virtio-net: xsk: rx: fix the frame's length check

Summary

In the Linux kernel, the following vulnerability has been resolved: virtio-net: xsk: rx: fix the frame's length check When calling buf_to_xdp, the len argument is the frame data's length without virtio header's length (vi->hdr_len). We check that len with xsk_pool_get_rx_frame_size() + vi->hdr_len to ensure the provided len does not larger than the allocated chunk size. The additional vi->hdr_len is because in virtnet_add_recvbuf_xsk, we use part of XDP_PACKET_HEADROOM for virtio header and ask the vhost to start placing data from hard_start + XDP_PACKET_HEADROOM - vi->hdr_len not hard_start + XDP_PACKET_HEADROOM But the first buffer has virtio_header, so the maximum frame's length in the first buffer can only be xsk_pool_get_rx_frame_size() not xsk_pool_get_rx_frame_size() + vi->hdr_len like in the current check. This commit adds an additional argument to buf_to_xdp differentiate between the first buffer and other ones to correctly calculate the maximum frame's length.