netdev - Re: [PATCH 5/5] xfrm: Fix unlink race when policies are deleted.

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Date:	Thu, 27 Feb 2014 14:30:15 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Steffen Klassert <steffen.klassert@...unet.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH 5/5] xfrm: Fix unlink race when policies are deleted.

On Thu, Feb 27, 2014 at 02:27:12PM +0800, Herbert Xu wrote:
> On Thu, Feb 27, 2014 at 07:16:39AM +0100, Steffen Klassert wrote:
> > When a policy is unlinked from the lists in thread context,
> > the xfrm timer can fire before we can mark this policy as dead.
> > So reinitialize the bydst hlist, then hlist_unhashed() will
> > notice that this policy is not linked and will avoid a
> > doulble unlink of that policy.
> > 
> > Reported-by: Xianpeng Zhao <673321875@...com>
> > Signed-off-by: Steffen Klassert <steffen.klassert@...unet.com>
> 
> If this race condition is real then I don't see how this fix
> can be correct since there aren't any barriers between the check
> and the unlink.

Looking at the code it seems that we've already taken the policy
lock so how can this race occur?

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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