netdev - Re: crash since commit "net/flow_dissector: switch to siphash"

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Message-ID: <ef16acf8-0143-9e42-9d65-2cedbd331bcc@ncentric.com>
Date:   Mon, 18 Nov 2019 15:12:39 +0100
From:   Koen Vandeputte <koen.vandeputte@...ntric.com>
To:     Hauke Mehrtens <hauke@...ke-m.de>,
        Eric Dumazet <edumazet@...gle.com>
Cc:     netdev <netdev@...r.kernel.org>, Greg KH <greg@...ah.com>
Subject: Re: crash since commit "net/flow_dissector: switch to siphash"


On 18.11.19 01:11, Hauke Mehrtens wrote:
> On 11/15/19 6:09 PM, Eric Dumazet wrote:
>> On Fri, Nov 15, 2019 at 3:30 AM Koen Vandeputte
>> <koen.vandeputte@...ntric.com> wrote:
>>>
>>> On 13.11.19 15:50, Eric Dumazet wrote:
>>>> On Wed, Nov 13, 2019 at 3:52 AM Koen Vandeputte
>>>> <koen.vandeputte@...ntric.com> wrote:
>>>>> Hi Eric,
>>>>>
>>>>> I'm currently testing kernel 4.14.153 bump for OpenWrt and noticed splat
>>>>> below on my testing boards.
>>>>> They all reboot continuously nearly immediately when linked.
>>>>>
>>>>> It feels like it's tied to a commit of yours [1]
>>>> Have you tried current upstream kernels ?
>>> No.
>>>
>>> This board is only supported on OpenWrt currently using 4.14 and it's
>>> not natively supported by upstream.
>>>
>>>> Is is a backport issue, or a bug in original commit ?
>>> No idea .. and I'm not profound enough on that part of the code to judge
>>> this,
>>>
>>> which is why I'm consulting your expert opinion.
>>>
>>>> Can you give us gcc version ?
>>> 7.4.0
>>>> Can you check what SIPHASH_ALIGNMENT value is at compile time ?
>>> 8 (exposed it in dmesg on boot)
>> Please ask OpenWrt specialists for support.
>>
>> The code is probably mishandled by the compiler.
>>
>> siphash() is supposed to handle misaligned data just fine, and
>> net/core/flow_dissector.c tries hard to align the keys anyway.
> Hi Koen,
>
> This is probably related to backports for the wireless driver which uses
> its own fq.h and fq_impl.h implementation and this is now conflicting
> with Eric's patch which got backported.
> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v4.14.154&id=a9de6f42e945cdb24b59c7ab7ebad1eba6cb5875
>
> I saw this as a compile warning when creating a new backports version
> and created this patch:
> https://www.spinics.net/lists/backports/msg04930.html
> This is for the other way around.
>
> I will try to create a patch for OpenWrt backports tomorrow to fix this
> problem and I am also planning to create a new backports release in the
> next few days.
>
> Hauke

Hi Hauke,

This indeed fixes the issue.

Thank you!


Sorry for the noise here. ;-)

Koen