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

Michael S. Tsirkin
2013-12-09T10:59:21Z

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.

> ---
> 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