Subject: Re: [PATCH net V2 2/2] macvtap: signal truncated packets

From: Jason Wang <[email-masked]>
Date: Wed, 11 Dec 2013 11:29:22 +0800

On 12/10/2013 11:29 PM, Michael S. Tsirkin wrote:
> On Tue, Dec 10, 2013 at 01:49:46PM +0800, Jason Wang wrote:
>> > macvtap_put_user() never return a value grater than iov length, this in fact
>> > bypasses the truncated checking in macvtap_recvmsg(). Fix this by always
>> > returning the size of packet plus the possible vlan header to let the trunca
>> > checking work.
>> > 
>> > Cc: Vlad Yasevich <[email-masked]>
>> > Cc: Zhi Yong Wu <[email-masked]>
>> > Cc: Michael S. Tsirkin <[email-masked]>
>> > Signed-off-by: Jason Wang <[email-masked]>
>> > ---
>> > Changes from v1:
>> > - increase total unconditionally
>> > - do not move the structure veth out of the vlan handling block
>> > ---
>> >  drivers/net/macvtap.c | 19 ++++++++++---------
>> >  1 file changed, 10 insertions(+), 9 deletions(-)
>> > 
>> > diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
>> > index 957cc5c..ded4b2c 100644
>> > --- a/drivers/net/macvtap.c
>> > +++ b/drivers/net/macvtap.c
>> > @@ -770,7 +770,7 @@ static ssize_t macvtap_put_user(struct macvtap_queue *q,
>> >  	int ret;
>> >  	int vnet_hdr_len = 0;
>> >  	int vlan_offset = 0;
>> > -	int copied;
>> > +	int copied, offset;
>> >  
>> >  	if (q->flags & IFF_VNET_HDR) {
>> >  		struct virtio_net_hdr vnet_hdr;
>> > @@ -785,7 +785,8 @@ static ssize_t macvtap_put_user(struct macvtap_queue *q,
>> >  		if (memcpy_toiovecend(iv, (void *)&vnet_hdr, 0, sizeof(vnet_hdr)))
>> >  			return -EFAULT;
>> >  	}
>> > -	copied = vnet_hdr_len;
>> > +	offset = copied = vnet_hdr_len;
>> > +	copied += skb->len;
>> >  
>> >  	if (!vlan_tx_tag_present(skb))
>> >  		len = min_t(int, skb->len, len);
>> > @@ -800,24 +801,24 @@ static ssize_t macvtap_put_user(struct macvtap_queue *q,
>> >  
>> >  		vlan_offset = offsetof(struct vlan_ethhdr, h_vlan_proto);
>> >  		len = min_t(int, skb->len + VLAN_HLEN, len);
>> > +		copied += VLAN_HLEN;
>> >  
>> >  		copy = min_t(int, vlan_offset, len);
>> > -		ret = skb_copy_datagram_const_iovec(skb, 0, iv, copied, copy);
>> > +		ret = skb_copy_datagram_const_iovec(skb, 0, iv, offset, copy);
>> >  		len -= copy;
>> > -		copied += copy;
>> > +		offset += copy;
>> >  		if (ret || !len)
>> >  			goto done;
>> >  
>> >  		copy = min_t(int, sizeof(veth), len);
>> > -		ret = memcpy_toiovecend(iv, (void *)&veth, copied, copy);
>> > +		ret = memcpy_toiovecend(iv, (void *)&veth, offset, copy);
>> >  		len -= copy;
>> > -		copied += copy;
>> > +		offset += copy;
>> >  		if (ret || !len)
>> >  			goto done;
>> >  	}
>> >  
>> > -	ret = skb_copy_datagram_const_iovec(skb, vlan_offset, iv, copied, len);
>> > -	copied += len;
>> > +	ret = skb_copy_datagram_const_iovec(skb, vlan_offset, iv, offset, len);
>> >  
>> >  done:
>> >  	return ret ? ret : copied;
> I commented on this already. copied is how much we copied,
> so its value is correct.
> You want to name the new one total_len or something along
> these lines and return it.
>

Ok, to be same with tun, I will use "total" in V3.

Thanks