On Fri, 4 Dec 2020 11:48:24 -0500 Tony Krowiak <akrowiak@xxxxxxxxxxxxx> wrote: > On 12/3/20 12:55 PM, Halil Pasic wrote: > > On Wed, 2 Dec 2020 18:41:01 -0500 > > Tony Krowiak <akrowiak@xxxxxxxxxxxxx> wrote: > > > >> The vfio_ap device driver registers a group notifier with VFIO when the > >> file descriptor for a VFIO mediated device for a KVM guest is opened to > >> receive notification that the KVM pointer is set (VFIO_GROUP_NOTIFY_SET_KVM > >> event). When the KVM pointer is set, the vfio_ap driver stashes the pointer > >> and calls the kvm_get_kvm() function to increment its reference counter. > >> When the notifier is called to make notification that the KVM pointer has > >> been set to NULL, the driver should clean up any resources associated with > >> the KVM pointer and decrement its reference counter. The current > >> implementation does not take care of this clean up. > >> > >> Signed-off-by: Tony Krowiak <akrowiak@xxxxxxxxxxxxx> > > Do we need a Fixes tag? Do we need this backported? In my opinion > > this is necessary since the interrupt patches. > > I'll put in a fixes tag: > Fixes: 258287c994de (s390: vfio-ap: implement mediated device open callback) > > Yes, this should probably be backported. I changed my mind regarding the severity of this issue. I was paranoid about post-mortem interrupts, and resulting notifier byte updates by the machine. What I overlooked is that the pin is going to prevent the memory form getting repurposed. I.e. if we have something like vmalloc(), vfio_pin(notifier_page), vfree(), I believe the notifier_page is not free (available for allocation). So the worst case scenario is IMHO a resource leak and not corruption. So I'm not sure this must be backported. Opinions? Regards, Halil
