netdev - Re: [PATCH] Prevent reading uninitialized memory with socket filters

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Date:	Tue, 09 Nov 2010 15:03:06 -0800
From:	Joe Perches <joe@...ches.com>
To:	Dan Rosenberg <drosenberg@...curity.com>
Cc:	netdev@...r.kernel.org, stable@...nel.org, security@...nel.org
Subject: Re: [PATCH] Prevent reading uninitialized memory with socket
 filters

On Tue, 2010-11-09 at 17:28 -0500, Dan Rosenberg wrote:
> The "mem" array used as scratch space for socket filters is not
> initialized, allowing unprivileged users to leak kernel stack bytes.

Hi Dan.

Using
	type var[count] = {};
instead of
	type var[count];
	...
	memset(var, 0, sizeof(var));

at least for gcc 4.4 and 4.5 generally results in smaller code.

$ size net/core/filter.o*
   text	   data	    bss	    dec	    hex	filename
   6751	     56	   1736	   8543	   215f	net/core/filter.o.memset
   6749	     56	   1736	   8541	   215d	net/core/filter.o.init


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