On Tue, Oct 30, 2018 at 04:47:32PM +0100, Michal Privoznik wrote:
On 10/30/2018 04:07 PM, Daniel P. Berrangé wrote:
On Tue, Oct 30, 2018 at 03:45:36PM +0100, Michal Privoznik wrote:
On 10/30/2018 02:46 PM, Michal Privoznik wrote:
On 10/30/2018 01:55 PM, Daniel P. Berrangé wrote:
On Tue, Oct 30, 2018 at 10:32:08AM +0000, Daniel P. Berrangé wrote:
On Tue, Oct 30, 2018 at 11:08:45AM +0100, Michal Privoznik wrote: > On 10/30/2018 10:35 AM, Daniel P. Berrangé wrote: >> On Tue, Oct 30, 2018 at 09:13:50AM +0100, Michal Privoznik wrote: >>> On 10/29/2018 06:34 PM, Marc Hartmayer wrote: >>>> Introduce caching whether /dev/kvm is usable as the QEMU user:QEMU >>>> group. This reduces the overhead of the QEMU capabilities cache >>>> lookup. Before this patch there were many fork() calls used for >>>> checking whether /dev/kvm is accessible. Now we store the result >>>> whether /dev/kvm is accessible or not and we only need to re-run the >>>> virFileAccessibleAs check if the ctime of /dev/kvm has changed. >>>> >>>> Suggested-by: Daniel P. Berrangé <berrange@redhat.com> >>>> Signed-off-by: Marc Hartmayer <mhartmay@linux.ibm.com> >>>> --- >>>> src/qemu/qemu_capabilities.c | 54 ++++++++++++++++++++++++++++++++++-- >>>> 1 file changed, 52 insertions(+), 2 deletions(-) >>>>
Not really. Udev is in use everywhere, so this behaviour makes the patch useless in practice, even though it is technically right in theory :-(
Well, caching owner + seclabels + ACLs won't help either. What if user loads some profile into AppArmor or something that denies previously allowed access to /dev/kvm (or vice versa)? What I am saying is that there are some security models which base their decisions on something else than file attributes.
The virFileAccessibleAs check for /dev/kvm was put in their to ensure that we correctly report usability of KVM in the capabilities XML according to file permissions/ownership. Essentially KVM is not usable until the udev rule is applied to change permissions to world accessible or to set the kvm group. I don't think we need to care aout selinux/apparmor restrictions - just need to be no worse than what we cope with today, which is just perms and owner/group. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|