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net: avoid false positives in untrusted gso validation
commit9e8db59132
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:d5be7f632b
("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>
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parent
dac7d4432b
commit
d996573ebd
1 changed files with 12 additions and 2 deletions
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@ -61,12 +61,22 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
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/* gso packets without NEEDS_CSUM do not set transport_offset.
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* probe and drop if does not match one of the above types.
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*/
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if (gso_type) {
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if (gso_type && skb->network_header) {
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if (!skb->protocol)
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virtio_net_hdr_set_proto(skb, hdr);
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retry:
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skb_probe_transport_header(skb, -1);
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if (!skb_transport_header_was_set(skb))
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if (!skb_transport_header_was_set(skb)) {
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/* UFO does not specify ipv4 or 6: try both */
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if (gso_type & SKB_GSO_UDP &&
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skb->protocol == htons(ETH_P_IP)) {
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skb->protocol = htons(ETH_P_IPV6);
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goto retry;
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}
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return -EINVAL;
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}
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}
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}
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if (hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
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u16 gso_size = __virtio16_to_cpu(little_endian, hdr->gso_size);
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