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

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Message-ID: <20100422154908.GA31568@midget.suse.cz>
Date:	Thu, 22 Apr 2010 17:49:08 +0200
From:	Jiri Bohac <jbohac@...e.cz>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	David Miller <davem@...emloft.net>, 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 10:25:06PM +0800, Herbert Xu wrote:
> This patch fixes this by using the DADFAILED bit to synchronise
> the two paths while holding the ifp lock.  It relies on the fact
> that the TENTATIVE bit is always set during DAD, and that the
> DADFAILED bit is only set on failure.

But the addr_dad_failure()->...->ipv6_del_addr() path will
still race with any other path calling ipv6_del_addr() (e.g. a
manual address removal). Won't it?

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)?

-- 
Jiri Bohac <jbohac@...e.cz>
SUSE Labs, SUSE CZ

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