netdev - Re: [patch 1/1][NETNS][IPV6] protect addrconf from loopback registration

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Message-ID: <m1ejev4dap.fsf@ebiederm.dsl.xmission.com>
Date:	Mon, 12 Nov 2007 09:51:58 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	"Denis V. Lunev" <den@...ru>
Cc:	Daniel Lezcano <dlezcano@...ibm.com>, davem@...emloft.net,
	netdev@...r.kernel.org, xemul@...nvz.org,
	containers@...ts.osdl.org, yoshfuji@...ux-ipv6.org,
	Benjamin Thery <benjamin.thery@...l.net>
Subject: Re: [patch 1/1][NETNS][IPV6] protect addrconf from loopback registration

"Denis V. Lunev" <den@...ru> writes:

>> Index: linux-2.6-netns/net/ipv6/addrconf.c
>> ===================================================================
>> --- linux-2.6-netns.orig/net/ipv6/addrconf.c
>> +++ linux-2.6-netns/net/ipv6/addrconf.c
>> @@ -2272,7 +2272,8 @@ static int addrconf_notify(struct notifi
>>  
>>  	switch(event) {
>>  	case NETDEV_REGISTER:
>> -		if (!idev && dev->mtu >= IPV6_MIN_MTU) {
>> +		if (!(dev->flags & IFF_LOOPBACK) &&
>> +		    !idev && dev->mtu >= IPV6_MIN_MTU) {

It is idev being true here for the loopback device that would
prevent things not missing the REGISTER event.

Hmm.  But we do call ipv6_add_dev on loopback and now the loopback
device is practically guaranteed to be the first device so we can
probably just remove the special case in addrconf_init.

Anyway Daniels patch makes increasingly less sense the more I look
at it.


> Namespaces are good to catch leakage using standard codepaths, so they
> should be preserved as much as possible. So, _all_ normal down code
> should be called for a loopback device in other than init_net context.

In any context. After the code path is aware of multiple network namespaces
init_net should not be special in any way.

I completely agree about the ability to catch weird leakage scenarios.

Eric
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