-----Original Message----- From: Daniel P. Berrange [mailto:berrange@redhat.com] Sent: Wednesday, November 13, 2013 6:35 PM To: Chen Hanxiao Cc: libvir-list@redhat.com Subject: Re: [libvirt] [PATCH v2]lxc: don't mount dir if ownership couldn't be known
On Wed, Nov 13, 2013 at 04:51:43PM +0800, Chen Hanxiao wrote:
From: Chen Hanxiao <chenhanxiao@cn.fujitsu.com>
If we enable userns, we could bind mount some dirs from host to guest, which don't belong to the target mapped uid/gid.
Such as we could bind mount root's dirs to guest. What is worse, we could even modify root's files in that bind dir inside container.
I still can't see what the problem is from the description here. Please can you give a clear example of the config used and exactly what goes wrong.
1. enable user namespace <idmap> <uid start='0' target='1001' count='10'/> <gid start='0' target='1001' count='10'/> </idmap> 2. bind mount some dirs to container, which belongs to root or other users. <filesystem type='mount' accessmode='passthrough'> <source dir='/media/LXC1'/> <target dir='/mnt'/> </filesystem> # ll /media/ ... drwxr-xr-x. 3 root root 4096 Nov 13 17:21 LXC1 ... 3. start container I used to encounter issues: inside container, we could modify files under /mnt So I think inside user namespace, if we do not have a proper id mapping, we should not bind mount it for containers, or at least set it as readonly.