On 9/19/26 6:47 PM, Paulos Yibelo wrote:
> __virtio_net_hdr_to_skb() rejects a CHECKSUM_PARTIAL start smaller than an
> estimated minimum network-header length. The comparison currently uses the
> offset from skb->data rather than the offset from skb_network_header().
>
> For an AF_PACKET frame, skb->data can still point at the Ethernet header
> while skb_network_header() points past nested link-layer headers. A
> checksum start at the network header can therefore pass, then target byte
> zero after those headers are removed.
>
> This does not require a virtual-machine guest. A TUN device with
> virtio-net header support can supply the same checksum metadata.
>
> Keep the existing data-relative lower bound and also require checksum
> start to follow the estimated minimum relative to skb_network_header().
>
> Fixes: 49d14b54a527 ("net: test for not too small csum_start in
> virtio_net_hdr_to_skb()")
> Reported-by: Paulos Yibelo <[email protected]>
> Cc: [email protected]
> Assisted-by: LLM
> Signed-off-by: Paulos Yibelo <[email protected]>
> Acked-by: Michael S. Tsirkin <[email protected]>
> ---
> Changes in v4:
> - State explicitly that a TUN device is sufficient and no guest is required,
> as noted by Michael S. Tsirkin. No code changes.
>
> Changes in v3:
> - Keep the network-relative comparison on one line for readability, as
> requested by David Ahern.
>
> Changes in v2:
> - Make nh_min_len an int and remove the casts, as suggested by Michael S.
> Tsirkin.
>
> include/linux/virtio_net.h | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
Reviewed-by: David Ahern <[email protected]>
