Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753870AbdFSS4M (ORCPT + 2 others); Mon, 19 Jun 2017 14:56:12 -0400 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:52618 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753906AbdFSSiL (ORCPT ); Mon, 19 Jun 2017 14:38:11 -0400 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, linux@roeck-us.net Cc: Willem de Bruijn , "David S . Miller" , Willy Tarreau Subject: [PATCH 3.10 144/268] macvtap: read vnet_hdr_size once Date: Mon, 19 Jun 2017 20:30:43 +0200 Message-Id: <1497897167-14556-145-git-send-email-w@1wt.eu> X-Mailer: git-send-email 2.8.0.rc2.1.gbe9624a In-Reply-To: <1497897167-14556-1-git-send-email-w@1wt.eu> References: <1497897167-14556-1-git-send-email-w@1wt.eu> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: From: Willem de Bruijn commit 837585a5375c38d40361cfe64e6fd11e1addb936 upstream. When IFF_VNET_HDR is enabled, a virtio_net header must precede data. Data length is verified to be greater than or equal to expected header length tun->vnet_hdr_sz before copying. Macvtap functions read the value once, but unless READ_ONCE is used, the compiler may ignore this and read multiple times. Enforce a single read and locally cached value to avoid updates between test and use. Signed-off-by: Willem de Bruijn Suggested-by: Eric Dumazet Acked-by: Eric Dumazet Signed-off-by: David S. Miller [wt: s/READ_ONCE/ACCESS_ONCE] Signed-off-by: Willy Tarreau --- drivers/net/macvtap.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c index 8fc46fc..1c51abb 100644 --- a/drivers/net/macvtap.c +++ b/drivers/net/macvtap.c @@ -678,7 +678,7 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m, size_t linear; if (q->flags & IFF_VNET_HDR) { - vnet_hdr_len = q->vnet_hdr_sz; + vnet_hdr_len = ACCESS_ONCE(q->vnet_hdr_sz); err = -EINVAL; if (len < vnet_hdr_len) @@ -809,7 +809,7 @@ static ssize_t macvtap_put_user(struct macvtap_queue *q, if (q->flags & IFF_VNET_HDR) { struct virtio_net_hdr vnet_hdr; - vnet_hdr_len = q->vnet_hdr_sz; + vnet_hdr_len = ACCESS_ONCE(q->vnet_hdr_sz); if ((len -= vnet_hdr_len) < 0) return -EINVAL; -- 2.8.0.rc2.1.gbe9624a