netdev - Re: [PATCH RFC net-next] packet: always ensure that we pass hard_header_len bytes in skb

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Message-Id: <20170130.114143.1357866047815335563.davem@davemloft.net>
Date:   Mon, 30 Jan 2017 11:41:43 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     sowmini.varadhan@...cle.com
Cc:     willemdebruijn.kernel@...il.com, netdev@...r.kernel.org
Subject: Re: [PATCH RFC net-next] packet: always ensure that we pass
 hard_header_len bytes in skb_headlen() to the driver

From: Sowmini Varadhan <sowmini.varadhan@...cle.com>
Date: Mon, 30 Jan 2017 11:26:03 -0500

> On (01/27/17 19:19), Willem de Bruijn wrote:
>> > other than ax25, are there variable length header protocols out there
>> > without ->validate, and which need the CAP_RAW_SYSIO branch?
>> 
>> I don't know. An exhaustive search of protocols (by header_ops) may be
>> needed to say for sure.
>> 
>> If there are none, then the solution indeed is quite simple.
> 
> 
> I tried to start that exhaustive search, and it can be quite daunting:
> if you are doing this by just code-inspection, it's easy to get
> it wrong.. I havent quite given up yet, but it may be simpler to have
> the drivers support some defensive code against bogus skb's in the
> Tx path (the drivers will know, for sure, what's the min non-paged
> len they need anyway).

I think it's easier to audit all the header_ops than to add defensive
code to 500+ drivers.