From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B3101C43382 for ; Thu, 27 Sep 2018 23:50:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7189721731 for ; Thu, 27 Sep 2018 23:50:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7189721731 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728377AbeI1GLR (ORCPT ); Fri, 28 Sep 2018 02:11:17 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52714 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725957AbeI1GLR (ORCPT ); Fri, 28 Sep 2018 02:11:17 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 5E2223082134; Thu, 27 Sep 2018 23:50:28 +0000 (UTC) Received: from redhat.com (ovpn-123-154.rdu2.redhat.com [10.10.123.154]) by smtp.corp.redhat.com (Postfix) with ESMTP id 796C1600C1; Thu, 27 Sep 2018 23:50:24 +0000 (UTC) Date: Thu, 27 Sep 2018 19:50:24 -0400 From: "Michael S. Tsirkin" To: Jason Wang Cc: stefanha@redhat.com, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, sergei.shtylyov@cogentembedded.com Subject: Re: [PATCH net V2] vhost-vsock: fix use after free Message-ID: <20180927194734-mutt-send-email-mst@kernel.org> References: <20180927122204.4188-1-jasowang@redhat.com> <20180927123539-mutt-send-email-mst@kernel.org> <588ed28b-7e4b-9dc8-92ce-d75692836c9e@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <588ed28b-7e4b-9dc8-92ce-d75692836c9e@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.42]); Thu, 27 Sep 2018 23:50:28 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 28, 2018 at 07:37:37AM +0800, Jason Wang wrote: > > > On 2018年09月28日 01:04, Michael S. Tsirkin wrote: > > On Thu, Sep 27, 2018 at 08:22:04PM +0800, Jason Wang wrote: > > > The access of vsock is not protected by vhost_vsock_lock. This may > > > lead to use after free since vhost_vsock_dev_release() may free the > > > pointer at the same time. > > > > > > Fix this by holding the lock during the access. > > > > > > Reported-by:syzbot+e3e074963495f92a89ed@syzkaller.appspotmail.com > > > Fixes: 16320f363ae1 ("vhost-vsock: add pkt cancel capability") > > > Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko") > > > Cc: Stefan Hajnoczi > > > Signed-off-by: Jason Wang > > Wow is that really the best we can do? > > For net/stable, probably yes. > > > A global lock on a data path > > operation? > > It's already there, &vhost_vsock_lock? were is it takes on data path? > and the patch only increase the critical section. > > > Granted use after free is nasty but Stefan said he sees > > a way to fix it using a per socket refcount. He's on vacation > > until Oct 4 though ... > > > > Stefan has acked the pacth, so I think it's ok? We can do optimization for > -next on top. > > Thanks Well on high SMP serializing can drop performance as much as x100 so I'm not sure it's appropriate - seems to fix a bug but can introduce a regression. Let's see how does a proper fix look first? -- MST