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

Jason Wang
2013-12-10T05:42:19Z

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@gmail.com>
>> Cc: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
>> Signed-off-by: Jason Wang <jasowang@redhat.com>
> 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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