netdev - Re: [2.6 PATCH] IPV6: Check length of optval provided by user in setsockopt()

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Message-ID: <47F0C556.8090109@cn.fujitsu.com>
Date:	Mon, 31 Mar 2008 19:04:54 +0800
From:	Wang Chen <wangchen@...fujitsu.com>
To:	YOSHIFUJI Hideaki / 吉藤英明 
	<yoshfuji@...ux-ipv6.org>
CC:	davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [2.6 PATCH] IPV6: Check length of optval provided by user in
 setsockopt()

YOSHIFUJI Hideaki / 吉藤英明 said the following on 2008-3-31 18:53:
>>>> Check length of setsockopt's optval, which provided by user, before copy it
>>>> from user space.
>>> Please use "<" not "==".
>>>
>> There are two reasons that why I only check whether
>> len of optval is equal to that one in user space.
>> 1. We currently copy the entire structure from user
>>    to kernel.
>> 2. In other cases, such as IPV6_LEAVE/JOIN_ANYCAST,
>>    we check whether the len is equal to struct's len.
>>
>> So, Yoshifuji-san, can you tell me more about why we
>> should use "<"? :)
> 
> POSIX, as we have some comments in that file ;-).
> If it is shorter than expected, -EINVAL, otherwise, no error.
> We need to fix other sites as well.
> 

ooh, I see.
I will take a business trip to Japan tomorrow and I will finish
this patch since I come back weekend.
Thank you for your explanation.

--WCN

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