From 783291e6900292521a3895583785e0c04a56c5b3 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Thu, 17 Nov 2011 01:32:59 -0800 Subject: 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 Signed-off-by: Eric W. Biederman --- kernel/user_namespace.c | 42 ++++++++++++++++++++---------------------- 1 file changed, 20 insertions(+), 22 deletions(-) (limited to 'kernel/user_namespace.c') diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index 898e973bd1e8..ed08836558e0 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -27,6 +27,16 @@ int create_user_ns(struct cred *new) { 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 @@ int create_user_ns(struct cred *new) /* 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; @@ -63,35 +75,22 @@ int create_user_ns(struct cred *new) #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) +void free_user_ns(struct kref *kref) { struct user_namespace *parent, *ns = - container_of(work, struct user_namespace, destroyer); + container_of(kref, struct user_namespace, kref); + 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 = - 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) @@ -101,12 +100,11 @@ uid_t user_ns_map_uid(struct user_namespace *to, const struct cred *cred, uid_t 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 @@ gid_t user_ns_map_gid(struct user_namespace *to, const struct cred *cred, gid_t * 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; } } -- cgit v1.2.3-59-g8ed1b