3.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Luiz Capitulino <lcapitulino@xxxxxxxxxx> commit 8c6bab4f3874d31804a00782c48a8f244a0d3cc0 upstream. balloon_page_dequeue() 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. This bug was introduced in e2250429. Signed-off-by: Luiz Capitulino <lcapitulino@xxxxxxxxxx> Acked-by: Rafael Aquini <aquini@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/virtio/virtio_balloon.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -191,7 +191,8 @@ static void leak_balloon(struct virtio_b * 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 stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html