Subversion Repositories test_project

/*

 * 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);