From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756413Ab3AWQPt (ORCPT ); Wed, 23 Jan 2013 11:15:49 -0500 Received: from mx1.redhat.com ([209.132.183.28]:58140 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755364Ab3AWQPr (ORCPT ); Wed, 23 Jan 2013 11:15:47 -0500 Date: Wed, 23 Jan 2013 11:02:21 -0500 From: Aristeu Rozanski To: linux-kernel@vger.kernel.org Cc: "Eric W. Biederman" , "Serge E. Hallyn" Subject: [PATCH] userns: improve uid/gid map collision detection Message-ID: <20130123160221.GG17632@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Initial implementation of the uid/gid maps will enforce that the maps should be in order and would prevent a use case like this from being used: 0 1000 1 48 500 1 since the second entry both values should be bigger than the previous. This patch implements a more elaborate collision detection allowing any order to be used. Cc: "Eric W. Biederman" Cc: "Serge E. Hallyn" Signed-off-by: Aristeu Rozanski diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index 2b042c4..fb0e492 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -521,6 +521,28 @@ struct seq_operations proc_projid_seq_operations = { static DEFINE_MUTEX(id_map_mutex); +#define in_range(b,first,len) ((b)>=(first)&&(b)<(first)+(len)) +static inline int extent_collision(struct uid_gid_map *new_map, + struct uid_gid_extent *extent) +{ + int i; + struct uid_gid_extent *cur; + + for (i = 0; i < new_map->nr_extents; i++) { + cur = &new_map->extent[i]; + if (in_range(extent->first, cur->first, cur->count) || + in_range(extent->first + extent->count, cur->first, + cur->count)) + return 1; + if (in_range(extent->lower_first, cur->lower_first, + cur->count) || + in_range(extent->lower_first + extent->count, + cur->lower_first, cur->count)) + return 1; + } + return 0; +} + static ssize_t map_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos, int cap_setid, @@ -634,10 +656,7 @@ static ssize_t map_write(struct file *file, const char __user *buf, if ((extent->lower_first + extent->count) <= extent->lower_first) goto out; - /* For now only accept extents that are strictly in order */ - if (last && - (((last->first + last->count) > extent->first) || - ((last->lower_first + last->count) > extent->lower_first))) + if (extent_collision(&new_map, extent)) goto out; new_map.nr_extents++;