Re: [GIT] Networking

Tom Herbert
2014-06-25T03:51:41Z

I believe in the no scatter-gather case of skb_segment is not set
correctly. Will post a patch momentarily.

On Tue, Jun 24, 2014 at 8:05 PM, Tom Herbert <therbert@google.com> wrote:
>> 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.