netdev - Re: [PATCH] phonet: Check input from user before allocating

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Message-Id: <20120402.174006.70116829696492189.davem@davemloft.net>
Date:	Mon, 02 Apr 2012 17:40:06 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	remi@...lab.net
Cc:	levinsasha928@...il.com, remi.denis-courmont@...ia.com,
	davej@...hat.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] phonet: Check input from user before allocating

From: "Rémi Denis-Courmont" <remi@...lab.net>
Date: Mon, 2 Apr 2012 22:01:40 +0300

> Le lundi 2 avril 2012 23:31:00 Sasha Levin, vous avez écrit :
>> A phonet packet is limited to USHRT_MAX bytes, this is never checked during
>> tx which means that the user can specify any size he wishes, and the kernel
>> will attempt to allocate that size.
> 
> Does this really solve the problem?  I guess 128kb is still possible with 
> USHRT_MAX plus skbuff overhead, which might still trigger OOM relatively 
> easily once the memory gets sufficiently fragmented.
> 
> How does UDP deal with this?

UDP generates a fragment list of MTU sized SKBs.

Phonet could avoid the large allocations by building page based
SKBs.
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