From patchwork Fri May 11 17:24:25 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Willem de Bruijn X-Patchwork-Id: 912090 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming-netdev@ozlabs.org Delivered-To: patchwork-incoming-netdev@ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=netdev-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.b="rMci7SzV"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 40jH5Z10xtz9s19 for ; Sat, 12 May 2018 03:24:34 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751400AbeEKRYa (ORCPT ); Fri, 11 May 2018 13:24:30 -0400 Received: from mail-qk0-f194.google.com ([209.85.220.194]:35669 "EHLO mail-qk0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751378AbeEKRY3 (ORCPT ); Fri, 11 May 2018 13:24:29 -0400 Received: by mail-qk0-f194.google.com with SMTP id c137-v6so4960595qkg.2 for ; Fri, 11 May 2018 10:24:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id; bh=Uayy4rrV4g51U74U/1YxvBYDytzNDyb67DSN/+aBaW0=; b=rMci7SzVApihNJFF37Z2fa9lH/niZSpqiTXbbaadQ7GbdYJ+//yU8Ri3fglNm1JGEV +845/KXDDIaq4LIDlcoi1iYV8nVfr5BN9ka9HkqUUsYjwRUy812HcMxd6niiziql1GbC WFEbeaaJx6PkBAXJLu6PDccu1wcN0HqLA6Qecab9bh2GVGCe+YsQHpBW+jj0MqeP8lWL vELNuoA9rHFl04mgQfA6B5Dz4I7zMCraWGPwshWdD6tk7L5+2P7UAFmlbIkUaj42aD37 uSR56UVUlqoH36Afw/VGS4U5fwx4TPI5JaV70z7mB5t7id9Xi8HV4crfoJS5v/Q89Wlk eUhA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=Uayy4rrV4g51U74U/1YxvBYDytzNDyb67DSN/+aBaW0=; b=ifF6uqJGgKiOM92/TGNEiyB+yEMO9lnsfNsmWvTYvDgNjdd2e4KNu1za7V4H0cGs5b tl8ewD9RBMx4Z6pRFBKFH904bomxT9CHvAq3uj4g88RwOFlfZpSXnMIvOMHp3LDSUP2R +dgpldBlopnMNl/8ETBp6naKPfeeK7hl0TqmylL6SeFjnJF+QvKkvKKP/3zyAE1NYWEh oe6Zg29uX8LzLTZx3CaslemRb/sEcTL2rrdueBoY2zAi1sI1706aUkD8EGbS0XX6BPn9 RPzLrPueQVQ+95HT4hYVABRKynt03p2klecrxiOAGAcVq7iEEn5zfRyrVSKE40p9/0UZ RdWg== X-Gm-Message-State: ALKqPwcL8nxtGKG4i/x5rWP+mWxmbzH/FlqeRmGV95ync9mVZ55toLjY g3SNbJUYFkGRhCb9gR1N/SQIxVJo X-Google-Smtp-Source: AB8JxZrxda5ZOKPRudTrY0P8/wGJ6gG09t6p2gZRvkeNI+Mt8zEnB/XTgniUpUNl2sOYk1bNo266kQ== X-Received: by 2002:a37:15d8:: with SMTP id 85-v6mr5913791qkv.150.1526059467800; Fri, 11 May 2018 10:24:27 -0700 (PDT) Received: from willemb1.nyc.corp.google.com ([2620:0:1003:315:3fa1:a34c:1128:1d39]) by smtp.gmail.com with ESMTPSA id k188-v6sm2649617qke.69.2018.05.11.10.24.27 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 11 May 2018 10:24:27 -0700 (PDT) From: Willem de Bruijn To: netdev@vger.kernel.org Cc: davem@davemloft.net, eric.dumazet@gmail.com, Willem de Bruijn Subject: [PATCH net] packet: in packet_snd start writing at link layer allocation Date: Fri, 11 May 2018 13:24:25 -0400 Message-Id: <20180511172425.213901-1-willemdebruijn.kernel@gmail.com> X-Mailer: git-send-email 2.17.0.441.gb46fe60e1d-goog Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Willem de Bruijn Packet sockets allow construction of packets shorter than dev->hard_header_len to accommodate protocols with variable length link layer headers. These packets are padded to dev->hard_header_len, because some device drivers interpret that as a minimum packet size. packet_snd reserves dev->hard_header_len bytes on allocation. SOCK_DGRAM sockets call skb_push in dev_hard_header() to ensure that link layer headers are stored in the reserved range. SOCK_RAW sockets do the same in tpacket_snd, but not in packet_snd. Syzbot was able to send a zero byte packet to a device with massive 116B link layer header, causing padding to cross over into skb_shinfo. Fix this by writing from the start of the llheader reserved range also in the case of packet_snd/SOCK_RAW. Update skb_set_network_header to the new offset. This also corrects it for SOCK_DGRAM, where it incorrectly double counted reserve due to the skb_push in dev_hard_header. Fixes: 9ed988cd5915 ("packet: validate variable length ll headers") Reported-by: syzbot+71d74a5406d02057d559@syzkaller.appspotmail.com Signed-off-by: Willem de Bruijn --- net/packet/af_packet.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 01f3515cada0d..e9422fe451793 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -2903,13 +2903,15 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len) if (skb == NULL) goto out_unlock; - skb_set_network_header(skb, reserve); + skb_reset_network_header(skb); err = -EINVAL; if (sock->type == SOCK_DGRAM) { offset = dev_hard_header(skb, dev, ntohs(proto), addr, NULL, len); if (unlikely(offset < 0)) goto out_free; + } else if (reserve) { + skb_push(skb, reserve); } /* Returns -EFAULT on error */