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Date:   Wed, 03 Apr 2019 21:43:14 -0700 (PDT)
Message-Id: <20190403.214314.643123707100892779.davem@davemloft.net>
To:     hujunwei4@huawei.com
Cc:     kuznet@ms2.inr.ac.ru, yoshfuji@linux-ipv6.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        mingfangsen@huawei.com, liuzhiqiang26@huawei.com
Subject: Re: [PATCH v4 net] ipv6: Fix dangling pointer when ipv6 fragment
From:   David Miller <davem@davemloft.net>
In-Reply-To: <aaccfa09-8acf-e247-ab71-3d6ec3803f55@huawei.com>
References: <aaccfa09-8acf-e247-ab71-3d6ec3803f55@huawei.com>
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From: hujunwei <hujunwei4@huawei.com>
Date: Tue, 2 Apr 2019 19:38:04 +0800

> From: Junwei Hu <hujunwei4@huawei.com>
> 
> 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 <hujunwei4@huawei.com>
> Reported-by: Wenhao Zhang <zhangwenhao8@huawei.com>
> Reported-by: syzbot+e8ce541d095e486074fc@syzkaller.appspotmail.com
> Reviewed-by: Zhiqiang Liu <liuzhiqiang26@huawei.com>
> Acked-by: Martin KaFai Lau <kafai@fb.com>
> ---
> V3->V4:
> - fix build warning

Applied and queued up for -stable.