userns: Convert group_info values from gid_t to kgid_t.

As a first step to converting struct cred to be all kuid_t and kgid_t
values convert the group values stored in group_info to always be
kgid_t values.   Unless user namespaces are used this change should
have no effect.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

security/keys/permission.c

@@ -53,7 +53,8 @@ int key_task_permission(const key_ref_t key_ref, const struct cred *cred,
 			goto use_these_perms;
 		}
 
-		ret = groups_search(cred->group_info, key->gid);
+		ret = groups_search(cred->group_info,
+				    make_kgid(current_user_ns(), key->gid));
 		if (ret) {
 			kperm = key->perm >> 8;
 			goto use_these_perms;