netdev - Re: [net-next-2.6 PATCH 01/10] ethtool: prevent null pointer dereference with NTUPLE set but no set_rx

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Date:	Sat, 26 Feb 2011 18:16:31 -0800
From:	Alexander Duyck <alexander.duyck@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	alexander.h.duyck@...el.com, bhutchings@...arflare.com,
	jeffrey.t.kirsher@...el.com, netdev@...r.kernel.org
Subject: Re: [net-next-2.6 PATCH 01/10] ethtool: prevent null pointer
 dereference with NTUPLE set but no set_rx_ntuple

On Sat, Feb 26, 2011 at 4:07 PM, David Miller <davem@...emloft.net> wrote:
> From: Alexander Duyck <alexander.h.duyck@...el.com>
> Date: Fri, 25 Feb 2011 16:40:13 -0800
>
>> It cannot occur with any of the in-kernel drivers since they all set
>> the NETIF_F_NTUPLE flag and have the function defined.  However going
>> forward I would like to have the option of using the network flow
>> classifier interface instead of the set_rx_ntuple interface due to the
>> fact that it supports many of the features I needed.
>
> This still doesn't explain to me why a driver would set the feature
> flag, but not actually implement the feature.

Actually the reason I ran into this is because of the patches in the
RFC set.  Basically I was looking at moving the ntuple support in
ixgbe over to network flow classifier rules.  As such I was leaving
the ntuple flag set, but using set_rxnfc via the filter rules instead.
 If you recommend adding a new flag to do that I am fine with that.

> I'm not applying this patch.
>
> When you create the situation that causes the potentially NULL
> dereference, then you can use that patch to show why this seemingly
> illogical situation can indeed occur.
>
> Until then no driver causes this issue, therefore the problem does
> not exist.

I'll do some digging late next week to see if there are any other
means of encountering the issue and will get back to you if I find
anything.

Thanks,

Alex
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