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

[Wang Chen <wangchen@cn.fujitsu.com>]

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