Subject: Re: [PATCH] llc: fix skb size for test responses

From: Joonwoo Park <[email-masked]>
Date: Tue, 26 Feb 2008 16:00:25 +0900

On Sun, Feb 24, 2008 at 11:07:58AM -0800, Jim Westfall wrote:
> Hi
> 
> The llc test command is used for a layer2 ping and contains a variable 
> length payload that we must include in the response.  Use the size of the 
> received skb as the size of the skb we must allocate to hold the payload. 
> 
> This resolved an skb_over_panic(), when trying to copy the payload into 
> what was a hard coded skb of size 128.
> 
> Signed-off-by: Jim Westfall <[email-masked]>
> 
> diff -urp linux-2.6.24.2.org/net/llc/llc_s_ac.c linux-2.6.24.2/net/llc/llc_s_ac.c
> --- linux-2.6.24.2.org/net/llc/llc_s_ac.c	2008-02-10 21:51:11.000000000 -0800
> +++ linux-2.6.24.2/net/llc/llc_s_ac.c	2008-02-24 10:15:02.000000000 -0800
> @@ -148,9 +148,18 @@ int llc_sap_action_send_test_r(struct ll
>  	llc_pdu_decode_sa(skb, mac_da);
>  	llc_pdu_decode_da(skb, mac_sa);
>  	llc_pdu_decode_ssap(skb, &dsap);
> -	nskb = llc_alloc_frame(NULL, skb->dev);
> +	nskb = alloc_skb(skb->end - skb->head, GFP_ATOMIC);

Jim,

Not enough.
Because of 'skb_reserve(nskb, 50)', we need additional 50bytes.

> +
>  	if (!nskb)
>  		goto out;
> +
> +	skb_reset_mac_header(nskb);
> +	skb_reserve(nskb, 50);
> +	skb_reset_network_header(nskb);
> +	skb_reset_transport_header(nskb);
> +	nskb->protocol = htons(ETH_P_802_2);
> +	nskb->dev = skb->dev;
> +
>  	llc_pdu_header_init(nskb, LLC_PDU_TYPE_U, sap->laddr.lsap, dsap,
>  			    LLC_PDU_RSP);
>  	llc_pdu_init_as_test_rsp(nskb, skb);
> diff -urp linux-2.6.24.2.org/net/llc/llc_station.c linux-2.6.24.2/net/llc/llc_station.c
> --- linux-2.6.24.2.org/net/llc/llc_station.c	2008-02-10 21:51:11.000000000 -0800
> +++ linux-2.6.24.2/net/llc/llc_station.c	2008-02-24 10:10:01.000000000 -0800
> @@ -298,10 +298,18 @@ static int llc_station_ac_send_test_r(st
>  {
>  	u8 mac_da[ETH_ALEN], dsap;
>  	int rc = 1;
> -	struct sk_buff *nskb = llc_alloc_frame(NULL, skb->dev);
> +	struct sk_buff *nskb = alloc_skb(skb->end - skb->head, GFP_ATOMIC);

Also here.

>  
>  	if (!nskb)
>  		goto out;
> +
> +	skb_reset_mac_header(nskb);
> +	skb_reserve(nskb, 50);
> +	skb_reset_network_header(nskb);
> +	skb_reset_transport_header(nskb);
> +	nskb->protocol = htons(ETH_P_802_2);
> +	nskb->dev = skb->dev;
> +
>  	rc = 0;
>  	llc_pdu_decode_sa(skb, mac_da);
>  	llc_pdu_decode_ssap(skb, &dsap);
> 

Thanks,
Joonwoo

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