From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tom Herbert Subject: Re: [GIT] Networking Date: Tue, 24 Jun 2014 20:05:30 -0700 Message-ID: References: <20140616234254.GA15332@redhat.com> <20140623234759.GA19138@redhat.com> <20140624.172616.757600677169858458.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Cc: torvalds@linux-foundation.org, davej@redhat.com, Andrew Morton , Linux Netdev List , LKML To: David Miller Return-path: Received: from mail-ie0-f179.google.com ([209.85.223.179]:51535 "EHLO mail-ie0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753542AbaFYDFc (ORCPT ); Tue, 24 Jun 2014 23:05:32 -0400 Received: by mail-ie0-f179.google.com with SMTP id tr6so1083184ieb.24 for ; Tue, 24 Jun 2014 20:05:30 -0700 (PDT) In-Reply-To: <20140624.172616.757600677169858458.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: > 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.