Re: [PATCH 1/2] ipv4: fix do_ip_setsockopt optlen check for IP_MULTICAST_IF

[David Miller <davem@davemloft.net>]

From: Shan Wei <shanwei@cn.fujitsu.com>
Date: Thu, 17 Sep 2009 17:15:22 +0800

> Xiaotian Feng wrote, at 09/17/2009 01:19 PM:
>> Due to man page of setsockopt, if optlen is not valid, kernel should return
>> -EINVAL. But a simple testcase as following, errno is 0, which means setsockopt
>> is successful.
>> 
>>         addr.s_addr = inet_addr("192.1.2.3");
>>         setsockopt(s, IPPROTO_IP, IP_MULTICAST_IF, &addr, 1);
>> 	printf("errno is %d\n", errno);
>> 
>> This patch fixes the optlen check part, with the patch, we got errno EINVAL.
>> 
> 
> I also think it's a bug, the freebsd also does the optlen check. 
> But the style should be coincident with other option: firstly check the
> availability of optlen, then copy option value from user and deal with it.   
> 
> How about this one:

This definitely is better and cleaner, but please don't post such
things without proper signoffs and commit messages because now
I have to ask you to do that instead of me just applying your
patch :-/