netdev - Re: [PATCH RFC] ipv6: enable IPV6_FLOWLABEL

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Date:	Mon, 04 Nov 2013 18:09:01 +0100
From:	Florent Fourcot <florent.fourcot@...t-bretagne.fr>
To:	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	netdev@...r.kernel.org
Subject: Re: [PATCH RFC] ipv6: enable IPV6_FLOWLABEL_MGR for getsockopt


> We should take ip6_fl_lock here, otherwise expires extraction races with
> the garbage collector (which can update it). There seem to be some other
> unsafe places, e.g. fl6_renew.
> 

I will fix it, and for fl6_renew too.

>> +			freq->flr_label = sfl->fl->label;
>> +			freq->flr_dst = sfl->fl->dst;
>> +			freq->flr_share = sfl->fl->share;
>> +			freq->flr_expires = (sfl->fl->expires - jiffies) / HZ;
>> +			freq->flr_linger = sfl->fl->linger / HZ;
>> +
>> +			rcu_read_unlock_bh();
>> +			return 0;
>> +		}
>> +	}
>> +	rcu_read_unlock_bh();
>> +
>> +	return 0;
> 
> Maybe return -EINVAL for not found?
> 

I don't like -EINVAL for this case, since the user can not know if there
are no label or if the request has bad parameters. Could -ENOMSG be OK?


>> +	case IPV6_FLOWLABEL_MGR:
>> +	{
>> +		struct in6_flowlabel_req freq;
>> +
> 
> Can you think about other actions one might do with this getsockopt? Maybe
> we should copy_from_user freq and check if action specifies a GET
> request. So a further extension to this API won't break users which did
> pass uninitialized memory to this getsockopt.
> 

Very good idea.

Regards,

-- 
Florent.
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