1 files changed, 510 insertions, 0 deletions
diff --git a/kernel/user.c b/kernel/user.c
new file mode 100644
index 00000000000..46d0165ca70
--- /dev/null
+++ b/kernel/user.c
@@ -0,0 +1,510 @@
+/*
+ * 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);
+}
+
+#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 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) {
+			/* possibly resurrect an "almost deleted" object */
+			if (atomic_inc_return(&user->__count) == 1)
+				cancel_delayed_work(&user->work);
+			return user;
+		}
+	}
+
+	return NULL;
+}
+
+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, "%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);
+}
+
+/* delayed 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.work);
+	unsigned long flags;
+	int remove_user = 0;
+
+	/* Make uid_hash_remove() + sysfs_remove_file() + kobject_del()
+	 * atomic.
+	 */
+	uids_mutex_lock();
+
+	spin_lock_irqsave(&uidhash_lock, flags);
+	if (atomic_read(&up->__count) == 0) {
+		uid_hash_remove(up);
+		remove_user = 1;
+	}
+	spin_unlock_irqrestore(&uidhash_lock, 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)
+{
+	INIT_DELAYED_WORK(&up->work, cleanup_user_struct);
+	schedule_delayed_work(&up->work, msecs_to_jiffies(1000));
+	spin_unlock_irqrestore(&uidhash_lock, flags);
+}
+
+#else	/* CONFIG_USER_SCHED && CONFIG_SYSFS */
+
+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;
+}
+
+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);
+
+}
+#else
+int 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);