UBUNTU: Ubuntu-2.6.38-12.51

[linux-flexiantxendom0-natty.git] / kernel / user_namespace.c

diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 7908431..9da289c 100644 (file)
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -9,8 +9,11 @@
 #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
@@ -25,7 +28,7 @@ int create_user_ns(struct cred *new)
        struct user_struct *root_user;
        int n;
 
-       ns = kmalloc(sizeof(struct user_namespace), GFP_KERNEL);
+       ns = kmem_cache_alloc(user_ns_cachep, GFP_KERNEL);
        if (!ns)
                return -ENOMEM;
 
@@ -37,7 +40,7 @@ int create_user_ns(struct cred *new)
        /* Alloc new root user.  */
        root_user = alloc_uid(ns, 0);
        if (!root_user) {
-               kfree(ns);
+               kmem_cache_free(user_ns_cachep, ns);
                return -ENOMEM;
        }
 
@@ -54,18 +57,81 @@ int create_user_ns(struct cred *new)
 #endif
        /* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */
 
-       /* alloc_uid() incremented the userns refcount.  Just set it to 1 */
-       kref_set(&ns->kref, 1);
+       /* 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;
+       struct user_namespace *ns =
+               container_of(kref, struct user_namespace, kref);
 
-       ns = container_of(kref, struct user_namespace, kref);
-       free_uid(ns->creator);
-       kfree(ns);
+       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);