1 files changed, 137 insertions, 0 deletions
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
new file mode 100644
index 00000000..9da289c3
--- /dev/null
+++ b/kernel/user_namespace.c
@@ -0,0 +1,137 @@
+/*
+ *  This program is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU General Public License as
+ *  published by the Free Software Foundation, version 2 of the
+ *  License.
+ */
+
+#include <linux/module.h>
+#include <linux/nsproxy.h>
+#include <linux/slab.h>
+#include <linux/user_namespace.h>
+#include <linux/highuid.h>
+#include <linux/cred.h>
+
+static struct kmem_cache *user_ns_cachep __read_mostly;
+
+/*
+ * Create a new user namespace, deriving the creator from the user in the
+ * passed credentials, and replacing that user with the new root user for the
+ * new namespace.
+ *
+ * This is called by copy_creds(), which will finish setting the target task's
+ * credentials.
+ */
+int create_user_ns(struct cred *new)
+{
+	struct user_namespace *ns;
+	struct user_struct *root_user;
+	int n;
+
+	ns = kmem_cache_alloc(user_ns_cachep, GFP_KERNEL);
+	if (!ns)
+		return -ENOMEM;
+
+	kref_init(&ns->kref);
+
+	for (n = 0; n < UIDHASH_SZ; ++n)
+		INIT_HLIST_HEAD(ns->uidhash_table + n);
+
+	/* Alloc new root user.  */
+	root_user = alloc_uid(ns, 0);
+	if (!root_user) {
+		kmem_cache_free(user_ns_cachep, ns);
+		return -ENOMEM;
+	}
+
+	/* set the new root user in the credentials under preparation */
+	ns->creator = new->user;
+	new->user = root_user;
+	new->uid = new->euid = new->suid = new->fsuid = 0;
+	new->gid = new->egid = new->sgid = new->fsgid = 0;
+	put_group_info(new->group_info);
+	new->group_info = get_group_info(&init_groups);
+#ifdef CONFIG_KEYS
+	key_put(new->request_key_auth);
+	new->request_key_auth = NULL;
+#endif
+	/* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */
+
+	/* root_user holds a reference to ns, our reference can be dropped */
+	put_user_ns(ns);
+
+	return 0;
+}
+
+/*
+ * Deferred destructor for a user namespace.  This is required because
+ * free_user_ns() may be called with uidhash_lock held, but we need to call
+ * back to free_uid() which will want to take the lock again.
+ */
+static void free_user_ns_work(struct work_struct *work)
+{
+	struct user_namespace *ns =
+		container_of(work, struct user_namespace, destroyer);
+	free_uid(ns->creator);
+	kmem_cache_free(user_ns_cachep, ns);
+}
+
+void free_user_ns(struct kref *kref)
+{
+	struct user_namespace *ns =
+		container_of(kref, struct user_namespace, kref);
+
+	INIT_WORK(&ns->destroyer, free_user_ns_work);
+	schedule_work(&ns->destroyer);
+}
+EXPORT_SYMBOL(free_user_ns);
+
+uid_t user_ns_map_uid(struct user_namespace *to, const struct cred *cred, uid_t uid)
+{
+	struct user_namespace *tmp;
+
+	if (likely(to == cred->user->user_ns))
+		return uid;
+
+
+	/* Is cred->user the creator of the target user_ns
+	 * or the creator of one of it's parents?
+	 */
+	for ( tmp = to; tmp != &init_user_ns;
+	      tmp = tmp->creator->user_ns ) {
+		if (cred->user == tmp->creator) {
+			return (uid_t)0;
+		}
+	}
+
+	/* No useful relationship so no mapping */
+	return overflowuid;
+}
+
+gid_t user_ns_map_gid(struct user_namespace *to, const struct cred *cred, gid_t gid)
+{
+	struct user_namespace *tmp;
+
+	if (likely(to == cred->user->user_ns))
+		return gid;
+
+	/* Is cred->user the creator of the target user_ns
+	 * or the creator of one of it's parents?
+	 */
+	for ( tmp = to; tmp != &init_user_ns;
+	      tmp = tmp->creator->user_ns ) {
+		if (cred->user == tmp->creator) {
+			return (gid_t)0;
+		}
+	}
+
+	/* No useful relationship so no mapping */
+	return overflowgid;
+}
+
+static __init int user_namespaces_init(void)
+{
+	user_ns_cachep = KMEM_CACHE(user_namespace, SLAB_PANIC);
+	return 0;
+}
+module_init(user_namespaces_init);