netdev - Re: [PATCH] net: check the length of the data before dereferencing it

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Message-Id: <20120401.232942.1829187970291547571.davem@davemloft.net>
Date:	Sun, 01 Apr 2012 23:29:42 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	xiaosuo@...il.com, kaber@...sh.net, pablo@...filter.org,
	netfilter-devel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH] net: check the length of the data before dereferencing
 it

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Mon, 02 Apr 2012 05:19:33 +0200

>> @@ -3845,6 +3845,8 @@ void tcp_parse_options(const struct sk_buff *skb, struct tcp_options_received *o
>>  			length--;
>>  			continue;
>>  		default:
>> +			if (length < 2)
>> +				return;
>>  			opsize = *ptr++;
>>  			if (opsize < 2) /* "silly options" */
>>  				return;
> 
> Acked-by: Eric Dumazet <eric.dumazet@...il.com>

Tag Eric, you're it.

You ACK'd this patch, so you get to show how this is actually able
to cause some kind of problem.

I assert that this is adding a useless test, that doesn't fix any kind
of possible crash or misbehavior.  If length == 1 at the default:, the
code will absolutely do the right thing.

Prove me wrong.
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