Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932352Ab3FEVKf (ORCPT ); Wed, 5 Jun 2013 17:10:35 -0400 Received: from mx1.redhat.com ([209.132.183.28]:2779 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932189Ab3FEVKe (ORCPT ); Wed, 5 Jun 2013 17:10:34 -0400 Date: Wed, 5 Jun 2013 17:10:31 -0400 From: Luiz Capitulino To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, aquini@redhat.com Subject: [PATCH] virtio_balloon: leak_balloon(): only tell host if we got pages deflated Message-ID: <20130605171031.7448deea@redhat.com> Organization: Red Hat Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1406 Lines: 39 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 --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/