netdev - Re: [PATCH] net: Convert skb->csum_(start|offset) integrity BUG_ON() to WARN

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Date:	Thu, 14 Feb 2013 10:18:53 +0000
From:	Thomas Graf <tgraf@...g.ch>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH] net: Convert skb->csum_(start|offset) integrity BUG_ON()
 to WARN_ON() & drop

On 02/13/13 at 07:37pm, David Miller wrote:
> From: Thomas Graf <tgraf@...g.ch>
> Date: Wed, 13 Feb 2013 23:48:43 +0000
[...]
> >  b) No longer collapse if the new skb would result in a
> >     a headroom + data that exceeds 64K. This seems to be the
> >     most trivial fix.
[...]
> > Other ideas?
> 
> "b" is a good idea.

OK, patch to do so being tested by original reporter.

> Let's not paper over this, this BUG_ON() is really a BUG_ON()
> meaning "FIX ME NOW" :-)

Maybe it's my general dislike of BUG_ON() in the processing
path, especially if the bug condition can be influenced remotely.
It looks absolutely doable to trigger the previously mentioned
partial acking & collapsing on purpose by a malicious receiver
even with an MTU of 1500. I believe we should avoid total DoS
in future similar situations that we don't think of yet.
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