From patchwork Wed Jun 5 21:10:31 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Luiz Capitulino X-Patchwork-Id: 2674121 Return-Path: X-Original-To: patchwork-kvm@patchwork.kernel.org Delivered-To: patchwork-process-083081@patchwork2.kernel.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by patchwork2.kernel.org (Postfix) with ESMTP id 757A6DF264 for ; Wed, 5 Jun 2013 21:10:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932329Ab3FEVKf (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 Received: from int-mx12.intmail.prod.int.phx2.redhat.com (int-mx12.intmail.prod.int.phx2.redhat.com [10.5.11.25]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r55LAWKb018788 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Wed, 5 Jun 2013 17:10:32 -0400 Received: from localhost (ovpn-113-101.phx2.redhat.com [10.3.113.101]) by int-mx12.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id r55LAVZZ002545; Wed, 5 Jun 2013 17:10:32 -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 X-Scanned-By: MIMEDefang 2.68 on 10.5.11.25 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org 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 Acked-by: Rafael Aquini --- 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); }