On Tue, Sep 3, 2019 at 1:03 PM Shmulik Ladkani <shmu...@metanetworks.com> wrote: > > On Tue, 3 Sep 2019 12:23:54 -0400 > Willem de Bruijn <willemdebruijn.ker...@gmail.com> wrote: > > > This is a lot more code change. Especially for stable fixes that need > > to be backported, a smaller patch is preferable. > > Indeed. Thanks for the feedback. > > > My suggestion only tested the first frag_skb length. If a list can be > > created where the first frag_skb is head_frag but a later one is not, > > it will fail short. I kind of doubt that. > > > > By default skb_gro_receive builds GSO skbs that can be segmented > > along the original gso_size boundaries. We have so far only observed > > this issue when messing with gso_size. > > The rationale was based on inputs specified in 43170c4e0ba7, where a GRO > skb has a fraglist with different amounts of payloads. > > > We can easily refine the test to fall back on to copying only if > > skb_headlen(list_skb) != mss. > > I'm concerned this is too generic; innocent skbs may fall victim to our > skb copy fallback. Probably those mentioned in 43170c4e0ba7. > > > Alternatively, only on SKB_GSO_DODGY is fine, too. > > > > I suggest we stick with the two-liner. > > OK. > So lets refine your original codition, testing only the first > frag_skb, but also ensuring SKB_GSO_DODGY *and* 'skb_headlen(list_skb) != mss' > (we know existing code DOES work OK for unchanged gso_size, even if frags > have linear, non head_frag, data). > > This hits the known, reproducable case of the mentioned BUG_ON, and is > tightly scoped to that case. > > If that's agreed, I'll submit a proper patch.
Yep, that sounds good to me.
