netdev - Re: [PATCH 1/2] ppp_generic: pull 2 bytes so that PPP

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Message-ID: <e85216b167313bb2bd46f5990ed468f5b67a1ad8@8b5064a13e22126c1b9329f0dc35b8915774b7c3.invalid>
Date:	Mon, 3 May 2010 12:50:04 +0100
From:	"Simon Arlott" <simon@...e.lp0.eu>
To:	"David Miller" <davem@...emloft.net>
Cc:	netdev@...r.kernel.org, paulus@...ba.org, linux-ppp@...r.kernel.org
Subject: Re: [PATCH 1/2] ppp_generic: pull 2 bytes so that PPP_PROTO(skb) 
 is valid

On Mon, May 3, 2010 07:25, David Miller wrote:
> From: Simon Arlott <simon@...e.lp0.eu>
> Date: Fri, 30 Apr 2010 19:41:17 +0100
>> @@ -1572,8 +1572,18 @@ ppp_input(struct ppp_channel *chan, struct sk_buff *skb)
>>  		return;
>>  	}
>>
>> -	proto = PPP_PROTO(skb);
>> +
>>  	read_lock_bh(&pch->upl);
>> +	if (!pskb_may_pull(skb, 2)) {
>
> This makes the skb->len == 0 test at the beginning completely redundant.
>
> Put your pskb_may_pull(skb, 2) call there and remove the skb->len==0
> check entirely.

If I move pskb_may_pull(skb, 2) up to where skb->len == 0 is then it can't
increment rx_length_errors because it doesn't have the read lock on pch->upl,
so I can only remove the redundant skb->len == 0 if that error count is to
remain.

Updated patch attached.

-- 
Simon Arlott
Download attachment "
 "0001-ppp_generic-pull-2-bytes-so-that-PPP_PROTO-skb-is-va.patch"" of type "application/octet-stream" (2627 bytes)