The kvmgt code keeps a pointer to the struct kvm associated with the device, but doesn't actually hold a reference to it. If we do unclean shutdown testing (ie. killing the user process), then we can see the kvm association to the device unset, which causes kvmgt to trigger a device release via a work queue. Naturally we cannot guarantee that the cached struct kvm pointer is still valid at this point without holding a reference. The observed failure in this case is a stuck cpu trying to acquire the spinlock from the invalid reference, but other failure modes are clearly possible. Hold a reference to avoid this. Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx #v4.10 Cc: Jike Song <jike.song@xxxxxxxxx> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx> Cc: Zhenyu Wang <zhenyuw@xxxxxxxxxxxxxxx> Cc: Zhi Wang <zhi.a.wang@xxxxxxxxx> --- drivers/gpu/drm/i915/gvt/kvmgt.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c index 84d801638ede..142b8bd4ba6b 100644 --- a/drivers/gpu/drm/i915/gvt/kvmgt.c +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c @@ -1324,6 +1324,7 @@ static int kvmgt_guest_init(struct mdev_device *mdev) vgpu->handle = (unsigned long)info; info->vgpu = vgpu; info->kvm = kvm; + kvm_get_kvm(info->kvm); kvmgt_protect_table_init(info); gvt_cache_init(vgpu); @@ -1343,6 +1344,7 @@ static bool kvmgt_guest_exit(struct kvmgt_guest_info *info) } kvm_page_track_unregister_notifier(info->kvm, &info->track_node); + kvm_put_kvm(info->kvm); kvmgt_protect_table_destroy(info); gvt_cache_destroy(info->vgpu); vfree(info);
