Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752237AbeAQGpg (ORCPT + 1 other); Wed, 17 Jan 2018 01:45:36 -0500 Received: from mo4-p00-ob.smtp.rzone.de ([81.169.146.217]:15462 "EHLO mo4-p00-ob.smtp.rzone.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750816AbeAQGpf (ORCPT ); Wed, 17 Jan 2018 01:45:35 -0500 X-RZG-AUTH: :P2MHfkW8eP4Mre39l357AZT/I7AY/7nT2yrDxb8mjG14FZxedJy6qgO1rHLMaVmKZDiSuDWYEcd9 X-RZG-CLASS-ID: mo00 Subject: Re: WARNING in can_rcv To: Dmitry Vyukov , Marc Kleine-Budde Cc: syzbot , David Miller , linux-can@vger.kernel.org, LKML , netdev , syzkaller-bugs@googlegroups.com References: <001a11c16b40d795350562e878cc@google.com> From: Oliver Hartkopp Message-ID: <48c5623e-de78-5cfa-b537-2acf9a44ae51@hartkopp.net> Date: Wed, 17 Jan 2018 07:39:24 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: On 01/16/2018 07:11 PM, Dmitry Vyukov wrote: > On Tue, Jan 16, 2018 at 7:07 PM, Marc Kleine-Budde wrote: >> On 01/16/2018 06:58 PM, syzbot wrote: >>> Hello, >>> >>> syzkaller hit the following crash on >>> a8750ddca918032d6349adbf9a4b6555e7db20da >>> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master >>> compiler: gcc (GCC) 7.1.1 20170620 >>> .config is attached >>> Raw console output is attached. >>> C reproducer is attached >>> syzkaller reproducer is attached. See https://goo.gl/kgGztJ >>> for information about syzkaller reproducers >>> >>> >>> IMPORTANT: if you fix the bug, please add the following tag to the commit: >>> Reported-by: syzbot+4386709c0c1284dca827@syzkaller.appspotmail.com >>> It will help syzbot understand when the bug is fixed. See footer for >>> details. >>> If you forward the report, please keep this part and the footer. >>> >>> device eql entered promiscuous mode >>> ------------[ cut here ]------------ >>> PF_CAN: dropped non conform CAN skbuf: dev type 65534, len 42, datalen 0 >>> WARNING: CPU: 0 PID: 3650 at net/can/af_can.c:729 can_rcv+0x1c5/0x200 >>> net/can/af_can.c:724 >>> Kernel panic - not syncing: panic_on_warn set ... >> >> Invalid packages generate a warning (WARN_ONCE()), and you have >> panic_on_warn active. Should we better silently drop these CAN packages? > > Hi, > > pr_warn_once() will be more appropriate. It prints a single line. > The idea behind this WARN() is to detect really bad things that might have happen on network driver level: The CAN subsystem registers with dev_add_pack() for ETH_P_CAN and ETH_P_CANFD only. These ETH_P_ types are only allowed to be created by CAN network devices (like vcan, vxcan, and real CAN drivers). I don't have any strong opinion on using WARN() or pr_warn_once(). Is this detected violation worth using WARN(), as something already must have gone really wrong to trigger this issue? Best regards, Oliver