Sudeep Holla wrote:
On Tue, Sep 10, 2024 at 05:35:35PM -0400, Willem de Bruijn wrote:
From: Willem de Bruijn willemb@google.com
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:
- 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.
- 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@arm.com
That is great to hear. Thanks for reporting your results, Sudeep.