On Tue, Jun 14, 2016 at 04:03:43PM +0800, Wei Xu wrote: > On 2016年06月09日 05:48, Aaron Conole wrote: > > Flavio Leitner <f...@redhat.com> writes: > > > > > Adding Aaron who is fixing exactly that on the OVS side. > > > > > > Aaron, please see the last question in the bottom of this email. > > > > > > On Wed, Jun 08, 2016 at 06:07:29AM -0400, Amnon Ilan wrote: > > > > > > > > > > > > ----- Original Message ----- > > > > > From: "Michal Privoznik" <mpriv...@redhat.com> > > > > > To: "Daniel P. Berrange" <berra...@redhat.com> > > > > > Cc: qemu-devel@nongnu.org, "amit shah" <amit.s...@redhat.com>, > > > > > jasow...@redhat.com, "Wei Xu" <w...@redhat.com>, > > > > > arm...@redhat.com > > > > > Sent: Thursday, June 2, 2016 2:38:53 PM > > > > > Subject: Re: [Qemu-devel] [RFC Patch 0/3] Accept passed in socket > > > > > 'fd' open from outside for unix socket > > > > > > > > > > On 02.06.2016 10:29, Daniel P. Berrange wrote: > > > > > > On Thu, Jun 02, 2016 at 09:41:56AM +0200, Michal Privoznik wrote: > > > > > > > On 01.06.2016 18:16, Wei Xu wrote: > > > > > > > > On 2016年06月01日 00:44, Daniel P. Berrange wrote: > > > > > > > > > On Wed, Jun 01, 2016 at 12:30:44AM +0800, w...@redhat.com > > > > > > > > > wrote: > > > > > > > > > > From: Wei Xu <w...@redhat.com> > > > > > > > > > > > > > > > > > > > > Recently I'm working on a fd passing issue, selinux forbids > > > > > > > > > > qemu to > > > > > > > > > > create a unix socket for a chardev when managing VMs with > > > > > > > > > > libvirt, > > > > > > > > > > because qemu don't have sufficient permissions in this > > > > > > > > > > case, and > > > > > > > > > > proposal from libvirt team is opening the 'fd' in libvirt > > > > > > > > > > and merely > > > > > > > > > > passing it to qemu. > > > > > > > > > > > > > > > > > > This sounds like a bug in libvirt, or selinux, or a mistaken > > > > > > > > > configuration > > > > > > > > > of the guest. It is entirely possible for QEMU to create a > > > > > > > > > unix socket > > > > > > > > > - not > > > > > > > > > least because that is exactly what QEMU uses for its QMP > > > > > > > > > monitor > > > > > > > > > backend. > > > > > > > > > Looking at your example command line, I think the issue is > > > > > > > > > simply that > > > > > > > > > you > > > > > > > > > should be putting the sockets in a different location. ie at > > > > > > > > > /var/lib/libvirt/qemu/$guest-vhost-user1.sock where QEMU has > > > > > > > > > permission to > > > > > > > > > create sockets already. > > > > > > > > ah.. adjusting permission or file location can solve this > > > > > > > > problem, i'm > > > > > > > > guessing maybe this is a more security concern, the socket is > > > > > > > > used as a > > > > > > > > network interface for a vm, similar as the qcow image file, > > > > > > > > thus should > > > > > > > > prevent it to be arbitrarily accessed. > > > > > > > > > > > > > > > > Michael, do you have any comment on this? > > > > > > > > > > > > > > I haven't seen the patches. But in libvirt we allow users to > > > > > > > create a > > > > > > > vhostuser interface and even specify where the socket should be > > > > > > > placed: > > > > > > > > > > > > > > <interface type='vhostuser'> > > > > > > > <mac address='52:54:00:ee:96:6c'/> > > > > > > > <source type='unix' path='/tmp/vhost1.sock' mode='server'/> > > > > > > > <model type='virtio'/> > > > > > > > </interface> > > > > > > > > > > > > > > The following cmd line is generated by libvirt then: > > > > > > > > > > > > > > -chardev socket,id=charnet1,path=/tmp/vhost1.sock,server \ > > > > > > > -netdev type=vhost-user,id=hostnet1,chardev=charnet1 \ > > > > > > > -device > > > > > > > virtio-net-pci,netdev=hostnet1,id=net1,mac=52:54:00:ee:96:6c,bus=pci.0,\ > > > > > > > > > > > > > > Now, if we accept only /var/run/openvwitch path in > > > > > > > /interface/source/@path (or whatever path to OVS is), we don't > > > > > > > need this > > > > > > > and have users manually label the dir (unless already labeled). > > > > > > > But > > > > > > > since we accept just any path in there, we should make sure that > > > > > > > qemu is > > > > > > > then able to create the socket. One possible fix would be to > > > > > > > allow qemu > > > > > > > create sockets just anywhere in the system. This, however, brings > > > > > > > huge > > > > > > > security risks and it's not acceptable IMO. The other option > > > > > > > would be > > > > > > > that libvirt would create the socket, and pass its FD to qemu > > > > > > > (since > > > > > > > libvirt already is allowed to create sockets anywhere). > > > > > > > > > > > > There are plenty of other places where we allow arbitrary paths in > > > > > > the > > > > > > XML, but which have restrictions imposed by the security drivers. > > > > > > Not > > > > > > least the <channel> devices which have the exact same scenario as > > > > > > this > > > > > > network device, and require use of /var/lib/libvirt/qemu as the > > > > > > directory > > > > > > for the sockets. We certainly do not want to allow QEMU to create > > > > > > sockets > > > > > > anywhere. > > > > > > > > > > > > I don't think we want to grant QEMU svirtt permission to create > > > > > > sockets > > > > > > in the /var/run/openvswitch directory either really.IMHO, users of > > > > > > vhost > > > > > > user should really be using /var/lib/libvirt/qemu, as is used for > > > > > > all > > > > > > other UNIX sockets we create wrt other devices. > > > > > > > > > > Okay. I can live with that; but in that case we should document it > > > > > somewhere, that we guarantee only paths under /var/lib/libvirt/ to be > > > > > accessible and for the rest we do our best but maybe require sys admin > > > > > intervention (e.g. to label the whole tree for a non-standard > > > > > location). > > > > > > > > Does OVS has some limit for it's sockets to be only in > > > > /var/run/openvswitch ? > > > > As of a recent commit, it can only be in /var/run/openvswitch or a > > subdirectory therein (found in the openvswitch database). > Aaron, thanks for your reply. > > Just a question about the usage of openvswitch, in this user case when > launching a vhostuser/dpdk via libvirt, qemu works as server mode for socket > under /var/run/openvswitch, but per my previous test, ovs/dpdk always works > as server mode, which means ovs will creates the socket and listening for > connection, thus qemu works as client mode, does ovs/dpdk support working in > client mode? which means it's qemu's duty to create the socket? and ovs will > connect to it on demanding?
Oh, I was assuming that QEMU would be working in server mode - no wonder we have somewhat different views :-) If OVS is running the UNIX socket server, and QEMU is purely the client, then that means the solution would be slightly different. In particular libvirt would *not* do any SELinux relabelling. Instead you would have to get an addition to the SELinux policy, to allow svirt_t type to connect to the SELinux type associated with the openvswitch socket. For file permissions, if the OVS socket is owned by a particular UNIX group, you could potentially add the 'qemu' user account to that group to grant access. Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|
