Subject: Re: [PATCH] ipv6: fix incorrect route 'expires' value passed to userspace.

From: Li Wei <[email-masked]>
Date: Tue, 17 Jul 2012 09:53:35 +0800

于 2012-7-17 0:41, Stephen Hemminger 写道:
> On Mon, 16 Jul 2012 16:09:37 +0800
> Li Wei <[email-masked]> wrote:
> 
>> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
>> index becb048..a7fec9d 100644
>> --- a/net/ipv6/route.c
>> +++ b/net/ipv6/route.c
>> @@ -2516,7 +2516,7 @@ static int rt6_fill_node(struct net *net,
>>  		goto nla_put_failure;
>>  	if (!(rt->rt6i_flags & RTF_EXPIRES))
>>  		expires = 0;
>> -	else if (rt->dst.expires - jiffies < INT_MAX)
>> +	else if ((int)(rt->dst.expires - jiffies) < INT_MAX)
>>  		expires = rt->dst.expires - jiffies;
>>  	else
>>  		expires = INT_MAX;
> 
> Why not use time_is_after_jiffies() macro?

time_is_after_jiffies() return a bool but we need "how much time
before/after jiffies" here.

However, I also think these code seems a little ugly, because we
need to store the result of two "unsigned long"'s subtraction into
an integer. Maybe we should distinguish expires before and after 
jiffies to proper process the overflows.

Thanks,
Wei