netdev - Re: [PATCH] net: netem: fix skb length BUG_ON in __skb_to

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Date:   Tue, 26 Feb 2019 08:08:17 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Stephen Hemminger <stephen@...workplumber.org>,
        Sheng Lan <lansheng@...wei.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        netem@...ts.linux-foundation.org, xuhanbing@...wei.com,
        zhengshaoyu@...wei.com, jiqin.ji@...wei.com,
        liuzhiqiang26@...wei.com, yuehaibing@...wei.com
Subject: Re: [PATCH] net: netem: fix skb length BUG_ON in __skb_to_sgvec




On 02/26/2019 07:59 AM, Stephen Hemminger wrote:
> 
> 
> Maybe the fix is to stop TSO fragment from overwriting by doing something like:
> 
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index 730bc44dbad9..5fe91d0224f6 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -1856,7 +1856,7 @@ static int tso_fragment(struct sock *sk, enum tcp_queue tcp_queue,
>  	u8 flags;
>  
>  	/* All of a TSO frame must be composed of paged data.  */
> -	if (skb->len != skb->data_len)
> +	if (skb->len != skb->data_len || skb_cloned(skb))
>  		return tcp_fragment(sk, tcp_queue, skb, len, mss_now, gfp);
>  
>  	buff = sk_stream_alloc_skb(sk, 0, gfp, true);
> 


tso_fragment() is only called with packets that were not yet transmit.