On Wed, Jun 05, 2013 at 09:18:37PM -0400, Luiz Capitulino wrote: > The balloon_page_dequeue() function can return NULL. If it does for > the first page being freed, then leak_balloon() will create a > scatter list with len=0. Which in turn seems to generate an invalid > virtio request. > > I didn't get this in practice, I found it by code review. On the other > hand, such an invalid virtio request will cause errors in QEMU and > fill_balloon() also performs the same check implemented by this commit. > > Signed-off-by: Luiz Capitulino <lcapitulino@xxxxxxxxxx> > Acked-by: Rafael Aquini <aquini@xxxxxxxxxx> > --- > > o v2 > > - Improve changelog > > drivers/virtio/virtio_balloon.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c > index bd3ae32..71af7b5 100644 > --- a/drivers/virtio/virtio_balloon.c > +++ b/drivers/virtio/virtio_balloon.c > @@ -191,7 +191,8 @@ static void leak_balloon(struct virtio_balloon *vb, size_t num) > * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST); > * is true, we *have* to do it in this order > */ > - tell_host(vb, vb->deflate_vq); Luiz, sorry for not being clearer before. I was referring to add a commentary on code, to explain in short words why we should not get rid of this check point. > + if (vb->num_pfns != 0) > + tell_host(vb, vb->deflate_vq); > mutex_unlock(&vb->balloon_lock); If the comment is regarded as unnecessary, then just ignore my suggestion. I'm OK with your patch. :) Cheers! -- Rafael -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>