Re: [libvirt] [PATCH 1/4] virt-aa-helper: fix paths for usb hostdevs

On Fri, Sep 29, 2017 at 4:58 PM, Michal Privoznik <mprivozn(a)redhat.co m> wrote: > On 09/20/2017 04:59 PM, Christian Ehrhardt wrote: > > If users only specified vendor&product (the common case) then > > parsing > > the xml via virDomainHostdevSubsysUSBDefParseXML would only set > > these. > > Bus and Device would much later be added when the devices are > > prepared > > to be added. > > > > Due to that a hot-add of a usb hostdev works as the device is > > prepared > > and virt-aa-helper processes the new internal xml. But on an > > initial > > guest start at the time virt-aa-helper renders the apparmor rules > > the > > bus/device id's are not set yet: > > > > p ctl->def->hostdevs[0]->source.subsys.u.usb > > $12 = {autoAddress = false, bus = 0, device = 0, vendor = 1921, > > product > > = 21888} > > > > That causes rules to be wrong: > > "/dev/bus/usb/000/000" rw, > > > > The fix calls virHostdevFindUSBDevice after reading the XML from > > irt-aa-helper to only add apparmor rules for devices that could > > be found > > and now are fully known to be able to write the rule correctly. > > > > It uncondtionally sets virHostdevFindUSBDevice mandatory > > attribute as > > adding an apparmor rule for a device not found makes no sense no > > matter > > what startup policy it has set. > > > > Signed-off-by: Christian Ehrhardt <christian.ehrhardt(a)canonical.c > > om> > > --- > > src/security/virt-aa-helper.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/src/security/virt-aa-helper.c > > b/src/security/virt-aa-helper.c > > index 7944dc1..d1518ea 100644 > > --- a/src/security/virt-aa-helper.c > > +++ b/src/security/virt-aa-helper.c > > @@ -55,6 +55,7 @@ > > #include "virrandom.h" > > #include "virstring.h" > > #include "virgettext.h" > > +#include "virhostdev.h" > > > > #include "storage/storage_source.h" > > > > @@ -1069,6 +1070,9 @@ get_files(vahControl * ctl) > > if (usb == NULL) > > continue; > > > > + if (virHostdevFindUSBDevice(dev, true, &usb) < > > 0) > > + continue; > > + > > Shouldn't we rather fail in this case? Or, what happens if > startupPolicy > of the device is set to 'optional'? I think we need to error out > here > (although, we've probably errored out earlier in the process). > Hi, sorry for the late reply, but I was finally getting some time off for a few days. I intentionally decided not to error out to avoid a new "source" of issues. Compare the two options we have: 1. continue if not finding the device 1.1 likely case we found it, rule will be correct - good 1.2 we don't find it (for whatever reason) - we are "as bad" as before this fix, but not worse 2. error out if not finding the device 2.1 likely case we found it, rule will be correct - good 2.2 we don't find it (for whatever reason) - we are now failing completely What I don't like about 2.2 is that there might be cases things would have been kind of ok, depsite whatever dark usb magic hit some special setup. In those cases if we error out we add a new chance to fail. And as there are often too many unknowns, so I chose the safer option.