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

[Jason Wang]

On 12/09/2013 07:02 PM, Michael S. Tsirkin wrote:
> On Mon, Dec 09, 2013 at 06:25:17PM +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 truncated
>> checking work.
>>
>> Cc: Vlad Yasevich <vyasevich@xxxxxxxxx>
>> Cc: Zhi Yong Wu <wuzhy@xxxxxxxxxxxxxxxxxx>
>> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
> Same comments as for tun really, but here it's also
> kind of ugly to call a variable copied if we don't copy.
>
> Also, maybe we should name the variable "copied" for tun,
> this would make the code more similar.

Agree, but better with a separate patch for net-next.
>> ---
>> The patch is needed for stable.
>> ---
>>  drivers/net/macvtap.c | 27 ++++++++++++++-------------
>>  1 file changed, 14 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
>> index 957cc5c..7544a0c 100644
>> --- a/drivers/net/macvtap.c
>> +++ b/drivers/net/macvtap.c
>> @@ -767,10 +767,14 @@ static ssize_t macvtap_put_user(struct macvtap_queue *q,
>>  				const struct sk_buff *skb,
>>  				const struct iovec *iv, int len)
>>  {
>> -	int ret;
>> +	int ret, off;
>>  	int vnet_hdr_len = 0;
>>  	int vlan_offset = 0;
>>  	int copied;
>> +	struct {
>> +		__be16 h_vlan_proto;
>> +		__be16 h_vlan_TCI;
>> +	} veth;
>>  
>>  	if (q->flags & IFF_VNET_HDR) {
>>  		struct virtio_net_hdr vnet_hdr;
>> @@ -785,16 +789,13 @@ 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;
>> +	off = copied = vnet_hdr_len;
>>  
>>  	if (!vlan_tx_tag_present(skb))
>>  		len = min_t(int, skb->len, len);
>>  	else {
>>  		int copy;
>> -		struct {
>> -			__be16 h_vlan_proto;
>> -			__be16 h_vlan_TCI;
>> -		} veth;
>> +
>>  		veth.h_vlan_proto = skb->vlan_proto;
>>  		veth.h_vlan_TCI = htons(vlan_tx_tag_get(skb));
>>  
>> @@ -802,22 +803,22 @@ static ssize_t macvtap_put_user(struct macvtap_queue *q,
>>  		len = min_t(int, skb->len + VLAN_HLEN, len);
>>  
>>  		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, off, copy);
>>  		len -= copy;
>> -		copied += copy;
>> +		off += 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, off, copy);
>>  		len -= copy;
>> -		copied += copy;
>> +		off += 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, off, len);
>> +	copied += skb->len + (vlan_offset ? sizeof(veth) : 0);
>>  
>>  done:
>>  	return ret ? ret : copied;
>> @@ -875,7 +876,7 @@ static ssize_t macvtap_aio_read(struct kiocb *iocb, const struct iovec *iv,
>>  	}
>>  
>>  	ret = macvtap_do_read(q, iocb, iv, len, file->f_flags & O_NONBLOCK);
>> -	ret = min_t(ssize_t, ret, len); /* XXX copied from tun.c. Why? */
>> +	ret = min_t(ssize_t, ret, len);
>>  	if (ret > 0)
>>  		iocb->ki_pos = ret;
>>  out:
>
>
>> -- 
>> 1.8.3.2
> --
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