4.20-stable review patch. If anyone has any objections, please let me know.
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From: Willem de Bruijn willemb@google.com
commit 9e8db5913264d3967b93c765a6a9e464d9c473db upstream.
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: d5be7f632bad ("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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- include/linux/virtio_net.h | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-)
--- a/include/linux/virtio_net.h +++ b/include/linux/virtio_net.h @@ -61,10 +61,20 @@ static inline int virtio_net_hdr_to_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; + } } }