Return-path: Received: from mail-qk0-f180.google.com ([209.85.220.180]:33637 "EHLO mail-qk0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751520AbeBALEN (ORCPT ); Thu, 1 Feb 2018 06:04:13 -0500 Received: by mail-qk0-f180.google.com with SMTP id i141so18790196qke.0 for ; Thu, 01 Feb 2018 03:04:13 -0800 (PST) Subject: Re: [PATCH] brcmfmac: detect & reject faked packet generated by a firmware To: =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= , Hante Meuleman References: <20180130090922.30346-1-zajec5@gmail.com> <5A705B5E.5070906@broadcom.com> <5A71D08B.7090905@broadcom.com> <4f6223b8083ed69432493a37d4f45b69@mail.gmail.com> Cc: =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= , Kalle Valo , Franky Lin , Chi-Hsien Lin , Wright Feng , Pieter-Paul Giesberts , linux-wireless@vger.kernel.org, "BRCM80211-DEV-LIST,PDL" , brcm80211-dev-list@cypress.com From: Arend van Spriel Message-ID: <5A72F42A.5090700@broadcom.com> (sfid-20180201_120416_625588_70DD680D) Date: Thu, 1 Feb 2018 12:04:10 +0100 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Sender: linux-wireless-owner@vger.kernel.org List-ID: On 2/1/2018 11:42 AM, Rafał Miłecki wrote: > On 2018-01-31 17:14, Hante Meuleman wrote: >> It is an 802.2 frame, more specifically a LLC XID frames. So why it >> exists? >> And more over, why would we crash as an result? Decoding info can be >> found >> here: >> >> https://www.cisco.com/c/en/us/support/docs/ibm-technologies/logical-link-control-llc/12247-45.html#con3 >> >> >> The frame was likely sent by the stack from remote site PC, should be >> possible to capture with tcpdump. >> >> I've seen these frames before, but don’t know what they are for. The >> frame >> appears to be correctly encoded. The ethertype, is not a type, but a len >> field. The only protocol with such a short len allowed is llc, see also >> >> https://www.savvius.com/networking-glossary/ethernet/frame_formats/ >> >> So it is 802.2 (also known as LLC) > > Please, try to accept for a moment that it may be really a *firmware* > doing something unexpected. I feel you don't really want to trust my > research and conclusions ;) We do. What Hante is saying is that it is a valid packet and we should not discard it. > Maybe you can spend a moment and try to reproduce this problem? It > should be rather simple, I see this packet every time. I tried on my OpenWrt box, which is a bridged config, but did not see it. > Why I'm blaming a firmware: > > 1) I see that packet being sent no matter what device tries to connect > (Linux, Android, Windows). > > 2) I can't see that packet when connecting the same devices to a > non-Broadcom AP. > > 3) Running Wireshark on my Linux notebook never shows that packet > leaving my notebook > > 4) Running independent device in monitor mode never catches that packet > in the air > > I really tried to do my homework well before sending this patch. I see > no other explanation for this packet's existence. Ok. > Could you try grepping your firmware source looking some LLC references? > Maybe there is really something you can find there to confirm this > issue? Will do. > P.S. > Arend's right, firmware isn't crashing, I never said that :) Regards, Arend