| Message ID | 20130605171031.7448deea@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Jun 05, 2013 at 05:10:31PM -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. > > Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com> > --- > > PS: I didn't get this in practice. I found it by code review. On the other > hand, automatic-ballooning was able to put such invalid requests in > the virtqueue and QEMU would explode... > Nice catch! The patch looks sane and replicates the check done at fill_balloon(). I think we also could use this P.S. as a commentary to let others aware of this scenario. Thanks Luiz! Acked-by: Rafael Aquini <aquini@redhat.com> > PPS: Very lightly tested > > 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); > } > -- > 1.8.1.4 > -- 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 18:24:49 -0300 Rafael Aquini <aquini@redhat.com> wrote: > On Wed, Jun 05, 2013 at 05:10:31PM -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. > > > > Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com> > > --- > > > > PS: I didn't get this in practice. I found it by code review. On the other > > hand, automatic-ballooning was able to put such invalid requests in > > the virtqueue and QEMU would explode... > > > > Nice catch! The patch looks sane and replicates the check done at > fill_balloon(). I think we also could use this P.S. as a commentary > to let others aware of this scenario. Thanks Luiz! Want me to respin? > Acked-by: Rafael Aquini <aquini@redhat.com> Thanks for your review! > > > > PPS: Very lightly tested > > > > 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); > > } > > -- > > 1.8.1.4 > > > -- 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, Jun 05, 2013 at 07:08:44PM -0400, Luiz Capitulino wrote: > On Wed, 5 Jun 2013 18:24:49 -0300 > Rafael Aquini <aquini@redhat.com> wrote: > > > On Wed, Jun 05, 2013 at 05:10:31PM -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. > > > > > > Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com> > > > --- > > > > > > PS: I didn't get this in practice. I found it by code review. On the other > > > hand, automatic-ballooning was able to put such invalid requests in > > > the virtqueue and QEMU would explode... > > > > > > > Nice catch! The patch looks sane and replicates the check done at > > fill_balloon(). I think we also could use this P.S. as a commentary > > to let others aware of this scenario. Thanks Luiz! > > Want me to respin? > That would be great, indeed. I guess the commentary could also go for the same if case at fill_balloon(), assuming the tests are placed to prevent the same scenario you described at changelog. You can stick my Ack on it, if reposting. 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
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); }
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. Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com> --- PS: I didn't get this in practice. I found it by code review. On the other hand, automatic-ballooning was able to put such invalid requests in the virtqueue and QEMU would explode... PPS: Very lightly tested drivers/virtio/virtio_balloon.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)