linux-kernel - Re: [PATCH net V2 1/2] tuntap: limit head length of skb allocated

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Message-Id: <20131114.160630.604524891761475222.davem@davemloft.net>
Date:	Thu, 14 Nov 2013 16:06:30 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	jasowang@...hat.com
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	mst@...hat.com, stefanha@...hat.com, gregory.v.rose@...el.com
Subject: Re: [PATCH net V2 1/2] tuntap: limit head length of skb allocated

From: Jason Wang <jasowang@...hat.com>
Date: Wed, 13 Nov 2013 14:00:39 +0800

> We currently use hdr_len as a hint of head length which is advertised by
> guest. But when guest advertise a very big value, it can lead to an 64K+
> allocating of kmalloc() which has a very high possibility of failure when host
> memory is fragmented or under heavy stress. The huge hdr_len also reduce the
> effect of zerocopy or even disable if a gso skb is linearized in guest.
> 
> To solves those issues, this patch introduces an upper limit (PAGE_SIZE) of the
> head, which guarantees an order 0 allocation each time.
> 
> Cc: Stefan Hajnoczi <stefanha@...hat.com>
> Cc: Michael S. Tsirkin <mst@...hat.com>
> Signed-off-by: Jason Wang <jasowang@...hat.com>

Applied and queued up for -stable.
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