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Re: [Libguestfs] [PATCH v2 3/5] launch: libvirt: Allow the SELinux label to be set on qcow2 overlay files.



On Fri, Mar 01, 2013 at 10:22:14AM +0000, Matthew Booth wrote:
> On Thu, 2013-02-28 at 16:02 +0000, Richard W.M. Jones wrote:
> > From: "Richard W.M. Jones" <rjones redhat com>
> > 
> > When a disk is opened readonly, the libvirt attach-method privately
> > creates a qcow2 overlay on top.
> > 
> > This commit lets that overlay get an SELinux label, and sets it to the
> > imagelabel specified by guestfs_internal_set_libvirt_selinux_label.
> > 
> > The above only applies to the libvirt attach-method.
> > ---
> >  src/launch-libvirt.c | 28 ++++++++++++++++++++--------
> >  1 file changed, 20 insertions(+), 8 deletions(-)
> > 
> > diff --git a/src/launch-libvirt.c b/src/launch-libvirt.c
> > index 318847a..b692fd6 100644
> > --- a/src/launch-libvirt.c
> > +++ b/src/launch-libvirt.c
> > @@ -133,8 +133,8 @@ static int is_custom_qemu (guestfs_h *g);
> >  static int is_blk (const char *path);
> >  static int random_chars (char *ret, size_t len);
> >  static void ignore_errors (void *ignore, virErrorPtr ignore2);
> > -static char *make_qcow2_overlay (guestfs_h *g, const char *path, const char *format);
> > -static int make_qcow2_overlay_for_drive (guestfs_h *g, struct drive *drv);
> > +static char *make_qcow2_overlay (guestfs_h *g, const char *path, const char *format, const char *selinux_imagelabel);
> > +static int make_qcow2_overlay_for_drive (guestfs_h *g, struct drive *drv, const char *selinux_imagelabel);
> >  static void drive_free_priv (void *);
> >  static void set_socket_create_context (guestfs_h *g);
> >  static void clear_socket_create_context (guestfs_h *g);
> > @@ -235,13 +235,13 @@ launch_libvirt (guestfs_h *g, const char *libvirt_uri)
> >     * Note that appliance can be NULL if using the old-style appliance.
> >     */
> >    if (appliance) {
> > -    params.appliance_overlay = make_qcow2_overlay (g, appliance, "raw");
> > +    params.appliance_overlay = make_qcow2_overlay (g, appliance, "raw", NULL);
> >      if (!params.appliance_overlay)
> >        goto cleanup;
> >    }
> 
> I remain convinced that this is going to bite us at some point in the
> future. The fact that it works now is essentially a quirk of the default
> SELinux policy. I still don't understand at all how the confined guest
> can access the underlying appliance image, which libvirt presumably
> doesn't relabel.

There's no mystery.  Because the appliance disk has a <shareable/>
tag, libvirt labels it as Dan explains here:

https://www.redhat.com/archives/libguestfs/2013-February/msg00139.html

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
virt-df lists disk usage of guests without needing to install any
software inside the virtual machine.  Supports Linux and Windows.
http://people.redhat.com/~rjones/virt-df/


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