netdev - Re: [PATCH net-next 1/2] ip: fail fast on IP defrag errors

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Message-Id: <20180829.194958.139685537797704906.davem@davemloft.net>
Date:   Wed, 29 Aug 2018 19:49:58 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     posk@...gle.com
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH net-next 1/2] ip: fail fast on IP defrag errors

From: Peter Oskolkov <posk@...gle.com>
Date: Tue, 28 Aug 2018 11:36:19 -0700

> The current behavior of IP defragmentation is inconsistent:
> - some overlapping/wrong length fragments are dropped without
>   affecting the queue;
> - most overlapping fragments cause the whole frag queue to be dropped.
> 
> This patch brings consistency: if a bad fragment is detected,
> the whole frag queue is dropped. Two major benefits:
> - fail fast: corrupted frag queues are cleared immediately, instead of
>   by timeout;
> - testing of overlapping fragments is now much easier: any kind of
>   random fragment length mutation now leads to the frag queue being
>   discarded (IP packet dropped); before this patch, some overlaps were
>   "corrected", with tests not seeing expected packet drops.
> 
> Note that in one case (see "if (end&7)" conditional) the current
> behavior is preserved as there are concerns that this could be
> legitimate padding.
> 
> Signed-off-by: Peter Oskolkov <posk@...gle.com>
> Reviewed-by: Eric Dumazet <edumazet@...gle.com>
> Reviewed-by: Willem de Bruijn <willemb@...gle.com>

Applied.