From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:60208 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752659AbeDQQAq (ORCPT ); Tue, 17 Apr 2018 12:00:46 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+65a84dde0214b0387ccd@syzkaller.appspotmail.com, Jason Wang , Stefan Hajnoczi , "Michael S. Tsirkin" , "David S. Miller" Subject: [PATCH 4.16 04/68] vhost: fix vhost_vq_access_ok() log check Date: Tue, 17 Apr 2018 17:57:17 +0200 Message-Id: <20180417155749.519346445@linuxfoundation.org> In-Reply-To: <20180417155749.341779147@linuxfoundation.org> References: <20180417155749.341779147@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Stefan Hajnoczi [ Upstream commit d14d2b78090c7de0557362b26a4ca591aa6a9faa ] 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 Acked-by: Michael S. Tsirkin Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- drivers/vhost/vhost.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -1244,10 +1244,12 @@ static int vq_log_access_ok(struct vhost /* 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); }