linux-kernel - Re: [V2 PATCH 2/9] macvtap: zerocopy: fix truesize underestimation

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Message-ID: <1337268512.10741.53.camel@oc3660625478.ibm.com>
Date:	Thu, 17 May 2012 08:28:32 -0700
From:	Shirley Ma <mashirle@...ibm.com>
To:	Jason Wang <jasowang@...hat.com>
Cc:	eric.dumazet@...il.com, mst@...hat.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, ebiederm@...ssion.com,
	davem@...emloft.net
Subject: Re: [V2 PATCH 2/9] macvtap: zerocopy: fix truesize underestimation

On Thu, 2012-05-17 at 10:59 +0800, Jason Wang wrote:
> Didn't see how this affact skb->len. And for truesize, I think they
> are 
> different, when the offset were not zero, the data in this vector
> were 
> divided into two parts. First part is copied into skb directly, and
> the 
> second were pinned from a whole userspace page by
> get_user_pages_fast(), 
> so we need count the whole page to the socket limit to prevent evil 
> application. 

What I meant that the code for skb->truesize has double added the first
offset if any left from that vector (partically copied into skb
directly, and then count pagesize which includes the offset (truesize +=
PAGE_SIZE)).

Thanks
Shirley

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