netdev - Re: [PATCH V2] ipv6 mcast: Fix incorrect use of pskb_may

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Date:	Thu, 27 Dec 2012 01:40:07 +0900
From:	YOSHIFUJI Hideaki <yoshfuji@...ux-ipv6.org>
To:	Eric Dumazet <eric.dumazet@...il.com>,
	David Miller <davem@...emloft.net>
CC:	"'netdev@...r.kernel.org'" <netdev@...r.kernel.org>,
	YOSHIFUJI Hideaki <yoshfuji@...ux-ipv6.org>
Subject: Re: [PATCH V2] ipv6 mcast: Fix incorrect use of pskb_may_pull().

Eric Dumazet wrote:
> On Wed, 2012-12-26 at 12:12 +0900, YOSHIFUJI Hideaki wrote:
>> pskb_may_pull(skb, len) ensures that len bytes from skb->data
>> are available in a linear array.  When pskb_may_pull() is
>> being used multiple times for the same buffer without
>> skb_pull(), the length is not accumulated.
:
>> @@ -1124,7 +1124,7 @@ int igmp6_event_query(struct sk_buff *skb)
>>  	int mark = 0;
>>  	int len;
>>  
>> -	if (!pskb_may_pull(skb, sizeof(struct in6_addr)))
>> +	if (!pskb_may_pull(skb, sizeof(struct icmp6hdr) + sizeof(struct in6_addr)))
>>  		return -EINVAL;
>>  
> 
> I am a bit confused by your patch.
> 
> igmp6_event_query() is called from icmpv6_rcv() _after_ 
> 
> pskb_pull(skb, sizeof(*hdr);
> 
> (hdr being struct icmp6hdr)
> 
> So this patch is wrong IMHO

Argh..I agree.  I withdraw this one.

--yoshfuji
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