From patchwork Thu Jan 21 17:01:21 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefano Stabellini X-Patchwork-Id: 8083461 Return-Path: X-Original-To: patchwork-qemu-devel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 44D75BEEE5 for ; Thu, 21 Jan 2016 17:06:19 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id D0BE9204A9 for ; Thu, 21 Jan 2016 17:06:13 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 389A7200FE for ; Thu, 21 Jan 2016 17:06:13 +0000 (UTC) Received: from localhost ([::1]:48965 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aMIgW-0003Kx-Je for patchwork-qemu-devel@patchwork.kernel.org; Thu, 21 Jan 2016 12:06:12 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47868) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aMIdY-0005nJ-Jo for qemu-devel@nongnu.org; Thu, 21 Jan 2016 12:03:11 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aMIdX-00023d-FQ for qemu-devel@nongnu.org; Thu, 21 Jan 2016 12:03:08 -0500 Received: from smtp02.citrix.com ([66.165.176.63]:51214) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aMIdX-00023R-3G for qemu-devel@nongnu.org; Thu, 21 Jan 2016 12:03:07 -0500 X-IronPort-AV: E=Sophos;i="5.22,326,1449532800"; d="scan'208";a="333120552" From: Stefano Stabellini To: Date: Thu, 21 Jan 2016 17:01:21 +0000 Message-ID: <1453395690-32660-2-git-send-email-stefano.stabellini@eu.citrix.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: References: MIME-Version: 1.0 X-DLP: MIA1 X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 66.165.176.63 Cc: xen-devel@lists.xensource.com, qemu-devel@nongnu.org, Stefano Stabellini Subject: [Qemu-devel] [PULL 02/11] xenfb.c: avoid expensive loops when prod <= out_cons X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP If the frontend sets out_cons to a value higher than out_prod, it will cause xenfb_handle_events to loop about 2^32 times. Avoid that by using better checks at the beginning of the function. Signed-off-by: Stefano Stabellini Reported-by: Ling Liu --- hw/display/xenfb.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/hw/display/xenfb.c b/hw/display/xenfb.c index 4e2a27a..8eb3046 100644 --- a/hw/display/xenfb.c +++ b/hw/display/xenfb.c @@ -789,8 +789,9 @@ static void xenfb_handle_events(struct XenFB *xenfb) prod = page->out_prod; out_cons = page->out_cons; - if (prod == out_cons) - return; + if (prod - out_cons >= XENFB_OUT_RING_LEN) { + return; + } xen_rmb(); /* ensure we see ring contents up to prod */ for (cons = out_cons; cons != prod; cons++) { union xenfb_out_event *event = &XENFB_OUT_RING_REF(page, cons);