net: avoid false positives in untrusted gso validation (9e8db591) · Commits · 戴 / test

GSO packets with vnet_hdr must conform to a small set of gso_types. The below commit uses flow dissection to drop packets that do not. But it has false positives when the skb is not fully initialized. Dissection needs skb->protocol and skb->network_header. Infer skb->protocol from gso_type as the two must agree. SKB_GSO_UDP can use both ipv4 and ipv6, so try both. Exclude callers for which network header offset is not known. Fixes: ("net: validate untrusted gso packets without csum offload") Signed-off-by:

Willem de Bruijn <willemb@google.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

include/linux/virtio_net.h

+12 −2

Original line number	Diff line number	Diff line
		@@ -61,12 +61,22 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
		/* gso packets without NEEDS_CSUM do not set transport_offset.
		* probe and drop if does not match one of the above types.
		*/
		if (gso_type) {
		if (gso_type && skb->network_header) {
		if (!skb->protocol)
		virtio_net_hdr_set_proto(skb, hdr);
		retry:
		skb_probe_transport_header(skb, -1);
		if (!skb_transport_header_was_set(skb))
		if (!skb_transport_header_was_set(skb)) {
		/* UFO does not specify ipv4 or 6: try both */
		if (gso_type & SKB_GSO_UDP &&
		skb->protocol == htons(ETH_P_IP)) {
		skb->protocol = htons(ETH_P_IPV6);
		goto retry;
		}
		return -EINVAL;
		}
		}
		}

		if (hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
		u16 gso_size = __virtio16_to_cpu(little_endian, hdr->gso_size);

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