linux-kernel - Re: [PATCH 3/6] macvtap: zerocopy: validate vector length before pinning user pages

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Date:	Tue, 17 Apr 2012 08:43:58 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Jason Wang <jasowang@...hat.com>, netdev@...r.kernel.org,
	xma@...ibm.com, davem@...emloft.net, linux-kernel@...r.kernel.org,
	ebiederm@...ssion.com
Subject: Re: [PATCH 3/6] macvtap: zerocopy: validate vector length before
 pinning user pages

On Tue, Apr 17, 2012 at 07:33:28AM +0200, Eric Dumazet wrote:
> On Mon, 2012-04-16 at 16:21 +0800, Jason Wang wrote:
> > Hi:
> > On 04/16/2012 02:53 PM, Eric Dumazet wrote:
> > 	if ((num_pages != size) ||
> > >>   		    (num_pages>  MAX_SKB_FRAGS - skb_shinfo(skb)->nr_frags))
> > >>
> > > Hi Jason
> > >
> > > Why is -EFAULT the right error code ?
> > 
> > E2BIG or is there any error code you prefer?
> 
> Might be good yes.
> 
> However it sounds strange user cant write any size he wants (and kernel
> needs to build several skbs to fulfill user request)

We never supported arbitrary length writes:
macvtap is exactly like packet sockets in this regard.

-- 
MST

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