linux-kernel - Re: [BUG] skb corruption and kernel panic at forwarding with fragmentation

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Message-ID: <CAM_iQpWsx6w2tFvSAy66M69FNi5iSp===EFCrO=4EPjy7y3iSg@mail.gmail.com>
Date:	Wed, 6 Jan 2016 11:59:23 -0800
From:	Cong Wang <xiyou.wangcong@...il.com>
To:	Konstantin Khlebnikov <koct9i@...il.com>
Cc:	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] skb corruption and kernel panic at forwarding with fragmentation

On Wed, Jan 6, 2016 at 11:15 AM, Konstantin Khlebnikov <koct9i@...il.com> wrote:
> Looks like this happens because ip_options_fragment() relies on
> correct ip options length in ip control block in skb. But in
> ip_finish_output_gso() control block in segments is reused by
> skb_gso_segment(). following ip_fragment() sees some garbage.
>
> In my case there was no ip options but length becomes non-zero and
> ip_options_fragment() picked some bytes from payload and decides to
> fill huge range with IPOPT_NOOP (1). One of that ones flipped nr_frags
> in skb_shared_info at the end of data =)
>

Hmm, it looks like SKB_GSO_CB should be cleared after skb_gso_segment()
since all the gso information should be saved in shared_info after it finishes.

Does a memset(0) on SKB_GSO_CB after skb_gso_segment() work as well?
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