netdev - Re: v4.14-rc2/arm64 kernel BUG at net/core/skbuff.c:2626

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Date:   Mon, 2 Oct 2017 16:03:50 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     Eric Dumazet <edumazet@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        linux-arm-kernel@...ts.infradead.org,
        syzkaller <syzkaller@...glegroups.com>,
        "David S. Miller" <davem@...emloft.net>,
        Willem de Bruijn <willemb@...gle.com>
Subject: Re: v4.14-rc2/arm64 kernel BUG at net/core/skbuff.c:2626

On Mon, Oct 02, 2017 at 07:48:28AM -0700, Eric Dumazet wrote:
> Please try the following fool proof patch.
> 
> This is what I had in my local tree back in August but could not
> conclude on the syzkaller bug I was working on.

Thanks, I'll give this a go shortly.

I'm currently minimizing the Syzkaller log so that I can trigger the
issue more quickly (and have some confidence in a Tested-by)!

Thanks,
Mark.

> diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
> index 681e33998e03b609fdca83a83e0fc62a3fee8c39..e51d777797a927058760a1ab7af00579f7488cb5 100644
> --- a/net/ipv4/icmp.c
> +++ b/net/ipv4/icmp.c
> @@ -732,7 +732,8 @@ void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info)
>  		room = 576;
>  	room -= sizeof(struct iphdr) + icmp_param.replyopts.opt.opt.optlen;
>  	room -= sizeof(struct icmphdr);
> -
> +	if (room < 0)
> +		goto ende;
>  	icmp_param.data_len = skb_in->len - icmp_param.offset;
>  	if (icmp_param.data_len > room)
>  		icmp_param.data_len = room;
> 
> 
>