Initial import

1 files changed, 228 insertions, 0 deletions

diff --git a/kernel/user.c b/kernel/user.c
new file mode 100644
index 000000000..b069ccbfb
--- /dev/null
+++ b/kernel/user.c
@@ -0,0 +1,228 @@
+/*
+ * 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/export.h>
+#include <linux/user_namespace.h>
+#include <linux/proc_ns.h>
+
+/*
+ * userns count is 1 for root user, 1 for init_uts_ns,
+ * and 1 for... ?
+ */
+struct user_namespace init_user_ns = {
+	.uid_map = {
+		.nr_extents = 1,
+		.extent[0] = {
+			.first = 0,
+			.lower_first = 0,
+			.count = 4294967295U,
+		},
+	},
+	.gid_map = {
+		.nr_extents = 1,
+		.extent[0] = {
+			.first = 0,
+			.lower_first = 0,
+			.count = 4294967295U,
+		},
+	},
+	.projid_map = {
+		.nr_extents = 1,
+		.extent[0] = {
+			.first = 0,
+			.lower_first = 0,
+			.count = 4294967295U,
+		},
+	},
+	.count = ATOMIC_INIT(3),
+	.owner = GLOBAL_ROOT_UID,
+	.group = GLOBAL_ROOT_GID,
+	.ns.inum = PROC_USER_INIT_INO,
+#ifdef CONFIG_USER_NS
+	.ns.ops = &userns_operations,
+#endif
+	.flags = USERNS_INIT_FLAGS,
+#ifdef CONFIG_PERSISTENT_KEYRINGS
+	.persistent_keyring_register_sem =
+	__RWSEM_INITIALIZER(init_user_ns.persistent_keyring_register_sem),
+#endif
+};
+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_BITS	(CONFIG_BASE_SMALL ? 3 : 7)
+#define UIDHASH_SZ	(1 << UIDHASH_BITS)
+#define UIDHASH_MASK		(UIDHASH_SZ - 1)
+#define __uidhashfn(uid)	(((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK)
+#define uidhashentry(uid)	(uidhash_table + __uidhashfn((__kuid_val(uid))))
+
+static struct kmem_cache *uid_cachep;
+struct hlist_head uidhash_table[UIDHASH_SZ];
+
+/*
+ * 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 1, for init task cred */
+struct user_struct root_user = {
+	.__count	= ATOMIC_INIT(1),
+	.processes	= ATOMIC_INIT(1),
+	.sigpending	= ATOMIC_INIT(0),
+	.locked_shm     = 0,
+	.uid		= GLOBAL_ROOT_UID,
+};
+
+/*
+ * 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(kuid_t uid, struct hlist_head *hashent)
+{
+	struct user_struct *user;
+
+	hlist_for_each_entry(user, hashent, uidhash_node) {
+		if (uid_eq(user->uid, uid)) {
+			atomic_inc(&user->__count);
+			return user;
+		}
+	}
+
+	return NULL;
+}
+
+/* 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)
+	__releases(&uidhash_lock)
+{
+	uid_hash_remove(up);
+	spin_unlock_irqrestore(&uidhash_lock, flags);
+	key_put(up->uid_keyring);
+	key_put(up->session_keyring);
+	kmem_cache_free(uid_cachep, up);
+}
+
+/*
+ * 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(kuid_t uid)
+{
+	struct user_struct *ret;
+	unsigned long flags;
+
+	spin_lock_irqsave(&uidhash_lock, flags);
+	ret = uid_hash_find(uid, uidhashentry(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(kuid_t uid)
+{
+	struct hlist_head *hashent = uidhashentry(uid);
+	struct user_struct *up, *new;
+
+	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);
+
+		/*
+		 * 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) {
+			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);
+	}
+
+	return up;
+
+out_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(uidhash_table + n);
+
+	/* Insert the root user immediately (init already runs as root) */
+	spin_lock_irq(&uidhash_lock);
+	uid_hash_insert(&root_user, uidhashentry(GLOBAL_ROOT_UID));
+	spin_unlock_irq(&uidhash_lock);
+
+	return 0;
+}
+subsys_initcall(uid_cache_init);