On 2023/12/12 12:35, Jason Wang wrote:>>>> +done: >>>> + backend.fd = tun_alloc(); >>>> + assert(backend.fd >= 0); >>>> + vdev_info_init(&dev, features); >>>> + vq_info_add(&dev, 256); >>>> + run_test(&dev, &dev.vqs[0], delayed, batch, reset, nbufs); >>> >>> I'd expect we are testing some basic traffic here. E.g can we use a >>> packet socket then we can test both tx and rx? >> >> Yes, only rx for tun is tested. >> Do you have an idea how to test the tx too? As I am not familar enough >> with vhost_net and tun yet. > > Maybe you can have a packet socket to bind to the tun/tap. Then you can test: > > 1) TAP RX: by write a packet via virtqueue through vhost_net and read > it from packet socket > 2) TAP TX: by write via packet socket and read it from the virtqueue > through vhost_net
When implementing the TAP TX by adding VHOST_NET_F_VIRTIO_NET_HDR, I found one possible use of uninitialized data in vhost_net_build_xdp(). And vhost_hlen is set to sizeof(struct virtio_net_hdr_mrg_rxbuf) and sock_hlen is set to zero in vhost_net_set_features() for both tx and rx queue. For vhost_net_build_xdp() called by handle_tx_copy(): The (gso->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) checking below may cause a read of uninitialized data if sock_hlen is zero. And it seems vhost_hdr is skipped in get_tx_bufs(): https://elixir.bootlin.com/linux/latest/source/drivers/vhost/net.c#L616 static int vhost_net_build_xdp(struct vhost_net_virtqueue *nvq, struct iov_iter *from) { ... buflen += SKB_DATA_ALIGN(len + pad); alloc_frag->offset = ALIGN((u64)alloc_frag->offset, SMP_CACHE_BYTES); if (unlikely(!vhost_net_page_frag_refill(net, buflen, alloc_frag, GFP_KERNEL))) return -ENOMEM; buf = (char *)page_address(alloc_frag->page) + alloc_frag->offset; copied = copy_page_from_iter(alloc_frag->page, alloc_frag->offset + offsetof(struct tun_xdp_hdr, gso), sock_hlen, from); if (copied != sock_hlen) return -EFAULT; hdr = buf; gso = &hdr->gso; if ((gso->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) && vhost16_to_cpu(vq, gso->csum_start) + vhost16_to_cpu(vq, gso->csum_offset) + 2 > vhost16_to_cpu(vq, gso->hdr_len)) { ... } I seems the handle_tx_copy() does not handle the VHOST_NET_F_VIRTIO_NET_HDR case correctly, Or do I miss something obvious here? > > Thanks > >> >>> >>> Thanks >> > > . >
