[PATCH net v6 1/2] net: validate virtio checksum start after network header

[Jakub Kicinski]

On Wed, 23 Sep 2026 22:02:57 -0400 Michael S. Tsirkin wrote:
> $ git grep 'skb->csum_start\ ='
> drivers/net/ethernet/hisilicon/hns3/hns3_enet.c:        skb->csum_start = (unsigned char *)th - skb->head;
> drivers/net/ethernet/mellanox/mlx5/core/en_rx.c:        skb->csum_start = (unsigned char *)uh - skb->head;
> drivers/net/ethernet/mellanox/mlx5/core/en_rx.c:        skb->csum_start = (unsigned char *)uh - skb->head;
> drivers/net/ethernet/mellanox/mlx5/core/en_rx.c:        skb->csum_start = (unsigned char *)tcp - skb->head;
> drivers/net/ethernet/mellanox/mlx5/core/en_rx.c:        skb->csum_start = (unsigned char *)tcp - skb->head;

These are HW-GRO, ASIC coalesced TCP segments so it better know 
the _correct_ offsets of things. And it's hardly remote-provided?

> drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c:         skb->csum_start = skb_transport_header(skb) - skb->head;

selftest