From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752921AbeDKCf6 (ORCPT ); Tue, 10 Apr 2018 22:35:58 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:54078 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752850AbeDKCf4 (ORCPT ); Tue, 10 Apr 2018 22:35:56 -0400 From: Stefan Hajnoczi To: virtualization@lists.linux-foundation.org Cc: Linus Torvalds , jasowang@redhat.com, mst@redhat.com, netdev@vger.kernel.org, syzkaller-bugs@googlegroups.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Stefan Hajnoczi Subject: [PATCH v3 1/2] vhost: fix vhost_vq_access_ok() log check Date: Wed, 11 Apr 2018 10:35:40 +0800 Message-Id: <20180411023541.15776-2-stefanha@redhat.com> In-Reply-To: <20180411023541.15776-1-stefanha@redhat.com> References: <20180411023541.15776-1-stefanha@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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 bec722e41f58..fc805b7fad9d 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