From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oliver Hartkopp Subject: Re: skbuff panic Date: Sun, 06 Jul 2014 14:12:53 +0200 Message-ID: <53B93D45.5090505@hartkopp.net> References: <53B7D63B.2060108@hartkopp.net> <53B8504C.4070808@hartkopp.net> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: Received: from mo4-p00-ob.smtp.rzone.de ([81.169.146.219]:30609 "EHLO mo4-p00-ob.smtp.rzone.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751011AbaGFMM4 (ORCPT ); Sun, 6 Jul 2014 08:12:56 -0400 In-Reply-To: Sender: linux-can-owner@vger.kernel.org List-ID: To: Austin Schuh Cc: linux-can@vger.kernel.org On 06.07.2014 07:07, Austin Schuh wrote: > What makes you think that someone opened a PF_PACKET socket? I'm > curious, since that observation may help me produce a more reliable > test case and debug it some more myself. If you look in your call trace is says: skb_push+0x38/0x39 (-->> which panics) packet_rcv_spkt+0x98/0xdf __netif_receive_skb_core+0x459/0x4dc get_parent_ip+0xe/0x3e __netif_receive_skb+0x53/0x65 As packet_rcv_spkt() is located in net/packet/af_packet.c there must be some user at this early stage of system boot to make PF_PACKET process the CAN frame. In https://gitorious.org/linux-can/can-tests there's a tst-packet.c program which uses the PF_PACKET socket to send/receive CAN frames. I was using tst-packet.c about four years ago for a test - without any problems. But maybe something in the network layer changed, so that CAN frame skbs need to be created with a different setup now. I'll try ASAP if tst-packet.c still works as expected on my machine. > > I'm going to work on reproducing the panic more reliable, and then > I'll give your patch a whirl. Currently, only PCs that are on the > other end of cell modems out in the field seem to be triggering the > panic. I'm hesitant to do excessive experimentation on something that > takes a plane trip to fix. That just means that this will take longer > to debug that I'd like... Indeed this should not be the plan ... Let's save the world by saving carbon dioxide ;-) Best regards, Oliver