On Tue, Sep 10, 2024 at 05:35:35PM -0400, Willem de Bruijn wrote: > From: Willem de Bruijn <willemb@xxxxxxxxxx> > > The referenced commit drops bad input, but has false positives. > Tighten the check to avoid these. > > The check detects illegal checksum offload requests, which produce > csum_start/csum_off beyond end of packet after segmentation. > > But it is based on two incorrect assumptions: > > 1. virtio_net_hdr_to_skb with VIRTIO_NET_HDR_GSO_TCP[46] implies GSO. > True in callers that inject into the tx path, such as tap. > But false in callers that inject into rx, like virtio-net. > Here, the flags indicate GRO, and CHECKSUM_UNNECESSARY or > CHECKSUM_NONE without VIRTIO_NET_HDR_F_NEEDS_CSUM is normal. > > 2. TSO requires checksum offload, i.e., ip_summed == CHECKSUM_PARTIAL. > False, as tcp[46]_gso_segment will fix up csum_start and offset for > all other ip_summed by calling __tcp_v4_send_check. > > Because of 2, we can limit the scope of the fix to virtio_net_hdr > that do try to set these fields, with a bogus value. > I see it is already queued and extremely sorry for not testing and getting back earlier. Good news: it does fix the issue in my setup(same as reported at [1]) So, FWIW, Tested-by: Sudeep Holla <sudeep.holla@xxxxxxx> -- Regards, Sudeep [1] https://lore.kernel.org/netdev/ZtsTGp9FounnxZaN@xxxxxxx/
