From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Luiz Capitulino , Rafael Aquini , Andrew Morton , Rusty Russell Subject: [ 069/103] virtio_balloon: leak_balloon(): only tell host if we got pages deflated Date: Tue, 23 Jul 2013 15:26:20 -0700 Message-Id: <20130723220427.037760581@linuxfoundation.org> In-Reply-To: <20130723220418.532514378@linuxfoundation.org> References: <20130723220418.532514378@linuxfoundation.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Luiz Capitulino 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 Acked-by: Rafael Aquini Signed-off-by: Andrew Morton Signed-off-by: Rusty Russell Signed-off-by: Greg Kroah-Hartman --- 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); }