Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S937151AbdCJMa4 (ORCPT ); Fri, 10 Mar 2017 07:30:56 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:45232 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936307AbdCJMVQ (ORCPT ); Fri, 10 Mar 2017 07:21:16 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Willem de Bruijn" , "David S. Miller" , "Eric Dumazet" , "Dmitry Vyukov" Date: Fri, 10 Mar 2017 11:46:23 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 358/370] tun: read vnet_hdr_sz once In-Reply-To: X-SA-Exim-Connect-IP: 82.70.136.246 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1877 Lines: 62 3.16.42-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Willem de Bruijn [ Upstream commit e1edab87faf6ca30cd137e0795bc73aa9a9a22ec ] 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. Read this value once and cache locally, as it can be updated between the test and use (TOCTOU). Signed-off-by: Willem de Bruijn Reported-by: Dmitry Vyukov CC: Eric Dumazet Acked-by: Eric Dumazet Signed-off-by: David S. Miller [bwh: Backported to 3.16: - Use ACCESS_ONCE() instead of READ_ONCE() - Adjust context] Signed-off-by: Ben Hutchings --- drivers/net/tun.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -1037,9 +1037,11 @@ static ssize_t tun_get_user(struct tun_s } if (tun->flags & TUN_VNET_HDR) { - if (len < tun->vnet_hdr_sz) + int vnet_hdr_sz = ACCESS_ONCE(tun->vnet_hdr_sz); + + if (len < vnet_hdr_sz) return -EINVAL; - len -= tun->vnet_hdr_sz; + len -= vnet_hdr_sz; if (memcpy_fromiovecend((void *)&gso, iv, offset, sizeof(gso))) return -EFAULT; @@ -1050,7 +1052,7 @@ static ssize_t tun_get_user(struct tun_s if (gso.hdr_len > len) return -EINVAL; - offset += tun->vnet_hdr_sz; + offset += vnet_hdr_sz; } if ((tun->flags & TUN_TYPE_MASK) == TUN_TAP_DEV) { @@ -1233,7 +1235,7 @@ static ssize_t tun_put_user(struct tun_s vlan_hlen = VLAN_HLEN; if (tun->flags & TUN_VNET_HDR) - vnet_hdr_sz = tun->vnet_hdr_sz; + vnet_hdr_sz = ACCESS_ONCE(tun->vnet_hdr_sz); if (!(tun->flags & TUN_NO_PI)) { if ((len -= sizeof(pi)) < 0)