netdev - Re: [PATCHv3 net] xfrm: move xfrm_garbage_collect out of xfrm_policy

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Message-ID: <20170612121342.GY2631@secunet.com>
Date:   Mon, 12 Jun 2017 14:13:42 +0200
From:   Steffen Klassert <steffen.klassert@...unet.com>
To:     Hangbin Liu <liuhangbin@...il.com>
CC:     <netdev@...r.kernel.org>, David Miller <davem@...emloft.net>,
        Xin Long <lucien.xin@...il.com>
Subject: Re: [PATCHv3 net] xfrm: move xfrm_garbage_collect out of
 xfrm_policy_flush

On Sun, Jun 11, 2017 at 09:44:20AM +0800, Hangbin Liu wrote:
> Now we will force to do garbage collection if any policy removed in
> xfrm_policy_flush(). But during xfrm_net_exit(). We call flow_cache_fini()
> first and set set fc->percpu to NULL. Then after we call xfrm_policy_fini()
> -> frxm_policy_flush() -> flow_cache_flush(), we will get NULL pointer
> dereference when check percpu_empty. The code path looks like:
> 
> flow_cache_fini()
>   - fc->percpu = NULL
> xfrm_policy_fini()
>   - xfrm_policy_flush()
>     - xfrm_garbage_collect()
>       - flow_cache_flush()
>         - flow_cache_percpu_empty()
> 	  - fcp = per_cpu_ptr(fc->percpu, cpu)
> 
> To reproduce, just add ipsec in netns and then remove the netns.
> 
> v2:
> As Xin Long suggested, since only two other places need to call it. move
> xfrm_garbage_collect() outside xfrm_policy_flush().
> 
> v3:
> Fix subject mismatch after v2 fix.
> 
> Fixes: 35db06912189 ("xfrm: do the garbage collection after flushing policy")
> Signed-off-by: Hangbin Liu <liuhangbin@...il.com>

Patch applied, thanks eveyone!