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Subject: Re: BUG: unable to handle kernel NULL pointer dereference at
 00000000000000a0
From: Eric Dumazet <eric.dumazet@gmail.com>
To: "Justin P.Mattock" <justinmattock@gmail.com>
Cc: "John W.Linville" <linville@tuxdriver.com>, netdev@vger.kernel.org,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       davem@davemloft.net, timo.teras@iki.fi
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Date: Wed, 23 Jun 2010 19:29:27 +0200
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Le mercredi 23 juin 2010 à 10:00 -0700, Justin P. Mattock a écrit :
> o.k. the bisect is pointing to the below results..
> (I tried git revert xxx but this commit is too big
> so I'll(hopefully)manually revert it on the latest HEAD to
> see if this is the actual problem im experiencing)
> 
> 
> 
> 80c802f3073e84c956846e921e8a0b02dfa3755f is the first bad commit
> commit 80c802f3073e84c956846e921e8a0b02dfa3755f
> Author: Timo Teräs <timo.teras@iki.fi>
> Date:   Wed Apr 7 00:30:05 2010 +0000
> 
>      xfrm: cache bundles instead of policies for outgoing flows
> 
>      __xfrm_lookup() is called for each packet transmitted out of
>      system. The xfrm_find_bundle() does a linear search which can
>      kill system performance depending on how many bundles are
>      required per policy.
> 
>      This modifies __xfrm_lookup() to store bundles directly in
>      the flow cache. If we did not get a hit, we just create a new
>      bundle instead of doing slow search. This means that we can now
>      get multiple xfrm_dst's for same flow (on per-cpu basis).
> 
>      Signed-off-by: Timo Teras <timo.teras@iki.fi>
>      Signed-off-by: David S. Miller <davem@davemloft.net>
> 
> :040000 040000 d8e60f5fa4c1329f450d9c7cdf98b34e6a177f22 
> 9f576e68e5bf4ce357d7f0305aee5f410250dfe2 M      include
> :040000 040000 f2876df688ee36907af7b4123eea96592faaed3e 
> a3f6f6f94f0309106856cd99b38ec90b024eb016 M      net
> 
> 

Thanks a lot for bisecting Jutin, this is really appreciated.

crash is in xfrm_bundle_ok()

if (xdst->policy_genid != atomic_read(&xdst->pols[0]->genid))
	return 0;

xdst->pols[0] contains a NULL pointer