/* * 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), .mq_bytes = 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 inline void uid_hash_insert(struct user_struct *up, struct hlist_head *hashent) { hlist_add_head(&up->uidhash_node, hashent); } static inline void uid_hash_remove(struct user_struct *up) { hlist_del_init(&up->uidhash_node); } static inline 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 struct kobject uids_kobject; /* represents /sys/kernel/uids directory */ static DEFINE_MUTEX(uids_mutex); 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); } 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 */ 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 */ 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 */ 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) { } 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 /* CONFIG_FAIR_USER_SCHED */ /* * 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) 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 new->mq_bytes = 0; new->locked_shm = 0; if (alloc_uid_keyring(new, current) < 0) { kmem_cache_free(uid_cachep, new); return NULL; } if (sched_create_user(new) < 0) { key_put(new->uid_keyring); key_put(new->session_keyring); kmem_cache_free(uid_cachep, new); 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(¤t->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);