From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753989AbeDJN14 (ORCPT ); Tue, 10 Apr 2018 09:27:56 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:57952 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752584AbeDJN1y (ORCPT ); Tue, 10 Apr 2018 09:27:54 -0400 Date: Tue, 10 Apr 2018 16:27:51 +0300 From: "Michael S. Tsirkin" To: Stefan Hajnoczi Cc: virtualization@lists.linux-foundation.org, syzkaller-bugs@googlegroups.com, Linus Torvalds , kvm@vger.kernel.org, jasowang@redhat.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org Subject: Re: [PATCH v2 1/2] vhost: fix vhost_vq_access_ok() log check Message-ID: <20180410162522-mutt-send-email-mst@kernel.org> References: <20180410052630.11270-1-stefanha@redhat.com> <20180410052630.11270-2-stefanha@redhat.com> <20180410161905-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180410161905-mutt-send-email-mst@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 10, 2018 at 04:22:35PM +0300, Michael S. Tsirkin wrote: > On Tue, Apr 10, 2018 at 01:26:29PM +0800, Stefan Hajnoczi wrote: > > Commit d65026c6c62e7d9616c8ceb5a53b68bcdc050525 ("vhost: validate log > > when IOTLB is enabled") introduced a regression. The logic was > > originally: > > > > if (vq->iotlb) > > return 1; > > return A && B; > > > > After the patch the short-circuit logic for A was inverted: > > > > if (A || vq->iotlb) > > return A; > > return B; > > > > This patch fixes the regression by rewriting the checks in the obvious > > way, no longer returning A when vq->iotlb is non-NULL (which is hard to > > understand). > > > > Reported-by: syzbot+65a84dde0214b0387ccd@syzkaller.appspotmail.com > > Cc: Jason Wang > > Signed-off-by: Stefan Hajnoczi > > This patch only makes sense after patch 2/2 is applied. > Otherwise the logic seems reversed below. > > Can you pls squash these two? Oh, in fact the patch is ok. This just goes to show that patch 2/2 is useful. But squashing is not required. Sorry about the noise. Acked-by: Michael S. Tsirkin Fixes: d65026c6c ("vhost: validate log when IOTLB is enabled") probably stable material since patch it fixes was queued to stable? > > --- > > drivers/vhost/vhost.c | 8 +++++--- > > 1 file changed, 5 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > > index 5320039671b7..93fd0c75b0d8 100644 > > --- a/drivers/vhost/vhost.c > > +++ b/drivers/vhost/vhost.c > > @@ -1244,10 +1244,12 @@ static int vq_log_access_ok(struct vhost_virtqueue *vq, > > /* Caller should have vq mutex and device mutex */ > > int vhost_vq_access_ok(struct vhost_virtqueue *vq) > > { > > - int ret = vq_log_access_ok(vq, vq->log_base); > > + if (!vq_log_access_ok(vq, vq->log_base)) > > + return 0; > > > > - if (ret || vq->iotlb) > > - return ret; > > + /* Access validation occurs at prefetch time with IOTLB */ > > + if (vq->iotlb) > > + return 1; > > > > return vq_access_ok(vq, vq->num, vq->desc, vq->avail, vq->used); > > } > > -- > > 2.14.3