linux-kernel - Re: [PATCH 3/3] net: tipc: fix information leak to userland

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Date:	Wed, 10 Nov 2010 12:58:54 +0100
From:	walter harms <wharms@....de>
To:	Vasiliy Kulikov <segooon@...il.com>
CC:	David Miller <davem@...emloft.net>,
	kernel-janitors@...r.kernel.org, jon.maloy@...csson.com,
	allan.stephens@...driver.com,
	tipc-discussion@...ts.sourceforge.net, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] net: tipc: fix information leak to userland



Am 09.11.2010 21:33, schrieb Vasiliy Kulikov:
> On Tue, Nov 09, 2010 at 09:26 -0800, David Miller wrote:
>> From: Vasiliy Kulikov <segooon@...il.com>
>> Date: Sun, 31 Oct 2010 20:10:32 +0300
>>
>>> Structure sockaddr_tipc is copied to userland with padding bytes after
>>> "id" field in union field "name" unitialized.  It leads to leaking of
>>> contents of kernel stack memory.  We have to initialize them to zero.
>>>
>>> Signed-off-by: Vasiliy Kulikov <segooon@...il.com>
>>
>> Applied.
>>
>> Patches #1 and #2 were given feedback which I need you to integrate
>> and submit new patches based upon, thanks.
> 
> About #2:
> 
> I still think that this:
> 
>     if (dev)
>         strncpy(uaddr->sa_data, dev->name, 14);
>     else
>         memset(uaddr->sa_data, 0, 14);
> 
> is better than this:
> 
>     memset(uaddr->sa_data, 0, 14);
>     dev = dev_get_by_index_rcu(sock_net(sk), pkt_sk(sk)->ifindex);
>     if (dev)
>         strlcpy(uaddr->sa_data, dev->name, 15);
> 
> Doesn't it?  Explicitly filling with zero on the same "if" level is
> slightly easier to read and understand.
> 

no problem with me, since i came up with the idea a simple explanation:
IMHO the pattern clear/if/copy is more robust

NTL the core problem was that sizeof sa_data is 14 while dev->name is IFNAMESZ=15.


re,
 wh
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