From: Arend van Spriel <arend.vanspriel@broadcom.com>
To: "Rafał Miłecki" <rafal@milecki.pl>,
"Hante Meuleman" <hante.meuleman@broadcom.com>
Cc: "Rafał Miłecki" <zajec5@gmail.com>,
"Kalle Valo" <kvalo@codeaurora.org>,
"Franky Lin" <franky.lin@broadcom.com>,
"Chi-Hsien Lin" <chi-hsien.lin@cypress.com>,
"Wright Feng" <wright.feng@cypress.com>,
"Pieter-Paul Giesberts" <pieter-paul.giesberts@broadcom.com>,
linux-wireless@vger.kernel.org,
"BRCM80211-DEV-LIST,PDL" <brcm80211-dev-list.pdl@broadcom.com>,
brcm80211-dev-list@cypress.com
Subject: Re: [PATCH] brcmfmac: detect & reject faked packet generated by a firmware
Date: Thu, 1 Feb 2018 12:04:10 +0100 [thread overview]
Message-ID: <5A72F42A.5090700@broadcom.com> (raw)
In-Reply-To: <f64b5ee40e534046c47a5675a078706f@milecki.pl>
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
next prev parent reply other threads:[~2018-02-01 11:04 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-30 9:09 [PATCH] brcmfmac: detect & reject faked packet generated by a firmware Rafał Miłecki
2018-01-30 11:30 ` Arend van Spriel
2018-01-31 13:11 ` Rafał Miłecki
2018-01-31 14:00 ` Arend van Spriel
2018-01-30 11:47 ` Arend van Spriel
2018-01-31 13:14 ` Rafał Miłecki
2018-01-31 14:19 ` Arend van Spriel
2018-01-31 16:14 ` Hante Meuleman
2018-01-31 18:02 ` Arend van Spriel
2018-02-01 10:42 ` Rafał Miłecki
2018-02-01 11:04 ` Arend van Spriel [this message]
2018-02-01 11:16 ` Rafał Miłecki
2018-02-01 11:48 ` Rafał Miłecki
2018-02-01 12:23 ` Arend van Spriel
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