linux-kernel - Re: [PATCH] net: use __GFP_NORETRY for high order allocations

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Date:	Tue, 25 Feb 2014 15:50:27 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	ebiederm@...ssion.com
Cc:	eric.dumazet@...il.com, netdev@...r.kernel.org,
	rientjes@...gle.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: use __GFP_NORETRY for high order allocations

From: ebiederm@...ssion.com (Eric W. Biederman)
Date: Fri, 07 Feb 2014 16:22:56 -0800

> David Miller <davem@...emloft.net> writes:
> 
>> From: Eric Dumazet <eric.dumazet@...il.com>
>> Date: Thu, 06 Feb 2014 10:42:42 -0800
>>
>>> From: Eric Dumazet <edumazet@...gle.com>
>>> 
>>> sock_alloc_send_pskb() & sk_page_frag_refill()
>>> have a loop trying high order allocations to prepare
>>> skb with low number of fragments as this increases performance.
>>> 
>>> Problem is that under memory pressure/fragmentation, this can
>>> trigger OOM while the intent was only to try the high order
>>> allocations, then fallback to order-0 allocations.
>>> 
>>> We had various reports from unexpected regressions.
>>> 
>>> According to David, setting __GFP_NORETRY should be fine,
>>> as the asynchronous compaction is still enabled, and this
>>> will prevent OOM from kicking as in :
>>  ...
>>> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
>>> Acked-by: David Rientjes <rientjes@...gle.com>
>>
>> Applied, do we want this for -stable?
> 
> The first hunk goes back to 3.12 and the second hunk goes back to 3.8.
> 
> I think so.    The change is safe and this class of problem can cause an
> external attack to trigger an OOM on your box, by controlling the packet
> flow.

Great, I'm working integrating this into my -stable queue right now.
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