userns: Simplify the user_namespace by making userns->creator a kuid.
- Transform userns->creator from a user_struct reference to a simple
kuid_t, kgid_t pair.
In cap_capable this allows the check to see if we are the creator of
a namespace to become the classic suser style euid permission check.
This allows us to remove the need for a struct cred in the mapping
functions and still be able to dispaly the user namespace creators
uid and gid as 0.
- Remove the now unnecessary delayed_work in free_user_ns.
All that is left for free_user_ns to do is to call kmem_cache_free
and put_user_ns. Those functions can be called in any context
so call them directly from free_user_ns removing the need for delayed work.
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 898e973..ed08836 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -27,6 +27,16 @@
{
struct user_namespace *ns, *parent_ns = new->user_ns;
struct user_struct *root_user;
+ kuid_t owner = make_kuid(new->user_ns, new->euid);
+ kgid_t group = make_kgid(new->user_ns, new->egid);
+
+ /* The creator needs a mapping in the parent user namespace
+ * or else we won't be able to reasonably tell userspace who
+ * created a user_namespace.
+ */
+ if (!kuid_has_mapping(parent_ns, owner) ||
+ !kgid_has_mapping(parent_ns, group))
+ return -EPERM;
ns = kmem_cache_alloc(user_ns_cachep, GFP_KERNEL);
if (!ns)
@@ -43,7 +53,9 @@
/* set the new root user in the credentials under preparation */
ns->parent = parent_ns;
- ns->creator = new->user;
+ ns->owner = owner;
+ ns->group = group;
+ free_uid(new->user);
new->user = root_user;
new->uid = new->euid = new->suid = new->fsuid = 0;
new->gid = new->egid = new->sgid = new->fsgid = 0;
@@ -63,34 +75,21 @@
#endif
/* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */
- /* Leave the reference to our user_ns with the new cred */
+ /* Leave the new->user_ns reference with the new user namespace. */
+ /* Leave the reference to our user_ns with the new cred. */
new->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 *parent, *ns =
- container_of(work, struct user_namespace, destroyer);
- parent = ns->parent;
- free_uid(ns->creator);
- kmem_cache_free(user_ns_cachep, ns);
- put_user_ns(parent);
-}
-
void free_user_ns(struct kref *kref)
{
- struct user_namespace *ns =
+ struct user_namespace *parent, *ns =
container_of(kref, struct user_namespace, kref);
- INIT_WORK(&ns->destroyer, free_user_ns_work);
- schedule_work(&ns->destroyer);
+ parent = ns->parent;
+ kmem_cache_free(user_ns_cachep, ns);
+ put_user_ns(parent);
}
EXPORT_SYMBOL(free_user_ns);
@@ -101,12 +100,11 @@
if (likely(to == cred->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->parent ) {
- if (cred->user == tmp->creator) {
+ if (uid_eq(cred->user->uid, tmp->owner)) {
return (uid_t)0;
}
}
@@ -126,7 +124,7 @@
* or the creator of one of it's parents?
*/
for ( tmp = to; tmp != &init_user_ns; tmp = tmp->parent ) {
- if (cred->user == tmp->creator) {
+ if (uid_eq(cred->user->uid, tmp->owner)) {
return (gid_t)0;
}
}