From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH net-next] net: ndisc.c: reduce size of
 __ndisc_fill_addr_option()
Date: Mon, 29 May 2017 23:31:09 -0400 (EDT)
Message-ID: <20170529.233109.702640863399503414.davem@davemloft.net>
References: <20170527151514.GA3347@avx2>
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Cc: Linyu.Yuan@alcatel-sbell.com.cn, netdev@vger.kernel.org
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From: Alexey Dobriyan <adobriyan@gmail.com>
Date: Sat, 27 May 2017 18:15:14 +0300

>> --- a/net/ipv6/ndisc.c
>> +++ b/net/ipv6/ndisc.c
>> @@ -148,17 +148,18 @@ void __ndisc_fill_addr_option(struct sk_buff *skb, int type, void *data,
> 
>>  	space -= data_len;
>> -	if (space > 0)
>> -		memset(opt, 0, space);
>> +
>> +	memset(opt, 0, space);
> 
> This can't be right.
> 
> And what size are you reducing?

It is right, space equals the same thing it would have equaled
before his changes, and a memset() of zero length will do the
right thing.

Finally, if space can be negative here, we have real problems.