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authorJonathan Davies <jonathan.davies@nutanix.com>2021-11-16 17:42:42 +0000
committerDavid S. Miller <davem@davemloft.net>2021-11-17 14:50:45 +0000
commitcf9acc90c80ecbee00334aa85d92f4e74014bcff (patch)
tree7f3ab1f535418e1d61669832d759366c44007f95 /include/linux/virtio_net.h
parent9b5a333272a48c2f8b30add7a874e46e8b26129c (diff)
net: virtio_net_hdr_to_skb: count transport header in UFO
virtio_net_hdr_to_skb does not set the skb's gso_size and gso_type correctly for UFO packets received via virtio-net that are a little over the GSO size. This can lead to problems elsewhere in the networking stack, e.g. ovs_vport_send dropping over-sized packets if gso_size is not set. This is due to the comparison if (skb->len - p_off > gso_size) not properly accounting for the transport layer header. p_off includes the size of the transport layer header (thlen), so skb->len - p_off is the size of the TCP/UDP payload. gso_size is read from the virtio-net header. For UFO, fragmentation happens at the IP level so does not need to include the UDP header. Hence the calculation could be comparing a TCP/UDP payload length with an IP payload length, causing legitimate virtio-net packets to have lack gso_type/gso_size information. Example: a UDP packet with payload size 1473 has IP payload size 1481. If the guest used UFO, it is not fragmented and the virtio-net header's flags indicate that it is a GSO frame (VIRTIO_NET_HDR_GSO_UDP), with gso_size = 1480 for an MTU of 1500. skb->len will be 1515 and p_off will be 42, so skb->len - p_off = 1473. Hence the comparison fails, and shinfo->gso_size and gso_type are not set as they should be. Instead, add the UDP header length before comparing to gso_size when using UFO. In this way, it is the size of the IP payload that is compared to gso_size. Fixes: 6dd912f82680 ("net: check untrusted gso_size at kernel entry") Signed-off-by: Jonathan Davies <jonathan.davies@nutanix.com> Reviewed-by: Willem de Bruijn <willemb@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux/virtio_net.h')
-rw-r--r--include/linux/virtio_net.h7
1 files changed, 6 insertions, 1 deletions
diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
index b465f8f3e554..04e87f4b9417 100644
--- a/include/linux/virtio_net.h
+++ b/include/linux/virtio_net.h
@@ -120,10 +120,15 @@ retry:
if (hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
u16 gso_size = __virtio16_to_cpu(little_endian, hdr->gso_size);
+ unsigned int nh_off = p_off;
struct skb_shared_info *shinfo = skb_shinfo(skb);
+ /* UFO may not include transport header in gso_size. */
+ if (gso_type & SKB_GSO_UDP)
+ nh_off -= thlen;
+
/* Too small packets are not really GSO ones. */
- if (skb->len - p_off > gso_size) {
+ if (skb->len - nh_off > gso_size) {
shinfo->gso_size = gso_size;
shinfo->gso_type = gso_type;