From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A4823C43381 for ; Sat, 30 Mar 2019 07:30:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7B0C3218A6 for ; Sat, 30 Mar 2019 07:30:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730174AbfC3HaM (ORCPT ); Sat, 30 Mar 2019 03:30:12 -0400 Received: from szxga05-in.huawei.com ([45.249.212.191]:5764 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726325AbfC3HaM (ORCPT ); Sat, 30 Mar 2019 03:30:12 -0400 Received: from DGGEMS405-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 4692232C626D7813BA63; Sat, 30 Mar 2019 15:30:10 +0800 (CST) Received: from [127.0.0.1] (10.184.191.73) by DGGEMS405-HUB.china.huawei.com (10.3.19.205) with Microsoft SMTP Server id 14.3.408.0; Sat, 30 Mar 2019 15:29:55 +0800 To: , , , , From: hujunwei Subject: [PATCH net] ipv6: Fix dangling pointer when ipv6 fragment CC: , , Message-ID: Date: Sat, 30 Mar 2019 15:29:32 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Content-Language: en-US X-Originating-IP: [10.184.191.73] X-CFilter-Loop: Reflected Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Junwei Hu At the beginning of ip6_fragment func, the prevhdr pointer is obtained in the ip6_find_1stfragopt func. However, all the pointers pointing into skb header may change when calling skb_checksum_help func with skb->ip_summed = CHECKSUM_PARTIAL condition. The prevhdr pointe will be dangling if it is not reloaded after calling __skb_linearize func in skb_checksum_help func. Here, I add a variable, nexthdr_offset, to evaluate the offset, which does not changes even after calling __skb_linearize func. Fixes: 405c92f7a541 ("ipv6: add defensive check for CHECKSUM_PARTIAL skbs in ip_fragment") Signed-off-by: Junwei Hu Reported-by: Wenhao Zhang Reviewed-by: Zhiqiang Liu ---  net/ipv6/ip6_output.c | 4 ++++  1 file changed, 4 insertions(+) diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index edbd12067170..6db3c60b3b66 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -606,12 +606,14 @@ int ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,      __be32 frag_id;      int ptr, offset = 0, err = 0;      u8 *prevhdr, nexthdr = 0; +    u8 nexthdr_offset;        err = ip6_find_1stfragopt(skb, &prevhdr);      if (err < 0)          goto fail;      hlen = err;      nexthdr = *prevhdr; +    nexthdr_offset = prevhdr - skb_network_header(skb);        mtu = ip6_skb_dst_mtu(skb);   @@ -646,6 +648,8 @@ int ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,          (err = skb_checksum_help(skb)))          goto fail;   +    prevhdr = skb_network_header(skb) + nexthdr_offset; +      hroom = LL_RESERVED_SPACE(rt->dst.dev);      if (skb_has_frag_list(skb)) {          unsigned int first_len = skb_pagelen(skb); -- 2.19.1