netdev - Re: [PATCH net] inet: frag: enforce memory limits earlier

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Message-Id: <20180731.144426.1299313303695149125.davem@davemloft.net>
Date:   Tue, 31 Jul 2018 14:44:26 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     edumazet@...gle.com
Cc:     netdev@...r.kernel.org, jannh@...gle.com, eric.dumazet@...il.com,
        fw@...len.de, posk@...gle.com, pabeni@...hat.com
Subject: Re: [PATCH net] inet: frag: enforce memory limits earlier

From: Eric Dumazet <edumazet@...gle.com>
Date: Mon, 30 Jul 2018 20:09:11 -0700

> We currently check current frags memory usage only when
> a new frag queue is created. This allows attackers to first
> consume the memory budget (default : 4 MB) creating thousands
> of frag queues, then sending tiny skbs to exceed high_thresh
> limit by 2 to 3 order of magnitude.
> 
> Note that before commit 648700f76b03 ("inet: frags: use rhashtables
> for reassembly units"), work queue could be starved under DOS,
> getting no cpu cycles.
> After commit 648700f76b03, only the per frag queue timer can eventually
> remove an incomplete frag queue and its skbs.
> 
> Fixes: b13d3cbfb8e8 ("inet: frag: move eviction of queues to work queue")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: Jann Horn <jannh@...gle.com>

Applied and queued up for -stable.