_attr, "cpu_share", 0644); 	error = kobject_add(kobj);	if (error)		goto done; 	error = sysfs_create_file(kobj, &up->user_attr.attr);	if (error)		kobject_del(kobj); 	kobject_uevent(kobj, KOBJ_ADD); done:	return error;} /* create these in sysfs filesystem: * 	"/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_kobject_init(void){	int error; 	/* create under /sys/kernel dir */	uids_kobject.parent = &kernel_subsys.kobj;	uids_kobject.kset = &kernel_subsys;	kobject_set_name(&uids_kobject, "uids");	kobject_init(&uids_kobject); 	error = kobject_add(&uids_kobject);	if (!error)		error = user_kobject_create(&root_user); 	return error;} /* 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);	struct kobject *kobj = &up->kset.kobj;	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; 	sysfs_remove_file(kobj, &up->user_attr.attr);	kobject_uevent(kobj, KOBJ_REMOVE);	kobject_del(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_FAIR_USER_SCHED && CONFIG_SYSFS */ static inline int user_kobject_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; 	/* Make uid_hash_find() + user_kobject_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) {		struct user_struct *new; 		new = kmem_cache_alloc(uid_cachep, GFP_KERNEL);		if (!new) {			uids_mutex_unlock();			return NULL;		} 		new->uid = uid;		atomic_set(&new->__count, 1);		atomic_set(&new->processes, 0);		atomic_set(&new->files, 0);		atomic_set(&new->sigpending, 0);#ifdef CONFIG_INOTIFY_USER		atomic_set(&new->inotify_watches, 0);		atomic_set(&new->inotify_devs, 0);#endif#ifdef CONFIG_POSIX_MQUEUE		new->mq_bytes = 0;#endif		new->locked_shm = 0; 		if (alloc_uid_keyring(new, current) < 0) {			kmem_cache_free(uid_cachep, new);			uids_mutex_unlock();			return NULL;		} 		if (sched_create_user(new) < 0) {			key_put(new->uid_keyring);			key_put(new->session_keyring);			kmem_cache_free(uid_cachep, new);			uids_mutex_unlock();			return NULL;		} 		if (user_kobject_create(new)) {			sched_destroy_user(new);			key_put(new->uid_keyring);			key_put(new->session_keyring);			kmem_cache_free(uid_cachep, new);			uids_mutex_unlock();			return NULL;		} 		/*		 * 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_FAIR_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;} 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);} void 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);} 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);