Re: [GIT] Networking

Tom Herbert
2014-06-25T03:05:33Z

> tcp_gso_segment() makes sure that the headers are reachable in the linear
> area with the pskb_may_pull(skb, sizeof(*th)) call, and gso_make_checksum()
> is only working with the area up to SKB_GSO_CB()->csum_start which should
> be within this area for sure.
>
Seems likely that csum_start is not properly initialized in this path.
I am thinking that this may have happened in GRO path on a checksum
error where CHECKSUM_PARTIAL (and hence csum) is not set. That would
explain the infrequency of the occurrence, and also previously not
setting csum would have just resulted in sending a corrupted packet
not a crash.

> Well, that's the precondition we seem to be relying upon, I suppose an
> assert is in order.

Assert on SKB_GSO_CB()->csum_start == 0 would confirm my suspicion.