netdev - Re: IPv6: race condition in __ipv6_ifa_notify() and dst

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Message-ID: <20100423021000.GA21777@gondor.apana.org.au>
Date:	Fri, 23 Apr 2010 10:10:00 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	David Miller <davem@...emloft.net>
Cc:	jbohac@...e.cz, yoshfuji@...ux-ipv6.org, netdev@...r.kernel.org,
	shemminger@...tta.com
Subject: Re: IPv6: race condition in __ipv6_ifa_notify() and dst_free() ?

On Thu, Apr 22, 2010 at 06:54:00PM -0700, David Miller wrote:
> From: Jiri Bohac <jbohac@...e.cz>
> Date: Thu, 22 Apr 2010 17:49:08 +0200
> 
> > I still don't see why __ipv6_ifa_notify() needs to call
> > dst_free(). Shouldn't that be dst_release() instead, to drop the
> > reference obtained by dst_hold(&ifp->rt->u.dst)?
> 
> It likely wants to do both.

Actually I don't think the problem is in __ipv6_ifa_notify.  The
fact is none of this stuff is meant to be idempotent.  So it's
up to the entity that is requesting the deletion to make sure that
a single object is not deleted more than once.

Yes the original symptom was in __ipv6_ifa_notify, but it is
merely pointing out that we have a problem further up.

My patch is indeed not sufficient as Jiri pointed out, because
I didn't deal with the case of an administrative deletion of
autmatically generated IPv6 addresses.

I will post an updated patch later today to deal with that.

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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