Messages in this thread Patch in this message | | | Date | Wed, 5 Jun 2013 17:10:31 -0400 | From | Luiz Capitulino <> | Subject | [PATCH] virtio_balloon: leak_balloon(): only tell host if we got pages deflated |
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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(-)
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
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