/* * 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_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; 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(¤t->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); }Lines 1–500 of 526. Load more
/* * 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_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; 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_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\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_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, "%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(¤t->sighand->siglock); free_uid(old_user); suid_keys(current); } #ifdef CONFIG_USER_NS 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); }