I checked the patch on three reproducers and all three DEFINITELY broke the core.
There are two malfunctions. 1. No flag skb_shinfo(skb)->tx_flags |= SKBFL_SHARED_FRAG; If it is not set then __skb_linearize will not be executed in skb_checksum_help. sk_buff remains fragmented (non-linear) and this is the first warning. OR add skb_shinfo(skb)->tx_flags |= SKBFL_SHARED_FRAG. OR ask Eric Dumazet (cef401de7be8c). Is checking if (skb_has_shared_frag(skb)) so important? in the skb_checksum_help function, is it enough if (skb_is_nonlinear(skb)) ? 2. The skb_segment algorithm and related checks, this is where you need time to think ... Best regards Denis.
