| Message ID | 20130605211837.1fc9b902@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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@redhat.com> > Acked-by: Rafael Aquini <aquini@redhat.com> > --- > > 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 from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, 6 Jun 2013 11:13:58 -0300 Rafael Aquini <aquini@redhat.com> wrote: > 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@redhat.com> > > Acked-by: Rafael Aquini <aquini@redhat.com> > > --- > > > > 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. Oh. > > + 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. :) IMHO, the code is clear enough. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, 5 Jun 2013 21:18:37 -0400 Luiz Capitulino <lcapitulino@redhat.com> 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@redhat.com> > Acked-by: Rafael Aquini <aquini@redhat.com> Andrew, can you pick this one? > --- > > 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); > + if (vb->num_pfns != 0) > + tell_host(vb, vb->deflate_vq); > mutex_unlock(&vb->balloon_lock); > release_pages_by_pfn(vb->pfns, vb->num_pfns); > } -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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); + if (vb->num_pfns != 0) + tell_host(vb, vb->deflate_vq); mutex_unlock(&vb->balloon_lock); release_pages_by_pfn(vb->pfns, vb->num_pfns); }