From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: ipv6: handle -EFAULT from skb_copy_bits Date: Tue, 20 Dec 2016 13:28:13 -0500 (EST) Message-ID: <20161220.132813.435056880928769245.davem@davemloft.net> References: <20161220004013.43pcopemc6im32az@codemonkey.org.uk> <20161219.203623.119653805184192345.davem@davemloft.net> <20161220181728.dd2cynjwrceruwcu@codemonkey.org.uk> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: davej@codemonkey.org.uk Return-path: Received: from shards.monkeyblade.net ([184.105.139.130]:42910 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1764493AbcLTS2R (ORCPT ); Tue, 20 Dec 2016 13:28:17 -0500 In-Reply-To: <20161220181728.dd2cynjwrceruwcu@codemonkey.org.uk> Sender: netdev-owner@vger.kernel.org List-ID: From: Dave Jones Date: Tue, 20 Dec 2016 13:17:28 -0500 > On Mon, Dec 19, 2016 at 08:36:23PM -0500, David Miller wrote: > > From: Dave Jones > > Date: Mon, 19 Dec 2016 19:40:13 -0500 > > > > > On Mon, Dec 19, 2016 at 07:31:44PM -0500, Dave Jones wrote: > > > > > > > Unfortunately, this made no difference. I spent some time today trying > > > > to make a better reproducer, but failed. I'll revisit again tomorrow. > > > > > > > > Maybe I need >1 process/thread to trigger this. That would explain why > > > > I can trigger it with Trinity. > > > > > > scratch that last part, I finally just repro'd it with a single process. > > > > Thanks for the info, I'll try to think about this some more. > > I threw in some debug printks right before that BUG_ON. > it's always this: > > skb->len=31 skb->data_len=0 offset:30 total_len:9 > > Shouldn't we have kicked out data_len=0 skb's somewhere before we got this far ? skb->data_len is just the length of any non-linear data in the SKB. This has to do with the SKB buffer layout and geometry, not whether the packet is "fragmented" in the protocol sense. So no, this isn't a criteria for packets being filtered out by this point. Can you try to capture what sk->sk_socket->type and inet_sk(sk)->hdrincl are set to at the time of the crash? Thanks.