From: Alexander Duyck alexander.h.duyck@linux.intel.com
commit fb69c2c896fc8289b0d9e2c0791472e7cd398bca upstream.
We should disable free page reporting if page poisoning is enabled but we cannot report it via the balloon interface. This way we can avoid the possibility of corrupting guest memory. Normally the page poisoning feature should always be present when free page reporting is enabled on the hypervisor, however this allows us to correctly handle a case of the virtio-balloon device being possibly misconfigured.
Fixes: 5d757c8d518d ("virtio-balloon: add support for providing free page reports to host") Cc: stable@vger.kernel.org Acked-by: David Hildenbrand david@redhat.com Signed-off-by: Alexander Duyck alexander.h.duyck@linux.intel.com Link: https://lore.kernel.org/r/20200508173732.17877.85060.stgit@localhost.localdo... Signed-off-by: Michael S. Tsirkin mst@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/virtio/virtio_balloon.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
--- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -1107,11 +1107,18 @@ static int virtballoon_restore(struct vi
static int virtballoon_validate(struct virtio_device *vdev) { - /* Tell the host whether we care about poisoned pages. */ + /* + * Inform the hypervisor that our pages are poisoned or + * initialized. If we cannot do that then we should disable + * page reporting as it could potentially change the contents + * of our free pages. + */ if (!want_init_on_free() && (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY) || !page_poisoning_enabled())) __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON); + else if (!virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) + __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_REPORTING);
__virtio_clear_bit(vdev, VIRTIO_F_IOMMU_PLATFORM); return 0;