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

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Message-ID: <20200120095714.GA3421303@splinter>
Date:   Mon, 20 Jan 2020 11:57:14 +0200
From:   Ido Schimmel <idosch@...sch.org>
To:     "Hans-Christian Egtvedt (hegtvedt)" <hegtvedt@...co.com>
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 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.

> 
> 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