netdev - Re: Regression in macvlan driver in stable release 4.4.209

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Date:   Mon, 20 Jan 2020 10:03:03 +0000
From:   "Hans-Christian Egtvedt (hegtvedt)" <hegtvedt@...co.com>
To:     Ido Schimmel <idosch@...sch.org>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: Regression in macvlan driver in stable release 4.4.209

On 20.01.2020 10:57, Ido Schimmel wrote:
> On Mon, Jan 20, 2020 at 09:17:35AM +0000, Hans-Christian Egtvedt (hegtvedt) wrote:
>> Hello,
>>
>> I am seeing a regression in the macvlan kernel driver after Linux stable
>> release 4.4.209, bisecting identifies commit
>> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-4.4.y&id=8d28d7e88851b1081b05dc269a27df1c8a903f3e
> 
> Noticed it too last week (on net-next), but Eric already fixed it:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1712b2fff8c682d145c7889d2290696647d82dab
> 
> I assume the patch will find its way to 4.4.y soon now that it is in
> mainline.

Excellent, thank you for the quick update.

I will know what to look for in upcoming 4.4.y releases.

>> There seems to be a history behind this, and I do not have the full
>> overview of the intention behind the change.
>>
>> What I see on my target, Aarch64 CPU, is that this patch moves the eth
>> pointer in macvlan_broadcast() function some bytes. This will cause
>> everything within the ethhdr struct to be wrong AFAICT.
>>
>> An example:
>> Original code "eth = eth_hdr(skb)"
>>      eth = ffffffc007a1b002
>> New code "eth = skb_eth_hdr(skb)"
>>      eth = ffffffc007a1b010
>>
>> Let me know if I can assist in any way.-- 
Best regards,
Hans-Christian Noren Egtvedt