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=-6.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 AE98CC282CE for ; Wed, 24 Apr 2019 17:19:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7CB4521907 for ; Wed, 24 Apr 2019 17:19:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556126345; bh=WMsuK4oBxUq3ToKRclrgQHMxfLV042jFlZ6LgHOaE6s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=uWDFRDPpev91r+c9VNm9w/Xo7NFLxMcvu2JV5lRA2G3wW5/TkPqmWDA+sSVqoSSNZ XBqhedjbUWlYS9BbJOYweNiReSyGXRdKGPZxkD7/31YgdKNiRpxFJA8c3ApJvzZZet SVyTpSL0CA8a5cpe8RFpkERBxdivsrE+w1QUE9nQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388934AbfDXRTE (ORCPT ); Wed, 24 Apr 2019 13:19:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:44162 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388921AbfDXRTA (ORCPT ); Wed, 24 Apr 2019 13:19:00 -0400 Received: from localhost (62-193-50-229.as16211.net [62.193.50.229]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 39E26218B0; Wed, 24 Apr 2019 17:18:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556126339; bh=WMsuK4oBxUq3ToKRclrgQHMxfLV042jFlZ6LgHOaE6s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VjHgzX+wJ6XjqNdanIKFkdWNLAcmVcyem+HxFSnUYH18AH4kWwSJDLV4chZR5TNWx 784Y/k7b2huQVIBZ8xHa8m6FBG7LVXPzqaSJjF7ualJv0Xq29QRTGqQWW/eW73SlBL ho6hrih80dGv96xi1pA9n0bZJCMubRmQMQZwXkYY= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Junwei Hu , Wenhao Zhang , syzbot+e8ce541d095e486074fc@syzkaller.appspotmail.com, Zhiqiang Liu , Martin KaFai Lau , "David S. Miller" Subject: [PATCH 4.4 077/168] ipv6: Fix dangling pointer when ipv6 fragment Date: Wed, 24 Apr 2019 19:08:41 +0200 Message-Id: <20190424170928.504455385@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190424170923.452349382@linuxfoundation.org> References: <20190424170923.452349382@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Junwei Hu [ Upstream commit ef0efcd3bd3fd0589732b67fb586ffd3c8705806 ] 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 Reported-by: syzbot+e8ce541d095e486074fc@syzkaller.appspotmail.com Reviewed-by: Zhiqiang Liu Acked-by: Martin KaFai Lau Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv6/ip6_output.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -575,7 +575,7 @@ int ip6_fragment(struct net *net, struct inet6_sk(skb->sk) : NULL; struct ipv6hdr *tmp_hdr; struct frag_hdr *fh; - unsigned int mtu, hlen, left, len; + unsigned int mtu, hlen, left, len, nexthdr_offset; int hroom, troom; __be32 frag_id; int ptr, offset = 0, err = 0; @@ -586,6 +586,7 @@ int ip6_fragment(struct net *net, struct goto fail; hlen = err; nexthdr = *prevhdr; + nexthdr_offset = prevhdr - skb_network_header(skb); mtu = ip6_skb_dst_mtu(skb); @@ -620,6 +621,7 @@ int ip6_fragment(struct net *net, struct (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)) { int first_len = skb_pagelen(skb);